id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1708.03929 | Mariusz Dabrowski P. | Mariusz P. Dabrowski | Singularities and Cyclic Universes | 4 pages, no figures | Acta Phys. Pol. (Proc. Suppl.) B10, 415 (2017) | 10.5506/APhysPolBSupp.10.415 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The models of cyclic universes and cyclic multiverses based on the
alternative gravity theories of varying constants are considered.
| [
{
"created": "Sun, 13 Aug 2017 16:37:53 GMT",
"version": "v1"
}
] | 2017-08-18 | [
[
"Dabrowski",
"Mariusz P.",
""
]
] | The models of cyclic universes and cyclic multiverses based on the alternative gravity theories of varying constants are considered. |
gr-qc/9705041 | Chung-I. Kuo | Chung-I Kuo(Soochow University) | Quantum Fluctuations of Scalar Field in Conical Space | 8 pages, RevTeX file, no figure, to appear in Phys. Lett. B | Phys.Lett. B405 (1997) 236-242 | 10.1016/S0370-2693(97)00594-7 | null | gr-qc | null | We consider vacuum polarization effect of a conformally coupled massless
scalar field in the background produced by an idealized straight cosmic string.
Using previous criterion we show the calculation of back reaction of the field
to the metric in the context of semiclassical gravity theory is not valid , in
some regions due to large quantum fluctuations in the conical space.
| [
{
"created": "Wed, 14 May 1997 15:25:32 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Kuo",
"Chung-I",
"",
"Soochow University"
]
] | We consider vacuum polarization effect of a conformally coupled massless scalar field in the background produced by an idealized straight cosmic string. Using previous criterion we show the calculation of back reaction of the field to the metric in the context of semiclassical gravity theory is not valid , in some regions due to large quantum fluctuations in the conical space. |
gr-qc/0301124 | Andrew Makarenko | A.N. Makarenko, V.V. Obukhov, K.E. Osetrin | Kantowski-Sachs Brane Cosmology | 3 pages, other comments | null | null | null | gr-qc | null | We consider brane Kantowski-Sachs Universe when bulk space is
five-dimensional Anti-deSitter space. The corresponding cosmological equations
with perfect fluid are written. For several specific choices of relation
between energy and pressure it is found the behavior of scale factors at early
time. In particulary, for $\gamma=3/2$ Kantowski-Sachs brane cosmology is
modified to become the isotropic one, while for $\gamma=1$ it remains the
anisotropic cosmology in the process of evolution.
| [
{
"created": "Fri, 31 Jan 2003 07:18:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Makarenko",
"A. N.",
""
],
[
"Obukhov",
"V. V.",
""
],
[
"Osetrin",
"K. E.",
""
]
] | We consider brane Kantowski-Sachs Universe when bulk space is five-dimensional Anti-deSitter space. The corresponding cosmological equations with perfect fluid are written. For several specific choices of relation between energy and pressure it is found the behavior of scale factors at early time. In particulary, for $\gamma=3/2$ Kantowski-Sachs brane cosmology is modified to become the isotropic one, while for $\gamma=1$ it remains the anisotropic cosmology in the process of evolution. |
1811.06927 | Daniel Hartley | Daniel Hartley and Christian K\"ading and Richard Howl and Ivette
Fuentes | Quantum simulation of dark energy candidates | 26 pages, 3 figures | Phys. Rev. D 99, 105002 (2019) | 10.1103/PhysRevD.99.105002 | null | gr-qc astro-ph.CO cond-mat.quant-gas quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Additional scalar fields from scalar-tensor, modified gravity or higher
dimensional theories beyond general relativity may account for dark energy and
the accelerating expansion of the Universe. These theories have lead to
proposed models of screening mechanisms, such as chameleon and symmetron
fields, to account for the tight experimental bounds on fifth-force searches.
Cold atom systems have been very successfully used to constrain the parameters
of these screening models, and may in future eliminate the interesting
parameter space of some models entirely. In this paper, we show how to
manipulate a Bose-Einstein condensate to simulate the effect of any screened
scalar field model coupled conformally to the metric. We give explicit
expressions for the simulation of various common models. This result may be
useful for investigating the computationally challenging evolution of particles
on a screened scalar field background, as well as for testing the metrology
scheme of an upcoming detector proposal.
| [
{
"created": "Fri, 16 Nov 2018 17:20:57 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2019 12:20:33 GMT",
"version": "v2"
}
] | 2019-05-14 | [
[
"Hartley",
"Daniel",
""
],
[
"Käding",
"Christian",
""
],
[
"Howl",
"Richard",
""
],
[
"Fuentes",
"Ivette",
""
]
] | Additional scalar fields from scalar-tensor, modified gravity or higher dimensional theories beyond general relativity may account for dark energy and the accelerating expansion of the Universe. These theories have lead to proposed models of screening mechanisms, such as chameleon and symmetron fields, to account for the tight experimental bounds on fifth-force searches. Cold atom systems have been very successfully used to constrain the parameters of these screening models, and may in future eliminate the interesting parameter space of some models entirely. In this paper, we show how to manipulate a Bose-Einstein condensate to simulate the effect of any screened scalar field model coupled conformally to the metric. We give explicit expressions for the simulation of various common models. This result may be useful for investigating the computationally challenging evolution of particles on a screened scalar field background, as well as for testing the metrology scheme of an upcoming detector proposal. |
1711.02723 | Stelios Karydas Mr | B. C. Georgalas, Stelios Karydas, Eleftherios Papantonopoulos | Reconstruction of Cosmological Evolution in the Presence of Extra
Dimensions | 15 pages, 11 figures, version accepted for publication in JCAP,
includes a number of minor clarifications throughout, and a lengthier
discussion of needed/used constraints in Section 4 | null | 10.1088/1475-7516/2018/08/005 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The model of Physics resulting from a Kaluza-Klein dimensional reduction
procedure offers very good dark matter candidates in the form of Light
Kaluza-Klein Particles, and thus becomes relevant to Cosmology. In this work we
recover a late-time cosmological picture, similar to that of the $\Lambda$CDM,
in a multidimensional scenario, in the general framework of Universal Extra
Dimensions. This is achieved by utilizing a special, Kasner-type solution that
is analytically known, and acts as an attractor for a plethora of pairs of
initial conditions of the usual and extra spatial Hubble parameters. The
phenomenology of fundamental interactions dictates the stabilization of the
extra dimensional evolution from a very early epoch in these scenarios. Without
an explicit mechanism, this is achieved through particular behaviors of the
usual and extra spatial fluids, which have to be motivated by a more
fundamental theory.
| [
{
"created": "Tue, 7 Nov 2017 20:53:56 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Nov 2017 08:58:44 GMT",
"version": "v2"
},
{
"created": "Sat, 24 Mar 2018 11:13:26 GMT",
"version": "v3"
},
{
"created": "Mon, 30 Jul 2018 09:09:27 GMT",
"version": "v4"
}
] | 2018-08-15 | [
[
"Georgalas",
"B. C.",
""
],
[
"Karydas",
"Stelios",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | The model of Physics resulting from a Kaluza-Klein dimensional reduction procedure offers very good dark matter candidates in the form of Light Kaluza-Klein Particles, and thus becomes relevant to Cosmology. In this work we recover a late-time cosmological picture, similar to that of the $\Lambda$CDM, in a multidimensional scenario, in the general framework of Universal Extra Dimensions. This is achieved by utilizing a special, Kasner-type solution that is analytically known, and acts as an attractor for a plethora of pairs of initial conditions of the usual and extra spatial Hubble parameters. The phenomenology of fundamental interactions dictates the stabilization of the extra dimensional evolution from a very early epoch in these scenarios. Without an explicit mechanism, this is achieved through particular behaviors of the usual and extra spatial fluids, which have to be motivated by a more fundamental theory. |
1206.1420 | Subenoy Chakraborty | Subenoy Chakraborty | Is thermodynamics of the universe bounded by the event horizon a
Bekenstein system? | 4 pages; accepted for publication in Phys. Lett. B | null | 10.1016/j.physletb.2012.11.021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this brief communication, we have studied the validity of the first law of
thermodynamics for the universe bounded by event horizon with two examples. The
key point is the appropriate choice of the temperature on the event horizon.
Finally, we have concluded that universe bounded by the event horizon may be a
Bekenstein system and the Einstein's equations and the first law of
thermodynamics on the event horizons are equivalent.
| [
{
"created": "Thu, 7 Jun 2012 08:07:27 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Nov 2012 08:08:02 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Chakraborty",
"Subenoy",
""
]
] | In this brief communication, we have studied the validity of the first law of thermodynamics for the universe bounded by event horizon with two examples. The key point is the appropriate choice of the temperature on the event horizon. Finally, we have concluded that universe bounded by the event horizon may be a Bekenstein system and the Einstein's equations and the first law of thermodynamics on the event horizons are equivalent. |
gr-qc/0508070 | Domenico Giulini | Domenico Giulini and Gustav Holzegel | Corvino's construction using Brill waves | 14 pages, 2 figures | null | null | Freiburg THEP 05/09 | gr-qc | null | For two-black-hole time-symmetric initial data we consider the Corvino
construction of gluing an exact Schwarzschild end. We propose to do this by
using Brill waves. We address the question of whether this method can be used
to reduce the overall energy, which seems to relate to the question of whether
it can reduce the amount of `spurious' gravitational radiation. We find a
positive answer at first order in the inverse gluing radius.
| [
{
"created": "Wed, 17 Aug 2005 13:57:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Giulini",
"Domenico",
""
],
[
"Holzegel",
"Gustav",
""
]
] | For two-black-hole time-symmetric initial data we consider the Corvino construction of gluing an exact Schwarzschild end. We propose to do this by using Brill waves. We address the question of whether this method can be used to reduce the overall energy, which seems to relate to the question of whether it can reduce the amount of `spurious' gravitational radiation. We find a positive answer at first order in the inverse gluing radius. |
gr-qc/0103031 | Hisaaki Shinkai | Hisa-aki Shinkai and Gen Yoneda | Will hyperbolic formulations help numerical relativity? - Experiments
using Ashtekar's connection variables | 9 pages, LaTeX, 4 eps figures, for the proceedings of 10th JGRG,
Osaka, Japan, Sept. 11 - 14, 2000 | null | null | CGPG-00/11-3 | gr-qc | null | In order to perform accurate and stable long-term numerical integration of
the Einstein equations, several hyperbolic systems have been proposed. We here
report our numerical comparisons between weakly hyperbolic, strongly
hyperbolic, and symmetric hyperbolic systems based on Ashtekar's connection
variables. The primary advantage for using this connection formulation is that
we can keep using the same dynamical variables for all levels of hyperbolicity.
We also study asymptotically constrained systems, "$\lambda$-system" and
"adjusted system", for numerical integration of the Einstein equations, which
are intended to be robust against perturbative errors for the free evolution of
the initial data. These systems are tested in the Maxwell system and in the
Ashtekar's system. This mechanism affects more than the system's symmetric
hyperbolicity.
(This workshop contribution is the summary of our gr-qc/0005003 [CQG 17
(2000) 4799] and gr-qc/0007034 [CQG 18 (2001) 441].)
| [
{
"created": "Fri, 9 Mar 2001 19:58:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shinkai",
"Hisa-aki",
""
],
[
"Yoneda",
"Gen",
""
]
] | In order to perform accurate and stable long-term numerical integration of the Einstein equations, several hyperbolic systems have been proposed. We here report our numerical comparisons between weakly hyperbolic, strongly hyperbolic, and symmetric hyperbolic systems based on Ashtekar's connection variables. The primary advantage for using this connection formulation is that we can keep using the same dynamical variables for all levels of hyperbolicity. We also study asymptotically constrained systems, "$\lambda$-system" and "adjusted system", for numerical integration of the Einstein equations, which are intended to be robust against perturbative errors for the free evolution of the initial data. These systems are tested in the Maxwell system and in the Ashtekar's system. This mechanism affects more than the system's symmetric hyperbolicity. (This workshop contribution is the summary of our gr-qc/0005003 [CQG 17 (2000) 4799] and gr-qc/0007034 [CQG 18 (2001) 441].) |
gr-qc/0106003 | David Waite | David Waite | Inertia Manipulation through Metric Patching | 6 pages | null | null | null | gr-qc | null | This paper will present the exact solution for the stress-energy tensor of a
spherical matter shell of finite thickness that will patch together different
metrics at the boundaries of the shell. The choice of vacuum field solutions
for the shell exterior and hollow interior that we make will allow us to
manipulate the inertial state of an object within the shell. The choice will
cause it to be in a state of acceleration with the shell relative to an
external observer for an indefinite time. The stress-energy tensor's solution
results in zero ship frame energy requirements, and only finite stress
requirements, and we show how any WEC violation can be avoided.
| [
{
"created": "Sat, 2 Jun 2001 10:26:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Waite",
"David",
""
]
] | This paper will present the exact solution for the stress-energy tensor of a spherical matter shell of finite thickness that will patch together different metrics at the boundaries of the shell. The choice of vacuum field solutions for the shell exterior and hollow interior that we make will allow us to manipulate the inertial state of an object within the shell. The choice will cause it to be in a state of acceleration with the shell relative to an external observer for an indefinite time. The stress-energy tensor's solution results in zero ship frame energy requirements, and only finite stress requirements, and we show how any WEC violation can be avoided. |
2306.06168 | Jonathan Nay | Jonathan Nay, Kimberly K. Boddy, Tristan L. Smith, Chiara M. F.
Mingarelli | Harmonic Analysis for Pulsar Timing Arrays | 17 pages, 11 figures | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the use of harmonic analysis techniques to perform
measurements of the angular power spectrum on mock pulsar timing data for an
isotropic stochastic gravitational-wave background (SGWB) with a dimensionless
strain amplitude $A_{\text{gw}}=2 \times 10^{-15}$ and spectral index
$\gamma_{\text{gw}}=13/3$. We examine the sensitivity of our harmonic analysis
to the number of pulsars (50, 100, and 150) and length of pulsar observation
time (10, 20, and 30 years) for an isotropic distribution of pulsars. We
account for intrinsic pulsar red noise and use an average value of white noise
of ~100 ns. We are able to detect the quadrupole for all our mock harmonic
analyses, and for the analysis with 150 pulsars observed for 30 years, we are
able to detect up to the $\ell = 5$ multipole. We provide scaling laws for the
SGWB amplitude, the quadrupole, and $\ell = 3$ as a function of pulsar
observation time and as a function of number of pulsars. We estimate the
sensitivity of our harmonic approach to deviations of General Relativity that
produce subluminal gravitational wave propagation speeds.
| [
{
"created": "Fri, 9 Jun 2023 18:00:02 GMT",
"version": "v1"
}
] | 2023-06-13 | [
[
"Nay",
"Jonathan",
""
],
[
"Boddy",
"Kimberly K.",
""
],
[
"Smith",
"Tristan L.",
""
],
[
"Mingarelli",
"Chiara M. F.",
""
]
] | We investigate the use of harmonic analysis techniques to perform measurements of the angular power spectrum on mock pulsar timing data for an isotropic stochastic gravitational-wave background (SGWB) with a dimensionless strain amplitude $A_{\text{gw}}=2 \times 10^{-15}$ and spectral index $\gamma_{\text{gw}}=13/3$. We examine the sensitivity of our harmonic analysis to the number of pulsars (50, 100, and 150) and length of pulsar observation time (10, 20, and 30 years) for an isotropic distribution of pulsars. We account for intrinsic pulsar red noise and use an average value of white noise of ~100 ns. We are able to detect the quadrupole for all our mock harmonic analyses, and for the analysis with 150 pulsars observed for 30 years, we are able to detect up to the $\ell = 5$ multipole. We provide scaling laws for the SGWB amplitude, the quadrupole, and $\ell = 3$ as a function of pulsar observation time and as a function of number of pulsars. We estimate the sensitivity of our harmonic approach to deviations of General Relativity that produce subluminal gravitational wave propagation speeds. |
gr-qc/0106046 | Manoelito M. de Souza | Manoelito M. de Souza | Discrete fields and the Pioneer anomalous acceleration | 8 pages | null | null | null | gr-qc astro-ph hep-th | null | The dominant contributions from a discrete gravitational interaction produce
the standard potential as an effective continuous field. The sub-dominant
contributions are, in a first approximation, linear on n, the accumulated
number of (discrete) interaction events along the test-body trajectory. For a
nearly radial trajectory n is proportional to the traversed distance and its
effects may have been observed as the Pioneer anomalous constant radial
acceleration, which cannot be observed on the nearly circular planetary orbits.
| [
{
"created": "Thu, 14 Jun 2001 14:57:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Souza",
"Manoelito M.",
""
]
] | The dominant contributions from a discrete gravitational interaction produce the standard potential as an effective continuous field. The sub-dominant contributions are, in a first approximation, linear on n, the accumulated number of (discrete) interaction events along the test-body trajectory. For a nearly radial trajectory n is proportional to the traversed distance and its effects may have been observed as the Pioneer anomalous constant radial acceleration, which cannot be observed on the nearly circular planetary orbits. |
gr-qc/0201014 | Angelo Tartaglia | A. Tartaglia | Space time and rotations | RevTex, 15 pages | null | null | null | gr-qc | null | The paper considers the problem of finding the metric of space time around a
rotating, weakly gravitating body. Both external and internal metric tensors
are consistently found, together with an appropriate source tensor. All tensors
are calculated at the lowest meaningful approximation in a power series. The
two physical parameters entering the equations (the mass and the angular
momentum per unit mass) are assumed to be such that the mass effects are
negligible with respect to the rotation effects. A non zero Riemann tensor is
obtained. The order of magnitude of the effects at the laboratory scale is such
as to allow for experimental verification of the theory.
| [
{
"created": "Fri, 4 Jan 2002 13:18:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tartaglia",
"A.",
""
]
] | The paper considers the problem of finding the metric of space time around a rotating, weakly gravitating body. Both external and internal metric tensors are consistently found, together with an appropriate source tensor. All tensors are calculated at the lowest meaningful approximation in a power series. The two physical parameters entering the equations (the mass and the angular momentum per unit mass) are assumed to be such that the mass effects are negligible with respect to the rotation effects. A non zero Riemann tensor is obtained. The order of magnitude of the effects at the laboratory scale is such as to allow for experimental verification of the theory. |
gr-qc/0505161 | Fu-Wen Shu | Fu-Wen Shu, You-Gen Shen | Quasinormal modes of Rarita-Schwinger field in Reissner-Nordstr\"{o}m
black hole spacetimes | 9 pages, 2 figures | Phys.Lett.B614:195-200,2005 | 10.1016/j.physletb.2005.03.076 | null | gr-qc | null | The Newman-Penrose formalism is used to deal with the quasinormal
modes(QNM's) of Rarita-Schwinger perturbations outside a Reissner-Nordstr\"{o}m
black hole. We obtain four kinds of possible expressions of effective
potentials, which are proved to be of the same spectra of quasinormal mode
frequencies. The quasinormal mode frequencies evaluated by the WKB potential
approximation show that, similar to those for Dirac perturbations, the real
parts of the frequencies increase with the charge $Q$ and decrease with the
mode number $n$, while the dampings almost keep unchanged as the charge
increases.
| [
{
"created": "Tue, 31 May 2005 15:22:41 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Shu",
"Fu-Wen",
""
],
[
"Shen",
"You-Gen",
""
]
] | The Newman-Penrose formalism is used to deal with the quasinormal modes(QNM's) of Rarita-Schwinger perturbations outside a Reissner-Nordstr\"{o}m black hole. We obtain four kinds of possible expressions of effective potentials, which are proved to be of the same spectra of quasinormal mode frequencies. The quasinormal mode frequencies evaluated by the WKB potential approximation show that, similar to those for Dirac perturbations, the real parts of the frequencies increase with the charge $Q$ and decrease with the mode number $n$, while the dampings almost keep unchanged as the charge increases. |
2107.05723 | Valerio Bozza | F. Aratore, V. Bozza | Decoding a black hole metric from the interferometric pattern of the
relativistic images of a compact source | 20 pages, 8 figures | null | 10.1088/1475-7516/2021/10/054 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Photons emitted by light sources in the neighbourhood of a black hole can
wind several times around it before fleeing towards the observer. For
spherically symmetric black holes, two infinite sequences of images are created
for any given source, asymptotically approaching the shadow border with
decreasing magnitude. These sequences are reflected by a characteristic
staircase structure in the complex visibility function that may be used to
decode the properties of the black hole metric. Recalling the formalism of
gravitational lensing in the strong deflection limit, we derive analytical
formulae for the height, the width and the periodicities of the steps in the
visibility as functions of the black hole parameters for the case of a single
compact and distant source. With respect to diffuse emission by the whole
accretion flow, this ideal framework provides clean insight and
model-independent information on the metric. These basic formulae can then be
used to build visibilities for more complicated sources and track the changes
induced by alternative metrics and ultimately test General Relativity. As
simple examples, we include visibilities for Reissner-Nordstr\"om and
Janis-Newman-Winicour metrics.
| [
{
"created": "Mon, 12 Jul 2021 20:29:17 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 2021 07:16:10 GMT",
"version": "v2"
}
] | 2021-10-27 | [
[
"Aratore",
"F.",
""
],
[
"Bozza",
"V.",
""
]
] | Photons emitted by light sources in the neighbourhood of a black hole can wind several times around it before fleeing towards the observer. For spherically symmetric black holes, two infinite sequences of images are created for any given source, asymptotically approaching the shadow border with decreasing magnitude. These sequences are reflected by a characteristic staircase structure in the complex visibility function that may be used to decode the properties of the black hole metric. Recalling the formalism of gravitational lensing in the strong deflection limit, we derive analytical formulae for the height, the width and the periodicities of the steps in the visibility as functions of the black hole parameters for the case of a single compact and distant source. With respect to diffuse emission by the whole accretion flow, this ideal framework provides clean insight and model-independent information on the metric. These basic formulae can then be used to build visibilities for more complicated sources and track the changes induced by alternative metrics and ultimately test General Relativity. As simple examples, we include visibilities for Reissner-Nordstr\"om and Janis-Newman-Winicour metrics. |
gr-qc/0205035 | Ilja Schmelzer | I. Schmelzer | A generalization of the Lorentz ether to gravity with
general-relativistic limit | Some changes in the presentation | Advances in Applied Clifford Algebras 22, 1 (2012), p. 203-242 | 10.1007/s00006-011-0303-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Does relativistic gravity provide arguments against the existence of a
preferred frame? Our answer is negative. We define a viable theory of gravity
with preferred frame. In this theory, the EEP holds exactly, and the Einstein
equations of GR limit are obtained in a natural limit. Despite some remarkable
differences (stable "frozen stars" instead of black holes, a "big bounce"
instead of the big bang, exclusion of nontrivial topologies and closed causal
loops, and a preference for a flat universe) the theory is viable.
The equations of the theory are derived from simple axioms about some
fundamental condensed matter (the generalized Lorentz ether), so that, in
particular, the EEP is not postulated but derived.
The theory is compatible with the condensed matter interpretation for the
fermions and gauge fields of the standard model.
| [
{
"created": "Wed, 8 May 2002 21:24:54 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Nov 2002 16:52:18 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Feb 2011 15:25:59 GMT",
"version": "v3"
},
{
"created": "Sat, 20 Oct 2012 17:35:09 GMT",
"version": "v4"
}
] | 2012-10-23 | [
[
"Schmelzer",
"I.",
""
]
] | Does relativistic gravity provide arguments against the existence of a preferred frame? Our answer is negative. We define a viable theory of gravity with preferred frame. In this theory, the EEP holds exactly, and the Einstein equations of GR limit are obtained in a natural limit. Despite some remarkable differences (stable "frozen stars" instead of black holes, a "big bounce" instead of the big bang, exclusion of nontrivial topologies and closed causal loops, and a preference for a flat universe) the theory is viable. The equations of the theory are derived from simple axioms about some fundamental condensed matter (the generalized Lorentz ether), so that, in particular, the EEP is not postulated but derived. The theory is compatible with the condensed matter interpretation for the fermions and gauge fields of the standard model. |
1810.05527 | Abdul Jawad | Abdul Jawad, Shamaila Rani and Salman Rafique | Thermodynamics of Various Entropies in Specific Modified Gravity with
Particle Creation | 32 pages, 12 figures, AHEP accepted. arXiv admin note: text overlap
with arXiv:1801.09999; text overlap with arXiv:1604.00899, arXiv:0811.4477 by
other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the particle creation scenario in the dynamical Chern-Simons
modified gravity in the presence of perfect fluid equation of state
$p=(\gamma-1)\rho$. By assuming various modified entropies (Bekenstein,
logarithmic, power law correction and Reyni), we investigate the first law of
thermodynamics and generalized second law of thermodynamics on the apparent
horizon. In the presence of particle creation rate, we discuss the generalized
second law of thermodynamics and thermal equilibrium condition. It is found
that thermodynamic laws and equilibrium condition remain valid under certain
conditions of parameters.
| [
{
"created": "Wed, 10 Oct 2018 06:33:10 GMT",
"version": "v1"
}
] | 2018-10-15 | [
[
"Jawad",
"Abdul",
""
],
[
"Rani",
"Shamaila",
""
],
[
"Rafique",
"Salman",
""
]
] | We consider the particle creation scenario in the dynamical Chern-Simons modified gravity in the presence of perfect fluid equation of state $p=(\gamma-1)\rho$. By assuming various modified entropies (Bekenstein, logarithmic, power law correction and Reyni), we investigate the first law of thermodynamics and generalized second law of thermodynamics on the apparent horizon. In the presence of particle creation rate, we discuss the generalized second law of thermodynamics and thermal equilibrium condition. It is found that thermodynamic laws and equilibrium condition remain valid under certain conditions of parameters. |
1603.01461 | Naser Sadeghnezhad | N. Sadeghnezhad | A Note on Coherent States with Quantum Gravity Effects | 14 pages, 2 figures | null | 10.1016/j.cjph.2016.06.009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Existence of a minimal measurable length and an upper bound for the momentum
fluctuations are the casting reasons for generalization of uncertainty
principle and then reformulation of Hilbert space representation of quantum
mechanics. In this paper, we study the consequences of the Generalized
Uncertainty Principle (GUP) in the presence of both minimal length and maximal
momentum. We consider a simple harmonic oscillator in the framework of GUP by
introducing it's energy eigenstates and energy spectrum. Investigation of
coherent states for a generalized harmonic oscillator and it's generic behavior
are the other topics in our study.
| [
{
"created": "Fri, 26 Feb 2016 22:46:37 GMT",
"version": "v1"
}
] | 2016-11-29 | [
[
"Sadeghnezhad",
"N.",
""
]
] | Existence of a minimal measurable length and an upper bound for the momentum fluctuations are the casting reasons for generalization of uncertainty principle and then reformulation of Hilbert space representation of quantum mechanics. In this paper, we study the consequences of the Generalized Uncertainty Principle (GUP) in the presence of both minimal length and maximal momentum. We consider a simple harmonic oscillator in the framework of GUP by introducing it's energy eigenstates and energy spectrum. Investigation of coherent states for a generalized harmonic oscillator and it's generic behavior are the other topics in our study. |
1106.5066 | Eugen Radu | Eugen Radu, Ya. Shnir and D. H. Tchrakian | Scalar hairy black holes and solitons in a gravitating Goldstone model | 17 pages, 5 figures | Phys.Lett.B703:386-393,2011 | 10.1016/j.physletb.2011.08.032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study black hole solutions of Einstein gravity coupled to a specific
global symmetry breaking Goldstone model described by an O(3) isovector scalar
field in four spacetime dimensions. Our configurations are static and
spherically symmetric, approaching at infinity a Minkowski spacetime
background. A set of globally regular, particle-like solutions are found in the
limit of vanishing event horizon radius. These configurations can be viewed as
'regularised' global monopoles, since their mass is finite and the spacetime
geometry has no deficit angle. As an unusual feature, we notice the existence
of extremal black holes in this model defined in terms of gravity and scalar
fields only.
| [
{
"created": "Fri, 24 Jun 2011 20:47:38 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jul 2011 12:08:37 GMT",
"version": "v2"
}
] | 2011-09-07 | [
[
"Radu",
"Eugen",
""
],
[
"Shnir",
"Ya.",
""
],
[
"Tchrakian",
"D. H.",
""
]
] | We study black hole solutions of Einstein gravity coupled to a specific global symmetry breaking Goldstone model described by an O(3) isovector scalar field in four spacetime dimensions. Our configurations are static and spherically symmetric, approaching at infinity a Minkowski spacetime background. A set of globally regular, particle-like solutions are found in the limit of vanishing event horizon radius. These configurations can be viewed as 'regularised' global monopoles, since their mass is finite and the spacetime geometry has no deficit angle. As an unusual feature, we notice the existence of extremal black holes in this model defined in terms of gravity and scalar fields only. |
0906.3088 | Michael Gabler | Michael Gabler, Ulrich Sperhake and Nils Andersson | Nonlinear radial oscillations of neutron stars | 15 pages, 10 figures, 9 tables; To match published version in
Phys.Rev.D; discussion about interpretation of the expression "mode coupling"
and one figure added | Phys.Rev.D80:064012,2009 | 10.1103/PhysRevD.80.064012 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effects of nonlinear oscillations in compact stars are attracting
considerable current interest. In order to study such phenomena in the
framework of fully nonlinear general relativity, highly accurate numerical
studies are required. We present a numerical scheme specifically tailored for
studies, based on formulating the time evolution in terms of deviations from a
stationary equilibrium configuration. Using this technique, we investigate
nonlinear effects associated with radial oscillations of neutron stars for a
wide range of amplitudes. In particular, we discuss mode coupling due to
nonlinear interactions, the occurrence of resonance phenomena, shock formation
near the stellar surface as well as the capacity of nonlinearities to stabilize
perturbatively unstable neutron star models.
| [
{
"created": "Wed, 17 Jun 2009 08:48:14 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Sep 2009 06:12:12 GMT",
"version": "v2"
}
] | 2009-09-24 | [
[
"Gabler",
"Michael",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Andersson",
"Nils",
""
]
] | The effects of nonlinear oscillations in compact stars are attracting considerable current interest. In order to study such phenomena in the framework of fully nonlinear general relativity, highly accurate numerical studies are required. We present a numerical scheme specifically tailored for studies, based on formulating the time evolution in terms of deviations from a stationary equilibrium configuration. Using this technique, we investigate nonlinear effects associated with radial oscillations of neutron stars for a wide range of amplitudes. In particular, we discuss mode coupling due to nonlinear interactions, the occurrence of resonance phenomena, shock formation near the stellar surface as well as the capacity of nonlinearities to stabilize perturbatively unstable neutron star models. |
2405.08563 | Soma Heydari | Soma Heydari and Kayoomars Karami | Primordial black holes generated by fast-roll mechanism in non-canonical
natural inflation | 29 pages, 6 figures, 5 tables | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this work, a new fast-roll (FR) mechanism to generate primordial black
holes (PBHs) and their coeval gravitational waves (GWs) in generalized
non-canonical natural inflation is introduced. In this model, choosing a
suitable function for non-canonical mass scale parameter $M(\phi)$ gives rise
to produce a cliff-like region in field evolution path. When inflaton rolls
down the steep cliff, its kinetic energy during the FR stage is amplified in
comparison with slow-roll (SR) stage. Hence, seeds of PBHs production are born
in this transient FR stage. Depending on the position of the cliff, appropriate
cases of PBHs for explaining total dark matter (DM), microlensing effects,
LIGO-VIRGO events and NANOGrav 15 year data can be formed. The density spectrum
of GWs related to one case of the model lies in the NANOGrav 15 year domain and
behaves like $\Omega_{\rm GW_0}\sim f^{5-\gamma}$. The spectral index
$\gamma=3.42$ for this case satisfies the NANOGrav 15 year constraint.
Moreover, regarding reheating considerations, it is demonstrated that PBHs are
born in radiation-dominated (RD) era. Furthermore, viability of the model in
light of theoretical swampland criteria and observational constraints on cosmic
microwave background (CMB) scales are illustrated.
| [
{
"created": "Tue, 14 May 2024 12:51:40 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Heydari",
"Soma",
""
],
[
"Karami",
"Kayoomars",
""
]
] | In this work, a new fast-roll (FR) mechanism to generate primordial black holes (PBHs) and their coeval gravitational waves (GWs) in generalized non-canonical natural inflation is introduced. In this model, choosing a suitable function for non-canonical mass scale parameter $M(\phi)$ gives rise to produce a cliff-like region in field evolution path. When inflaton rolls down the steep cliff, its kinetic energy during the FR stage is amplified in comparison with slow-roll (SR) stage. Hence, seeds of PBHs production are born in this transient FR stage. Depending on the position of the cliff, appropriate cases of PBHs for explaining total dark matter (DM), microlensing effects, LIGO-VIRGO events and NANOGrav 15 year data can be formed. The density spectrum of GWs related to one case of the model lies in the NANOGrav 15 year domain and behaves like $\Omega_{\rm GW_0}\sim f^{5-\gamma}$. The spectral index $\gamma=3.42$ for this case satisfies the NANOGrav 15 year constraint. Moreover, regarding reheating considerations, it is demonstrated that PBHs are born in radiation-dominated (RD) era. Furthermore, viability of the model in light of theoretical swampland criteria and observational constraints on cosmic microwave background (CMB) scales are illustrated. |
0803.0786 | S. K. Sahay | S.K. Sahay | On the independent points in the sky for the search of periodic
gravitational wave | 10 Pages, 2 figures | Rom.Rep.Phys.61:191-201,2009 | null | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the independent points in the sky require to search the
periodic gravitational wave, assuming the noise power spectral density to be
flat. We have made an analysis with different initial azimuth of the Earth for
a week data set. The analysis shows significant difference in the independent
points in the sky for the search. We numerically obtain an approximate relation
to make trade-off between computational cost and sensitivities. We also discuss
the feasibility of the coherent search in small frequency band in reference to
advanced LIGO.
| [
{
"created": "Thu, 6 Mar 2008 04:15:09 GMT",
"version": "v1"
}
] | 2010-02-05 | [
[
"Sahay",
"S. K.",
""
]
] | We investigate the independent points in the sky require to search the periodic gravitational wave, assuming the noise power spectral density to be flat. We have made an analysis with different initial azimuth of the Earth for a week data set. The analysis shows significant difference in the independent points in the sky for the search. We numerically obtain an approximate relation to make trade-off between computational cost and sensitivities. We also discuss the feasibility of the coherent search in small frequency band in reference to advanced LIGO. |
1807.06105 | David Garfinkle | David Garfinkle | Matters of Gravity, The Newsletter of the Division of Gravitational
Physics of the American Physical Society, Volume 51, June 2018 | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | DGRAV News:
We hear that....
DGRAV Student Travel Grants
Town Hall Meeting
GRG Society
Research Briefs:
What's new in LIGO
Conference Reports:
Christodoulou Conference
Obituaries:
Stephen Hawking (1942-2018)
Joseph Polchinski (1954-2018)
| [
{
"created": "Mon, 16 Jul 2018 20:54:51 GMT",
"version": "v1"
}
] | 2018-07-18 | [
[
"Garfinkle",
"David",
""
]
] | DGRAV News: We hear that.... DGRAV Student Travel Grants Town Hall Meeting GRG Society Research Briefs: What's new in LIGO Conference Reports: Christodoulou Conference Obituaries: Stephen Hawking (1942-2018) Joseph Polchinski (1954-2018) |
0808.3120 | L. C. Garcia de Andrade | Garcia de Andrade | Acoustic black hole evaporation as plasma diffusion phenomena | Dept fisica teorica-UERJ-Brasil | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Acoustic analogues of Kerr black hole in plasmas are considered, by taking
for granted the existence of acoustic ion waves in plasmas. An effective black
holes (BH) in curved Riemannian spacetime in a random walk plasmas is endowed
with a naked singularity, when plasmas are in the lowest diffusion mode. The
plasma particle diffusion is encoded in the effective metric. The diffusive
solution has a horizon when the plasma flow reaches the sound velocity in the
medium and a shock wave is obtained inside the slab. The sonic black hole
curved Riemannian metric is also found in terms of particle number density in
plasmas. The sonic BH singularity is found at the center of the plasma
diffusive slab from the study of the Ricci curvature scalar for constant
diffusion coefficient. It is suggested and shown that the Hawking temperature
is proportional to the plasma Kelvin temperature through diffusion coefficient
dependence to this temperature. Therefore Unruh sonic or dumb BH is shown to
have a relation between Hawking and plasma diffusive temperatures. BH
evaporation is analogous to the diffusive phenomena in plasmas, since in both
cases Hawking temperature is inversely proportional to mass. It is shown that
Hawking analogue temperature of a plasma torus is
$T_{H}(torus)\approx{10^{-4}K}$ which is much higher than the gravitational
Hawking temperature of a one solar mass BH, ${T_{H}}^{GR}\approx{10^{-8}K}$,
but still very small for being detectable in plasma laboratories.
| [
{
"created": "Fri, 22 Aug 2008 18:23:25 GMT",
"version": "v1"
}
] | 2008-08-25 | [
[
"de Andrade",
"Garcia",
""
]
] | Acoustic analogues of Kerr black hole in plasmas are considered, by taking for granted the existence of acoustic ion waves in plasmas. An effective black holes (BH) in curved Riemannian spacetime in a random walk plasmas is endowed with a naked singularity, when plasmas are in the lowest diffusion mode. The plasma particle diffusion is encoded in the effective metric. The diffusive solution has a horizon when the plasma flow reaches the sound velocity in the medium and a shock wave is obtained inside the slab. The sonic black hole curved Riemannian metric is also found in terms of particle number density in plasmas. The sonic BH singularity is found at the center of the plasma diffusive slab from the study of the Ricci curvature scalar for constant diffusion coefficient. It is suggested and shown that the Hawking temperature is proportional to the plasma Kelvin temperature through diffusion coefficient dependence to this temperature. Therefore Unruh sonic or dumb BH is shown to have a relation between Hawking and plasma diffusive temperatures. BH evaporation is analogous to the diffusive phenomena in plasmas, since in both cases Hawking temperature is inversely proportional to mass. It is shown that Hawking analogue temperature of a plasma torus is $T_{H}(torus)\approx{10^{-4}K}$ which is much higher than the gravitational Hawking temperature of a one solar mass BH, ${T_{H}}^{GR}\approx{10^{-8}K}$, but still very small for being detectable in plasma laboratories. |
gr-qc/0004003 | Shahar Hod | Shahar Hod | Evidence for a null entropy of extremal black holes | 11 pages | Phys.Rev. D61 (2000) 084018 | 10.1103/PhysRevD.61.084018 | null | gr-qc hep-th | null | We present some arguments in support of a {\it zero} entropy for {\it
extremal} black holes. These rely on a combination of both quantum,
thermodynamic, and statistical physics arguments. This result may shed some
light on the nature of these extreme objects. In addition, we show that within
a {\it quantum} framework the capture of a particle by an initially extremal
black hole always results with a final nonextremal black hole.
| [
{
"created": "Sat, 1 Apr 2000 06:38:19 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Apr 2000 10:15:34 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Hod",
"Shahar",
""
]
] | We present some arguments in support of a {\it zero} entropy for {\it extremal} black holes. These rely on a combination of both quantum, thermodynamic, and statistical physics arguments. This result may shed some light on the nature of these extreme objects. In addition, we show that within a {\it quantum} framework the capture of a particle by an initially extremal black hole always results with a final nonextremal black hole. |
0705.1346 | Alexey Toporensky | A. Toporensky, P. Tretyakov | Power-law anisotropic cosmological solution in 5+1 dimensional
Gauss-Bonnet gravity | 10 pages, one statement corrected, references added | Grav.Cosmol.13:207-210,2007 | null | null | gr-qc | null | We write down an anisotropic solution for a flat 5+1 dimensional Universe in
Gauss-Bonnet gravity. In the model under investigation this solution replaces
the generalized Kasner solution near a cosmological singularity.
| [
{
"created": "Wed, 9 May 2007 19:21:52 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2007 19:34:23 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Aug 2007 17:39:08 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Toporensky",
"A.",
""
],
[
"Tretyakov",
"P.",
""
]
] | We write down an anisotropic solution for a flat 5+1 dimensional Universe in Gauss-Bonnet gravity. In the model under investigation this solution replaces the generalized Kasner solution near a cosmological singularity. |
1507.06123 | Ivan de Martino | Ivan de Martino, Mariafelicia De Laurentis, Salvatore Capozziello | Constraining $f(R)$ gravity by the Large Scale Structure | 37 pages, 3 Tables, 6 Figures. Invited Review belonging "Special
Issue Modified Gravity Cosmology: From Inflation to Dark Energy". The
manuscript matches the accepted version. References updated | Universe 2015, 1(2), 123-157 | 10.3390/universe1020123 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Over the past decades, General Relativity and the concordance $\Lambda$CDM
model have been successfully tested using several different astrophysical and
cosmological probes based on large datasets ({\it precision cosmology}).
Despite their successes, some shortcomings emerge due to the fact that General
Relativity should be revised at infrared and ultraviolet limits and to the fact
that the fundamental nature of Dark Matter and Dark Energy is still a puzzle to
be solved. In this perspective, $f(R)$ gravity have been extensively
investigated being the most straightforward way to modify General Relativity
and to overcame some of the above shortcomings. In this paper, we review
various aspects of $f(R)$ gravity at extragalactic and cosmological levels. In
particular, we consider cluster of galaxies, cosmological perturbations, and
N-Body simulations, focusing on those models that satisfy both cosmological and
local gravity constraints. The perspective is that some classes of $f(R)$
models can be consistently constrained by Large Scale Structure.
| [
{
"created": "Wed, 22 Jul 2015 10:53:38 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jul 2015 21:53:06 GMT",
"version": "v2"
}
] | 2015-08-07 | [
[
"de Martino",
"Ivan",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | Over the past decades, General Relativity and the concordance $\Lambda$CDM model have been successfully tested using several different astrophysical and cosmological probes based on large datasets ({\it precision cosmology}). Despite their successes, some shortcomings emerge due to the fact that General Relativity should be revised at infrared and ultraviolet limits and to the fact that the fundamental nature of Dark Matter and Dark Energy is still a puzzle to be solved. In this perspective, $f(R)$ gravity have been extensively investigated being the most straightforward way to modify General Relativity and to overcame some of the above shortcomings. In this paper, we review various aspects of $f(R)$ gravity at extragalactic and cosmological levels. In particular, we consider cluster of galaxies, cosmological perturbations, and N-Body simulations, focusing on those models that satisfy both cosmological and local gravity constraints. The perspective is that some classes of $f(R)$ models can be consistently constrained by Large Scale Structure. |
1808.04412 | Jose Luis Flores | L. Ak\'e Hau, Jos\'e L. Flores, Miguel S\'anchez | Structure of globally hyperbolic spacetimes with timelike boundary | Added Appendix B and four references, several improvements in section
2.4 and other minor modifications. To appear in Rev. Mat. Iberoamericana | Rev. Matem. Iberoamericana, Volume 37, Issue 1 (2021) pp. 45-94 | 10.4171/rmi/1201 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Globally hyperbolic spacetimes with timelike boundary $(\overline{M} = M \cup
\partial M, g)$ are the natural class of spacetimes where regular boundary
conditions (eventually asymptotic, if $\overline{M}$ is obtained by means of a
conformal embedding) can be posed. $\partial M$ represents the naked
singularities and can be identified with a part of the intrinsic causal
boundary. Apart from general properties of $\partial M$, the splitting of any
globally hyperbolic $(\overline{M},g)$ as an orthogonal product ${\mathbb
R}\times \bar{\Sigma}$ with Cauchy slices with boundary $\{t\}\times
\bar{\Sigma}$ is proved. This is obtained by constructing a Cauchy temporal
function $\tau$ with gradient $\nabla \tau$ tangent to $\partial M$ on the
boundary. To construct such a $\tau$, results on stability of both, global
hyperbolicity and Cauchy temporal functions are obtained. Apart from having
their own interest, these results allow us to circumvent technical difficulties
introduced by $\partial M$. As a consequence, the interior $M$ both, splits
orthogonally and can be embedded isometrically in ${\mathbb L}^N$, extending so
properties of globally spacetimes without boundary to a class of causally
continuous ones.
| [
{
"created": "Mon, 13 Aug 2018 19:31:11 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2018 06:51:11 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Nov 2018 23:06:47 GMT",
"version": "v3"
},
{
"created": "Wed, 14 Aug 2019 08:59:21 GMT",
"version": "v4"
}
] | 2021-04-23 | [
[
"Hau",
"L. Aké",
""
],
[
"Flores",
"José L.",
""
],
[
"Sánchez",
"Miguel",
""
]
] | Globally hyperbolic spacetimes with timelike boundary $(\overline{M} = M \cup \partial M, g)$ are the natural class of spacetimes where regular boundary conditions (eventually asymptotic, if $\overline{M}$ is obtained by means of a conformal embedding) can be posed. $\partial M$ represents the naked singularities and can be identified with a part of the intrinsic causal boundary. Apart from general properties of $\partial M$, the splitting of any globally hyperbolic $(\overline{M},g)$ as an orthogonal product ${\mathbb R}\times \bar{\Sigma}$ with Cauchy slices with boundary $\{t\}\times \bar{\Sigma}$ is proved. This is obtained by constructing a Cauchy temporal function $\tau$ with gradient $\nabla \tau$ tangent to $\partial M$ on the boundary. To construct such a $\tau$, results on stability of both, global hyperbolicity and Cauchy temporal functions are obtained. Apart from having their own interest, these results allow us to circumvent technical difficulties introduced by $\partial M$. As a consequence, the interior $M$ both, splits orthogonally and can be embedded isometrically in ${\mathbb L}^N$, extending so properties of globally spacetimes without boundary to a class of causally continuous ones. |
1411.7878 | Georgios Doulis | Georgios Doulis and Oliver Rinne | Numerical construction of initial data for Einstein's equations with
static extension to space-like infinity | 20 pages, 13 figures. Agrees with the published version | Class. Quantum Grav. 33, 075014 (2016) | 10.1088/0264-9381/33/7/075014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a numerical method to construct Cauchy data extending to
space-like infinity based on Corvino's (2000) gluing method. Adopting the
setting of Giulini and Holzegel (2005), we restrict ourselves here to vacuum
axisymmetric spacetimes and glue a Schwarzschildean end to Brill-Lindquist data
describing two non-rotating black holes. Our numerical implementation is based
on pseudo-spectral methods, and we carry out extensive convergence tests to
check the validity of our numerical results. We also investigate the dependence
of the total ADM mass on the details of the gluing construction.
| [
{
"created": "Fri, 28 Nov 2014 14:30:13 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2015 12:54:39 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Dec 2016 10:41:48 GMT",
"version": "v3"
}
] | 2016-12-30 | [
[
"Doulis",
"Georgios",
""
],
[
"Rinne",
"Oliver",
""
]
] | We describe a numerical method to construct Cauchy data extending to space-like infinity based on Corvino's (2000) gluing method. Adopting the setting of Giulini and Holzegel (2005), we restrict ourselves here to vacuum axisymmetric spacetimes and glue a Schwarzschildean end to Brill-Lindquist data describing two non-rotating black holes. Our numerical implementation is based on pseudo-spectral methods, and we carry out extensive convergence tests to check the validity of our numerical results. We also investigate the dependence of the total ADM mass on the details of the gluing construction. |
1111.4586 | J. Brian Pitts | J. Brian Pitts | The Nontriviality of Trivial General Covariance: How Electrons Restrict
'Time' Coordinates, Spinors (Almost) Fit into Tensor Calculus, and 7/16 of a
Tetrad Is Surplus Structure | Forthcoming in \textit{Studies in History and Philosophy of Modern
Physics} | Studies in History and Philosophy of Modern Physics 43 (2012) 1-24 | 10.1016/j.shpsb.2011.11.001 | null | gr-qc hep-th math-ph math.MP physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is a commonplace that any theory can be written in any coordinates via
tensor calculus. But it is claimed that spinors as such cannot be represented
in coordinates in a curved space-time. What general covariance means for
theories with fermions is thus unclear. In fact both commonplaces are wrong.
Though it is not widely known, Ogievetsky and Polubarinov (OP) constructed
spinors in coordinates in 1965, helping to spawn nonlinear group
representations. Locally, these spinors resemble the orthonormal basis or
"tetrad" formalism in the symmetric gauge, but they are conceptually
self-sufficient. The tetrad formalism is de-Ockhamized, with 6 extra fields and
6 compensating gauge symmetries. OP spinors, as developed nonperturbatively by
Bilyalov, admit any coordinates at a point, but "time" must be listed first:
the product of the metric components and the matrix diag(-1,1,1,1) must have no
negative eigenvalues to yield a real symmetric square root function of the
metric. Thus the admissible coordinates depend on the types and values of the
fields. Apart from coordinate order and spinorial two-valuedness, OP spinors
form, with the metric, a nonlinear geometric object, with Lie and covariant
derivatives. Such spinors avoid a spurious absolute object in the
Anderson-Friedman analysis of substantive general covariance. They also permit
the gauge-invariant localization of the infinite-component gravitational energy
in GR. Density-weighted spinors exploit the conformal invariance of the
massless Dirac equation to show that the volume element is absent. Thus instead
of a matrix with 16 components, one can use weighted OP spinors coupled to the
9-component symmetric unimodular square root of the conformal metric density.
The surprising mildness of the restrictions on coordinates for the
Schwarzschild solution is exhibited. (edited)
| [
{
"created": "Sat, 19 Nov 2011 21:39:44 GMT",
"version": "v1"
}
] | 2016-03-21 | [
[
"Pitts",
"J. Brian",
""
]
] | It is a commonplace that any theory can be written in any coordinates via tensor calculus. But it is claimed that spinors as such cannot be represented in coordinates in a curved space-time. What general covariance means for theories with fermions is thus unclear. In fact both commonplaces are wrong. Though it is not widely known, Ogievetsky and Polubarinov (OP) constructed spinors in coordinates in 1965, helping to spawn nonlinear group representations. Locally, these spinors resemble the orthonormal basis or "tetrad" formalism in the symmetric gauge, but they are conceptually self-sufficient. The tetrad formalism is de-Ockhamized, with 6 extra fields and 6 compensating gauge symmetries. OP spinors, as developed nonperturbatively by Bilyalov, admit any coordinates at a point, but "time" must be listed first: the product of the metric components and the matrix diag(-1,1,1,1) must have no negative eigenvalues to yield a real symmetric square root function of the metric. Thus the admissible coordinates depend on the types and values of the fields. Apart from coordinate order and spinorial two-valuedness, OP spinors form, with the metric, a nonlinear geometric object, with Lie and covariant derivatives. Such spinors avoid a spurious absolute object in the Anderson-Friedman analysis of substantive general covariance. They also permit the gauge-invariant localization of the infinite-component gravitational energy in GR. Density-weighted spinors exploit the conformal invariance of the massless Dirac equation to show that the volume element is absent. Thus instead of a matrix with 16 components, one can use weighted OP spinors coupled to the 9-component symmetric unimodular square root of the conformal metric density. The surprising mildness of the restrictions on coordinates for the Schwarzschild solution is exhibited. (edited) |
1302.5560 | Burkhard Kleihaus | Efstathios Charalampidis, Theodora Ioannidou, Burkhard Kleihaus and
Jutta Kunz | Wormholes Threaded by Chiral Fields | 14 pages, 9 figures | null | 10.1103/PhysRevD.87.084069 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Lorentzian wormholes with a phantom field and chiral matter
fields. The chiral fields are described by the non-linear sigma model with or
without a Skyrme term. When the gravitational coupling of the chiral fields is
increased, the wormhole geometry changes. The single throat is replaced by a
double throat with a belly inbetween. For a maximal value of the coupling, the
radii of both throats reach zero. Then the interior part pinches off, leaving a
closed universe and two (asymptotically) flat spaces. A stability analysis
shows that all wormholes threaded by chiral fields inherit the instability of
the Ellis wormhole.
| [
{
"created": "Fri, 22 Feb 2013 11:43:55 GMT",
"version": "v1"
}
] | 2013-05-08 | [
[
"Charalampidis",
"Efstathios",
""
],
[
"Ioannidou",
"Theodora",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We consider Lorentzian wormholes with a phantom field and chiral matter fields. The chiral fields are described by the non-linear sigma model with or without a Skyrme term. When the gravitational coupling of the chiral fields is increased, the wormhole geometry changes. The single throat is replaced by a double throat with a belly inbetween. For a maximal value of the coupling, the radii of both throats reach zero. Then the interior part pinches off, leaving a closed universe and two (asymptotically) flat spaces. A stability analysis shows that all wormholes threaded by chiral fields inherit the instability of the Ellis wormhole. |
1509.04243 | Gabor Kunstatter | Gabor Kunstatter, Hideki Maeda, and Tim Taves | Designer black holes from new 2D gravity | 11 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a family of extensions of spherically symmetric
Einstein-Lanczos-Lovelock gravity. The field equations are second order and
obey a generalized Birkhoff's theorem. The Hamiltonian constraint can be
written in terms of a generalized Misner-Sharp mass function that determines
the form of the vacuum solution. The action can be designed to yield
interesting non-singular black-hole spacetimes as the unique vacuum solutions,
including the Hayward black hole as well as a completely new one. The new
theories therefore provide a consistent starting point for studying the
formation and evaporation of non-singular black holes as a possible resolution
to the black hole information loss conundrum.
| [
{
"created": "Mon, 14 Sep 2015 19:04:50 GMT",
"version": "v1"
}
] | 2015-09-16 | [
[
"Kunstatter",
"Gabor",
""
],
[
"Maeda",
"Hideki",
""
],
[
"Taves",
"Tim",
""
]
] | We present a family of extensions of spherically symmetric Einstein-Lanczos-Lovelock gravity. The field equations are second order and obey a generalized Birkhoff's theorem. The Hamiltonian constraint can be written in terms of a generalized Misner-Sharp mass function that determines the form of the vacuum solution. The action can be designed to yield interesting non-singular black-hole spacetimes as the unique vacuum solutions, including the Hayward black hole as well as a completely new one. The new theories therefore provide a consistent starting point for studying the formation and evaporation of non-singular black holes as a possible resolution to the black hole information loss conundrum. |
1505.02188 | Hooman Moradpour Hooman | H. Moradpour, N. Riazi | Spherically symmetric solutions in a FRW background | null | Mod. Phys. Lett. A 8, (2015) 1550042 | 10.1142/S021773231550042X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We impose perfect fluid concept along with slow expansion approximation to
derive new solutions which, considering non-static spherically symmetric
metrics, can be treated as Black Holes (BHs). We will refer to these solutions
as Quasi BHs. Mathematical and physical features such as Killing vectors,
singularities, and mass have been studied. Their horizons and thermodynamic
properties have also been investigated. In addition, relationship with other
related works (including McVittie's) are described.
| [
{
"created": "Mon, 4 May 2015 14:58:47 GMT",
"version": "v1"
}
] | 2015-05-12 | [
[
"Moradpour",
"H.",
""
],
[
"Riazi",
"N.",
""
]
] | We impose perfect fluid concept along with slow expansion approximation to derive new solutions which, considering non-static spherically symmetric metrics, can be treated as Black Holes (BHs). We will refer to these solutions as Quasi BHs. Mathematical and physical features such as Killing vectors, singularities, and mass have been studied. Their horizons and thermodynamic properties have also been investigated. In addition, relationship with other related works (including McVittie's) are described. |
1602.05594 | Vladimir Ivashchuk | A.A. Kobtsev, V.D. Ivashchuk and K.K. Ernazarov | On multidimensional solutions in the Einstein-Gauss-Bonnet model with a
cosmological term | 7 pages, Latex, no figures. To be published in: Proceedings of the
XII International Conference on Gravitation, Cosmology and Astrophysics,
(ICGAC-12, June 28-July 5, 2015, Moscow, PFUR), Eds. J.P. Hsu and V.N.
Melnikov, World Scientific Publ., Singapore, 2016 | null | 10.1142/9789814759816_0074 | PFUR-IGC-2016-02/01 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A D-dimensional gravitational model with Gauss-Bonnet and cosmological term
is considered. When ansatz with diagonal cosmological metrics is adopted, we
overview recent solutions for zero cosmological term and find new examples of
solutions for non-zero cosmological term and D = 8 with exponential dependence
of scale factors which describe an expansion of our 3-dimensional factor-space
and contraction of 4-dimensional internal space.
| [
{
"created": "Wed, 17 Feb 2016 21:06:17 GMT",
"version": "v1"
}
] | 2016-03-16 | [
[
"Kobtsev",
"A. A.",
""
],
[
"Ivashchuk",
"V. D.",
""
],
[
"Ernazarov",
"K. K.",
""
]
] | A D-dimensional gravitational model with Gauss-Bonnet and cosmological term is considered. When ansatz with diagonal cosmological metrics is adopted, we overview recent solutions for zero cosmological term and find new examples of solutions for non-zero cosmological term and D = 8 with exponential dependence of scale factors which describe an expansion of our 3-dimensional factor-space and contraction of 4-dimensional internal space. |
1809.01403 | Dieter L\"ust | Dieter Lust, Ward Vleeshouwers | Black Hole Information and Thermodynamics | Revised version with typos corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This SpringerBrief is based on a masters course on black hole thermodynamics
and the black hole information problem taught by Dieter L\"ust during the
summer term 2017 at the Ludwig-Maximilians-Universit\"at in Munich; it was
written by Ward Vleeshouwers. It provides a short introduction to general
relativity, which describes gravity in terms of the curvature of space-time,
and examines the properties of black holes. These are central objects in
general relativity which arise when sufficient energy is compressed into a
finite volume, so that even light cannot escape its gravitational pull. We will
see that black holes exhibit a profound connection with thermodynamic systems.
Indeed, by quantizing a field theory on curved backgrounds, one can show that
black holes emit thermal (Hawking) radiation, so that the connection with
thermodynamics is more than a formal similarity. Hawking radiation gives rise
to an apparent conflict between general relativity and quantum mechanics known
as the black hole information problem. If a black hole formed from a pure
quantum state evaporates to form thermal radiation, which is in a mixed state,
then the unitarity postulate of quantum mechanics is violated. We will examine
the black hole information problem, which has plagued the physics community for
over four decades, and consider prominent examples of proposed solutions, in
particular, the string theoretical construction of the Tangherlini black hole,
and the infinite number of asymptotic symmetries given by BMS-transformations.
| [
{
"created": "Wed, 5 Sep 2018 09:32:05 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Nov 2018 16:26:21 GMT",
"version": "v2"
}
] | 2018-11-27 | [
[
"Lust",
"Dieter",
""
],
[
"Vleeshouwers",
"Ward",
""
]
] | This SpringerBrief is based on a masters course on black hole thermodynamics and the black hole information problem taught by Dieter L\"ust during the summer term 2017 at the Ludwig-Maximilians-Universit\"at in Munich; it was written by Ward Vleeshouwers. It provides a short introduction to general relativity, which describes gravity in terms of the curvature of space-time, and examines the properties of black holes. These are central objects in general relativity which arise when sufficient energy is compressed into a finite volume, so that even light cannot escape its gravitational pull. We will see that black holes exhibit a profound connection with thermodynamic systems. Indeed, by quantizing a field theory on curved backgrounds, one can show that black holes emit thermal (Hawking) radiation, so that the connection with thermodynamics is more than a formal similarity. Hawking radiation gives rise to an apparent conflict between general relativity and quantum mechanics known as the black hole information problem. If a black hole formed from a pure quantum state evaporates to form thermal radiation, which is in a mixed state, then the unitarity postulate of quantum mechanics is violated. We will examine the black hole information problem, which has plagued the physics community for over four decades, and consider prominent examples of proposed solutions, in particular, the string theoretical construction of the Tangherlini black hole, and the infinite number of asymptotic symmetries given by BMS-transformations. |
1801.05942 | Shilpa Kastha | Shilpa Kastha, M. Saleem and K G Arun | Imprints of the redshift evolution of double neutron star merger rate on
the signal to noise ratio distribution | 9 pages, 4 figures | Monthly Notices of the Royal Astronomical Society, staa1077, 22
April 2020 | 10.1093/mnras/staa1077 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Proposed third generation gravitational wave (GW) interferometers such as
Cosmic Explorer will have the sensitivity to observe double neutron star (DNS)
mergers up to a redshift of $\sim 5$ with good signal to noise ratios. We argue
that the comoving spatial distribution of DNS mergers leaves a unique imprint
on the statistical distribution of signal to noise ratios (SNRs) of the
detected DNS mergers. Hence the SNR distribution of DNS mergers will facilitate
a novel probe of their redshift evolution independent of the luminosity
distance measurements. We consider detections of DNS mergers by the third
generation detector Cosmic Explorer and study the SNR distribution for
different possible redshift evolution models of DNSs and employ Anderson
Darling p-value statistic to demonstrate the distinguishability between these
different models. We find that a few hundreds of DNS mergers in the Cosmic
Explorer era will allow us to distinguish between different models of redshift
evolution.
| [
{
"created": "Thu, 18 Jan 2018 05:32:14 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jul 2019 11:15:23 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Apr 2020 17:50:58 GMT",
"version": "v3"
}
] | 2020-06-16 | [
[
"Kastha",
"Shilpa",
""
],
[
"Saleem",
"M.",
""
],
[
"Arun",
"K G",
""
]
] | Proposed third generation gravitational wave (GW) interferometers such as Cosmic Explorer will have the sensitivity to observe double neutron star (DNS) mergers up to a redshift of $\sim 5$ with good signal to noise ratios. We argue that the comoving spatial distribution of DNS mergers leaves a unique imprint on the statistical distribution of signal to noise ratios (SNRs) of the detected DNS mergers. Hence the SNR distribution of DNS mergers will facilitate a novel probe of their redshift evolution independent of the luminosity distance measurements. We consider detections of DNS mergers by the third generation detector Cosmic Explorer and study the SNR distribution for different possible redshift evolution models of DNSs and employ Anderson Darling p-value statistic to demonstrate the distinguishability between these different models. We find that a few hundreds of DNS mergers in the Cosmic Explorer era will allow us to distinguish between different models of redshift evolution. |
1810.11486 | Seramika Ariwahjoedi | S. Ariwahjoedi, I. Husin, I. Sebastian, F. P. Zen | Hermiticity of the Volume Operators in Loop Quantum Gravity | 15 pages, no figure | Gen. Rel. Grav. 51, 58 (2019) | 10.1007/s10714-019-2541-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of this article is to provide a rigorous-but-simple steps to prove
the hermiticity of the volume operator of Rovelli-Smolin and
Ashtekar-Lewandowski using the angular momentum approach, as well as pointing
out some subleties which have not been given a lot of attention previously.
Besides of being hermitian, we also prove that both volume operators are real,
symmetric, and positive semi-definite, with respect to the inner product
defined on the Hilbert space over SU(2). Other special properties follows from
this fact, such as the possibility to obtain real orthonormal eigenvectors.
Moreover, the matrix representation of the volume operators are degenerate,
such that the real positive eigenvalues always come in pairs for even
dimension, with an additional zero if the dimension is odd. As a consequence,
one has a freedom in choosing the orthonormal eigenvectors for each
2-dimensional eigensubspaces. Furthermore, we provide a formal procedure to
obtain the spectrum and matrix representation of the volume operators. In order
to compare our procedure with the earlier ones existing in the literature, we
give explicit computational examples for the case of monochromatic quantum
tetrahedron, where the eigenvalues agrees with the standard earlier procedure.
| [
{
"created": "Fri, 26 Oct 2018 18:26:53 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Nov 2018 15:32:15 GMT",
"version": "v2"
}
] | 2021-03-30 | [
[
"Ariwahjoedi",
"S.",
""
],
[
"Husin",
"I.",
""
],
[
"Sebastian",
"I.",
""
],
[
"Zen",
"F. P.",
""
]
] | The aim of this article is to provide a rigorous-but-simple steps to prove the hermiticity of the volume operator of Rovelli-Smolin and Ashtekar-Lewandowski using the angular momentum approach, as well as pointing out some subleties which have not been given a lot of attention previously. Besides of being hermitian, we also prove that both volume operators are real, symmetric, and positive semi-definite, with respect to the inner product defined on the Hilbert space over SU(2). Other special properties follows from this fact, such as the possibility to obtain real orthonormal eigenvectors. Moreover, the matrix representation of the volume operators are degenerate, such that the real positive eigenvalues always come in pairs for even dimension, with an additional zero if the dimension is odd. As a consequence, one has a freedom in choosing the orthonormal eigenvectors for each 2-dimensional eigensubspaces. Furthermore, we provide a formal procedure to obtain the spectrum and matrix representation of the volume operators. In order to compare our procedure with the earlier ones existing in the literature, we give explicit computational examples for the case of monochromatic quantum tetrahedron, where the eigenvalues agrees with the standard earlier procedure. |
2009.14582 | Jackson Levi Said | Rebecca Briffa, Salvatore Capozziello, Jackson Levi Said, Jurgen
Mifsud and Emmanuel N. Saridakis | Constraining Teleparallel Gravity through Gaussian Processes | 36 pages, 16 figures | null | 10.1088/1361-6382/abd4f5 | null | gr-qc astro-ph.CO hep-th physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply Gaussian processes (GP) in order to impose constraints on
teleparallel gravity and its $f(T)$ extensions. We use available $H(z)$
observations from (i) cosmic chronometers data (CC); (ii) Supernova Type Ia
(SN) data from the compressed Pantheon release together with the CANDELS and
CLASH Multi-Cycle Treasury programs; and (iii) baryonic acoustic oscillation
(BAO) datasets from the Sloan Digital Sky Survey. For the involved covariance
functions, we consider four widely used choices, namely the square exponential,
Cauchy, Mat\'{e}rn and rational quadratic kernels, which are consistent with
one another within 1$\sigma$ confidence levels. Specifically, we use the GP
approach to reconstruct a model-independent determination of the Hubble
constant $H_0$, for each of these kernels and dataset combinations. These
analyses are complemented with three recently announced literature values of
$H_0$, namely (i) Riess $H_0^{\rm R} = 74.22 \pm 1.82 \,{\rm km\, s}^{-1} {\rm
Mpc}^{-1}$; (ii) H0LiCOW Collaboration $H_0^{\rm HW} = 73.3^{+1.7}_{-1.8}
\,{\rm km\, s}^{-1} {\rm Mpc}^{-1}$; and (iii) Carnegie-Chicago Hubble Program
$H_0^{\rm TRGB} = 69.8 \pm 1.9 \,{\rm km\, s}^{-1} {\rm Mpc}^{-1}$.
Additionally, we investigate the transition redshift between the decelerating
and accelerating cosmological phases through the GP reconstructed deceleration
parameter. Furthermore, we reconstruct the model-independent evolution of the
dark energy equation of state, and finally reconstruct the allowed $f(T)$
functions. As a result, the $\Lambda$CDM model lies inside the allowed region
at 1$\sigma$ in all the examined kernels and datasets, however a negative slope
for $f(T)$ versus $T$ is slightly favored.
| [
{
"created": "Tue, 29 Sep 2020 10:02:07 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Briffa",
"Rebecca",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Mifsud",
"Jurgen",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We apply Gaussian processes (GP) in order to impose constraints on teleparallel gravity and its $f(T)$ extensions. We use available $H(z)$ observations from (i) cosmic chronometers data (CC); (ii) Supernova Type Ia (SN) data from the compressed Pantheon release together with the CANDELS and CLASH Multi-Cycle Treasury programs; and (iii) baryonic acoustic oscillation (BAO) datasets from the Sloan Digital Sky Survey. For the involved covariance functions, we consider four widely used choices, namely the square exponential, Cauchy, Mat\'{e}rn and rational quadratic kernels, which are consistent with one another within 1$\sigma$ confidence levels. Specifically, we use the GP approach to reconstruct a model-independent determination of the Hubble constant $H_0$, for each of these kernels and dataset combinations. These analyses are complemented with three recently announced literature values of $H_0$, namely (i) Riess $H_0^{\rm R} = 74.22 \pm 1.82 \,{\rm km\, s}^{-1} {\rm Mpc}^{-1}$; (ii) H0LiCOW Collaboration $H_0^{\rm HW} = 73.3^{+1.7}_{-1.8} \,{\rm km\, s}^{-1} {\rm Mpc}^{-1}$; and (iii) Carnegie-Chicago Hubble Program $H_0^{\rm TRGB} = 69.8 \pm 1.9 \,{\rm km\, s}^{-1} {\rm Mpc}^{-1}$. Additionally, we investigate the transition redshift between the decelerating and accelerating cosmological phases through the GP reconstructed deceleration parameter. Furthermore, we reconstruct the model-independent evolution of the dark energy equation of state, and finally reconstruct the allowed $f(T)$ functions. As a result, the $\Lambda$CDM model lies inside the allowed region at 1$\sigma$ in all the examined kernels and datasets, however a negative slope for $f(T)$ versus $T$ is slightly favored. |
0807.4559 | Kristin Schleich | K. Schleich and D. M. Witt | Designer de Sitter Spacetimes | 6 pages, no figure, correction of sign in eq. 4 | Can. J. Phys. 86, 591-595 (2008) | 10.1139/P07-191 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observations in cosmology indicate an accelerating expansion of the
universe postulated to arise from some form of dark energy, the paradigm being
positive cosmological constant. De Sitter spacetime is the well-known isotropic
solution to the Einstein equations with cosmological constant. However, as
discussed here, it is not the most general, locally isotropic solution. One can
construct an infinite family of such solutions, designer de Sitter spacetimes,
which are everywhere locally isometric to a region of de Sitter spacetime.
However, the global dynamics of these designer cosmologies is very different
than that of de Sitter spacetime itself. The construction and dynamics of these
designer de Sitter spacetimes is detailed along with some comments about their
implications for the structure of our universe.
| [
{
"created": "Mon, 28 Jul 2008 23:39:41 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Sep 2008 22:26:40 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Schleich",
"K.",
""
],
[
"Witt",
"D. M.",
""
]
] | Recent observations in cosmology indicate an accelerating expansion of the universe postulated to arise from some form of dark energy, the paradigm being positive cosmological constant. De Sitter spacetime is the well-known isotropic solution to the Einstein equations with cosmological constant. However, as discussed here, it is not the most general, locally isotropic solution. One can construct an infinite family of such solutions, designer de Sitter spacetimes, which are everywhere locally isometric to a region of de Sitter spacetime. However, the global dynamics of these designer cosmologies is very different than that of de Sitter spacetime itself. The construction and dynamics of these designer de Sitter spacetimes is detailed along with some comments about their implications for the structure of our universe. |
2210.11959 | Cosimo Bambi | Cosimo Bambi | Search for Variations of Fundamental Constants | 15 pages, no figures. Chapter for the book "Recent Progress on
Gravity Tests" (Eds. C. Bambi and A. C\'ardenas-Avenda\~no, Springer
Singapore, expected in 2023) | null | 10.1007/978-981-97-2871-8_10 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possibility of variations of the values of fundamental constants is a
phenomenon predicted by a number of scenarios beyond General Relativity. This
can happen if ``our'' fundamental constants are not the actual constants of the
fundamental theory and their value is instead determined, for example, by the
background value of some new field or the size of extra dimensions. So far,
most studies have been devoted to constrain possible temporal variations of the
electromagnetic fine structure constant $\alpha$, the proton to electron mass
ratio $\mu = m_p/m_e$, and the gravitational constant $G_{\rm N}$. Apart some
claims of the detection of a temporal or spatial variation of $\alpha$ and
$\mu$, so far there is no clear observational evidence of any variation of our
fundamental constants.
| [
{
"created": "Fri, 21 Oct 2022 13:33:56 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Bambi",
"Cosimo",
""
]
] | The possibility of variations of the values of fundamental constants is a phenomenon predicted by a number of scenarios beyond General Relativity. This can happen if ``our'' fundamental constants are not the actual constants of the fundamental theory and their value is instead determined, for example, by the background value of some new field or the size of extra dimensions. So far, most studies have been devoted to constrain possible temporal variations of the electromagnetic fine structure constant $\alpha$, the proton to electron mass ratio $\mu = m_p/m_e$, and the gravitational constant $G_{\rm N}$. Apart some claims of the detection of a temporal or spatial variation of $\alpha$ and $\mu$, so far there is no clear observational evidence of any variation of our fundamental constants. |
gr-qc/0001034 | Kazuya Koyama | Kazuya Koyama, Kayoko Maeda and Jiro Soda | Creation of an Open Universe from Valley Bounce | LaTeX, 8 pages, 2 figure, Presented at 9th Workshop on General
Relativity and Gravitation, Hiroshima, Japan, Nov 3-6, 1999, For details see
hep-ph/9910556 | null | null | null | gr-qc | null | It appears difficult to construct a simple model for an open universe based
on the one bubble inflationary scenario. The reason is that one needs a large
mass to avoid the tunneling via the Hawking Moss solution and a small mass for
successful slow-rolling. However, Rubakov and Sibiryakov suggest that the
Hawking Moss solution is not a solution for the false vacuum decay process
since it does not satisfy the boundary condition. Hence, we have reconsidered
the arguments for the defect of the simple polynomial model. We find the valley
bounce belonging to a valley line in the functional space represents the decay
process instead of the Hawking Moss solution. The point is that the valley
bounce gives the appropriate initial condition for the inflation. We show an
open inflation model can be constructed within the polynomial form of the
potential so that the fluctuations can be reconciled with the observations.
| [
{
"created": "Wed, 12 Jan 2000 09:09:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Koyama",
"Kazuya",
""
],
[
"Maeda",
"Kayoko",
""
],
[
"Soda",
"Jiro",
""
]
] | It appears difficult to construct a simple model for an open universe based on the one bubble inflationary scenario. The reason is that one needs a large mass to avoid the tunneling via the Hawking Moss solution and a small mass for successful slow-rolling. However, Rubakov and Sibiryakov suggest that the Hawking Moss solution is not a solution for the false vacuum decay process since it does not satisfy the boundary condition. Hence, we have reconsidered the arguments for the defect of the simple polynomial model. We find the valley bounce belonging to a valley line in the functional space represents the decay process instead of the Hawking Moss solution. The point is that the valley bounce gives the appropriate initial condition for the inflation. We show an open inflation model can be constructed within the polynomial form of the potential so that the fluctuations can be reconciled with the observations. |
2205.09758 | Subhayan Maity | Subhayan Maity | Non-equilibrium thermodynamics in the non-canonical scalar field
perturbed space-time : Stability analysis | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The space-time of the Universe has been perturbed under a scalar field $\phi$
considering the minimum coupling between {\phi} and the background metric. The
solutions of Einstein field equations have been obtained under perturbed
geometry and the corresponding conservation equation shows the non-equilibrium
thermodynamic prescription of the cosmic fluid. Following the stability
criteria of the cosmic fluid along with the laws of thermodynamics, some
constraints have been imposed on the choice of $\phi$.
| [
{
"created": "Thu, 19 May 2022 07:29:02 GMT",
"version": "v1"
},
{
"created": "Tue, 31 May 2022 13:06:20 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Jun 2022 18:56:22 GMT",
"version": "v3"
},
{
"created": "Sun, 16 Oct 2022 14:31:15 GMT",
"version": "v4"
}
] | 2022-10-18 | [
[
"Maity",
"Subhayan",
""
]
] | The space-time of the Universe has been perturbed under a scalar field $\phi$ considering the minimum coupling between {\phi} and the background metric. The solutions of Einstein field equations have been obtained under perturbed geometry and the corresponding conservation equation shows the non-equilibrium thermodynamic prescription of the cosmic fluid. Following the stability criteria of the cosmic fluid along with the laws of thermodynamics, some constraints have been imposed on the choice of $\phi$. |
2104.00594 | Gr\'egory Baltus | Gregory Baltus, Justin Janquart, Melissa Lopez, Amit Reza, Sarah
Caudill, Jean-Rene Cudell | Convolutional neural networks for the detection of the early inspiral of
a gravitational-wave signal | 12 pages, 14 figures | Phys. Rev. D 103, 102003 (2021) | 10.1103/PhysRevD.103.102003 | LIGO DCC number LIGO-P2100087 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | GW170817 has led to the first example of multi-messenger astronomy with
observations from gravitational wave interferometers and electromagnetic
telescopes combined to characterise the source. However, detections of the
early inspiral phase by the gravitational wave detectors would allow the
observation of the earlier stages of the merger in the electromagnetic band,
improving multi-messenger astronomy and giving access to new information. In
this paper, we introduce a new machine-learning-based approach to produce
early-warning alerts for an inspiraling binary neutron star system, based only
on the early inspiral part of the signal. We give a proof of concept to show
the possibility to use a combination of small convolutional neural networks
trained on the whitened detector strain in the time domain to detect and
classify early inspirals. Each of those is targeting a specific range of chirp
masses dividing the binary neutron star category into three sub-classes: light,
intermediate and heavy. In this work, we focus on one LIGO detector at design
sensitivity and generate noise from the design power spectral density. We show
that within this setup it is possible to produce an early alert up to 100
seconds before the merger for the best-case scenario. We also present some
future upgrades that will enhance the detection capabilities of our
convolutional neural networks. Finally, we also show that the current number of
detections for a realistic binary neutron star population is comparable to that
of matched filtering and that there is a high probability to detect GW170817-
and GW190425-like events at design sensitivity.
| [
{
"created": "Thu, 1 Apr 2021 16:22:09 GMT",
"version": "v1"
}
] | 2021-05-26 | [
[
"Baltus",
"Gregory",
""
],
[
"Janquart",
"Justin",
""
],
[
"Lopez",
"Melissa",
""
],
[
"Reza",
"Amit",
""
],
[
"Caudill",
"Sarah",
""
],
[
"Cudell",
"Jean-Rene",
""
]
] | GW170817 has led to the first example of multi-messenger astronomy with observations from gravitational wave interferometers and electromagnetic telescopes combined to characterise the source. However, detections of the early inspiral phase by the gravitational wave detectors would allow the observation of the earlier stages of the merger in the electromagnetic band, improving multi-messenger astronomy and giving access to new information. In this paper, we introduce a new machine-learning-based approach to produce early-warning alerts for an inspiraling binary neutron star system, based only on the early inspiral part of the signal. We give a proof of concept to show the possibility to use a combination of small convolutional neural networks trained on the whitened detector strain in the time domain to detect and classify early inspirals. Each of those is targeting a specific range of chirp masses dividing the binary neutron star category into three sub-classes: light, intermediate and heavy. In this work, we focus on one LIGO detector at design sensitivity and generate noise from the design power spectral density. We show that within this setup it is possible to produce an early alert up to 100 seconds before the merger for the best-case scenario. We also present some future upgrades that will enhance the detection capabilities of our convolutional neural networks. Finally, we also show that the current number of detections for a realistic binary neutron star population is comparable to that of matched filtering and that there is a high probability to detect GW170817- and GW190425-like events at design sensitivity. |
0906.0990 | Guillermo A. Gonzalez | Guillermo A. Gonz\'alez, Antonio C. Guti\'errez-Pi\~neres, Viviana M.
Vi\~na-Cervantes | Exact Static Axially Symmetric Thin Annular Dust Disks | Physics and Mathematics of Gravitation: Proceedings of the Spanish
Relativity Meeting 2008 | AIP Conf.Proc.1122:284-287,2009 | 10.1063/1.3141294 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new family of exact solutions of the Einstein field equations for static
and axially simmetric spacetimes is presented. All the metric functions of the
solutions are explicitly computed and the obtained expressions are simply
written in terms of oblate spheroidal coordinates. The solutions describe an
infinite family of static axially symmetric thin annular dust disks. The disk
are of infinite extension but with an inner annular edge. The energy densities
of the disks are everywhere positive functions of the radial coordinate, equals
to zero at the inner edge of the disk, having a maximun at a finite value of
the radius and then vanishing at infinity. The disks have finite mass and their
energy-momentum tensor agrees with all the energy conditions.
| [
{
"created": "Thu, 4 Jun 2009 20:19:15 GMT",
"version": "v1"
}
] | 2010-11-22 | [
[
"González",
"Guillermo A.",
""
],
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"Viña-Cervantes",
"Viviana M.",
""
]
] | A new family of exact solutions of the Einstein field equations for static and axially simmetric spacetimes is presented. All the metric functions of the solutions are explicitly computed and the obtained expressions are simply written in terms of oblate spheroidal coordinates. The solutions describe an infinite family of static axially symmetric thin annular dust disks. The disk are of infinite extension but with an inner annular edge. The energy densities of the disks are everywhere positive functions of the radial coordinate, equals to zero at the inner edge of the disk, having a maximun at a finite value of the radius and then vanishing at infinity. The disks have finite mass and their energy-momentum tensor agrees with all the energy conditions. |
1009.0647 | Angus Prain | Angus Prain, Serena Fagnocchi and Stefano Liberati | Analogue Cosmological Particle Creation: Quantum Correlations in
Expanding Bose Einstein Condensates | Reference added | Phys.Rev.D82:105018,2010 | 10.1103/PhysRevD.82.105018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the structure of quantum correlations in an expanding Bose
Einstein Condensate (BEC) through the analogue gravity framework. We consider
both a 3+1 isotropically expanding BEC as well as the experimentally relevant
case of an elongated, effectively 1+1 dimensional, expanding condensate. In
this case we include the effects of inhomogeneities in the condensate, a
feature rarely included in the analogue gravity literature. In both cases we
link the BEC expansion to a simple model for an expanding spacetime and then
study the correlation structure numerically and analytically (in suitable
approximations). We also discuss the expected strength of such correlation
patterns and experimentally feasible BEC systems in which these effects might
be detected in the near future.
| [
{
"created": "Fri, 3 Sep 2010 12:51:50 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Sep 2010 13:30:34 GMT",
"version": "v2"
}
] | 2010-12-09 | [
[
"Prain",
"Angus",
""
],
[
"Fagnocchi",
"Serena",
""
],
[
"Liberati",
"Stefano",
""
]
] | We investigate the structure of quantum correlations in an expanding Bose Einstein Condensate (BEC) through the analogue gravity framework. We consider both a 3+1 isotropically expanding BEC as well as the experimentally relevant case of an elongated, effectively 1+1 dimensional, expanding condensate. In this case we include the effects of inhomogeneities in the condensate, a feature rarely included in the analogue gravity literature. In both cases we link the BEC expansion to a simple model for an expanding spacetime and then study the correlation structure numerically and analytically (in suitable approximations). We also discuss the expected strength of such correlation patterns and experimentally feasible BEC systems in which these effects might be detected in the near future. |
2208.03170 | Justin Vines | M. V. S. Saketh and Justin Vines | Scattering of gravitational waves off spinning compact objects with an
effective worldline theory | v2: minor corrections and additional discussion; two-column format;
submitted to PRD | null | 10.1103/PhysRevD.106.124026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the process, within classical general relativity, in which an
incident gravitational plane wave, of weak amplitude and long wavelength,
scatters off a massive spinning compact object, such as a black hole or neutron
star. The amplitude of the asymptotic scattered wave, considered here at linear
order in Newton's constant $G$ while at higher orders in the object's multipole
expansion, is a valuable characterization of the response of the object to
external gravitational fields. This amplitude coincides with a classical
($\hbar\to0$) limit of a quantum 4-point (object and graviton in, object and
graviton out) gravitational Compton amplitude, at the tree (linear-in-$G$)
level. Such tree-level Compton amplitudes are key building blocks in
generalized-unitary-based approaches to the post-Minkowskian dynamics of
binaries of spinning compact objects. In this paper, we compute the classical
amplitude using an effective worldline theory to describe the compact object,
determined by an action functional for translational and rotational degrees of
freedom, including couplings of spin-induced higher multipole moments to
spacetime curvature. We work here up to the levels of quadratic-in-spin
quadrupole and cubic-in-spin octupole couplings, respectively involving Wilson
coefficients $C_2$ and $C_3$. For the special case $C_2=C_3=1$ corresponding to
a black hole, we find agreement through cubic-in-spin order between our
classical amplitude and previous conjectures arising from considerations of
quantum scattering amplitudes. We also present new results for general $C_2$
and $C_3$, anticipating instructive comparisons with results from effective
quantum theories.
| [
{
"created": "Fri, 5 Aug 2022 13:56:28 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2022 10:43:15 GMT",
"version": "v2"
}
] | 2023-01-04 | [
[
"Saketh",
"M. V. S.",
""
],
[
"Vines",
"Justin",
""
]
] | We study the process, within classical general relativity, in which an incident gravitational plane wave, of weak amplitude and long wavelength, scatters off a massive spinning compact object, such as a black hole or neutron star. The amplitude of the asymptotic scattered wave, considered here at linear order in Newton's constant $G$ while at higher orders in the object's multipole expansion, is a valuable characterization of the response of the object to external gravitational fields. This amplitude coincides with a classical ($\hbar\to0$) limit of a quantum 4-point (object and graviton in, object and graviton out) gravitational Compton amplitude, at the tree (linear-in-$G$) level. Such tree-level Compton amplitudes are key building blocks in generalized-unitary-based approaches to the post-Minkowskian dynamics of binaries of spinning compact objects. In this paper, we compute the classical amplitude using an effective worldline theory to describe the compact object, determined by an action functional for translational and rotational degrees of freedom, including couplings of spin-induced higher multipole moments to spacetime curvature. We work here up to the levels of quadratic-in-spin quadrupole and cubic-in-spin octupole couplings, respectively involving Wilson coefficients $C_2$ and $C_3$. For the special case $C_2=C_3=1$ corresponding to a black hole, we find agreement through cubic-in-spin order between our classical amplitude and previous conjectures arising from considerations of quantum scattering amplitudes. We also present new results for general $C_2$ and $C_3$, anticipating instructive comparisons with results from effective quantum theories. |
gr-qc/9711004 | Pierre Savaria | Pierre Savaria | Anisotropic Homogeneous Cosmology in the Nonsymmetric Theory of
Gravitation | 13 pages, TeX, no figure | null | null | UTPT-97-22 | gr-qc | null | Solutions to the field equations of the Nonsymmetric Gravitational Theory
with $g_[i0] = 0$ are obtained for the homogeneous, plane-symmetric,
time-dependent case, both in vacuum and in the presence of a perfect fluid.
Cosmological consequences include a dependence of the speed of light on its
polarisation, as in a birefringent crystal.
| [
{
"created": "Mon, 3 Nov 1997 18:58:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Savaria",
"Pierre",
""
]
] | Solutions to the field equations of the Nonsymmetric Gravitational Theory with $g_[i0] = 0$ are obtained for the homogeneous, plane-symmetric, time-dependent case, both in vacuum and in the presence of a perfect fluid. Cosmological consequences include a dependence of the speed of light on its polarisation, as in a birefringent crystal. |
2203.14595 | Athanasios Bakopoulos | Athanasios Bakopoulos, Christos Charmousis, Panagiota Kanti, Nicolas
Lecoeur | Compact objects of spherical symmetry in beyond Horndeski theories | References updated, typos corrected, matches published version | JHEP 08 (2022) 055 | 10.1007/JHEP08(2022)055 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We analyse in all generality beyond Horndeski theories of shift symmetry in a
static and spherically symmetric spacetime. By introducing four auxiliary
functions, we write the field equations in a particularly compact form. We show
that assuming additionally parity symmetry renders the system directly
integrable giving multiple families of black-hole solutions. These have
typically an asymptotically-flat Reissner-Nordstrom behaviour, and emerge in
the presence of a canonical kinetic term for the scalar field. In the absence
of parity symmetry, we present a general method which allows us to integrate
the field equations by choosing the form of only one coupling function and an
auxiliary quantity. This method leads to asymptotically flat and AdS black hole
solutions with differing properties. We finally discuss disformal
transformations within this context as a means of obtaining wormhole and black
hole solutions in different theories.
| [
{
"created": "Mon, 28 Mar 2022 09:15:15 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Aug 2022 16:44:50 GMT",
"version": "v2"
}
] | 2022-08-11 | [
[
"Bakopoulos",
"Athanasios",
""
],
[
"Charmousis",
"Christos",
""
],
[
"Kanti",
"Panagiota",
""
],
[
"Lecoeur",
"Nicolas",
""
]
] | We analyse in all generality beyond Horndeski theories of shift symmetry in a static and spherically symmetric spacetime. By introducing four auxiliary functions, we write the field equations in a particularly compact form. We show that assuming additionally parity symmetry renders the system directly integrable giving multiple families of black-hole solutions. These have typically an asymptotically-flat Reissner-Nordstrom behaviour, and emerge in the presence of a canonical kinetic term for the scalar field. In the absence of parity symmetry, we present a general method which allows us to integrate the field equations by choosing the form of only one coupling function and an auxiliary quantity. This method leads to asymptotically flat and AdS black hole solutions with differing properties. We finally discuss disformal transformations within this context as a means of obtaining wormhole and black hole solutions in different theories. |
1204.1199 | Laszlo Arpad Gergely | Zolt\'an Keresztes, L\'aszl\'o \'A. Gergely, Alexander Yu. Kamenshchik | The paradox of soft singularity crossing and its resolution by
distributional cosmological quantitities | 12 pages; to be published in Phys.Rev.D | Phys.Rev.D86:063522,2012 | 10.1103/PhysRevD.86.063522 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological model of a flat Friedmann universe filled with a mixture of
anti-Chaplygin gas and dust-like matter exhibits a future soft singularity,
where the pressure of the anti-Chaplygin gas diverges (while its energy density
is finite). Despite infinite tidal forces the geodesics pass through the
singularity. Due to the dust component, the Hubble parameter has a non-zero
value at the encounter with the singularity, therefore the dust implies further
expansion. With continued expansion however, the energy density and the
pressure of the anti-Chaplygin gas would become ill-defined, hence from the
point of view of the anti-Chaplygin gas only a contraction is allowed.
Paradoxically, the universe in this cosmological model would have to expand and
contract simultaneously. This obviosly could not happen. We solve the paradox
by redefining the anti-Chaplygin gas in a distributional sense. Then a
contraction could follow the expansion phase at the singularity at the price of
a jump in the Hubble parameter. Although such an abrupt change is not common in
any cosmological evolution, we explicitly show that the set of Friedmann,
Raychaudhuri and continuity equations are all obeyed both at the singularity
and in its vicinity. We also prove that the Israel junction conditions are
obeyed through the singular spatial hypersurface. In particular we enounce and
prove a more general form of the Lanczos equation.
| [
{
"created": "Thu, 5 Apr 2012 12:28:15 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Sep 2012 09:19:51 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Keresztes",
"Zoltán",
""
],
[
"Gergely",
"László Á.",
""
],
[
"Kamenshchik",
"Alexander Yu.",
""
]
] | A cosmological model of a flat Friedmann universe filled with a mixture of anti-Chaplygin gas and dust-like matter exhibits a future soft singularity, where the pressure of the anti-Chaplygin gas diverges (while its energy density is finite). Despite infinite tidal forces the geodesics pass through the singularity. Due to the dust component, the Hubble parameter has a non-zero value at the encounter with the singularity, therefore the dust implies further expansion. With continued expansion however, the energy density and the pressure of the anti-Chaplygin gas would become ill-defined, hence from the point of view of the anti-Chaplygin gas only a contraction is allowed. Paradoxically, the universe in this cosmological model would have to expand and contract simultaneously. This obviosly could not happen. We solve the paradox by redefining the anti-Chaplygin gas in a distributional sense. Then a contraction could follow the expansion phase at the singularity at the price of a jump in the Hubble parameter. Although such an abrupt change is not common in any cosmological evolution, we explicitly show that the set of Friedmann, Raychaudhuri and continuity equations are all obeyed both at the singularity and in its vicinity. We also prove that the Israel junction conditions are obeyed through the singular spatial hypersurface. In particular we enounce and prove a more general form of the Lanczos equation. |
gr-qc/9805102 | Daniel Kennefick | Daniel Kennefick | Stability under radiation reaction of circular equatorial orbits around
Kerr black holes | Revtex, 20 pages including three figures | Phys.Rev. D58 (1998) 064012 | 10.1103/PhysRevD.58.064012 | null | gr-qc | null | We examine the evolution, under gravitational radiation reaction, of slightly
eccentric equatorial orbits of point particles around Kerr black holes. Our
method involves numerical integration of the Sasaki-Nakamura equation. It is
discovered that such orbits decrease in eccentricity throughout most of the
inspiral, until shortly before the innermost stable circular orbit (ISCO), when
a critical radius $r_{\text{crit}}$ is reached beyond which the inspiralling
orbits increase in eccentricity. It is shown that the number of orbits
remaining in this last (eccentricity increasing) phase of the inspiral is an
order of magnitude less for prograde orbits around rapidly spinning black holes
than for retrograde orbits. In the extreme limit of a Kerr black hole with spin
parameter $a=1$, this critical radius descends into the ``throat'' of the black
hole.
| [
{
"created": "Fri, 29 May 1998 14:42:53 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kennefick",
"Daniel",
""
]
] | We examine the evolution, under gravitational radiation reaction, of slightly eccentric equatorial orbits of point particles around Kerr black holes. Our method involves numerical integration of the Sasaki-Nakamura equation. It is discovered that such orbits decrease in eccentricity throughout most of the inspiral, until shortly before the innermost stable circular orbit (ISCO), when a critical radius $r_{\text{crit}}$ is reached beyond which the inspiralling orbits increase in eccentricity. It is shown that the number of orbits remaining in this last (eccentricity increasing) phase of the inspiral is an order of magnitude less for prograde orbits around rapidly spinning black holes than for retrograde orbits. In the extreme limit of a Kerr black hole with spin parameter $a=1$, this critical radius descends into the ``throat'' of the black hole. |
1808.05703 | Dimitry Ayzenberg | Harrison Gott, Dimitry Ayzenberg, Nicolas Yunes, Anne Lohfink | Observing the Shadows of Stellar-Mass Black Holes with Binary Companions | 24 pages, 5 Figures, 2 Tables. Videos included in supplemental
material. Submitted to CQG | null | 10.1088/1361-6382/ab01b0 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of the shadows cast by the event horizon of black holes on
the light emitted in its neighborhood is the target of current
very-long-baseline-interferometric observations. When considering supermassive
black holes, the light source is the black hole's accretion disk, and
therefore, the observation of the shadow may reveal information about the black
hole and the accretion flow. We here study the shadows cast by stellar-mass
black holes that are illuminated not by an accretion disk but by a stellar
companion in a wide binary orbit. We calculate the shadows produced in such a
configuration for the first time and show snapshots of the time-dependent
shadow "movie" that is generated. We also study the minimal criteria for
detecting and resolving such shadows with very-long-baseline-interferometric
observations. We find that one would need telescopes capable of resolving
apparent magnitudes greater than $33$ with baselines larger than $10^{6}$ km.
Therefore, although very-long-baseline-interferometric efforts such as the
Event Horizon Telescope would not be able to detect these shadows, their
detection is possible with future telescopes in the next few decades.
| [
{
"created": "Thu, 16 Aug 2018 23:19:14 GMT",
"version": "v1"
}
] | 2019-02-20 | [
[
"Gott",
"Harrison",
""
],
[
"Ayzenberg",
"Dimitry",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Lohfink",
"Anne",
""
]
] | The observation of the shadows cast by the event horizon of black holes on the light emitted in its neighborhood is the target of current very-long-baseline-interferometric observations. When considering supermassive black holes, the light source is the black hole's accretion disk, and therefore, the observation of the shadow may reveal information about the black hole and the accretion flow. We here study the shadows cast by stellar-mass black holes that are illuminated not by an accretion disk but by a stellar companion in a wide binary orbit. We calculate the shadows produced in such a configuration for the first time and show snapshots of the time-dependent shadow "movie" that is generated. We also study the minimal criteria for detecting and resolving such shadows with very-long-baseline-interferometric observations. We find that one would need telescopes capable of resolving apparent magnitudes greater than $33$ with baselines larger than $10^{6}$ km. Therefore, although very-long-baseline-interferometric efforts such as the Event Horizon Telescope would not be able to detect these shadows, their detection is possible with future telescopes in the next few decades. |
0901.4828 | Lau Loi So | Lau Loi So | An alternative non-negative gravitational energy tensor to the
Bel-Robinson tensor | 7 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Bel-Robinson tensor $B_{\alpha\beta\mu\nu}$ gives a positive definite
gravitational energy in the small sphere limit approximation. However, there is
an alternative tensor $V_{\alpha\beta\mu\nu}$ which was proposed recently that
offers the same positivity as $B_{\alpha\beta\mu\nu}$ does. These two tensors
are a basis for expressions which have the desirable non-negative gravitational
energy in the small sphere region limit.
| [
{
"created": "Fri, 30 Jan 2009 06:23:42 GMT",
"version": "v1"
}
] | 2009-02-02 | [
[
"So",
"Lau Loi",
""
]
] | The Bel-Robinson tensor $B_{\alpha\beta\mu\nu}$ gives a positive definite gravitational energy in the small sphere limit approximation. However, there is an alternative tensor $V_{\alpha\beta\mu\nu}$ which was proposed recently that offers the same positivity as $B_{\alpha\beta\mu\nu}$ does. These two tensors are a basis for expressions which have the desirable non-negative gravitational energy in the small sphere region limit. |
1905.07340 | Adrien Kuntz | Adrien Kuntz | The two-body potential of Vainshtein screened theories | 15 pages, 8 figures | Phys. Rev. D 100, 024024 (2019) | 10.1103/PhysRevD.100.024024 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Adding a light scalar degree of freedom to General Relativity often induces a
fifth force whose magnitude is strongly constrained by laboratory experiments
and solar system tests. The Vainshtein screening mechanism ensures that the
effects of this supplementary force are suppressed in dense environments.
However, the field solution of theories exhibiting Vainshtein screening is only
known in spherically symmetric situations. In this article we examine in
different configurations the two-body potential energy of pointlike particles
in a specific $P(X)$ theory with Vainshtein screening. We use ideas borrowed
from the Effective One-Body approach of Buonanno and Damour in order to
restrict the form of the solution. Our results indicate that, even if
Vainshtein screening is also fully active in the equal-mass case, the nonlinear
dependance of the two-body energy on the mass ratio implies a violation of the
Equivalence Principle. We compute the contribution of this effect to the Moon
orbit for generic theories equipped with Vainshtein screening.
| [
{
"created": "Fri, 17 May 2019 15:55:18 GMT",
"version": "v1"
}
] | 2019-07-24 | [
[
"Kuntz",
"Adrien",
""
]
] | Adding a light scalar degree of freedom to General Relativity often induces a fifth force whose magnitude is strongly constrained by laboratory experiments and solar system tests. The Vainshtein screening mechanism ensures that the effects of this supplementary force are suppressed in dense environments. However, the field solution of theories exhibiting Vainshtein screening is only known in spherically symmetric situations. In this article we examine in different configurations the two-body potential energy of pointlike particles in a specific $P(X)$ theory with Vainshtein screening. We use ideas borrowed from the Effective One-Body approach of Buonanno and Damour in order to restrict the form of the solution. Our results indicate that, even if Vainshtein screening is also fully active in the equal-mass case, the nonlinear dependance of the two-body energy on the mass ratio implies a violation of the Equivalence Principle. We compute the contribution of this effect to the Moon orbit for generic theories equipped with Vainshtein screening. |
gr-qc/9712066 | WU Zhong Chao | Wu Zhong Chao (ICRA) | Quantum Fields in Schwarzschild-de Sitter Space | 24 pages | Int.J.Mod.Phys. D7 (1998) 887-907 | null | ICRA-97-101 | gr-qc hep-th | null | In the No-Boundary Universe a primordial black hole is created from a
constrained gravitational instanton. The black hole created is immersed in the
de Sitter background with a positive cosmological constant. The constrained
instanton is characterized not only by the external parameters, the mass
parameter, charge and angular momentum, but also by one more internal
parameter, the identification period in the imaginary time coordinate. Although
the period has no effect on the black hole background, its inverse is the
temperature of the no-boundary state of the perturbation modes perceived by an
observer. By using the Bogoliubov transformation, we show that the perturbation
modes of both scalar and spinor fields are in thermal q equilibrium with the
black hole background at the arbitrary temperature. However, for the two
extreme cases, the de Sitter and the Nariai models, the no-boundary state
remains pure.
| [
{
"created": "Mon, 15 Dec 1997 20:56:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Chao",
"Wu Zhong",
"",
"ICRA"
]
] | In the No-Boundary Universe a primordial black hole is created from a constrained gravitational instanton. The black hole created is immersed in the de Sitter background with a positive cosmological constant. The constrained instanton is characterized not only by the external parameters, the mass parameter, charge and angular momentum, but also by one more internal parameter, the identification period in the imaginary time coordinate. Although the period has no effect on the black hole background, its inverse is the temperature of the no-boundary state of the perturbation modes perceived by an observer. By using the Bogoliubov transformation, we show that the perturbation modes of both scalar and spinor fields are in thermal q equilibrium with the black hole background at the arbitrary temperature. However, for the two extreme cases, the de Sitter and the Nariai models, the no-boundary state remains pure. |
1108.3550 | Thomas W. Baumgarte | Thomas W. Baumgarte | Puncture black hole initial data in the conformal thin-sandwich
formalism | 17 pages, 4 figures | null | 10.1088/0264-9381/28/21/215003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the construction of puncture black hole initial data in the
conformal thin-sandwich decomposition of Einstein's constraint equations. It
has been shown previously that this approach cannot yield quasiequilibrium
wormhole data, which connect two asymptotically flat spatial infinities. This
argument does not apply to trumpet data, which connect the spatial infinity in
one universe with the future timelike infinity of another. As a numerical
demonstration we present results for a single boosted trumpet-puncture black
holes, constructed in the original version of the conformal thin-sandwich
formalism.
| [
{
"created": "Wed, 17 Aug 2011 18:59:01 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Baumgarte",
"Thomas W.",
""
]
] | We revisit the construction of puncture black hole initial data in the conformal thin-sandwich decomposition of Einstein's constraint equations. It has been shown previously that this approach cannot yield quasiequilibrium wormhole data, which connect two asymptotically flat spatial infinities. This argument does not apply to trumpet data, which connect the spatial infinity in one universe with the future timelike infinity of another. As a numerical demonstration we present results for a single boosted trumpet-puncture black holes, constructed in the original version of the conformal thin-sandwich formalism. |
2003.09486 | Roberto Percacci | Roberto Percacci | Towards Metric-Affine Quantum Gravity | Talk given at PAFT2019, Vietri sul Mare, Italy; to appear in
International Journal of Geometric Methods in Modern Physics | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review here some motivations to consider a theory of gravity based on
independent metric and connection, and its status as a quantum theory.
| [
{
"created": "Fri, 20 Mar 2020 20:19:15 GMT",
"version": "v1"
}
] | 2020-03-24 | [
[
"Percacci",
"Roberto",
""
]
] | I review here some motivations to consider a theory of gravity based on independent metric and connection, and its status as a quantum theory. |
gr-qc/9406012 | Haret Rosu | H.C. Rosu | Hawking-like effects and Unruh-like effects: toward experiments ? | 31 pages, revised, a few references updated | Grav.Cosmol. 7 (2001) 1-17 | null | null | gr-qc | null | The Hawking effect and the Unruh effect are two of the most important
predictions in the theoretical physics of the last quarter of the 20th century.
In parallel to the theoretical investigations there is great interest in the
possibility of revealing effects of this type in some sort of experiments. I
present a general discussion of the proposals to measure the Hawking and Unruh
effects and/or their `analogues' in the laboratory, and I make brief comments
on each of them. The reader may also find the various physical pictures
corresponding to the two effects which were applied to more common phenomena,
and vice versa
| [
{
"created": "Mon, 6 Jun 1994 23:40:00 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 1996 01:49:00 GMT",
"version": "v2"
},
{
"created": "Tue, 30 Dec 1997 23:57:24 GMT",
"version": "v3"
},
{
"created": "Wed, 31 Dec 1997 03:20:16 GMT",
"version": "v4"
},
{
"cr... | 2008-02-03 | [
[
"Rosu",
"H. C.",
""
]
] | The Hawking effect and the Unruh effect are two of the most important predictions in the theoretical physics of the last quarter of the 20th century. In parallel to the theoretical investigations there is great interest in the possibility of revealing effects of this type in some sort of experiments. I present a general discussion of the proposals to measure the Hawking and Unruh effects and/or their `analogues' in the laboratory, and I make brief comments on each of them. The reader may also find the various physical pictures corresponding to the two effects which were applied to more common phenomena, and vice versa |
1801.08208 | Lionel London | L. London | Modeling ringdown II: non-precessing binary black holes | null | Phys. Rev. D 102, 084052 (2020) | 10.1103/PhysRevD.102.084052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aftermath of binary black hole coalescence is a perturbed remnant whose
gravitational radiation rings down, encoding information about the new black
hole's recent history and current state.It is expected that this ringdown
radiation will be composed primarily of Kerr quasinormal modes, and thereby
enable tests of general relativity.Here, the first complete ringdown signal
model for nonprecessing binary black hole systems is presented: multipole
amplitudes and phases are modeled as functions of initial binary parameters. It
is found that using the peak time of the dominant merger multipole as a
reference results in the dominant mode's excitation being a remarkably simple
linear function of system parameters, strongly suggesting that an analytic
treatment may be within reach.In particular, for initially nonspinning black
holes, the dominant quadrupole is excited as -4 times the system's symmetric
mass ratio.Application of the model to parameter estimation allows general
relativity predictions for mode amplitudes independently of signal
strength.Treatment of GW150914 indicates some mode amplitudes and relative
phases are intrinsically difficult to constrain.
| [
{
"created": "Wed, 24 Jan 2018 21:37:28 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Oct 2020 00:44:31 GMT",
"version": "v2"
}
] | 2020-10-28 | [
[
"London",
"L.",
""
]
] | The aftermath of binary black hole coalescence is a perturbed remnant whose gravitational radiation rings down, encoding information about the new black hole's recent history and current state.It is expected that this ringdown radiation will be composed primarily of Kerr quasinormal modes, and thereby enable tests of general relativity.Here, the first complete ringdown signal model for nonprecessing binary black hole systems is presented: multipole amplitudes and phases are modeled as functions of initial binary parameters. It is found that using the peak time of the dominant merger multipole as a reference results in the dominant mode's excitation being a remarkably simple linear function of system parameters, strongly suggesting that an analytic treatment may be within reach.In particular, for initially nonspinning black holes, the dominant quadrupole is excited as -4 times the system's symmetric mass ratio.Application of the model to parameter estimation allows general relativity predictions for mode amplitudes independently of signal strength.Treatment of GW150914 indicates some mode amplitudes and relative phases are intrinsically difficult to constrain. |
2108.13361 | Daine Danielson | Daine L. Danielson, Gautam Satishchandran, Robert M. Wald, Robert J.
Weinbaum | Bl\'azquez-Salcedo-Knoll-Radu Wormholes Are Not Solutions to the
Einstein-Dirac-Maxwell Equations | 12 pages, no figures | Phys. Rev. D 104, 124055 (2021) | 10.1103/PhysRevD.104.124055 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, Bl\'azquez-Salcedo, Knoll, and Radu (BSKR) have given a class of
static, spherically symmetric, traversable wormhole spacetimes with Dirac and
Maxwell fields. The BSKR wormholes are obtained by joining a classical solution
to the Einstein-Dirac-Maxwell (EDM) equations on the "up" side of the wormhole
($r \geq 0$) to a corresponding solution on the "down" side of the wormhole ($r
\leq 0$). However, it can be seen that the BSKR metric fails to be $C^3$ on the
wormhole throat at $r=0$. We prove that if the matching were done in such a way
that the resulting spacetime metric, Dirac field, and Maxwell field composed a
solution to the EDM equations in a neighborhood of $r=0$, then all of the
fields would be smooth at $r=0$ in a suitable gauge. Thus, the BSKR wormholes
cannot be solutions to the EDM equations. The failure of the BSKR wormholes to
solve the EDM equations arises both from the failure of the Maxwell field to
satisfy the required matching conditions (which implies the presence of an
additional shell of charged matter at $r=0$) and, more significantly, from the
failure of the Dirac field to satisfy required matching conditions (which
implies the presence of a spurious source term for the Dirac field at $r=0$.
| [
{
"created": "Mon, 30 Aug 2021 16:33:46 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Dec 2021 21:18:53 GMT",
"version": "v2"
}
] | 2021-12-21 | [
[
"Danielson",
"Daine L.",
""
],
[
"Satishchandran",
"Gautam",
""
],
[
"Wald",
"Robert M.",
""
],
[
"Weinbaum",
"Robert J.",
""
]
] | Recently, Bl\'azquez-Salcedo, Knoll, and Radu (BSKR) have given a class of static, spherically symmetric, traversable wormhole spacetimes with Dirac and Maxwell fields. The BSKR wormholes are obtained by joining a classical solution to the Einstein-Dirac-Maxwell (EDM) equations on the "up" side of the wormhole ($r \geq 0$) to a corresponding solution on the "down" side of the wormhole ($r \leq 0$). However, it can be seen that the BSKR metric fails to be $C^3$ on the wormhole throat at $r=0$. We prove that if the matching were done in such a way that the resulting spacetime metric, Dirac field, and Maxwell field composed a solution to the EDM equations in a neighborhood of $r=0$, then all of the fields would be smooth at $r=0$ in a suitable gauge. Thus, the BSKR wormholes cannot be solutions to the EDM equations. The failure of the BSKR wormholes to solve the EDM equations arises both from the failure of the Maxwell field to satisfy the required matching conditions (which implies the presence of an additional shell of charged matter at $r=0$) and, more significantly, from the failure of the Dirac field to satisfy required matching conditions (which implies the presence of a spurious source term for the Dirac field at $r=0$. |
1501.04003 | Surajit Chattopadhyay | Ines G. Salako, Abdul Jawad, Surajit Chattopadhyay | Holographic dark energy reconstruction of $f(T,\mathcal{T})$ gravity | 14 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper reports a holographic reconstruction scheme for
$f(T,\mathcal T)$ gravity proposed in Harko et al. $\emph{JCAP}\; 12(2014)021$
where $T$ is the torsion scalar and $\mathcal{T}$ is the trace of the
energy-momentum tensor considering future event horizon as the enveloping
horizon of the universe. We have considered $f(T, \mathcal T)=T + \gamma
g(\mathcal T)$ and $f(T,\mathcal T) =\beta \mathcal T + g(T)$ for
reconstruction. We observe that the derived $f(T,\mathcal T)$ models can
represent phantom or quintessence regimes of the universe which are compatible
with the current observational data.
| [
{
"created": "Tue, 6 Jan 2015 09:56:30 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Feb 2015 07:24:06 GMT",
"version": "v2"
}
] | 2015-02-23 | [
[
"Salako",
"Ines G.",
""
],
[
"Jawad",
"Abdul",
""
],
[
"Chattopadhyay",
"Surajit",
""
]
] | The present paper reports a holographic reconstruction scheme for $f(T,\mathcal T)$ gravity proposed in Harko et al. $\emph{JCAP}\; 12(2014)021$ where $T$ is the torsion scalar and $\mathcal{T}$ is the trace of the energy-momentum tensor considering future event horizon as the enveloping horizon of the universe. We have considered $f(T, \mathcal T)=T + \gamma g(\mathcal T)$ and $f(T,\mathcal T) =\beta \mathcal T + g(T)$ for reconstruction. We observe that the derived $f(T,\mathcal T)$ models can represent phantom or quintessence regimes of the universe which are compatible with the current observational data. |
1410.6678 | Anzhong Wang | Kai Lin, O. Goldoni, M.F. da Silva, and Anzhong Wang | New look at black holes: Existence of universal horizons | revtex4, 17 figures. Version appeared in Phys. Rev. D91, 024047
(2015) | Phys. Rev. D 91, 024047 (2015) | 10.1103/PhysRevD.91.024047 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the existence of universal horizons in a given static
spacetime, and find that the test khronon field can be solved explicitly when
its velocity becomes infinitely large, at which point the universal horizon
coincides with the sound horizon of the khronon. Choosing the timelike
coordinate aligned with the khronon, the static metric takes a simple form,
from which it can be seen clearly that the metric is free of singularity at the
Killing horizon, but becomes singular at the universal horizon. Applying such
developed formulas to three well-known black hole solutions, the Schwarzschild,
Schwarzschild anti-de Sitter, and Reissner-Nordstr\"om, we find that in all
these solutions universal horizons exist and are always inside the Killing
horizons. In particular, in the Eddington-Finkelstein and Painleve-Gullstrand
coordinates, in which the metrics are not singular when crossing both of the
Killing and universal horizons, the peeling-off behavior of the khronon is
found only at the universal horizons, whereby we show that the values of
surface gravity of the universal horizons calculated from the peeling-off
behavior of the khronon match with those obtained from the covariant definition
given recently by Cropp, Liberati, Mohd and Visser.
| [
{
"created": "Thu, 23 Oct 2014 16:21:29 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jan 2015 03:10:17 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Feb 2015 14:20:44 GMT",
"version": "v3"
}
] | 2015-03-05 | [
[
"Lin",
"Kai",
""
],
[
"Goldoni",
"O.",
""
],
[
"da Silva",
"M. F.",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this paper, we study the existence of universal horizons in a given static spacetime, and find that the test khronon field can be solved explicitly when its velocity becomes infinitely large, at which point the universal horizon coincides with the sound horizon of the khronon. Choosing the timelike coordinate aligned with the khronon, the static metric takes a simple form, from which it can be seen clearly that the metric is free of singularity at the Killing horizon, but becomes singular at the universal horizon. Applying such developed formulas to three well-known black hole solutions, the Schwarzschild, Schwarzschild anti-de Sitter, and Reissner-Nordstr\"om, we find that in all these solutions universal horizons exist and are always inside the Killing horizons. In particular, in the Eddington-Finkelstein and Painleve-Gullstrand coordinates, in which the metrics are not singular when crossing both of the Killing and universal horizons, the peeling-off behavior of the khronon is found only at the universal horizons, whereby we show that the values of surface gravity of the universal horizons calculated from the peeling-off behavior of the khronon match with those obtained from the covariant definition given recently by Cropp, Liberati, Mohd and Visser. |
1908.05442 | Michalis Agathos | Michalis Agathos, Francesco Zappa, Sebastiano Bernuzzi, Albino Perego,
Matteo Breschi and David Radice | Inferring prompt black-hole formation in neutron star mergers from
gravitational-wave data | 14 pages, 14 figures | Phys. Rev. D 101, 044006 (2020) | 10.1103/PhysRevD.101.044006 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational-wave GW170817 is associated to the inspiral phase of a
binary neutron star coalescence event. The LIGO-Virgo detectors sensitivity at
high frequencies was not sufficient to detect the signal corresponding to the
merger and post-merger phases. Hence, the question whether the merger outcome
was a prompt black hole formation or not must be answered using either the
pre-merger gravitational wave signal or electromagnetic counterparts. In this
work we present two methods to infer the probability of prompt black hole
formation, using the analysis of the inspiral gravitational-wave signal. Both
methods combine the posterior distribution from the gravitational-wave data
analysis with numerical relativity results. One method relies on the use of
phenomenological models for the equation of state and on the estimate of the
collapse threshold mass. The other is based on the estimate of the tidal
polarizability parameter $\tilde{\Lambda}$ that is correlated in an
equation-of-state agnostic way with the prompt BH formation. We analyze
GW170817 data and find that the two methods consistently predict a probability
of ~ 50-70% for prompt black-hole formation, which however may significantly
decrease below 10% if the maximum mass constraint from PSR J0348+0432 or PSR
J0740+6620 is imposed.
| [
{
"created": "Thu, 15 Aug 2019 07:00:45 GMT",
"version": "v1"
}
] | 2020-02-12 | [
[
"Agathos",
"Michalis",
""
],
[
"Zappa",
"Francesco",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Perego",
"Albino",
""
],
[
"Breschi",
"Matteo",
""
],
[
"Radice",
"David",
""
]
] | The gravitational-wave GW170817 is associated to the inspiral phase of a binary neutron star coalescence event. The LIGO-Virgo detectors sensitivity at high frequencies was not sufficient to detect the signal corresponding to the merger and post-merger phases. Hence, the question whether the merger outcome was a prompt black hole formation or not must be answered using either the pre-merger gravitational wave signal or electromagnetic counterparts. In this work we present two methods to infer the probability of prompt black hole formation, using the analysis of the inspiral gravitational-wave signal. Both methods combine the posterior distribution from the gravitational-wave data analysis with numerical relativity results. One method relies on the use of phenomenological models for the equation of state and on the estimate of the collapse threshold mass. The other is based on the estimate of the tidal polarizability parameter $\tilde{\Lambda}$ that is correlated in an equation-of-state agnostic way with the prompt BH formation. We analyze GW170817 data and find that the two methods consistently predict a probability of ~ 50-70% for prompt black-hole formation, which however may significantly decrease below 10% if the maximum mass constraint from PSR J0348+0432 or PSR J0740+6620 is imposed. |
2212.09407 | Vishwa Vijay Singh | Vishwa Vijay Singh and J\"urgen M\"uller and Liliane Biskupek and Eva
Hackmann and Claus L\"ammerzahl | Equivalence of Active and Passive Gravitational Mass Tested with Lunar
Laser Ranging | 4 pages, 1 figure | null | 10.1103/PhysRevLett.131.021401 | null | gr-qc astro-ph.EP physics.space-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | LLR measures the distance between observatories on Earth and retro-reflectors
on Moon since 1969. In this paper, we study the possible violation of the
equality of passive and active gravitational mass ($m_{a}/m_{p}$), for
Aluminium (Al) and Iron (Fe), using LLR data. Our new limit of
$3.9\cdot10^{-14}$ is about 100 times better than that of Bartlett and Van
Buren [1986] reflecting the benefit of the many years of LLR data.
| [
{
"created": "Mon, 19 Dec 2022 12:37:40 GMT",
"version": "v1"
}
] | 2023-07-17 | [
[
"Singh",
"Vishwa Vijay",
""
],
[
"Müller",
"Jürgen",
""
],
[
"Biskupek",
"Liliane",
""
],
[
"Hackmann",
"Eva",
""
],
[
"Lämmerzahl",
"Claus",
""
]
] | LLR measures the distance between observatories on Earth and retro-reflectors on Moon since 1969. In this paper, we study the possible violation of the equality of passive and active gravitational mass ($m_{a}/m_{p}$), for Aluminium (Al) and Iron (Fe), using LLR data. Our new limit of $3.9\cdot10^{-14}$ is about 100 times better than that of Bartlett and Van Buren [1986] reflecting the benefit of the many years of LLR data. |
2111.07207 | Michael Efroimsky | Pini Gurfil and Michael Efroimsky | Analysis of the PPN Two-Body Problem Using Non-Osculating Orbital
Elements | null | null | 10.1016/j.asr.2021.09.009 | null | gr-qc astro-ph.EP math.DS | http://creativecommons.org/licenses/by-sa/4.0/ | The parameterised post-Newtonian (PPN) formalism is a weak-field slow-motion
approximation for both GR and some of its generalisations. It permits various
parameterisations of the motion, among which are the Lagrange-type and
Gauss-type orbital equations. Often, these equations are developed under the
Lagrange constraint, which makes the evolving orbital elements parameterise
instantaneous conics tangent to the orbit. Arbitrary mathematically, this
choice of a constraint is convenient under perturbations dependent only on
positions. Under perturbations dependent also on velocities (like relativistic
corrections) the Lagrange constraint unnecessarily complicates solutions that
can be simplified by introducing a freedom in the orbit parameterisation, which
is analogous to the gauge freedom in electrodynamics and gauge theories.
Geometrically, this freedom is the freedom of nonosculation, i.e. of the degree
to which the instantaneous conics are permitted to be non-tangent to the actual
orbit. Under the same perturbation, all solutions with different degree of
nonosculation look mathematically different, though describe the same physical
orbit. While non-intuitive, the modeling of an orbit with a sequence of
nontangent instantaneous conics can at times simplify calculations. The
appropriately generalised ("gauge-generalised") Lagrange-type equations, and
their applications, appeared in the literature hitherto. We in this paper
derive the gauge-generalised Gauss-type equations and apply them to the PPN
two-body problem. Fixing the gauge freedom in three different ways (i.e.
modeling an orbit with non-osculating elements of three different types) we
find three parameterisations of the PPN two-body dynamics. These
parameterisations render orbits with either a fixed non-osculating semimajor
axis, or a fixed non-osculating eccentricity, or a fixed non-osculating
argument of periastron.
| [
{
"created": "Sat, 13 Nov 2021 23:16:48 GMT",
"version": "v1"
}
] | 2021-11-16 | [
[
"Gurfil",
"Pini",
""
],
[
"Efroimsky",
"Michael",
""
]
] | The parameterised post-Newtonian (PPN) formalism is a weak-field slow-motion approximation for both GR and some of its generalisations. It permits various parameterisations of the motion, among which are the Lagrange-type and Gauss-type orbital equations. Often, these equations are developed under the Lagrange constraint, which makes the evolving orbital elements parameterise instantaneous conics tangent to the orbit. Arbitrary mathematically, this choice of a constraint is convenient under perturbations dependent only on positions. Under perturbations dependent also on velocities (like relativistic corrections) the Lagrange constraint unnecessarily complicates solutions that can be simplified by introducing a freedom in the orbit parameterisation, which is analogous to the gauge freedom in electrodynamics and gauge theories. Geometrically, this freedom is the freedom of nonosculation, i.e. of the degree to which the instantaneous conics are permitted to be non-tangent to the actual orbit. Under the same perturbation, all solutions with different degree of nonosculation look mathematically different, though describe the same physical orbit. While non-intuitive, the modeling of an orbit with a sequence of nontangent instantaneous conics can at times simplify calculations. The appropriately generalised ("gauge-generalised") Lagrange-type equations, and their applications, appeared in the literature hitherto. We in this paper derive the gauge-generalised Gauss-type equations and apply them to the PPN two-body problem. Fixing the gauge freedom in three different ways (i.e. modeling an orbit with non-osculating elements of three different types) we find three parameterisations of the PPN two-body dynamics. These parameterisations render orbits with either a fixed non-osculating semimajor axis, or a fixed non-osculating eccentricity, or a fixed non-osculating argument of periastron. |
1510.04010 | Puxun Wu | Yize Fan, Puxun Wu and Hongwei Yu | Spherical collapse in the extended quintessence cosmological models | 17 pages, 4 figures. References added | Physical Review D 92, 083529 (2015) | 10.1103/PhysRevD.92.083529 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the spherical collapse method to investigate the non-linear density
perturbations of pressureless matter in the cosmological models with the
extended quintessence as dark energy in the metric and Palatini formalisms. We
find that for both formalisms, when the coupling constant is negative, the
deviation from the $\Lambda$CDM model is the least according to the
evolutionary curves of the linear density contrast $\delta_{c}$ and virial
overdensity $\Delta_{v}$, and it is less than one percent. And this indicates
that, in the extended quintessence cosmological models in which the coupling
constant is negative, all quantities dependent on $\delta_{c}$ or $\Delta_{v}$
are essentially unaffected if the linear density contrast or the virial
overdensity of the $\Lambda$CDM model is used as an approximation. Moreover, we
find that the differences between different formalisms are very small in terms
of structure formation, and thus can not be used to distinguish the metric and
Palatini formalisms.
| [
{
"created": "Wed, 14 Oct 2015 09:02:05 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Nov 2015 15:15:20 GMT",
"version": "v2"
}
] | 2015-11-09 | [
[
"Fan",
"Yize",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | We use the spherical collapse method to investigate the non-linear density perturbations of pressureless matter in the cosmological models with the extended quintessence as dark energy in the metric and Palatini formalisms. We find that for both formalisms, when the coupling constant is negative, the deviation from the $\Lambda$CDM model is the least according to the evolutionary curves of the linear density contrast $\delta_{c}$ and virial overdensity $\Delta_{v}$, and it is less than one percent. And this indicates that, in the extended quintessence cosmological models in which the coupling constant is negative, all quantities dependent on $\delta_{c}$ or $\Delta_{v}$ are essentially unaffected if the linear density contrast or the virial overdensity of the $\Lambda$CDM model is used as an approximation. Moreover, we find that the differences between different formalisms are very small in terms of structure formation, and thus can not be used to distinguish the metric and Palatini formalisms. |
2112.04065 | Erik Jimenez | Erik Jim\'enez-V\'azquez, Miguel Alcubierre | Critical gravitational collapse of a non-minimally coupled scalar field | null | null | 10.1103/PhysRevD.105.064071 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the critical gravitational collapse of a massless scalar field
non-minimally coupled to gravity, using a quadratic coupling function with a
strength parameter $\xi$. We concentrate on critical phenomena of type II, and
determine with an accuracy of at least $10^{-12}$ the value of the critical
amplitude for collapse to a black hole, as well as the values of the critical
and echoing exponents. Obtaining such high accuracy in the critical amplitude
requires us to do a coordinate radial transformation that effectively increases
resolution near the central regions by a factor of at least $10^3$. As
expected, we find that for the case of small coupling the critical behaviour is
very similar to that of a minimally coupled scalar field. On the other hand,
for high coupling the dynamics become so violent that we need to introduce a
special slicing condition, known as the shock-avoiding slicing condition, in
order to avoid gauge pathologies that would otherwise cause our simulations to
fail. With this new gauge condition we are able to perform high accuracy
simulations even in the strong coupling regime, where we find that the critical
and echoing exponents become significantly smaller, and that the echoing
behavior is richer and can not be modelled by a single harmonic.
| [
{
"created": "Wed, 8 Dec 2021 01:07:45 GMT",
"version": "v1"
}
] | 2022-04-13 | [
[
"Jiménez-Vázquez",
"Erik",
""
],
[
"Alcubierre",
"Miguel",
""
]
] | We study the critical gravitational collapse of a massless scalar field non-minimally coupled to gravity, using a quadratic coupling function with a strength parameter $\xi$. We concentrate on critical phenomena of type II, and determine with an accuracy of at least $10^{-12}$ the value of the critical amplitude for collapse to a black hole, as well as the values of the critical and echoing exponents. Obtaining such high accuracy in the critical amplitude requires us to do a coordinate radial transformation that effectively increases resolution near the central regions by a factor of at least $10^3$. As expected, we find that for the case of small coupling the critical behaviour is very similar to that of a minimally coupled scalar field. On the other hand, for high coupling the dynamics become so violent that we need to introduce a special slicing condition, known as the shock-avoiding slicing condition, in order to avoid gauge pathologies that would otherwise cause our simulations to fail. With this new gauge condition we are able to perform high accuracy simulations even in the strong coupling regime, where we find that the critical and echoing exponents become significantly smaller, and that the echoing behavior is richer and can not be modelled by a single harmonic. |
1006.2609 | Ujjal Debnath | Samarpita Bhattacharya and Ujjal Debnath | Brans-Dicke Theory and Thermodynamical Laws on Apparent and Event
Horizons | 6 pages, 2 figures | null | 10.1139/p11-072 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have described the Brans-Dicke theory of gravity and given a
particular solution by choosing a power law form of scalar field $\phi$ and
constant $\omega$. If we assume first law and entropy formula on apparent
horizon then we recover Friedmann equations. Next, assuming first law of
thermodynamics, the validity conditions of GSL on event horizon are presented.
Also without use first law, if we impose the entropy relation on the horizon,
then we also obtain the condition of validity of GSL on event horizon. The
validity of GSL completely depends on the model of BD scalar field solutions.
We have justified that on the apparent horizon the two process are equivalent,
but on the event horizon they are not equivalent. If first law is valid on the
event horizon then GSL may be satisfied in BD solution, but if first law is not
satisfied then GSL is not satisfied in BD solution. So first law always favours
GSL on event horizon. In our effective approach, the first law and GSL is
always satisfied in apparent horizon, which do not depend on BD theory of
gravity.
| [
{
"created": "Mon, 14 Jun 2010 06:58:47 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Bhattacharya",
"Samarpita",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this work, we have described the Brans-Dicke theory of gravity and given a particular solution by choosing a power law form of scalar field $\phi$ and constant $\omega$. If we assume first law and entropy formula on apparent horizon then we recover Friedmann equations. Next, assuming first law of thermodynamics, the validity conditions of GSL on event horizon are presented. Also without use first law, if we impose the entropy relation on the horizon, then we also obtain the condition of validity of GSL on event horizon. The validity of GSL completely depends on the model of BD scalar field solutions. We have justified that on the apparent horizon the two process are equivalent, but on the event horizon they are not equivalent. If first law is valid on the event horizon then GSL may be satisfied in BD solution, but if first law is not satisfied then GSL is not satisfied in BD solution. So first law always favours GSL on event horizon. In our effective approach, the first law and GSL is always satisfied in apparent horizon, which do not depend on BD theory of gravity. |
1707.09309 | Ryuichi Fujita | Ryuichi Fujita, Norichika Sago, Hiroyuki Nakano | Note on Accuracy of the Post-Newtonian Approximation for Extreme-Mass
Ratio Inspirals: Retrograde Orbits | 10 pages, 3 figures | Class. Quantum Grav. 35 027001 (2018) | 10.1088/1361-6382/aa9ad5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The post-Newtonian approximation is useful to discuss gravitational waveforms
for binary inspirals. In this note, for retrograde circular orbits in the
equatorial plane, we discuss the region of validity of the post-Newtonian
approximation by using the gravitational energy flux derived numerically and
analytically in the black hole perturbation approach. It is found that the edge
of the allowable region behaves quite intricately, including prograde orbits
even if we treat higher post-Newtonian orders.
| [
{
"created": "Fri, 28 Jul 2017 16:24:27 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Dec 2017 07:58:05 GMT",
"version": "v2"
}
] | 2017-12-22 | [
[
"Fujita",
"Ryuichi",
""
],
[
"Sago",
"Norichika",
""
],
[
"Nakano",
"Hiroyuki",
""
]
] | The post-Newtonian approximation is useful to discuss gravitational waveforms for binary inspirals. In this note, for retrograde circular orbits in the equatorial plane, we discuss the region of validity of the post-Newtonian approximation by using the gravitational energy flux derived numerically and analytically in the black hole perturbation approach. It is found that the edge of the allowable region behaves quite intricately, including prograde orbits even if we treat higher post-Newtonian orders. |
gr-qc/9805088 | Bozhidar Zakhariev Iliev | Bozhidar Z. Iliev (Institute for Nuclear Research and Nuclear Energy,
Bulgarian Academy of Sciences, Sofia, Bulgaria) | Normal frames and the validity of the equivalence principle. III. The
case along smooth maps with separable points of self-intersection | 15 standard LaTeX 2e (11pt, A4) pages. The package amsfonts is
required | J.Phys.A31:1287-1296,1998 | 10.1088/0305-4470/31/4/016 | JINR Communication E5-92-543, Dubna, 1992 | gr-qc | null | The equivalence principle is treated on a mathematically rigorous base on
sufficiently general subsets of a differentiable manifold. This is carried out
using the basis of derivations of the tensor algebra over that manifold.
Necessary and/or sufficient conditions of existence, uniqueness, and
holonomicity of these bases in which the components of the derivations of the
tensor algebra over it vanish on these subsets, are studied. The linear
connections are considered in this context. It is shown that the equivalence
principle is identically valid at any point, and along any path, in every
gravitational theory based on linear connections. On higher dimensional
submanifolds it may be valid only in certain exceptional cases.
| [
{
"created": "Fri, 22 May 1998 15:31:23 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Iliev",
"Bozhidar Z.",
"",
"Institute for Nuclear Research and Nuclear Energy,\n Bulgarian Academy of Sciences, Sofia, Bulgaria"
]
] | The equivalence principle is treated on a mathematically rigorous base on sufficiently general subsets of a differentiable manifold. This is carried out using the basis of derivations of the tensor algebra over that manifold. Necessary and/or sufficient conditions of existence, uniqueness, and holonomicity of these bases in which the components of the derivations of the tensor algebra over it vanish on these subsets, are studied. The linear connections are considered in this context. It is shown that the equivalence principle is identically valid at any point, and along any path, in every gravitational theory based on linear connections. On higher dimensional submanifolds it may be valid only in certain exceptional cases. |
gr-qc/9905062 | Maurizio Gasperini | M. Gasperini | Looking back in time beyond the big bang | 11 pages, Latex, four figures included using epsfig. Essay written
for the 1999 Awards of the Gravity Research Foundation (Wellesley Hills, Ma,
02481-0004), and selected for Honorable Mention. To appear in Mod. Phys.
Lett. A | Mod.Phys.Lett. A14 (1999) 1059-1066 | 10.1142/S0217732399001127 | BARI-TH/99-331 | gr-qc | null | String theory can (in principle) describe gravity at all curvature scales,
and can be applied to cosmology to look back in time beyond the Planck epoch.
The duality symmetries of string theory suggest a cosmological picture in which
the imprint of a primordial, pre-big bang phase could still be accessible to
present observations. The predictive power of such a scenario relies, however,
on our ability to connect in a smooth way the pre-big bang to the present
cosmological regime. Classical radiation back reaction seems to play a key role
to this purpose, by isotropizing and turning into a final expansion any state
of anisotropic contraction possibly emerging from the pre-big bang at the
string scale.
| [
{
"created": "Tue, 18 May 1999 13:35:55 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gasperini",
"M.",
""
]
] | String theory can (in principle) describe gravity at all curvature scales, and can be applied to cosmology to look back in time beyond the Planck epoch. The duality symmetries of string theory suggest a cosmological picture in which the imprint of a primordial, pre-big bang phase could still be accessible to present observations. The predictive power of such a scenario relies, however, on our ability to connect in a smooth way the pre-big bang to the present cosmological regime. Classical radiation back reaction seems to play a key role to this purpose, by isotropizing and turning into a final expansion any state of anisotropic contraction possibly emerging from the pre-big bang at the string scale. |
1302.2646 | Paolo Pani | Caio F.B. Macedo, Paolo Pani, Vitor Cardoso, Luis C.B. Crispino | Into the lair: gravitational-wave signatures of dark matter | 17 pages, 6 figures. Abstract abridged. v2: Sections 1 and 2
improved. Version to be published in the ApJ | null | 10.1088/0004-637X/774/1/48 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nature and properties of dark matter (DM) are both outstanding issues in
physics. Besides clustering in halos, the universal character of gravity
implies that self-gravitating compact DM configurations might be spread
throughout the universe. The astrophysical signature of these objects may be
used to probe fundamental particle physics, or even to provide an alternative
description of compact objects in active galactic nuclei. Here we discuss the
most promising dissection tool of these configurations: the inspiral of a
compact stellar-size object and consequent gravitational-wave emission. The
inward motion of this "test probe" encodes unique information about the nature
of the central, supermassive DM configuration. When the probe travels through
some compact DM profile we show that, within a Newtonian approximation, the
quasi-adiabatic evolution of the inspiral is mainly driven by DM accretion into
the small compact object and by dynamical friction, rather than by
gravitational-wave radiation-reaction. These effects circularize the orbits and
leave a peculiar imprint on the gravitational waves emitted at late time. When
accretion dominates, the frequency and the amplitude of the gravitational-wave
signal produced during the latest stages of the inspiral are nearly constant.
In the exterior region we study a relativistic model in which the inspiral is
driven by the emission of gravitational and scalar waves. Resonances in the
energy flux appear whenever the orbital frequency matches the mass of the DM
particle and they correspond to the excitation of the central object's
quasinormal frequencies. Unexpectedly, these resonances can lead to large
dephasing with respect to standard inspiral templates, to such an extent as to
prevent detection with matched filtering techniques. We discuss some
observational consequences of these effects for gravitational-wave detection.
| [
{
"created": "Mon, 11 Feb 2013 21:15:01 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2013 14:52:50 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Macedo",
"Caio F. B.",
""
],
[
"Pani",
"Paolo",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Crispino",
"Luis C. B.",
""
]
] | The nature and properties of dark matter (DM) are both outstanding issues in physics. Besides clustering in halos, the universal character of gravity implies that self-gravitating compact DM configurations might be spread throughout the universe. The astrophysical signature of these objects may be used to probe fundamental particle physics, or even to provide an alternative description of compact objects in active galactic nuclei. Here we discuss the most promising dissection tool of these configurations: the inspiral of a compact stellar-size object and consequent gravitational-wave emission. The inward motion of this "test probe" encodes unique information about the nature of the central, supermassive DM configuration. When the probe travels through some compact DM profile we show that, within a Newtonian approximation, the quasi-adiabatic evolution of the inspiral is mainly driven by DM accretion into the small compact object and by dynamical friction, rather than by gravitational-wave radiation-reaction. These effects circularize the orbits and leave a peculiar imprint on the gravitational waves emitted at late time. When accretion dominates, the frequency and the amplitude of the gravitational-wave signal produced during the latest stages of the inspiral are nearly constant. In the exterior region we study a relativistic model in which the inspiral is driven by the emission of gravitational and scalar waves. Resonances in the energy flux appear whenever the orbital frequency matches the mass of the DM particle and they correspond to the excitation of the central object's quasinormal frequencies. Unexpectedly, these resonances can lead to large dephasing with respect to standard inspiral templates, to such an extent as to prevent detection with matched filtering techniques. We discuss some observational consequences of these effects for gravitational-wave detection. |
2001.09082 | Alessandro Nagar | Alessandro Nagar, Gunnar Riemenschneider, Geraint Pratten, Piero
Rettegno and Francesco Messina | A multipolar effective one body waveform model for spin-aligned black
hole binaries | 45 pages, 21 figures, several changes with respect to the earlier
version. Matches published version | Phys. Rev. D 102, 024077 (2020) | 10.1103/PhysRevD.102.024077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce \TEOBiResumSM{}, an improved version of the effective-one-body
(EOB) waveform model \TEOBResumS{} for spin-aligned, coalescing black hole
binaries, that includes subdominant gravitational waveform modes completed
through merger and ringdown. Beyond the dominant $(\ell,|m|)=(2,2)$ one, the
more robust multipoles all over the parameter space are: $(2,1)$, $(3,3)$,
$(3,2)$, $(4,4)$ and $(5,5)$. The multipolar ringdown EOB waveform stems from
suitably fitting many numerical relativity (NR) waveform data from the
Simulating eXtreme Spacetimes (SXS) collaboration together with test-mass
waveform data. Mode-mixing effects are not incorporated. The orbital
(nonspinning) part of the multipolar waveform amplitudes includes test-mass
results up to (relative) 6PN order and, for most modes,is Pad\'e resummed. The
$m$=odd waveform multipoles (up to $\ell=5$) incorporate most of the currently
available spin-dependent analytical information. Improving on previous work, we
confirm that certain $m=\text{odd}$ modes, e.g. the $(2,1)$, and even the
$(3,1)$, may develop a zero (or a minimum) in the amplitude for nearly
equal-mass binaries and for several combinations of the individual spins. A
remarkable EOB/NR agreement around such zero is found for these modes. The new
waveform, and radiation reaction, prompts a new NR-calibration of the spinning
sector of the model, done with only $32$ datasets.The maximum $(2,2)$ EOB/NR
unfaithfulness $\bar{F}$ with Advanced LIGO noise against the SXS catalog
($\sim 595$ datasets) is always below $0.5\%$ for binaries with total mass $M$
as $10M_\odot\leq M \leq 200M_\odot$, except for a single outlier with
$\max{(\bar{F})}\sim 0.85\%$. When $(2,1)$, $(3,3)$ and $(4,4)$ modes are
included, one finds an excellent EOB/NR agreement up to $M\sim 120M_\odot$,
above which the performance degrades slightly and moves above $3\%$
| [
{
"created": "Fri, 24 Jan 2020 16:44:24 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Sep 2020 09:53:17 GMT",
"version": "v2"
}
] | 2020-09-15 | [
[
"Nagar",
"Alessandro",
""
],
[
"Riemenschneider",
"Gunnar",
""
],
[
"Pratten",
"Geraint",
""
],
[
"Rettegno",
"Piero",
""
],
[
"Messina",
"Francesco",
""
]
] | We introduce \TEOBiResumSM{}, an improved version of the effective-one-body (EOB) waveform model \TEOBResumS{} for spin-aligned, coalescing black hole binaries, that includes subdominant gravitational waveform modes completed through merger and ringdown. Beyond the dominant $(\ell,|m|)=(2,2)$ one, the more robust multipoles all over the parameter space are: $(2,1)$, $(3,3)$, $(3,2)$, $(4,4)$ and $(5,5)$. The multipolar ringdown EOB waveform stems from suitably fitting many numerical relativity (NR) waveform data from the Simulating eXtreme Spacetimes (SXS) collaboration together with test-mass waveform data. Mode-mixing effects are not incorporated. The orbital (nonspinning) part of the multipolar waveform amplitudes includes test-mass results up to (relative) 6PN order and, for most modes,is Pad\'e resummed. The $m$=odd waveform multipoles (up to $\ell=5$) incorporate most of the currently available spin-dependent analytical information. Improving on previous work, we confirm that certain $m=\text{odd}$ modes, e.g. the $(2,1)$, and even the $(3,1)$, may develop a zero (or a minimum) in the amplitude for nearly equal-mass binaries and for several combinations of the individual spins. A remarkable EOB/NR agreement around such zero is found for these modes. The new waveform, and radiation reaction, prompts a new NR-calibration of the spinning sector of the model, done with only $32$ datasets.The maximum $(2,2)$ EOB/NR unfaithfulness $\bar{F}$ with Advanced LIGO noise against the SXS catalog ($\sim 595$ datasets) is always below $0.5\%$ for binaries with total mass $M$ as $10M_\odot\leq M \leq 200M_\odot$, except for a single outlier with $\max{(\bar{F})}\sim 0.85\%$. When $(2,1)$, $(3,3)$ and $(4,4)$ modes are included, one finds an excellent EOB/NR agreement up to $M\sim 120M_\odot$, above which the performance degrades slightly and moves above $3\%$ |
1001.5429 | Jose Luis Jaramillo | J.L. Jaramillo, E. Gourgoulhon | Mass and Angular Momentum in General Relativity | 41 pages. Notes based on the lecture given at the C.N.R.S. "School on
Mass" (June 2008) in Orleans, France. To appear as proceedings in the book
"Mass and Motion in General Relativity", eds. L. Blanchet, A. Spallicci and
B. Whiting. Some comments and references added. | null | 10.1007/978-90-481-3015-3_4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an introduction to mass and angular momentum in General
Relativity. After briefly reviewing energy-momentum for matter fields, first in
the flat Minkowski case (Special Relativity) and then in curved spacetimes with
or without symmetries, we focus on the discussion of energy-momentum for the
gravitational field. We illustrate the difficulties rooted in the Equivalence
Principle for defining a local energy-momentum density for the gravitational
field. This leads to the understanding of gravitational energy-momentum and
angular momentum as non-local observables that make sense, at best, for
extended domains of spacetime. After introducing Komar quantities associated
with spacetime symmetries, it is shown how total energy-momentum can be
unambiguously defined for isolated systems, providing fundamental tests for the
internal consistency of General Relativity as well as setting the conceptual
basis for the understanding of energy loss by gravitational radiation. Finally,
several attempts to formulate quasi-local notions of mass and angular momentum
associated with extended but finite spacetime domains are presented, together
with some illustrations of the relations between total and quasi-local
quantities in the particular context of black hole spacetimes. This article is
not intended to be a rigorous and exhaustive review of the subject, but rather
an invitation to the topic for non-experts. In this sense we follow essentially
the expositions in Szabados 2004, Gourgoulhon 2007, Poisson 2004 and Wald 84,
and refer the reader interested in further developments to the existing
literature, in particular to the excellent and comprehensive review by Szabados
(2004).
| [
{
"created": "Fri, 29 Jan 2010 16:26:37 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Apr 2010 08:30:01 GMT",
"version": "v2"
}
] | 2015-05-18 | [
[
"Jaramillo",
"J. L.",
""
],
[
"Gourgoulhon",
"E.",
""
]
] | We present an introduction to mass and angular momentum in General Relativity. After briefly reviewing energy-momentum for matter fields, first in the flat Minkowski case (Special Relativity) and then in curved spacetimes with or without symmetries, we focus on the discussion of energy-momentum for the gravitational field. We illustrate the difficulties rooted in the Equivalence Principle for defining a local energy-momentum density for the gravitational field. This leads to the understanding of gravitational energy-momentum and angular momentum as non-local observables that make sense, at best, for extended domains of spacetime. After introducing Komar quantities associated with spacetime symmetries, it is shown how total energy-momentum can be unambiguously defined for isolated systems, providing fundamental tests for the internal consistency of General Relativity as well as setting the conceptual basis for the understanding of energy loss by gravitational radiation. Finally, several attempts to formulate quasi-local notions of mass and angular momentum associated with extended but finite spacetime domains are presented, together with some illustrations of the relations between total and quasi-local quantities in the particular context of black hole spacetimes. This article is not intended to be a rigorous and exhaustive review of the subject, but rather an invitation to the topic for non-experts. In this sense we follow essentially the expositions in Szabados 2004, Gourgoulhon 2007, Poisson 2004 and Wald 84, and refer the reader interested in further developments to the existing literature, in particular to the excellent and comprehensive review by Szabados (2004). |
2004.05627 | Arunima Banerjee Dr. | K. Aditya, Indrani Banerjee, Arunima Banerjee and Soumitra SenGupta | Dynamical modelling of disc vertical structure in superthin galaxy `UGC
7321' in braneworld gravity: An MCMC study | 20 pages, 2 figures (Accepted for publication in MNRAS) | null | 10.1093/mnras/staa3104 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Low surface brightness (LSBs) superthins constitute classic examples of very
late-type galaxies, with their disc dynamics strongly regulated by their dark
matter halos. In this work we consider a gravitational origin of dark matter in
the brane world scenario, where the higher dimensional Weyl stress term
projected onto the 3-brane acts as the source of dark matter. In the context of
the braneworld model, this dark matter is referred to as the \emph{`dark
mass'}.This model has been successful in reproducing the rotation curves of
several low surface brightness and high surface brightness galaxies. Therefore
it is interesting to study the prospect of this model in explaining the
vertical structure of galaxies which has not been explored in the literature so
far. Using our 2-component model of gravitationally-coupled stars and gas in
the external force field of this \emph{dark mass}, we fit the observed scale
heights of stellar and atomic hydrogen (HI) gas of superthin galaxy `UGC7321'
using the Markov Chain Monte Carlo approach. We find that the observed
scaleheights of `UGC7321' can be successfully modelled in the context of the
braneworld scenario. In addition, the model predicted rotation curve also
matches the observed one. The implications on the model parameters are
discussed.
| [
{
"created": "Sun, 12 Apr 2020 14:57:01 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Sep 2020 10:55:37 GMT",
"version": "v2"
}
] | 2020-10-21 | [
[
"Aditya",
"K.",
""
],
[
"Banerjee",
"Indrani",
""
],
[
"Banerjee",
"Arunima",
""
],
[
"SenGupta",
"Soumitra",
""
]
] | Low surface brightness (LSBs) superthins constitute classic examples of very late-type galaxies, with their disc dynamics strongly regulated by their dark matter halos. In this work we consider a gravitational origin of dark matter in the brane world scenario, where the higher dimensional Weyl stress term projected onto the 3-brane acts as the source of dark matter. In the context of the braneworld model, this dark matter is referred to as the \emph{`dark mass'}.This model has been successful in reproducing the rotation curves of several low surface brightness and high surface brightness galaxies. Therefore it is interesting to study the prospect of this model in explaining the vertical structure of galaxies which has not been explored in the literature so far. Using our 2-component model of gravitationally-coupled stars and gas in the external force field of this \emph{dark mass}, we fit the observed scale heights of stellar and atomic hydrogen (HI) gas of superthin galaxy `UGC7321' using the Markov Chain Monte Carlo approach. We find that the observed scaleheights of `UGC7321' can be successfully modelled in the context of the braneworld scenario. In addition, the model predicted rotation curve also matches the observed one. The implications on the model parameters are discussed. |
2001.03228 | Davide Fermi | Davide Fermi, Massimo Gengo, Livio Pizzocchero (Univ. di Milano) | Integrable scalar cosmologies with matter and curvature | 83 pages, 31 figures. In comparison with version v1, the exposition
of the results has been polished and some references have been added | Nucl. Phys. B 957 (2020), 115095 | 10.1016/j.nuclphysb.2020.115095 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that several integrable (i.e., exactly solvable) scalar cosmologies
considered by Fr\'e, Sagnotti and Sorin (Nuclear Physics \textbf{B 877}(3)
(2013), 1028--1106) can be generalized to include cases where the spatial
curvature is not zero and, besides a scalar field, matter or radiation are
present with an equation of state $p^{(m)} = w\, \rho^{(m)}$; depending on the
specific form of the self-interaction potential for the field, the constant $w$
can be arbitrary or must be fixed suitably.
| [
{
"created": "Thu, 9 Jan 2020 21:34:18 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Feb 2020 16:24:19 GMT",
"version": "v2"
}
] | 2020-07-03 | [
[
"Fermi",
"Davide",
"",
"Univ. di Milano"
],
[
"Gengo",
"Massimo",
"",
"Univ. di Milano"
],
[
"Pizzocchero",
"Livio",
"",
"Univ. di Milano"
]
] | We show that several integrable (i.e., exactly solvable) scalar cosmologies considered by Fr\'e, Sagnotti and Sorin (Nuclear Physics \textbf{B 877}(3) (2013), 1028--1106) can be generalized to include cases where the spatial curvature is not zero and, besides a scalar field, matter or radiation are present with an equation of state $p^{(m)} = w\, \rho^{(m)}$; depending on the specific form of the self-interaction potential for the field, the constant $w$ can be arbitrary or must be fixed suitably. |
0906.0926 | Luke Butcher | Luke M. Butcher, Michael Hobson, Anthony Lasenby | Bootstrapping gravity: a consistent approach to energy-momentum
self-coupling | 18 pages, RevTex; Published version | Phys.Rev.D80:084014,2009 | 10.1103/PhysRevD.80.084014 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is generally believed that coupling the graviton (a classical Fierz-Pauli
massless spin-2 field) to its own energy-momentum tensor successfully recreates
the dynamics of the Einstein field equations order by order; however the
validity of this idea has recently been brought into doubt [1]. Motivated by
this, we present a graviton action for which energy-momentum self-coupling is
indeed consistent with the Einstein field equations. The Hilbert
energy-momentum tensor for this graviton is calculated explicitly and shown to
supply the correct second-order term in the field equations; in contrast, the
Fierz-Pauli action fails to supply the correct term. A formalism for
perturbative expansions of metric-based gravitational theories is then
developed, and these techniques employed to demonstrate that our graviton
action is a starting point for a straightforward energy-momentum self-coupling
procedure that, order by order, generates the Einstein-Hilbert action (up to a
classically irrelevant surface term). The perturbative formalism is extended to
include matter and a cosmological constant, and interactions between
perturbations of a free matter field and the gravitational field are studied in
a vacuum background. Finally, the effect of a non-vacuum background is
examined, and the graviton is found to develop a non-vanishing ``mass-term'' in
the action.
| [
{
"created": "Thu, 4 Jun 2009 15:01:20 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Oct 2009 11:45:46 GMT",
"version": "v2"
}
] | 2009-10-29 | [
[
"Butcher",
"Luke M.",
""
],
[
"Hobson",
"Michael",
""
],
[
"Lasenby",
"Anthony",
""
]
] | It is generally believed that coupling the graviton (a classical Fierz-Pauli massless spin-2 field) to its own energy-momentum tensor successfully recreates the dynamics of the Einstein field equations order by order; however the validity of this idea has recently been brought into doubt [1]. Motivated by this, we present a graviton action for which energy-momentum self-coupling is indeed consistent with the Einstein field equations. The Hilbert energy-momentum tensor for this graviton is calculated explicitly and shown to supply the correct second-order term in the field equations; in contrast, the Fierz-Pauli action fails to supply the correct term. A formalism for perturbative expansions of metric-based gravitational theories is then developed, and these techniques employed to demonstrate that our graviton action is a starting point for a straightforward energy-momentum self-coupling procedure that, order by order, generates the Einstein-Hilbert action (up to a classically irrelevant surface term). The perturbative formalism is extended to include matter and a cosmological constant, and interactions between perturbations of a free matter field and the gravitational field are studied in a vacuum background. Finally, the effect of a non-vacuum background is examined, and the graviton is found to develop a non-vanishing ``mass-term'' in the action. |
2010.15202 | Ssohrab Borhanian | Ssohrab Borhanian | Gwbench: a novel Fisher information package for gravitational-wave
benchmarking | 18 pages, 6 figures, 4 tables | Class. Quantum Grav. 38 175014 (2021) | 10.1088/1361-6382/ac1618 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a new Python package, gwbench, implementing the well-established
Fisher information formalism as a fast and straightforward tool for the purpose
of gravitational-wave benchmarking, i.e. the estimation of signal-to-noise
ratios and measurement errors of gravitational waves observed by a network of
detectors. Such an infrastructure is necessary due to the high computational
cost of Bayesian parameter estimation methods which renders them less effective
for the scientific assessment of gravitational waveforms, detectors, and
networks of detectors, especially when determining their effects on large
populations of gravitational-wave sources spread throughout the universe.
gwbench further gives quick access to detector locations and sensitivities,
while including the effects of Earth's rotation on the latter, as well as
waveform models and their derivatives, while giving access to the host of
waveforms available in the LSC Algorithm Library. With the provided
functionality, gwbench is relevant for a wide variety of applications in
gravitational-wave astronomy such as waveform modeling, detector development,
cosmology, and tests of general relativity.
| [
{
"created": "Wed, 28 Oct 2020 19:52:19 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Nov 2020 15:54:22 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Aug 2021 16:51:07 GMT",
"version": "v3"
}
] | 2021-08-31 | [
[
"Borhanian",
"Ssohrab",
""
]
] | We present a new Python package, gwbench, implementing the well-established Fisher information formalism as a fast and straightforward tool for the purpose of gravitational-wave benchmarking, i.e. the estimation of signal-to-noise ratios and measurement errors of gravitational waves observed by a network of detectors. Such an infrastructure is necessary due to the high computational cost of Bayesian parameter estimation methods which renders them less effective for the scientific assessment of gravitational waveforms, detectors, and networks of detectors, especially when determining their effects on large populations of gravitational-wave sources spread throughout the universe. gwbench further gives quick access to detector locations and sensitivities, while including the effects of Earth's rotation on the latter, as well as waveform models and their derivatives, while giving access to the host of waveforms available in the LSC Algorithm Library. With the provided functionality, gwbench is relevant for a wide variety of applications in gravitational-wave astronomy such as waveform modeling, detector development, cosmology, and tests of general relativity. |
1506.05014 | Minas Tsoukalas | Christos Charmousis and Minas Tsoukalas | On Lovelock galileons and black holes | 11 pages, minor corrections, references added, version accepted to
PRD | Phys. Rev. D 92, 104050 (2015) | 10.1103/PhysRevD.92.104050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a scalar-tensor version of Lovelock theory with a non trivial higher
order galileon term involving the coupling of the Lovelock two tensor with
derivatives of the scalar galileon field. For a static and spherically
symmetric spacetime we extend the Boulware-Deser solution to the presence of a
Galileon field. The hairy solution has a regular scalar field on the black hole
event horizon and presents certain self tuning properties for the bulk
cosmological constant and the Gauss-Bonnet coupling. The combined time and
radial dependence of the galileon field permits its horizon regularity.
Furthermore in order to investigate the effects of linear time dependence we
find spherically symmetric solutions in 4 and 5 spacetime dimensions. They are
shown to have singular horizons. Afar from the Schwarzschild radius and for
weak higher dimensional couplings the solutions are perturbratively close to GR
representing GR like star solutions for scalar tensor theories.
| [
{
"created": "Tue, 16 Jun 2015 16:11:14 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Dec 2015 07:52:26 GMT",
"version": "v2"
}
] | 2015-12-09 | [
[
"Charmousis",
"Christos",
""
],
[
"Tsoukalas",
"Minas",
""
]
] | We study a scalar-tensor version of Lovelock theory with a non trivial higher order galileon term involving the coupling of the Lovelock two tensor with derivatives of the scalar galileon field. For a static and spherically symmetric spacetime we extend the Boulware-Deser solution to the presence of a Galileon field. The hairy solution has a regular scalar field on the black hole event horizon and presents certain self tuning properties for the bulk cosmological constant and the Gauss-Bonnet coupling. The combined time and radial dependence of the galileon field permits its horizon regularity. Furthermore in order to investigate the effects of linear time dependence we find spherically symmetric solutions in 4 and 5 spacetime dimensions. They are shown to have singular horizons. Afar from the Schwarzschild radius and for weak higher dimensional couplings the solutions are perturbratively close to GR representing GR like star solutions for scalar tensor theories. |
0710.4345 | Spindel | Robert Brout, Serge Massar, Renaud Parentani, Philippe Spindel | A Primer for Black Hole Quantum Physics | An old review article on black hole evaporation and black hole
thermodynamics, put on the archive following popular demand, 178 pages, 21
figures (This text differs in slightly from the published version) | Phys.Rept.260:329-454,1995 | 10.1016/0370-1573(95)00008-5 | null | gr-qc hep-th | null | The mechanisms which give rise to Hawking radiation are revealed by analyzing
in detail pair production in the presence of horizons. In preparation for the
black hole problem, three preparatory problems are dwelt with at length: pair
production in an external electric field, thermalization of a uniformly
accelerated detector and accelerated mirrors. In the light of these examples,
the black hole evaporation problem is then presented.
The leitmotif is the singular behavior of modes on the horizon which gives
rise to a steady rate of production. Special emphasis is put on how each
produced particle contributes to the mean albeit arising from a particular
vacuum fluctuation. It is the mean which drives the semiclassical back
reaction. This aspect is analyzed in more detail than heretofore and in
particular its drawbacks are emphasized. It is the semiclassical theory which
gives rise to Hawking's famous equation for the loss of mass of the black hole
due to evaporation $dM/dt \simeq -1/M^2$. Black hole thermodynamics is derived
from the evaporation process whereupon the reservoir character of the black
hole is manifest. The relation to the thermodynamics of the eternal black hole
through the Hartle--Hawking vacuum and the Killing identity are displayed.
It is through the analysis of the fluctuations of the field configurations
which give rise to a particular Hawking photon that the dubious character of
the semiclassical theory is manifest. The present frontier of research revolves
around this problem and is principally concerned with the fact that one calls
upon energy scales that are greater than Planckian and the possibility of a non
unitary evolution as well. These last subjects are presented in qualitative
fashion only, so that this review stops at the threshold of quantum gravity.
| [
{
"created": "Tue, 23 Oct 2007 21:09:32 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Brout",
"Robert",
""
],
[
"Massar",
"Serge",
""
],
[
"Parentani",
"Renaud",
""
],
[
"Spindel",
"Philippe",
""
]
] | The mechanisms which give rise to Hawking radiation are revealed by analyzing in detail pair production in the presence of horizons. In preparation for the black hole problem, three preparatory problems are dwelt with at length: pair production in an external electric field, thermalization of a uniformly accelerated detector and accelerated mirrors. In the light of these examples, the black hole evaporation problem is then presented. The leitmotif is the singular behavior of modes on the horizon which gives rise to a steady rate of production. Special emphasis is put on how each produced particle contributes to the mean albeit arising from a particular vacuum fluctuation. It is the mean which drives the semiclassical back reaction. This aspect is analyzed in more detail than heretofore and in particular its drawbacks are emphasized. It is the semiclassical theory which gives rise to Hawking's famous equation for the loss of mass of the black hole due to evaporation $dM/dt \simeq -1/M^2$. Black hole thermodynamics is derived from the evaporation process whereupon the reservoir character of the black hole is manifest. The relation to the thermodynamics of the eternal black hole through the Hartle--Hawking vacuum and the Killing identity are displayed. It is through the analysis of the fluctuations of the field configurations which give rise to a particular Hawking photon that the dubious character of the semiclassical theory is manifest. The present frontier of research revolves around this problem and is principally concerned with the fact that one calls upon energy scales that are greater than Planckian and the possibility of a non unitary evolution as well. These last subjects are presented in qualitative fashion only, so that this review stops at the threshold of quantum gravity. |
1010.4004 | Ivan Agullo | I. Agullo, J. Navarro-Salas, G. J. Olmo, and L. Parker | Acceleration radiation, transition probabilities, and trans-Planckian
physics | 19 pages | New J.Phys.12:095017,2010 | 10.1088/1367-2630/12/9/095017 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important question in the derivation of the acceleration radiation, which
also arises in Hawking's derivation of black hole radiance, is the need to
invoke trans-Planckian physics for the quantum field that originates the
created quanta. We point out that this issue can be further clarified by
reconsidering the analysis in terms of particle detectors, transition
probabilities, and local two-point functions. By writing down separate
expressions for the spontaneous- and induced-transition probabilities of a
uniformly accelerated detector, we show that the bulk of the effect comes from
the natural (non trans-Planckian) scale of the problem, which largely
diminishes the importance of the trans-Planckian sector. This is so, at least,
when trans-Planckian physics is defined in a Lorentz invariant way. This
analysis also suggests how to define and estimate the role of trans-Planckian
physics in the Hawking effect itself.
| [
{
"created": "Tue, 19 Oct 2010 18:46:59 GMT",
"version": "v1"
}
] | 2015-03-12 | [
[
"Agullo",
"I.",
""
],
[
"Navarro-Salas",
"J.",
""
],
[
"Olmo",
"G. J.",
""
],
[
"Parker",
"L.",
""
]
] | An important question in the derivation of the acceleration radiation, which also arises in Hawking's derivation of black hole radiance, is the need to invoke trans-Planckian physics for the quantum field that originates the created quanta. We point out that this issue can be further clarified by reconsidering the analysis in terms of particle detectors, transition probabilities, and local two-point functions. By writing down separate expressions for the spontaneous- and induced-transition probabilities of a uniformly accelerated detector, we show that the bulk of the effect comes from the natural (non trans-Planckian) scale of the problem, which largely diminishes the importance of the trans-Planckian sector. This is so, at least, when trans-Planckian physics is defined in a Lorentz invariant way. This analysis also suggests how to define and estimate the role of trans-Planckian physics in the Hawking effect itself. |
2105.13896 | Qasem Exirifard | Qasem Exirifard, Ebrahim Karimi | Schr\"odinger equation in a general curved space-time geometry | 39 pages, 9 figures, Matches the published version | International Journal of Modern Physics D(2022) 225001 | 10.1142/S0218271822500183 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider relativistic quantum field theory in the presence of an external
electric potential in a general curved space-time geometry. We utilise Fermi
coordinates adapted to the time-like geodesic to describe the low-energy
physics in the laboratory and calculate the leading correction due to the
curvature of the space-time geometry to the Schr\"odinger equation. We then
compute the non-vanishing probability of excitation for a hydrogen atom that
falls in or is scattered by a general Schwarzschild black hole. The photon that
is emitted from the excited state by spontaneous emission extracts energy from
the black hole, increases the decay rate of the black hole and adds to the
information paradox.
| [
{
"created": "Wed, 26 May 2021 18:47:44 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Nov 2021 15:08:39 GMT",
"version": "v2"
}
] | 2022-01-10 | [
[
"Exirifard",
"Qasem",
""
],
[
"Karimi",
"Ebrahim",
""
]
] | We consider relativistic quantum field theory in the presence of an external electric potential in a general curved space-time geometry. We utilise Fermi coordinates adapted to the time-like geodesic to describe the low-energy physics in the laboratory and calculate the leading correction due to the curvature of the space-time geometry to the Schr\"odinger equation. We then compute the non-vanishing probability of excitation for a hydrogen atom that falls in or is scattered by a general Schwarzschild black hole. The photon that is emitted from the excited state by spontaneous emission extracts energy from the black hole, increases the decay rate of the black hole and adds to the information paradox. |
1208.5839 | Anil Zenginoglu C | An{\i}l Zengino\u{g}lu, Gaurav Khanna, Lior M. Burko | Intermediate behavior of Kerr tails | 16 pages | General Relativity and Gravitation 46, 1672 (2014) | 10.1007/s10714-014-1672-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The numerical investigation of wave propagation in the asymptotic domain of
Kerr spacetime has only recently been possible thanks to the construction of
suitable hyperboloidal coordinates. The asymptotics revealed an apparent puzzle
in the decay rates of scalar fields: the late-time rates seemed to depend on
whether finite distance observers are in the strong field domain or far away
from the rotating black hole, an apparent phenomenon dubbed "splitting". We
discuss far-field "splitting" in the full field and near-horizon "splitting" in
certain projected modes using horizon-penetrating, hyperboloidal coordinates.
For either case we propose an explanation to the cause of the "splitting"
behavior, and we determine uniquely decay rates that previous studies found to
be ambiguous or immeasurable. The far-field "splitting" is explained by
competition between projected modes. The near-horizon "splitting" is due to
excitation of lower multipole modes that back excite the multipole mode for
which "splitting" is observed. In both cases "splitting" is an intermediate
effect, such that asymptotically in time strong field rates are valid at all
finite distances. At any finite time, however, there are three domains with
different decay rates whose boundaries move outwards during evolution. We then
propose a formula for the decay rate of tails that takes into account the
inter--mode excitation effect that we study.
| [
{
"created": "Wed, 29 Aug 2012 04:58:21 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jun 2013 20:08:42 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Feb 2014 13:33:07 GMT",
"version": "v3"
}
] | 2014-02-18 | [
[
"Zenginoğlu",
"Anıl",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Burko",
"Lior M.",
""
]
] | The numerical investigation of wave propagation in the asymptotic domain of Kerr spacetime has only recently been possible thanks to the construction of suitable hyperboloidal coordinates. The asymptotics revealed an apparent puzzle in the decay rates of scalar fields: the late-time rates seemed to depend on whether finite distance observers are in the strong field domain or far away from the rotating black hole, an apparent phenomenon dubbed "splitting". We discuss far-field "splitting" in the full field and near-horizon "splitting" in certain projected modes using horizon-penetrating, hyperboloidal coordinates. For either case we propose an explanation to the cause of the "splitting" behavior, and we determine uniquely decay rates that previous studies found to be ambiguous or immeasurable. The far-field "splitting" is explained by competition between projected modes. The near-horizon "splitting" is due to excitation of lower multipole modes that back excite the multipole mode for which "splitting" is observed. In both cases "splitting" is an intermediate effect, such that asymptotically in time strong field rates are valid at all finite distances. At any finite time, however, there are three domains with different decay rates whose boundaries move outwards during evolution. We then propose a formula for the decay rate of tails that takes into account the inter--mode excitation effect that we study. |
gr-qc/9906118 | Valery M. Koryukin | Valery Koryukin (Mari State Technical University) | Neutrinos of Universe and masses of particles | 11 pages, submitted to PANIC'99 | null | null | null | gr-qc | null | The detection and the research of the neutrinos background of
Universe are the attractive problems. This problems do not seem the
unpromising one in the case of the high neutrinos density that is necessary for
the explanation of the nucleons-antinucleons asymmetry of Universe. It was
offered before to use the low energy neutrinos background of Universe for the
explanation of the gravitational phenomena with the quantum position attracting
the Casimir's effect for this. As a result it was connected the gravitational
constant with the parameters characterizing the electroweak interactions. If
now we shall be based on the results of the experements fixing the equality of
the gravitation mass and the inert one then it can consider that the spectrum
of the particle masses is defined by their interaction with the neutrinos
background of Universe.
| [
{
"created": "Tue, 29 Jun 1999 11:46:57 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Koryukin",
"Valery",
"",
"Mari State Technical University"
]
] | The detection and the research of the neutrinos background of Universe are the attractive problems. This problems do not seem the unpromising one in the case of the high neutrinos density that is necessary for the explanation of the nucleons-antinucleons asymmetry of Universe. It was offered before to use the low energy neutrinos background of Universe for the explanation of the gravitational phenomena with the quantum position attracting the Casimir's effect for this. As a result it was connected the gravitational constant with the parameters characterizing the electroweak interactions. If now we shall be based on the results of the experements fixing the equality of the gravitation mass and the inert one then it can consider that the spectrum of the particle masses is defined by their interaction with the neutrinos background of Universe. |
1602.04459 | Josef Schmidt | Ji\v{r}\'i Bi\v{c}\'ak, Josef Schmidt | Energy-momentum tensors in linearized Einstein's theory and massive
gravity: The question of uniqueness | 13 pages | Phys. Rev. D 93, 024009 (2016) | 10.1103/PhysRevD.93.024009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The question of the uniqueness of energy-momentum tensors in the linearized
general relativity and in the linear massive gravity is analyzed without using
variational techniques. We start from a natural ansatz for the form of the
tensor (for example, that it is a linear combination of the terms quadratic in
the first derivatives), and require it to be conserved as a consequence of
field equations. In the case of the linear gravity in a general gauge we find a
four-parametric system of conserved second-rank tensors which contains a unique
symmetric tensor. This turns out to be the linearized Landau-Lifshitz
pseudotensor employed often in full general relativity. We elucidate the
relation of the four-parametric system to the expression proposed recently by
Butcher et al. "on physical grounds" in harmonic gauge, and we show that the
results coincide in the case of high-frequency waves in vacuum after a suitable
averaging. In the massive gravity we show how one can arrive at the expression
which coincides with the "generalized linear symmetric Landau-Lifshitz" tensor.
However, there exists another uniquely given simpler symmetric tensor which can
be obtained by adding the divergence of a suitable superpotential to the
canonical energy-momentum tensor following from the Fierz-Pauli action. In
contrast to the symmetric tensor derived by the Belinfante procedure which
involves the second derivatives of the field variables, this expression
contains only the field and its first derivatives. It is simpler than the
generalized Landau-Lifshitz tensor but both yield the same total quantities
since they differ by the divergence of a superpotential. We also discuss the
role of the gauge conditions in the proofs of the uniqueness. In the Appendix,
the use of the symbolic tensor manipulation software Cadabra is briefly
described.
| [
{
"created": "Sun, 14 Feb 2016 14:11:36 GMT",
"version": "v1"
}
] | 2016-02-16 | [
[
"Bičák",
"Jiří",
""
],
[
"Schmidt",
"Josef",
""
]
] | The question of the uniqueness of energy-momentum tensors in the linearized general relativity and in the linear massive gravity is analyzed without using variational techniques. We start from a natural ansatz for the form of the tensor (for example, that it is a linear combination of the terms quadratic in the first derivatives), and require it to be conserved as a consequence of field equations. In the case of the linear gravity in a general gauge we find a four-parametric system of conserved second-rank tensors which contains a unique symmetric tensor. This turns out to be the linearized Landau-Lifshitz pseudotensor employed often in full general relativity. We elucidate the relation of the four-parametric system to the expression proposed recently by Butcher et al. "on physical grounds" in harmonic gauge, and we show that the results coincide in the case of high-frequency waves in vacuum after a suitable averaging. In the massive gravity we show how one can arrive at the expression which coincides with the "generalized linear symmetric Landau-Lifshitz" tensor. However, there exists another uniquely given simpler symmetric tensor which can be obtained by adding the divergence of a suitable superpotential to the canonical energy-momentum tensor following from the Fierz-Pauli action. In contrast to the symmetric tensor derived by the Belinfante procedure which involves the second derivatives of the field variables, this expression contains only the field and its first derivatives. It is simpler than the generalized Landau-Lifshitz tensor but both yield the same total quantities since they differ by the divergence of a superpotential. We also discuss the role of the gauge conditions in the proofs of the uniqueness. In the Appendix, the use of the symbolic tensor manipulation software Cadabra is briefly described. |
1203.4801 | Michel Miranda | Tonatiuh Matos, L. Arturo Urena-Lopez and Galaxia Miranda | Wormhole Cosmic Censorship | null | Gen. Rel. Grav. 48, (2016), 61 | 10.1007/s10714-016-2040-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the properties of a Kerr-like wormhole supported by phantom
matter, which is an exact solution of the Einstein-phantom field equations. It
is shown that the solution has a naked ring singularity which is unreachable to
null geodesics falling freely from the outside. Similarly to Roger Penrose's
cosmic censorship, that states that all naked singularities in the Universe
must be protected by event horizons, here we conjecture from our results that a
naked singularity can also be fully protected by the intrinsic properties of a
wormhole's throat.
| [
{
"created": "Wed, 21 Mar 2012 18:58:16 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Jun 2013 05:57:00 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Jul 2015 02:06:14 GMT",
"version": "v3"
},
{
"created": "Mon, 28 Mar 2016 21:23:32 GMT",
"version": "v4"
}
] | 2021-02-09 | [
[
"Matos",
"Tonatiuh",
""
],
[
"Urena-Lopez",
"L. Arturo",
""
],
[
"Miranda",
"Galaxia",
""
]
] | We analyze the properties of a Kerr-like wormhole supported by phantom matter, which is an exact solution of the Einstein-phantom field equations. It is shown that the solution has a naked ring singularity which is unreachable to null geodesics falling freely from the outside. Similarly to Roger Penrose's cosmic censorship, that states that all naked singularities in the Universe must be protected by event horizons, here we conjecture from our results that a naked singularity can also be fully protected by the intrinsic properties of a wormhole's throat. |
1804.07740 | Mohammad Mehrafarin | Hamideh Balajani and Mohammad Mehrafarin | Berry phase of primordial scalar and tensor perturbations in
single-field inflationary models | null | Phys. Lett. A 382 (2018) 1524 | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the single-field slow-roll inflation, we derive the
Hamiltonian of the linear primordial scalar and tensor perturbations in the
form of time-dependent harmonic oscillator Hamiltonians. We find the invariant
operators of the resulting Hamiltonians and use their eigenstates to calculate
the adiabatic Berry phase for sub-horizon modes in terms of the
Lewis-Riesenfeld phase. We conclude by discussing the discrepancy in the
results of Pal et. al [Class. Quant. Grav. 30 (2013) 12] for these Berry
phases, which is resolved to yield agreement with our results.
| [
{
"created": "Fri, 20 Apr 2018 17:35:09 GMT",
"version": "v1"
}
] | 2018-04-24 | [
[
"Balajani",
"Hamideh",
""
],
[
"Mehrafarin",
"Mohammad",
""
]
] | In the framework of the single-field slow-roll inflation, we derive the Hamiltonian of the linear primordial scalar and tensor perturbations in the form of time-dependent harmonic oscillator Hamiltonians. We find the invariant operators of the resulting Hamiltonians and use their eigenstates to calculate the adiabatic Berry phase for sub-horizon modes in terms of the Lewis-Riesenfeld phase. We conclude by discussing the discrepancy in the results of Pal et. al [Class. Quant. Grav. 30 (2013) 12] for these Berry phases, which is resolved to yield agreement with our results. |
0904.3541 | Carlos O. Lousto | Carlos O. Lousto, Manuela Campanelli, Yosef Zlochower, Hiroyuki Nakano
(RIT) | Remnant Masses, Spins and Recoils from the Merger of Generic Black-Hole
Binaries | 15 pages, 2 figures. Rewritten and added new section. | Class.Quant.Grav.27:114006,2010 | 10.1088/0264-9381/27/11/114006 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain empirical formulae for the final remnant black hole mass, spin, and
recoil velocity from merging black-hole binaries with arbitrary mass ratios and
spins. Our formulae are based on the mass ratio and spin dependence of the
post-Newtonian expressions for the instantaneous radiated energy, linear
momentum, and angular momentum, as well as the ISCO binding energy and angular
momentum. The relative weight between the different terms is fixed by amplitude
parameters chosen through a least-squares fit of recently available fully
nonlinear numerical simulations. These formulae can be used for statistical
studies of N-body simulations of galaxy cores and clusters, and the
cosmological growth of supermassive black holes. As an example, we use these
formulae to obtain a universal spin magnitude distribution of merged black
holes and recoil velocity distributions for dry and hot/cold wet mergers. We
also revisit the long term orbital precession and resonances and discuss how
they affect spin distributions before the merging regime.
| [
{
"created": "Wed, 22 Apr 2009 20:01:10 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2009 19:22:23 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Jan 2010 22:25:40 GMT",
"version": "v3"
},
{
"created": "Tue, 20 Apr 2010 21:28:28 GMT",
"version": "v4"
}
] | 2010-05-25 | [
[
"Lousto",
"Carlos O.",
"",
"RIT"
],
[
"Campanelli",
"Manuela",
"",
"RIT"
],
[
"Zlochower",
"Yosef",
"",
"RIT"
],
[
"Nakano",
"Hiroyuki",
"",
"RIT"
]
] | We obtain empirical formulae for the final remnant black hole mass, spin, and recoil velocity from merging black-hole binaries with arbitrary mass ratios and spins. Our formulae are based on the mass ratio and spin dependence of the post-Newtonian expressions for the instantaneous radiated energy, linear momentum, and angular momentum, as well as the ISCO binding energy and angular momentum. The relative weight between the different terms is fixed by amplitude parameters chosen through a least-squares fit of recently available fully nonlinear numerical simulations. These formulae can be used for statistical studies of N-body simulations of galaxy cores and clusters, and the cosmological growth of supermassive black holes. As an example, we use these formulae to obtain a universal spin magnitude distribution of merged black holes and recoil velocity distributions for dry and hot/cold wet mergers. We also revisit the long term orbital precession and resonances and discuss how they affect spin distributions before the merging regime. |
2005.14211 | Jose' P. S. Lemos | Jos\'e P. S. Lemos, Diogo L. F. G. Silva | Maximal extension of the Schwarzschild metric: From
Painlev\'e-Gullstrand to Kruskal-Szekeres | 18 pages, 7 figures | Annals of Physics 430, 168497 (2021) | 10.1016/j.aop.2021.168497 | null | gr-qc astro-ph.HE hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find a specific coordinate system that goes from the Painlev\'e-Gullstrand
partial extension to the Kruskal-Szekeres maximal extension and thus exhibit
the maximal extension of the Schwarzschild metric in a unified picture. We do
this by adopting two time coordinates, one being the proper time of a
congruence of outgoing timelike geodesics, the other being the proper time of a
congruence of ingoing timelike geodesics, both parameterized by the same energy
per unit mass $E$. $E$ is in the range $1\leq E<\infty$ with the limit
$E=\infty$ yielding the Kruskal-Szekeres maximal extension. So, through such an
integrated description one sees that the Kruskal-Szekeres solution belongs to
this family of extensions parameterized by $E$. Our family of extensions is
different from the Novikov-Lema\^itre family parameterized also by the energy
$E$ of timelike geodesics, with the Novikov extension holding for $0<E<1$ and
being maximal, and the Lema\^itre extension holding for $1\leq E<\infty$ and
being partial, not maximal, and moreover its $E=\infty$ limit evanescing in a
Minkowski spacetime rather than ending in the Kruskal-Szekeres spacetime.
| [
{
"created": "Thu, 28 May 2020 18:00:25 GMT",
"version": "v1"
}
] | 2021-11-01 | [
[
"Lemos",
"José P. S.",
""
],
[
"Silva",
"Diogo L. F. G.",
""
]
] | We find a specific coordinate system that goes from the Painlev\'e-Gullstrand partial extension to the Kruskal-Szekeres maximal extension and thus exhibit the maximal extension of the Schwarzschild metric in a unified picture. We do this by adopting two time coordinates, one being the proper time of a congruence of outgoing timelike geodesics, the other being the proper time of a congruence of ingoing timelike geodesics, both parameterized by the same energy per unit mass $E$. $E$ is in the range $1\leq E<\infty$ with the limit $E=\infty$ yielding the Kruskal-Szekeres maximal extension. So, through such an integrated description one sees that the Kruskal-Szekeres solution belongs to this family of extensions parameterized by $E$. Our family of extensions is different from the Novikov-Lema\^itre family parameterized also by the energy $E$ of timelike geodesics, with the Novikov extension holding for $0<E<1$ and being maximal, and the Lema\^itre extension holding for $1\leq E<\infty$ and being partial, not maximal, and moreover its $E=\infty$ limit evanescing in a Minkowski spacetime rather than ending in the Kruskal-Szekeres spacetime. |
0709.0299 | Latham Boyle | Latham Boyle, Michael Kesden and Samaya Nissanke | Binary black hole merger: symmetry and the spin expansion | 4 pages, 4 figures, matches Phys. Rev. Lett. version | Phys.Rev.Lett.100:151101,2008 | 10.1103/PhysRevLett.100.151101 | null | gr-qc astro-ph hep-ph hep-th | null | We regard binary black hole (BBH) merger as a map from a simple initial state
(two Kerr black holes, with dimensionless spins {\bf a} and {\bf b}) to a
simple final state (a Kerr black hole with mass m, dimensionless spin {\bf s},
and kick velocity {\bf k}). By expanding this map around {\bf a} = {\bf b} = 0
and applying symmetry constraints, we obtain a simple formalism that is
remarkably successful at explaining existing BBH simulations. It also makes
detailed predictions and suggests a more efficient way of mapping the parameter
space of binary black hole merger. Since we rely on symmetry rather than
dynamics, our expansion complements previous analytical techniques.
| [
{
"created": "Tue, 4 Sep 2007 19:02:29 GMT",
"version": "v1"
},
{
"created": "Fri, 9 May 2008 02:52:03 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Boyle",
"Latham",
""
],
[
"Kesden",
"Michael",
""
],
[
"Nissanke",
"Samaya",
""
]
] | We regard binary black hole (BBH) merger as a map from a simple initial state (two Kerr black holes, with dimensionless spins {\bf a} and {\bf b}) to a simple final state (a Kerr black hole with mass m, dimensionless spin {\bf s}, and kick velocity {\bf k}). By expanding this map around {\bf a} = {\bf b} = 0 and applying symmetry constraints, we obtain a simple formalism that is remarkably successful at explaining existing BBH simulations. It also makes detailed predictions and suggests a more efficient way of mapping the parameter space of binary black hole merger. Since we rely on symmetry rather than dynamics, our expansion complements previous analytical techniques. |
1210.1449 | Abraham Harte | Abraham I. Harte | Strong lensing, plane gravitational waves and transient flashes | 32 pages, 8 figures, fixed typos and slightly added to some
explanations | null | 10.1088/0264-9381/30/7/075011 | AEI-2012-106 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Plane-symmetric gravitational waves are considered as gravitational lenses.
Numbers of images, frequency shifts, mutual angles, and image distortion
parameters are computed exactly in essentially all non-singular plane wave
spacetimes. For a fixed observation event in a particular plane wave spacetime,
the number of images is found to be the same for almost every source. This
number can be any positive integer, including infinity. Wavepackets of finite
width are discussed in detail as well as waves which maintain a constant
amplitude for all time. Short wavepackets are found to generically produce up
to two images of each source which appear (separately) only some time after the
wave has passed. They are initially infinitely bright, infinitely blueshifted
images of the infinitely distant past. Later, these images become dim and
acquire a rapidly-increasing redshift. For sufficiently weak wavepackets, one
such "flash" almost always exists. The appearance of a second flash requires
that the Ricci tensor inside the wave exceed a certain threshold. This might
occur if a gravitational plane wave is sourced by, e.g., a sufficiently strong
electromagnetic plane wave.
| [
{
"created": "Thu, 4 Oct 2012 14:10:14 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Oct 2012 16:12:40 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Harte",
"Abraham I.",
""
]
] | Plane-symmetric gravitational waves are considered as gravitational lenses. Numbers of images, frequency shifts, mutual angles, and image distortion parameters are computed exactly in essentially all non-singular plane wave spacetimes. For a fixed observation event in a particular plane wave spacetime, the number of images is found to be the same for almost every source. This number can be any positive integer, including infinity. Wavepackets of finite width are discussed in detail as well as waves which maintain a constant amplitude for all time. Short wavepackets are found to generically produce up to two images of each source which appear (separately) only some time after the wave has passed. They are initially infinitely bright, infinitely blueshifted images of the infinitely distant past. Later, these images become dim and acquire a rapidly-increasing redshift. For sufficiently weak wavepackets, one such "flash" almost always exists. The appearance of a second flash requires that the Ricci tensor inside the wave exceed a certain threshold. This might occur if a gravitational plane wave is sourced by, e.g., a sufficiently strong electromagnetic plane wave. |
2308.09826 | John Friedman | John L. Friedman | Notes on Gravitational Physics | 371 pages. This updated version includes a chapter on cosmology as
well as a number of revisions and corrections | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/4.0/ | These notes are self-contained, with the first 7 chapters used in a
one-semester course with recommended texts by Wald, by Misner, Thorne and
Wheeler, and by Schutz. In its treatment of topics covered in these standard
texts, the presentation here typically includes steps skipped in Wald or MTW.
Treatments of gravitational waves, particle orbits in black-hole backgrounds,
the Teukolsky equation, and the initial value equations are motivated in part
by the discoveries of gravitational waves from the inspiral and coalescence of
binary black holes and neutron stars, advances in numerical relativity, and the
expected LISA space-based observatory. The notes begin with a detailed
presentation of special relativity with a geometrical orientation, starting
with with time dilation and length contraction and including relativistic
particles, fluids, electromagnetism, and curvilinear coordinates. Chaps. 2-5
cover curvature, the Einstein equation, relativistic stars, and black holes.
Chap. 6, on gravitational waves, includes a discussion of detection and noise.
Chap. 7 is a brief introduction to cosmology, deriving the metrics of
homogeneous isotropic space, the equations governing a universe with matter,
radiation and vacuum energy, and their solutions, and discussions of the
cosmological redshift and on using gravitational waves to measure the Hubble
constant.
Chap. 8, on the initial value problem, has a section on the form of the
equations used in numerical relativity. The Newman-Penrose formalism and the
Teukolsky equation are covered in Chap. 9. Following that is a chapter on
black-hole thermodynamics and a final chapter on the gravitational action and
on conserved quantities for asymptotically flat spacetimes, using Noether's
theorem. An appendix covers forms, densities, integration, and Cartan calculus.
| [
{
"created": "Fri, 18 Aug 2023 21:31:53 GMT",
"version": "v1"
},
{
"created": "Tue, 21 May 2024 15:56:45 GMT",
"version": "v2"
}
] | 2024-05-22 | [
[
"Friedman",
"John L.",
""
]
] | These notes are self-contained, with the first 7 chapters used in a one-semester course with recommended texts by Wald, by Misner, Thorne and Wheeler, and by Schutz. In its treatment of topics covered in these standard texts, the presentation here typically includes steps skipped in Wald or MTW. Treatments of gravitational waves, particle orbits in black-hole backgrounds, the Teukolsky equation, and the initial value equations are motivated in part by the discoveries of gravitational waves from the inspiral and coalescence of binary black holes and neutron stars, advances in numerical relativity, and the expected LISA space-based observatory. The notes begin with a detailed presentation of special relativity with a geometrical orientation, starting with with time dilation and length contraction and including relativistic particles, fluids, electromagnetism, and curvilinear coordinates. Chaps. 2-5 cover curvature, the Einstein equation, relativistic stars, and black holes. Chap. 6, on gravitational waves, includes a discussion of detection and noise. Chap. 7 is a brief introduction to cosmology, deriving the metrics of homogeneous isotropic space, the equations governing a universe with matter, radiation and vacuum energy, and their solutions, and discussions of the cosmological redshift and on using gravitational waves to measure the Hubble constant. Chap. 8, on the initial value problem, has a section on the form of the equations used in numerical relativity. The Newman-Penrose formalism and the Teukolsky equation are covered in Chap. 9. Following that is a chapter on black-hole thermodynamics and a final chapter on the gravitational action and on conserved quantities for asymptotically flat spacetimes, using Noether's theorem. An appendix covers forms, densities, integration, and Cartan calculus. |
1708.07851 | Andreas Sch\"arer | Manuel Hohmann, Andreas Sch\"arer | Post-Newtonian parameters $\gamma$ and $\beta$ of scalar-tensor gravity
for a homogeneous gravitating sphere | 35 pages, 5 figures | Phys. Rev. D 96, 104026 (2017) | 10.1103/PhysRevD.96.104026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the parameters $\gamma$ and $\beta$ in the parametrized
post-Newtonian (PPN) formalism for scalar-tensor gravity (STG) with an
arbitrary potential, under the assumption that the source matter is given by a
non-rotating sphere of constant density, pressure and internal energy. For our
calculation we write the STG field equations in a form which is manifestly
invariant under conformal transformations of the metric and redefinitions of
the scalar field. This easily shows that also the obtained PPN parameters are
invariant under such transformations. Our result is consistent with the
expectation that STG is a fully conservative theory, i.e., only $\gamma$ and
$\beta$ differ from their general relativity values $\gamma = \beta = 1$, which
indicates the absence of preferred frame and preferred location effects. We
find that the values of the PPN parameters depend on both the radius of the
gravitating mass source and the distance between the source and the observer.
Most interestingly, we find that also at large distances from the source
$\beta$ does not approach $\beta = 1$, but receives corrections due to a
modified gravitational self-energy of the source. Finally, we compare our
result to a number of measurements of $\gamma$ and $\beta$ in the Solar System.
We find that in particular measurements of $\beta$ improve the previously
obtained bounds on the theory parameters, due to the aforementioned
long-distance corrections.
| [
{
"created": "Fri, 25 Aug 2017 18:15:12 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Sep 2017 15:56:37 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Hohmann",
"Manuel",
""
],
[
"Schärer",
"Andreas",
""
]
] | We calculate the parameters $\gamma$ and $\beta$ in the parametrized post-Newtonian (PPN) formalism for scalar-tensor gravity (STG) with an arbitrary potential, under the assumption that the source matter is given by a non-rotating sphere of constant density, pressure and internal energy. For our calculation we write the STG field equations in a form which is manifestly invariant under conformal transformations of the metric and redefinitions of the scalar field. This easily shows that also the obtained PPN parameters are invariant under such transformations. Our result is consistent with the expectation that STG is a fully conservative theory, i.e., only $\gamma$ and $\beta$ differ from their general relativity values $\gamma = \beta = 1$, which indicates the absence of preferred frame and preferred location effects. We find that the values of the PPN parameters depend on both the radius of the gravitating mass source and the distance between the source and the observer. Most interestingly, we find that also at large distances from the source $\beta$ does not approach $\beta = 1$, but receives corrections due to a modified gravitational self-energy of the source. Finally, we compare our result to a number of measurements of $\gamma$ and $\beta$ in the Solar System. We find that in particular measurements of $\beta$ improve the previously obtained bounds on the theory parameters, due to the aforementioned long-distance corrections. |
gr-qc/0409023 | Sayan Kar | Supratik Pal, Somnath Bharadwaj and Sayan Kar (IIT Kharagpur, India) | Can extra dimensional effects replace dark matter ? | 10 pages, no figures, RevTex4 | Phys.Lett. B609 (2005) 194-199 | 10.1016/j.physletb.2005.01.043 | null | gr-qc astro-ph hep-th | null | In the braneworld scenario, the four dimensional effective Einstein equation
has extra terms which arise from the embedding of the 3-brane in the bulk. We
show that in this modified theory of gravity, it is possible to model
observations of galaxy rotation curves and the X-ray profiles of clusters of
galaxies, without the need for dark matter. In this scenario, a traceless
tensor field which arises from the projection of the bulk Weyl tensor on the
brane, provides the extra gravitational acceleration which is usually explained
through dark matter. We also predict that gravitational lensing observations
can possibly discriminate between the proposed higher dimensional effects and
dark matter, the deflection angles predicted in the proposed scenario being
around 75% to 80% of the usual predictions based on dark matter.
| [
{
"created": "Mon, 6 Sep 2004 09:51:36 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Pal",
"Supratik",
"",
"IIT Kharagpur, India"
],
[
"Bharadwaj",
"Somnath",
"",
"IIT Kharagpur, India"
],
[
"Kar",
"Sayan",
"",
"IIT Kharagpur, India"
]
] | In the braneworld scenario, the four dimensional effective Einstein equation has extra terms which arise from the embedding of the 3-brane in the bulk. We show that in this modified theory of gravity, it is possible to model observations of galaxy rotation curves and the X-ray profiles of clusters of galaxies, without the need for dark matter. In this scenario, a traceless tensor field which arises from the projection of the bulk Weyl tensor on the brane, provides the extra gravitational acceleration which is usually explained through dark matter. We also predict that gravitational lensing observations can possibly discriminate between the proposed higher dimensional effects and dark matter, the deflection angles predicted in the proposed scenario being around 75% to 80% of the usual predictions based on dark matter. |
1407.7742 | Taeyoon Moon | Yun Soo Myung and Taeyoon Moon | Cosmological singleton gravity theory and dS/LCFT correspondence | 1+18 pages, no figures, published version | JHEP10(2014)137 | 10.1007/JHEP10(2014)137 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of cosmological perturbations generated during de
Sitter inflation in the singleton gravity theory. This theory is composed of a
dipole ghost pair in addition to tensor. We obtain the singleton power spectra
which show that the de Sitter/logarithmic conformal field theory (dS/LCFT)
correspondence works for computing the power spectra in the superhorizon limit.
Also we compute the spectral indices for light singleton which contains a
logarithmic correction.
| [
{
"created": "Tue, 29 Jul 2014 14:42:57 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Oct 2014 02:26:24 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Myung",
"Yun Soo",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We study the evolution of cosmological perturbations generated during de Sitter inflation in the singleton gravity theory. This theory is composed of a dipole ghost pair in addition to tensor. We obtain the singleton power spectra which show that the de Sitter/logarithmic conformal field theory (dS/LCFT) correspondence works for computing the power spectra in the superhorizon limit. Also we compute the spectral indices for light singleton which contains a logarithmic correction. |
0811.4316 | Oleg Zaslavskii | Naresh Dadhich and Oleg B. Zaslavskii | Focusing versus defocusing properties of truly naked black holes | 16 pages. To appear in IJMP D | Int.J.Mod.Phys.D18:1073-1084,2009 | 10.1142/S0218271809014959 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the properties of the congruence of null geodesics propagating near
the so-called truly naked horizons (TNH) - objects having finite Kretschmann
scalar but with diverging tidal acceleration for freely falling observers. The
expansion of outgoing rays near the future horizon always tends to vanish for
the non-extremal case but may be non-zero for the distorted (ultra)extremal
one. It tends to diverge for the ingoing ones if the the null energy condition
(NEC) is satisfied in the vicinity of the horizon outside. However, it also
tends to zero for NEC violating cases except the remote horizons. We also
discuss the validity of test particle approximation for TNHs and find the
sufficient condition for backreaction remaining small.
| [
{
"created": "Wed, 26 Nov 2008 14:06:15 GMT",
"version": "v1"
}
] | 2009-08-25 | [
[
"Dadhich",
"Naresh",
""
],
[
"Zaslavskii",
"Oleg B.",
""
]
] | We study the properties of the congruence of null geodesics propagating near the so-called truly naked horizons (TNH) - objects having finite Kretschmann scalar but with diverging tidal acceleration for freely falling observers. The expansion of outgoing rays near the future horizon always tends to vanish for the non-extremal case but may be non-zero for the distorted (ultra)extremal one. It tends to diverge for the ingoing ones if the the null energy condition (NEC) is satisfied in the vicinity of the horizon outside. However, it also tends to zero for NEC violating cases except the remote horizons. We also discuss the validity of test particle approximation for TNHs and find the sufficient condition for backreaction remaining small. |
2010.13518 | S. Q. Wu | Di Wu, Shuang-Qing Wu, Puxun Wu, Hongwei Yu | Aspects of the dyonic Kerr-Sen-AdS$_4$ black hole and its ultraspinning
version | 12 pages,2 figures, revtex4-1.cls. Title changed; six references
newly-added | Phys. Rev. D 103, 044014 (2021) | 10.1103/PhysRevD.103.044014 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We explore some (especially, thermodynamical) properties of the dyonic
Kerr-Sen-AdS$_4$ black hole and its ultraspinning counterpart, and check
whether or not both black holes satisfy the first law and Bekenstein-Smarr mass
formulas. To this end, new Christodoulou-Ruffini-like squared-mass formulae for
the usual dyonic Kerr-Sen-AdS$_4$ solution and its ultraspinning cousin are
deduced. Similar to the ultraspinning Kerr-Sen-AdS$_4$ black hole case, we
demonstrate that the ultraspinning dyonic Kerr-Sen-AdS$_4$ black hole does not
always violate the reverse isoperimetric inequality (RII) since the value of
the isoperimetric ratio can either be larger/smaller than, or equal to unity,
depending upon the range of the solution parameters, as is the case only with
an electric charge. This property is apparently distinct from that of the
superentropic dyonic Kerr-Newman-AdS$_4$ black hole, which always strictly
violates the RII, although both of them have some similar properties in other
aspects, such as the horizon geometry and conformal boundary.
| [
{
"created": "Fri, 23 Oct 2020 01:42:40 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Dec 2020 05:45:29 GMT",
"version": "v2"
}
] | 2021-02-16 | [
[
"Wu",
"Di",
""
],
[
"Wu",
"Shuang-Qing",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | We explore some (especially, thermodynamical) properties of the dyonic Kerr-Sen-AdS$_4$ black hole and its ultraspinning counterpart, and check whether or not both black holes satisfy the first law and Bekenstein-Smarr mass formulas. To this end, new Christodoulou-Ruffini-like squared-mass formulae for the usual dyonic Kerr-Sen-AdS$_4$ solution and its ultraspinning cousin are deduced. Similar to the ultraspinning Kerr-Sen-AdS$_4$ black hole case, we demonstrate that the ultraspinning dyonic Kerr-Sen-AdS$_4$ black hole does not always violate the reverse isoperimetric inequality (RII) since the value of the isoperimetric ratio can either be larger/smaller than, or equal to unity, depending upon the range of the solution parameters, as is the case only with an electric charge. This property is apparently distinct from that of the superentropic dyonic Kerr-Newman-AdS$_4$ black hole, which always strictly violates the RII, although both of them have some similar properties in other aspects, such as the horizon geometry and conformal boundary. |
1409.4918 | Marcelo Disconzi | Marcelo M. Disconzi, Thomas W. Kephart, Robert J. Scherrer | A New Approach to Cosmological Bulk Viscosity | Text and references expanded. To appear in Physical Review D | Phys. Rev. D 91, 043532 (2015) | 10.1103/PhysRevD.91.043532 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the cosmological consequences of an alternative to the standard
expression for bulk viscosity, one which was proposed to avoid the propagation
of superluminal signals without the necessity of extending the space of
variables of the theory. The Friedmann equation is derived for this case, along
with an expression for the effective pressure. We find solutions for the
evolution of the density of a viscous component, which differs markedly from
the case of conventional Eckart theory; our model evolves toward late-time
phantom-like behavior with a future singularity. Entropy production is
addressed, and some similarities and differences to approaches based on the
Mueller-Israel-Stewart theory are discussed.
| [
{
"created": "Wed, 17 Sep 2014 09:33:53 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Feb 2015 14:34:35 GMT",
"version": "v2"
}
] | 2016-04-08 | [
[
"Disconzi",
"Marcelo M.",
""
],
[
"Kephart",
"Thomas W.",
""
],
[
"Scherrer",
"Robert J.",
""
]
] | We examine the cosmological consequences of an alternative to the standard expression for bulk viscosity, one which was proposed to avoid the propagation of superluminal signals without the necessity of extending the space of variables of the theory. The Friedmann equation is derived for this case, along with an expression for the effective pressure. We find solutions for the evolution of the density of a viscous component, which differs markedly from the case of conventional Eckart theory; our model evolves toward late-time phantom-like behavior with a future singularity. Entropy production is addressed, and some similarities and differences to approaches based on the Mueller-Israel-Stewart theory are discussed. |
1801.03382 | Shaoqi Hou | Yungui Gong, Shaoqi Hou, Dicong Liang, Eleftherios Papantonopoulos | Gravitational waves in Einstein-{\ae}ther and generalized TeVeS theory
after GW170817 | 33 pages, 7 figures | Phys. Rev. D 97, 084040 (2018) | 10.1103/PhysRevD.97.084040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we discuss the polarization contents of Einstein-\ae ther
theory and the generalized tensor-vector-scalar (TeVeS) theory, as both
theories have a normalized timelike vector field. We derive the linearized
equations of motion around the flat spacetime background using the
gauge-invariant variables to easily separate physical degrees of freedom. We
find the plane wave solutions are then found, and identify the polarizations by
examining the geodesic deviation equations. We find that there are five
polarizations in Einstein-\ae ther theory and six polarizations in the
generalized TeVeS theory. In particular, the transverse breathing mode is mixed
with the pure longitudinal mode. We also discuss the experimental tests of the
extra polarizations in Einstein-\ae ther theory using pulsar timing arrays
combined with the gravitational-wave speed bound derived from the observations
on GW 170817 and GRB 170817A. It turns out that it might be difficult to use
pulsar timing arrays to distinguish different polarizations in Einstein-\ae
ther theory. The same speed bound also forces one of the propagating modes in
the generalized TeVeS theory to travel much faster than the speed of light.
Since the strong coupling problem does not exist in some parameter subspaces,
the generalized TeVeS theory is excluded in these parameter subspaces.
| [
{
"created": "Wed, 10 Jan 2018 14:08:36 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Mar 2018 12:10:16 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Apr 2018 13:21:49 GMT",
"version": "v3"
}
] | 2018-04-25 | [
[
"Gong",
"Yungui",
""
],
[
"Hou",
"Shaoqi",
""
],
[
"Liang",
"Dicong",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | In this work, we discuss the polarization contents of Einstein-\ae ther theory and the generalized tensor-vector-scalar (TeVeS) theory, as both theories have a normalized timelike vector field. We derive the linearized equations of motion around the flat spacetime background using the gauge-invariant variables to easily separate physical degrees of freedom. We find the plane wave solutions are then found, and identify the polarizations by examining the geodesic deviation equations. We find that there are five polarizations in Einstein-\ae ther theory and six polarizations in the generalized TeVeS theory. In particular, the transverse breathing mode is mixed with the pure longitudinal mode. We also discuss the experimental tests of the extra polarizations in Einstein-\ae ther theory using pulsar timing arrays combined with the gravitational-wave speed bound derived from the observations on GW 170817 and GRB 170817A. It turns out that it might be difficult to use pulsar timing arrays to distinguish different polarizations in Einstein-\ae ther theory. The same speed bound also forces one of the propagating modes in the generalized TeVeS theory to travel much faster than the speed of light. Since the strong coupling problem does not exist in some parameter subspaces, the generalized TeVeS theory is excluded in these parameter subspaces. |
1508.05120 | Christian Boehmer | Sebastian Bahamonde, Christian G. Boehmer, Matthew Wright | Modified teleparallel theories of gravity | 9 pages, 1 figure; some typos fixed, slightly improved notation | Phys. Rev. D 92, 104042 (2015) | 10.1103/PhysRevD.92.104042 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate modified theories of gravity in the context of teleparallel
geometries. It is well known that modified gravity models based on the torsion
scalar are not invariant under local Lorentz transformations while
modifications based on the Ricci scalar are. This motivates the study of a
model depending on the torsion scalar and the divergence of the torsion vector.
We derive the teleparallel equivalent of $f(R)$ gravity as a particular subset
of these models and also show that this is the unique theory in this class that
is invariant under local Lorentz transformation. Furthermore one can show that
$f(T)$ gravity is the unique theory admitting second order field equations.
| [
{
"created": "Thu, 20 Aug 2015 20:50:36 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2015 10:29:12 GMT",
"version": "v2"
}
] | 2015-11-30 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Boehmer",
"Christian G.",
""
],
[
"Wright",
"Matthew",
""
]
] | We investigate modified theories of gravity in the context of teleparallel geometries. It is well known that modified gravity models based on the torsion scalar are not invariant under local Lorentz transformations while modifications based on the Ricci scalar are. This motivates the study of a model depending on the torsion scalar and the divergence of the torsion vector. We derive the teleparallel equivalent of $f(R)$ gravity as a particular subset of these models and also show that this is the unique theory in this class that is invariant under local Lorentz transformation. Furthermore one can show that $f(T)$ gravity is the unique theory admitting second order field equations. |
gr-qc/0112077 | Christos G. Tsagas | Christos G Tsagas (Univ. of Portsmouth/Univ. of Cape Town) | Geometrical Aspects of Cosmic Magnetic Fields | To appear in proceedings of the 2nd Hellenic Cosmology Workshop,
Athens 2001 (Kluwer-ASSL series) | null | 10.1007/978-94-010-0622-4_4 | null | gr-qc astro-ph | null | We discuss how the vector nature of magnetic fields, and the geometrical
interpretation of gravity introduced by general relativity, lead to a special
coupling between magnetism and spacetime curvature. This magneto-geometrical
interaction effectively transfers the tension properties of the field into the
spacetime fabric, triggering a variety of effects with potentially far-reaching
implications.
| [
{
"created": "Sat, 29 Dec 2001 12:16:06 GMT",
"version": "v1"
}
] | 2017-01-25 | [
[
"Tsagas",
"Christos G",
"",
"Univ. of Portsmouth/Univ. of Cape Town"
]
] | We discuss how the vector nature of magnetic fields, and the geometrical interpretation of gravity introduced by general relativity, lead to a special coupling between magnetism and spacetime curvature. This magneto-geometrical interaction effectively transfers the tension properties of the field into the spacetime fabric, triggering a variety of effects with potentially far-reaching implications. |
2304.12407 | Guillermo Palma Prof. Dr. | Norman Cruz, Gabriel Gomez, Esteban Gonzalez, Guillermo Palma and
Angel Rincon | Exploring Models of Running Vacuum Energy with Viscous Dark Matter from
a Dynamical System Perspective | 26 pages and 13 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Running vacuum models and viscous dark matter scenarios beyond perfect fluid
idealization are two appealing theoretical strategies that have been separately
studied as alternatives to solve some problems rooted in the $\Lambda$CDM
cosmological model. In this paper, we combine these two notions in a single
cosmological setting and investigate their cosmological implications, paying
particular attention in the interplay between these two constituents in
different cosmological periods. Specifically, we consider a well-studied
running vacuum model inspired by renormalization group, and a recently proposed
general parameterization for the bulk viscosity $\xi$. By employing dynamical
system analysis, we explore the physical aspects of the new phase space that
emerges from the combined models and derive stability conditions that ensure
complete cosmological dynamics. We identify four distinct classes of models and
find that the critical points of the phase space are non-trivially renewed
compared to the single scenarios. We then proceed, in a joint and complementary
way to the dynamical system analysis, with a detailed numerical exploration to
quantify the impact of both the running parameter and the bulk viscosity
coefficient on the cosmological evolution. Thus, for some values of the model
parameters, numerical solutions show qualitative differences from the
$\Lambda$CDM model, which is phenomenologically appealing in light of
cosmological observations.
| [
{
"created": "Mon, 24 Apr 2023 19:38:04 GMT",
"version": "v1"
}
] | 2023-04-26 | [
[
"Cruz",
"Norman",
""
],
[
"Gomez",
"Gabriel",
""
],
[
"Gonzalez",
"Esteban",
""
],
[
"Palma",
"Guillermo",
""
],
[
"Rincon",
"Angel",
""
]
] | Running vacuum models and viscous dark matter scenarios beyond perfect fluid idealization are two appealing theoretical strategies that have been separately studied as alternatives to solve some problems rooted in the $\Lambda$CDM cosmological model. In this paper, we combine these two notions in a single cosmological setting and investigate their cosmological implications, paying particular attention in the interplay between these two constituents in different cosmological periods. Specifically, we consider a well-studied running vacuum model inspired by renormalization group, and a recently proposed general parameterization for the bulk viscosity $\xi$. By employing dynamical system analysis, we explore the physical aspects of the new phase space that emerges from the combined models and derive stability conditions that ensure complete cosmological dynamics. We identify four distinct classes of models and find that the critical points of the phase space are non-trivially renewed compared to the single scenarios. We then proceed, in a joint and complementary way to the dynamical system analysis, with a detailed numerical exploration to quantify the impact of both the running parameter and the bulk viscosity coefficient on the cosmological evolution. Thus, for some values of the model parameters, numerical solutions show qualitative differences from the $\Lambda$CDM model, which is phenomenologically appealing in light of cosmological observations. |
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