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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9806098 | Scott Foster | S. Foster | Scalar Field Cosmologies and the Initial Space-Time Singularity | 31 pages, 3 figures | Class.Quant.Grav. 15 (1998) 3485-3504 | 10.1088/0264-9381/15/11/014 | ADP-98-26/M66 | gr-qc | null | The singularity structure of cosmological models whose matter content
consists of a scalar field with arbitrary non-negative potential is discussed.
The special case of spatially flat FRW space-time is analysed in detail using a
dynamical systems approach which may readily be generalised to more complicated
space-times. It is shown that for a very large and natural class of models a
simple and regular past asymptotic structure exists. More specifically, there
exists a family of solutions which is in continuous 1-1 correspondence with the
exactly integrable massless scalar field cosmologies, this correspondence being
realised by a unique asymptotic approximation. The set of solutions which do
not fall into this class has measure zero. The significance of this result to
the cosmological initial value problem is briefly discussed.
| [
{
"created": "Thu, 25 Jun 1998 10:41:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Foster",
"S.",
""
]
] | The singularity structure of cosmological models whose matter content consists of a scalar field with arbitrary non-negative potential is discussed. The special case of spatially flat FRW space-time is analysed in detail using a dynamical systems approach which may readily be generalised to more complicated space-times. It is shown that for a very large and natural class of models a simple and regular past asymptotic structure exists. More specifically, there exists a family of solutions which is in continuous 1-1 correspondence with the exactly integrable massless scalar field cosmologies, this correspondence being realised by a unique asymptotic approximation. The set of solutions which do not fall into this class has measure zero. The significance of this result to the cosmological initial value problem is briefly discussed. |
2101.04153 | Anton Kapustin | Anton Kapustin, Marc Touraev | Non-relativistic Geometry and the Equivalence Principle | 11 pages. v2: version published in Classical and Quantum Gravity | Classical and Quantum Gravity 38, 135003 (2021) | 10.1088/1361-6382/abfea5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a geometric and symmetry-based formulation of the equivalence
principle in non-relativistic physics. It applies both on the classical and
quantum levels and states that the Newtonian potential can be eliminated in
favor of a curved and time-dependent spatial metric. It is this requirement
that forces the gravitational mass to be equal to the inertial mass. We
identify the symmetry responsible for the equivalence principle as the remnant
of time-reparameterization symmetry of the relativistic theory. We also clarify
the transformation properties of the Schroedinger wave-function under arbitrary
changes of frame.
| [
{
"created": "Mon, 11 Jan 2021 19:30:08 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Jul 2021 23:51:49 GMT",
"version": "v2"
}
] | 2021-07-13 | [
[
"Kapustin",
"Anton",
""
],
[
"Touraev",
"Marc",
""
]
] | We describe a geometric and symmetry-based formulation of the equivalence principle in non-relativistic physics. It applies both on the classical and quantum levels and states that the Newtonian potential can be eliminated in favor of a curved and time-dependent spatial metric. It is this requirement that forces the gravitational mass to be equal to the inertial mass. We identify the symmetry responsible for the equivalence principle as the remnant of time-reparameterization symmetry of the relativistic theory. We also clarify the transformation properties of the Schroedinger wave-function under arbitrary changes of frame. |
2406.16545 | Andrei Galiautdinov | Andrei Galiautdinov | Canonical quantization of the dark Dirac field and time asymmetry | 8 pages, no figures; typos corrected, supersymmetric extension
proposed | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform canonical quantization of the single-component, spin-zero field
that was introduced by Dirac in 1971 and recently suggested as a candidate for
dark matter by Bogomolny. The massive and massless cases are treated
separately. Since in the massive case only positive-frequency modes are
normalizable and regarded as physical, the mode expansion for the field
involves annihilation operators only, making the quantization procedure
particularly simple. The corresponding Hamiltonian turns out to be unambiguous,
with no need for normal ordering. The positive-energy requirement imposed on
the second-quantized system leads to equally acceptable Bose and Fermi choices
for particle statistics. This suggests supersymmetric extension of original
Dirac's theory in which Bose and Fermi single-component positive-energy Dirac
fields are combined into a doublet whose members can transform into each other.
Our model includes a Landau-Anderson-Higgs type potential which allows
spontaneous selection of the universe with a given bose-to-fermi ratio of the
positive-energy Dirac particles. The bosonic sector of proposed extension hints
at the possibility of a dark, background Bose-Einstein condensate that endows
the universe with its cosmological temporal asymmetry. In the massless case of
Dirac's original theory, we explore the possibility of allowing the field
expansion to involve both positive- and negative-frequency modes. This leads to
the anticommutation relations for creation and annihilation operators
associated with the negative energy solutions, resulting in supersymmetric
behavior of the single-component field in the ultrarelativistic limit. Finally,
we speculate on the possibility for the positive-energy Dirac particles to obey
some exotic (such as non-abelian, Clifford) statistics in which the particles
are neither created nor destroyed.
| [
{
"created": "Mon, 24 Jun 2024 11:29:57 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jul 2024 13:47:11 GMT",
"version": "v2"
}
] | 2024-07-02 | [
[
"Galiautdinov",
"Andrei",
""
]
] | We perform canonical quantization of the single-component, spin-zero field that was introduced by Dirac in 1971 and recently suggested as a candidate for dark matter by Bogomolny. The massive and massless cases are treated separately. Since in the massive case only positive-frequency modes are normalizable and regarded as physical, the mode expansion for the field involves annihilation operators only, making the quantization procedure particularly simple. The corresponding Hamiltonian turns out to be unambiguous, with no need for normal ordering. The positive-energy requirement imposed on the second-quantized system leads to equally acceptable Bose and Fermi choices for particle statistics. This suggests supersymmetric extension of original Dirac's theory in which Bose and Fermi single-component positive-energy Dirac fields are combined into a doublet whose members can transform into each other. Our model includes a Landau-Anderson-Higgs type potential which allows spontaneous selection of the universe with a given bose-to-fermi ratio of the positive-energy Dirac particles. The bosonic sector of proposed extension hints at the possibility of a dark, background Bose-Einstein condensate that endows the universe with its cosmological temporal asymmetry. In the massless case of Dirac's original theory, we explore the possibility of allowing the field expansion to involve both positive- and negative-frequency modes. This leads to the anticommutation relations for creation and annihilation operators associated with the negative energy solutions, resulting in supersymmetric behavior of the single-component field in the ultrarelativistic limit. Finally, we speculate on the possibility for the positive-energy Dirac particles to obey some exotic (such as non-abelian, Clifford) statistics in which the particles are neither created nor destroyed. |
gr-qc/9908018 | Sameer Gupta | Sameer Gupta | Causality in Spin Foam Models | 19 pages, LaTeX2e, many eps figures | Phys.Rev. D61 (2000) 064014 | 10.1103/PhysRevD.61.064014 | null | gr-qc | null | We compute Teitelboim's causal propagator in the context of canonical loop
quantum gravity. For the Lorentzian signature, we find that the resultant power
series can be expressed as a sum over branched, colored two-surfaces with an
intrinsic causal structure. This leads us to define a general structure which
we call a ``causal spin foam''. We also demonstrate that the causal evolution
models for spin networks fall in the general class of causal spin foams.
| [
{
"created": "Thu, 5 Aug 1999 22:12:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gupta",
"Sameer",
""
]
] | We compute Teitelboim's causal propagator in the context of canonical loop quantum gravity. For the Lorentzian signature, we find that the resultant power series can be expressed as a sum over branched, colored two-surfaces with an intrinsic causal structure. This leads us to define a general structure which we call a ``causal spin foam''. We also demonstrate that the causal evolution models for spin networks fall in the general class of causal spin foams. |
1004.0998 | Jacob Slutsky | J. Slutsky, L. Blackburn, D. A. Brown, L. Cadonati, J. Cain, M.
Cavagli\`a, S. Chatterji, N. Christensen, M. Coughlin, S. Desai, G.
Gonz\'alez, T. Isogai, E. Katsavounidis, B. Rankins, T. Reed, K. Riles, P.
Shawhan, J. R. Smith, N. Zotov, J. Zweizig | Methods for Reducing False Alarms in Searches for Compact Binary
Coalescences in LIGO Data | null | Class.Quant.Grav.27:165023,2010 | 10.1088/0264-9381/27/16/165023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LIGO detectors are sensitive to a variety of noise transients of
non-astrophysical origin. Instrumental glitches and environmental disturbances
increase the false alarm rate in the searches for gravitational waves. Using
times already identified when the interferometers produced data of questionable
quality, or when the channels that monitor the interferometer indicated
non-stationarity, we have developed techniques to safely and effectively veto
false triggers from the compact binary coalescences (CBCs) search pipeline.
| [
{
"created": "Wed, 7 Apr 2010 03:50:12 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Apr 2010 16:16:00 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Slutsky",
"J.",
""
],
[
"Blackburn",
"L.",
""
],
[
"Brown",
"D. A.",
""
],
[
"Cadonati",
"L.",
""
],
[
"Cain",
"J.",
""
],
[
"Cavaglià",
"M.",
""
],
[
"Chatterji",
"S.",
""
],
[
"Christensen",
"N.",
""
],
[
"Coughlin",
"M.",
""
],
[
"Desai",
"S.",
""
],
[
"González",
"G.",
""
],
[
"Isogai",
"T.",
""
],
[
"Katsavounidis",
"E.",
""
],
[
"Rankins",
"B.",
""
],
[
"Reed",
"T.",
""
],
[
"Riles",
"K.",
""
],
[
"Shawhan",
"P.",
""
],
[
"Smith",
"J. R.",
""
],
[
"Zotov",
"N.",
""
],
[
"Zweizig",
"J.",
""
]
] | The LIGO detectors are sensitive to a variety of noise transients of non-astrophysical origin. Instrumental glitches and environmental disturbances increase the false alarm rate in the searches for gravitational waves. Using times already identified when the interferometers produced data of questionable quality, or when the channels that monitor the interferometer indicated non-stationarity, we have developed techniques to safely and effectively veto false triggers from the compact binary coalescences (CBCs) search pipeline. |
1507.05047 | Hermano Velten | Jose Beltran Jimenez, Federico Piazza and Hermano Velten | Piercing the Vainshtein screen with anomalous gravitational wave speed:
Constraints on modified gravity from binary pulsars | v3: typos corrected. Final version to appear on PRL | Phys. Rev. Lett. 116, 061101 (2016) | 10.1103/PhysRevLett.116.061101 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using observations of the Hulse-Taylor pulsar we constrain the
gravitational wave (GW) speed to the level of $10^{-2}$. We apply this result
to scalar-tensor theories that generalize Galileon 4 and 5 models, which
display anomalous propagation speed and coupling to matter for GWs. We argue
that this effect survives conventional screening due to the persistence of a
scalar field gradient inside virialized overdensities, which effectively
"pierces" the Vainshtein screening. In specific branches of solutions, our
result allows to directly constrain the cosmological couplings in the effective
field theory of dark energy formalism.
| [
{
"created": "Fri, 17 Jul 2015 19:26:45 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Sep 2015 08:42:10 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Jan 2016 13:19:44 GMT",
"version": "v3"
}
] | 2016-02-17 | [
[
"Jimenez",
"Jose Beltran",
""
],
[
"Piazza",
"Federico",
""
],
[
"Velten",
"Hermano",
""
]
] | By using observations of the Hulse-Taylor pulsar we constrain the gravitational wave (GW) speed to the level of $10^{-2}$. We apply this result to scalar-tensor theories that generalize Galileon 4 and 5 models, which display anomalous propagation speed and coupling to matter for GWs. We argue that this effect survives conventional screening due to the persistence of a scalar field gradient inside virialized overdensities, which effectively "pierces" the Vainshtein screening. In specific branches of solutions, our result allows to directly constrain the cosmological couplings in the effective field theory of dark energy formalism. |
gr-qc/9408040 | Parthasarathi Mitra | A. Ghosh and P. Mitra | General form of thermodynamical entropy for black hole | LaTeX, 6 pages; published version | Mod.Phys.Lett.A11:1231-1234,1996 | 10.1142/S0217732396001247 | null | gr-qc hep-th | null | The entropy of a black hole can be different from a quarter of the area even
at the semiclassical level.
| [
{
"created": "Wed, 31 Aug 1994 10:57:00 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jun 1997 11:52:03 GMT",
"version": "v2"
}
] | 2010-11-01 | [
[
"Ghosh",
"A.",
""
],
[
"Mitra",
"P.",
""
]
] | The entropy of a black hole can be different from a quarter of the area even at the semiclassical level. |
2407.03077 | Eftychios Kaimakkamis | Eftychios Kaimakkamis and Karunava Sil | A formalism for the ambiguities of the Wheeler-DeWitt equation | Based on presentation at Corfu Summer Institute 2023 "School and
Workshops on Elementary Particle Physics and Gravity"(CORFU2023), 10
pages+references | null | 10.22323/1.463.0227 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study ambiguities in the precise formulation of the Wheeler-DeWitt
equation for the wavefunction of the Universe that arise due to different
operator orderings in the quantum Hamiltonian. We first examine the simpler
case of the 1-dimensional minisuperspace model and derive the inner product
measure that renders the Hamiltonian hermitian. Based on this, we establish
that the Hilbert space inner products and quantum probabilities are universal,
free of any ambiguities, at the semiclassical level. Recasting the
Wheeler-DeWitt equation in a form invariant under field redefinitions of the
minisuperspace variable, we show that all ambiguity functions are contained in
a higher order scalar function, which can be used to define classes of models
with universal predictions to all orders in $\hbar$. We then generalize to
minisuperspace models of arbitrary dimension, upon the inclusion of an
arbitrary number of scalar matter fields. We show that the hermiticity of the
Hamiltonian in these cases provides a set of constraints, which can be used to
cast the WDW equation in a covariant form and establish the universality of the
inner products at the semiclassical level. In these cases as well, all
ambiguity functions appear in a higher order scalar function of the
minisuperspace manifold, which leads to distinct universality classes.
| [
{
"created": "Wed, 3 Jul 2024 12:52:22 GMT",
"version": "v1"
}
] | 2024-08-13 | [
[
"Kaimakkamis",
"Eftychios",
""
],
[
"Sil",
"Karunava",
""
]
] | We study ambiguities in the precise formulation of the Wheeler-DeWitt equation for the wavefunction of the Universe that arise due to different operator orderings in the quantum Hamiltonian. We first examine the simpler case of the 1-dimensional minisuperspace model and derive the inner product measure that renders the Hamiltonian hermitian. Based on this, we establish that the Hilbert space inner products and quantum probabilities are universal, free of any ambiguities, at the semiclassical level. Recasting the Wheeler-DeWitt equation in a form invariant under field redefinitions of the minisuperspace variable, we show that all ambiguity functions are contained in a higher order scalar function, which can be used to define classes of models with universal predictions to all orders in $\hbar$. We then generalize to minisuperspace models of arbitrary dimension, upon the inclusion of an arbitrary number of scalar matter fields. We show that the hermiticity of the Hamiltonian in these cases provides a set of constraints, which can be used to cast the WDW equation in a covariant form and establish the universality of the inner products at the semiclassical level. In these cases as well, all ambiguity functions appear in a higher order scalar function of the minisuperspace manifold, which leads to distinct universality classes. |
1806.07295 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Dynamical Systems Perspective of Cosmological Finite-time Singularities
in $f(R)$ Gravity and Interacting Multifluid Cosmology | PRD Accepted | null | 10.1103/PhysRevD.98.024013 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we shall investigate the occurrence of future cosmological
finite-time singularities in the dynamical system corresponding to two
cosmological theories, namely that of vacuum $f(R)$ gravity and that of three
fluids. The vacuum $f(R)$ gravity is an example for which the variables we will
choose to quantify the phase space dynamics, do not necessarily blow-up near a
cosmological singularity. After appropriately choosing the variables, we shall
investigate the behavior of the corresponding dynamical system near some types
of cosmological finite-time singularities, for some limiting cases in which we
can produce analytic solutions for the dynamical variables. The most
interesting case from both a mathematical and physical point of view, is the
Big Rip case, and particularly in the limiting case of a very strong
singularity. The physically appealing outcome is that the resulting
non-autonomous dynamical system is attracted asymptotically to an accelerating
attractor solution, with equation of state parameter $w_{eff}=-1$. Our analytic
results, show that an extremely strong Big Rip singularity in vacuum $f(R)$
gravity theories is always related to an accelerating solution, or tends to
acceleration. The converse statement though may not be true. The second
cosmology we shall study is a multifluid cosmology, consisting of three fluids,
the interacting dark matter and dark energy fluids, and the baryonic fluid. By
appropriately choosing the variables, we will show that the dynamical system
can become an autonomous polynomial dynamical system, in which case, by using a
dominant balance analysis, we shall investigate the occurrence of finite-time
singularities in this system.
| [
{
"created": "Tue, 19 Jun 2018 14:55:59 GMT",
"version": "v1"
}
] | 2018-08-01 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | In this work we shall investigate the occurrence of future cosmological finite-time singularities in the dynamical system corresponding to two cosmological theories, namely that of vacuum $f(R)$ gravity and that of three fluids. The vacuum $f(R)$ gravity is an example for which the variables we will choose to quantify the phase space dynamics, do not necessarily blow-up near a cosmological singularity. After appropriately choosing the variables, we shall investigate the behavior of the corresponding dynamical system near some types of cosmological finite-time singularities, for some limiting cases in which we can produce analytic solutions for the dynamical variables. The most interesting case from both a mathematical and physical point of view, is the Big Rip case, and particularly in the limiting case of a very strong singularity. The physically appealing outcome is that the resulting non-autonomous dynamical system is attracted asymptotically to an accelerating attractor solution, with equation of state parameter $w_{eff}=-1$. Our analytic results, show that an extremely strong Big Rip singularity in vacuum $f(R)$ gravity theories is always related to an accelerating solution, or tends to acceleration. The converse statement though may not be true. The second cosmology we shall study is a multifluid cosmology, consisting of three fluids, the interacting dark matter and dark energy fluids, and the baryonic fluid. By appropriately choosing the variables, we will show that the dynamical system can become an autonomous polynomial dynamical system, in which case, by using a dominant balance analysis, we shall investigate the occurrence of finite-time singularities in this system. |
2002.03599 | German Sharov | G. S. Sharov and E. S. Sinyakov | Cosmological models, observational data and tension in Hubble constant | 15 pages, 6 figures, submitted to Mathematical Modelling and
Geometry, | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze how predictions of cosmological models depend on a choice of
described observational data, restrictions on flatness,
and how this choice can alleviate the $H_0$ tension. These effects are
demonstrated in the $w$CDM model in comparison with the standard $\Lambda$CDM
model. We describe the Pantheon sample observations of Type Ia supernovae, 31
Hubble parameter data points $H(z)$ from cosmic chronometers, the extended
sample with 57 $H(z)$ data points and observational manifestations of cosmic
microwave background radiation (CMB).
For the $w$CDM and $\Lambda$CDM models in the flat case and with spatial
curvature we calculate $\chi^2$ functions for all observed data in different
combinations, estimate optimal values of model parameters and their expected
intervals. For both considered models the results essentially depend on a
choice of data sets. In particular, for the $w$CDM model with $H(z)$ data,
supernovae and CMB the $1\sigma$ estimations may vary from
$H_0=67.52^{+0.96}_{-0.95}$ km\,/(s$\cdot$Mpc) (for all $N_H=57$ Hubble
parameter data points) up to $H_0=70.87^{+1.63}_{-1.62}$ km\,/(s$\cdot$Mpc) for
the flat case ($k=0$) and $N_H=31$. These results might be a hint how to
alleviate the problem of $H_0$ tension: different estimates of the Hubble
constant may be connected with filters and a choice of observational data.
| [
{
"created": "Mon, 10 Feb 2020 08:31:26 GMT",
"version": "v1"
}
] | 2020-02-11 | [
[
"Sharov",
"G. S.",
""
],
[
"Sinyakov",
"E. S.",
""
]
] | We analyze how predictions of cosmological models depend on a choice of described observational data, restrictions on flatness, and how this choice can alleviate the $H_0$ tension. These effects are demonstrated in the $w$CDM model in comparison with the standard $\Lambda$CDM model. We describe the Pantheon sample observations of Type Ia supernovae, 31 Hubble parameter data points $H(z)$ from cosmic chronometers, the extended sample with 57 $H(z)$ data points and observational manifestations of cosmic microwave background radiation (CMB). For the $w$CDM and $\Lambda$CDM models in the flat case and with spatial curvature we calculate $\chi^2$ functions for all observed data in different combinations, estimate optimal values of model parameters and their expected intervals. For both considered models the results essentially depend on a choice of data sets. In particular, for the $w$CDM model with $H(z)$ data, supernovae and CMB the $1\sigma$ estimations may vary from $H_0=67.52^{+0.96}_{-0.95}$ km\,/(s$\cdot$Mpc) (for all $N_H=57$ Hubble parameter data points) up to $H_0=70.87^{+1.63}_{-1.62}$ km\,/(s$\cdot$Mpc) for the flat case ($k=0$) and $N_H=31$. These results might be a hint how to alleviate the problem of $H_0$ tension: different estimates of the Hubble constant may be connected with filters and a choice of observational data. |
1611.09720 | Oliver Porth | Oliver Porth, Hector Olivares, Yosuke Mizuno, Ziri Younsi, Luciano
Rezzolla, Monika Moscibrodzka, Heino Falcke and Michael Kramer | The Black Hole Accretion Code | revised version accepted for publication by Computational
Astrophysics and Cosmology. Some figures have been down-sampled | null | 10.1186/s40668-017-0020-2 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the black hole accretion code (BHAC), a new multidimensional
general-relativistic magnetohydrodynamics module for the MPI-AMRVAC framework.
BHAC has been designed to solve the equations of ideal general-relativistic
magnetohydrodynamics in arbitrary spacetimes and exploits adaptive mesh
refinement techniques with an efficient block-based approach. Several
spacetimes have already been implemented and tested. We demonstrate the
validity of BHAC by means of various one-, two-, and three-dimensional test
problems, as well as through a close comparison with the HARM3D code in the
case of a torus accreting onto a black hole. The convergence of a turbulent
accretion scenario is investigated with several diagnostics and we find
accretion rates and horizon-penetrating fluxes to be convergent to within a few
percent when the problem is run in three dimensions. Our analysis also involves
the study of the corresponding thermal synchrotron emission, which is performed
by means of a new general-relativistic radiative transfer code, BHOSS. The
resulting synthetic intensity maps of accretion onto black holes are found to
be convergent with increasing resolution and are anticipated to play a crucial
role in the interpretation of horizon-scale images resulting from upcoming
radio observations of the source at the Galactic Center.
| [
{
"created": "Tue, 29 Nov 2016 16:49:49 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Jun 2017 17:54:44 GMT",
"version": "v2"
}
] | 2017-06-20 | [
[
"Porth",
"Oliver",
""
],
[
"Olivares",
"Hector",
""
],
[
"Mizuno",
"Yosuke",
""
],
[
"Younsi",
"Ziri",
""
],
[
"Rezzolla",
"Luciano",
""
],
[
"Moscibrodzka",
"Monika",
""
],
[
"Falcke",
"Heino",
""
],
[
"Kramer",
"Michael",
""
]
] | We present the black hole accretion code (BHAC), a new multidimensional general-relativistic magnetohydrodynamics module for the MPI-AMRVAC framework. BHAC has been designed to solve the equations of ideal general-relativistic magnetohydrodynamics in arbitrary spacetimes and exploits adaptive mesh refinement techniques with an efficient block-based approach. Several spacetimes have already been implemented and tested. We demonstrate the validity of BHAC by means of various one-, two-, and three-dimensional test problems, as well as through a close comparison with the HARM3D code in the case of a torus accreting onto a black hole. The convergence of a turbulent accretion scenario is investigated with several diagnostics and we find accretion rates and horizon-penetrating fluxes to be convergent to within a few percent when the problem is run in three dimensions. Our analysis also involves the study of the corresponding thermal synchrotron emission, which is performed by means of a new general-relativistic radiative transfer code, BHOSS. The resulting synthetic intensity maps of accretion onto black holes are found to be convergent with increasing resolution and are anticipated to play a crucial role in the interpretation of horizon-scale images resulting from upcoming radio observations of the source at the Galactic Center. |
1712.05960 | Martin Bojowald | Martin Bojowald | Symmetries of space-time | 6 pages, based on an invited talk given at the Centennial Workshop on
General Relativity, Mexican GR Society, Guanajuato, Mexico, November 2015 | Int. J. Mod. Phys. D 25 (2016) 1644007 | 10.1142/S0218271816440077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The equations of Hamiltonian gravity are often considered ugly cousins of the
elegant and manifestly covariant versions found in the Lagrangian theory.
However, both formulations are fundamental in their own rights because they
make different statements about the nature of space-time and its symmetries.
These implications, along with the history of their derivation and an
introduction of recent mathematical support, are discussed here.
| [
{
"created": "Sat, 16 Dec 2017 13:45:16 GMT",
"version": "v1"
}
] | 2017-12-27 | [
[
"Bojowald",
"Martin",
""
]
] | The equations of Hamiltonian gravity are often considered ugly cousins of the elegant and manifestly covariant versions found in the Lagrangian theory. However, both formulations are fundamental in their own rights because they make different statements about the nature of space-time and its symmetries. These implications, along with the history of their derivation and an introduction of recent mathematical support, are discussed here. |
gr-qc/0406119 | Tekin Dereli | H. Cebeci, T. Dereli | Axi-Dilaton Gravity in D \geq 4 Dimensional Space-Times with Torsion | null | Phys.Rev.D71:024016,2005 | 10.1103/PhysRevD.71.024016 | null | gr-qc | null | We study models of axi-dilaton gravity in space-time geometries with torsion.
We discuss conformal re-scaling rules in both Riemannian and non-Riemannian
formulations. We give static, spherically symmetric solutions and examine their
singularity structure.
| [
{
"created": "Wed, 30 Jun 2004 08:52:54 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Cebeci",
"H.",
""
],
[
"Dereli",
"T.",
""
]
] | We study models of axi-dilaton gravity in space-time geometries with torsion. We discuss conformal re-scaling rules in both Riemannian and non-Riemannian formulations. We give static, spherically symmetric solutions and examine their singularity structure. |
1009.3267 | Piero Nicolini | Piero Nicolini and Benjamin Niedner | Hausdorff dimension of a particle path in a quantum manifold | 7 pages, 4 figure, updated version which matches that published on
Physical Review D | Phys.Rev.D83:024017,2011 | 10.1103/PhysRevD.83.024017 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After recalling the concept of the Hausdorff dimension, we study the fractal
properties of a quantum particle path. As a novelty we consider the possibility
for the space where the particle propagates to be endowed with a
quantum-gravity-induced minimal length. We show that the Hausdorff dimension
accounts for both the quantum mechanics uncertainty and manifold fluctuations.
In addition the presence of a minimal length breaks the self-similarity
property of the erratic path of the quantum particle. Finally we establish a
universal property of the Hausdorff dimension as well as the spectral
dimension: They both depend on the amount of resolution loss which affects both
the path and the manifold when quantum gravity fluctuations occur.
| [
{
"created": "Thu, 16 Sep 2010 20:00:04 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jan 2011 15:24:49 GMT",
"version": "v2"
}
] | 2011-01-26 | [
[
"Nicolini",
"Piero",
""
],
[
"Niedner",
"Benjamin",
""
]
] | After recalling the concept of the Hausdorff dimension, we study the fractal properties of a quantum particle path. As a novelty we consider the possibility for the space where the particle propagates to be endowed with a quantum-gravity-induced minimal length. We show that the Hausdorff dimension accounts for both the quantum mechanics uncertainty and manifold fluctuations. In addition the presence of a minimal length breaks the self-similarity property of the erratic path of the quantum particle. Finally we establish a universal property of the Hausdorff dimension as well as the spectral dimension: They both depend on the amount of resolution loss which affects both the path and the manifold when quantum gravity fluctuations occur. |
2110.06056 | Susmita Jana | Susmita Jana, S. Shankaranarayanan (IIT Bombay) | Non-minimally coupled electromagnetic fields and observable implications
for primordial black holes | 37 pages, 3 figures, accepted in Universe as part of the Special
Issue 'Open Questions in Black Hole Physics' | Universe 10(7), 270 (2024) | 10.3390/universe10070270 | null | gr-qc astro-ph.CO astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | General relativity (GR) postulates have been verified with high precision,
yet our understanding of how gravity interacts with matter fields remains
incomplete. Various modifications to GR have been proposed in both classical
and quantum realms to address these interactions within the strong gravity
regime. One such approach is non-minimal coupling (NMC), where the space-time
curvature (scalar and tensor) interacts with matter fields, resulting in matter
fields not following the geodesics. To probe the astrophysical implications of
NMC, in this work, we investigate non-minimally coupled electromagnetic (EM)
fields in the presence of black holes. Specifically, we show that primordial
black holes (PBHs) provide a possible tool to constrain the NMC parameter. PBHs
represent an intriguing cosmological black hole class that does not conform to
the no-hair theorem. We model the PBH as a Sultana--Dyer black hole and compare
it with Schwarzschild. We examine observables such as the radius of the photon
sphere, critical impact parameter, and total deflection angles for
non-minimally coupled photons for Schwarzschild and Sultana--Dyer black holes.
Both the black hole space-times lead to similar constraints on the NMC
parameter. For a PBH of mass $M=10^{-5} M_{\odot}$, the photon sphere will not
be formed for one mode. Hence, the photons forming the photon sphere will be
highly polarized, potentially leading to observable implications.
| [
{
"created": "Tue, 12 Oct 2021 14:58:37 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2024 22:15:43 GMT",
"version": "v2"
}
] | 2024-06-26 | [
[
"Jana",
"Susmita",
"",
"IIT Bombay"
],
[
"Shankaranarayanan",
"S.",
"",
"IIT Bombay"
]
] | General relativity (GR) postulates have been verified with high precision, yet our understanding of how gravity interacts with matter fields remains incomplete. Various modifications to GR have been proposed in both classical and quantum realms to address these interactions within the strong gravity regime. One such approach is non-minimal coupling (NMC), where the space-time curvature (scalar and tensor) interacts with matter fields, resulting in matter fields not following the geodesics. To probe the astrophysical implications of NMC, in this work, we investigate non-minimally coupled electromagnetic (EM) fields in the presence of black holes. Specifically, we show that primordial black holes (PBHs) provide a possible tool to constrain the NMC parameter. PBHs represent an intriguing cosmological black hole class that does not conform to the no-hair theorem. We model the PBH as a Sultana--Dyer black hole and compare it with Schwarzschild. We examine observables such as the radius of the photon sphere, critical impact parameter, and total deflection angles for non-minimally coupled photons for Schwarzschild and Sultana--Dyer black holes. Both the black hole space-times lead to similar constraints on the NMC parameter. For a PBH of mass $M=10^{-5} M_{\odot}$, the photon sphere will not be formed for one mode. Hence, the photons forming the photon sphere will be highly polarized, potentially leading to observable implications. |
1811.06528 | Edward Anderson | Edward Anderson | Shape Theories. II. Compactness Selection Principles | 21 pages, including 1 figure. Minor adjustments | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Shape(-and-scale) spaces - configuration spaces for generalized Kendall-type
Shape(-and-Scale) Theories - are usually not manifolds but stratified
manifolds. While in Kendall's own case - similarity shapes - the shape spaces
are analytically nice - Hausdorff - for the Image Analysis and Computer Vision
cases - affine and projective shapes - they are not: merely Kolmogorov. We now
furthermore characterize these results in terms of whether one is staying
within, or straying outside of, some compactness conditions which provide
protection for nice analytic behaviour. We furthermore list which of the recent
wealth of proposed shape theories lie within these topological-level selection
principles for technical tractability. Most cases are not protected, by which
the merely-Kolmogorov behaviour may be endemic and the range of technically
tractable Shape(-and-Scale) Theories very limited. This is the second of two
great bounds on Shape(-and-Scale) Theories, each of which moreover have major
implications for the Comparative Theory of Background Independence as per
Article III.
| [
{
"created": "Thu, 15 Nov 2018 18:52:03 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Dec 2018 23:54:23 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Jan 2019 15:56:20 GMT",
"version": "v3"
},
{
"created": "Tue, 12 Mar 2019 00:53:51 GMT",
"version": "v4"
}
] | 2019-03-13 | [
[
"Anderson",
"Edward",
""
]
] | Shape(-and-scale) spaces - configuration spaces for generalized Kendall-type Shape(-and-Scale) Theories - are usually not manifolds but stratified manifolds. While in Kendall's own case - similarity shapes - the shape spaces are analytically nice - Hausdorff - for the Image Analysis and Computer Vision cases - affine and projective shapes - they are not: merely Kolmogorov. We now furthermore characterize these results in terms of whether one is staying within, or straying outside of, some compactness conditions which provide protection for nice analytic behaviour. We furthermore list which of the recent wealth of proposed shape theories lie within these topological-level selection principles for technical tractability. Most cases are not protected, by which the merely-Kolmogorov behaviour may be endemic and the range of technically tractable Shape(-and-Scale) Theories very limited. This is the second of two great bounds on Shape(-and-Scale) Theories, each of which moreover have major implications for the Comparative Theory of Background Independence as per Article III. |
gr-qc/0612010 | Yu Zhang | Yu Zhang, Yuanxing Gui, Fei Yu and Fenglin Li | Quasinormal modes of a Schwarzschild black hole surrounded by free
static spherically symmetric quintessence: Electromagnetic perturbations | 6 pages, 3 figures | Gen.Rel.Grav.39:1003-1010,2007 | 10.1007/s10714-007-0434-2 | null | gr-qc | null | In this paper, we evaluated the quasinormal modes of electromagnetic
perturbation in a Schwarzschild black hole surrounded by the static spherically
symmetric quintessence by using the third-order WKB approximation when the
quintessential state parameter $ w_{q}$ in the range of $-1/3<w_{q}<0$. Due to
the presence of quintessence, Maxwell field damps more slowly. And when at
$-1<w_{q}<-1/3$, it is similar to the black hole solution in the ds/Ads
spacetime. The appropriate boundary conditions need to be modified.
| [
{
"created": "Fri, 1 Dec 2006 12:27:36 GMT",
"version": "v1"
},
{
"created": "Tue, 29 May 2007 11:44:07 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Zhang",
"Yu",
""
],
[
"Gui",
"Yuanxing",
""
],
[
"Yu",
"Fei",
""
],
[
"Li",
"Fenglin",
""
]
] | In this paper, we evaluated the quasinormal modes of electromagnetic perturbation in a Schwarzschild black hole surrounded by the static spherically symmetric quintessence by using the third-order WKB approximation when the quintessential state parameter $ w_{q}$ in the range of $-1/3<w_{q}<0$. Due to the presence of quintessence, Maxwell field damps more slowly. And when at $-1<w_{q}<-1/3$, it is similar to the black hole solution in the ds/Ads spacetime. The appropriate boundary conditions need to be modified. |
gr-qc/9712077 | Frank Wilczek | Maulik K. Parikh and Frank Wilczek | An Action for Black Hole Membranes | LaTeX, 30 Pages, minor editorial changes | Phys.Rev. D58 (1998) 064011 | 10.1103/PhysRevD.58.064011 | PUPT-1753 and IASSNS-HEP-97-117 | gr-qc hep-th | null | The membrane paradigm is the remarkable view that, to an external observer, a
black hole appears to behave exactly like a dynamical fluid membrane, obeying
such pre-relativistic equations as Ohm's law and the Navier-Stokes equation. It
has traditionally been derived by manipulating the equations of motion. Here we
provide an action formulation of this picture, clarifying what underlies the
paradigm, and simplifying the derivations. Within this framework, we derive
previous membrane results, and extend them to dyonic black hole solutions. We
discuss how it is that an action can produce dissipative equations. Using a
Euclidean path integral, we show that familiar semi-classical thermodynamic
properties of black holes also emerge from the membrane action. Finally, in a
Hamiltonian description, we establish the validity of a minimum entropy
production principle for black holes.
| [
{
"created": "Wed, 17 Dec 1997 22:15:25 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Mar 1998 20:54:20 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Parikh",
"Maulik K.",
""
],
[
"Wilczek",
"Frank",
""
]
] | The membrane paradigm is the remarkable view that, to an external observer, a black hole appears to behave exactly like a dynamical fluid membrane, obeying such pre-relativistic equations as Ohm's law and the Navier-Stokes equation. It has traditionally been derived by manipulating the equations of motion. Here we provide an action formulation of this picture, clarifying what underlies the paradigm, and simplifying the derivations. Within this framework, we derive previous membrane results, and extend them to dyonic black hole solutions. We discuss how it is that an action can produce dissipative equations. Using a Euclidean path integral, we show that familiar semi-classical thermodynamic properties of black holes also emerge from the membrane action. Finally, in a Hamiltonian description, we establish the validity of a minimum entropy production principle for black holes. |
0906.5078 | Bogus{\l}aw Broda | Bogus{\l}aw Broda, Micha{\l} Szanecki | Vacuum pressure, dark energy and dark matter | 6 pages, 0 figures | ISRN Astronomy and Astrophysics, Volume 2011, Article ID 509836 | 10.5402/2011/509836 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been argued that the correct, i.e. positive, sign of quantum vacuum
energy density, or more properly, negative sign of quantum vacuum pressure,
requires not a very large number, e.g. ~100, of additional, undiscovered
fundamental bosonic particle species, absent in the standard model.
Interpretation of the new particle species in terms of dark matter ones permits
to qualitatively, and even quantitatively, connect all the three concepts given
in the title.
| [
{
"created": "Sat, 27 Jun 2009 13:22:37 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jun 2009 13:43:20 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Aug 2009 13:46:17 GMT",
"version": "v3"
},
{
"created": "Thu, 5 Jan 2012 16:36:11 GMT",
"version": "v4"
}
] | 2012-01-06 | [
[
"Broda",
"Bogusław",
""
],
[
"Szanecki",
"Michał",
""
]
] | It has been argued that the correct, i.e. positive, sign of quantum vacuum energy density, or more properly, negative sign of quantum vacuum pressure, requires not a very large number, e.g. ~100, of additional, undiscovered fundamental bosonic particle species, absent in the standard model. Interpretation of the new particle species in terms of dark matter ones permits to qualitatively, and even quantitatively, connect all the three concepts given in the title. |
0807.3824 | Sergey Vyatchanin | Andrey A. Rakhubovsky and Sergey P. Vyatchanin | Displacement-noise-free gravitational-wave detection with two
Fabry-Perot cavities | 10 pages, 5 figures | Phys.Lett.A373:13-18,2008 | 10.1016/j.physleta.2008.10.088 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose two detuned Fabry-Perot cavities, each pumped through both the
mirrors, positioned in line as a toy model of the gravitational-wave (GW)
detector free from displacement noise of the test masses. It is demonstrated
that the noise of cavity mirrors can be completely excluded in a proper linear
combination of the cavities output signals. This model is illustrated by a
simplified round trip model (without Fabry-Perot cavities). We show that in
low-frequency region the obtained displacement-noise-free response signal is
stronger than the one of the interferometer recently proposed by S.Kawamura and
Y.Chen.
| [
{
"created": "Thu, 24 Jul 2008 09:16:44 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Rakhubovsky",
"Andrey A.",
""
],
[
"Vyatchanin",
"Sergey P.",
""
]
] | We propose two detuned Fabry-Perot cavities, each pumped through both the mirrors, positioned in line as a toy model of the gravitational-wave (GW) detector free from displacement noise of the test masses. It is demonstrated that the noise of cavity mirrors can be completely excluded in a proper linear combination of the cavities output signals. This model is illustrated by a simplified round trip model (without Fabry-Perot cavities). We show that in low-frequency region the obtained displacement-noise-free response signal is stronger than the one of the interferometer recently proposed by S.Kawamura and Y.Chen. |
gr-qc/0401002 | Bahram Mashhoon | Bahram Mashhoon and Paul S. Wesson | Gauge-Dependent Cosmological "Constant" | 14 pages, no figures, expanded version to be published in Class.
Quantum Grav | Class.Quant.Grav. 21 (2004) 3611 | 10.1088/0264-9381/21/14/020 | null | gr-qc astro-ph | null | When the cosmological constant of spacetime is derived from the 5D
induced-matter theory of gravity, we show that a simple gauge transformation
changes it to a variable measure of the vacuum which is infinite at the big
bang and decays to an astrophysically-acceptable value at late epochs. We
outline implications of this for cosmology and galaxy formation.
| [
{
"created": "Thu, 1 Jan 2004 00:29:14 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jun 2004 18:59:06 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Mashhoon",
"Bahram",
""
],
[
"Wesson",
"Paul S.",
""
]
] | When the cosmological constant of spacetime is derived from the 5D induced-matter theory of gravity, we show that a simple gauge transformation changes it to a variable measure of the vacuum which is infinite at the big bang and decays to an astrophysically-acceptable value at late epochs. We outline implications of this for cosmology and galaxy formation. |
2212.12175 | Antony Valentini | Antony Valentini | Beyond the Born rule in quantum gravity | 39 pages. For special issue of Foundations of Physics, 'Pilot-wave
and beyond: Louis de Broglie and David Bohm's quest for a quantum ontology',
ed. A. Drezet | Found. Phys. 53, 6 (2023) | 10.1007/s10701-022-00635-0 | null | gr-qc astro-ph.CO hep-th physics.hist-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have recently developed a new understanding of probability in quantum
gravity. In this paper we provide an overview of this new approach and its
implications. Adopting the de Broglie-Bohm pilot-wave formulation of quantum
physics, we argue that there is no Born rule at the fundamental level of
quantum gravity with a non-normalisable Wheeler-DeWitt wave functional $\Psi$.
Instead the universe is in a perpetual state of quantum nonequilibrium with a
probability density $P\neq\left\vert \Psi\right\vert ^{2}$. Dynamical
relaxation to the Born rule can occur only after the early universe has emerged
into a semiclassical or Schr\"{o}dinger approximation, with a time-dependent
and normalisable wave functional $\psi$, for non-gravitational systems on a
classical spacetime background. In that regime the probability density $\rho$
can relax towards $\left\vert \psi\right\vert ^{2}$ (on a coarse-grained
level). Thus the pilot-wave theory of gravitation supports the hypothesis of
primordial quantum nonequilibrium, with relaxation to the Born rule taking
place soon after the big bang. We also show that quantum-gravitational
corrections to the Schr\"{o}dinger approximation allow quantum nonequilibrium
$\rho\neq\left\vert \psi\right\vert ^{2}$ to be created from a prior
equilibrium ($\rho=\left\vert \psi\right\vert ^{2}$) state. Such effects are
very tiny and difficult to observe in practice.
| [
{
"created": "Fri, 23 Dec 2022 07:15:35 GMT",
"version": "v1"
}
] | 2022-12-26 | [
[
"Valentini",
"Antony",
""
]
] | We have recently developed a new understanding of probability in quantum gravity. In this paper we provide an overview of this new approach and its implications. Adopting the de Broglie-Bohm pilot-wave formulation of quantum physics, we argue that there is no Born rule at the fundamental level of quantum gravity with a non-normalisable Wheeler-DeWitt wave functional $\Psi$. Instead the universe is in a perpetual state of quantum nonequilibrium with a probability density $P\neq\left\vert \Psi\right\vert ^{2}$. Dynamical relaxation to the Born rule can occur only after the early universe has emerged into a semiclassical or Schr\"{o}dinger approximation, with a time-dependent and normalisable wave functional $\psi$, for non-gravitational systems on a classical spacetime background. In that regime the probability density $\rho$ can relax towards $\left\vert \psi\right\vert ^{2}$ (on a coarse-grained level). Thus the pilot-wave theory of gravitation supports the hypothesis of primordial quantum nonequilibrium, with relaxation to the Born rule taking place soon after the big bang. We also show that quantum-gravitational corrections to the Schr\"{o}dinger approximation allow quantum nonequilibrium $\rho\neq\left\vert \psi\right\vert ^{2}$ to be created from a prior equilibrium ($\rho=\left\vert \psi\right\vert ^{2}$) state. Such effects are very tiny and difficult to observe in practice. |
1504.07622 | Norbert Klein | Norbert Klein | Analysis of recent G experiments by a differential version of MOND
theory | 16 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The discrepancy between two recently reported experimental values of the
gravitational constant G was analysed within a differential version of MOND
theory. In contrast to the most commonly accepted interpretation of MOND
theory, it is assumed that only the relative gravitational acceleration between
a test mass and an array of source masses determines the magnitude of post
Newtonian corrections at small magnitudes of acceleration. The analysis was
applied to one of the most recent Cavendish-type gravitational force
experiments, which showed a significant deviation of the measured gravitational
constant from the current CODATA value. A remarkable agreement between the
observed G discrepancy and galaxy rotation curves was revealed by a consistent
extrapolation within the framework of this model. The differential approach
suggests that gravity-induced alterations of the space-time-curvature may
define the magnitude of corrections to Newton's law.
| [
{
"created": "Mon, 27 Apr 2015 20:45:43 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jun 2015 12:44:24 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Jul 2015 16:19:28 GMT",
"version": "v3"
},
{
"created": "Wed, 13 Apr 2016 12:44:00 GMT",
"version": "v4"
}
] | 2016-04-14 | [
[
"Klein",
"Norbert",
""
]
] | The discrepancy between two recently reported experimental values of the gravitational constant G was analysed within a differential version of MOND theory. In contrast to the most commonly accepted interpretation of MOND theory, it is assumed that only the relative gravitational acceleration between a test mass and an array of source masses determines the magnitude of post Newtonian corrections at small magnitudes of acceleration. The analysis was applied to one of the most recent Cavendish-type gravitational force experiments, which showed a significant deviation of the measured gravitational constant from the current CODATA value. A remarkable agreement between the observed G discrepancy and galaxy rotation curves was revealed by a consistent extrapolation within the framework of this model. The differential approach suggests that gravity-induced alterations of the space-time-curvature may define the magnitude of corrections to Newton's law. |
1503.02873 | Jorge Ovalle | Roberto Casadio, Jorge Ovalle, Roldao da Rocha | The Minimal Geometric Deformation Approach Extended | Improved version with new solutions. 11 pages, 4 figures. To be
published in CQG | Class. Quantum Grav. 32 (2015) 215020 | 10.1088/0264-9381/32/21/215020 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The minimal geometric deformation approach was introduced in order to study
the exterior space-time around spherically symmetric self-gravitating systems,
like stars or similar astrophysical objects as well, in the Randall-Sundrum
brane-world framework. A consistent extension of this approach is developed
here, which contains modifications of both the time component and the radial
component of a spherically symmetric metric. A modified Schwarzschild geometry
is obtained as an example of its simplest application, and a new solution
potentially useful to describe stars in the brane-world is also presented.
| [
{
"created": "Tue, 10 Mar 2015 11:43:36 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Sep 2015 14:19:28 GMT",
"version": "v2"
}
] | 2015-10-15 | [
[
"Casadio",
"Roberto",
""
],
[
"Ovalle",
"Jorge",
""
],
[
"da Rocha",
"Roldao",
""
]
] | The minimal geometric deformation approach was introduced in order to study the exterior space-time around spherically symmetric self-gravitating systems, like stars or similar astrophysical objects as well, in the Randall-Sundrum brane-world framework. A consistent extension of this approach is developed here, which contains modifications of both the time component and the radial component of a spherically symmetric metric. A modified Schwarzschild geometry is obtained as an example of its simplest application, and a new solution potentially useful to describe stars in the brane-world is also presented. |
2201.06097 | Jaume Haro | Jaume de Haro, Emilio Elizalde | Some topics in Cosmology -- Clearly explained by means of simple
examples -- | 43 pages, 3 figures. New references and material has been added.
Version accepted for publication in Universe | null | null | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | This is a very comprehensible review of some key issues in Modern Cosmology.
Simple mathematical examples and analogies are always used, whenever available.
The starting point is the well know Big Bang Cosmology (BBC). We deal with the
mathematical singularities appearing in this theory and discuss some ways to
remove them. Next, and before introducing the inflationary paradigm by means of
some clear examples, we review the horizon and flatness problems of the old BBC
model. We then consider the current cosmic acceleration and, as a procedure to
deal with both periods of acceleration in a unified way, we study
quintessential inflation. Finally, the reheating stage of the universe, via
gravitational particle production, which took place after inflation ended, is
discussed in simple mathematical terms, by involving the so-called
$\alpha$-attractors in the context of quintessential inflation.
| [
{
"created": "Sun, 16 Jan 2022 17:36:58 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jan 2022 16:29:30 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Mar 2022 10:22:11 GMT",
"version": "v3"
}
] | 2022-03-03 | [
[
"de Haro",
"Jaume",
""
],
[
"Elizalde",
"Emilio",
""
]
] | This is a very comprehensible review of some key issues in Modern Cosmology. Simple mathematical examples and analogies are always used, whenever available. The starting point is the well know Big Bang Cosmology (BBC). We deal with the mathematical singularities appearing in this theory and discuss some ways to remove them. Next, and before introducing the inflationary paradigm by means of some clear examples, we review the horizon and flatness problems of the old BBC model. We then consider the current cosmic acceleration and, as a procedure to deal with both periods of acceleration in a unified way, we study quintessential inflation. Finally, the reheating stage of the universe, via gravitational particle production, which took place after inflation ended, is discussed in simple mathematical terms, by involving the so-called $\alpha$-attractors in the context of quintessential inflation. |
1308.4770 | Sanjay Jhingan | Naresh Dadhich, Sushant G. Ghosh and Sanjay Jhingan | Bound orbits and gravitational theory | 7 pages, 1 pdf figure | Physical Review D 88, 124040 (2013) | 10.1103/PhysRevD.88.124040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It can be easily shown that bound orbits around a static source can exist
only in 4 dimension and in none else for any long range force. This is so not
only for Maxwell's electromagnetic and Newton's gravity but also for Einstein's
gravitation theory. In contrast to Maxwell's electrodynamics and Newton's
gravity, GR has a natural higher dimensional generalization in Lovelock gravity
which remarkably admits bound orbits around a static black hole in all even
d=2N+2 dimensions where $N$ is degree of Lovelock polynomial action. This is as
general a result as Bertrand's theorem of classical mechanics in which
existence of closed orbits uniquely singles out the inverse square law for a
long range central force.
| [
{
"created": "Thu, 22 Aug 2013 06:23:55 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Dadhich",
"Naresh",
""
],
[
"Ghosh",
"Sushant G.",
""
],
[
"Jhingan",
"Sanjay",
""
]
] | It can be easily shown that bound orbits around a static source can exist only in 4 dimension and in none else for any long range force. This is so not only for Maxwell's electromagnetic and Newton's gravity but also for Einstein's gravitation theory. In contrast to Maxwell's electrodynamics and Newton's gravity, GR has a natural higher dimensional generalization in Lovelock gravity which remarkably admits bound orbits around a static black hole in all even d=2N+2 dimensions where $N$ is degree of Lovelock polynomial action. This is as general a result as Bertrand's theorem of classical mechanics in which existence of closed orbits uniquely singles out the inverse square law for a long range central force. |
0706.2699 | Eyo Ita III | Eyo Eyo Ita III | Instanton representation of Plebanski gravity. Application to Bianchi
Type A metrics | 12 pages. Background material for revised journal article | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the instanton representation method we construct a general solution for
GR in the spatially homogeneous case restricted to diagonal variables. This
paper provides a testing ground and physical intuition for many of the salient
features of general relativity which it is suggested should be preserved in the
full theory.
| [
{
"created": "Tue, 19 Jun 2007 01:59:05 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jul 2007 04:53:57 GMT",
"version": "v2"
},
{
"created": "Mon, 26 May 2008 19:31:49 GMT",
"version": "v3"
},
{
"created": "Tue, 24 Jun 2008 19:26:47 GMT",
"version": "v4"
},
{
"created": "Wed, 21 Apr 2010 19:42:58 GMT",
"version": "v5"
},
{
"created": "Fri, 18 Mar 2011 07:38:08 GMT",
"version": "v6"
}
] | 2011-03-21 | [
[
"Ita",
"Eyo Eyo",
"III"
]
] | Using the instanton representation method we construct a general solution for GR in the spatially homogeneous case restricted to diagonal variables. This paper provides a testing ground and physical intuition for many of the salient features of general relativity which it is suggested should be preserved in the full theory. |
1911.09060 | Antonino Del Popolo | J. A. S. Lima (Departamento de Astronomia, Universidade de Sao Paulo),
A. Del Popolo (Catania University), A. R. Plastino (CeBio y Departamento de
Ciencias Basicas, Universidad Nacional del Noroeste de la Provincia de Buenos
Aires, UNNOBA) | Thermodynamic Equilibrium in General Relativity | 7 pages, 2 figures, PRD accepted | PRD 2009, volume 100, 104042;
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.104042 | 10.1103/PhysRevD.100.104042 | null | gr-qc astro-ph.GA cond-mat.stat-mech physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamic equilibrium condition for a static self-gravitating fluid
in the Einstein theory is defined by the Tolman-Ehrenfest temperature law,
$T{\sqrt {g_{00}(x^{i})}} = constant$, according to which the proper
temperature depends explicitly on the position within the medium through the
metric coefficient $g_{00}(x^{i})$. By assuming the validity of
Tolman-Ehrenfest "pocket temperature", Klein also proved a similar relation for
the chemical potential, namely, $\mu {\sqrt {g_{00}(x^{i})}} = constant$. In
this letter we prove that a more general relation uniting both quantities holds
regardless of the equation of state satisfied by the medium, and that the
original Tolman-Ehrenfest law form is valid only if the chemical potential
vanishes identically. In the general case of equilibrium, the temperature and
the chemical potential are intertwined in such a way that only a definite
(position dependent) relation uniting both quantities is obeyed. As an
illustration of these results, the temperature expressions for an isothermal
gas (finite spherical distribution) and a neutron star are also determined.
| [
{
"created": "Wed, 20 Nov 2019 17:44:36 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Nov 2019 17:53:43 GMT",
"version": "v2"
}
] | 2020-09-02 | [
[
"Lima",
"J. A. S.",
"",
"Departamento de Astronomia, Universidade de Sao Paulo"
],
[
"Del Popolo",
"A.",
"",
"Catania University"
],
[
"Plastino",
"A. R.",
"",
"CeBio y Departamento de\n Ciencias Basicas, Universidad Nacional del Noroeste de la Provincia de Buenos\n Aires, UNNOBA"
]
] | The thermodynamic equilibrium condition for a static self-gravitating fluid in the Einstein theory is defined by the Tolman-Ehrenfest temperature law, $T{\sqrt {g_{00}(x^{i})}} = constant$, according to which the proper temperature depends explicitly on the position within the medium through the metric coefficient $g_{00}(x^{i})$. By assuming the validity of Tolman-Ehrenfest "pocket temperature", Klein also proved a similar relation for the chemical potential, namely, $\mu {\sqrt {g_{00}(x^{i})}} = constant$. In this letter we prove that a more general relation uniting both quantities holds regardless of the equation of state satisfied by the medium, and that the original Tolman-Ehrenfest law form is valid only if the chemical potential vanishes identically. In the general case of equilibrium, the temperature and the chemical potential are intertwined in such a way that only a definite (position dependent) relation uniting both quantities is obeyed. As an illustration of these results, the temperature expressions for an isothermal gas (finite spherical distribution) and a neutron star are also determined. |
2305.04040 | Peng-Cheng Li | Wei Xiong and Peng-Cheng Li | Quasinormal modes of rotating accelerating black holes | 23 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies the quasinormal mode spectrum of the scalar perturbation
on the background of the rotating accelerating black holes. The quasinormal
frequency $\omega$ and the separation constant $\lambda$ are calculated using
two methods: the continued fractions method and the directly integration
method. The spectrum is found to include three families of modes: the photon
sphere modes, the acceleration modes, and the near extreme modes. We
investigate the effects of back hole parameters such as spin and acceleration.
Empirical formulas are presented for the numerical results, specifically for
the acceleration modes in the small black hole limit or the near extreme modes
in the extreme black hole limit. An interesting phenomenon known as eigenvalue
repulsion is observed when the acceleration modes intersect with the near
extreme modes at certain parameter values. The strong cosmic censorship
conjecture for spinning C-metric is respected.
| [
{
"created": "Sat, 6 May 2023 13:06:57 GMT",
"version": "v1"
}
] | 2023-05-09 | [
[
"Xiong",
"Wei",
""
],
[
"Li",
"Peng-Cheng",
""
]
] | This paper studies the quasinormal mode spectrum of the scalar perturbation on the background of the rotating accelerating black holes. The quasinormal frequency $\omega$ and the separation constant $\lambda$ are calculated using two methods: the continued fractions method and the directly integration method. The spectrum is found to include three families of modes: the photon sphere modes, the acceleration modes, and the near extreme modes. We investigate the effects of back hole parameters such as spin and acceleration. Empirical formulas are presented for the numerical results, specifically for the acceleration modes in the small black hole limit or the near extreme modes in the extreme black hole limit. An interesting phenomenon known as eigenvalue repulsion is observed when the acceleration modes intersect with the near extreme modes at certain parameter values. The strong cosmic censorship conjecture for spinning C-metric is respected. |
1306.3865 | David Keitel | Yan Wang, David Keitel, Stanislav Babak, Antoine Petiteau, Markus
Otto, Simon Barke, Fumiko Kawazoe, Alexander Khalaidovski, Vitali M\"uller,
Daniel Sch\"utze, Holger Wittel, Karsten Danzmann, Bernard F. Schutz | Octahedron configuration for a displacement noise-cancelling
gravitational wave detector in space | 17 pages, 5 figures, revtex4-1, matches version accepted by PRD | Phys. Rev. D 88, 104021 (2013) | 10.1103/PhysRevD.88.104021 | LIGO-P1300074; AEI-2013-261 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study for the first time a three-dimensional octahedron constellation for
a space-based gravitational wave detector, which we call the Octahedral
Gravitational Observatory (OGO). With six spacecraft the constellation is able
to remove laser frequency noise and acceleration disturbances from the
gravitational wave signal without needing LISA-like drag-free control, thereby
simplifying the payloads and placing less stringent demands on the thrusters.
We generalize LISA's time-delay interferometry to displacement-noise free
interferometry (DFI) by deriving a set of generators for those combinations of
the data streams that cancel laser and acceleration noise. However, the
three-dimensional configuration makes orbit selection complicated. So far, only
a halo orbit near the Lagrangian point L1 has been found to be stable enough,
and this allows only short arms up to 1400 km. We derive the sensitivity curve
of OGO with this arm length, resulting in a peak sensitivity of about
$2\times10^{-23}\,\mathrm{Hz}^{-1/2}$ near 100 Hz. We compare this version of
OGO to the present generation of ground-based detectors and to some future
detectors. We also investigate the scientific potentials of such a detector,
which include observing gravitational waves from compact binary coalescences,
the stochastic background and pulsars as well as the possibility to test
alternative theories of gravity. We find a mediocre performance level for this
short-arm-length detector, between those of initial and advanced ground-based
detectors. Thus, actually building a space-based detector of this specific
configuration does not seem very efficient. However, when alternative orbits
that allow for longer detector arms can be found, a detector with much improved
science output could be constructed using the octahedron configuration and DFI
solutions demonstrated in this paper. (abridged)
| [
{
"created": "Mon, 17 Jun 2013 14:04:29 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Nov 2013 17:24:44 GMT",
"version": "v2"
}
] | 2013-11-21 | [
[
"Wang",
"Yan",
""
],
[
"Keitel",
"David",
""
],
[
"Babak",
"Stanislav",
""
],
[
"Petiteau",
"Antoine",
""
],
[
"Otto",
"Markus",
""
],
[
"Barke",
"Simon",
""
],
[
"Kawazoe",
"Fumiko",
""
],
[
"Khalaidovski",
"Alexander",
""
],
[
"Müller",
"Vitali",
""
],
[
"Schütze",
"Daniel",
""
],
[
"Wittel",
"Holger",
""
],
[
"Danzmann",
"Karsten",
""
],
[
"Schutz",
"Bernard F.",
""
]
] | We study for the first time a three-dimensional octahedron constellation for a space-based gravitational wave detector, which we call the Octahedral Gravitational Observatory (OGO). With six spacecraft the constellation is able to remove laser frequency noise and acceleration disturbances from the gravitational wave signal without needing LISA-like drag-free control, thereby simplifying the payloads and placing less stringent demands on the thrusters. We generalize LISA's time-delay interferometry to displacement-noise free interferometry (DFI) by deriving a set of generators for those combinations of the data streams that cancel laser and acceleration noise. However, the three-dimensional configuration makes orbit selection complicated. So far, only a halo orbit near the Lagrangian point L1 has been found to be stable enough, and this allows only short arms up to 1400 km. We derive the sensitivity curve of OGO with this arm length, resulting in a peak sensitivity of about $2\times10^{-23}\,\mathrm{Hz}^{-1/2}$ near 100 Hz. We compare this version of OGO to the present generation of ground-based detectors and to some future detectors. We also investigate the scientific potentials of such a detector, which include observing gravitational waves from compact binary coalescences, the stochastic background and pulsars as well as the possibility to test alternative theories of gravity. We find a mediocre performance level for this short-arm-length detector, between those of initial and advanced ground-based detectors. Thus, actually building a space-based detector of this specific configuration does not seem very efficient. However, when alternative orbits that allow for longer detector arms can be found, a detector with much improved science output could be constructed using the octahedron configuration and DFI solutions demonstrated in this paper. (abridged) |
1501.04539 | Edward Malec | Patryk Mach and Edward Malec | General-relativistic rotation laws in rotating fluid bodies | 5 pages, to appear in the Physical Review D | Phys. Rev. D 91, 124053 (2015) | 10.1103/PhysRevD.91.124053 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We formulate new general-relativistic extensions of Newtonian rotation laws
for self-gravitating stationary fluids. They have been used to re-derive, in
the first post-Newtonian approximation, the well known geometric dragging of
frames. We derive two other general-relativistic weak-field effects within
rotating tori: the recently discovered dynamic anti-dragging and a new effect
that measures the deviation from the Keplerian motion and/or the contribution
of the fluids selfgravity. One can use the rotation laws to study the
uniqueness and the convergence of the post-Newtonian approximations, and the
existence of the post-Newtonian limits.
| [
{
"created": "Mon, 19 Jan 2015 16:28:14 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jun 2015 20:05:26 GMT",
"version": "v2"
}
] | 2015-06-24 | [
[
"Mach",
"Patryk",
""
],
[
"Malec",
"Edward",
""
]
] | We formulate new general-relativistic extensions of Newtonian rotation laws for self-gravitating stationary fluids. They have been used to re-derive, in the first post-Newtonian approximation, the well known geometric dragging of frames. We derive two other general-relativistic weak-field effects within rotating tori: the recently discovered dynamic anti-dragging and a new effect that measures the deviation from the Keplerian motion and/or the contribution of the fluids selfgravity. One can use the rotation laws to study the uniqueness and the convergence of the post-Newtonian approximations, and the existence of the post-Newtonian limits. |
1610.03294 | Jedrzej \'Swie\.zewski | Pawe{\l} Duch, Jerzy Lewandowski, Jedrzej \'Swie\.zewski | Observer's observables. Residual diffeomorphisms | 23 pages | Class. Quantum Grav. 34 (2017) 125009 | 10.1088/1361-6382/aa6f33 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the fate of diffeomorphisms when the radial gauge is imposed
in canonical general relativity. As shown elsewhere, the radial gauge is
closely related to the observer's observables. These observables are invariant
under a large subgroup of diffeomorphisms which results in their usefulness for
canonical general relativity. There are, however, some diffeomorphisms, called
residual diffeomorphisms, which might be "observed" by the observer as they do
not preserve her observables. The present paper is devoted to the analysis of
these diffeomorphisms in the case of the spatial and spacetime radial gauges.
Although the residual diffeomorphisms do not form a subgroup of all
diffeomorphisms, we show that their induced action in the phase space does form
a group. We find the generators of the induced transformations and compute the
structure functions of the algebras they form. The obtained algebras are
deformations of the algebra of the Euclidean group and the algebra of the
Poincar\'e group in the spatial and spacetime case, respectively. In both cases
the deformation depends only on the Riemann curvature tensor and in particular
vanishes when the space or spacetime is flat.
| [
{
"created": "Tue, 11 Oct 2016 12:09:02 GMT",
"version": "v1"
}
] | 2018-06-04 | [
[
"Duch",
"Paweł",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Świeżewski",
"Jedrzej",
""
]
] | We investigate the fate of diffeomorphisms when the radial gauge is imposed in canonical general relativity. As shown elsewhere, the radial gauge is closely related to the observer's observables. These observables are invariant under a large subgroup of diffeomorphisms which results in their usefulness for canonical general relativity. There are, however, some diffeomorphisms, called residual diffeomorphisms, which might be "observed" by the observer as they do not preserve her observables. The present paper is devoted to the analysis of these diffeomorphisms in the case of the spatial and spacetime radial gauges. Although the residual diffeomorphisms do not form a subgroup of all diffeomorphisms, we show that their induced action in the phase space does form a group. We find the generators of the induced transformations and compute the structure functions of the algebras they form. The obtained algebras are deformations of the algebra of the Euclidean group and the algebra of the Poincar\'e group in the spatial and spacetime case, respectively. In both cases the deformation depends only on the Riemann curvature tensor and in particular vanishes when the space or spacetime is flat. |
1602.04213 | Nurettin Pirinccioglu | Nurettin Pirinccioglu | Determinantal invariant gravity | 6 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein-Hilbert action with a determinantal invariant has been considered.
The obtained field equation contains the \texttt{inverse Ricci tensor},
$\Re_{\alpha\beta}$. The linearized solution of invariant has been examined,
and constant curvature space-time metric solution of the field equation gives
different curvature constant for each values of $\sigma$. $\sigma=0$ gives a
trivial solution for constant curvature, $R_{0}$.
| [
{
"created": "Fri, 12 Feb 2016 12:52:17 GMT",
"version": "v1"
}
] | 2016-02-16 | [
[
"Pirinccioglu",
"Nurettin",
""
]
] | Einstein-Hilbert action with a determinantal invariant has been considered. The obtained field equation contains the \texttt{inverse Ricci tensor}, $\Re_{\alpha\beta}$. The linearized solution of invariant has been examined, and constant curvature space-time metric solution of the field equation gives different curvature constant for each values of $\sigma$. $\sigma=0$ gives a trivial solution for constant curvature, $R_{0}$. |
gr-qc/0508078 | Pierre Noundjeu | P. Noundjeu | On the non-relativistic limit of the spherically symmetric
Einstein-Vlasov-Maxwell system | 16 pages | null | null | null | gr-qc | null | The Einstein-Vlasov-Maxwell (EVM) system can be viewed as a relativistic
generalization of the Vlasov-Poisson (VP) system. As it is proved below, one of
nice property obeys by the first system is that the strong energy condition
holds and this allows to conclude that the above system is physically viable.
We show in this paper that in the context of spherical symmetry, solutions of
the perturbed (EVM) system by $\gamma := 1/c^{2}$, $c$ being the speed of
light, exist and converge uniformly in $L^{\infty}$-norm, as $c$ goes to
infinity on compact time intervals to solutions of the non-relativistic (VP)
system.
| [
{
"created": "Fri, 19 Aug 2005 10:09:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Noundjeu",
"P.",
""
]
] | The Einstein-Vlasov-Maxwell (EVM) system can be viewed as a relativistic generalization of the Vlasov-Poisson (VP) system. As it is proved below, one of nice property obeys by the first system is that the strong energy condition holds and this allows to conclude that the above system is physically viable. We show in this paper that in the context of spherical symmetry, solutions of the perturbed (EVM) system by $\gamma := 1/c^{2}$, $c$ being the speed of light, exist and converge uniformly in $L^{\infty}$-norm, as $c$ goes to infinity on compact time intervals to solutions of the non-relativistic (VP) system. |
2111.14612 | Alexander P. Sobolev | Alexander P. Sobolev | Foundations of a Theory of Gravity with a Constraint and its Canonical
Quantization | 34 pages, 11 figures, 2 tables | Foundations of Physics 52, 3 (2022) | 10.1007/s10701-021-00521-1 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The gravitational equations were derived in general relativity (GR) using the
assumption of their covariance relative to arbitrary transformations of
coordinates. It has been repeatedly expressed an opinion over the past century
that such equality of all coordinate systems may not correspond to reality.
Nevertheless, no actual verification of the necessity of this assumption has
been made to date. The paper proposes a theory of gravity with a constraint,
the degenerate variants of which are general relativity (GR) and the unimodular
theory of gravity. This constraint is interpreted from a physical point of view
as a sufficient condition for the adiabaticity of the process of the evolution
of the space-time metric. The original equations of the theory of gravity with
the constraint are formulated. On this basis, a unified model of the evolution
of the modern, early, and very early Universe is constructed that is consistent
with the observational astronomical data but does not require the hypotheses of
the existence of dark energy, dark matter or inflatons. It is claimed that:
physical time is anisotropic, the gravitational field is the main source of
energy of the Universe, the maximum global energy density in the Universe was
64 orders of magnitude smaller the Planckian one, and the entropy density is 18
orders of magnitude higher the value predicted by GR. The value of the relative
density of neutrinos at the present time and the maximum temperature of matter
in the early Universe are calculated. The wave equation of the gravitational
field is formulated, its solution is found, and the nonstationary wave function
of the very early Universe is constructed. It is shown that the birth of the
Universe was random.
| [
{
"created": "Thu, 25 Nov 2021 14:44:25 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Mar 2022 12:40:06 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Mar 2023 11:12:09 GMT",
"version": "v3"
},
{
"created": "Mon, 25 Sep 2023 16:20:07 GMT",
"version": "v4"
},
{
"created": "Fri, 26 Apr 2024 07:21:55 GMT",
"version": "v5"
},
{
"created": "Tue, 30 Jul 2024 17:12:24 GMT",
"version": "v6"
},
{
"created": "Wed, 31 Jul 2024 14:58:12 GMT",
"version": "v7"
}
] | 2024-08-07 | [
[
"Sobolev",
"Alexander P.",
""
]
] | The gravitational equations were derived in general relativity (GR) using the assumption of their covariance relative to arbitrary transformations of coordinates. It has been repeatedly expressed an opinion over the past century that such equality of all coordinate systems may not correspond to reality. Nevertheless, no actual verification of the necessity of this assumption has been made to date. The paper proposes a theory of gravity with a constraint, the degenerate variants of which are general relativity (GR) and the unimodular theory of gravity. This constraint is interpreted from a physical point of view as a sufficient condition for the adiabaticity of the process of the evolution of the space-time metric. The original equations of the theory of gravity with the constraint are formulated. On this basis, a unified model of the evolution of the modern, early, and very early Universe is constructed that is consistent with the observational astronomical data but does not require the hypotheses of the existence of dark energy, dark matter or inflatons. It is claimed that: physical time is anisotropic, the gravitational field is the main source of energy of the Universe, the maximum global energy density in the Universe was 64 orders of magnitude smaller the Planckian one, and the entropy density is 18 orders of magnitude higher the value predicted by GR. The value of the relative density of neutrinos at the present time and the maximum temperature of matter in the early Universe are calculated. The wave equation of the gravitational field is formulated, its solution is found, and the nonstationary wave function of the very early Universe is constructed. It is shown that the birth of the Universe was random. |
2304.14222 | Claudio Aravena Cap | Claudio Aravena-Plaza, V\'ictor Mu\~noz and Felipe A. Asenjo | London-like tensor modes of gravitational waves in cosmic string
cosmology | null | null | 10.1134/S0202289323040035 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | From a classical analysis, we show that gravitational waves in a cosmological
medium with equation of state $\omega=-1/3$ can follow a London-like equation,
implying that some gravitational wave solutions present a decay for certain
wavelengths. This scenario, corresponding to a cosmic string cosmology, induces
an attenuation temporal scale on the gravitational wave propagation. We discuss
on how these solutions impose a limit on the wavelength of the waves that can
propagate, which depends on the type of spatial curvature and the energy
density content of this type of cosmology.
| [
{
"created": "Thu, 27 Apr 2023 14:33:07 GMT",
"version": "v1"
}
] | 2023-11-30 | [
[
"Aravena-Plaza",
"Claudio",
""
],
[
"Muñoz",
"Víctor",
""
],
[
"Asenjo",
"Felipe A.",
""
]
] | From a classical analysis, we show that gravitational waves in a cosmological medium with equation of state $\omega=-1/3$ can follow a London-like equation, implying that some gravitational wave solutions present a decay for certain wavelengths. This scenario, corresponding to a cosmic string cosmology, induces an attenuation temporal scale on the gravitational wave propagation. We discuss on how these solutions impose a limit on the wavelength of the waves that can propagate, which depends on the type of spatial curvature and the energy density content of this type of cosmology. |
0908.4067 | Thomas L. Wilson | Thomas L. Wilson, Hans-Joachim Blome | The Pioneer Anomaly and a Rotating G\"odel Universe | 13 pages, 2 figures | Adv.Space Res.44:1345-1353,2009 | 10.1016/j.asr.2009.07.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based upon a simple cosmological model with no expansion, we find that the
rotational terms appearing in the G/"odel universe are too small to explain the
Pioneer anomaly. Although it contributes, universal rotation is not the cause
of the Pioneer effect.
| [
{
"created": "Thu, 27 Aug 2009 19:08:39 GMT",
"version": "v1"
}
] | 2009-11-18 | [
[
"Wilson",
"Thomas L.",
""
],
[
"Blome",
"Hans-Joachim",
""
]
] | Based upon a simple cosmological model with no expansion, we find that the rotational terms appearing in the G/"odel universe are too small to explain the Pioneer anomaly. Although it contributes, universal rotation is not the cause of the Pioneer effect. |
1607.06662 | Andreas G. A. Pithis | Andreas G. A. Pithis, Mairi Sakellariadou and Petar Tomov | Impact of nonlinear effective interactions on GFT quantum gravity
condensates | 22 pages, 18 figures; closest to published version | Phys. Rev. D 94, 064056 (2016) | 10.1103/PhysRevD.94.064056 | KCL-PH-TH/2016-43 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the numerical analysis of effectively interacting Group Field
Theory (GFT) models in the context of the GFT quantum gravity condensate
analogue of the Gross-Pitaevskii equation for real Bose-Einstein condensates
including combinatorially local interaction terms. Thus we go beyond the
usually considered construction for free models.
More precisely, considering such interactions in a weak regime, we find
solutions for which the expectation value of the number operator N is finite,
as in the free case. When tuning the interaction to the strongly nonlinear
regime, however, we obtain solutions for which N grows and eventually blows up,
which is reminiscent of what one observes for real Bose-Einstein condensates,
where a strong interaction regime can only be realized at high density. This
behaviour suggests the breakdown of the Bogoliubov ansatz for quantum gravity
condensates and the need for non-Fock representations to describe the system
when the condensate constituents are strongly correlated.
Furthermore, we study the expectation values of certain geometric operators
imported from Loop Quantum Gravity in the free and interacting cases. In
particular, computing solutions around the nontrivial minima of the interaction
potentials, one finds, already in the weakly interacting case, a nonvanishing
condensate population for which the spectra are dominated by the lowest
nontrivial configuration of the quantum geometry. This result indicates that
the condensate may indeed consist of many smallest building blocks giving rise
to an effectively continuous geometry, thus suggesting the interpretation of
the condensate phase to correspond to a geometric phase.
| [
{
"created": "Thu, 21 Jul 2016 00:40:34 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Sep 2016 06:32:09 GMT",
"version": "v2"
}
] | 2016-09-28 | [
[
"Pithis",
"Andreas G. A.",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Tomov",
"Petar",
""
]
] | We present the numerical analysis of effectively interacting Group Field Theory (GFT) models in the context of the GFT quantum gravity condensate analogue of the Gross-Pitaevskii equation for real Bose-Einstein condensates including combinatorially local interaction terms. Thus we go beyond the usually considered construction for free models. More precisely, considering such interactions in a weak regime, we find solutions for which the expectation value of the number operator N is finite, as in the free case. When tuning the interaction to the strongly nonlinear regime, however, we obtain solutions for which N grows and eventually blows up, which is reminiscent of what one observes for real Bose-Einstein condensates, where a strong interaction regime can only be realized at high density. This behaviour suggests the breakdown of the Bogoliubov ansatz for quantum gravity condensates and the need for non-Fock representations to describe the system when the condensate constituents are strongly correlated. Furthermore, we study the expectation values of certain geometric operators imported from Loop Quantum Gravity in the free and interacting cases. In particular, computing solutions around the nontrivial minima of the interaction potentials, one finds, already in the weakly interacting case, a nonvanishing condensate population for which the spectra are dominated by the lowest nontrivial configuration of the quantum geometry. This result indicates that the condensate may indeed consist of many smallest building blocks giving rise to an effectively continuous geometry, thus suggesting the interpretation of the condensate phase to correspond to a geometric phase. |
gr-qc/0612145 | Karim Noui | Karim Noui | Three dimensional Loop Quantum Gravity: towards a self-gravitating
Quantum Field Theory | 36 pages, published in Class. Quant. Grav | Class.Quant.Grav.24:329-360,2007 | 10.1088/0264-9381/24/2/005 | null | gr-qc | null | In a companion paper, we have emphasized the role of the Drinfeld double
DSU(2) in the context of three dimensional Riemannian Loop Quantum Gravity
coupled to massive spinless point particles. We make use of this result to
propose a model for a self-gravitating quantum field theory (massive spinless
non-causal scalar field) in three dimensional Riemannian space. We start by
constructing the Fock space of the free self-gravitating field: the vacuum is
the unique DSU(2) invariant state, one-particle states correspond to DSU(2)
unitary irreducible simple representations and any multi-particles states is
obtained as the symmetrized tensor product between simple representations. The
associated quantum field is defined by the usual requirement of covariance
under DSU(2). Then, we introduce a DSU(2)-invariant self-interacting potential
(the obtained model is a Group Field Theory) and compute explicitely the lowest
order terms (in the self-interaction coupling constant $\lambda$) of the
propagator and of the three-points function. Finally, we compute the lowest
order quantum gravity corrections (in the Newton constant G) to the propagator
and to the three-points function.
| [
{
"created": "Fri, 22 Dec 2006 13:40:33 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Noui",
"Karim",
""
]
] | In a companion paper, we have emphasized the role of the Drinfeld double DSU(2) in the context of three dimensional Riemannian Loop Quantum Gravity coupled to massive spinless point particles. We make use of this result to propose a model for a self-gravitating quantum field theory (massive spinless non-causal scalar field) in three dimensional Riemannian space. We start by constructing the Fock space of the free self-gravitating field: the vacuum is the unique DSU(2) invariant state, one-particle states correspond to DSU(2) unitary irreducible simple representations and any multi-particles states is obtained as the symmetrized tensor product between simple representations. The associated quantum field is defined by the usual requirement of covariance under DSU(2). Then, we introduce a DSU(2)-invariant self-interacting potential (the obtained model is a Group Field Theory) and compute explicitely the lowest order terms (in the self-interaction coupling constant $\lambda$) of the propagator and of the three-points function. Finally, we compute the lowest order quantum gravity corrections (in the Newton constant G) to the propagator and to the three-points function. |
1601.06134 | Giuseppe Alberti | Giuseppe Alberti, Marco Merafina | A General Criterion for the Dynamical Stability of Anisotropic Newtonian
Systems | 6 pages, 3 figures. Presence of a conceptual mistake [Eq.(20)] for
what concerns the deduction of the stability criterion. Consequently Eqs.(27)
and (28) are wrong | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of the dynamical stability of anistropic systems is studied, by
proposing a criterion in terms of the adiabatic local index $\gamma$. The
result has general validity and can be applied to several physical situations.
Configurations that cannot exist in the isotropic regime can exist in the
anisotropic one. Some applications of the criterion are also included.
| [
{
"created": "Fri, 22 Jan 2016 20:06:10 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2019 20:29:50 GMT",
"version": "v2"
}
] | 2019-02-14 | [
[
"Alberti",
"Giuseppe",
""
],
[
"Merafina",
"Marco",
""
]
] | The problem of the dynamical stability of anistropic systems is studied, by proposing a criterion in terms of the adiabatic local index $\gamma$. The result has general validity and can be applied to several physical situations. Configurations that cannot exist in the isotropic regime can exist in the anisotropic one. Some applications of the criterion are also included. |
gr-qc/0212061 | Ujjal Debnath | Ujjal Debnath and Subenoy Chakraborty | Naked singularity formation for higher dimensional inhomogeneous dust
collapse | 7 Latex pages, No figure, Revtex style | null | null | null | gr-qc | null | We investigate the occurrence and nature of a naked singularity in the
gravitational collapse of an inhomogeneous dust cloud described by higher
dimensional Tolman-Bondi space-time. The naked singularities are found to be
gravitationally strong.
| [
{
"created": "Fri, 13 Dec 2002 16:53:47 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Feb 2003 11:07:48 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Debnath",
"Ujjal",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | We investigate the occurrence and nature of a naked singularity in the gravitational collapse of an inhomogeneous dust cloud described by higher dimensional Tolman-Bondi space-time. The naked singularities are found to be gravitationally strong. |
1405.3878 | Mauricio Cataldo MC | Mauricio Cataldo and Alberto A. Garc\'ia | Radiation in (2+1)-dimensions | 7 pages. Accepted for publication in Phys. Lett. B | Phys. Lett. B, 734, (2014) 58-63 | 10.1016/j.physletb.2014.05.019 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss the radiation equation of state $p=\rho/2$ in
(2+1)-dimensions. In (3+1)-dimensions the equation of state $p=\rho/3$ may be
used to describe either actual electromagnetic radiation (photons) as well as a
gas of massless particles in a thermodynamic equilibrium (for example
neutrinos). In this work it is shown that in the framework of (2+1)-dimensional
Maxwell electrodynamics the radiation law $p=\rho/2$ takes place only for plane
waves, i.e. for $E = B$. Instead of the linear Maxwell electrodynamics, to
derive the (2+1)-radiation law for more general cases with $E \neq B$, one has
to use a conformally invariant electrodynamics, which is a 2+1-nonlinear
electrodynamics with a trace free energy-momentum tensor, and to perform a
volumetric spatial average of the corresponding Maxwell stress-energy tensor
with its electric and magnetic components at a given instant of time $t$.
| [
{
"created": "Thu, 15 May 2014 15:15:02 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Cataldo",
"Mauricio",
""
],
[
"García",
"Alberto A.",
""
]
] | In this paper we discuss the radiation equation of state $p=\rho/2$ in (2+1)-dimensions. In (3+1)-dimensions the equation of state $p=\rho/3$ may be used to describe either actual electromagnetic radiation (photons) as well as a gas of massless particles in a thermodynamic equilibrium (for example neutrinos). In this work it is shown that in the framework of (2+1)-dimensional Maxwell electrodynamics the radiation law $p=\rho/2$ takes place only for plane waves, i.e. for $E = B$. Instead of the linear Maxwell electrodynamics, to derive the (2+1)-radiation law for more general cases with $E \neq B$, one has to use a conformally invariant electrodynamics, which is a 2+1-nonlinear electrodynamics with a trace free energy-momentum tensor, and to perform a volumetric spatial average of the corresponding Maxwell stress-energy tensor with its electric and magnetic components at a given instant of time $t$. |
0710.2515 | Georgii Alekseev | G.A. Alekseev and V.A. Belinski | Superposition of fields of two Reissner - Nordstrom sources | 24 pages, submitted to the Proceedings of the Eleventh Marcel
Grossmann Meeting (Berlin, July 23 - 29, 2006) | null | 10.1142/9789812834300_0022 | null | gr-qc | null | In this paper we present a 5-parametric family of static asymptotically flat
solutions for the superposed gravitational and electromagnetic fields of two
Reissner-Nordstr\"om sources with arbitrary parameters -- masses, charges and
separating distance. A procedure for solving of the linear singular integral
equation form of the electrovacuum Einstein - Maxwell equations for stationary
axisymmetric fields is described in detail. The 4-parametric family of
equilibrium configurations of two Reissner-Nordstr\"om sources (one of which
should be a black hole and another one -- a naked singularity) presented in our
recent paper \cite{Alekseev-Belinski:2007} arises after a restriction of the
parameters of the 5-parametric solution presented here by the equilibrium
condition which provides the absence in the solution of conical points on the
symmetry axis between the sources.
| [
{
"created": "Fri, 12 Oct 2007 17:24:25 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Alekseev",
"G. A.",
""
],
[
"Belinski",
"V. A.",
""
]
] | In this paper we present a 5-parametric family of static asymptotically flat solutions for the superposed gravitational and electromagnetic fields of two Reissner-Nordstr\"om sources with arbitrary parameters -- masses, charges and separating distance. A procedure for solving of the linear singular integral equation form of the electrovacuum Einstein - Maxwell equations for stationary axisymmetric fields is described in detail. The 4-parametric family of equilibrium configurations of two Reissner-Nordstr\"om sources (one of which should be a black hole and another one -- a naked singularity) presented in our recent paper \cite{Alekseev-Belinski:2007} arises after a restriction of the parameters of the 5-parametric solution presented here by the equilibrium condition which provides the absence in the solution of conical points on the symmetry axis between the sources. |
1104.1082 | Wessel Valkenburg | Wessel Valkenburg (RWTH Aachen) | Complete solutions to the metric of spherically collapsing dust in an
expanding spacetime with a cosmological constant | 23 pages, one figure. Numerical module for evaluation of the
solutions released at
http://web.physik.rwth-aachen.de/download/valkenburg/ColLambda/ Matches
published version, published under Open Access. Note change of title | Gen.Rel.Grav. 44 (2012) 2449-2476 | 10.1007/s10714-012-1405-9 | TTK-11-10 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present semi-analytical solutions to the background equations describing
the Lema\^itre-Tolman-Bondi (LTB) metric as well as the homogeneous Friedmann
equations, in the presence of dust, curvature and a cosmological constant
Lambda. For none of the presented solutions any numerical integration has to be
performed. All presented solutions are given for expanding and collapsing
phases, preserving continuity in time and radius. Hence, these solutions
describe the complete space time of a collapsing spherical object in an
expanding universe. In the appendix we present for completeness a solution of
the Friedmann equations in the additional presence of radiation, only valid for
the Robertson-Walker metric.
| [
{
"created": "Wed, 6 Apr 2011 13:02:36 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jun 2011 20:00:49 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Jul 2012 13:39:58 GMT",
"version": "v3"
}
] | 2015-03-19 | [
[
"Valkenburg",
"Wessel",
"",
"RWTH Aachen"
]
] | We present semi-analytical solutions to the background equations describing the Lema\^itre-Tolman-Bondi (LTB) metric as well as the homogeneous Friedmann equations, in the presence of dust, curvature and a cosmological constant Lambda. For none of the presented solutions any numerical integration has to be performed. All presented solutions are given for expanding and collapsing phases, preserving continuity in time and radius. Hence, these solutions describe the complete space time of a collapsing spherical object in an expanding universe. In the appendix we present for completeness a solution of the Friedmann equations in the additional presence of radiation, only valid for the Robertson-Walker metric. |
gr-qc/9601033 | Alejandro Jakubi | Luis P. Chimento and Alejandro S. Jakubi | Relaxation dominated cosmological expansion | 7 pages, LaTeX. To be published in Physics Letters A | Physics Letters A 212 (1996) 320 | 10.1016/0375-9601(96)00024-2 | null | gr-qc | null | The behavior near the singularity of an isotropic, homogeneous cosmological
model with a viscous fluid source is investigated. This turns out to be a
relaxation dominated regime. Full extended irreversible thermodynamics is used,
and comparison with results of the truncated theory is made. New singular
behaviors are found and it is shown that a relaxation dominated inflationary
epoch may exist for fluids with small heat capacity.
| [
{
"created": "Mon, 22 Jan 1996 18:50:41 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Chimento",
"Luis P.",
""
],
[
"Jakubi",
"Alejandro S.",
""
]
] | The behavior near the singularity of an isotropic, homogeneous cosmological model with a viscous fluid source is investigated. This turns out to be a relaxation dominated regime. Full extended irreversible thermodynamics is used, and comparison with results of the truncated theory is made. New singular behaviors are found and it is shown that a relaxation dominated inflationary epoch may exist for fluids with small heat capacity. |
0804.0948 | Muhammad Sharif | M. Sharif and M. Jamil Amir | Teleparallel Version of the Levi-Civita Vacuum Solutions and their
Energy Contents | 15 pages, accepted for publication in Canadian J. Physics | Can.J.Phys.86:1091-1096,2008 | 10.1139/P08-033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we find the teleparallel version of the Levi-Civita metric and
obtain tetrad and the torsion fields. The tensor, vector and the axial-vector
parts of the torsion tensor are evaluated. It is found that the vector part
lies along the radial direction only while the axial-vector vanishes everywhere
because the metric is diagonal. Further, we use the teleparallel version of
M$\ddot{o}$ller, Einstein, Landau-Lifshitz and Bergmann-Thomson prescriptions
to find the energy-momentum distribution of this metric and compare the results
with those already found in General Relativity. It is worth mentioning here
that momentum is constant in both the theories for all the prescriptions. The
energy in teleparallel theory is equal to the corresponding energy in GR only
in M$\ddot{o}$ller prescription for the remaining prescriptions, the energy do
not agree in both theories. We also conclude that M$\ddot{o}$ller's
energy-momentum distribution is independent of the coupling constant $\lambda$
in the teleparallel theory.
| [
{
"created": "Mon, 7 Apr 2008 02:27:58 GMT",
"version": "v1"
}
] | 2009-01-14 | [
[
"Sharif",
"M.",
""
],
[
"Amir",
"M. Jamil",
""
]
] | In this paper, we find the teleparallel version of the Levi-Civita metric and obtain tetrad and the torsion fields. The tensor, vector and the axial-vector parts of the torsion tensor are evaluated. It is found that the vector part lies along the radial direction only while the axial-vector vanishes everywhere because the metric is diagonal. Further, we use the teleparallel version of M$\ddot{o}$ller, Einstein, Landau-Lifshitz and Bergmann-Thomson prescriptions to find the energy-momentum distribution of this metric and compare the results with those already found in General Relativity. It is worth mentioning here that momentum is constant in both the theories for all the prescriptions. The energy in teleparallel theory is equal to the corresponding energy in GR only in M$\ddot{o}$ller prescription for the remaining prescriptions, the energy do not agree in both theories. We also conclude that M$\ddot{o}$ller's energy-momentum distribution is independent of the coupling constant $\lambda$ in the teleparallel theory. |
1210.1109 | Josep M. Pons | Naresh Dadhich and Josep M. Pons | Probing pure Lovelock gravity by Nariai and Bertotti-Robinson solutions | Title changed, contents reordered, changes in the introduction to
clarify some points | J. Math. Phys. 54, 102501 (2013) | 10.1063/1.4825115 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The product spacetimes of constant curvature describe in Einstein gravity,
which is linear in Riemann curvature, Nariai metric which is a solution of
$\Lambda$-vacuum when curvatures are equal, $k_1=k_2$, while it is
Bertotti-Robinson metric describing uniform electric field when curvatures are
equal and opposite, $k_1=-k_2$. We probe pure Lovelock gravity by these simple
product spacetimes and prove that the same characterization of these solutions
is indeed true in general for pure Lovelock gravitational equation of order $N$
in $d=2N+2$ dimension. We also consider these solutions for the conventional
setting of Einstein-Gauss-Bonnet gravity.
| [
{
"created": "Wed, 3 Oct 2012 13:58:33 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Nov 2013 10:06:15 GMT",
"version": "v2"
}
] | 2013-11-18 | [
[
"Dadhich",
"Naresh",
""
],
[
"Pons",
"Josep M.",
""
]
] | The product spacetimes of constant curvature describe in Einstein gravity, which is linear in Riemann curvature, Nariai metric which is a solution of $\Lambda$-vacuum when curvatures are equal, $k_1=k_2$, while it is Bertotti-Robinson metric describing uniform electric field when curvatures are equal and opposite, $k_1=-k_2$. We probe pure Lovelock gravity by these simple product spacetimes and prove that the same characterization of these solutions is indeed true in general for pure Lovelock gravitational equation of order $N$ in $d=2N+2$ dimension. We also consider these solutions for the conventional setting of Einstein-Gauss-Bonnet gravity. |
2203.07926 | Eduardo Bittencourt | Eduardo Bittencourt, Leandro G. Gomes, Grasiele B. Santos | On the intrinsically flat cosmological models in a lattice | 16 pages, 3 figures | null | 10.1088/1361-6382/ac96c3 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | In this manuscript we investigate the intrinsically flat (space-flat)
spacetimes as viable cosmological models. We show that they have a natural
geometric structure which is suitable to describe inhomogeneous matter
distributions forming a periodic pattern throughout the space. We prove
theorems for their local representation and for existence and uniqueness of the
Einstein's equations with these periodic boundary conditions. We also find an
interesting class of exact solutions, which illustrates the applicability of
such spacetimes in cosmology, with an early time behavior close to homogeneity
and isotropy and a late time aspect with peaks and voids in the matter
distribution.
| [
{
"created": "Tue, 15 Mar 2022 14:07:04 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Bittencourt",
"Eduardo",
""
],
[
"Gomes",
"Leandro G.",
""
],
[
"Santos",
"Grasiele B.",
""
]
] | In this manuscript we investigate the intrinsically flat (space-flat) spacetimes as viable cosmological models. We show that they have a natural geometric structure which is suitable to describe inhomogeneous matter distributions forming a periodic pattern throughout the space. We prove theorems for their local representation and for existence and uniqueness of the Einstein's equations with these periodic boundary conditions. We also find an interesting class of exact solutions, which illustrates the applicability of such spacetimes in cosmology, with an early time behavior close to homogeneity and isotropy and a late time aspect with peaks and voids in the matter distribution. |
2209.12117 | Cheng-Yong Zhang | Chao Niu, Wei Xiong, Peng Liu, Cheng-Yong Zhang and Bin Wang | Dynamical descalarization in Einstein-Maxwell-scalar theory | 18 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For an asymptotically flat hairy black hole in the Einstein-Maxwell-scalar
(EMS) theory, we study the possibility of shedding off its scalar hair via
nonlinear scalar perturbation fully interacting with the background spacetime.
We examine the effect of the perturbation strength on the descalarization. The
results show that the effective charge to mass ratio of the black hole plays
the key role in the dynamical descalarization. The descalarization at the
threshold is continuous. This indicates a second order phase transition.
| [
{
"created": "Sun, 25 Sep 2022 01:23:12 GMT",
"version": "v1"
}
] | 2022-09-27 | [
[
"Niu",
"Chao",
""
],
[
"Xiong",
"Wei",
""
],
[
"Liu",
"Peng",
""
],
[
"Zhang",
"Cheng-Yong",
""
],
[
"Wang",
"Bin",
""
]
] | For an asymptotically flat hairy black hole in the Einstein-Maxwell-scalar (EMS) theory, we study the possibility of shedding off its scalar hair via nonlinear scalar perturbation fully interacting with the background spacetime. We examine the effect of the perturbation strength on the descalarization. The results show that the effective charge to mass ratio of the black hole plays the key role in the dynamical descalarization. The descalarization at the threshold is continuous. This indicates a second order phase transition. |
0801.1317 | Viqar Husain | Viqar Husain | Gravitational collapse in quantum gravity | 5 pages. Invited talk published in "Mathematical Physics: Proceedings
of the 12th. Regional Conference," Eds. J. Aslam et. al. (World Scientific,
Singapore, 2007) | null | null | null | gr-qc | null | We give a review of recent work aimed at understanding the dynamics of
gravitational collapse in quantum gravity. Its goal is to provide a
non-perturbative computational framework for understanding the emergence of the
semi-classical approximation and Hawking radiation. The model studied is the
gravity-scalar field theory in spherical symmetry. A quantization of this
theory is given in which operators corresponding to null expansions and
curvature are well defined. Together with the Hamiltonian, these operators
allow one to follow the evolution of an initial matter-geometry state to a
trapped configuration and beyond, in a singularity free and unitary setting.
| [
{
"created": "Tue, 8 Jan 2008 20:34:50 GMT",
"version": "v1"
}
] | 2008-01-09 | [
[
"Husain",
"Viqar",
""
]
] | We give a review of recent work aimed at understanding the dynamics of gravitational collapse in quantum gravity. Its goal is to provide a non-perturbative computational framework for understanding the emergence of the semi-classical approximation and Hawking radiation. The model studied is the gravity-scalar field theory in spherical symmetry. A quantization of this theory is given in which operators corresponding to null expansions and curvature are well defined. Together with the Hamiltonian, these operators allow one to follow the evolution of an initial matter-geometry state to a trapped configuration and beyond, in a singularity free and unitary setting. |
0710.4058 | Edward Glass | J.P. Krisch and E.N. Glass | Collapsing Layers on Schwarzschild-Lemaitre Geodesics | To appear in Phys. Rev. D 15 | Phys.Rev.D76:104006,2007 | 10.1103/PhysRevD.76.104006 | null | gr-qc | null | We discuss Israel layers collapsing inward from rest at infinity along
Schwarzschild-Lemaitre geodesics. The dynamics of the collapsing layer and its
equation of state are developed. There is a general equation of state which is
approximately polytropic in the limit of very low pressure. The equation of
state establishes a new limit on the stress-density ratio.
| [
{
"created": "Mon, 22 Oct 2007 18:19:45 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Krisch",
"J. P.",
""
],
[
"Glass",
"E. N.",
""
]
] | We discuss Israel layers collapsing inward from rest at infinity along Schwarzschild-Lemaitre geodesics. The dynamics of the collapsing layer and its equation of state are developed. There is a general equation of state which is approximately polytropic in the limit of very low pressure. The equation of state establishes a new limit on the stress-density ratio. |
1405.3715 | Ian Vega | Thomas P. Sotiriou, Ian Vega, Daniele Vernieri | Rotating black holes in three-dimensional Ho\v{r}ava gravity | 16 pages, 9 figures, final published version | Phys. Rev. D 90, 044046 (2014) | 10.1103/PhysRevD.90.044046 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study black holes in the infrared sector of three-dimensional Ho\v{r}ava
gravity. It is shown that black hole solutions with anti-de Sitter asymptotics
are admissible only in the sector of the theory in which the scalar degree of
freedom propagates infinitely fast. We derive the most general class of
stationary, circularly symmetric, asymptotically anti-de Sitter black hole
solutions. We also show that the theory admits black hole solutions with de
Sitter and flat asymptotics, unlike three-dimensional general relativity. For
all these cases, universal horizons may or may not exist depending on the
choice of parameters. Solutions with de Sitter asymptotics can have universal
horizons that lie beyond the de Sitter horizon.
| [
{
"created": "Wed, 14 May 2014 23:23:06 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Aug 2014 20:31:58 GMT",
"version": "v2"
}
] | 2014-08-26 | [
[
"Sotiriou",
"Thomas P.",
""
],
[
"Vega",
"Ian",
""
],
[
"Vernieri",
"Daniele",
""
]
] | We study black holes in the infrared sector of three-dimensional Ho\v{r}ava gravity. It is shown that black hole solutions with anti-de Sitter asymptotics are admissible only in the sector of the theory in which the scalar degree of freedom propagates infinitely fast. We derive the most general class of stationary, circularly symmetric, asymptotically anti-de Sitter black hole solutions. We also show that the theory admits black hole solutions with de Sitter and flat asymptotics, unlike three-dimensional general relativity. For all these cases, universal horizons may or may not exist depending on the choice of parameters. Solutions with de Sitter asymptotics can have universal horizons that lie beyond the de Sitter horizon. |
2404.18147 | Sobhan Kazempour | Sobhan Kazempour and Amin Rezaei Akbarieh | The Cosmological Impact of Brane-Chern-Simons Massive Gravity | null | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | In this paper, we present a novel extension of massive gravity theory; the
Brane-Chern-Simons massive gravity theory. We explore the cosmological
implications of this theory by deriving the background equations and
demonstrating the existence of self-accelerating solutions. Interestingly, our
theory suggests the existence of self-accelerating mechanisms that originate
from an effective cosmological constant, leading to intriguing possibilities
for understanding the nature of cosmic acceleration. Furthermore, we perform a
tensor perturbation analysis to investigate the propagation of gravitational
waves in this framework. We derive the dispersion relation for gravitational
waves and study their behavior in the Friedmann-Lema\^itre-Roberson-Waker
cosmology within the context of Brane-Chen-Simons massive gravity. Utilizing
the latest Union2 type Ia supernova dataset comprising $557$ SNIa events, we
provide observational support for our theoretical framework, indicating that
the Brane-Chern-Simons massive gravity theory is consistent with cosmological
observations.
| [
{
"created": "Sun, 28 Apr 2024 11:42:01 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Kazempour",
"Sobhan",
""
],
[
"Akbarieh",
"Amin Rezaei",
""
]
] | In this paper, we present a novel extension of massive gravity theory; the Brane-Chern-Simons massive gravity theory. We explore the cosmological implications of this theory by deriving the background equations and demonstrating the existence of self-accelerating solutions. Interestingly, our theory suggests the existence of self-accelerating mechanisms that originate from an effective cosmological constant, leading to intriguing possibilities for understanding the nature of cosmic acceleration. Furthermore, we perform a tensor perturbation analysis to investigate the propagation of gravitational waves in this framework. We derive the dispersion relation for gravitational waves and study their behavior in the Friedmann-Lema\^itre-Roberson-Waker cosmology within the context of Brane-Chen-Simons massive gravity. Utilizing the latest Union2 type Ia supernova dataset comprising $557$ SNIa events, we provide observational support for our theoretical framework, indicating that the Brane-Chern-Simons massive gravity theory is consistent with cosmological observations. |
2205.08130 | Stephan Rosswog | S. Rosswog, P. Diener, F. Torsello | Thinking outside the box: Numerical Relativity with particles | 36 pages, accepted for publication in Symmetry | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-nd/4.0/ | To date, essentially all simulation codes that solve the full set of
Einstein's equations are performed in the framework of Eulerian hydrodynamics.
The exception is our recently developed Numerical Relativity code SPHINCS_BSSN
which solves the commonly used BSSN formulation of the Einstein equations on a
structured mesh and the matter equations via Lagrangian particles. We show
here, for the first time, SPHINCS_BSSN neutron star merger simulations with
piecewise polytropic approximations to four nuclear matter equations of state.
In this set of neutron star merger simulations we focus on perfectly symmetric
binary systems that are irrotational and have 1.3 $M_\odot$ masses. We
introduce some further methodological refinements (a new way of steering
dissipation, an improved particle-mesh mapping) and we explore the impact of
the exponent that enters in the calculation of the thermal pressure
contribution. We find that it leaves a noticeable imprint on the gravitational
wave amplitude (calculated via both quadrupole approximation and the
$\Psi_4$-formalism) and has a noticeable impact on the amount of dynamic
ejecta. Consistent with earlier findings, we only find a few times $10^{-3}$
\Msun as dynamic ejecta in the studied equal mass binary systems, with softer
equations of state (which are more prone to shock formation) ejecting larger
amounts of matter. In all of the cases, we see a credible high-velocity
($\sim0.5 .. 0.7c$) ejecta component of $\sim 10^{-4}$ \Msun that is launched
at contact from the interface between the two neutron stars. Such a
high-velocity component has been suggested to produce an early, blue precursor
to the main kilonova emission and it could also potentially cause a kilonova
afterglow.
| [
{
"created": "Tue, 17 May 2022 06:58:35 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jun 2022 21:49:15 GMT",
"version": "v2"
}
] | 2022-06-17 | [
[
"Rosswog",
"S.",
""
],
[
"Diener",
"P.",
""
],
[
"Torsello",
"F.",
""
]
] | To date, essentially all simulation codes that solve the full set of Einstein's equations are performed in the framework of Eulerian hydrodynamics. The exception is our recently developed Numerical Relativity code SPHINCS_BSSN which solves the commonly used BSSN formulation of the Einstein equations on a structured mesh and the matter equations via Lagrangian particles. We show here, for the first time, SPHINCS_BSSN neutron star merger simulations with piecewise polytropic approximations to four nuclear matter equations of state. In this set of neutron star merger simulations we focus on perfectly symmetric binary systems that are irrotational and have 1.3 $M_\odot$ masses. We introduce some further methodological refinements (a new way of steering dissipation, an improved particle-mesh mapping) and we explore the impact of the exponent that enters in the calculation of the thermal pressure contribution. We find that it leaves a noticeable imprint on the gravitational wave amplitude (calculated via both quadrupole approximation and the $\Psi_4$-formalism) and has a noticeable impact on the amount of dynamic ejecta. Consistent with earlier findings, we only find a few times $10^{-3}$ \Msun as dynamic ejecta in the studied equal mass binary systems, with softer equations of state (which are more prone to shock formation) ejecting larger amounts of matter. In all of the cases, we see a credible high-velocity ($\sim0.5 .. 0.7c$) ejecta component of $\sim 10^{-4}$ \Msun that is launched at contact from the interface between the two neutron stars. Such a high-velocity component has been suggested to produce an early, blue precursor to the main kilonova emission and it could also potentially cause a kilonova afterglow. |
gr-qc/0102046 | Lars Bildsten | Lars Bildsten (Institute for Theoretical Physics, UCSB) | Dissipation for Euler's Disk and a Desktop Demonstration of Coalescing
Neutron Stars | Submitted to American Journal of Physics | null | null | null | gr-qc astro-ph | null | I show that the recent calculation of Moffatt's regarding the viscous
dissipation of a spinning coin overlooked the importance of the finite width of
the viscous boundary layer. My new estimates are more in accord with that
observed. I also point out that the frequency ``chirp'' of the specially
designed toy ``Euler's Disk'' is similar to that expected during the last few
minutes of the life of a coalescing binary of two neutron stars. As such, this
toy is an excellent desktop demonstration for the expected phenomena.
| [
{
"created": "Sun, 11 Feb 2001 23:40:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bildsten",
"Lars",
"",
"Institute for Theoretical Physics, UCSB"
]
] | I show that the recent calculation of Moffatt's regarding the viscous dissipation of a spinning coin overlooked the importance of the finite width of the viscous boundary layer. My new estimates are more in accord with that observed. I also point out that the frequency ``chirp'' of the specially designed toy ``Euler's Disk'' is similar to that expected during the last few minutes of the life of a coalescing binary of two neutron stars. As such, this toy is an excellent desktop demonstration for the expected phenomena. |
1408.4759 | Jolyon Bloomfield | Jolyon K. Bloomfield, Clare Burrage, Anne-Christine Davis | The Shape Dependence of Vainshtein Screening | 11 pages, 1 figure; v2 publication version, minimal changes for
clarity | Phys. Rev. D 91, 083510 (2015) | 10.1103/PhysRevD.91.083510 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar field theories that possess a Vainshtein mechanism are able to
dynamically suppress the associated fifth forces in the presence of massive
sources through derivative non-linearities. The resulting equations of motion
for the scalar are highly non-linear and therefore very few analytic solutions
are known. Here we present a brief investigation of the structure of Vainshtein
screening in symmetrical configurations, focusing in particular on the
spherical, cylindrical and planar solutions that are relevant for observations
of the cosmic web. We consider Vainshtein screening in both the Galileon model,
where the non-linear terms involve second derivatives of the scalar, and a
k-essence theory, where the non-linear terms involve only first derivatives of
the scalar. We find that screening, and consequently the suppression of the
scalar force, is most efficient around spherical sources, weaker around
cylindrical sources and can be absent altogether around planar sources.
| [
{
"created": "Mon, 18 Aug 2014 19:59:58 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Aug 2015 01:28:42 GMT",
"version": "v2"
}
] | 2015-08-18 | [
[
"Bloomfield",
"Jolyon K.",
""
],
[
"Burrage",
"Clare",
""
],
[
"Davis",
"Anne-Christine",
""
]
] | Scalar field theories that possess a Vainshtein mechanism are able to dynamically suppress the associated fifth forces in the presence of massive sources through derivative non-linearities. The resulting equations of motion for the scalar are highly non-linear and therefore very few analytic solutions are known. Here we present a brief investigation of the structure of Vainshtein screening in symmetrical configurations, focusing in particular on the spherical, cylindrical and planar solutions that are relevant for observations of the cosmic web. We consider Vainshtein screening in both the Galileon model, where the non-linear terms involve second derivatives of the scalar, and a k-essence theory, where the non-linear terms involve only first derivatives of the scalar. We find that screening, and consequently the suppression of the scalar force, is most efficient around spherical sources, weaker around cylindrical sources and can be absent altogether around planar sources. |
2402.07965 | Dalibor Jav\r{u}rek | Dalibor Jav\r{u}rek | Extension of Theory of Gravitomagnetism and Spinor Quantum Mechanics
with Dynamics of Free Electromagnetic Field | 8 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The theory of Gravitomagnetism and spinor quantum mechanics describing the
interaction between the Dirac spinor field, the electromagnetic field, and a
weak gravitational field is extended by including the Lagrangian density of the
free electromagnetic field. It is shown that the newly added term in the
Lagrangian density is necessary to restore a symmetric energy-momentum tensor
in the interaction term of the Lagrangian density within the theory. We prove
that when the electromagnetic energy term is missing, the tensor in the
interaction Lagrangian density does not represent the energy-momentum tensor of
the Dirac field minimally coupled to the electromagnetic field on flat
space-time. Moreover, it follows that the Lagrangian density remains unchanged
regardless of whether the theory is developed from the principle of general
covariance or is defined as a flat space-time theory with the gravitational
field treated as a regular tensor field, in analogy to the electromagnetic
field. This contradicts previous findings.
| [
{
"created": "Mon, 12 Feb 2024 11:58:32 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Feb 2024 08:18:54 GMT",
"version": "v2"
}
] | 2024-02-15 | [
[
"Javůrek",
"Dalibor",
""
]
] | The theory of Gravitomagnetism and spinor quantum mechanics describing the interaction between the Dirac spinor field, the electromagnetic field, and a weak gravitational field is extended by including the Lagrangian density of the free electromagnetic field. It is shown that the newly added term in the Lagrangian density is necessary to restore a symmetric energy-momentum tensor in the interaction term of the Lagrangian density within the theory. We prove that when the electromagnetic energy term is missing, the tensor in the interaction Lagrangian density does not represent the energy-momentum tensor of the Dirac field minimally coupled to the electromagnetic field on flat space-time. Moreover, it follows that the Lagrangian density remains unchanged regardless of whether the theory is developed from the principle of general covariance or is defined as a flat space-time theory with the gravitational field treated as a regular tensor field, in analogy to the electromagnetic field. This contradicts previous findings. |
1302.1206 | Bibhas Majhi Ranjan | Bibhas Ranjan Majhi, T. Padmanabhan | Thermality and Heat Content of horizons from infinitesimal coordinate
transformations | Published version | Eur. Phys. J. C 73 (2013) 2651 | 10.1140/epjc/s10052-013-2651-z | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/3.0/ | Thermal properties of a static horizon, (like the entropy S, heat content TS
etc.) can be obtained either from the surface term of the Einstein-Hilbert
action or by evaluating the Noether charge, corresponding to the
diffeomorphisms generated by the timelike Killing vector field. We show that,
for a wide class of geometries, the same results can be obtained using the
vector field which produces an infinitesimal coordinate transformation between
two physically relevant reference frames, viz. the freely falling frame near
the horizon and the static, accelerated, frame. In particular, the
infinitesimal coordinate transformation from inertial coordinates to uniformly
accelerated frame can be used to obtain the heat content and entropy of the
Rindler horizon. This result offers insight into understanding the observer
dependent degrees of freedom which contribute to the entropy of null surfaces.
| [
{
"created": "Tue, 5 Feb 2013 21:06:17 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Nov 2013 07:35:03 GMT",
"version": "v2"
}
] | 2013-11-22 | [
[
"Majhi",
"Bibhas Ranjan",
""
],
[
"Padmanabhan",
"T.",
""
]
] | Thermal properties of a static horizon, (like the entropy S, heat content TS etc.) can be obtained either from the surface term of the Einstein-Hilbert action or by evaluating the Noether charge, corresponding to the diffeomorphisms generated by the timelike Killing vector field. We show that, for a wide class of geometries, the same results can be obtained using the vector field which produces an infinitesimal coordinate transformation between two physically relevant reference frames, viz. the freely falling frame near the horizon and the static, accelerated, frame. In particular, the infinitesimal coordinate transformation from inertial coordinates to uniformly accelerated frame can be used to obtain the heat content and entropy of the Rindler horizon. This result offers insight into understanding the observer dependent degrees of freedom which contribute to the entropy of null surfaces. |
2205.13534 | William Barker Dr | W. E. V. Barker | Geometric multipliers and partial teleparallelism in Poincar\'e gauge
theory | Version accepted by PRD, added Fig. 1, added Section IIA, added
references, corrected typos in Appendix E | null | 10.1103/PhysRevD.108.024053 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The dynamics of the torsion-powered teleparallel theory are only viable
because thirty-six multiplier fields disable all components of the
Riemann--Cartan curvature. We generalise this suggestive approach by
considering Poincar\'e gauge theory in which sixty such `geometric multipliers'
can be invoked to disable any given irreducible part of the curvature, or
indeed the torsion. Torsion theories motivated by a weak-field analysis
frequently suffer from unwanted dynamics in the strong-field regime, such as
the activation of ghosts. By considering the propagation of massive,
parity-even vector torsion, we explore how geometric multipliers may be able to
limit strong-field departures from the weak-field Hamiltonian constraint
structure, and consider their tree-level phenomena.
| [
{
"created": "Thu, 26 May 2022 17:53:04 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Aug 2023 15:15:14 GMT",
"version": "v2"
}
] | 2023-08-15 | [
[
"Barker",
"W. E. V.",
""
]
] | The dynamics of the torsion-powered teleparallel theory are only viable because thirty-six multiplier fields disable all components of the Riemann--Cartan curvature. We generalise this suggestive approach by considering Poincar\'e gauge theory in which sixty such `geometric multipliers' can be invoked to disable any given irreducible part of the curvature, or indeed the torsion. Torsion theories motivated by a weak-field analysis frequently suffer from unwanted dynamics in the strong-field regime, such as the activation of ghosts. By considering the propagation of massive, parity-even vector torsion, we explore how geometric multipliers may be able to limit strong-field departures from the weak-field Hamiltonian constraint structure, and consider their tree-level phenomena. |
2011.12142 | Guo-Ping Li | Guo-Ping Li, Ke-Jian He and Bing-Bing Chen | Testing thermodynamic laws and weak cosmic censorship conjecture of
conformal anomaly corrected AdS black hole | 10 pages, 13 figures | Eur.Phys.J.Plus,136 (2021) 1, 2 | 10.1140/epjp/s13360-020-00953-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By dropping particles into black hole, we have employed the recently new
assumption [1] that the change of the black hole mass(enthalpy) should be the
same amount as the energy of an infalling particle($\omega = dM$), to carefully
test the laws of thermodynamics and the weak cosmic censorship conjecture of a
conformal anomaly corrected AdS black hole in different phase spaces. Using the
energy-momentum relation, the result shows that the first law, second law and
weak cosmic censorship conjecture of black hole are all valid in the normal
phase space, no violations occur. In the extended phase space, it firstly shows
that the first law of black hole thermodynamics is always true in our case.
Then, we interestingly find that if the condition ${d\ell} > -\left(P^r
\ell^3\right)/{r_+^3}$ satisfied the variation of entropy is always positive,
which means there would be no violation of the second law in the extend phase
spaces. Also, it is true that there are always horizons by which the
singularity is also covered. So, the configurations of the extremal and
near-extremal black holes will not be changed, and there has no violation of
the weak cosmic censorship conjecture. Finally, all of those conclusions are
independent of the scalar curvature parameter $k$ and the conformal anomaly
parameter $\tilde{\alpha}$
| [
{
"created": "Sun, 22 Nov 2020 03:06:23 GMT",
"version": "v1"
},
{
"created": "Sun, 16 May 2021 02:10:55 GMT",
"version": "v2"
}
] | 2021-05-18 | [
[
"Li",
"Guo-Ping",
""
],
[
"He",
"Ke-Jian",
""
],
[
"Chen",
"Bing-Bing",
""
]
] | By dropping particles into black hole, we have employed the recently new assumption [1] that the change of the black hole mass(enthalpy) should be the same amount as the energy of an infalling particle($\omega = dM$), to carefully test the laws of thermodynamics and the weak cosmic censorship conjecture of a conformal anomaly corrected AdS black hole in different phase spaces. Using the energy-momentum relation, the result shows that the first law, second law and weak cosmic censorship conjecture of black hole are all valid in the normal phase space, no violations occur. In the extended phase space, it firstly shows that the first law of black hole thermodynamics is always true in our case. Then, we interestingly find that if the condition ${d\ell} > -\left(P^r \ell^3\right)/{r_+^3}$ satisfied the variation of entropy is always positive, which means there would be no violation of the second law in the extend phase spaces. Also, it is true that there are always horizons by which the singularity is also covered. So, the configurations of the extremal and near-extremal black holes will not be changed, and there has no violation of the weak cosmic censorship conjecture. Finally, all of those conclusions are independent of the scalar curvature parameter $k$ and the conformal anomaly parameter $\tilde{\alpha}$ |
gr-qc/0007082 | Dobromila Nowak-Szczepaniak | J. Kowalski-Glikman and D. Nowak-Szczepaniak (University of Wroclaw) | Topological Black Holes in Quantum Gravity | 4pages, no figures, plain LaTeX | Phys.Lett. A277 (2000) 83-86 | 10.1016/S0375-9601(00)00687-3 | null | gr-qc | null | We derive the black hole solutions with horizons of non-trivial topology and
investigate their properties in the framework of an approach to quantum gravity
being an extension of Bohm's formulation of quantum mechanics. The solutions we
found tend asymptotically (for large $r$) to topological black holes. We also
analyze the thermodynamics of these space-times.
| [
{
"created": "Mon, 31 Jul 2000 11:24:11 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kowalski-Glikman",
"J.",
"",
"University of Wroclaw"
],
[
"Nowak-Szczepaniak",
"D.",
"",
"University of Wroclaw"
]
] | We derive the black hole solutions with horizons of non-trivial topology and investigate their properties in the framework of an approach to quantum gravity being an extension of Bohm's formulation of quantum mechanics. The solutions we found tend asymptotically (for large $r$) to topological black holes. We also analyze the thermodynamics of these space-times. |
1707.08472 | Ghulam Abbas | G. Abbas and M. Tahir | Gravitational Perfect Fluid Collapse in Gauss-Bonnet Gravity | 16 pages, 3 Figures; some future research directions mentioned; to
appear in European Physical Journal C | Eur. Phys. J. C (2017) 77:537 | 10.1140/epjc/s10052-017-5114-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein Gauss-Bonnet theory of gravity is the low energy limit of
heterotic super-symmetric string theory. This paper deals gravitational
collapse of perfect fluid in Einstein Gauss-Bonnet gravity by considering the
Lemaitre - Tolman - Bondi metric. For this purpose, the closed form of exact
solution of equations of motion has been determined by using the conservation
of stress-energy tensor and the condition of marginally bound shells. It has
been investigated that the presence of Gauss-Bonnet coupling term $\alpha>0$
and pressure of the fluid modifies the structure and time formation of
singularity. In this analysis singularity form earlier than horizon, so end
state of the collapse is a naked singularity depending on the initial data. But
this singularity is weak and timelike that goes against the investigation of
general relativity.
| [
{
"created": "Tue, 25 Jul 2017 17:24:22 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jul 2017 13:13:14 GMT",
"version": "v2"
}
] | 2018-01-12 | [
[
"Abbas",
"G.",
""
],
[
"Tahir",
"M.",
""
]
] | The Einstein Gauss-Bonnet theory of gravity is the low energy limit of heterotic super-symmetric string theory. This paper deals gravitational collapse of perfect fluid in Einstein Gauss-Bonnet gravity by considering the Lemaitre - Tolman - Bondi metric. For this purpose, the closed form of exact solution of equations of motion has been determined by using the conservation of stress-energy tensor and the condition of marginally bound shells. It has been investigated that the presence of Gauss-Bonnet coupling term $\alpha>0$ and pressure of the fluid modifies the structure and time formation of singularity. In this analysis singularity form earlier than horizon, so end state of the collapse is a naked singularity depending on the initial data. But this singularity is weak and timelike that goes against the investigation of general relativity. |
1806.09530 | Ruth Durrer | George F R Ellis and Ruth Durrer | Note on the Kaiser-Peacock paper regarding gravitational lensing effects | 11 page,s 1 figure | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper revisits the controversy concerning whether gravitational lensing
effects make a significant difference to estimation of distance to the Cosmic
Microwave Background last scattering surface in cosmology. A recent paper by
Kaiser and Peacock supports a previous paper by Weinberg stating that such
affects average to zero because of energy conservation. In this note, problems
are pointed out in the Kaiser and Peacock analysis related to their choice of
endpoint of integration, and to the `wrinkly surface' argument.
| [
{
"created": "Mon, 25 Jun 2018 15:37:05 GMT",
"version": "v1"
}
] | 2018-06-26 | [
[
"Ellis",
"George F R",
""
],
[
"Durrer",
"Ruth",
""
]
] | This paper revisits the controversy concerning whether gravitational lensing effects make a significant difference to estimation of distance to the Cosmic Microwave Background last scattering surface in cosmology. A recent paper by Kaiser and Peacock supports a previous paper by Weinberg stating that such affects average to zero because of energy conservation. In this note, problems are pointed out in the Kaiser and Peacock analysis related to their choice of endpoint of integration, and to the `wrinkly surface' argument. |
1007.0863 | Betti Hartmann | Betti Hartmann and Parinya Sirimachan | Geodesic motion in the space-time of a cosmic string | 20 pages including 14 figures; v2: references added, discussion on
null geodesics extended, numerical results added | JHEP 1008:110,2010 | 10.1007/JHEP08(2010)110 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geodesic equation in the space-time of an Abelian-Higgs string
and discuss the motion of massless and massive test particles. The geodesics
can be classified according to the particles energy, angular momentum and
linear momentum along the string axis. We observe that bound orbits of massive
particles are only possible if the Higgs boson mass is smaller than the gauge
boson mass, while massless particles always move on escape orbits. Moreover,
neither massive nor massless particles can ever reach the string axis for
non-vanishing angular momentum. We also discuss the dependence of light
deflection by a cosmic string as well as the perihelion shift of bound orbits
of massive particles on the ratio between Higgs and gauge boson mass and the
ratio between symmetry breaking scale and Planck mass, respectively.
| [
{
"created": "Tue, 6 Jul 2010 11:19:30 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jul 2010 09:25:45 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Hartmann",
"Betti",
""
],
[
"Sirimachan",
"Parinya",
""
]
] | We study the geodesic equation in the space-time of an Abelian-Higgs string and discuss the motion of massless and massive test particles. The geodesics can be classified according to the particles energy, angular momentum and linear momentum along the string axis. We observe that bound orbits of massive particles are only possible if the Higgs boson mass is smaller than the gauge boson mass, while massless particles always move on escape orbits. Moreover, neither massive nor massless particles can ever reach the string axis for non-vanishing angular momentum. We also discuss the dependence of light deflection by a cosmic string as well as the perihelion shift of bound orbits of massive particles on the ratio between Higgs and gauge boson mass and the ratio between symmetry breaking scale and Planck mass, respectively. |
2403.12270 | Eduardo J S Villase\~nor | Marc Basquens, Antonio Lasanta, Emanuel Momp\'o, Valle Varo, Eduardo
J. S. Villase\~nor | Spacetime symmetries and geometric diffusion | 29 pages. Accepted for publication in Journal of Physics A:
Mathematical and Theoretical | J. Phys. A: Math. Theor. 57 (2024) 285204 | 10.1088/1751-8121/ad5a57 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We examine relativistic diffusion through the frame and observer bundles
associated with a Lorentzian manifold $(M,g)$. Our focus is on spacetimes with
a non-trivial isometry group, and we detail the conditions required to find
symmetric solutions of the relativistic diffusion equation. Additionally, we
analyze the conservation laws associated with the presence of Killing vector
fields on $(M,g)$ and their implications for the expressions of the geodesic
spray and the vertical Laplacian on both the frame and the observer bundles.
Finally, we present several relevant examples of symmetric spacetimes.
| [
{
"created": "Mon, 18 Mar 2024 21:35:48 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Jun 2024 00:34:34 GMT",
"version": "v2"
}
] | 2024-07-01 | [
[
"Basquens",
"Marc",
""
],
[
"Lasanta",
"Antonio",
""
],
[
"Mompó",
"Emanuel",
""
],
[
"Varo",
"Valle",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We examine relativistic diffusion through the frame and observer bundles associated with a Lorentzian manifold $(M,g)$. Our focus is on spacetimes with a non-trivial isometry group, and we detail the conditions required to find symmetric solutions of the relativistic diffusion equation. Additionally, we analyze the conservation laws associated with the presence of Killing vector fields on $(M,g)$ and their implications for the expressions of the geodesic spray and the vertical Laplacian on both the frame and the observer bundles. Finally, we present several relevant examples of symmetric spacetimes. |
gr-qc/9502003 | Maria Guimaraes | M. E. X. Guimar\~aes (Lab. Gravitation et Cosmologie Relativistes,
Paris, France) | Vacuum Polarization at Finite Temperature around a Magnetic Flux Cosmic
String | 22 pages, latex, no figures | Class.Quant.Grav.12:1705-1714,1995 | 10.1088/0264-9381/12/7/012 | GCR - 95 - 02 - 01 | gr-qc hep-th | null | We consider a general situation where a charged massive scalar field
$\phi(x)$ at finite temperature interacts with a magnetic flux cosmic string.
We determine a general expression for the Euclidean thermal Green's function of
the massive scalar field and a handy expression for a massless scalar field.
With this result, we evaluate the thermal average $<\phi^{2}(x)>$ and the
thermal average of the energy-momentum tensor of a nonconformal massless scalar
field.
| [
{
"created": "Wed, 1 Feb 1995 10:34:36 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Guimarães",
"M. E. X.",
"",
"Lab. Gravitation et Cosmologie Relativistes,\n Paris, France"
]
] | We consider a general situation where a charged massive scalar field $\phi(x)$ at finite temperature interacts with a magnetic flux cosmic string. We determine a general expression for the Euclidean thermal Green's function of the massive scalar field and a handy expression for a massless scalar field. With this result, we evaluate the thermal average $<\phi^{2}(x)>$ and the thermal average of the energy-momentum tensor of a nonconformal massless scalar field. |
gr-qc/0402032 | Kouji Nakamura | Kouji Nakamura | General framework of higher order gauge invariant perturbation theory | Prepared for the proceeding of the 13th Workshop on General
Relativity and Gravitation in Japan (Osaka City University). 4 pages, no
figure, latex format | null | null | null | gr-qc astro-ph hep-th math-ph math.MP | null | Based on the gauge invariant variables proposed in [K. Nakamura, Prog. Theor.
Phys. vol.110 (2003), 723.], general framework of the second order gauge
invariant perturbation theory on arbitrary background spacetime is considered.
We derived formulae of the perturbative Einstein tensor of each order, which
have the similar form to the definitions of gauge invariant variables for
arbitrary perturbative fields. As a result, each order Einstein equation is
necessarily given in terms of gauge invariant variables.
| [
{
"created": "Thu, 5 Feb 2004 10:53:57 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nakamura",
"Kouji",
""
]
] | Based on the gauge invariant variables proposed in [K. Nakamura, Prog. Theor. Phys. vol.110 (2003), 723.], general framework of the second order gauge invariant perturbation theory on arbitrary background spacetime is considered. We derived formulae of the perturbative Einstein tensor of each order, which have the similar form to the definitions of gauge invariant variables for arbitrary perturbative fields. As a result, each order Einstein equation is necessarily given in terms of gauge invariant variables. |
1806.04969 | Andronikos Paliathanasis | Andronikos Paliathanasis | Dynamical analysis and cosmological viability of varying $G$ and
$\Lambda$ cosmology | 13 pages, 4 figures, discussion improved, to appear in EPJC | null | 10.1140/epjc/s10052-018-6165-6 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological viability of varying $G\left( t\right) $ and $\Lambda \left(
t\right) $ cosmology is discussed by determining the cosmological eras provided
by the theory. Such a study is performed with the determination of the critical
points while stability analysis is performed. The application of
Renormalization group in the ADM formalism of General Relativity provides a
modified second-order theory of gravity where varying $G\left( t\right) $ plays
the role of a minimally coupled field, different from that of Scalar-tensor
theories, while $\Lambda\left( t\right) =\Lambda\left( G\left( t\right) \right)
$ is a potential term. We find that the theory provides two de Sitter phases
and a tracking solution. In the presence of matter source, two new critical
points are introduced, where the matter source contributes to the universe. One
of those points describes the $\Lambda$CDM cosmology and in order for the
solution at the point to be cosmologically viable, it has to be unstable.
Moreover, the second point, where matter exists, describes a universe where the
dark energy parameter for the equation of state has a different value from that
of the cosmological constant.
| [
{
"created": "Wed, 13 Jun 2018 12:05:21 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Aug 2018 09:51:32 GMT",
"version": "v2"
}
] | 2018-09-26 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | The cosmological viability of varying $G\left( t\right) $ and $\Lambda \left( t\right) $ cosmology is discussed by determining the cosmological eras provided by the theory. Such a study is performed with the determination of the critical points while stability analysis is performed. The application of Renormalization group in the ADM formalism of General Relativity provides a modified second-order theory of gravity where varying $G\left( t\right) $ plays the role of a minimally coupled field, different from that of Scalar-tensor theories, while $\Lambda\left( t\right) =\Lambda\left( G\left( t\right) \right) $ is a potential term. We find that the theory provides two de Sitter phases and a tracking solution. In the presence of matter source, two new critical points are introduced, where the matter source contributes to the universe. One of those points describes the $\Lambda$CDM cosmology and in order for the solution at the point to be cosmologically viable, it has to be unstable. Moreover, the second point, where matter exists, describes a universe where the dark energy parameter for the equation of state has a different value from that of the cosmological constant. |
2009.04999 | YuZhu Chen | Yu-Zhu Chen, Shi-Lin Li, Yu-Jie Chen, Fu-Lin Zhang, Wu-Sheng Dai | Toy models of black hole, white hole and wormhole: thermal effects and
information loss problem | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, by setting proper boundaries in the Minkowski spacetime, we
construct three toy model spacetimes, a toy black hole, a toy white hole, and a
toy wormhole. Based on these model spacetimes, we discuss the Hawking radiation
and the information loss problem. By counting the number of the field modes
inside and outside the horizon, we show the thermal radiation of the toy black
hole. We show that the white hole have a thermal absorption. We show that in
the whole toy wormhole spacetime, there is no information lost. In addition, we
show the black hole radiation and the white hole absorption are independent of
the choices of boundary conditions at the singularity. We also show the
physical effects caused by two particular boundary conditions.
| [
{
"created": "Thu, 10 Sep 2020 17:09:50 GMT",
"version": "v1"
}
] | 2020-09-11 | [
[
"Chen",
"Yu-Zhu",
""
],
[
"Li",
"Shi-Lin",
""
],
[
"Chen",
"Yu-Jie",
""
],
[
"Zhang",
"Fu-Lin",
""
],
[
"Dai",
"Wu-Sheng",
""
]
] | In this paper, by setting proper boundaries in the Minkowski spacetime, we construct three toy model spacetimes, a toy black hole, a toy white hole, and a toy wormhole. Based on these model spacetimes, we discuss the Hawking radiation and the information loss problem. By counting the number of the field modes inside and outside the horizon, we show the thermal radiation of the toy black hole. We show that the white hole have a thermal absorption. We show that in the whole toy wormhole spacetime, there is no information lost. In addition, we show the black hole radiation and the white hole absorption are independent of the choices of boundary conditions at the singularity. We also show the physical effects caused by two particular boundary conditions. |
1811.04360 | Barak Shoshany | Laurent Freidel, Florian Girelli, Barak Shoshany | 2+1D Loop Quantum Gravity on the Edge | 44 pages, 7 figures; corrected minor typos and updated references | Phys. Rev. D 99, 046003 (2019) | 10.1103/PhysRevD.99.046003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a new perspective on the discretization of the phase space
structure of gravity in 2+1 dimensions as a piecewise-flat geometry in 2
spatial dimensions. Starting from a subdivision of the continuum geometric and
phase space structure into elementary cells, we obtain the loop gravity phase
space coupled to a collection of effective particles carrying mass and spin,
which measure the curvature and torsion of the geometry. We show that the new
degrees of freedom associated to the particle-like elements can be understood
as edge modes, which appear in the decomposition of the continuum theory into
subsystems and do not cancel out in the gluing of cells along codimension 2
defects. These new particle-like edge modes are gravitationally dressed in an
explicit way. This provides a detailed explanation of the relations and
differences between the loop gravity phase space and the one deduced from the
continuum theory.
| [
{
"created": "Sun, 11 Nov 2018 06:03:07 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 06:07:58 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Feb 2019 14:03:36 GMT",
"version": "v3"
},
{
"created": "Wed, 1 Apr 2020 19:06:15 GMT",
"version": "v4"
}
] | 2020-04-03 | [
[
"Freidel",
"Laurent",
""
],
[
"Girelli",
"Florian",
""
],
[
"Shoshany",
"Barak",
""
]
] | We develop a new perspective on the discretization of the phase space structure of gravity in 2+1 dimensions as a piecewise-flat geometry in 2 spatial dimensions. Starting from a subdivision of the continuum geometric and phase space structure into elementary cells, we obtain the loop gravity phase space coupled to a collection of effective particles carrying mass and spin, which measure the curvature and torsion of the geometry. We show that the new degrees of freedom associated to the particle-like elements can be understood as edge modes, which appear in the decomposition of the continuum theory into subsystems and do not cancel out in the gluing of cells along codimension 2 defects. These new particle-like edge modes are gravitationally dressed in an explicit way. This provides a detailed explanation of the relations and differences between the loop gravity phase space and the one deduced from the continuum theory. |
gr-qc/9505044 | Michael Reisenberger | Michael Reisenberger | New constraints for canonical general relativity | Version to appear in Nuclear Physics B. Discussion of 4-diffeo
invariance, Dirac brackets improved. Proof of theorem connecting self-dual
2-forms and orthonormal tetrads replaced. Latex 57 pages, 7 uuencoded
postscript figures. Uses macro psfig.tex available from this archive (and
appended to this posting for your convenience). After latexing use dvips -
not - dvi2ps to get postscript files | Nucl.Phys. B457 (1995) 643-687 | 10.1016/0550-3213(95)00448-3 | Utrecht University Institute of Theoretical Physics preprint
THU-95/14 | gr-qc | null | Ashtekar's canonical theory of classical complex Euclidean GR (no Lorentzian
reality conditions) is found to be invariant under the full algebra of
infinitesimal 4-diffeomorphisms, but non-invariant under some finite proper
4-diffeos when the densitized dreibein, $\tilE^a_i$, is degenerate. The
breakdown of 4-diffeo invariance appears to be due to the inability of the
Ashtekar Hamiltonian to generate births and deaths of $\tilE$ flux loops
(leaving open the possibility that a new `causality condition' forbidding the
birth of flux loops might justify the non-invariance of the theory).
A fully 4-diffeo invariant canonical theory in Ashtekar's variables, derived
from Plebanski's action, is found to have constraints that are stronger than
Ashtekar's for $rank\tilE < 2$. The corresponding Hamiltonian generates births
and deaths of $\tilE$ flux loops.
It is argued that this implies a finite amplitude for births and deaths of
loops in the physical states of quantum GR in the loop representation, thus
modifying this (partly defined) theory substantially.
Some of the new constraints are second class, leading to difficulties in
quantization in the connection representation. This problem might be overcome
in a very nice way by transforming to the classical loop variables, or the
`Faraday line' variables of Newman and Rovelli, and then solving the offending
constraints.
Note that, though motivated by quantum considerations, the present paper is
classical in substance.
| [
{
"created": "Wed, 24 May 1995 11:02:42 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Nov 1995 02:38:24 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Reisenberger",
"Michael",
""
]
] | Ashtekar's canonical theory of classical complex Euclidean GR (no Lorentzian reality conditions) is found to be invariant under the full algebra of infinitesimal 4-diffeomorphisms, but non-invariant under some finite proper 4-diffeos when the densitized dreibein, $\tilE^a_i$, is degenerate. The breakdown of 4-diffeo invariance appears to be due to the inability of the Ashtekar Hamiltonian to generate births and deaths of $\tilE$ flux loops (leaving open the possibility that a new `causality condition' forbidding the birth of flux loops might justify the non-invariance of the theory). A fully 4-diffeo invariant canonical theory in Ashtekar's variables, derived from Plebanski's action, is found to have constraints that are stronger than Ashtekar's for $rank\tilE < 2$. The corresponding Hamiltonian generates births and deaths of $\tilE$ flux loops. It is argued that this implies a finite amplitude for births and deaths of loops in the physical states of quantum GR in the loop representation, thus modifying this (partly defined) theory substantially. Some of the new constraints are second class, leading to difficulties in quantization in the connection representation. This problem might be overcome in a very nice way by transforming to the classical loop variables, or the `Faraday line' variables of Newman and Rovelli, and then solving the offending constraints. Note that, though motivated by quantum considerations, the present paper is classical in substance. |
2204.09095 | Deepen Garg | Deepen Garg and I. Y. Dodin | Gravitational wave modes in matter | 13 pages, 1 figure | J. Cosmol. Astropart. Phys 08 (2022) 017 | 10.1088/1475-7516/2022/08/017 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general linear gauge-invariant equation for dispersive gravitational waves
(GWs) propagating in matter is derived. This equation describes, on the same
footing, both the usual tensor modes and the gravitational modes strongly
coupled with matter. It is shown that the effect of matter on the former is
comparable to diffraction and therefore negligible within the
geometrical-optics approximation. However, this approximation is applicable to
modes strongly coupled with matter due to their large refractive index. GWs in
ideal gas are studied using the kinetic average-Lagrangian approach and the
gravitational polarizability of matter that we have introduced earlier. In
particular, we show that this formulation subsumes the kinetic Jeans
instability as a collective GW mode with a peculiar polarization, which is
derived from the dispersion matrix rather than assumed a priori. This forms a
foundation for systematically extending GW theory to GW interactions with
plasmas, where symmetry considerations alone are insufficient to predict the
wave polarization.
| [
{
"created": "Tue, 19 Apr 2022 18:59:04 GMT",
"version": "v1"
}
] | 2022-08-12 | [
[
"Garg",
"Deepen",
""
],
[
"Dodin",
"I. Y.",
""
]
] | A general linear gauge-invariant equation for dispersive gravitational waves (GWs) propagating in matter is derived. This equation describes, on the same footing, both the usual tensor modes and the gravitational modes strongly coupled with matter. It is shown that the effect of matter on the former is comparable to diffraction and therefore negligible within the geometrical-optics approximation. However, this approximation is applicable to modes strongly coupled with matter due to their large refractive index. GWs in ideal gas are studied using the kinetic average-Lagrangian approach and the gravitational polarizability of matter that we have introduced earlier. In particular, we show that this formulation subsumes the kinetic Jeans instability as a collective GW mode with a peculiar polarization, which is derived from the dispersion matrix rather than assumed a priori. This forms a foundation for systematically extending GW theory to GW interactions with plasmas, where symmetry considerations alone are insufficient to predict the wave polarization. |
1809.10457 | Sanjar Shaymatov | Sanjar Shaymatov, Naresh Dadhich, Bobomurat Ahmedov | The higher dimensional Myers-Perry black hole with single rotation
always obeys the Cosmic Censorship Conjecture | 5 pages, no figures; Coincides with published version | Eur. Phys. J. C 79 (2019) 585 | 10.1140/epjc/s10052-019-7088-6 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Even though the Myers-Perry five dimensional rotating black hole with two
rotations could be overspun by test particle accretion, yet it turns out as we
show in this letter that it cannot do so for a single rotation. On the other
hand it is known that there exists no extremal limit for a black hole with
single rotation in dimensions greater than equal to six. It has been proven
that all higher dimensional ($>4$) rotating black holes with only one single
rotation can never be overspun under test particle linear accretion and hence
would always obey CCC in the weak form.
| [
{
"created": "Thu, 27 Sep 2018 11:17:10 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Feb 2019 14:24:42 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Jul 2019 09:50:42 GMT",
"version": "v3"
}
] | 2019-09-04 | [
[
"Shaymatov",
"Sanjar",
""
],
[
"Dadhich",
"Naresh",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] | Even though the Myers-Perry five dimensional rotating black hole with two rotations could be overspun by test particle accretion, yet it turns out as we show in this letter that it cannot do so for a single rotation. On the other hand it is known that there exists no extremal limit for a black hole with single rotation in dimensions greater than equal to six. It has been proven that all higher dimensional ($>4$) rotating black holes with only one single rotation can never be overspun under test particle linear accretion and hence would always obey CCC in the weak form. |
gr-qc/0301051 | M. Blagojevic | M. Blagojevic and M. Vasilic | Asymptotic symmetries in 3d gravity with torsion | 25 pages, RevTeX, no figures | Phys.Rev. D67 (2003) 084032 | 10.1103/PhysRevD.67.084032 | null | gr-qc hep-th | null | We study the nature of asymptotic symmetries in topological 3d gravity with
torsion. After introducing the concept of asymptotically anti-de Sitter
configuration, we find that the canonical realization of the asymptotic
symmetry is characterized by the Virasoro algebra with classical central
charge, the value of which is the same as in general relativity: c=3l/2G.
| [
{
"created": "Wed, 15 Jan 2003 15:08:19 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Blagojevic",
"M.",
""
],
[
"Vasilic",
"M.",
""
]
] | We study the nature of asymptotic symmetries in topological 3d gravity with torsion. After introducing the concept of asymptotically anti-de Sitter configuration, we find that the canonical realization of the asymptotic symmetry is characterized by the Virasoro algebra with classical central charge, the value of which is the same as in general relativity: c=3l/2G. |
0712.0654 | Muhammad Sharif | M. Sharif and Umber Sheikh | Complex Wave Numbers in the Vicinity of the Schwarzschild Event Horizon | 21 pages, 9 figures, accepted for publication Int. J. Mod. Phys. A | Int.J.Mod.Phys.A23:1417-1433,2008 | 10.1142/S0217751X0803855X | null | gr-qc astro-ph | null | This paper is devoted to investigate the cold plasma wave properties outside
the event horizon of the Schwarzschild planar analogue. The dispersion
relations are obtained from the corresponding Fourier analyzed equations for
non-rotating and rotating, non-magnetized and magnetized backgrounds. These
dispersion relations provide complex wave numbers. The wave numbers are shown
in graphs to discuss the nature and behavior of waves and the properties of
plasma lying in the vicinity of the Schwarzschild event horizon.
| [
{
"created": "Wed, 5 Dec 2007 05:43:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharif",
"M.",
""
],
[
"Sheikh",
"Umber",
""
]
] | This paper is devoted to investigate the cold plasma wave properties outside the event horizon of the Schwarzschild planar analogue. The dispersion relations are obtained from the corresponding Fourier analyzed equations for non-rotating and rotating, non-magnetized and magnetized backgrounds. These dispersion relations provide complex wave numbers. The wave numbers are shown in graphs to discuss the nature and behavior of waves and the properties of plasma lying in the vicinity of the Schwarzschild event horizon. |
gr-qc/0608100 | Martin Bojowald | Martin Bojowald | Large scale effective theory for cosmological bounces | 5 pages, 1 figure; v2: more details on effective equations | Phys.Rev.D74:081301,2007 | 10.1103/PhysRevD.75.081301 | IGPG-06/8-1 | gr-qc astro-ph hep-th | null | An exactly solvable bounce model in loop quantum cosmology is identified
which serves as a perturbative basis for realistic bounce scenarios. Its
bouncing solutions are derived analytically, demonstrating why recent numerical
simulations robustly led to smooth bounces under the assumption of
semiclassicality. Several effects, easily included in a perturbative analysis,
can however change this smoothness. The effective theory is not only applicable
to such situations where numerical techniques become highly involved but also
allows one to discuss conceptual issues. For instance, consequences of the
notoriously difficult physical inner product can be implemented at the
effective level. This indicates that even physical predictions from full
quantum gravity can be obtained from perturbative effective equations.
| [
{
"created": "Mon, 21 Aug 2006 16:14:07 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Mar 2007 07:53:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bojowald",
"Martin",
""
]
] | An exactly solvable bounce model in loop quantum cosmology is identified which serves as a perturbative basis for realistic bounce scenarios. Its bouncing solutions are derived analytically, demonstrating why recent numerical simulations robustly led to smooth bounces under the assumption of semiclassicality. Several effects, easily included in a perturbative analysis, can however change this smoothness. The effective theory is not only applicable to such situations where numerical techniques become highly involved but also allows one to discuss conceptual issues. For instance, consequences of the notoriously difficult physical inner product can be implemented at the effective level. This indicates that even physical predictions from full quantum gravity can be obtained from perturbative effective equations. |
gr-qc/0009091 | Adrian Ottewill | Bruce Allen and Adrian C. Ottewill | Waveforms for Gravitational Radiation from Cosmic String Loops | 16 pages, 6 figures, Revtex | Phys.Rev. D63 (2001) 063507 | 10.1103/PhysRevD.63.063507 | null | gr-qc | null | We obtain general formulae for the plus- and cross- polarized waveforms of
gravitational radiation emitted by a cosmic string loop in transverse,
traceless (synchronous, harmonic) gauge. These equations are then specialized
to the case of piecewise linear loops, and it is shown that the general
waveform for such a loop is a piecewise linear function. We give several simple
examples of the waveforms from such loops. We also discuss the relation between
the gravitational radiation by a smooth loop and by a piecewise linear
approximation to it.
| [
{
"created": "Tue, 26 Sep 2000 16:34:14 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Allen",
"Bruce",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | We obtain general formulae for the plus- and cross- polarized waveforms of gravitational radiation emitted by a cosmic string loop in transverse, traceless (synchronous, harmonic) gauge. These equations are then specialized to the case of piecewise linear loops, and it is shown that the general waveform for such a loop is a piecewise linear function. We give several simple examples of the waveforms from such loops. We also discuss the relation between the gravitational radiation by a smooth loop and by a piecewise linear approximation to it. |
gr-qc/0304065 | Mustapha Ishak | Mustapha Ishak (1), Kayll Lake (2) ((1) Princeton University, (2)
Queen's University, Kingston) | An inverse approach to Einstein's equations for non-conducting fluids | 9 pages revtex4. Final form to appear in Phys Rev D | Phys.Rev.D68:104031,2003 | 10.1103/PhysRevD.68.104031 | null | gr-qc astro-ph.CO | null | We show that a flow (timelike congruence) in any type $B_{1}$ warped product
spacetime is uniquely and algorithmically determined by the condition of zero
flux. (Though restricted, these spaces include many cases of interest.) The
flow is written out explicitly for canonical representations of the spacetimes.
With the flow determined, we explore an inverse approach to Einstein's
equations where a phenomenological fluid interpretation of a spacetime follows
directly from the metric irrespective of the choice of coordinates. This
approach is pursued for fluids with anisotropic pressure and shear viscosity.
In certain degenerate cases this interpretation is shown to be generically not
unique. The framework developed allows the study of exact solutions in any
frame without transformations. We provide a number of examples, in various
coordinates, including spacetimes with and without unique interpretations. The
results and algorithmic procedure developed are implemented as a computer
algebra program called GRSource.
| [
{
"created": "Thu, 17 Apr 2003 18:28:34 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jun 2003 22:05:26 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Oct 2003 19:52:23 GMT",
"version": "v3"
}
] | 2011-02-01 | [
[
"Ishak",
"Mustapha",
""
],
[
"Lake",
"Kayll",
""
]
] | We show that a flow (timelike congruence) in any type $B_{1}$ warped product spacetime is uniquely and algorithmically determined by the condition of zero flux. (Though restricted, these spaces include many cases of interest.) The flow is written out explicitly for canonical representations of the spacetimes. With the flow determined, we explore an inverse approach to Einstein's equations where a phenomenological fluid interpretation of a spacetime follows directly from the metric irrespective of the choice of coordinates. This approach is pursued for fluids with anisotropic pressure and shear viscosity. In certain degenerate cases this interpretation is shown to be generically not unique. The framework developed allows the study of exact solutions in any frame without transformations. We provide a number of examples, in various coordinates, including spacetimes with and without unique interpretations. The results and algorithmic procedure developed are implemented as a computer algebra program called GRSource. |
2401.03810 | Iarley P. Lobo Dr | Iarley P. Lobo | Time Delay in $\kappa$-Anti-de Sitter Spacetime | Title modified. Corrections on the translation parameters were made.
7 pages, 2 figures. Version published in PLB | Phys. Lett. B 855 (2024) 138864 | 10.1016/j.physletb.2024.138864 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Based on deformed translations in the $\kappa$-anti-de Sitter algebra, we
derive a delay in the time of detection between a soft and a hard photon, which
are simultaneously emitted at a distant event, to first order in the quantum
gravity parameter. In the basis analyzed, the trajectories are undeformed, and
the effect depends exclusively on the symmetry properties of the quantum
algebra. The time delay depends linearly on the energy of the hard particle and
has a sinusoidal dependence on the redshift of the source.
| [
{
"created": "Mon, 8 Jan 2024 10:59:06 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2024 10:22:21 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Jul 2024 12:17:51 GMT",
"version": "v3"
}
] | 2024-07-19 | [
[
"Lobo",
"Iarley P.",
""
]
] | Based on deformed translations in the $\kappa$-anti-de Sitter algebra, we derive a delay in the time of detection between a soft and a hard photon, which are simultaneously emitted at a distant event, to first order in the quantum gravity parameter. In the basis analyzed, the trajectories are undeformed, and the effect depends exclusively on the symmetry properties of the quantum algebra. The time delay depends linearly on the energy of the hard particle and has a sinusoidal dependence on the redshift of the source. |
0905.0543 | Guido Cognola | Guido Cognola, Emilio Elizalde, Shin'ichi Nojiri, Sergei D. Odintsov,
Sergio Zerbini | One-loop effective action for non-local modified Gauss-Bonnet gravity in
de Sitter space | latex file, 17 pages, 4 figures. Published version. Significative
improvement and new references | Eur.Phys.J.C64:483-494,2009 | 10.1140/epjc/s10052-009-1154-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the classical and quantum properties of non-local modified
Gauss-Bonnet gravity in de Sitter space, using its equivalent representation
via string-inspired local scalar-Gauss-Bonnet gravity with a scalar potential.
A classical, multiply de Sitter universe solution is found where one of the de
Sitter phases corresponds to the primordial inflationary epoch, while the other
de Sitter space solution--the one with the smallest Hubble rate--describes the
late-time acceleration of our universe. A Chameleon scenario for the theory
under investigation is developed, and it is successfully used to show that the
theory complies with gravitational tests. An explicit expression for the
one-loop effective action for this non-local modified Gauss-Bonnet gravity in
the de Sitter space is obtained. It is argued that this effective action might
be an important step towards the solution of the cosmological constant problem.
| [
{
"created": "Tue, 5 May 2009 08:07:16 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Sep 2009 06:50:09 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Cognola",
"Guido",
""
],
[
"Elizalde",
"Emilio",
""
],
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Zerbini",
"Sergio",
""
]
] | We discuss the classical and quantum properties of non-local modified Gauss-Bonnet gravity in de Sitter space, using its equivalent representation via string-inspired local scalar-Gauss-Bonnet gravity with a scalar potential. A classical, multiply de Sitter universe solution is found where one of the de Sitter phases corresponds to the primordial inflationary epoch, while the other de Sitter space solution--the one with the smallest Hubble rate--describes the late-time acceleration of our universe. A Chameleon scenario for the theory under investigation is developed, and it is successfully used to show that the theory complies with gravitational tests. An explicit expression for the one-loop effective action for this non-local modified Gauss-Bonnet gravity in the de Sitter space is obtained. It is argued that this effective action might be an important step towards the solution of the cosmological constant problem. |
0806.2418 | Mohammad Reza Setare | P. Moyassari, and M. R. Setare | Quintom dark energy in DGP braneworld cosmology | 12 pages, 8 figures | Phys.Lett.B674:237-242,2009 | 10.1016/j.physletb.2009.03.051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider a $Z_2$ symmetrical 3-brane embedded in a
5-dimensional spacetime. We study the effective Einstein equation and
acceleration condition in presence of the quintom dark energy fluid as the bulk
matter field. It is shown that the time-dependent bulk quintom field induces a
time-dependent cosmological constant on the brane. In the framework of the DGP
model, the effective Einstein equation is obtained in two different cases: i)
where the quintom field is considered as the bulk matter field and the brane is
empty and, ii) where the quintom dark energy is confined on the brane and the
bulk is empty. We show that in both cases one could obtain a self-inflationary
solution at late time in positive branch $\epsilon=1$, and an asymptotically
static universe in negative branch $\epsilon=-1$.
| [
{
"created": "Sun, 15 Jun 2008 05:15:36 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Apr 2009 10:30:26 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Moyassari",
"P.",
""
],
[
"Setare",
"M. R.",
""
]
] | In this paper we consider a $Z_2$ symmetrical 3-brane embedded in a 5-dimensional spacetime. We study the effective Einstein equation and acceleration condition in presence of the quintom dark energy fluid as the bulk matter field. It is shown that the time-dependent bulk quintom field induces a time-dependent cosmological constant on the brane. In the framework of the DGP model, the effective Einstein equation is obtained in two different cases: i) where the quintom field is considered as the bulk matter field and the brane is empty and, ii) where the quintom dark energy is confined on the brane and the bulk is empty. We show that in both cases one could obtain a self-inflationary solution at late time in positive branch $\epsilon=1$, and an asymptotically static universe in negative branch $\epsilon=-1$. |
1906.10662 | Jean Alexandre | Jean Alexandre and Katy Clough | Saving the universe with finite volume effects | 8 pages, 2 figures, comments and references added | Phys. Rev. D 100, 103522 (2019) | 10.1103/PhysRevD.100.103522 | KCL-PH-TH/2019-70 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Setting aside anthropic arguments, there is no reason why the universe should
initially favour a net expanding phase rather than one experiencing a net
contraction. However, a collapsing universe containing "normal" matter will end
at a singularity in a finite time. We point out that there is a mechanism,
derived from non-perturbative effects in Quantum Field Theory in a finite
volume, which may provide a bias towards expansion when the spacetime volume
shrinks, by dynamically violating the null energy condition, without the need
for modified gravity or exotic matter. We describe a scalar field component
subjected to this non-perturbative effect in a cosmological background and
consider its impact on a contracting phase. We discuss how this could
dynamically generate the necessary initial conditions for inflation to get
started, or form part of the mechanism for a non-singular cosmological bounce.
| [
{
"created": "Tue, 25 Jun 2019 16:56:15 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Oct 2019 17:05:02 GMT",
"version": "v2"
}
] | 2019-11-20 | [
[
"Alexandre",
"Jean",
""
],
[
"Clough",
"Katy",
""
]
] | Setting aside anthropic arguments, there is no reason why the universe should initially favour a net expanding phase rather than one experiencing a net contraction. However, a collapsing universe containing "normal" matter will end at a singularity in a finite time. We point out that there is a mechanism, derived from non-perturbative effects in Quantum Field Theory in a finite volume, which may provide a bias towards expansion when the spacetime volume shrinks, by dynamically violating the null energy condition, without the need for modified gravity or exotic matter. We describe a scalar field component subjected to this non-perturbative effect in a cosmological background and consider its impact on a contracting phase. We discuss how this could dynamically generate the necessary initial conditions for inflation to get started, or form part of the mechanism for a non-singular cosmological bounce. |
2108.04154 | Bradley James Kavanagh | Adam Coogan, Gianfranco Bertone, Daniele Gaggero, Bradley J. Kavanagh,
David A. Nichols | Measuring the dark matter environments of black hole binaries with
gravitational waves | 16 pages + 3 appendices, 8 figures. Code available online at
https://github.com/adam-coogan/pydd . v2: Matches version published in PRD | Phys. Rev. D 105, 043009 (2022) | 10.1103/PhysRevD.105.043009 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Large dark matter overdensities can form around black holes of astrophysical
and primordial origin as they form and grow. This "dark dress" inevitably
affects the dynamical evolution of binary systems, and induces a dephasing in
the gravitational waveform that can be probed with future interferometers. In
this paper, we introduce a new analytical model to rapidly compute
gravitational waveforms in presence of an evolving dark matter distribution. We
then present a Bayesian analysis determining when dressed black hole binaries
can be distinguished from GR-in-vacuum ones and how well their parameters can
be measured, along with how close they must be to be detectable by the planned
Laser Interferometer Space Antenna (LISA). We show that LISA can definitively
distinguish dark dresses from standard binaries and characterize the dark
matter environments around astrophysical and primordial black holes for a wide
range of model parameters. Our approach can be generalized to assess the
prospects for detecting, classifying, and characterizing other environmental
effects in gravitational wave physics.
| [
{
"created": "Mon, 9 Aug 2021 16:25:55 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Apr 2022 11:04:38 GMT",
"version": "v2"
}
] | 2022-04-04 | [
[
"Coogan",
"Adam",
""
],
[
"Bertone",
"Gianfranco",
""
],
[
"Gaggero",
"Daniele",
""
],
[
"Kavanagh",
"Bradley J.",
""
],
[
"Nichols",
"David A.",
""
]
] | Large dark matter overdensities can form around black holes of astrophysical and primordial origin as they form and grow. This "dark dress" inevitably affects the dynamical evolution of binary systems, and induces a dephasing in the gravitational waveform that can be probed with future interferometers. In this paper, we introduce a new analytical model to rapidly compute gravitational waveforms in presence of an evolving dark matter distribution. We then present a Bayesian analysis determining when dressed black hole binaries can be distinguished from GR-in-vacuum ones and how well their parameters can be measured, along with how close they must be to be detectable by the planned Laser Interferometer Space Antenna (LISA). We show that LISA can definitively distinguish dark dresses from standard binaries and characterize the dark matter environments around astrophysical and primordial black holes for a wide range of model parameters. Our approach can be generalized to assess the prospects for detecting, classifying, and characterizing other environmental effects in gravitational wave physics. |
1011.2536 | Volker Perlick | Volker Perlick | On the hyperbolicity of Maxwell's equations with a local constitutive
law | 21 pages, no figures. Revised version contains 3 more references and
several minor corrections. To appear in J. Math. Phys | J. Math. Phys. 52, 042903 (2011) | 10.1063/1.3579133 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Maxwell's equations are considered in metric-free form, with a local but
otherwise arbitrary constitutive law. After splitting Maxwell's equations into
evolution equations and constraints, we derive the characteristic equation and
we discuss its properties in detail. We present several results that are
relevant for the question of whether the evolution equations are hyperbolic,
strongly hyperbolic or symmmetric hyperbolic. In particular, we give a
convenient characterisation of all constitutive laws for which the evolution
equations are symmetric hyperbolic. The latter property is sufficient, but not
necessary, for well-posedness of the initial-value problem. By way of example,
we illustrate our results with the constitutive laws of biisotropic media and
of Born-Infeld theory.
| [
{
"created": "Thu, 11 Nov 2010 00:04:40 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Apr 2011 12:47:59 GMT",
"version": "v2"
}
] | 2015-08-11 | [
[
"Perlick",
"Volker",
""
]
] | Maxwell's equations are considered in metric-free form, with a local but otherwise arbitrary constitutive law. After splitting Maxwell's equations into evolution equations and constraints, we derive the characteristic equation and we discuss its properties in detail. We present several results that are relevant for the question of whether the evolution equations are hyperbolic, strongly hyperbolic or symmmetric hyperbolic. In particular, we give a convenient characterisation of all constitutive laws for which the evolution equations are symmetric hyperbolic. The latter property is sufficient, but not necessary, for well-posedness of the initial-value problem. By way of example, we illustrate our results with the constitutive laws of biisotropic media and of Born-Infeld theory. |
1511.02220 | Carlos Hidalgo | Adam J. Christopherson, Juan Carlos Hidalgo, Cornelius Rampf, Karim A.
Malik | Second-order cosmological perturbation theory and initial conditions for
$N$-body simulations | V2: Second order density added and other expressions simplified.
References updated. 15 pages | Phys. Rev. D 93, 043539 (2016) | 10.1103/PhysRevD.93.043539 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use gauge-invariant cosmological perturbation theory to calculate the
displacement field that sets the initial conditions for $N$-body simulations.
Using first and second-order fully relativistic perturbation theory in the
synchronous-comoving gauge, allows us to go beyond the Newtonian predictions
and to calculate relativistic corrections to it. We use an Einstein--de Sitter
model, including both growing and decaying modes in our solutions. The impact
of our results should be assessed through the implementation of the featured
displacement in cosmological $N$-body simulations.
| [
{
"created": "Fri, 6 Nov 2015 20:27:46 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Dec 2015 02:59:30 GMT",
"version": "v2"
}
] | 2016-03-02 | [
[
"Christopherson",
"Adam J.",
""
],
[
"Hidalgo",
"Juan Carlos",
""
],
[
"Rampf",
"Cornelius",
""
],
[
"Malik",
"Karim A.",
""
]
] | We use gauge-invariant cosmological perturbation theory to calculate the displacement field that sets the initial conditions for $N$-body simulations. Using first and second-order fully relativistic perturbation theory in the synchronous-comoving gauge, allows us to go beyond the Newtonian predictions and to calculate relativistic corrections to it. We use an Einstein--de Sitter model, including both growing and decaying modes in our solutions. The impact of our results should be assessed through the implementation of the featured displacement in cosmological $N$-body simulations. |
1509.04971 | Dominic Dold | Dominic Dold | Unstable mode solutions to the Klein-Gordon equation in Kerr-anti-de
Sitter spacetimes | 56 pages, 2 figures, final version with minor changes, to appear in
Comm. Math. Phys | null | 10.1007/s00220-016-2783-8 | null | gr-qc hep-th math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For any cosmological constant $\Lambda=-3/\ell^2<0$ and any $\alpha<9/4$, we
find a Kerr-AdS spacetime $(\mathcal M,g_{\mathrm{KAdS}})$, in which the
Klein-Gordon equation $\Box_{g_{\mathrm{KAdS}}}\psi+\alpha/\ell^2\psi=0$ has an
exponentially growing mode solution satisfying a Dirichlet boundary condition
at infinity. The spacetime violates the Hawking-Reall bound $r_+^2>|a|\ell$. We
obtain an analogous result for Neumann boundary conditions if $5/4<\alpha<9/4$.
Moreover, in the Dirichlet case, one can prove that, for any Kerr-AdS spacetime
violating the Hawking-Reall bound, there exists an open family of masses
$\alpha$ such that the corresponding Klein-Gordon equation permits
exponentially growing mode solutions. Our result adopts methods of
Shlapentokh-Rothman (see arXiv:1302.3448) and provides the first rigorous
construction of a superradiant instability for negative cosmological constant.
| [
{
"created": "Wed, 16 Sep 2015 16:31:30 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Aug 2016 13:13:42 GMT",
"version": "v2"
}
] | 2016-11-23 | [
[
"Dold",
"Dominic",
""
]
] | For any cosmological constant $\Lambda=-3/\ell^2<0$ and any $\alpha<9/4$, we find a Kerr-AdS spacetime $(\mathcal M,g_{\mathrm{KAdS}})$, in which the Klein-Gordon equation $\Box_{g_{\mathrm{KAdS}}}\psi+\alpha/\ell^2\psi=0$ has an exponentially growing mode solution satisfying a Dirichlet boundary condition at infinity. The spacetime violates the Hawking-Reall bound $r_+^2>|a|\ell$. We obtain an analogous result for Neumann boundary conditions if $5/4<\alpha<9/4$. Moreover, in the Dirichlet case, one can prove that, for any Kerr-AdS spacetime violating the Hawking-Reall bound, there exists an open family of masses $\alpha$ such that the corresponding Klein-Gordon equation permits exponentially growing mode solutions. Our result adopts methods of Shlapentokh-Rothman (see arXiv:1302.3448) and provides the first rigorous construction of a superradiant instability for negative cosmological constant. |
1301.1109 | Hiromi Saida | Hiromi Saida | Universal Property of Quantum Gravity implied by Bekenstein-Hawking
Entropy and Boltzmann formula | This article is bease on ref.[4] (Entropy 13(2011)1611-1647), but the
conclusion in sec.4 is modified from ref.[4]. This is a refereed proceeding
article of International Conference on Mathematical Modeling in Physical
Sciences (IC-Msquare 2012) | null | 10.1088/1742-6596/410/1/012139 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We search for a universal property of quantum gravity. By "universal", we
mean the independence from any existing model of quantum gravity (such as the
super string theory, loop quantum gravity, causal dynamical triangulation, and
so on). To do so, we try to put the basis of our discussion on theories
established by some experiments. Thus, we focus our attention on
thermodynamical and statistical-mechanical basis of the black hole
thermodynamics: Let us assume that the Bekenstein-Hawking entropy is given by
the Boltzmann formula applied to the underlying theory of quantum gravity.
Under this assumption, the conditions justifying Boltzmann formula together
with uniqueness of Bekenstein-Hawking entropy imply a reasonable universal
property of quantum gravity. The universal property indicates a repulsive
gravity at Planck length scale, otherwise stationary black holes can not be
regarded as thermal equilibrium states of gravity. Further, in semi-classical
level, we discuss a possible correction of Einstein equation which generates
repulsive gravity at Planck length scale. (This article is bease on ref.[4]
(Entropy 13(2011)1611-1647), but the conclusion in sec.4 is modified from
ref.[4].)
| [
{
"created": "Mon, 7 Jan 2013 04:37:24 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Saida",
"Hiromi",
""
]
] | We search for a universal property of quantum gravity. By "universal", we mean the independence from any existing model of quantum gravity (such as the super string theory, loop quantum gravity, causal dynamical triangulation, and so on). To do so, we try to put the basis of our discussion on theories established by some experiments. Thus, we focus our attention on thermodynamical and statistical-mechanical basis of the black hole thermodynamics: Let us assume that the Bekenstein-Hawking entropy is given by the Boltzmann formula applied to the underlying theory of quantum gravity. Under this assumption, the conditions justifying Boltzmann formula together with uniqueness of Bekenstein-Hawking entropy imply a reasonable universal property of quantum gravity. The universal property indicates a repulsive gravity at Planck length scale, otherwise stationary black holes can not be regarded as thermal equilibrium states of gravity. Further, in semi-classical level, we discuss a possible correction of Einstein equation which generates repulsive gravity at Planck length scale. (This article is bease on ref.[4] (Entropy 13(2011)1611-1647), but the conclusion in sec.4 is modified from ref.[4].) |
1405.7904 | Evan Goetz | The LIGO Scientific Collaboration and the Virgo Collaboration: J.
Aasi, B. P. Abbott, R. Abbott, T. Abbott, M. R. Abernathy, T. Accadia, F.
Acernese, K. Ackley, C. Adams, T. Adams, P. Addesso, R. X. Adhikari, C.
Affeldt, M. Agathos, N. Aggarwal, O. D. Aguiar, A. Ain, P. Ajith, A. Alemic,
B. Allen, A. Allocca, D. Amariutei, M. Andersen, R. Anderson, S. B. Anderson,
W. G. Anderson, K. Arai, M. C. Araya, C. Arceneaux, J. Areeda, S. M. Aston,
P. Astone, P. Aufmuth, C. Aulbert, L. Austin, B. E. Aylott, S. Babak, P. T.
Baker, G. Ballardin, S. W. Ballmer, J. C. Barayoga, M. Barbet, B. C. Barish,
D. Barker, F. Barone, B. Barr, L. Barsotti, M. Barsuglia, M. A. Barton, I.
Bartos, R. Bassiri, A. Basti, J. C. Batch, J. Bauchrowitz, Th. S. Bauer, B.
Behnke, M. Bejger, M. G. Beker, C. Belczynski, A. S. Bell, C. Bell, G.
Bergmann, D. Bersanetti, A. Bertolini, J. Betzwieser, P. T. Beyersdorf, I. A.
Bilenko, G. Billingsley, J. Birch, S. Biscans, M. Bitossi, M. A. Bizouard, E.
Black, J. K. Blackburn, L. Blackburn, D. Blair, S. Bloemen, M. Blom, O. Bock,
T. P. Bodiya, M. Boer, G. Bogaert, C. Bogan, C. Bond, F. Bondu, L. Bonelli,
R. Bonnand, R. Bork, M. Born, V. Boschi, Sukanta Bose, L. Bosi, C.
Bradaschia, P. R. Brady, V. B. Braginsky, M. Branchesi, J. E. Brau, T.
Briant, D. O. Bridges, A. Brillet, M. Brinkmann, V. Brisson, A. F. Brooks, D.
A. Brown, D. D. Brown, F. Br\"uckner, S. Buchman, T. Bulik, H. J. Bulten, A.
Buonanno, R. Burman, D. Buskulic, C. Buy, L. Cadonati, G. Cagnoli, J.
Calder\'on Bustillo, E. Calloni, J. B. Camp, P. Campsie, K. C. Cannon, B.
Canuel, J. Cao, C. D. Capano, F. Carbognani, L. Carbone, S. Caride, A.
Castiglia, S. Caudill, M. Cavagli\`a, F. Cavalier, R. Cavalieri, C. Celerier,
G. Cella, C. Cepeda, E. Cesarini, R. Chakraborty, T. Chalermsongsak, S. J.
Chamberlin, S. Chao, P. Charlton, E. Chassande-Mottin, X. Chen, Y. Chen, A.
Chincarini, A. Chiummo, H. S. Cho, J. Chow, N. Christensen, Q. Chu, S. S. Y.
Chua, S. Chung, G. Ciani, F. Clara, J. A. Clark, F. Cleva, E. Coccia, P.-F.
Cohadon, A. Colla, C. Collette, M. Colombini, L. Cominsky, M. Constancio Jr.,
A. Conte, D. Cook, T. R. Corbitt, M. Cordier, N. Cornish, A. Corpuz, A.
Corsi, C. A. Costa, M. W. Coughlin, S. Coughlin, J.-P. Coulon, S. Countryman,
P. Couvares, D. M. Coward, M. Cowart, D. C. Coyne, R. Coyne, K. Craig, J. D.
E. Creighton, T. D. Creighton, S. G. Crowder, A. Cumming, L. Cunningham, E.
Cuoco, K. Dahl, T. Dal Canton, M. Damjanic, S. L. Danilishin, S. D'Antonio,
K. Danzmann, V. Dattilo, H. Daveloza, M. Davier, G. S. Davies, E. J. Daw, R.
Day, T. Dayanga, G. Debreczeni, J. Degallaix, S. Del\'eglise, W. Del Pozzo,
T. Denker, T. Dent, H. Dereli, V. Dergachev, R. De Rosa, R. T. DeRosa, R.
DeSalvo, S. Dhurandhar, M. D\'iaz, L. Di Fiore, A. Di Lieto, I. Di Palma, A.
Di Virgilio, A. Donath, F. Donovan, K. L. Dooley, S. Doravari, S. Dossa, R.
Douglas, T. P. Downes, M. Drago, R. W. P. Drever, J. C. Driggers, Z. Du, S.
Dwyer, T. Eberle, T. Edo, M. Edwards, A. Effler, H. Eggenstein, P. Ehrens, J.
Eichholz, S. S. Eikenberry, G. Endr\H{o}czi, R. Essick, T. Etzel, M. Evans,
T. Evans, M. Factourovich, V. Fafone, S. Fairhurst, Q. Fang, S. Farinon, B.
Farr, W. M. Farr, M. Favata, H. Fehrmann, M. M. Fejer, D. Feldbaum, F. Feroz,
I. Ferrante, F. Ferrini, F. Fidecaro, L. S. Finn, I. Fiori, R. P. Fisher, R.
Flaminio, J.-D. Fournier, S. Franco, S. Frasca, F. Frasconi, M. Frede, Z.
Frei, A. Freise, R. Frey, T. T. Fricke, P. Fritschel, V. V. Frolov, P. Fulda,
M. Fyffe, J. Gair, L. Gammaitoni, S. Gaonkar, F. Garufi, N. Gehrels, G.
Gemme, E. Genin, A. Gennai, S. Ghosh, J. A. Giaime, K. D. Giardina, A.
Giazotto, C. Gill, J. Gleason, E. Goetz, R. Goetz, L. Gondan, G. Gonz\'alez,
N. Gordon, M. L. Gorodetsky, S. Gossan, S. Go{\ss}ler, R. Gouaty, C. Gr\"af,
P. B. Graff, M. Granata, A. Grant, S. Gras, C. Gray, R. J. S. Greenhalgh, A.
M. Gretarsson, P. Groot, H. Grote, K. Grover, S. Grunewald, G. M. Guidi, C.
Guido, K. Gushwa, E. K. Gustafson, R. Gustafson, D. Hammer, G. Hammond, M.
Hanke, J. Hanks, C. Hanna, J. Hanson, J. Harms, G. M. Harry, I. W. Harry, E.
D. Harstad, M. Hart, M. T. Hartman, C.-J. Haster, K. Haughian, A. Heidmann,
M. Heintze, H. Heitmann, P. Hello, G. Hemming, M. Hendry, I. S. Heng, A. W.
Heptonstall, M. Heurs, M. Hewitson, S. Hild, D. Hoak, K. A. Hodge, K. Holt,
S. Hooper, P. Hopkins, D. J. Hosken, J. Hough, E. J. Howell, Y. Hu, E.
Huerta, B. Hughey, S. Husa, S. H. Huttner, M. Huynh, T. Huynh-Dinh, D. R.
Ingram, R. Inta, T. Isogai, A. Ivanov, B. R. Iyer, K. Izumi, M. Jacobson, E.
James, H. Jang, P. Jaranowski, Y. Ji, F. Jim\'enez-Forteza, W. W. Johnson, D.
I. Jones, R. Jones, R.J.G. Jonker, L. Ju, Haris K, P. Kalmus, V. Kalogera, S.
Kandhasamy, G. Kang, J. B. Kanner, J. Karlen, M. Kasprzack, E. Katsavounidis,
W. Katzman, H. Kaufer, K. Kawabe, F. Kawazoe, F. K\'ef\'elian, G. M. Keiser,
D. Keitel, D. B. Kelley, W. Kells, A. Khalaidovski, F. Y. Khalili, E. A.
Khazanov, C. Kim, K. Kim, N. Kim, N. G. Kim, Y.-M. Kim, E. J. King, P. J.
King, D. L. Kinzel, J. S. Kissel, S. Klimenko, J. Kline, S. Koehlenbeck, K.
Kokeyama, V. Kondrashov, S. Koranda, W. Z. Korth, I. Kowalska, D. B. Kozak,
A. Kremin, V. Kringel, B. Krishnan, A. Kr\'olak, G. Kuehn, A. Kumar, P.
Kumar, R. Kumar, L. Kuo, A. Kutynia, P. Kwee, M. Landry, B. Lantz, S. Larson,
P. D. Lasky, C. Lawrie, A. Lazzarini, C. Lazzaro, P. Leaci, S. Leavey, E. O.
Lebigot, C.-H. Lee, H. K. Lee, H. M. Lee, J. Lee, M. Leonardi, J. R. Leong,
A. Le Roux, N. Leroy, N. Letendre, Y. Levin, B. Levine, J. Lewis, T. G. F.
Li, K. Libbrecht, A. Libson, A. C. Lin, T. B. Littenberg, V. Litvine, N. A.
Lockerbie, V. Lockett, D. Lodhia, K. Loew, J. Logue, A. L. Lombardi, M.
Lorenzini, V. Loriette, M. Lormand, G. Losurdo, J. Lough, M. J. Lubinski, H.
L\"uck, E. Luijten, A. P. Lundgren, R. Lynch, Y. Ma, J. Macarthur, E. P.
Macdonald, T. MacDonald, B. Machenschalk, M. MacInnis, D. M. Macleod, F.
Magana-Sandoval, M. Mageswaran, C. Maglione, K. Mailand, E. Majorana, I.
Maksimovic, V. Malvezzi, N. Man, G. M. Manca, I. Mandel, V. Mandic, V.
Mangano, N. Mangini, M. Mantovani, F. Marchesoni, F. Marion, S. M\'arka, Z.
M\'arka, A. Markosyan, E. Maros, J. Marque, F. Martelli, I. W. Martin, R. M.
Martin, L. Martinelli, D. Martynov, J. N. Marx, K. Mason, A. Masserot, T. J.
Massinger, F. Matichard, L. Matone, R. A. Matzner, N. Mavalvala, N. Mazumder,
G. Mazzolo, R. McCarthy, D. E. McClelland, S. C. McGuire, G. McIntyre, J.
McIver, K. McLin, D. Meacher, G. D. Meadors, M. Mehmet, J. Meidam, M.
Meinders, A. Melatos, G. Mendell, R. A. Mercer, S. Meshkov, C. Messenger, P.
Meyers, H. Miao, C. Michel, E. E. Mikhailov, L. Milano, S. Milde, J. Miller,
Y. Minenkov, C. M. F. Mingarelli, C. Mishra, S. Mitra, V. P. Mitrofanov, G.
Mitselmakher, R. Mittleman, B. Moe, P. Moesta, M. Mohan, S. R. P. Mohapatra,
D. Moraru, G. Moreno, N. Morgado, S. R. Morriss, K. Mossavi, B. Mours, C. M.
Mow-Lowry, C. L. Mueller, G. Mueller, S. Mukherjee, A. Mullavey, J. Munch, D.
Murphy, P. G. Murray, A. Mytidis, M. F. Nagy, D. Nanda Kumar, I. Nardecchia,
L. Naticchioni, R. K. Nayak, V. Necula, G. Nelemans, I. Neri, M. Neri, G.
Newton, T. Nguyen, A. Nitz, F. Nocera, D. Nolting, M. E. N. Normandin, L. K.
Nuttall, E. Ochsner, J. O'Dell, E. Oelker, J. J. Oh, S. H. Oh, F. Ohme, P.
Oppermann, B. O'Reilly, R. O'Shaughnessy, C. Osthelder, D. J. Ottaway, R. S.
Ottens, H. Overmier, B. J. Owen, C. Padilla, A. Pai, O. Palashov, C. Palomba,
H. Pan, Y. Pan, C. Pankow, F. Paoletti, R. Paoletti, M. A. Papa, H. Paris, A.
Pasqualetti, R. Passaquieti, D. Passuello, M. Pedraza, S. Penn, A. Perreca,
M. Phelps, M. Pichot, M. Pickenpack, F. Piergiovanni, V. Pierro, L. Pinard,
I. M. Pinto, M. Pitkin, J. Poeld, R. Poggiani, A. Poteomkin, J. Powell, J.
Prasad, S. Premachandra, T. Prestegard, L. R. Price, M. Prijatelj, S.
Privitera, R. Prix, G. A. Prodi, L. Prokhorov, O. Puncken, M. Punturo, P.
Puppo, J. Qin, V. Quetschke, E. Quintero, G. Quiroga, R. Quitzow-James, F. J.
Raab, D. S. Rabeling, I. R\'acz, H. Radkins, P. Raffai, S. Raja, G.
Rajalakshmi, M. Rakhmanov, C. Ramet, K. Ramirez, P. Rapagnani, V. Raymond, V.
Re, J. Read, C. M. Reed, T. Regimbau, S. Reid, D. H. Reitze, E. Rhoades, F.
Ricci, K. Riles, N. A. Robertson, F. Robinet, A. Rocchi, M. Rodruck, L.
Rolland, J. G. Rollins, R. Romano, G. Romanov, J. H. Romie, D. Rosi\'nska, S.
Rowan, A. R\"udiger, P. Ruggi, K. Ryan, F. Salemi, L. Sammut, V. Sandberg, J.
R. Sanders, V. Sannibale, I. Santiago-Prieto, E. Saracco, B. Sassolas, B. S.
Sathyaprakash, P. R. Saulson, R. Savage, J. Scheuer, R. Schilling, R.
Schnabel, R. M. S. Schofield, E. Schreiber, D. Schuette, B. F. Schutz, J.
Scott, S. M. Scott, D. Sellers, A. S. Sengupta, D. Sentenac, V. Sequino, A.
Sergeev, D. Shaddock, S. Shah, M. S. Shahriar, M. Shaltev, B. Shapiro, P.
Shawhan, D. H. Shoemaker, T. L. Sidery, K. Siellez, X. Siemens, D. Sigg, D.
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Stuver, T. Z. Summerscales, S. Susmithan, P. J. Sutton, B. Swinkels, M.
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P. J. Veitch, K. Venkateswara, D. Verkindt, S. S. Verma, F. Vetrano, A.
Vicer\'e, R. Vincent-Finley, J.-Y. Vinet, S. Vitale, T. Vo, H. Vocca, C.
Vorvick, W. D. Vousden, S. P. Vyachanin, A. Wade, L. Wade, M. Wade, M.
Walker, L. Wallace, M. Wang, X. Wang, R. L. Ward, M. Was, B. Weaver, L.-W.
Wei, M. Weinert, A. J. Weinstein, R. Weiss, T. Welborn, L. Wen, P. Wessels,
M. West, T. Westphal, K. Wette, J. T. Whelan, D. J. White, B. F. Whiting, K.
Wiesner, C. Wilkinson, K. Williams, L. Williams, R. Williams, T. Williams, A.
R. Williamson, J. L. Willis, B. Willke, M. Wimmer, W. Winkler, C. C. Wipf, A.
G. Wiseman, H. Wittel, G. Woan, J. Worden, J. Yablon, I. Yakushin, H.
Yamamoto, C. C. Yancey, H. Yang, Z. Yang, S. Yoshida, M. Yvert, A.
Zadro\.zny, M. Zanolin, J.-P. Zendri, Fan Zhang, L. Zhang, C. Zhao, X. J.
Zhu, M. E. Zucker, S. Zuraw, J. Zweizig | First all-sky search for continuous gravitational waves from unknown
sources in binary systems | 16 pages, 6 figures | Phys. Rev. D 90, 062010 (2014) | 10.1103/PhysRevD.90.062010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first results of an all-sky search for continuous
gravitational waves from unknown spinning neutron stars in binary systems using
LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect
algorithm, the search was carried out on data from the sixth LIGO Science Run
and the second and third Virgo Science Runs. The search covers a range of
frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ~2,254 h
and a frequency- and period-dependent range of frequency modulation depths from
0.277 to 100 mHz. This corresponds to a range of projected semi-major axes of
the orbit from ~0.6e-3 ls to ~6,500 ls assuming the orbit of the binary is
circular. While no plausible candidate gravitational wave events survive the
pipeline, upper limits are set on the analyzed data. The most sensitive 95%
confidence upper limit obtained on gravitational wave strain is 2.3e-24 at 217
Hz, assuming the source waves are circularly polarized. Although this search
has been optimized for circular binary orbits, the upper limits obtained remain
valid for orbital eccentricities as large as 0.9. In addition, upper limits are
placed on continuous gravitational wave emission from the low-mass x-ray binary
Scorpius X-1 between 20 Hz and 57.25 Hz.
| [
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"version": "v1"
},
{
"created": "Wed, 17 Sep 2014 09:02:57 GMT",
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""
],
[
"Siellez",
"K.",
""
],
[
"Siemens",
"X.",
""
],
[
"Sigg",
"D.",
""
],
[
"Simakov",
"D.",
""
],
[
"Singer",
"A.",
""
],
[
"Singer",
"L.",
""
],
[
"Singh",
"R.",
""
],
[
"Sintes",
"A. M.",
""
],
[
"Slagmolen",
"B. J. J.",
""
],
[
"Slutsky",
"J.",
""
],
[
"Smith",
"J. R.",
""
],
[
"Smith",
"M.",
""
],
[
"Smith",
"R. J. E.",
""
],
[
"Smith-Lefebvre",
"N. D.",
""
],
[
"Son",
"E. J.",
""
],
[
"Sorazu",
"B.",
""
],
[
"Souradeep",
"T.",
""
],
[
"Sperandio",
"L.",
""
],
[
"Staley",
"A.",
""
],
[
"Stebbins",
"J.",
""
],
[
"Steinlechner",
"J.",
""
],
[
"Steinlechner",
"S.",
""
],
[
"Stephens",
"B. C.",
""
],
[
"Steplewski",
"S.",
""
],
[
"Stevenson",
"S.",
""
],
[
"Stone",
"R.",
""
],
[
"Stops",
"D.",
""
],
[
"Strain",
"K. A.",
""
],
[
"Straniero",
"N.",
""
],
[
"Strigin",
"S.",
""
],
[
"Sturani",
"R.",
""
],
[
"Stuver",
"A. L.",
""
],
[
"Summerscales",
"T. Z.",
""
],
[
"Susmithan",
"S.",
""
],
[
"Sutton",
"P. J.",
""
],
[
"Swinkels",
"B.",
""
],
[
"Tacca",
"M.",
""
],
[
"Talukder",
"D.",
""
],
[
"Tanner",
"D. B.",
""
],
[
"Tarabrin",
"S. P.",
""
],
[
"Taylor",
"R.",
""
],
[
"ter Braack",
"A. P. M.",
""
],
[
"Thirugnanasambandam",
"M. P.",
""
],
[
"Thomas",
"M.",
""
],
[
"Thomas",
"P.",
""
],
[
"Thorne",
"K. A.",
""
],
[
"Thorne",
"K. S.",
""
],
[
"Thrane",
"E.",
""
],
[
"Tiwari",
"V.",
""
],
[
"Tokmakov",
"K. V.",
""
],
[
"Tomlinson",
"C.",
""
],
[
"Toncelli",
"A.",
""
],
[
"Tonelli",
"M.",
""
],
[
"Torre",
"O.",
""
],
[
"Torres",
"C. V.",
""
],
[
"Torrie",
"C. I.",
""
],
[
"Travasso",
"F.",
""
],
[
"Traylor",
"G.",
""
],
[
"Tse",
"M.",
""
],
[
"Ugolini",
"D.",
""
],
[
"Unnikrishnan",
"C. S.",
""
],
[
"Urban",
"A. L.",
""
],
[
"Urbanek",
"K.",
""
],
[
"Vahlbruch",
"H.",
""
],
[
"Vajente",
"G.",
""
],
[
"Valdes",
"G.",
""
],
[
"Vallisneri",
"M.",
""
],
[
"Brand",
"J. F. J. van den",
""
],
[
"Broeck",
"C. Van Den",
""
],
[
"van der Putten",
"S.",
""
],
[
"van der Sluys",
"M. V.",
""
],
[
"van Heijningen",
"J.",
""
],
[
"van Veggel",
"A. A.",
""
],
[
"Vass",
"S.",
""
],
[
"Vasúth",
"M.",
""
],
[
"Vaulin",
"R.",
""
],
[
"Vecchio",
"A.",
""
],
[
"Vedovato",
"G.",
""
],
[
"Veitch",
"J.",
""
],
[
"Veitch",
"P. J.",
""
],
[
"Venkateswara",
"K.",
""
],
[
"Verkindt",
"D.",
""
],
[
"Verma",
"S. S.",
""
],
[
"Vetrano",
"F.",
""
],
[
"Viceré",
"A.",
""
],
[
"Vincent-Finley",
"R.",
""
],
[
"Vinet",
"J. -Y.",
""
],
[
"Vitale",
"S.",
""
],
[
"Vo",
"T.",
""
],
[
"Vocca",
"H.",
""
],
[
"Vorvick",
"C.",
""
],
[
"Vousden",
"W. D.",
""
],
[
"Vyachanin",
"S. P.",
""
],
[
"Wade",
"A.",
""
],
[
"Wade",
"L.",
""
],
[
"Wade",
"M.",
""
],
[
"Walker",
"M.",
""
],
[
"Wallace",
"L.",
""
],
[
"Wang",
"M.",
""
],
[
"Wang",
"X.",
""
],
[
"Ward",
"R. L.",
""
],
[
"Was",
"M.",
""
],
[
"Weaver",
"B.",
""
],
[
"Wei",
"L. -W.",
""
],
[
"Weinert",
"M.",
""
],
[
"Weinstein",
"A. J.",
""
],
[
"Weiss",
"R.",
""
],
[
"Welborn",
"T.",
""
],
[
"Wen",
"L.",
""
],
[
"Wessels",
"P.",
""
],
[
"West",
"M.",
""
],
[
"Westphal",
"T.",
""
],
[
"Wette",
"K.",
""
],
[
"Whelan",
"J. T.",
""
],
[
"White",
"D. J.",
""
],
[
"Whiting",
"B. F.",
""
],
[
"Wiesner",
"K.",
""
],
[
"Wilkinson",
"C.",
""
],
[
"Williams",
"K.",
""
],
[
"Williams",
"L.",
""
],
[
"Williams",
"R.",
""
],
[
"Williams",
"T.",
""
],
[
"Williamson",
"A. R.",
""
],
[
"Willis",
"J. L.",
""
],
[
"Willke",
"B.",
""
],
[
"Wimmer",
"M.",
""
],
[
"Winkler",
"W.",
""
],
[
"Wipf",
"C. C.",
""
],
[
"Wiseman",
"A. G.",
""
],
[
"Wittel",
"H.",
""
],
[
"Woan",
"G.",
""
],
[
"Worden",
"J.",
""
],
[
"Yablon",
"J.",
""
],
[
"Yakushin",
"I.",
""
],
[
"Yamamoto",
"H.",
""
],
[
"Yancey",
"C. C.",
""
],
[
"Yang",
"H.",
""
],
[
"Yang",
"Z.",
""
],
[
"Yoshida",
"S.",
""
],
[
"Yvert",
"M.",
""
],
[
"Zadrożny",
"A.",
""
],
[
"Zanolin",
"M.",
""
],
[
"Zendri",
"J. -P.",
""
],
[
"Zhang",
"Fan",
""
],
[
"Zhang",
"L.",
""
],
[
"Zhao",
"C.",
""
],
[
"Zhu",
"X. J.",
""
],
[
"Zucker",
"M. E.",
""
],
[
"Zuraw",
"S.",
""
],
[
"Zweizig",
"J.",
""
]
] | We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO Science Run and the second and third Virgo Science Runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ~2,254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semi-major axes of the orbit from ~0.6e-3 ls to ~6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3e-24 at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz. |
gr-qc/9312024 | Michael P. Ryan | Michael P. Ryan Jr | Cosmological "Ground State" Wave Functions in Gravity and
Electromagnetism | 15 pages, Plain TEX | null | null | null | gr-qc | null | The coincidence of quantum cosmology solutions generated by solving a
Euclidean version of the Hamilton-Jacobi equation for gravity and by using the
complex canonical transformation of the Ashtekar variables is discussed. An
examination of similar solutions for the free electromagnetic field shows that
this coincidence is an artifact of the homogeneity of the cosmological space.
(This paper will appear in a festchrift volume for Jerzy Plebanski)
| [
{
"created": "Wed, 15 Dec 1993 17:58:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ryan",
"Michael P.",
"Jr"
]
] | The coincidence of quantum cosmology solutions generated by solving a Euclidean version of the Hamilton-Jacobi equation for gravity and by using the complex canonical transformation of the Ashtekar variables is discussed. An examination of similar solutions for the free electromagnetic field shows that this coincidence is an artifact of the homogeneity of the cosmological space. (This paper will appear in a festchrift volume for Jerzy Plebanski) |
1307.2213 | Sourav Bhattacharya | Sourav Bhattacharya | Note on black hole no hair theorems for massive forms and spin-1/2
fields | v2, 15pp; added references and discussions, typos corrected; slight
change in title to match published version | Phys. Rev. D 88, 044053 (2013) | 10.1103/PhysRevD.88.044053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a proof of the non-perturbative no hair theorems for a massive 2-form
field with 3-form field strength for general stationary axisymmetric and static
(anti)-de Sitter or asymptotically flat black hole spacetimes with some
suitable geometrical properties. The generalization of this result for higher
form fields is discussed. Next, we discuss the perturbative no hair theorems
for massive spin-1/2 fields for general static backgrounds with electric or
magnetic charge. Some generalization of this result for stationary axisymmetric
spacetimes are also discussed. All calculations are done in arbitrary spacetime
dimensions.
| [
{
"created": "Mon, 8 Jul 2013 19:41:02 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Aug 2013 05:02:51 GMT",
"version": "v2"
}
] | 2013-09-03 | [
[
"Bhattacharya",
"Sourav",
""
]
] | We give a proof of the non-perturbative no hair theorems for a massive 2-form field with 3-form field strength for general stationary axisymmetric and static (anti)-de Sitter or asymptotically flat black hole spacetimes with some suitable geometrical properties. The generalization of this result for higher form fields is discussed. Next, we discuss the perturbative no hair theorems for massive spin-1/2 fields for general static backgrounds with electric or magnetic charge. Some generalization of this result for stationary axisymmetric spacetimes are also discussed. All calculations are done in arbitrary spacetime dimensions. |
2204.07869 | Tupac Bravo Ibarra | Tupac Bravo, Dennis R\"atzel, Ivette Fuentes | Gravitational time dilation in extended quantum systems: the case of
light clocks in Schwarzschild spacetime | updated references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The precision of optical atomic clocks is approaching a regime where they
resolve gravitational time dilation on smaller scales than their own
extensions. Hence, an accurate description of quantum clocks has to take their
spatial extension into account. In this article, as a first step towards a
fully relativistic description of extended quantum clocks, we investigate a
quantized version of Einstein's light clock fixed at a constant distance from a
large massive object like the Earth. The model consists of a quantum light
field in a one-dimensional cavity in Schwarzschild spacetime, where the
distance between the mirrors is fixed by a rigid rod. By comparing a vertical
and a horizontal clock, we propose an operational way to define the clock time
when the clock resolves gravitational time dilation on scales smaller than its
extension. In particular, we show that the time measured by the vertical light
clock is equivalent to the proper time defined at its center. We also derive
fundamental bounds on the precision of these clocks for measurements of proper
time and the Schwarzschild radius.
| [
{
"created": "Sat, 16 Apr 2022 20:30:42 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Apr 2022 01:01:28 GMT",
"version": "v2"
},
{
"created": "Thu, 12 May 2022 02:06:18 GMT",
"version": "v3"
}
] | 2022-05-13 | [
[
"Bravo",
"Tupac",
""
],
[
"Rätzel",
"Dennis",
""
],
[
"Fuentes",
"Ivette",
""
]
] | The precision of optical atomic clocks is approaching a regime where they resolve gravitational time dilation on smaller scales than their own extensions. Hence, an accurate description of quantum clocks has to take their spatial extension into account. In this article, as a first step towards a fully relativistic description of extended quantum clocks, we investigate a quantized version of Einstein's light clock fixed at a constant distance from a large massive object like the Earth. The model consists of a quantum light field in a one-dimensional cavity in Schwarzschild spacetime, where the distance between the mirrors is fixed by a rigid rod. By comparing a vertical and a horizontal clock, we propose an operational way to define the clock time when the clock resolves gravitational time dilation on scales smaller than its extension. In particular, we show that the time measured by the vertical light clock is equivalent to the proper time defined at its center. We also derive fundamental bounds on the precision of these clocks for measurements of proper time and the Schwarzschild radius. |
1601.01260 | Pieter Miedema | P. G. Miedema | Structure Formation in the Early Universe | 21 pages, 2 figures. Thoroughly rewritten, references added, draws
heavily on arXiv:1106.0627 | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of the perturbations in the energy density and the particle
number density in a flat Friedmann-Lemaitre-Robertson-Walker universe in the
radiation-dominated era and in the epoch after decoupling of matter and
radiation is studied. For large-scale perturbations the outcome is in
accordance with treatments in the literature. For small-scale perturbations the
differences are conspicuous. Firstly, in the radiation-dominated era
small-scale perturbations grew proportional to the square root of time.
Secondly, perturbations in the Cold Dark Matter particle number density were,
due to gravitation, coupled to perturbations in the total energy density. This
implies that structure formation could have begun successfully only after
decoupling of matter and radiation. Finally, after decoupling density
perturbations evolved diabatically, i.e., they exchanged heat with their
environment. This heat exchange may have enhanced the growth rate of their mass
sufficiently to explain structure formation in the early universe, a phenomenon
which cannot be understood from adiabatic density perturbations.
| [
{
"created": "Sun, 3 Jan 2016 14:53:49 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2016 12:23:39 GMT",
"version": "v2"
},
{
"created": "Sun, 7 Mar 2021 11:54:29 GMT",
"version": "v3"
}
] | 2021-03-09 | [
[
"Miedema",
"P. G.",
""
]
] | The evolution of the perturbations in the energy density and the particle number density in a flat Friedmann-Lemaitre-Robertson-Walker universe in the radiation-dominated era and in the epoch after decoupling of matter and radiation is studied. For large-scale perturbations the outcome is in accordance with treatments in the literature. For small-scale perturbations the differences are conspicuous. Firstly, in the radiation-dominated era small-scale perturbations grew proportional to the square root of time. Secondly, perturbations in the Cold Dark Matter particle number density were, due to gravitation, coupled to perturbations in the total energy density. This implies that structure formation could have begun successfully only after decoupling of matter and radiation. Finally, after decoupling density perturbations evolved diabatically, i.e., they exchanged heat with their environment. This heat exchange may have enhanced the growth rate of their mass sufficiently to explain structure formation in the early universe, a phenomenon which cannot be understood from adiabatic density perturbations. |
gr-qc/0010113 | Merced Montesinos | Merced Montesinos and Jose David Vergara | Gauge invariance of complex general relativity | 9 pages, Latex file, no figures. To be published in Gen. Rel. Grav | Gen.Rel.Grav. 33 (2001) 921-929 | 10.1023/A:1010268110661 | null | gr-qc | null | In this paper it is implemented how to make compatible the boundary
conditions and the gauge fixing conditions for complex general relativity
written in terms of Ashtekar variables using the Henneaux-Teitelboim-Vergara
approach. Moreover, it is found that at first order in the gauge parameters,
the Hamiltonian action is (on shell) fully gauge-invariant under the gauge
symmetry generated by the first class constraints in the case when spacetime
$\cal M$ has the topology ${\cal M}= R \times \Sigma$ and $\Sigma$ has no
boundary. Thus, the statement that the constraints linear in the momenta do not
contribute to the boundary terms is right, but only in the case when $\Sigma$
has no boundary.
| [
{
"created": "Tue, 31 Oct 2000 17:03:18 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Montesinos",
"Merced",
""
],
[
"Vergara",
"Jose David",
""
]
] | In this paper it is implemented how to make compatible the boundary conditions and the gauge fixing conditions for complex general relativity written in terms of Ashtekar variables using the Henneaux-Teitelboim-Vergara approach. Moreover, it is found that at first order in the gauge parameters, the Hamiltonian action is (on shell) fully gauge-invariant under the gauge symmetry generated by the first class constraints in the case when spacetime $\cal M$ has the topology ${\cal M}= R \times \Sigma$ and $\Sigma$ has no boundary. Thus, the statement that the constraints linear in the momenta do not contribute to the boundary terms is right, but only in the case when $\Sigma$ has no boundary. |
1611.09223 | Antonio Enea Romano | Camilo Santa Velez, Antonio Enea Romano | Newton gauge cosmological perturbations for static spherically symmetric
modifications of the de Sitter metric | 20 pages, version accepted by JCAP, typo in the title corrected | null | 10.1088/1475-7516/2018/05/041 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Static coordinates can be convenient to solve the vacuum Einstein's equations
in presence of spherical symmetry, but for cosmological applications comoving
coordinates are more suitable to describe an expanding Universe, especially in
the framework of cosmological perturbation theory (CPT). Using CPT we develop a
method to transform static spherically symmetric (SSS) modifications of the de
Sitter solution from static coordinates to the Newton gauge. We test the method
with the Schwarzschild de Sitter (SDS) metric and then derive general
expressions for the Bardeen's potentials for a class of SSS metrics obtained by
adding to the de Sitter metric a term linear in the mass and proportional to a
general function of the radius. Using the gauge invariance of the Bardeen's
potentials we then obtain a gauge invariant definition of the turn around
radius. We apply the method to an SSS solution of the Brans-Dicke theory,
confirming the results obtained independently by solving the perturbation
equations in the Newton gauge. The Bardeen's potentials are then derived for
new SSS metrics involving logarithmic, power law and exponential modifications
of the de Sitter metric. We also apply the method to SSS metrics which give
flat rotation curves, computing the radial energy density profile in comoving
coordinates in presence of a cosmological constant.
| [
{
"created": "Thu, 24 Nov 2016 20:28:37 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Mar 2017 14:54:31 GMT",
"version": "v2"
},
{
"created": "Fri, 4 May 2018 09:40:55 GMT",
"version": "v3"
},
{
"created": "Mon, 31 May 2021 17:55:43 GMT",
"version": "v4"
}
] | 2021-06-01 | [
[
"Velez",
"Camilo Santa",
""
],
[
"Romano",
"Antonio Enea",
""
]
] | Static coordinates can be convenient to solve the vacuum Einstein's equations in presence of spherical symmetry, but for cosmological applications comoving coordinates are more suitable to describe an expanding Universe, especially in the framework of cosmological perturbation theory (CPT). Using CPT we develop a method to transform static spherically symmetric (SSS) modifications of the de Sitter solution from static coordinates to the Newton gauge. We test the method with the Schwarzschild de Sitter (SDS) metric and then derive general expressions for the Bardeen's potentials for a class of SSS metrics obtained by adding to the de Sitter metric a term linear in the mass and proportional to a general function of the radius. Using the gauge invariance of the Bardeen's potentials we then obtain a gauge invariant definition of the turn around radius. We apply the method to an SSS solution of the Brans-Dicke theory, confirming the results obtained independently by solving the perturbation equations in the Newton gauge. The Bardeen's potentials are then derived for new SSS metrics involving logarithmic, power law and exponential modifications of the de Sitter metric. We also apply the method to SSS metrics which give flat rotation curves, computing the radial energy density profile in comoving coordinates in presence of a cosmological constant. |
1907.03012 | Marius Oltean | Marius Oltean, Richard J. Epp, Carlos F. Sopuerta, Alessandro D. A. M.
Spallicci, Robert B. Mann | Motion of localized sources in general relativity: gravitational
self-force from quasilocal conservation laws | v1: 41 pages, 12 figures. To be submitted for publication, comments
welcome; v2: 42 pages. Comments and references added; v3: Matches published
version | Phys. Rev. D 101, 064060 (2020) | 10.1103/PhysRevD.101.064060 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An idealized "test" object in general relativity moves along a geodesic.
However, if the object has a finite mass, this will create additional curvature
in the spacetime, causing it to deviate from geodesic motion. If the mass is
nonetheless sufficiently small, such an effect is usually treated
perturbatively and is known as the gravitational self-force due to the object.
This issue is still an open problem in gravitational physics today, motivated
not only by basic foundational interest, but also by the need for its direct
application in gravitational-wave astronomy. In particular, the observation of
extreme-mass-ratio inspirals by the future space-based detector LISA will rely
crucially on an accurate modeling of the self-force driving the orbital
evolution and gravitational wave emission of such systems.
In this paper, we present a novel derivation, based on conservation laws, of
the basic equations of motion for this problem. They are formulated with the
use of a quasilocal (rather than matter) stress-energy-momentum tensor---in
particular, the Brown-York tensor---so as to capture gravitational effects in
the momentum flux of the object, including the self-force. Our formulation and
resulting equations of motion are independent of the choice of the perturbative
gauge. We show that, in addition to the usual gravitational self-force term,
they also lead to an additional "self-pressure" force not found in previous
analyses, and also that our results correctly recover known formulas under
appropriate conditions. Our approach thus offers a fresh geometrical picture
from which to understand the self-force fundamentally, and potentially useful
new avenues for computing it practically.
| [
{
"created": "Fri, 5 Jul 2019 20:09:20 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Nov 2019 18:06:51 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Mar 2020 18:38:47 GMT",
"version": "v3"
}
] | 2020-03-30 | [
[
"Oltean",
"Marius",
""
],
[
"Epp",
"Richard J.",
""
],
[
"Sopuerta",
"Carlos F.",
""
],
[
"Spallicci",
"Alessandro D. A. M.",
""
],
[
"Mann",
"Robert B.",
""
]
] | An idealized "test" object in general relativity moves along a geodesic. However, if the object has a finite mass, this will create additional curvature in the spacetime, causing it to deviate from geodesic motion. If the mass is nonetheless sufficiently small, such an effect is usually treated perturbatively and is known as the gravitational self-force due to the object. This issue is still an open problem in gravitational physics today, motivated not only by basic foundational interest, but also by the need for its direct application in gravitational-wave astronomy. In particular, the observation of extreme-mass-ratio inspirals by the future space-based detector LISA will rely crucially on an accurate modeling of the self-force driving the orbital evolution and gravitational wave emission of such systems. In this paper, we present a novel derivation, based on conservation laws, of the basic equations of motion for this problem. They are formulated with the use of a quasilocal (rather than matter) stress-energy-momentum tensor---in particular, the Brown-York tensor---so as to capture gravitational effects in the momentum flux of the object, including the self-force. Our formulation and resulting equations of motion are independent of the choice of the perturbative gauge. We show that, in addition to the usual gravitational self-force term, they also lead to an additional "self-pressure" force not found in previous analyses, and also that our results correctly recover known formulas under appropriate conditions. Our approach thus offers a fresh geometrical picture from which to understand the self-force fundamentally, and potentially useful new avenues for computing it practically. |
gr-qc/0204048 | Sanjeev S. Seahra | Paul S. Wesson | Classical and quantized aspects of dynamics in five dimensional
relativity | 26 pages, in press in Class. Quant. Grav | Class.Quant.Grav. 19 (2002) 2825-2834 | 10.1088/0264-9381/19/11/306 | null | gr-qc | null | A null path in 5D can appear as a timelike path in 4D, and for a certain
gauge in 5D the motion of a massive particle in 4D obeys the usual quantization
rule with an uncertainty-type relation. Generalizations of this result are
discussed in regard to induced-matter and membrane theory.
| [
{
"created": "Mon, 15 Apr 2002 12:48:33 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Wesson",
"Paul S.",
""
]
] | A null path in 5D can appear as a timelike path in 4D, and for a certain gauge in 5D the motion of a massive particle in 4D obeys the usual quantization rule with an uncertainty-type relation. Generalizations of this result are discussed in regard to induced-matter and membrane theory. |
gr-qc/0203039 | Nils Andersson | N. Andersson, G.L. Comer and D. Langlois | Oscillations of General Relativistic Superfluid Neutron Stars | 27 RevTeX pages, 6 eps figures | Phys.Rev. D66 (2002) 104002 | 10.1103/PhysRevD.66.104002 | null | gr-qc astro-ph | null | We develop a general formalism to treat, in general relativity, the nonradial
oscillations of a superfluid neutron star about static (non-rotating)
configurations. The matter content of these stars can, as a first
approximation, be described by a two-fluid model: one fluid is the neutron
superfluid, which is believed to exist in the core and inner crust of mature
neutron stars; the other fluid is a conglomerate of all charged constituents.
We use a system of equations that governs the perturbations both of the metric
and of the matter variables, whatever the equation of state for the two fluids.
The entrainment effect is explicitly included. We also allow for an outer
envelope composed of ordinary fluid. We derive and implement the junction
conditions for the metric and matter variables at the core/envelope interface.
We investigate how the quasinormal modes of a superfluid star are affected by
changes in the entrainment parameter, and unveil a series of avoided crossings
between the various modes. We provide a proof that all modes of a two-fluid
star must radiate gravitationally. We also discuss the future detectability of
pulsations in a superfluid star and argue that it may be possible to use
gravitational-wave data to constrain the parameters of superfluid neutron
stars.
| [
{
"created": "Tue, 12 Mar 2002 15:27:52 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Andersson",
"N.",
""
],
[
"Comer",
"G. L.",
""
],
[
"Langlois",
"D.",
""
]
] | We develop a general formalism to treat, in general relativity, the nonradial oscillations of a superfluid neutron star about static (non-rotating) configurations. The matter content of these stars can, as a first approximation, be described by a two-fluid model: one fluid is the neutron superfluid, which is believed to exist in the core and inner crust of mature neutron stars; the other fluid is a conglomerate of all charged constituents. We use a system of equations that governs the perturbations both of the metric and of the matter variables, whatever the equation of state for the two fluids. The entrainment effect is explicitly included. We also allow for an outer envelope composed of ordinary fluid. We derive and implement the junction conditions for the metric and matter variables at the core/envelope interface. We investigate how the quasinormal modes of a superfluid star are affected by changes in the entrainment parameter, and unveil a series of avoided crossings between the various modes. We provide a proof that all modes of a two-fluid star must radiate gravitationally. We also discuss the future detectability of pulsations in a superfluid star and argue that it may be possible to use gravitational-wave data to constrain the parameters of superfluid neutron stars. |
1607.03396 | Sourav Dutta | Sourav Dutta, Muthusamy Lakshmanan and Subenoy Chakraborty | Quintom cosmological model and some possible solutions using Lie and
Noether symmetries | 14 pages, 6 figures, accepted in IJMPD | International Journal of Modern Physics D, Vol. 25, No. 14 (2016)
1650110 (17 pages) | 10.1142/S0218271816501108 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work deals with a quintom model of dark energy in the framework
of a spatially flat isotropic and homogeneous
Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. At first, Lie point
symmetry is imposed to the system and the unknown coupled potential of the
model is determined. Then Noether symmetry, which is also a point like symmetry
of the Lagrangian, is imposed on the physical system and the potential takes a
general form. It is shown that the Lie algebra of Noether symmetry is a
sub-algebra of the corresponding Lie algebra of the Lie symmetry. Finally, a
point transformation in the three dimensional augmented space is performed
suitably so that one of the variables become cyclic and as a result there is
considerable simplification to the physical system. Hence conserved quantities
(i.e, constants of motion) are expressed in a compact form and cosmological
solutions are evaluated and analyzed in the present context.
| [
{
"created": "Wed, 29 Jun 2016 07:19:37 GMT",
"version": "v1"
}
] | 2016-09-27 | [
[
"Dutta",
"Sourav",
""
],
[
"Lakshmanan",
"Muthusamy",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present work deals with a quintom model of dark energy in the framework of a spatially flat isotropic and homogeneous Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. At first, Lie point symmetry is imposed to the system and the unknown coupled potential of the model is determined. Then Noether symmetry, which is also a point like symmetry of the Lagrangian, is imposed on the physical system and the potential takes a general form. It is shown that the Lie algebra of Noether symmetry is a sub-algebra of the corresponding Lie algebra of the Lie symmetry. Finally, a point transformation in the three dimensional augmented space is performed suitably so that one of the variables become cyclic and as a result there is considerable simplification to the physical system. Hence conserved quantities (i.e, constants of motion) are expressed in a compact form and cosmological solutions are evaluated and analyzed in the present context. |
1711.06220 | Muhammad Sharif | M. Sharif and Aisha Siddiqa | Polarization Modes of Gravitational Wave for Viable f(R) Models | 15 pages, no figure, to appear in Astrophys. Space Sci | Astrophys. Space Sci. 362(2017)226 | 10.1007/s10509-017-3207-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the gravitational wave polarization modes for some
particular $f(R)$ models using Newman-Penrose formalism. We find two extra
scalar modes of gravitational wave (longitudinal and transversal modes) in
addition to two tensor modes of general relativity. We conclude that
gravitational waves correspond to class $II_{6}$ under the Lorentz-invariant
E(2) classification of plane null waves for these $f(R)$ models.
| [
{
"created": "Sat, 11 Nov 2017 05:06:22 GMT",
"version": "v1"
}
] | 2017-12-06 | [
[
"Sharif",
"M.",
""
],
[
"Siddiqa",
"Aisha",
""
]
] | In this paper, we study the gravitational wave polarization modes for some particular $f(R)$ models using Newman-Penrose formalism. We find two extra scalar modes of gravitational wave (longitudinal and transversal modes) in addition to two tensor modes of general relativity. We conclude that gravitational waves correspond to class $II_{6}$ under the Lorentz-invariant E(2) classification of plane null waves for these $f(R)$ models. |
0908.0186 | Yousuke Itoh | Yousuke Itoh, Toshifumi Futamase, Makoto Hattori | A method to measure a relative transverse velocity of
source-lens-observer system using gravitational lensing of gravitational
waves | 27 pages, 9 figures. Accepted for publication in Physical Review D | Phys.Rev.D80:044009,2009 | 10.1103/PhysRevD.80.044009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves propagate along null geodesics like light rays in the
geometrical optics approximation, and they may have a chance to suffer from
gravitational lensing by intervening objects, as is the case for
electromagnetic waves. Long wavelength of gravitational waves and compactness
of possible sources may enable us to extract information in the interference
among the lensed images. We point out that the interference term contains
information of relative transverse velocity of the source-lens-observer system,
which may be obtained by possible future space-borne gravitational wave
detectors such as BBO/DECIGO.
| [
{
"created": "Mon, 3 Aug 2009 04:31:48 GMT",
"version": "v1"
}
] | 2010-10-12 | [
[
"Itoh",
"Yousuke",
""
],
[
"Futamase",
"Toshifumi",
""
],
[
"Hattori",
"Makoto",
""
]
] | Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves. Long wavelength of gravitational waves and compactness of possible sources may enable us to extract information in the interference among the lensed images. We point out that the interference term contains information of relative transverse velocity of the source-lens-observer system, which may be obtained by possible future space-borne gravitational wave detectors such as BBO/DECIGO. |
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