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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0901.1628 | Larne Pekowsky | Michael Boyle, Duncan A. Brown, Larne Pekowsky | Comparison of high-accuracy numerical simulations of black-hole binaries
with stationary phase post-Newtonian template waveforms for Initial and
Advanced LIGO | 20 pages, 11 figures. Presented at NRDA 2008 | Class.Quant.Grav.26:114006,2009 | 10.1088/0264-9381/26/11/114006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effectiveness of stationary-phase approximated post-Newtonian
waveforms currently used by ground-based gravitational-wave detectors to search
for the coalescence of binary black holes by comparing them to an accurate
waveform obtained from numerical simulation of an equal-mass non-spinning
binary black hole inspiral, merger and ringdown. We perform this study for the
Initial- and Advanced-LIGO detectors. We find that overlaps between the
templates and signal can be improved by integrating the match filter to higher
frequencies than used currently. We propose simple analytic frequency cutoffs
for both Initial and Advanced LIGO, which achieve nearly optimal matches, and
can easily be extended to unequal-mass, spinning systems. We also find that
templates that include terms in the phase evolution up to 3.5 pN order are
nearly always better, and rarely significantly worse, than 2.0 pN templates
currently in use. For Initial LIGO we recommend a strategy using templates that
include a recently introduced pseudo-4.0 pN term in the low-mass ($M \leq 35
\MSun$) region, and 3.5 pN templates allowing unphysical values of the
symmetric reduced mass $\eta$ above this. This strategy always achieves
overlaps within 0.3% of the optimum, for the data used here. For Advanced LIGO
we recommend a strategy using 3.5 pN templates up to $M=12 \MSun$, 2.0 pN
templates up to $M=21 \MSun$, pseudo-4.0 pN templates up to $65 \MSun$, and 3.5
pN templates with unphysical $\eta$ for higher masses. This strategy always
achieves overlaps within 0.7% of the optimum for Advanced LIGO.
| [
{
"created": "Mon, 12 Jan 2009 17:58:37 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jan 2009 02:52:31 GMT",
"version": "v2"
}
] | 2009-06-10 | [
[
"Boyle",
"Michael",
""
],
[
"Brown",
"Duncan A.",
""
],
[
"Pekowsky",
"Larne",
""
]
] | We study the effectiveness of stationary-phase approximated post-Newtonian waveforms currently used by ground-based gravitational-wave detectors to search for the coalescence of binary black holes by comparing them to an accurate waveform obtained from numerical simulation of an equal-mass non-spinning binary black hole inspiral, merger and ringdown. We perform this study for the Initial- and Advanced-LIGO detectors. We find that overlaps between the templates and signal can be improved by integrating the match filter to higher frequencies than used currently. We propose simple analytic frequency cutoffs for both Initial and Advanced LIGO, which achieve nearly optimal matches, and can easily be extended to unequal-mass, spinning systems. We also find that templates that include terms in the phase evolution up to 3.5 pN order are nearly always better, and rarely significantly worse, than 2.0 pN templates currently in use. For Initial LIGO we recommend a strategy using templates that include a recently introduced pseudo-4.0 pN term in the low-mass ($M \leq 35 \MSun$) region, and 3.5 pN templates allowing unphysical values of the symmetric reduced mass $\eta$ above this. This strategy always achieves overlaps within 0.3% of the optimum, for the data used here. For Advanced LIGO we recommend a strategy using 3.5 pN templates up to $M=12 \MSun$, 2.0 pN templates up to $M=21 \MSun$, pseudo-4.0 pN templates up to $65 \MSun$, and 3.5 pN templates with unphysical $\eta$ for higher masses. This strategy always achieves overlaps within 0.7% of the optimum for Advanced LIGO. |
1703.01415 | Sabine Hossenfelder | S. Hossenfelder | A Covariant Version of Verlinde's Emergent Gravity | correction and reference added. 15 pages, no figures | Phys. Rev. D 95, 124018 (2017) | 10.1103/PhysRevD.95.124018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A generally covariant version of Erik Verlinde's emergent gravity model is
proposed. The Lagrangian constructed here allows an improved interpretation of
the underlying mechanism. It suggests that de-Sitter space is filled with a
vector-field that couples to baryonic matter and, by dragging on it, creates an
effect similar to dark matter. We solve the covariant equation of motion in the
background of a Schwarzschild space-time and obtain correction terms to the
non-covariant expression. Furthermore, we demonstrate that the vector field can
also mimic dark energy.
| [
{
"created": "Sat, 4 Mar 2017 08:40:27 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Mar 2017 15:43:23 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Jun 2017 06:43:15 GMT",
"version": "v3"
}
] | 2017-06-28 | [
[
"Hossenfelder",
"S.",
""
]
] | A generally covariant version of Erik Verlinde's emergent gravity model is proposed. The Lagrangian constructed here allows an improved interpretation of the underlying mechanism. It suggests that de-Sitter space is filled with a vector-field that couples to baryonic matter and, by dragging on it, creates an effect similar to dark matter. We solve the covariant equation of motion in the background of a Schwarzschild space-time and obtain correction terms to the non-covariant expression. Furthermore, we demonstrate that the vector field can also mimic dark energy. |
1512.03095 | Sergio Ulhoa | S.C. Ulhoa | On the Quantization of the Charge-Mass Ratio | null | Gen Relativ Gravit (2017) 49: 3 | 10.1007/s10714-016-2170-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with the problem of describing fundamental particles. The
Einstein-Rosen approach was revisited to explain que charge-mass ratio
quantization. Such a result is obtained once a quantization prescription is
applied to the expression of gravitational energy defined in the realm of
teleparallel gravity.
| [
{
"created": "Sat, 5 Dec 2015 23:19:29 GMT",
"version": "v1"
}
] | 2016-12-02 | [
[
"Ulhoa",
"S. C.",
""
]
] | The paper deals with the problem of describing fundamental particles. The Einstein-Rosen approach was revisited to explain que charge-mass ratio quantization. Such a result is obtained once a quantization prescription is applied to the expression of gravitational energy defined in the realm of teleparallel gravity. |
gr-qc/9307016 | Ulvi Yurtsever | Ulvi Yurtsever | The origin of spacetime topology and generalizations of quantum field
theory | 23 pages, UCSBTH-92-45 | Class.Quant.Grav.11:1013-1026,1994 | 10.1088/0264-9381/11/4/017 | null | gr-qc | null | The research effort reported in this paper is directed, in a broad sense,
towards understanding the small-scale structure of spacetime. The fundamental
question that guides our discussion is ``what is the physical content of
spacetime topology?" In classical physics, if spacetime, $(X, \tau )$, has
sufficiently regular topology, and if sufficiently many fields exist to allow
us to observe all continuous functions on $X$, then this collection of
continuous functions uniquely determines both the set of points $X$ and the
topology $\tau$ on it. To explore the small-scale structure of spacetime, we
are led to consider the physical fields (the observables) not as classical
(continuous functions) but as quantum operators, and the fundamental observable
as not the collection of all continuous functions but the local algebra of
quantum field operators. In pursuing our approach further, we develop a number
of generalizations of quantum field theory through which it becomes possible to
talk about quantum fields defined on arbitrary topological spaces. Our ultimate
generalization dispenses with the fixed background topological space altogether
and proposes that the fundamental observable should be taken as a lattice (or
more specifically a ``frame," in the sense of set theory) of closed subalgebras
of an abstract $C^{\ast}$ algebra. Our discussion concludes with the definition
and some elementary
| [
{
"created": "Wed, 14 Jul 1993 01:32:07 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Yurtsever",
"Ulvi",
""
]
] | The research effort reported in this paper is directed, in a broad sense, towards understanding the small-scale structure of spacetime. The fundamental question that guides our discussion is ``what is the physical content of spacetime topology?" In classical physics, if spacetime, $(X, \tau )$, has sufficiently regular topology, and if sufficiently many fields exist to allow us to observe all continuous functions on $X$, then this collection of continuous functions uniquely determines both the set of points $X$ and the topology $\tau$ on it. To explore the small-scale structure of spacetime, we are led to consider the physical fields (the observables) not as classical (continuous functions) but as quantum operators, and the fundamental observable as not the collection of all continuous functions but the local algebra of quantum field operators. In pursuing our approach further, we develop a number of generalizations of quantum field theory through which it becomes possible to talk about quantum fields defined on arbitrary topological spaces. Our ultimate generalization dispenses with the fixed background topological space altogether and proposes that the fundamental observable should be taken as a lattice (or more specifically a ``frame," in the sense of set theory) of closed subalgebras of an abstract $C^{\ast}$ algebra. Our discussion concludes with the definition and some elementary |
gr-qc/0207083 | Metin Gurses | Metin Gurses (Bilkent University) and Ozgur Sarioglu (METU) | Accelerated Born-Infeld Metrics in Kerr-Schild Geometry | Latex file (12 pp) | Class.Quant.Grav. 20 (2003) 351-358 | 10.1088/0264-9381/20/2/308 | null | gr-qc hep-th | null | We consider Einstein Born-Infeld theory with a null fluid in Kerr-Schild
Geometry. We find accelerated charge solutions of this theory. Our solutions
reduce to the Plebanski solution when the acceleration vanishes and to the
Bonnor-Vaidya solution as the Born-Infeld parameter b goes to infinity. We also
give the explicit form of the energy flux formula due to the acceleration of
the charged sources.
| [
{
"created": "Mon, 22 Jul 2002 08:36:18 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Gurses",
"Metin",
"",
"Bilkent University"
],
[
"Sarioglu",
"Ozgur",
"",
"METU"
]
] | We consider Einstein Born-Infeld theory with a null fluid in Kerr-Schild Geometry. We find accelerated charge solutions of this theory. Our solutions reduce to the Plebanski solution when the acceleration vanishes and to the Bonnor-Vaidya solution as the Born-Infeld parameter b goes to infinity. We also give the explicit form of the energy flux formula due to the acceleration of the charged sources. |
0711.2170 | Carsten Gundlach | Carsten Gundlach | Summary of GR18 Numerical Relativity parallel sessions (B1/B2 and B2),
Sydney, 8-13 July 2007 | References updated, to be published in CQG | Class.Quant.Grav.25:114019,2008 | 10.1088/0264-9381/25/11/114019 | null | gr-qc | null | The numerical relativity session at GR18 was dominated by physics results on
binary black hole mergers. Several groups can now simulate these from a time
when the post-Newtonian equations of motion are still applicable, through
several orbits and the merger to the ringdown phase, obtaining plausible
gravitational waves at infinity, and showing some evidence of convergence with
resolution. The results of different groups roughly agree. This new-won
confidence has been used by these groups to begin mapping out the
(finite-dimensional) initial data space of the problem, with a particular focus
on the effect of black hole spins, and the acceleration by gravitational wave
recoil to hundreds of km/s of the final merged black hole. Other work was
presented on a variety of topics, such as evolutions with matter, extreme mass
ratio inspirals, and technical issues such as gauge choices.
| [
{
"created": "Wed, 14 Nov 2007 11:42:51 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jan 2008 10:46:20 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gundlach",
"Carsten",
""
]
] | The numerical relativity session at GR18 was dominated by physics results on binary black hole mergers. Several groups can now simulate these from a time when the post-Newtonian equations of motion are still applicable, through several orbits and the merger to the ringdown phase, obtaining plausible gravitational waves at infinity, and showing some evidence of convergence with resolution. The results of different groups roughly agree. This new-won confidence has been used by these groups to begin mapping out the (finite-dimensional) initial data space of the problem, with a particular focus on the effect of black hole spins, and the acceleration by gravitational wave recoil to hundreds of km/s of the final merged black hole. Other work was presented on a variety of topics, such as evolutions with matter, extreme mass ratio inspirals, and technical issues such as gauge choices. |
1208.3038 | Aaron Zimmerman | David A. Nichols, Aaron Zimmerman, Yanbei Chen, Geoffrey Lovelace,
Keith D. Matthews, Robert Owen, Fan Zhang, Kip S. Thorne | Visualizing Spacetime Curvature via Frame-Drag Vortexes and Tidal
Tendexes III. Quasinormal Pulsations of Schwarzschild and Kerr Black Holes | 53 pages with an overview of major results in the first 11 pages, 26
figures. v2: Very minor changes to reflect published version. v3: Fixed Ref 7 | Phys. Rev. D 86, 104028 (2012) | 10.1103/PhysRevD.86.104028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent papers, we and colleagues have introduced a way to visualize the
full vacuum Riemann curvature tensor using frame-drag vortex lines and their
vorticities, and tidal tendex lines and their tendicities. We have also
introduced the concepts of horizon vortexes and tendexes and 3-D vortexes and
tendexes (regions where vorticities or tendicities are large). Using these
concepts, we discover a number of previously unknown features of quasinormal
modes of Schwarzschild and Kerr black holes. These modes can be classified by
mode indexes (n,l,m), and parity, which can be electric [(-1)^l] or magnetic
[(-1)^(l+1)]. Among our discoveries are these: (i) There is a near duality
between modes of the same (n,l,m): a duality in which the tendex and vortex
structures of electric-parity modes are interchanged with the vortex and tendex
structures (respectively) of magnetic-parity modes. (ii) This near duality is
perfect for the modes' complex eigenfrequencies (which are well known to be
identical) and perfect on the horizon; it is slightly broken in the equatorial
plane of a non-spinning hole, and the breaking becomes greater out of the
equatorial plane, and greater as the hole is spun up; but even out of the plane
for fast-spinning holes, the duality is surprisingly good. (iii)
Electric-parity modes can be regarded as generated by 3-D tendexes that stick
radially out of the horizon. As these "longitudinal," near-zone tendexes rotate
or oscillate, they generate longitudinal-transverse near-zone vortexes and
tendexes, and outgoing and ingoing gravitational waves. The ingoing waves act
back on the longitudinal tendexes, driving them to slide off the horizon, which
results in decay of the mode's strength. (iv) By duality, magnetic-parity modes
are driven in this same manner by longitudinal, near-zone vortexes that stick
out of the horizon. [Abstract abridged.]
| [
{
"created": "Wed, 15 Aug 2012 06:20:27 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Dec 2012 22:41:41 GMT",
"version": "v2"
},
{
"created": "Thu, 31 Jan 2013 16:27:40 GMT",
"version": "v3"
}
] | 2015-03-20 | [
[
"Nichols",
"David A.",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Lovelace",
"Geoffrey",
""
],
[
"Matthews",
"Keith D.",
""
],
[
"Owen",
"Robert",
""
],
[
"Zhang",
"Fan",
""
],
[
"Thorne",
"Kip S.",
""
]
] | In recent papers, we and colleagues have introduced a way to visualize the full vacuum Riemann curvature tensor using frame-drag vortex lines and their vorticities, and tidal tendex lines and their tendicities. We have also introduced the concepts of horizon vortexes and tendexes and 3-D vortexes and tendexes (regions where vorticities or tendicities are large). Using these concepts, we discover a number of previously unknown features of quasinormal modes of Schwarzschild and Kerr black holes. These modes can be classified by mode indexes (n,l,m), and parity, which can be electric [(-1)^l] or magnetic [(-1)^(l+1)]. Among our discoveries are these: (i) There is a near duality between modes of the same (n,l,m): a duality in which the tendex and vortex structures of electric-parity modes are interchanged with the vortex and tendex structures (respectively) of magnetic-parity modes. (ii) This near duality is perfect for the modes' complex eigenfrequencies (which are well known to be identical) and perfect on the horizon; it is slightly broken in the equatorial plane of a non-spinning hole, and the breaking becomes greater out of the equatorial plane, and greater as the hole is spun up; but even out of the plane for fast-spinning holes, the duality is surprisingly good. (iii) Electric-parity modes can be regarded as generated by 3-D tendexes that stick radially out of the horizon. As these "longitudinal," near-zone tendexes rotate or oscillate, they generate longitudinal-transverse near-zone vortexes and tendexes, and outgoing and ingoing gravitational waves. The ingoing waves act back on the longitudinal tendexes, driving them to slide off the horizon, which results in decay of the mode's strength. (iv) By duality, magnetic-parity modes are driven in this same manner by longitudinal, near-zone vortexes that stick out of the horizon. [Abstract abridged.] |
1502.04626 | Azam Izadi | Azam Izadi and Shadi Sajedi Shacker | Studying the Supernova luminosity distance in Palatini formalism
considering the role of causal structure constant | 17 pages, 3 figures. arXiv admin note: text overlap with
arXiv:0811.2832 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The speed of light is a complicated synthesizer quantity with distinctive
origins which lead to coincident values in the standard theory. Due to the fact
that different aspects of speed of light do not coincide in the local inertial
frame for different Palatini modified gravity theories, when deviating from
general relativity, one should consider which aspect of speed of light should
be taken into account meticulously and unambiguously. The aim of this study is
mainly investigating the modification of the SN Ia luminosity distance, for two
f(R) and f(RR) extended theories in the local inertial frame in Palatini
formalism considering different aspects of the speed of light. Besides the
local inertial frame itself should be determined in the Palatini formalism as a
frame in which the Einstein Equivalence Principle is valid. SN Ia luminosity
distance should be modified considering the variation of the space-time causal
structure constant for two well-known extended models in Palatini formalism.
| [
{
"created": "Fri, 13 Feb 2015 11:45:15 GMT",
"version": "v1"
}
] | 2015-02-17 | [
[
"Izadi",
"Azam",
""
],
[
"Shacker",
"Shadi Sajedi",
""
]
] | The speed of light is a complicated synthesizer quantity with distinctive origins which lead to coincident values in the standard theory. Due to the fact that different aspects of speed of light do not coincide in the local inertial frame for different Palatini modified gravity theories, when deviating from general relativity, one should consider which aspect of speed of light should be taken into account meticulously and unambiguously. The aim of this study is mainly investigating the modification of the SN Ia luminosity distance, for two f(R) and f(RR) extended theories in the local inertial frame in Palatini formalism considering different aspects of the speed of light. Besides the local inertial frame itself should be determined in the Palatini formalism as a frame in which the Einstein Equivalence Principle is valid. SN Ia luminosity distance should be modified considering the variation of the space-time causal structure constant for two well-known extended models in Palatini formalism. |
1406.6551 | Maciej Wielgus | Maciek Wielgus, George F. R. Ellis, Frederic H. Vincent and Marek A.
Abramowicz | Cosmic background radiation in the vicinity of a Schwarzschild black
hole: no classic firewall | 18 pages, 4 figures, accepted for publication in Phys. Rev. D | Phys. Rev. D 90, 124024 (2014) | 10.1103/PhysRevD.90.124024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Cosmic Blackbody Background Radiation pervades the entire Universe, and
so falls into every astrophysical black hole. The blueshift of the infalling
photons, measured by a static observer, is infinite at the event horizon. This
raises a question as to whether a "firewall" of high energy density may form
just outside the horizon, or whether the effect can be attributed exclusively
to a singular behavior of the static observer's frame at the horizon. In
principle, the presence of such firewall may alter the motion of the infalling
matter, influence the black hole evolution, or even invalidate the {\it vacuum}
Einstein field equation solution as a realistic approximation for black holes.
In this paper we show by means of analytic calculations that all these effects
indeed exist, but their magnitude is typically negligibly small, even though
the matter stress tensor is divergent in the static frame at $r=2M$. That is
not surprising because of the divergent relation of that frame to a freely
falling frame as $r \rightarrow 2M$; however it represents a kind of classical
analogue for the Black Hole Complementarity principle that has been proposed
for quantum effects near a black hole. What is perhaps more surprising is the
divergence of the radiation stress tensor for massive particles moving on
circular geodesic orbits for values of $r$ approaching $r = 3M$. However such
orbits will not occur for infalling matter in realistic accretion discs.
| [
{
"created": "Wed, 25 Jun 2014 12:53:01 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Nov 2014 14:18:53 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Dec 2014 14:28:45 GMT",
"version": "v3"
}
] | 2014-12-16 | [
[
"Wielgus",
"Maciek",
""
],
[
"Ellis",
"George F. R.",
""
],
[
"Vincent",
"Frederic H.",
""
],
[
"Abramowicz",
"Marek A.",
""
]
] | The Cosmic Blackbody Background Radiation pervades the entire Universe, and so falls into every astrophysical black hole. The blueshift of the infalling photons, measured by a static observer, is infinite at the event horizon. This raises a question as to whether a "firewall" of high energy density may form just outside the horizon, or whether the effect can be attributed exclusively to a singular behavior of the static observer's frame at the horizon. In principle, the presence of such firewall may alter the motion of the infalling matter, influence the black hole evolution, or even invalidate the {\it vacuum} Einstein field equation solution as a realistic approximation for black holes. In this paper we show by means of analytic calculations that all these effects indeed exist, but their magnitude is typically negligibly small, even though the matter stress tensor is divergent in the static frame at $r=2M$. That is not surprising because of the divergent relation of that frame to a freely falling frame as $r \rightarrow 2M$; however it represents a kind of classical analogue for the Black Hole Complementarity principle that has been proposed for quantum effects near a black hole. What is perhaps more surprising is the divergence of the radiation stress tensor for massive particles moving on circular geodesic orbits for values of $r$ approaching $r = 3M$. However such orbits will not occur for infalling matter in realistic accretion discs. |
2109.01398 | Guillem Dom\`enech | Guillem Dom\`enech | Scalar induced gravitational waves review | Invited review for universe. 97 pages. 10 figures. Matches published
version | Universe 7 (2021) 11, 398 | 10.3390/universe7110398 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a review on the state-of-the-art of gravitational waves induced by
primordial fluctuations, so-called induced gravitational waves. We present the
intuitive physics behind induced gravitational waves and we revisit and unify
the general analytical formulation. We then present general formulas in a
compact form, ready to be applied. This review places emphasis on the open
possibility that the primordial universe experienced a different expansion
history than the often assumed radiation dominated cosmology. We hope that
anyone interested in the topic will become aware of current advances in the
cosmology of induced gravitational waves, as well as becoming familiar with the
calculations behind.
| [
{
"created": "Fri, 3 Sep 2021 09:44:21 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Nov 2021 08:11:41 GMT",
"version": "v2"
}
] | 2021-11-08 | [
[
"Domènech",
"Guillem",
""
]
] | We provide a review on the state-of-the-art of gravitational waves induced by primordial fluctuations, so-called induced gravitational waves. We present the intuitive physics behind induced gravitational waves and we revisit and unify the general analytical formulation. We then present general formulas in a compact form, ready to be applied. This review places emphasis on the open possibility that the primordial universe experienced a different expansion history than the often assumed radiation dominated cosmology. We hope that anyone interested in the topic will become aware of current advances in the cosmology of induced gravitational waves, as well as becoming familiar with the calculations behind. |
gr-qc/9611014 | Shuhei Mano | Shuhei Mano and Eiichi Takasugi | Analytic Solutions of the Teukolsky Equation and their Properties | 28 pages | Prog.Theor.Phys. 97 (1997) 213-232 | 10.1143/PTP.97.213 | null | gr-qc | null | The analytical solutions reported in our previous paper are given as series
of hypergeometric or Coulomb wave functions. By using them, we can get the
Teukolsky functions analytically in a desired accuracy. For the computation,
the deep understanding of their properties is necessary. We summarize the main
result: The relative normalization between the solutions with a spin weight s
and -s is given analytically by using the Teukolsky-Starobinsky (T-S)
identities. By examining the asymptotic behaviors of our solution and combined
with the T-S identities and the Wronskian, we found nontrivial identities
between the sums of coefficients of the series. These identities will serve to
make various expression in simpler forms and also become a powerful tool to
test the accuracy of the computation. As an application, we investigated the
absorption rate and the evaporation rate of black hole and obtain interesting
analytic results.
| [
{
"created": "Wed, 6 Nov 1996 10:05:33 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Mano",
"Shuhei",
""
],
[
"Takasugi",
"Eiichi",
""
]
] | The analytical solutions reported in our previous paper are given as series of hypergeometric or Coulomb wave functions. By using them, we can get the Teukolsky functions analytically in a desired accuracy. For the computation, the deep understanding of their properties is necessary. We summarize the main result: The relative normalization between the solutions with a spin weight s and -s is given analytically by using the Teukolsky-Starobinsky (T-S) identities. By examining the asymptotic behaviors of our solution and combined with the T-S identities and the Wronskian, we found nontrivial identities between the sums of coefficients of the series. These identities will serve to make various expression in simpler forms and also become a powerful tool to test the accuracy of the computation. As an application, we investigated the absorption rate and the evaporation rate of black hole and obtain interesting analytic results. |
2301.01692 | Sergei Vergeles | S. N. Vergeles | Phase transition near the Big Bang in the lattice theory of gravity and
some cosmological considerations | 15 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Lattice regularization of the theory of gravity provides a new possibility
for study of the Big Bang problem. Moreover, the very possibility of studying
the state of the Universe at the highest temperatures appears. In the 2D and 4D
lattice theories of gravity, the existence of a high-temperature phase is
proved, which is characterized by the folding of space into a point and zeroing
of the energy-momentum tensor. This fact leads to the hypothesis that there are
at least two phases in the 4D lattice theory, and the main properties of the
high-temperature phase are similar to those described above. The solution of
the Einstein equation in the low temperature phase within the framework of the
Friedmann paradigm with a finite bare cosmological constant is mathematically
correct, since all local physical quantities (energy density including vacuum
energy, etc.) on the lattice are finite. As a result, a solution is obtained
that demonstrates an exponential growth of the cosmological scale factor $a(t)$
in the initial period of evolution (inflation phase of the Universe) and then
passes into a power law ($a(t)\propto\sqrt{t}$).
| [
{
"created": "Tue, 3 Jan 2023 08:30:00 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Mar 2023 14:39:37 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Apr 2023 11:26:39 GMT",
"version": "v3"
},
{
"created": "Tue, 2 May 2023 09:28:23 GMT",
"version": "v4"
},
{
"created": "Thu, 11 Jan 2024 12:54:38 GMT",
"version": "v5"
},
{
"created": "Thu, 11 Apr 2024 10:35:07 GMT",
"version": "v6"
},
{
"created": "Thu, 27 Jun 2024 11:47:18 GMT",
"version": "v7"
}
] | 2024-06-28 | [
[
"Vergeles",
"S. N.",
""
]
] | Lattice regularization of the theory of gravity provides a new possibility for study of the Big Bang problem. Moreover, the very possibility of studying the state of the Universe at the highest temperatures appears. In the 2D and 4D lattice theories of gravity, the existence of a high-temperature phase is proved, which is characterized by the folding of space into a point and zeroing of the energy-momentum tensor. This fact leads to the hypothesis that there are at least two phases in the 4D lattice theory, and the main properties of the high-temperature phase are similar to those described above. The solution of the Einstein equation in the low temperature phase within the framework of the Friedmann paradigm with a finite bare cosmological constant is mathematically correct, since all local physical quantities (energy density including vacuum energy, etc.) on the lattice are finite. As a result, a solution is obtained that demonstrates an exponential growth of the cosmological scale factor $a(t)$ in the initial period of evolution (inflation phase of the Universe) and then passes into a power law ($a(t)\propto\sqrt{t}$). |
1110.5756 | Francisco Lobo | Christian G. Boehmer, Tiberiu Harko, Francisco S. N. Lobo | Wormhole geometries in modified teleparralel gravity and the energy
conditions | 8 pages, 4 figures. V2: major revision, discussion added; to appear
in PRD | Phys.Rev.D85:044033,2012 | 10.1103/PhysRevD.85.044033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we explore the possibility that static and spherically
symmetric traversable wormhole geometries are supported by modified
teleparallel gravity or f(T) gravity, where T is the torsion scalar.
Considering the field equations with an off-diagonal tetrad, a plethora of
asymptotically flat exact solutions are found, that satisfy the weak and the
null energy conditions throughout the spacetime. More specifically, considering
T=0, we find the general conditions for a wormhole satisfying the energy
conditions at the throat and present specific examples. Secondly, considering
specific choices for the f(T) form and for the redshift and shape functions,
several solutions of wormhole geometries are found that satisfy the energy
conditions throughout the spacetime. As in their general relativistic
counterparts, these f(T) wormhole geometries present far-reaching physical and
cosmological implications, such as being theoretically useful as shortcuts in
spacetime and for inducing closed timelike curves, possibly violating
causality.
| [
{
"created": "Wed, 26 Oct 2011 10:14:11 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Jan 2012 22:11:27 GMT",
"version": "v2"
}
] | 2012-02-16 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | In this work, we explore the possibility that static and spherically symmetric traversable wormhole geometries are supported by modified teleparallel gravity or f(T) gravity, where T is the torsion scalar. Considering the field equations with an off-diagonal tetrad, a plethora of asymptotically flat exact solutions are found, that satisfy the weak and the null energy conditions throughout the spacetime. More specifically, considering T=0, we find the general conditions for a wormhole satisfying the energy conditions at the throat and present specific examples. Secondly, considering specific choices for the f(T) form and for the redshift and shape functions, several solutions of wormhole geometries are found that satisfy the energy conditions throughout the spacetime. As in their general relativistic counterparts, these f(T) wormhole geometries present far-reaching physical and cosmological implications, such as being theoretically useful as shortcuts in spacetime and for inducing closed timelike curves, possibly violating causality. |
1611.00619 | Ahmida Bendjoudi | A. Bendjoudi and N. Mebarki | The Quantum Trihedron | 3 pages, 2 figures | CHIN. PHYS. LETT. Vol. 33, No. 11 (2016) 110401 | 10.1088/0256-307X/33/11/110401 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The convex hull on three points in two dimensional euclidean space of three
flat edges (trihedron) was studied. The Bohr-Sommerfeld quantization of the
area of space is performed. It is shown that it reproduces exactly the
equidistant spacing spectrum found elsewhere.
| [
{
"created": "Tue, 1 Nov 2016 17:25:58 GMT",
"version": "v1"
}
] | 2016-11-03 | [
[
"Bendjoudi",
"A.",
""
],
[
"Mebarki",
"N.",
""
]
] | The convex hull on three points in two dimensional euclidean space of three flat edges (trihedron) was studied. The Bohr-Sommerfeld quantization of the area of space is performed. It is shown that it reproduces exactly the equidistant spacing spectrum found elsewhere. |
0709.2741 | Stefano Ansoldi | Stefano Ansoldi | Vacuum and semiclassical gravity: a difficulty and its bewildering
significance | 11 pages, LaTeX, 4 figure; talk given at the workshop "From Quantum
to Emergent Gravity: Theory and Phenomenology", June, 11-15 2007, Trieste,
Italy (http://www.sissa.it/app/QGconference); submitted to the "Proceedings
of Science" (http://pos.sissa.it) | PoSQG-Ph:004,2007 | null | KUNS-2094 | gr-qc hep-th | null | We review a long-standing difficulty in some semiclassical models of vacuum
and vacuum decay. Surprisingly enough these models, careless of their
transparent formulation, are affected by, both, technical and conceptual
issues. After proving some general results that are relevant for, both, the
Euclidean and Lorentzian sectors of their dynamics, we briefly highlight their
importance in connection with the issues discussed before, arguing that their
solution might be interesting in our quest for quantum gravity.
| [
{
"created": "Tue, 18 Sep 2007 01:44:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ansoldi",
"Stefano",
""
]
] | We review a long-standing difficulty in some semiclassical models of vacuum and vacuum decay. Surprisingly enough these models, careless of their transparent formulation, are affected by, both, technical and conceptual issues. After proving some general results that are relevant for, both, the Euclidean and Lorentzian sectors of their dynamics, we briefly highlight their importance in connection with the issues discussed before, arguing that their solution might be interesting in our quest for quantum gravity. |
1405.6597 | Seyed Meraj Mousavi Rasouli | S. M. M. Rasouli | Kasner Solution in Brans-Dicke Theory and its Corresponding Reduced
Cosmology | 4 pages, Contribution to the Spanish Relativity Meeting in Portugal,
September 3-7, 2012 (ERE2012), Guimaraes, Portugal | Springer Proc. in Math. & Statist. 60, 371 (2014) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a brief review of the modified Brans-Dicke theory (MBDT) in
arbitrary dimensions, whereby the ($N+1$)-dimensional field equations reduce to
the $N$-dimensional $(ND)$ configuration with sources and an effective induced
scalar potential. We then investigate a generalized Bianchi type~I anisotropic
cosmology in $5D$ BD theory that leads to an extended Kasner solution. By
employing the original equations of MBDT, we probe the reduced Kasner cosmology
on the hypersuface with proceeding the investigations for a few cosmological
quantities, explaining their properties for some cosmological models.}
| [
{
"created": "Mon, 26 May 2014 14:52:53 GMT",
"version": "v1"
}
] | 2014-05-27 | [
[
"Rasouli",
"S. M. M.",
""
]
] | We present a brief review of the modified Brans-Dicke theory (MBDT) in arbitrary dimensions, whereby the ($N+1$)-dimensional field equations reduce to the $N$-dimensional $(ND)$ configuration with sources and an effective induced scalar potential. We then investigate a generalized Bianchi type~I anisotropic cosmology in $5D$ BD theory that leads to an extended Kasner solution. By employing the original equations of MBDT, we probe the reduced Kasner cosmology on the hypersuface with proceeding the investigations for a few cosmological quantities, explaining their properties for some cosmological models.} |
2303.01910 | Ekrem Demirbo\u{g}a | Ekrem S. Demirbo\u{g}a, Yakup Emre \c{S}ahin, Fethi M. Ramazano\u{g}lu | Subtleties in constraining gravity theories with mass-radius data | 18 pages, 11 figures. Published version. A larger dataset was used in
the analysis and a chapter explaining the effect of the dataset size is added
in this version | null | 10.1103/PhysRevD.108.024028 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Simultaneous measurements of neutron star masses and radii can be used to
constrain deviations from general relativity (GR) as was recently demonstrated
for the spontaneous scalarization model of Damour and Esposito-Far\`{e}se
(DEF). Here, we investigate the general applicability of the same procedure
beyond this single example. We first show that a simple variation of the DEF
model renders the same mass-radius measurements ineffective for obtaining
constraints. On the other hand, a recently popular and distinct model of
scalarization that arises in scalar-Gauss-Bonnet theory can be constrained
similarly to the original DEF model, albeit due to a slightly different
underlying mechanism. These establish that using the mass-radius data can
potentially constrain various theories of gravity, but the method also has
limitations.
| [
{
"created": "Fri, 3 Mar 2023 13:23:33 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jul 2023 16:17:16 GMT",
"version": "v2"
}
] | 2023-07-24 | [
[
"Demirboğa",
"Ekrem S.",
""
],
[
"Şahin",
"Yakup Emre",
""
],
[
"Ramazanoğlu",
"Fethi M.",
""
]
] | Simultaneous measurements of neutron star masses and radii can be used to constrain deviations from general relativity (GR) as was recently demonstrated for the spontaneous scalarization model of Damour and Esposito-Far\`{e}se (DEF). Here, we investigate the general applicability of the same procedure beyond this single example. We first show that a simple variation of the DEF model renders the same mass-radius measurements ineffective for obtaining constraints. On the other hand, a recently popular and distinct model of scalarization that arises in scalar-Gauss-Bonnet theory can be constrained similarly to the original DEF model, albeit due to a slightly different underlying mechanism. These establish that using the mass-radius data can potentially constrain various theories of gravity, but the method also has limitations. |
0707.1667 | Sergiu Vacaru I. | Sergiu I. Vacaru | Deformation Quantization of Nonholonomic Almost Kahler Models and
Einstein Gravity | latex 2e, 11pt, 15 pages, v4 accepted by Phys. Lett. A | Phys.Lett.A372:2949-2955,2008 | 10.1016/j.physleta.2008.01.044 | null | gr-qc hep-th math-ph math.MP math.SG | null | Nonholonomic distributions and adapted fame structures on (pseudo) Riemannian
manifolds of even dimension are employed to build structures equivalent to
almost Kahler geometry and which allows to perform a Fedosov-like quantization
of gravity. The nonlinear connection formalism that was formally elaborated for
Lagrange and Finsler geometry is implemented in classical and quantum Einstein
gravity.
| [
{
"created": "Wed, 11 Jul 2007 17:13:20 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jul 2007 17:45:11 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Jul 2007 20:23:25 GMT",
"version": "v3"
},
{
"created": "Thu, 10 Jan 2008 20:58:07 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Vacaru",
"Sergiu I.",
""
]
] | Nonholonomic distributions and adapted fame structures on (pseudo) Riemannian manifolds of even dimension are employed to build structures equivalent to almost Kahler geometry and which allows to perform a Fedosov-like quantization of gravity. The nonlinear connection formalism that was formally elaborated for Lagrange and Finsler geometry is implemented in classical and quantum Einstein gravity. |
gr-qc/0401022 | Luis Herrera | L.Herrera, G. Le Denmat, N.O. Santos and A. Wang | Shear-free radiating collapse and conformal flatness | 13 pages Latex. Some misprints in eqs.(17), (30) and (35) have been
corrected | Int.J.Mod.Phys.D13:583-592,2004 | 10.1142/S0218271804004840 | null | gr-qc astro-ph | null | Here we study some general properties of spherical shear-free collapse. Its
general solution when imposing conformal flatness is reobtained [1,2] and
matched to the outgoing Vaidya spacetime. We propose a simple model satisfying
these conditions and study its physical consequences. Special attention
deserve, the role played by relaxational processes and the conspicuous link
betweeen dissipation and density inhomogeneity.
| [
{
"created": "Wed, 7 Jan 2004 18:54:00 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2005 20:08:55 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Herrera",
"L.",
""
],
[
"Denmat",
"G. Le",
""
],
[
"Santos",
"N. O.",
""
],
[
"Wang",
"A.",
""
]
] | Here we study some general properties of spherical shear-free collapse. Its general solution when imposing conformal flatness is reobtained [1,2] and matched to the outgoing Vaidya spacetime. We propose a simple model satisfying these conditions and study its physical consequences. Special attention deserve, the role played by relaxational processes and the conspicuous link betweeen dissipation and density inhomogeneity. |
1501.05832 | David Ian Jones | D. I. Jones | Parameter choices and ranges for continuous gravitational wave searches
for steadily spinning neutron stars | Updated to match version accepted by MNRAS: One new equation
(equation 82)); typo (sign-error) corrected in equation (88); one more
paragraph inserted into Summary and Discussion section | null | 10.1093/mnras/stv1584 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the issue of selecting parameters and their associated ranges for
carrying out searches for continuous gravitational waves from steadily rotating
neutron stars. We consider three different cases (i) the "classic" case of a
star spinning about a principal axis; (ii) a biaxial star, not spinning about a
principal axis; (iii) a triaxial star spinning steady, but not about a
principal axis (as described in Jones, MNRAS vol 402, 2503 (2010)). The first
of these emits only at one frequency; the other two at a pair of harmonically
related frequencies. We show that in all three cases, when written in terms of
the original "source parameters", there exist a number of discrete
degeneracies, with different parameter values giving rise to the same
gravitational wave signal. We show how these can be removed by suitably
restricting the source parameter ranges. In the case of the model as written
down by Jones, there is also a continuous degeneracy. We show how to remove
this through a suitable rewriting in terms of "waveform parameters", chosen so
as to make the specialisations to the other stellar models particularly simple.
We briefly consider the (non-trivial) relation between the assignment of prior
probabilities on one set of parameters verses the other. The results of this
paper will be of use when designing strategies for carrying out searches for
such multi-harmonic gravitational wave signals, and when performing parameter
estimation in the event of a detection.
| [
{
"created": "Fri, 23 Jan 2015 15:32:14 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 2015 10:33:09 GMT",
"version": "v2"
}
] | 2015-08-19 | [
[
"Jones",
"D. I.",
""
]
] | We consider the issue of selecting parameters and their associated ranges for carrying out searches for continuous gravitational waves from steadily rotating neutron stars. We consider three different cases (i) the "classic" case of a star spinning about a principal axis; (ii) a biaxial star, not spinning about a principal axis; (iii) a triaxial star spinning steady, but not about a principal axis (as described in Jones, MNRAS vol 402, 2503 (2010)). The first of these emits only at one frequency; the other two at a pair of harmonically related frequencies. We show that in all three cases, when written in terms of the original "source parameters", there exist a number of discrete degeneracies, with different parameter values giving rise to the same gravitational wave signal. We show how these can be removed by suitably restricting the source parameter ranges. In the case of the model as written down by Jones, there is also a continuous degeneracy. We show how to remove this through a suitable rewriting in terms of "waveform parameters", chosen so as to make the specialisations to the other stellar models particularly simple. We briefly consider the (non-trivial) relation between the assignment of prior probabilities on one set of parameters verses the other. The results of this paper will be of use when designing strategies for carrying out searches for such multi-harmonic gravitational wave signals, and when performing parameter estimation in the event of a detection. |
gr-qc/0402017 | Gaetano Vilasi | Fabrizio Canfora and Gaetano Vilasi | Back Reaction from Trace Anomaly in RN-blackholes Evaporation | 16 pages Latex | JHEP 0312:055,2003 | 10.1088/1126-6708/2003/12/055 | null | gr-qc | null | A model is proposed to describe a transition from a charged black hole of
mass $M$ and charge $Q$ to one of mass $\bar{M}$ and charge $\bar{Q}$. The
basic equations are derived from the non-vacuum Einstein field equations
sourced by the Coulomb field and by a null scalar field with a nonvanishing
trace anomaly. It is shown that the nonvanishing trace of the energy-momentum
tensor prevents the formation of a naked singularity.
| [
{
"created": "Tue, 3 Feb 2004 21:14:44 GMT",
"version": "v1"
}
] | 2010-01-15 | [
[
"Canfora",
"Fabrizio",
""
],
[
"Vilasi",
"Gaetano",
""
]
] | A model is proposed to describe a transition from a charged black hole of mass $M$ and charge $Q$ to one of mass $\bar{M}$ and charge $\bar{Q}$. The basic equations are derived from the non-vacuum Einstein field equations sourced by the Coulomb field and by a null scalar field with a nonvanishing trace anomaly. It is shown that the nonvanishing trace of the energy-momentum tensor prevents the formation of a naked singularity. |
2407.19800 | Pankaj Sheoran | Tursunali Xamidov, Sanjar Shaymatov, Pankaj Sheoran and Bobomurat
Ahmedov | Astrophysical insights into magnetic Penrose process around
parameterized Konoplya-Rezzolla-Zhidenko black hole | 12 pages, 4 captioned figures and 2 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we investigate the parameterized Konoplya-Rezzolla-Zhidenko
(KRZ) black hole (BH) spacetime in the presence of an external asymptotically
uniform magnetic field. We first examine the innermost stable circular orbit
(ISCO) radii for both neutral and charged test particles, demonstrating that
the deformation parameters, $\delta_1$ and $\delta_2$, reduce the ISCO values.
Subsequently, we assess the energy efficiency of the magnetic Penrose process
(MPP) for an axially symmetric parameterized BH, analyzing the effects of the
deformation parameters and the magnetic field on the energy extraction process.
Our findings indicate that the rotational deformation parameter $\delta_2$ is
crucial for the efficiency of energy extraction from the BH. The synergy
between the rotational deformation parameter and the magnetic field
significantly boosts the energy extraction efficiency, with values exceeding
$100\%$. Interestingly, for extremal BHs with negative $\delta_2$ values, the
energy efficiency increases, in contrast to Kerr BHs where the MPP effect
diminishes. Additionally, we explore the astrophysical implications of the MPP
by deriving the maximum energy of a proton escaping from the KRZ parameterized
BH due to the beta decay of a free neutron near the horizon. Our results show
that negative $\delta_2$ values require stronger magnetic fields to achieve
equivalent energy levels for high-energy protons, providing deeper insights
into high-energy astrophysical phenomena around the parameterized BH.
| [
{
"created": "Mon, 29 Jul 2024 08:48:25 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Xamidov",
"Tursunali",
""
],
[
"Shaymatov",
"Sanjar",
""
],
[
"Sheoran",
"Pankaj",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] | In this study, we investigate the parameterized Konoplya-Rezzolla-Zhidenko (KRZ) black hole (BH) spacetime in the presence of an external asymptotically uniform magnetic field. We first examine the innermost stable circular orbit (ISCO) radii for both neutral and charged test particles, demonstrating that the deformation parameters, $\delta_1$ and $\delta_2$, reduce the ISCO values. Subsequently, we assess the energy efficiency of the magnetic Penrose process (MPP) for an axially symmetric parameterized BH, analyzing the effects of the deformation parameters and the magnetic field on the energy extraction process. Our findings indicate that the rotational deformation parameter $\delta_2$ is crucial for the efficiency of energy extraction from the BH. The synergy between the rotational deformation parameter and the magnetic field significantly boosts the energy extraction efficiency, with values exceeding $100\%$. Interestingly, for extremal BHs with negative $\delta_2$ values, the energy efficiency increases, in contrast to Kerr BHs where the MPP effect diminishes. Additionally, we explore the astrophysical implications of the MPP by deriving the maximum energy of a proton escaping from the KRZ parameterized BH due to the beta decay of a free neutron near the horizon. Our results show that negative $\delta_2$ values require stronger magnetic fields to achieve equivalent energy levels for high-energy protons, providing deeper insights into high-energy astrophysical phenomena around the parameterized BH. |
gr-qc/0403096 | Hernando Quevedo | Hernando Quevedo and Ruben D. Zarate | Reply to the Comment ``On the thermodynamics of inhomogeneous perfect
fluid mixtures'' | null | null | null | null | gr-qc | null | We show that the analysis presented in a recent comment by Coll and Ferrando
\cite{comment} (qr-qc/0312058) is based on the erroneous assumption that the
chemical potential and fractional concentration of a {\it mixture} of perfect
fluids are unknown variables.
| [
{
"created": "Tue, 23 Mar 2004 21:00:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Quevedo",
"Hernando",
""
],
[
"Zarate",
"Ruben D.",
""
]
] | We show that the analysis presented in a recent comment by Coll and Ferrando \cite{comment} (qr-qc/0312058) is based on the erroneous assumption that the chemical potential and fractional concentration of a {\it mixture} of perfect fluids are unknown variables. |
1802.03672 | Phongpichit Channuie | Phongpichit Channuie (Walailak U.), Davood Momeni (Sultan Qaboos U.) | On the Scalar-Vector-Tensor Gravity: Black Hole, Thermodynamics and
Geometrothermodynamics | v2: 8 pages, 4 figures, texts modified and references added, version
accepted by Physics Letters B | Physics Letters B785 (2018) 309-314 | 10.1016/j.physletb.2018.08.052 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a new class of modified gravity theories formulated via an
additional scalar and vector field on top of the standard tensor field has been
proposed. The direct implications of these theories are expected to be relevant
for cosmology and astrophysics. In the present work, we revisit the modified
framework of the scalar-vector-tensor theories of gravity. Surprisingly, we
discover novel metric function for the black hole solutions. We also
investigate the semi-classical thermodynamics of the black holes and study the
thermodynamic properties of the obtained solutions. Moreover, we quantify the
entropy and the temperature of the new black hole and also calculate the heat
capacity. Finally, we also apply the formalism of the geometrothermodynamics to
examine thermodynamic properties of the new black hole. This formalism yields
results consistent with those obtained from the usual thermodynamic
implementation.
| [
{
"created": "Sun, 11 Feb 2018 01:00:57 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Aug 2018 14:00:26 GMT",
"version": "v2"
}
] | 2018-09-11 | [
[
"Channuie",
"Phongpichit",
"",
"Walailak U."
],
[
"Momeni",
"Davood",
"",
"Sultan Qaboos U."
]
] | Recently, a new class of modified gravity theories formulated via an additional scalar and vector field on top of the standard tensor field has been proposed. The direct implications of these theories are expected to be relevant for cosmology and astrophysics. In the present work, we revisit the modified framework of the scalar-vector-tensor theories of gravity. Surprisingly, we discover novel metric function for the black hole solutions. We also investigate the semi-classical thermodynamics of the black holes and study the thermodynamic properties of the obtained solutions. Moreover, we quantify the entropy and the temperature of the new black hole and also calculate the heat capacity. Finally, we also apply the formalism of the geometrothermodynamics to examine thermodynamic properties of the new black hole. This formalism yields results consistent with those obtained from the usual thermodynamic implementation. |
1812.06988 | Francois Foucart | Francois Foucart, Matthew D. Duez, Tanja Hinderer, Jesus Caro, Andrew
R. Williamson, Michael Boyle, Alessandra Buonanno, Roland Haas, Daniel A.
Hemberger, Lawrence E. Kidder, Harald P. Pfeiffer, Mark A. Scheel | Gravitational waveforms from SpEC simulations : neutron star-neutron
star and low-mass black hole-neutron star binaries | 17p, 10 figures | Phys. Rev. D 99, 044008 (2019) | 10.1103/PhysRevD.99.044008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waveforms from numerical simulations are a critical tool to
test and analytically calibrate the waveform models used to study the
properties of merging compact objects. In this paper, we present a series of
high-accuracy waveforms produced with the SpEC code for systems involving at
least one neutron star. We provide for the first time waveforms with sub-radian
accuracy over more than twenty cycles for low-mass black hole-neutron star
binaries, including binaries with non-spinning objects, and binaries with
rapidly spinning neutron stars that maximize the impact on the gravitational
wave signal of the near-resonant growth of the fundamental excitation mode of
the neutron star (f-mode). We also provide for the first time with SpEC a
high-accuracy neutron star-neutron star waveform. These waveforms are made
publicly available as part of the SxS catalogue. We compare our results to
analytical waveform models currently implemented in data analysis pipelines.
For most simulations, the models lie outside of the predicted numerical errors
in the last few orbits before merger, but do not show systematic deviations
from the numerical results: comparing different models appears to provide
reasonable estimates of the modeling errors. The sole exception is the
equal-mass simulation using a rapidly counter-rotating neutron star to maximize
the impact of the excitation of the f-mode, for which all models perform
poorly. This is however expected, as even the single model that takes f-mode
excitation into account ignores the significant impact of the neutron star spin
on the f-mode excitation frequency.
| [
{
"created": "Mon, 17 Dec 2018 19:00:04 GMT",
"version": "v1"
}
] | 2019-02-20 | [
[
"Foucart",
"Francois",
""
],
[
"Duez",
"Matthew D.",
""
],
[
"Hinderer",
"Tanja",
""
],
[
"Caro",
"Jesus",
""
],
[
"Williamson",
"Andrew R.",
""
],
[
"Boyle",
"Michael",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Haas",
"Roland",
""
],
[
"Hemberger",
"Daniel A.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
]
] | Gravitational waveforms from numerical simulations are a critical tool to test and analytically calibrate the waveform models used to study the properties of merging compact objects. In this paper, we present a series of high-accuracy waveforms produced with the SpEC code for systems involving at least one neutron star. We provide for the first time waveforms with sub-radian accuracy over more than twenty cycles for low-mass black hole-neutron star binaries, including binaries with non-spinning objects, and binaries with rapidly spinning neutron stars that maximize the impact on the gravitational wave signal of the near-resonant growth of the fundamental excitation mode of the neutron star (f-mode). We also provide for the first time with SpEC a high-accuracy neutron star-neutron star waveform. These waveforms are made publicly available as part of the SxS catalogue. We compare our results to analytical waveform models currently implemented in data analysis pipelines. For most simulations, the models lie outside of the predicted numerical errors in the last few orbits before merger, but do not show systematic deviations from the numerical results: comparing different models appears to provide reasonable estimates of the modeling errors. The sole exception is the equal-mass simulation using a rapidly counter-rotating neutron star to maximize the impact of the excitation of the f-mode, for which all models perform poorly. This is however expected, as even the single model that takes f-mode excitation into account ignores the significant impact of the neutron star spin on the f-mode excitation frequency. |
0710.0477 | Hideki Asada | Hideki Asada | Gravitational time delay of light for various models of modified gravity | 10 pages, 2 figures; title, abstract and text improved; accepted for
publication in Phys. Lett. B | Phys.Lett.B661:78-81,2008 | 10.1016/j.physletb.2008.02.006 | null | gr-qc astro-ph hep-th | null | We reexamined the gravitational time delay of light, allowing for various
models of modified gravity. We clarify the dependence of the time delay (and
induced frequency shift) on modified gravity models and investigate how to
distinguish those models, when light propagates in static spherically symmetric
spacetimes. Thus experiments by radio signal from spacecrafts at very different
distances from Sun and future space-borne laser interferometric detectors could
be a probe of modified gravity in the solar system.
| [
{
"created": "Tue, 2 Oct 2007 09:41:07 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Feb 2008 08:40:48 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Asada",
"Hideki",
""
]
] | We reexamined the gravitational time delay of light, allowing for various models of modified gravity. We clarify the dependence of the time delay (and induced frequency shift) on modified gravity models and investigate how to distinguish those models, when light propagates in static spherically symmetric spacetimes. Thus experiments by radio signal from spacecrafts at very different distances from Sun and future space-borne laser interferometric detectors could be a probe of modified gravity in the solar system. |
1602.07006 | Elias Okon | Elias Okon and Daniel Sudarsky | A (not so?) novel explanation for the very special initial state of the
universe | 12 pages; improved and extended version | null | 10.1088/0264-9381/33/22/225015 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We put forward a proposal that combines objective collapse models, developed
in connection with quantum-foundational questions, with the so-called Weyl
curvature hypothesis, introduced by Roger Penrose as an attempt to account for
the very special initial state of the universe. In particular, we explain how a
curvature dependence of the collapse rate in such models, an idea already shown
to help in the context of black holes and information loss, could also offer a
dynamical justification for Penrose's conjecture.
| [
{
"created": "Tue, 23 Feb 2016 01:20:46 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Apr 2016 18:30:49 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Jun 2016 19:23:39 GMT",
"version": "v3"
}
] | 2016-11-23 | [
[
"Okon",
"Elias",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | We put forward a proposal that combines objective collapse models, developed in connection with quantum-foundational questions, with the so-called Weyl curvature hypothesis, introduced by Roger Penrose as an attempt to account for the very special initial state of the universe. In particular, we explain how a curvature dependence of the collapse rate in such models, an idea already shown to help in the context of black holes and information loss, could also offer a dynamical justification for Penrose's conjecture. |
0904.2330 | Mauro Rinaldelli | E. Minguzzi and M. Rinaldelli | Widening the light cones on subsets of spacetime: some variations to
stable causality | Latex2e, 19 pages, 1 table, 1 figure | Class.Quant.Grav.26:175004,2009 | 10.1088/0264-9381/26/17/175004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By definition a spacetime is stably causal if it is possible to widen the
light cones all over the spacetime without spoiling causality. We prove that if
the spacetime is at least non-total imprisoning then it is stably causal
provided the light cones can be widened outside any compact arbitrarily large
set, i.e. in a neighborhood of infinity, without spoiling causality.
Furthermore, we prove that the new causality level `compact stable causality'
can be obtained as the antisymmetry condition of a new causal relation which we
identify, but it cannot be obtained as a causal stability condition with
respect to a topology on metrics. The difference between stable causality and
compact stable causality is shown to follow from the fact that Geroch's
interval topology on the space of conformal metrics of M is not Frechet-Urysohn
(in fact it is not even T-sequential). In particular we prove that (compact)
stably causal metrics are those in the (sequential) interior of the set of
chronological metrics. Finally, contrary to previous claims it is shown that
stable causality with respect to the C^0 fine topology on metrics leads to the
usual notion of stable causality.
| [
{
"created": "Wed, 15 Apr 2009 14:38:32 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 2009 15:38:26 GMT",
"version": "v2"
}
] | 2009-08-12 | [
[
"Minguzzi",
"E.",
""
],
[
"Rinaldelli",
"M.",
""
]
] | By definition a spacetime is stably causal if it is possible to widen the light cones all over the spacetime without spoiling causality. We prove that if the spacetime is at least non-total imprisoning then it is stably causal provided the light cones can be widened outside any compact arbitrarily large set, i.e. in a neighborhood of infinity, without spoiling causality. Furthermore, we prove that the new causality level `compact stable causality' can be obtained as the antisymmetry condition of a new causal relation which we identify, but it cannot be obtained as a causal stability condition with respect to a topology on metrics. The difference between stable causality and compact stable causality is shown to follow from the fact that Geroch's interval topology on the space of conformal metrics of M is not Frechet-Urysohn (in fact it is not even T-sequential). In particular we prove that (compact) stably causal metrics are those in the (sequential) interior of the set of chronological metrics. Finally, contrary to previous claims it is shown that stable causality with respect to the C^0 fine topology on metrics leads to the usual notion of stable causality. |
0907.4103 | Eugeny Babichev | E. Babichev, C. Deffayet, R. Ziour | Recovering General Relativity from massive gravity | 4 pages, 3 figures; v2: minor changes, matches published version | Phys.Rev.Lett.103:201102,2009 | 10.1103/PhysRevLett.103.201102 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain static, spherically symmetric, and asymptotically flat numerical
solutions of massive gravity with a source. Those solutions show, for the first
time explicitly, a recovery of the Schwarzschild solution of General Relativity
via the so-called Vainshtein mechanism.
| [
{
"created": "Thu, 23 Jul 2009 15:58:24 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2009 14:31:43 GMT",
"version": "v2"
}
] | 2010-04-23 | [
[
"Babichev",
"E.",
""
],
[
"Deffayet",
"C.",
""
],
[
"Ziour",
"R.",
""
]
] | We obtain static, spherically symmetric, and asymptotically flat numerical solutions of massive gravity with a source. Those solutions show, for the first time explicitly, a recovery of the Schwarzschild solution of General Relativity via the so-called Vainshtein mechanism. |
2107.00393 | Alesandro Santos | J. S. Gon\c{c}alves and A. F. Santos | G\"{o}del-type solutions in hybrid metric-Palatini gravity | 14 pages, accepted for publication in EPL | null | 10.1209/0295-5075/ac0ffd | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, the hybrid metric-Palatini gravity is an approach to modified
gravity in which is added to the usual Einstein-Hilbert action a supplementary
term containing a Palatini-type correction of the form $f({\cal R},T)$. Here,
${\cal R}$ is the Palatini curvature scalar, which is constructed from an
independent connection and $T$ is the trace of the energy-momentum tensor. This
theory describes a non-minimal coupling between matter and geometry. The
modified Einstein field equations in this hybrid metric-Palatini approach are
obtained. Then, it is investigated whether this modified theory of gravity and
its field equations allow G\"{o}del-type solutions, which essentially lead to
violation of causality. Considering physically well-motivated matter sources,
causal and non-causal solutions are explored.
| [
{
"created": "Thu, 1 Jul 2021 12:12:10 GMT",
"version": "v1"
}
] | 2022-03-30 | [
[
"Gonçalves",
"J. S.",
""
],
[
"Santos",
"A. F.",
""
]
] | In this paper, the hybrid metric-Palatini gravity is an approach to modified gravity in which is added to the usual Einstein-Hilbert action a supplementary term containing a Palatini-type correction of the form $f({\cal R},T)$. Here, ${\cal R}$ is the Palatini curvature scalar, which is constructed from an independent connection and $T$ is the trace of the energy-momentum tensor. This theory describes a non-minimal coupling between matter and geometry. The modified Einstein field equations in this hybrid metric-Palatini approach are obtained. Then, it is investigated whether this modified theory of gravity and its field equations allow G\"{o}del-type solutions, which essentially lead to violation of causality. Considering physically well-motivated matter sources, causal and non-causal solutions are explored. |
1904.02247 | Madhavan Varadarajan | Madhavan Varadarajan | On quantum propagation in Smolin's weak coupling limit of 4d Euclidean
Gravity | 38 pages, 9 figures | Phys. Rev. D 100, 066018 (2019) | 10.1103/PhysRevD.100.066018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two desireable properties of a quantum dynamics for Loop Quantum Gravity
(LQG) are that its generators provide an anomaly free representation of the
classical constraint algebra and that physical states which lie in the kernel
of these generators encode propagation. A physical state in LQG is expected to
be a sum over graphical $SU(2)$ spin network states. By propagation we mean
that a quantum perturbation at one vertex of a spin network state propagates to
vertices which are `many links away' thus yielding a new spin network state
which is related to the old one by this propagation. A physical state encodes
propagation if its spin network summands are related by propagation. Here we
study propagation in an LQG quantization of Smolin's weak coupling limit of
Euclidean Gravity based on graphical $U(1)^3$ `charge' network states. Building
on our earlier work on anomaly free quantum constraint actions for this system,
we analyse the extent to which physical states encode propagation. In
particular, we show that a slight modification of the constraint actions
constructed in our previous work leads to physical states which encode robust
propagation. Under appropriate conditions, this propagation merges, seperates
and entangles vertices of charge network states. The `electric' diffeomorphism
constraints introduced in prevous work play a key role in our considerations.
The main import of our work is that there are choices of quantum constraint
constructions through LQG methods which are consistent with vigorous
propagation thus providing a counterpoint to Smolin's early observations on the
difficulties of propagation in the context of LQG type operator constructions.
Whether the choices considered in this work are physically appropriate is an
open question worthy of further study.
| [
{
"created": "Wed, 3 Apr 2019 21:42:25 GMT",
"version": "v1"
}
] | 2019-09-25 | [
[
"Varadarajan",
"Madhavan",
""
]
] | Two desireable properties of a quantum dynamics for Loop Quantum Gravity (LQG) are that its generators provide an anomaly free representation of the classical constraint algebra and that physical states which lie in the kernel of these generators encode propagation. A physical state in LQG is expected to be a sum over graphical $SU(2)$ spin network states. By propagation we mean that a quantum perturbation at one vertex of a spin network state propagates to vertices which are `many links away' thus yielding a new spin network state which is related to the old one by this propagation. A physical state encodes propagation if its spin network summands are related by propagation. Here we study propagation in an LQG quantization of Smolin's weak coupling limit of Euclidean Gravity based on graphical $U(1)^3$ `charge' network states. Building on our earlier work on anomaly free quantum constraint actions for this system, we analyse the extent to which physical states encode propagation. In particular, we show that a slight modification of the constraint actions constructed in our previous work leads to physical states which encode robust propagation. Under appropriate conditions, this propagation merges, seperates and entangles vertices of charge network states. The `electric' diffeomorphism constraints introduced in prevous work play a key role in our considerations. The main import of our work is that there are choices of quantum constraint constructions through LQG methods which are consistent with vigorous propagation thus providing a counterpoint to Smolin's early observations on the difficulties of propagation in the context of LQG type operator constructions. Whether the choices considered in this work are physically appropriate is an open question worthy of further study. |
gr-qc/9312020 | Jose Rubio | J.A. Rubio and R.P. Woodard | Reduced Hamiltonians | 80 pages, Univesity of Florida preprint UFIFT-93-20 | Class.Quant.Grav.11:2253-2281,1994 | 10.1088/0264-9381/11/9/009 | null | gr-qc | null | We resurrect a standard construction of analytical mechanics dating from the
last century. The technique allows one to pass from any dynamical system whose
first order evolution equations are known, and whose bracket algebra is not
degenerate, to a system of canonical variables and a non-zero Hamiltonian that
generates their evolution. We advocate using this method to infer a canonical
formalism, as a prelude to quantization, for systems in which the naive
Hamiltonian is constrained to vanish. The construction agrees with the usual
results for gauge theories and can be applied as well to gravity, {\it even
when the spatial manifold is closed.} As an example, we construct such a
reduced Hamiltonian in perturbation theory around a flat background on the
manifold $T^3 \times R$. The resulting Hamiltonian is positive semidefinite and
agrees with the A.D.M. energy in the limit that deviations from flat space
remain localized as the toroidal radii become infinite.
| [
{
"created": "Mon, 13 Dec 1993 13:45:02 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Rubio",
"J. A.",
""
],
[
"Woodard",
"R. P.",
""
]
] | We resurrect a standard construction of analytical mechanics dating from the last century. The technique allows one to pass from any dynamical system whose first order evolution equations are known, and whose bracket algebra is not degenerate, to a system of canonical variables and a non-zero Hamiltonian that generates their evolution. We advocate using this method to infer a canonical formalism, as a prelude to quantization, for systems in which the naive Hamiltonian is constrained to vanish. The construction agrees with the usual results for gauge theories and can be applied as well to gravity, {\it even when the spatial manifold is closed.} As an example, we construct such a reduced Hamiltonian in perturbation theory around a flat background on the manifold $T^3 \times R$. The resulting Hamiltonian is positive semidefinite and agrees with the A.D.M. energy in the limit that deviations from flat space remain localized as the toroidal radii become infinite. |
gr-qc/0411115 | Kerstin E. Kunze | Kerstin E. Kunze | Asymptotic behaviour of curvature and matter in the Penrose limit | 12 pages | null | 10.1103/PhysRevD.71.063518 | null | gr-qc hep-th | null | The asymptotic behaviour of the components of the Weyl tensor and of the
energy-momentum tensor in the Penrose limit is determined. In both cases a
peeling-off property is found. Examples of different types of matter are
provided. The expansion and shear of the congruence of null geodesics along
which the Penrose limit is taken are determined. Finally, the approach to the
singularity in the Penrose limit of cosmological space-times is discussed.
| [
{
"created": "Wed, 24 Nov 2004 16:16:59 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Kunze",
"Kerstin E.",
""
]
] | The asymptotic behaviour of the components of the Weyl tensor and of the energy-momentum tensor in the Penrose limit is determined. In both cases a peeling-off property is found. Examples of different types of matter are provided. The expansion and shear of the congruence of null geodesics along which the Penrose limit is taken are determined. Finally, the approach to the singularity in the Penrose limit of cosmological space-times is discussed. |
gr-qc/9704048 | Bill Pezzaglia | William M. Pezzaglia Jr. and John J. Adams | Should Metric Signature Matter in Clifford Algebra Formulations of
Physical Theories? | 12 pages, latex, no figures, Summary of talk at the Special Session
on Octonions and Clifford Algebras Algebras, at the 1997 Spring Western
Sectional Meeting of the American Mathematical Society, Oregon State
University, Corvallis, OR, 19-20 April 1997.
ftp://www.clifford.org/clf-alg/preprints/1995/pezz9502.latex | null | null | clf-alg/pezz9502 | gr-qc quant-ph | null | Standard formulation is unable to distinguish between the (+++-) and (---+)
spacetime metric signatures. However, the Clifford algebras associated with
each are inequivalent, R(4) in the first case (real 4 by 4 matrices), H(2) in
the latter (quaternionic 2 by 2). Multivector reformulations of Dirac theory by
various authors look quite inequivalent pending the algebra assumed. It is not
clear if this is mere artifact, or if there is a right/wrong choice as to which
one describes reality. However, recently it has been shown that one can map
from one signature to the other using a "tilt transformation" [see P. Lounesto,
"Clifford Algebras and Hestenes Spinors", Found. Phys. 23, 1203-1237 (1993)].
The broader question is that if the universe is signature blind, then perhaps a
complete theory should be manifestly tilt covariant. A generalized multivector
wave equation is proposed which is fully signature invariant in form, because
it includes all the components of the algebra in the wavefunction (instead of
restricting it to half) as well as all the possibilities for interaction terms.
| [
{
"created": "Thu, 17 Apr 1997 08:20:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pezzaglia",
"William M.",
"Jr."
],
[
"Adams",
"John J.",
""
]
] | Standard formulation is unable to distinguish between the (+++-) and (---+) spacetime metric signatures. However, the Clifford algebras associated with each are inequivalent, R(4) in the first case (real 4 by 4 matrices), H(2) in the latter (quaternionic 2 by 2). Multivector reformulations of Dirac theory by various authors look quite inequivalent pending the algebra assumed. It is not clear if this is mere artifact, or if there is a right/wrong choice as to which one describes reality. However, recently it has been shown that one can map from one signature to the other using a "tilt transformation" [see P. Lounesto, "Clifford Algebras and Hestenes Spinors", Found. Phys. 23, 1203-1237 (1993)]. The broader question is that if the universe is signature blind, then perhaps a complete theory should be manifestly tilt covariant. A generalized multivector wave equation is proposed which is fully signature invariant in form, because it includes all the components of the algebra in the wavefunction (instead of restricting it to half) as well as all the possibilities for interaction terms. |
gr-qc/0203058 | Alejandro Perez | Alejandro Perez | Spin foam quantization of SO(4) Plebanski's action | Main conclusions in first part changed due to correction in the
derivation | Adv.Theor.Math.Phys. 5 (2002) 947-968;
Erratum-Adv.Theor.Math.Phys. 6 (2003) 593-595 | null | CGPG-02/03-1 | gr-qc hep-th | null | The goal of this work is two-fold. In the first part of this paper we regard
classical Plebanski's action as a BF action supplemented by constraints. We
introduce a spin foam model for Riemannian general relativity by systematically
implementing these constraints as restrictions on paths in the state-sum of the
BF theory. The spin foam model obtained is precisely the Barrett-Crane model.
This provides a clear-cut connection of the model with a simplicial action.
In the second part of the paper we study the quantization of the effective
action corresponding to the degenerate sectors of Plebanski's theory and obtain
a very simple spin foam model. This model turns out to be precisely the one
introduced by De Pietri et al. as an alternative to the one proposed by Barrett
and Crane.
| [
{
"created": "Fri, 15 Mar 2002 18:53:13 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Mar 2002 20:22:20 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Sep 2002 22:57:52 GMT",
"version": "v3"
},
{
"created": "Sat, 19 Oct 2002 22:24:53 GMT",
"version": "v4"
},
{
"created": "Thu, 21 Nov 2002 03:42:09 GMT",
"version": "v5"
}
] | 2009-03-20 | [
[
"Perez",
"Alejandro",
""
]
] | The goal of this work is two-fold. In the first part of this paper we regard classical Plebanski's action as a BF action supplemented by constraints. We introduce a spin foam model for Riemannian general relativity by systematically implementing these constraints as restrictions on paths in the state-sum of the BF theory. The spin foam model obtained is precisely the Barrett-Crane model. This provides a clear-cut connection of the model with a simplicial action. In the second part of the paper we study the quantization of the effective action corresponding to the degenerate sectors of Plebanski's theory and obtain a very simple spin foam model. This model turns out to be precisely the one introduced by De Pietri et al. as an alternative to the one proposed by Barrett and Crane. |
gr-qc/0412010 | Francois Limousin | Dorota Gondek-Rosinska (LUTH, CAMK), Michal Bejger (CAMK), Tomek Bulik
(CAMK), Eric Gourgoulhon (LUTH), Pawel Haensel (LUTH, CAMK), Francois
Limousin (LUTH), Keisuke Taniguchi, Leszek Zdunik (CAMK) | The final phase of inspiral of neutron stars: realistic equations of
state | 6 pages, 2 figures, Advances in Space Research, in
press,doi:10.1016/j.asr.2006.09.021, available online www.sciencedirect.com,
paper updated according to the reviewer's suggestions (conclusions unchanged) | Adv.SpaceRes.39:271-274,2007 | 10.1016/j.asr.2006.09.021 | null | gr-qc | null | Coalescing compact star binaries are expected to be among the strongest
sources of gravitational radiation to be seen by laser interferometers. We
present calculations of the final phase of inspiral of equal mass irrotational
neutron star binaries and strange quark star binaries. Six types of equations
of state at zero temperature are used - three realistic nuclear equations of
state of various softness and three different MIT bag models of strange quark
matter. We study the precoalescing stage within the Isenberg-Wilson-Mathews
approximation of general relativity using a multidomain spectral method. The
gravitational-radiation driven evolution of the binary system is approximated
by a sequence of quasi-equilibrium configurations at fixed baryon number and
decreasing separation. We find that the innermost stable circular orbit (ISCO)
is given by an orbital instability for binary strange quark stars and by the
mass-shedding limit for neutron star binaries. The gravitational wave frequency
at the ISCO, which marks the end of the inspiral phase, is found to be around
1100-1460 Hz for two 1.35 solar masses irrotational strange stars described by
the MIT bag model and between 800 Hz and 1230 Hz for neutron stars.
| [
{
"created": "Thu, 2 Dec 2004 21:33:42 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jan 2007 07:51:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gondek-Rosinska",
"Dorota",
"",
"LUTH, CAMK"
],
[
"Bejger",
"Michal",
"",
"CAMK"
],
[
"Bulik",
"Tomek",
"",
"CAMK"
],
[
"Gourgoulhon",
"Eric",
"",
"LUTH"
],
[
"Haensel",
"Pawel",
"",
"LUTH, CAMK"
],
[
"Limousin",
"Francois",
"",
"LUTH"
],
[
"Taniguchi",
"Keisuke",
"",
"CAMK"
],
[
"Zdunik",
"Leszek",
"",
"CAMK"
]
] | Coalescing compact star binaries are expected to be among the strongest sources of gravitational radiation to be seen by laser interferometers. We present calculations of the final phase of inspiral of equal mass irrotational neutron star binaries and strange quark star binaries. Six types of equations of state at zero temperature are used - three realistic nuclear equations of state of various softness and three different MIT bag models of strange quark matter. We study the precoalescing stage within the Isenberg-Wilson-Mathews approximation of general relativity using a multidomain spectral method. The gravitational-radiation driven evolution of the binary system is approximated by a sequence of quasi-equilibrium configurations at fixed baryon number and decreasing separation. We find that the innermost stable circular orbit (ISCO) is given by an orbital instability for binary strange quark stars and by the mass-shedding limit for neutron star binaries. The gravitational wave frequency at the ISCO, which marks the end of the inspiral phase, is found to be around 1100-1460 Hz for two 1.35 solar masses irrotational strange stars described by the MIT bag model and between 800 Hz and 1230 Hz for neutron stars. |
gr-qc/9911082 | Laszlo A. Gergely | L\'aszl\'o \'A. Gergely | Spin-spin effects in radiating compact binaries | 12 pages, to appear in Phys. Rev. D | Phys.Rev. D61 (2000) 024035 | 10.1103/PhysRevD.61.024035 | null | gr-qc | null | The dynamics of a binary system with two spinning components on an eccentric
orbit is studied, with the inclusion of the spin-spin interaction terms
appearing at the second post-Newtonian order. A generalized true anomaly
parametrization properly describes the radial component of the motion. The
average over one radial period of the magnitude of the orbital angular momentum
$\bar{L}$ is found to have no nonradiative secular change. All spin-spin terms
in the secular radiative loss of the energy and magnitude of orbital angular
momentum are given in terms of $\bar{L}$ and other constants of the motion.
Among them, self-interaction spin effects are found, representing the second
post-Newtonian correction to the 3/2 post-Newtonian order Lense-Thirring
approximation.
| [
{
"created": "Mon, 22 Nov 1999 14:02:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gergely",
"László Á.",
""
]
] | The dynamics of a binary system with two spinning components on an eccentric orbit is studied, with the inclusion of the spin-spin interaction terms appearing at the second post-Newtonian order. A generalized true anomaly parametrization properly describes the radial component of the motion. The average over one radial period of the magnitude of the orbital angular momentum $\bar{L}$ is found to have no nonradiative secular change. All spin-spin terms in the secular radiative loss of the energy and magnitude of orbital angular momentum are given in terms of $\bar{L}$ and other constants of the motion. Among them, self-interaction spin effects are found, representing the second post-Newtonian correction to the 3/2 post-Newtonian order Lense-Thirring approximation. |
0802.4063 | Jerzy Matyjasek | Jerzy Matyjasek | Entropy of nonlinear black holes in quadratic gravity | null | ActaPhys.Polon.B39:3-22,2008 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Employing the Noether charge technique and Visser's Euclidean approach the
entropy of the nonlinear black hole described by the perturbative solution of
the system of coupled equations of the quadratic gravity and nonlinear
electrodynamics is constructed. The solution is parametrized by the exact
location of the event horizon and charge. Special emphasis in put on the
extremal configuration. Consequences of the second choice of the boundary
conditions, in which the solution is paramerized by the charge and the total
mass as seen by a distant observer is briefly examined.
| [
{
"created": "Wed, 27 Feb 2008 18:22:07 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Matyjasek",
"Jerzy",
""
]
] | Employing the Noether charge technique and Visser's Euclidean approach the entropy of the nonlinear black hole described by the perturbative solution of the system of coupled equations of the quadratic gravity and nonlinear electrodynamics is constructed. The solution is parametrized by the exact location of the event horizon and charge. Special emphasis in put on the extremal configuration. Consequences of the second choice of the boundary conditions, in which the solution is paramerized by the charge and the total mass as seen by a distant observer is briefly examined. |
gr-qc/9907053 | Andrew P. Bilyard | A. P. Billyard (1), A. A. Coley (1), R. J. van den Hoogen (2), J.
Ibanez (3) and I. Olasagasti (3) ((1) Dalhousie University, (2) Saint Francis
Xavier University, (3) Universidad del Pais Vasco) | Scalar Field Cosmologies with Barotropic Matter: Models of Bianchi class
B | 18 pages, 1 figure, uses revtex and epsf to insert figure | Class.Quant.Grav.16:4035-4056,1999 | 10.1088/0264-9381/16/12/320 | DAL-99-6a | gr-qc | null | We investigate in detail the qualitative behaviour of the class of Bianchi
type B spatially homogeneous cosmological models in which the matter content is
composed of two non-interacting components; the first component is described by
a barotropic fluid having a gamma-law equation of state, whilst the second is a
non-interacting scalar field (phi) with an exponential potential V=Lambda exp(k
phi). In particular, we study the asymptotic properties of the models both at
early and late times, paying particular attention on whether the models
isotropize (and inflate) to the future, and we discuss the genericity of the
cosmological scaling solutions.
| [
{
"created": "Thu, 15 Jul 1999 16:53:37 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Billyard",
"A. P.",
""
],
[
"Coley",
"A. A.",
""
],
[
"Hoogen",
"R. J. van den",
""
],
[
"Ibanez",
"J.",
""
],
[
"Olasagasti",
"I.",
""
]
] | We investigate in detail the qualitative behaviour of the class of Bianchi type B spatially homogeneous cosmological models in which the matter content is composed of two non-interacting components; the first component is described by a barotropic fluid having a gamma-law equation of state, whilst the second is a non-interacting scalar field (phi) with an exponential potential V=Lambda exp(k phi). In particular, we study the asymptotic properties of the models both at early and late times, paying particular attention on whether the models isotropize (and inflate) to the future, and we discuss the genericity of the cosmological scaling solutions. |
gr-qc/0611019 | Andrea Fuster | A. Coley, A. Fuster, S. Hervik and N. Pelavas | Higher dimensional VSI spacetimes | 14 pages, changes in second paragraph of the discussion | Class.Quant.Grav.23:7431-7444,2006 | 10.1088/0264-9381/23/24/014 | NIKHEF/2006-008 | gr-qc hep-th | null | We present the explicit metric forms for higher dimensional vanishing scalar
invariant (VSI) Lorentzian spacetimes. We note that all of the VSI spacetimes
belong to the higher dimensional Kundt class. We determine all of the VSI
spacetimes which admit a covariantly constant null vector, and we note that in
general in higher dimensions these spacetimes are of Ricci type III and Weyl
type III. The Ricci type N subclass is related to the chiral null models and
includes the relativistic gyratons and the higher dimensional pp-wave
spacetimes. The spacetimes under investigation are of particular interest since
they are solutions of supergravity or superstring theory.
| [
{
"created": "Fri, 3 Nov 2006 10:38:27 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Dec 2006 10:07:03 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Coley",
"A.",
""
],
[
"Fuster",
"A.",
""
],
[
"Hervik",
"S.",
""
],
[
"Pelavas",
"N.",
""
]
] | We present the explicit metric forms for higher dimensional vanishing scalar invariant (VSI) Lorentzian spacetimes. We note that all of the VSI spacetimes belong to the higher dimensional Kundt class. We determine all of the VSI spacetimes which admit a covariantly constant null vector, and we note that in general in higher dimensions these spacetimes are of Ricci type III and Weyl type III. The Ricci type N subclass is related to the chiral null models and includes the relativistic gyratons and the higher dimensional pp-wave spacetimes. The spacetimes under investigation are of particular interest since they are solutions of supergravity or superstring theory. |
gr-qc/0112008 | Christiane Lechner | Christiane Lechner, Jonathan Thornburg, Sascha Husa, and Peter C.
Aichelburg | A New Transition between Discrete and Continuous Self-Similarity in
Critical Gravitational Collapse | 4 pages, 5 figures, uses REVTeX | Phys.Rev. D65 (2002) 081501 | 10.1103/PhysRevD.65.081501 | UWThPh-2001-49 | gr-qc | null | We analyze a bifurcation phenomenon associated with critical gravitational
collapse in a family of self-gravitating SU(2) $\sigma$-models. As the
dimensionless coupling constant decreases, the critical solution changes from
discretely self-similar (DSS) to continuously self-similar (CSS). Numerical
results provide evidence for a bifurcation which is analogous to a heteroclinic
loop bifurcation in dynamical systems, where two fixed points (CSS) collide
with a limit cycle (DSS) in phase space as the coupling constant tends to a
critical value.
| [
{
"created": "Fri, 7 Dec 2001 13:19:01 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Lechner",
"Christiane",
""
],
[
"Thornburg",
"Jonathan",
""
],
[
"Husa",
"Sascha",
""
],
[
"Aichelburg",
"Peter C.",
""
]
] | We analyze a bifurcation phenomenon associated with critical gravitational collapse in a family of self-gravitating SU(2) $\sigma$-models. As the dimensionless coupling constant decreases, the critical solution changes from discretely self-similar (DSS) to continuously self-similar (CSS). Numerical results provide evidence for a bifurcation which is analogous to a heteroclinic loop bifurcation in dynamical systems, where two fixed points (CSS) collide with a limit cycle (DSS) in phase space as the coupling constant tends to a critical value. |
gr-qc/0609014 | Robert J. Scherrer | Rupam Das, Thomas W. Kephart, and Robert J. Scherrer | Tracking quintessence and k-essence in a general cosmological background | 6 pages, no figures | Phys.Rev.D74:103515,2006 | 10.1103/PhysRevD.74.103515 | null | gr-qc astro-ph hep-th | null | We derive conditions for stable tracker solutions for both quintessence and
k-essence in a general cosmological background, H^2 \propto f(\rho). We find
that tracker solutions are possible only when \eta = d ln f /d ln \rho is
constant, aside from a few special cases, which are enumerated. Expressions for
the quintessence or k-essence equation of state are derived as a function of
\eta and the equation of state of the dominant background component.
| [
{
"created": "Tue, 5 Sep 2006 17:23:24 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Das",
"Rupam",
""
],
[
"Kephart",
"Thomas W.",
""
],
[
"Scherrer",
"Robert J.",
""
]
] | We derive conditions for stable tracker solutions for both quintessence and k-essence in a general cosmological background, H^2 \propto f(\rho). We find that tracker solutions are possible only when \eta = d ln f /d ln \rho is constant, aside from a few special cases, which are enumerated. Expressions for the quintessence or k-essence equation of state are derived as a function of \eta and the equation of state of the dominant background component. |
gr-qc/0506108 | Archan S. Majumdar | A. S. Majumdar, D. Home, S. Sinha | Dark energy from quantum wave function collapse of dark matter | 5 pages in Elsevier style to match with version published in Phys.
Lett. B | Phys.Lett.B679:167-171,2009 | 10.1016/j.physletb.2009.07.042 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical wave function collapse models entail the continuous liberation of a
specified rate of energy arising from the interaction of a fluctuating scalar
field with the matter wave function. We consider the wave function collapse
process for the constituents of dark matter in our universe. Beginning from a
particular early era of the universe chosen from physical considerations, the
rate of the associated energy liberation is integrated to yield the requisite
magnitude of dark energy around the era of galaxy formation. Further, the
equation of state for the liberated energy approaches $w \to -1$
asymptotically, providing a mechanism to generate the present acceleration of
the universe.
| [
{
"created": "Wed, 22 Jun 2005 14:04:19 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Nov 2005 06:51:39 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Sep 2009 09:31:20 GMT",
"version": "v3"
}
] | 2010-10-27 | [
[
"Majumdar",
"A. S.",
""
],
[
"Home",
"D.",
""
],
[
"Sinha",
"S.",
""
]
] | Dynamical wave function collapse models entail the continuous liberation of a specified rate of energy arising from the interaction of a fluctuating scalar field with the matter wave function. We consider the wave function collapse process for the constituents of dark matter in our universe. Beginning from a particular early era of the universe chosen from physical considerations, the rate of the associated energy liberation is integrated to yield the requisite magnitude of dark energy around the era of galaxy formation. Further, the equation of state for the liberated energy approaches $w \to -1$ asymptotically, providing a mechanism to generate the present acceleration of the universe. |
1106.6313 | Jonathan R. Gair | Jonathan R. Gair and Nicolas Yunes | Approximate Waveforms for Extreme-Mass-Ratio Inspirals in Modified
Gravity Spacetimes | v1: 28 pages, no figures; v2: minor changes for consistency with
accepted version, 2 figures added showing sample waveforms; accepted by Phys.
Rev. D | Phys. Rev. D 84 064016 (2011) | 10.1103/PhysRevD.84.064016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extreme-mass-ratio inspirals, in which a stellar-mass compact object spirals
into a supermassive black hole, are prime candidates for detection with
space-borne milliHertz gravitational wave detectors, similar to the Laser
Interferometer Space Antenna. The gravitational waves generated during such
inspirals encode information about the background in which the small object is
moving, providing a tracer of the spacetime geometry and a probe of
strong-field physics. In this paper, we construct approximate,
"analytic-kludge" waveforms for such inspirals with parameterized
post-Einsteinian corrections that allow for generic, model-independent
deformations of the supermassive black hole background away from the Kerr
metric. These approximate waveforms include all of the qualitative features of
true waveforms for generic inspirals, including orbital eccentricity and
relativistic precession. The deformations of the Kerr metric are modeled using
a recently proposed, modified gravity bumpy metric, which parametrically
deforms the Kerr spacetime while ensuring that three approximate constants of
the motion remain for geodesic orbits: a conserved energy, azimuthal angular
momentum and Carter constant. The deformations represent modified gravity
effects and have been analytically mapped to several modified gravity black
hole solutions in four dimensions. In the analytic kludge waveforms, the
conservative motion is modeled by a post-Newtonian expansion of the geodesic
equations in the deformed spacetimes, which in turn induce modifications to the
radiation-reaction force. These analytic-kludge waveforms serve as a first step
toward complete and model-independent tests of General Relativity with extreme
mass-ratio inspirals.
| [
{
"created": "Thu, 30 Jun 2011 17:31:38 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Aug 2011 15:39:21 GMT",
"version": "v2"
}
] | 2011-09-15 | [
[
"Gair",
"Jonathan R.",
""
],
[
"Yunes",
"Nicolas",
""
]
] | Extreme-mass-ratio inspirals, in which a stellar-mass compact object spirals into a supermassive black hole, are prime candidates for detection with space-borne milliHertz gravitational wave detectors, similar to the Laser Interferometer Space Antenna. The gravitational waves generated during such inspirals encode information about the background in which the small object is moving, providing a tracer of the spacetime geometry and a probe of strong-field physics. In this paper, we construct approximate, "analytic-kludge" waveforms for such inspirals with parameterized post-Einsteinian corrections that allow for generic, model-independent deformations of the supermassive black hole background away from the Kerr metric. These approximate waveforms include all of the qualitative features of true waveforms for generic inspirals, including orbital eccentricity and relativistic precession. The deformations of the Kerr metric are modeled using a recently proposed, modified gravity bumpy metric, which parametrically deforms the Kerr spacetime while ensuring that three approximate constants of the motion remain for geodesic orbits: a conserved energy, azimuthal angular momentum and Carter constant. The deformations represent modified gravity effects and have been analytically mapped to several modified gravity black hole solutions in four dimensions. In the analytic kludge waveforms, the conservative motion is modeled by a post-Newtonian expansion of the geodesic equations in the deformed spacetimes, which in turn induce modifications to the radiation-reaction force. These analytic-kludge waveforms serve as a first step toward complete and model-independent tests of General Relativity with extreme mass-ratio inspirals. |
gr-qc/0309128 | Edgard Casal de Rey de Rey Neto | Edgard C. de Rey Neto | Geodesic deviation in pp-wave spacetimes of quadratic curvature gravity | 16 pages, no figures, accepted in Physical Review D | Phys.Rev. D68 (2003) 124013 | 10.1103/PhysRevD.68.124013 | null | gr-qc | null | We write the equation of geodesic deviations in the spacetime of $pp$-waves
in terms of the Newman-Penrose scalars and apply it to study gravitational
waves in quadratic curvature gravity. We show that quadratic curvature gravity
$pp$-waves can have a transverse helicity-0 polarization mode and two
transverse helicity-2 general relativity-like wave polarizations. A concrete
example is given in which we analyze the wave polarizations of an exact
impulsive gravitational wave solution to quadratic curvature gravity.
| [
{
"created": "Fri, 26 Sep 2003 13:05:17 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Neto",
"Edgard C. de Rey",
""
]
] | We write the equation of geodesic deviations in the spacetime of $pp$-waves in terms of the Newman-Penrose scalars and apply it to study gravitational waves in quadratic curvature gravity. We show that quadratic curvature gravity $pp$-waves can have a transverse helicity-0 polarization mode and two transverse helicity-2 general relativity-like wave polarizations. A concrete example is given in which we analyze the wave polarizations of an exact impulsive gravitational wave solution to quadratic curvature gravity. |
1905.06932 | Rajibul Shaikh | Rajibul Shaikh, Pritam Banerjee, Suvankar Paul, Tapobrata Sarkar | Strong gravitational lensing by wormholes | 29 pages, 7 figures, published in JCAP, references added | JCAP 07 (2019) 028 | 10.1088/1475-7516/2019/07/028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study strong gravitational lensing by a class of static wormhole
geometries. Analytical approaches to the same are developed, and the results
differ substantially from strong lensing by black holes, first reported by
Bozza. We consider two distinct situations, one in which the observer and the
source are on the same side of the wormhole throat, and the other in which they
are on opposite sides. Distinctive features in our study arise from the fact
that photon and antiphoton spheres might be present on both sides of the
wormhole throat, and that the throat might itself act as a photon sphere. We
show that strong gravitational lensing thus opens up a rich variety of
possibilities of relativistic image formation, some of which are novel, and are
qualitatively distinct from black hole lensing. These can serve as clear
indicators of exotic wormhole geometries.
| [
{
"created": "Thu, 16 May 2019 17:50:01 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jul 2019 11:50:51 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Nov 2023 12:31:04 GMT",
"version": "v3"
}
] | 2023-11-07 | [
[
"Shaikh",
"Rajibul",
""
],
[
"Banerjee",
"Pritam",
""
],
[
"Paul",
"Suvankar",
""
],
[
"Sarkar",
"Tapobrata",
""
]
] | We study strong gravitational lensing by a class of static wormhole geometries. Analytical approaches to the same are developed, and the results differ substantially from strong lensing by black holes, first reported by Bozza. We consider two distinct situations, one in which the observer and the source are on the same side of the wormhole throat, and the other in which they are on opposite sides. Distinctive features in our study arise from the fact that photon and antiphoton spheres might be present on both sides of the wormhole throat, and that the throat might itself act as a photon sphere. We show that strong gravitational lensing thus opens up a rich variety of possibilities of relativistic image formation, some of which are novel, and are qualitatively distinct from black hole lensing. These can serve as clear indicators of exotic wormhole geometries. |
gr-qc/0008044 | Forough Nasseri | Forough Nasseri, Sohrab Rahvar | Chaotic Inflation with Time-Variable Space Dimensions | 19 pages, To be published in Int.J.Mod.Phys.D. Minor changes to match
accepted version | Int.J.Mod.Phys. D11 (2002) 511-526 | 10.1142/S0218271802001834 | null | gr-qc astro-ph | null | Assuming the space dimension is not constant but decreases during the
expansion of the Universe, we study chaotic inflation with the potential
$m^2\phi^2/2$. Our investigations are based on a model Universe with variable
space dimensions. We write down field equations in the slow-roll approximation,
and define slow-roll parameters by assuming the number of space dimensions
decreases continuously as the Universe expands. The dynamical character of the
space dimension shifts the initial and final value of the inflaton field to
larger values. We obtain an upper limit for the space dimension at the Planck
length. This result is in agreement with previous works for the effective time
variation of the Newtonian gravitational constant in a model Universe with
variable space dimensions.
| [
{
"created": "Fri, 18 Aug 2000 08:20:40 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Dec 2001 06:19:48 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Nasseri",
"Forough",
""
],
[
"Rahvar",
"Sohrab",
""
]
] | Assuming the space dimension is not constant but decreases during the expansion of the Universe, we study chaotic inflation with the potential $m^2\phi^2/2$. Our investigations are based on a model Universe with variable space dimensions. We write down field equations in the slow-roll approximation, and define slow-roll parameters by assuming the number of space dimensions decreases continuously as the Universe expands. The dynamical character of the space dimension shifts the initial and final value of the inflaton field to larger values. We obtain an upper limit for the space dimension at the Planck length. This result is in agreement with previous works for the effective time variation of the Newtonian gravitational constant in a model Universe with variable space dimensions. |
0712.0888 | Sergei Rubin | K.A. Bronnikov, S.G. Rubin | Abilities of multidimensional gravity | 6 pages, 3 figures | Grav.Cosmol.13:253,2007 | null | null | gr-qc | null | We show that a number of problems of modern cosmology may be addressed and
solved in the framework of multidimensional gravity with high-order curvature
invariants, without invoking other fields. As applications of this approach, we
mention primordial inflation and particle production after it; description of
the modern accelerated stage of the Universe with stable compact extra
dimensions; construction of asymmetric thick brane-world models.
| [
{
"created": "Thu, 6 Dec 2007 08:33:05 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Dec 2007 11:31:34 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Rubin",
"S. G.",
""
]
] | We show that a number of problems of modern cosmology may be addressed and solved in the framework of multidimensional gravity with high-order curvature invariants, without invoking other fields. As applications of this approach, we mention primordial inflation and particle production after it; description of the modern accelerated stage of the Universe with stable compact extra dimensions; construction of asymmetric thick brane-world models. |
2103.11826 | Yeinzon Rodriguez Garcia | L. Gabriel Gomez (1), Yeinzon Rodriguez (2,3), Juan P. Beltran Almeida
(4) ((1) Universidad de Santiago de Chile, (2) Universidad Antonio Narino,
(3) Universidad Industrial de Santander, (4) Universidad Nacional de
Colombia) | Anisotropic Scalar Field Dark Energy with a Disformally Coupled
Yang-Mills Field | LaTeX file in jcappub style, 40 pages, 11 figures. v2: some cosmetic
changes and new references added. v3 and v4: more changes to add clarity to
the paper and new material added. Conclusions unchanged. v5: version to
appear in International Journal of Modern Physics D | Int. J. Mod. Phys. D 31, 2250060 (2022) | 10.1142/S0218271822500602 | PI/UAN-2021-687FT | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of scalar-tensor theories, the inclusion of new degrees of
freedom coupled non-minimally to the gravitational sector might produce some
appealing effects on the cosmic expansion history. We investigate this premise
by including a canonical SU(2) Yang- Mills field to the total energy budget of
the universe coupled to the standard quintessential field by a disformal
transformation. From the dynamical system analysis, we study three cases of
cosmological interest that span most of the physical phase space of the model:
the uncoupled limit, the isotropic, and the Abelian cases. New scaling
solutions with a non-vanishing gauge field are found in all cases which can be
interesting for early cosmological scenarios. Some of these scaling solutions
even exhibit anisotropic features. Also, the background evolution of the
universe is studied by means of numerical analysis. As an interesting result,
the disformal coupling changes the equation of state of the gauge field from
radiation to matter at some stages of the evolution of the universe, thereby
the gauge field can contribute to some fraction of the total dark matter. We
have also quantified the redshift-dependent contribution of the gauge field in
the form of dark radiation during the radiation era to the effective number of
relativistic species. This depends essentially on the initial conditions and,
more importantly, on the disformal coupling function.
| [
{
"created": "Thu, 18 Mar 2021 12:45:56 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jul 2021 13:58:05 GMT",
"version": "v2"
},
{
"created": "Fri, 12 Nov 2021 23:09:30 GMT",
"version": "v3"
},
{
"created": "Thu, 24 Mar 2022 02:24:57 GMT",
"version": "v4"
},
{
"created": "Thu, 28 Apr 2022 17:50:38 GMT",
"version": "v5"
}
] | 2022-05-04 | [
[
"Gomez",
"L. Gabriel",
""
],
[
"Rodriguez",
"Yeinzon",
""
],
[
"Almeida",
"Juan P. Beltran",
""
]
] | In the context of scalar-tensor theories, the inclusion of new degrees of freedom coupled non-minimally to the gravitational sector might produce some appealing effects on the cosmic expansion history. We investigate this premise by including a canonical SU(2) Yang- Mills field to the total energy budget of the universe coupled to the standard quintessential field by a disformal transformation. From the dynamical system analysis, we study three cases of cosmological interest that span most of the physical phase space of the model: the uncoupled limit, the isotropic, and the Abelian cases. New scaling solutions with a non-vanishing gauge field are found in all cases which can be interesting for early cosmological scenarios. Some of these scaling solutions even exhibit anisotropic features. Also, the background evolution of the universe is studied by means of numerical analysis. As an interesting result, the disformal coupling changes the equation of state of the gauge field from radiation to matter at some stages of the evolution of the universe, thereby the gauge field can contribute to some fraction of the total dark matter. We have also quantified the redshift-dependent contribution of the gauge field in the form of dark radiation during the radiation era to the effective number of relativistic species. This depends essentially on the initial conditions and, more importantly, on the disformal coupling function. |
1310.0339 | Martin Reiris | Martin Reiris | Stationary solutions and asymptotic flatness II | null | null | 10.1088/0264-9381/31/15/155013 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the second part of the investigation started in [Stationary solutions
and asymptotic flatness I]. We prove here that Strongly Stationary ends having
cubic volume growth are Weakly Asymptotically Flat. Combined with the results
of the previous paper this shows that Strongly Stationary ends are
Asymptotically Flat with Schwarzschidian fall off.
| [
{
"created": "Tue, 1 Oct 2013 15:04:55 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Reiris",
"Martin",
""
]
] | This is the second part of the investigation started in [Stationary solutions and asymptotic flatness I]. We prove here that Strongly Stationary ends having cubic volume growth are Weakly Asymptotically Flat. Combined with the results of the previous paper this shows that Strongly Stationary ends are Asymptotically Flat with Schwarzschidian fall off. |
gr-qc/0406092 | Volodymyr Gorkavenko | Volodymyr M. Gorkavenko and Alexander V. Viznyuk | Semiclassical gravitational effects near a singular magnetic flux | 14 pages, 4 figures, journal version | Phys.Lett. B604 (2004) 103-114 | 10.1016/j.physletb.2004.10.043 | null | gr-qc | null | We consider the backreaction of the vacuum polarization effect for a massive
charged scalar field in the presence of a singular magnetic massless string on
the background metric. Using semiclassical approach, we find the first-order
(in $\hbar$ units) metric modifications and the corresponding gravitational
potential and deficit angle. It is shown that, in certain region of values of
coupling constant and magnetic flux, the gravitational potential and deficit
angle can be positive as well as negative over all distances from the string
and can even change its sign. Unlike the case of massless scalar field, the
gravitational corrections were found to have short-range behavior.
| [
{
"created": "Wed, 23 Jun 2004 08:36:10 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jul 2004 12:09:06 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Mar 2005 10:19:05 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Gorkavenko",
"Volodymyr M.",
""
],
[
"Viznyuk",
"Alexander V.",
""
]
] | We consider the backreaction of the vacuum polarization effect for a massive charged scalar field in the presence of a singular magnetic massless string on the background metric. Using semiclassical approach, we find the first-order (in $\hbar$ units) metric modifications and the corresponding gravitational potential and deficit angle. It is shown that, in certain region of values of coupling constant and magnetic flux, the gravitational potential and deficit angle can be positive as well as negative over all distances from the string and can even change its sign. Unlike the case of massless scalar field, the gravitational corrections were found to have short-range behavior. |
1907.03484 | Denis Dobkowski-Ry{\l}ko | Denis Dobkowski-Ry{\l}ko, Jerzy Lewandowski, Istv\'an R\'acz | Petrov type D equation on horizons of nontrivial bundle topology | null | Phys. Rev. D 100, 084058 (2019) | 10.1103/PhysRevD.100.084058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $3$-dimensional isolated horizons (IHs) generated by null curves
that form nontrivial $U(1)$ bundles. We find a natural interplay between the IH
geometry and the $U(1)$-bundle geometry. In this context we consider the Petrov
type D equation introduced and studied in previous works
\cite{DLP1,DLP2,LS,DKLS1}. From the $4$-dimensional spacetime point of view,
solutions to that equation define isolated horizons embeddable in vacuum
spacetimes (with cosmological constant) as Killing horizons to the second order
such that the spacetime Weyl tensor at the horizon is of the Petrov type D.
From the point of view of the $U(1)$-bundle structure, the equation couples a
$U(1)$-connection, a metric tensor defined on the base manifold and the surface
gravity in a very nontrivial way. We focus on the $U(1)$-bundles over
$2$-dimensional manifolds diffeomorphic to $2$-sphere. We have derived all the
axisymmetric solutions to the Petrov type D equation. For a fixed value of the
cosmological constant they set a $3$-dimensional family as one could expect. A
surprising result is, that generically our horizons are not embeddable in the
known exact solutions to Einstein's equations. It means that among the exact
type D spacetimes there exists a new family of spacetimes that generalize the
properties of the Kerr- (anti) de Sitter black holes on one hand and the
Taub-NUT spacetimes on the other hand.
| [
{
"created": "Mon, 8 Jul 2019 10:01:03 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 2019 14:47:33 GMT",
"version": "v2"
},
{
"created": "Wed, 13 May 2020 20:21:27 GMT",
"version": "v3"
}
] | 2020-05-15 | [
[
"Dobkowski-Ryłko",
"Denis",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Rácz",
"István",
""
]
] | We consider $3$-dimensional isolated horizons (IHs) generated by null curves that form nontrivial $U(1)$ bundles. We find a natural interplay between the IH geometry and the $U(1)$-bundle geometry. In this context we consider the Petrov type D equation introduced and studied in previous works \cite{DLP1,DLP2,LS,DKLS1}. From the $4$-dimensional spacetime point of view, solutions to that equation define isolated horizons embeddable in vacuum spacetimes (with cosmological constant) as Killing horizons to the second order such that the spacetime Weyl tensor at the horizon is of the Petrov type D. From the point of view of the $U(1)$-bundle structure, the equation couples a $U(1)$-connection, a metric tensor defined on the base manifold and the surface gravity in a very nontrivial way. We focus on the $U(1)$-bundles over $2$-dimensional manifolds diffeomorphic to $2$-sphere. We have derived all the axisymmetric solutions to the Petrov type D equation. For a fixed value of the cosmological constant they set a $3$-dimensional family as one could expect. A surprising result is, that generically our horizons are not embeddable in the known exact solutions to Einstein's equations. It means that among the exact type D spacetimes there exists a new family of spacetimes that generalize the properties of the Kerr- (anti) de Sitter black holes on one hand and the Taub-NUT spacetimes on the other hand. |
1304.6725 | Richard Brito | Richard Brito, Vitor Cardoso, Paolo Pani | Massive spin-2 fields on black hole spacetimes: Instability of the
Schwarzschild and Kerr solutions and bounds on the graviton mass | 24 pages, 8 figures. v2: references added and discussion extended.
v3: references added, matches published version | Phys.Rev.D88:023514,2013 | 10.1103/PhysRevD.88.023514 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive bosonic fields of arbitrary spin are predicted by general extensions
of the Standard Model. It has been recently shown that there exists a family of
bimetric theories of gravity - including massive gravity - which are free of
Boulware-Deser ghosts at the nonlinear level. This opens up the possibility to
describe consistently the dynamics of massive spin-2 particles in a
gravitational field. Within this context, we develop the study of massive
spin-2 fluctuations - including massive gravitons - around Schwarzschild and
slowly-rotating Kerr black holes. Our work has two important outcomes. First,
we show that the Schwarzschild geometry is linearly unstable for small tensor
masses, against a spherically symmetric mode. Second, we provide solid evidence
that the Kerr geometry is also generically unstable, both against the spherical
mode and against long-lived superradiant modes. In the absence of nonlinear
effects, the observation of spinning black holes bounds the graviton mass to be
smaller than 5x10^{-23} eV.
| [
{
"created": "Wed, 24 Apr 2013 20:00:04 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2013 18:52:49 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Jul 2013 13:39:30 GMT",
"version": "v3"
}
] | 2013-07-12 | [
[
"Brito",
"Richard",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Pani",
"Paolo",
""
]
] | Massive bosonic fields of arbitrary spin are predicted by general extensions of the Standard Model. It has been recently shown that there exists a family of bimetric theories of gravity - including massive gravity - which are free of Boulware-Deser ghosts at the nonlinear level. This opens up the possibility to describe consistently the dynamics of massive spin-2 particles in a gravitational field. Within this context, we develop the study of massive spin-2 fluctuations - including massive gravitons - around Schwarzschild and slowly-rotating Kerr black holes. Our work has two important outcomes. First, we show that the Schwarzschild geometry is linearly unstable for small tensor masses, against a spherically symmetric mode. Second, we provide solid evidence that the Kerr geometry is also generically unstable, both against the spherical mode and against long-lived superradiant modes. In the absence of nonlinear effects, the observation of spinning black holes bounds the graviton mass to be smaller than 5x10^{-23} eV. |
2303.12090 | Ghulam Abbas | H. Nazar, M. Azam, G. Abbas, R. Ahmed and R. Naeem | Relativistic Polytropic Models of Charged Anisotropic Compact Object | 31 Pages, 11 Figures, 1 Table. Published in Chinese Phys. C | Chinese Phys. C 47 (2023) 035109 | 10.1088/1674-1137/acae5b | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we have introduced new viable solutions of Einstein-Maxwell
field equations by incorporating the features of anisotropic matter
distribution in the realm of General theory of Relativity ($GR$). For this
procurement, we have employed a Finch-Skea spacetime along with a generalized
polytropic equation of state ($EoS$). We have constructed various models of
generalized polytropes by assuming the different choices of the polytropic
index i.e.,$\eta=\frac{1}{2}, \frac{2}{3}, 1$ and $2$. The numerous physical
characteristics of these considered models have been studied via graphical
analysis, which obey all the essential conditions of the astrophysical compact
objects. Furthermore, such outcomes of charged anisotropic compact star models
can be regained to the various cases such as linear, quadratic and polytropic
$EoS$.
| [
{
"created": "Mon, 20 Mar 2023 20:27:27 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Nazar",
"H.",
""
],
[
"Azam",
"M.",
""
],
[
"Abbas",
"G.",
""
],
[
"Ahmed",
"R.",
""
],
[
"Naeem",
"R.",
""
]
] | In this paper, we have introduced new viable solutions of Einstein-Maxwell field equations by incorporating the features of anisotropic matter distribution in the realm of General theory of Relativity ($GR$). For this procurement, we have employed a Finch-Skea spacetime along with a generalized polytropic equation of state ($EoS$). We have constructed various models of generalized polytropes by assuming the different choices of the polytropic index i.e.,$\eta=\frac{1}{2}, \frac{2}{3}, 1$ and $2$. The numerous physical characteristics of these considered models have been studied via graphical analysis, which obey all the essential conditions of the astrophysical compact objects. Furthermore, such outcomes of charged anisotropic compact star models can be regained to the various cases such as linear, quadratic and polytropic $EoS$. |
2405.05698 | Lorenz Zwick | Lorenz Zwick, Christopher Tiede, Alessandro A. Trani, Andrea
Derdzinski, Zoltan Haiman, Daniel J. D'Orazio and Johan Samsing | Detecting environmental effects in gravitational waves from binaries
perturbed by periodic forces | Submitted to PRD. Comments welcome | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/publicdomain/zero/1.0/ | We study the gravitational wave (GW) emission of sources perturbed by
periodic dynamical forces which do not cause secular evolution in the orbital
elements. We construct a corresponding post-Newtonian waveform model and
provide estimates for the detectability of the resulting GW phase
perturbations, for both space-based and future ground-based detectors. We
validate our results by performing a set of Bayesian parameter recovery
experiments with post-Newtonian waveforms. We find that, in stark contrast to
the more commonly studied secular dephasing, periodic phase perturbations do
not suffer from degeneracies with any of the tested vacuum binary parameters.
We discuss the applications of our findings to a range of possible
astrophysical scenarios, finding that such periodic perturbations may be
detectable for massive black hole binaries embedded in circum-binary discs,
extreme mass-ratio inspirals in accretion discs, as well as stellar-mass
compact objects perturbed by tidal fields. We argue that modelling conservative
sub-orbital dynamics opens up a promising new avenue to detect environmental
effects in binary sources of GWs that should be included in state-of-the-art
waveform templates.
| [
{
"created": "Thu, 9 May 2024 11:54:10 GMT",
"version": "v1"
},
{
"created": "Wed, 15 May 2024 11:23:23 GMT",
"version": "v2"
}
] | 2024-05-16 | [
[
"Zwick",
"Lorenz",
""
],
[
"Tiede",
"Christopher",
""
],
[
"Trani",
"Alessandro A.",
""
],
[
"Derdzinski",
"Andrea",
""
],
[
"Haiman",
"Zoltan",
""
],
[
"D'Orazio",
"Daniel J.",
""
],
[
"Samsing",
"Johan",
""
]
] | We study the gravitational wave (GW) emission of sources perturbed by periodic dynamical forces which do not cause secular evolution in the orbital elements. We construct a corresponding post-Newtonian waveform model and provide estimates for the detectability of the resulting GW phase perturbations, for both space-based and future ground-based detectors. We validate our results by performing a set of Bayesian parameter recovery experiments with post-Newtonian waveforms. We find that, in stark contrast to the more commonly studied secular dephasing, periodic phase perturbations do not suffer from degeneracies with any of the tested vacuum binary parameters. We discuss the applications of our findings to a range of possible astrophysical scenarios, finding that such periodic perturbations may be detectable for massive black hole binaries embedded in circum-binary discs, extreme mass-ratio inspirals in accretion discs, as well as stellar-mass compact objects perturbed by tidal fields. We argue that modelling conservative sub-orbital dynamics opens up a promising new avenue to detect environmental effects in binary sources of GWs that should be included in state-of-the-art waveform templates. |
2209.12701 | Jo\~ao Lu\'is Rosa | Jo\~ao Lu\'is Rosa, Paul Martin Kull | Non-exotic traversable wormhole solutions in linear $f\left(R,T\right)$
gravity | 16 pages, 3 figures | The European Physical Journal C volume 82, Article number: 1154
(2022) | 10.1140/epjc/s10052-022-11135-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we analyze traversable wormhole solutions in the linear form of
$f\left(R,T\right)=R+\lambda T$ gravity satisfying the Null, Weak, Strong, and
Dominant Energy Conditions (NEC, WEC, SEC, and DEC respectively) for the entire
spacetime. These solutions are obtained via a fully analytical parameter space
analysis of the free parameters of the wormhole model, namely the exponents
controlling the degree of the redshift and shape functions, the radius of the
wormhole throat $r_0$, the value of the redshift function at the throat
$\zeta_0$, and the coupling parameter $\lambda$. Bounds on these free
parameters for which the energy conditions are satisfied for the entire
spacetime are deduced and two explicit solutions are provided. Even if some of
these bounds are violated, leading to the violation of the NEC at some critical
radius $r_c>r_0$, it is still possible to find physically relevant wormhole
solutions via a matching with an exterior vacuum spacetime in the region where
the energy conditions are still satisfied. For this purpose, we deduce the set
of junction conditions for the form of $f\left(R,T\right)$ considered and
provide an explicit example. These results seem to indicate that a wide variety
of non-exotic wormhole solutions are attainable in the $f\left(R,T\right)$
theory without the requirement of fine-tuning.
| [
{
"created": "Mon, 26 Sep 2022 13:51:42 GMT",
"version": "v1"
}
] | 2022-12-23 | [
[
"Rosa",
"João Luís",
""
],
[
"Kull",
"Paul Martin",
""
]
] | In this work we analyze traversable wormhole solutions in the linear form of $f\left(R,T\right)=R+\lambda T$ gravity satisfying the Null, Weak, Strong, and Dominant Energy Conditions (NEC, WEC, SEC, and DEC respectively) for the entire spacetime. These solutions are obtained via a fully analytical parameter space analysis of the free parameters of the wormhole model, namely the exponents controlling the degree of the redshift and shape functions, the radius of the wormhole throat $r_0$, the value of the redshift function at the throat $\zeta_0$, and the coupling parameter $\lambda$. Bounds on these free parameters for which the energy conditions are satisfied for the entire spacetime are deduced and two explicit solutions are provided. Even if some of these bounds are violated, leading to the violation of the NEC at some critical radius $r_c>r_0$, it is still possible to find physically relevant wormhole solutions via a matching with an exterior vacuum spacetime in the region where the energy conditions are still satisfied. For this purpose, we deduce the set of junction conditions for the form of $f\left(R,T\right)$ considered and provide an explicit example. These results seem to indicate that a wide variety of non-exotic wormhole solutions are attainable in the $f\left(R,T\right)$ theory without the requirement of fine-tuning. |
1110.0659 | Aur\'elien Hees | A. Hees, P. Wolf, B. Lamine, S. Reynaud, M.T. Jaekel, C. Le
Poncin-Lafitte, V. Lainey and V. Dehant | Testing Gravitation in the Solar System with Radio Science experiments | proceedings of SF2A 2011 - minor changes (typos corrected -
references updated) | SF2A 2011 (SF2A, 2011) p.653-658 | null | null | gr-qc astro-ph.IM physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The laws of gravitation have been tested for a long time with steadily
improving precision, leading at some moment of time to paradigmatic evolutions.
Pursuing this continual effort is of great importance for science. In this
communication, we focus on Solar System tests of gravity and more precisely on
possible tests that can be performed with radio science observations (Range and
Doppler). After briefly reviewing the current tests of gravitation at Solar
System scales, we give motivations to continue such experiments. In order to
obtain signature and estimate the amplitude of anomalous signals that could
show up in radio science observables because of modified gravitational laws, we
developed a new software that simulates Range/Doppler signals. We present this
new tool that simulates radio science observables directly from the space-time
metric. We apply this tool to the Cassini mission during its cruise from
Jupiter to Saturn and derive constraints on the parameters entering alternative
theories of gravity beyond the standard Parametrized Post Newtonian theory.
| [
{
"created": "Tue, 4 Oct 2011 12:36:33 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Nov 2011 10:55:50 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"Hees",
"A.",
""
],
[
"Wolf",
"P.",
""
],
[
"Lamine",
"B.",
""
],
[
"Reynaud",
"S.",
""
],
[
"Jaekel",
"M. T.",
""
],
[
"Poncin-Lafitte",
"C. Le",
""
],
[
"Lainey",
"V.",
""
],
[
"Dehant",
"V.",
""
]
] | The laws of gravitation have been tested for a long time with steadily improving precision, leading at some moment of time to paradigmatic evolutions. Pursuing this continual effort is of great importance for science. In this communication, we focus on Solar System tests of gravity and more precisely on possible tests that can be performed with radio science observations (Range and Doppler). After briefly reviewing the current tests of gravitation at Solar System scales, we give motivations to continue such experiments. In order to obtain signature and estimate the amplitude of anomalous signals that could show up in radio science observables because of modified gravitational laws, we developed a new software that simulates Range/Doppler signals. We present this new tool that simulates radio science observables directly from the space-time metric. We apply this tool to the Cassini mission during its cruise from Jupiter to Saturn and derive constraints on the parameters entering alternative theories of gravity beyond the standard Parametrized Post Newtonian theory. |
1904.11599 | Mauricio Bellini | Juan Ignacio Musmarra (IFIMAR - CONICET & UNMDP), Mauricio Bellini
(IFIMAR - CONICET & UNMDP), Mariano Anabitarte (IFIMAR - CONICET & UNMDP) | Quantum thermodynamics in the interior of a Schwarzschild B-H | Improved version. arXiv admin note: text overlap with
arXiv:1908.11716 | null | 10.1088/1402-4896/abd203 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the interior of a Schwarzschild Black-Hole (B-H) using Relativistic
Quantum Geometry described in \cite{rb} and \cite{rb1}. We found discrete
energy levels for a scalar field from a polynomial condition for Heun Confluent
functions expanded around the Schwarzschild radius. From the solutions it is
obtained that the uncertainty principle is valid for each energy level of
space-time, in the form: $E_n\, r_{sh,n}=\hbar/2$. Temperature, entropy and the
B-H mass are dependent on the number of states in the B-H, such that the
Bekenstein-Hawking (BH) results are obtained in a limit case.
| [
{
"created": "Thu, 25 Apr 2019 21:40:04 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Sep 2019 12:38:57 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Oct 2019 21:52:41 GMT",
"version": "v3"
},
{
"created": "Mon, 9 Dec 2019 22:39:29 GMT",
"version": "v4"
}
] | 2021-08-16 | [
[
"Musmarra",
"Juan Ignacio",
"",
"IFIMAR - CONICET & UNMDP"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR - CONICET & UNMDP"
],
[
"Anabitarte",
"Mariano",
"",
"IFIMAR - CONICET & UNMDP"
]
] | We study the interior of a Schwarzschild Black-Hole (B-H) using Relativistic Quantum Geometry described in \cite{rb} and \cite{rb1}. We found discrete energy levels for a scalar field from a polynomial condition for Heun Confluent functions expanded around the Schwarzschild radius. From the solutions it is obtained that the uncertainty principle is valid for each energy level of space-time, in the form: $E_n\, r_{sh,n}=\hbar/2$. Temperature, entropy and the B-H mass are dependent on the number of states in the B-H, such that the Bekenstein-Hawking (BH) results are obtained in a limit case. |
2104.04682 | Fei Wang | Fei Wang, Rui Wang | Q-balls Formation and the Production of Gravitational Waves With
Non-minimal Gravitational Coupling | 15 pages, 4 figures. Published version in EPJC | null | 10.1140/epjc/s10052-022-10291-3 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose to introduce non-minimal couplings of Affleck-Dine (AD) field to
gravity by adding the coupling of AD field to the Ricci scalar curvature. As
the Jordan frame supergravity always predict $|\Phi|^2 {\cal R}/6$ type
coupling for scalars with canonical kinetic terms, we propose a way to realize
the required $c_0|\Phi|^2 {\cal R}$-type couplings with generic $c_0$ for
canonical complex scalar fields after SUSY breaking. The impacts of such
non-minimal gravitational couplings for AD field is shown, especially on the
Q-balls formation and the associated gravitational wave (GW) productions. New
form of scalar potential for AD field in the Einstein frame is obtained. By
numerical simulations, we find that, with non-minimal gravitational coupling to
AD field, Q-balls can successfully form even with the choice of non-negative
$K$ parameter for $\xi>0$. The associated GW productions as well as their
dependences on the $\xi$ parameter are also discussed.
| [
{
"created": "Sat, 10 Apr 2021 04:39:51 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Dec 2021 07:29:58 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Apr 2022 13:17:54 GMT",
"version": "v3"
}
] | 2022-04-13 | [
[
"Wang",
"Fei",
""
],
[
"Wang",
"Rui",
""
]
] | We propose to introduce non-minimal couplings of Affleck-Dine (AD) field to gravity by adding the coupling of AD field to the Ricci scalar curvature. As the Jordan frame supergravity always predict $|\Phi|^2 {\cal R}/6$ type coupling for scalars with canonical kinetic terms, we propose a way to realize the required $c_0|\Phi|^2 {\cal R}$-type couplings with generic $c_0$ for canonical complex scalar fields after SUSY breaking. The impacts of such non-minimal gravitational couplings for AD field is shown, especially on the Q-balls formation and the associated gravitational wave (GW) productions. New form of scalar potential for AD field in the Einstein frame is obtained. By numerical simulations, we find that, with non-minimal gravitational coupling to AD field, Q-balls can successfully form even with the choice of non-negative $K$ parameter for $\xi>0$. The associated GW productions as well as their dependences on the $\xi$ parameter are also discussed. |
1207.5170 | Richard T. Hammond | Richard T. Hammond | New spin on Einstein's non-symmetric metric tensor | 5 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A solution to the gravitational field equations based on a non-symmetric
metric tensor is examined. Unlike Einstein's interpretation of
electromagnetism, or Moffat's generalized gravity, it is shown that the
non-symmetric part of the metric tensor is the potential of the spin field.
This is in agreement with string theory and provides a natural coupling between
gravitation and strings.
| [
{
"created": "Sat, 21 Jul 2012 19:40:33 GMT",
"version": "v1"
}
] | 2012-07-24 | [
[
"Hammond",
"Richard T.",
""
]
] | A solution to the gravitational field equations based on a non-symmetric metric tensor is examined. Unlike Einstein's interpretation of electromagnetism, or Moffat's generalized gravity, it is shown that the non-symmetric part of the metric tensor is the potential of the spin field. This is in agreement with string theory and provides a natural coupling between gravitation and strings. |
0906.2937 | Lorenzo Iorio | Lorenzo Iorio | On the MOND External Field Effect in the Solar System | Latex2e, 6 pages, 3 tables, 2 figures. Accepted for publication in
Astrophysics & Space Science (ApSS) | Astrophys. Space Sci.323:215-219, 2009 | 10.1007/s10509-009-0061-3 | null | gr-qc astro-ph.CO astro-ph.EP astro-ph.GA physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the MOdified Newtonian Dynamics (MOND), the internal
dynamics of a gravitating system s embedded in a larger one S is affected by
the external background field E of S even if it is constant and uniform, thus
implying a violation of the Strong Equivalence Principle: it is the so-called
External Field Effect (EFE). In the case of the solar system, E would be
A_cen\approx 10^-10 m s^-2 because of its motion through the Milky Way: it is
orders of magnitude smaller than the main Newtonian monopole terms for the
planets. We address here the following questions in a purely phenomenological
manner: are the Sun's planets affected by an EFE as large as 10^-10 m s^-2? Can
it be assumed that its effect is negligible for them because of its relatively
small size? Does $\bds E$ induce vanishing net orbital effects because of its
constancy over typical solar system's planetary orbital periods? It turns out
that a constant and uniform acceleration, treated perturbatively, does induce
non-vanishing long-period orbital effects on the longitude of the pericenter of
a test particle. In the case of the inner planets of the solar system and with
E\approx 10^-10 m s^-2, they are 4-6 orders of magnitude larger than the
present-day upper bounds on the non-standard perihelion precessions recently
obtained with by E.V. Pitjeva with the EPM ephemerides in the Solar System
Barycentric frame. The upper limits on the components of E are E_x <= 1 x
10^-15 m s^-2, E_y <= 2 x 10^-16 m s^-2, E_z <= 3 x 10^-14 m s^-2. This result
is in agreement with the violation of the Strong Equivalence Principle by MOND.
| [
{
"created": "Tue, 16 Jun 2009 13:55:14 GMT",
"version": "v1"
}
] | 2009-09-17 | [
[
"Iorio",
"Lorenzo",
""
]
] | In the framework of the MOdified Newtonian Dynamics (MOND), the internal dynamics of a gravitating system s embedded in a larger one S is affected by the external background field E of S even if it is constant and uniform, thus implying a violation of the Strong Equivalence Principle: it is the so-called External Field Effect (EFE). In the case of the solar system, E would be A_cen\approx 10^-10 m s^-2 because of its motion through the Milky Way: it is orders of magnitude smaller than the main Newtonian monopole terms for the planets. We address here the following questions in a purely phenomenological manner: are the Sun's planets affected by an EFE as large as 10^-10 m s^-2? Can it be assumed that its effect is negligible for them because of its relatively small size? Does $\bds E$ induce vanishing net orbital effects because of its constancy over typical solar system's planetary orbital periods? It turns out that a constant and uniform acceleration, treated perturbatively, does induce non-vanishing long-period orbital effects on the longitude of the pericenter of a test particle. In the case of the inner planets of the solar system and with E\approx 10^-10 m s^-2, they are 4-6 orders of magnitude larger than the present-day upper bounds on the non-standard perihelion precessions recently obtained with by E.V. Pitjeva with the EPM ephemerides in the Solar System Barycentric frame. The upper limits on the components of E are E_x <= 1 x 10^-15 m s^-2, E_y <= 2 x 10^-16 m s^-2, E_z <= 3 x 10^-14 m s^-2. This result is in agreement with the violation of the Strong Equivalence Principle by MOND. |
gr-qc/0001067 | Felix Finster | Felix Finster, Joel Smoller, and Shing-Tung Yau | The Interaction of Dirac Particles with Non-Abelian Gauge Fields and
Gravity - Bound States | 28 pages, 21 figures (published version) | Nucl.Phys.B584:387-414,2000 | 10.1016/S0550-3213(00)00370-9 | null | gr-qc hep-th math-ph math.AP math.MP | null | We consider a spherically symmetric, static system of a Dirac particle
interacting with classical gravity and an SU(2) Yang-Mills field. The
corresponding Einstein-Dirac-Yang/Mills equations are derived. Using numerical
methods, we find different types of soliton-like solutions of these equations
and discuss their properties. Some of these solutions are stable even for
arbitrarily weak gravitational coupling.
| [
{
"created": "Fri, 21 Jan 2000 19:17:14 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Aug 2000 11:54:20 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Finster",
"Felix",
""
],
[
"Smoller",
"Joel",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | We consider a spherically symmetric, static system of a Dirac particle interacting with classical gravity and an SU(2) Yang-Mills field. The corresponding Einstein-Dirac-Yang/Mills equations are derived. Using numerical methods, we find different types of soliton-like solutions of these equations and discuss their properties. Some of these solutions are stable even for arbitrarily weak gravitational coupling. |
gr-qc/0411053 | Diego Meschini | Diego Meschini, Markku Lehto, Johanna Piilonen | Geometry, pregeometry and beyond | 41 pages, Latex. v2: Date added. v3: Main arguments refined,
secondary discussions abridged; expands on the published version | Stud.Hist.Philos.Mod.Phys. 36 (2005) 435-464 | 10.1016/j.shpsb.2005.01.002 | null | gr-qc | null | This article explores the overall geometric manner in which human beings make
sense of the world around them by means of their physical theories; in
particular, in what are nowadays called pregeometric pictures of Nature. In
these, the pseudo-Riemannian manifold of general relativity is considered a
flawed description of spacetime and it is attempted to replace it by
theoretical constructs of a different character, ontologically prior to it.
However, despite its claims to the contrary, pregeometry is found to
surreptitiously and unavoidably fall prey to the very mode of description it
endeavours to evade, as evidenced in its all-pervading geometric understanding
of the world. The question remains as to the deeper reasons for this human,
geometric predilection--present, as a matter of fact, in all of physics--and as
to whether it might need to be superseded in order to achieve the goals that
frontier theoretical physics sets itself at the dawn of a new century: a
sounder comprehension of the physical meaning of empty spacetime.
| [
{
"created": "Wed, 10 Nov 2004 19:42:37 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Nov 2004 10:22:05 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Aug 2006 18:05:29 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Meschini",
"Diego",
""
],
[
"Lehto",
"Markku",
""
],
[
"Piilonen",
"Johanna",
""
]
] | This article explores the overall geometric manner in which human beings make sense of the world around them by means of their physical theories; in particular, in what are nowadays called pregeometric pictures of Nature. In these, the pseudo-Riemannian manifold of general relativity is considered a flawed description of spacetime and it is attempted to replace it by theoretical constructs of a different character, ontologically prior to it. However, despite its claims to the contrary, pregeometry is found to surreptitiously and unavoidably fall prey to the very mode of description it endeavours to evade, as evidenced in its all-pervading geometric understanding of the world. The question remains as to the deeper reasons for this human, geometric predilection--present, as a matter of fact, in all of physics--and as to whether it might need to be superseded in order to achieve the goals that frontier theoretical physics sets itself at the dawn of a new century: a sounder comprehension of the physical meaning of empty spacetime. |
1211.1679 | Richard Brito | Richard Brito | Dynamics around black holes: Radiation Emission and Tidal Effects | Master thesis, CENTRA / Instituto Superior Tecnico, October 2012. 72
pages; v2: References added | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this thesis we study several dynamical processes involving black holes in
four and higher dimensions. First, using perturbative techniques, we compare
the massless and massive scalar radiation emitted by a particle radially
infalling into a Schwarzchild black hole. We show that the late-time waveform
of massive scalar perturbations is dominated by a universal oscillatory
decaying tail, which appears due to curvature effects. We also show that the
energy spectrum is in perfect agreement with a ZFL calculation once no-hair
properties of black holes are taken into account. In the second part, we study
the phenomenon of superradiance in higher dimensions and conjecture that the
maximum energy extracted from a rotating black hole can be understood in terms
of the ergoregion proper volume. We then study some consequences of
superradiance in the dynamics of moons orbiting around higher-dimensional
rotating black holes. In four-dimensional spacetime, moons around black holes
generate low-amplitude tides, and the energy extracted from the hole's rotation
is always smaller than the gravitational radiation lost to infinity. We show
that in dimensions larger than five the energy extracted from the black hole
through superradiance is larger than the energy carried out to infinity. Our
results lend strong support to the conjecture that tidal acceleration is the
rule, rather than the exception, in higher dimensions. Superradiance dominates
the energy budget and moons "outspiral"; for some particular orbital frequency,
the energy extracted at the horizon equals the energy emitted to infinity and
"floating orbits" generically occur. We give an interpretation of this
phenomenon in terms of the membrane paradigm and of tidal acceleration due to
energy dissipation across the horizon.
| [
{
"created": "Wed, 7 Nov 2012 21:02:14 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Nov 2012 12:52:42 GMT",
"version": "v2"
}
] | 2012-11-12 | [
[
"Brito",
"Richard",
""
]
] | In this thesis we study several dynamical processes involving black holes in four and higher dimensions. First, using perturbative techniques, we compare the massless and massive scalar radiation emitted by a particle radially infalling into a Schwarzchild black hole. We show that the late-time waveform of massive scalar perturbations is dominated by a universal oscillatory decaying tail, which appears due to curvature effects. We also show that the energy spectrum is in perfect agreement with a ZFL calculation once no-hair properties of black holes are taken into account. In the second part, we study the phenomenon of superradiance in higher dimensions and conjecture that the maximum energy extracted from a rotating black hole can be understood in terms of the ergoregion proper volume. We then study some consequences of superradiance in the dynamics of moons orbiting around higher-dimensional rotating black holes. In four-dimensional spacetime, moons around black holes generate low-amplitude tides, and the energy extracted from the hole's rotation is always smaller than the gravitational radiation lost to infinity. We show that in dimensions larger than five the energy extracted from the black hole through superradiance is larger than the energy carried out to infinity. Our results lend strong support to the conjecture that tidal acceleration is the rule, rather than the exception, in higher dimensions. Superradiance dominates the energy budget and moons "outspiral"; for some particular orbital frequency, the energy extracted at the horizon equals the energy emitted to infinity and "floating orbits" generically occur. We give an interpretation of this phenomenon in terms of the membrane paradigm and of tidal acceleration due to energy dissipation across the horizon. |
1109.6612 | Yu-Chung Chen | Yu-Chung Chen | The creation of radiation and the relic of inflaton potential | 23 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, we have performed research on the subject of the cosmological
constant problem. The scenario is based on two postulates for inflationary
theory: one is that inflaton $\phi$ can interact with radiation (relativistic
particles); the other is that radiation will be created continuously during and
after the epoch of inflation. According to these postulates and from a
"macroscopic perspective", we discover that radiation can be viewed as a
product of the interaction between $\dot{\phi}$ and some "effective kinetic
frictional force" that exists in inflaton dynamics. Deducing and surmising from
"effective friction", we obtain conclusions of two special types of expanding
universe: A Type I universe will finally enter an expanding course after a
special time $t_{*}$ with uniformly rolling $\dot{\phi}(t_{*})$ due to the
balance between $V^{'}(\phi(t))$, 3H(t)\dot{\phi}(t_{*}) and the "effective
kinetic frictional force". In this result, the expanding course will see
particles created continuously. Additionally, for a Type II universe, $\phi$
will be at rest after $t_{r}$ inside a region named the "stagnant zone" that is
formed by the "maximum effective static frictional force". Consistent with
this, inflaton potential will survive as a relic $V(\phi(t_{r}))$, playing the
role of the effective cosmological constant $\Lambda$ .
| [
{
"created": "Thu, 29 Sep 2011 18:27:58 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Mar 2012 19:53:19 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Mar 2012 09:02:44 GMT",
"version": "v3"
}
] | 2012-03-07 | [
[
"Chen",
"Yu-Chung",
""
]
] | Recently, we have performed research on the subject of the cosmological constant problem. The scenario is based on two postulates for inflationary theory: one is that inflaton $\phi$ can interact with radiation (relativistic particles); the other is that radiation will be created continuously during and after the epoch of inflation. According to these postulates and from a "macroscopic perspective", we discover that radiation can be viewed as a product of the interaction between $\dot{\phi}$ and some "effective kinetic frictional force" that exists in inflaton dynamics. Deducing and surmising from "effective friction", we obtain conclusions of two special types of expanding universe: A Type I universe will finally enter an expanding course after a special time $t_{*}$ with uniformly rolling $\dot{\phi}(t_{*})$ due to the balance between $V^{'}(\phi(t))$, 3H(t)\dot{\phi}(t_{*}) and the "effective kinetic frictional force". In this result, the expanding course will see particles created continuously. Additionally, for a Type II universe, $\phi$ will be at rest after $t_{r}$ inside a region named the "stagnant zone" that is formed by the "maximum effective static frictional force". Consistent with this, inflaton potential will survive as a relic $V(\phi(t_{r}))$, playing the role of the effective cosmological constant $\Lambda$ . |
2008.04013 | Francisco Lobo | Mahdi Kord Zangeneh, Francisco S. N. Lobo, Hooman Moradpour | Evolving traversable wormholes satisfying the energy conditions in the
presence of pole dark energy | 5 pages, 12 figures. V2: 7 pages, discussion and references added.
V3: 8 pages, further discussion and references added. Version accepted for
publication in Physics of the Dark Universe | Physics of the Dark Universe 31 (2021) 100779 | 10.1016/j.dark.2021.100779 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the evolution of traversable wormhole geometries in the
inflationary, radiation -- and matter -- dominated eras, and dynamic wormholes
with a traceless energy-momentum tensor (EMT), within the recently proposed
{\it pole dark energy} model. We show that the evolving radiation -- and matter
-- dominated wormhole spacetimes satisfy the null energy condition (NEC), but
possess negative energy densities at late times, thus violating the weak energy
condition (WEC) in this specific domain. However, we demonstrate with a
specific example that the traceless EMT evolving wormholes, supported by
conformally invariant massless fields, in principle, could satisfy the WEC, and
consequently the NEC, at all times and for all values of the radial coordinate.
Thus, one may imagine a scenario in which these geometries originate in the
Planckian era through quantum gravitational processes. Inflation could then
provide a natural mechanism for the enlargement of these Planckian wormholes,
where their FLRW background evolution is governed by pole dark energy. For the
first time in the literature, specific dynamical $4$-dimensional solutions are
presented that satisfy the NEC and WEC everywhere and everywhen.
| [
{
"created": "Mon, 10 Aug 2020 10:35:00 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Oct 2020 11:24:18 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Jan 2021 14:58:43 GMT",
"version": "v3"
}
] | 2021-02-01 | [
[
"Zangeneh",
"Mahdi Kord",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Moradpour",
"Hooman",
""
]
] | We consider the evolution of traversable wormhole geometries in the inflationary, radiation -- and matter -- dominated eras, and dynamic wormholes with a traceless energy-momentum tensor (EMT), within the recently proposed {\it pole dark energy} model. We show that the evolving radiation -- and matter -- dominated wormhole spacetimes satisfy the null energy condition (NEC), but possess negative energy densities at late times, thus violating the weak energy condition (WEC) in this specific domain. However, we demonstrate with a specific example that the traceless EMT evolving wormholes, supported by conformally invariant massless fields, in principle, could satisfy the WEC, and consequently the NEC, at all times and for all values of the radial coordinate. Thus, one may imagine a scenario in which these geometries originate in the Planckian era through quantum gravitational processes. Inflation could then provide a natural mechanism for the enlargement of these Planckian wormholes, where their FLRW background evolution is governed by pole dark energy. For the first time in the literature, specific dynamical $4$-dimensional solutions are presented that satisfy the NEC and WEC everywhere and everywhen. |
1705.04107 | Kazuki Sakai | Kazuki Sakai, Ken-ichi Oohara, Hiroyuki Nakano, Masato Kaneyama, and
Hirotaka Takahashi | Estimation of starting times of quasinormal modes in ringdown
gravitational waves with the Hilbert-Huang transform | 12 pages, 12 figures | Phys. Rev. D 96, 044047 (2017) | 10.1103/PhysRevD.96.044047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that a quasinormal mode (QNM) of a remnant black hole dominates a
ringdown gravitational wave (GW) in a binary black hole (BBH) merger. To study
properties of the QNMs, it is important to determine the time when the QNMs
appear in a GW signal as well as to calculate its frequency and amplitude. In
this paper, we propose a new method of estimating the starting time of the QNM
and calculating the QNM frequency and amplitude of BBH GWs. We apply it to
simulated merger waveforms by numerical relativity and the observed data of
GW150914. The results show that the obtained QNM frequencies and time
evolutions of amplitudes are consistent with the theoretical values within 1%
accuracy for pure waveforms free from detector noise. In addition, it is
revealed that there is a correlation between the starting time of the QNM and
the spin of the remnant black hole. In the analysis of GW150914, we show that
the parameters of the remnant black hole estimated through our method are
consistent with those given by LIGO and a reasonable starting time of the QNM
is determined.
| [
{
"created": "Thu, 11 May 2017 10:53:51 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Jul 2017 11:14:59 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Sep 2017 11:22:26 GMT",
"version": "v3"
}
] | 2017-09-06 | [
[
"Sakai",
"Kazuki",
""
],
[
"Oohara",
"Ken-ichi",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Kaneyama",
"Masato",
""
],
[
"Takahashi",
"Hirotaka",
""
]
] | It is known that a quasinormal mode (QNM) of a remnant black hole dominates a ringdown gravitational wave (GW) in a binary black hole (BBH) merger. To study properties of the QNMs, it is important to determine the time when the QNMs appear in a GW signal as well as to calculate its frequency and amplitude. In this paper, we propose a new method of estimating the starting time of the QNM and calculating the QNM frequency and amplitude of BBH GWs. We apply it to simulated merger waveforms by numerical relativity and the observed data of GW150914. The results show that the obtained QNM frequencies and time evolutions of amplitudes are consistent with the theoretical values within 1% accuracy for pure waveforms free from detector noise. In addition, it is revealed that there is a correlation between the starting time of the QNM and the spin of the remnant black hole. In the analysis of GW150914, we show that the parameters of the remnant black hole estimated through our method are consistent with those given by LIGO and a reasonable starting time of the QNM is determined. |
gr-qc/0001051 | Yasunori Fujii | Yasunori Fujii | Cosmological Constant, Quintessence and Scalar-Tensor Theories of
Gravity | 11 pages including 3 figures. Delivered at The Ninth Workshop on
General Relativity and Gravitation, Hiroshima University, Nov. 3--6, 1999:
International Seminar Nara 99, Space, Time and Interactions, Nara Women's
University, December 4--5, 1999. To appear in Proceedings: Added footnote and
references | Grav.Cosmol. 6 (2000) 107-115 | null | null | gr-qc | null | We show how the scalar field, a candidate of quintessence, in a proposed
model of the scalar-tensor theories of gravity provides a way to understand a
small but nonzero cosmological constant as indicated by recent observations. A
particular emphasis is placed on the effort to inherit the success of the
scenario of a decaying cosmological constant. Discussions of a possible link to
non-Newtonian gravity, the coincidence problem, the issue of time-variability
of coupling constants as well as the chaos-like nature of the solution are also
included in a new perspective.
| [
{
"created": "Wed, 19 Jan 2000 10:22:23 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Feb 2000 06:25:32 GMT",
"version": "v2"
}
] | 2009-09-25 | [
[
"Fujii",
"Yasunori",
""
]
] | We show how the scalar field, a candidate of quintessence, in a proposed model of the scalar-tensor theories of gravity provides a way to understand a small but nonzero cosmological constant as indicated by recent observations. A particular emphasis is placed on the effort to inherit the success of the scenario of a decaying cosmological constant. Discussions of a possible link to non-Newtonian gravity, the coincidence problem, the issue of time-variability of coupling constants as well as the chaos-like nature of the solution are also included in a new perspective. |
gr-qc/0312054 | Mariano Cadoni | Mariano Cadoni | An Einstein-like theory of gravity with a non-newtonian weak-field limit | Final version, accepted for publication on General Relativity and
Gravitation | Gen.Rel.Grav.36:2681-2688,2004 | 10.1023/B:GERG.0000048982.05514.18 | INFNCA-TH0305 | gr-qc astro-ph | null | We propose a model describing Einstein gravity coupled to a scalar field with
an exponential potential. We show that the weak-field limit of the model has
static solutions given by a gravitational potential behaving for large
distances as \ln r . The Newtonian term GM/r appears only as subleading. Our
model can be used to give a phenomenological explanation of the rotation curves
of the galaxies without postulating the presence of dark matter. This can be
achieved only by giving up at galactic scales Einstein equivalence principle.
| [
{
"created": "Tue, 9 Dec 2003 16:19:00 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Dec 2003 11:27:20 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Sep 2004 14:15:09 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Cadoni",
"Mariano",
""
]
] | We propose a model describing Einstein gravity coupled to a scalar field with an exponential potential. We show that the weak-field limit of the model has static solutions given by a gravitational potential behaving for large distances as \ln r . The Newtonian term GM/r appears only as subleading. Our model can be used to give a phenomenological explanation of the rotation curves of the galaxies without postulating the presence of dark matter. This can be achieved only by giving up at galactic scales Einstein equivalence principle. |
2010.03683 | Shahar Hadar | Shahar Hadar, Michael D. Johnson, Alexandru Lupsasca, George N. Wong | Photon Ring Autocorrelations | 31 pages, 3 figures. v2: published version. v3: minor corrections,
summarized in an appendix; conclusions essentially unchanged | Phys. Rev. D 103, 104038 (2021) | 10.1103/PhysRevD.103.104038 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the presence of a black hole, light sources connect to observers along
multiple paths. As a result, observed brightness fluctuations must be
correlated across different times and positions in black hole images. Photons
that execute multiple orbits around the black hole appear near a critical curve
in the observer sky, giving rise to the photon ring. In this paper, a novel
observable is proposed: the two-point correlation function of intensity
fluctuations on the photon ring. This correlation function is analytically
computed for a Kerr black hole surrounded by stochastic equatorial emission,
with source statistics motivated by simulations of a turbulent accretion flow.
It is shown that this two-point function exhibits a universal, self-similar
structure consisting of multiple peaks of identical shape: while the profile of
each peak encodes statistical properties of fluctuations in the source, the
locations and heights of the peaks are determined purely by the black hole
parameters. Measuring these peaks would demonstrate the existence of the photon
ring without resolving its thickness, and would provide estimates of black hole
mass and spin. With regular monitoring over sufficiently long timescales, this
measurement could be possible via interferometric imaging with modest
improvements to the Event Horizon Telescope.
| [
{
"created": "Wed, 7 Oct 2020 22:56:50 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Apr 2021 16:24:18 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Jun 2023 12:21:02 GMT",
"version": "v3"
}
] | 2023-06-21 | [
[
"Hadar",
"Shahar",
""
],
[
"Johnson",
"Michael D.",
""
],
[
"Lupsasca",
"Alexandru",
""
],
[
"Wong",
"George N.",
""
]
] | In the presence of a black hole, light sources connect to observers along multiple paths. As a result, observed brightness fluctuations must be correlated across different times and positions in black hole images. Photons that execute multiple orbits around the black hole appear near a critical curve in the observer sky, giving rise to the photon ring. In this paper, a novel observable is proposed: the two-point correlation function of intensity fluctuations on the photon ring. This correlation function is analytically computed for a Kerr black hole surrounded by stochastic equatorial emission, with source statistics motivated by simulations of a turbulent accretion flow. It is shown that this two-point function exhibits a universal, self-similar structure consisting of multiple peaks of identical shape: while the profile of each peak encodes statistical properties of fluctuations in the source, the locations and heights of the peaks are determined purely by the black hole parameters. Measuring these peaks would demonstrate the existence of the photon ring without resolving its thickness, and would provide estimates of black hole mass and spin. With regular monitoring over sufficiently long timescales, this measurement could be possible via interferometric imaging with modest improvements to the Event Horizon Telescope. |
2405.08680 | Manabendra Sharma | Gaurav Bhandari, S. D. Pathak, Manabendra Sharma and Anzhong Wang | Generalized uncertainty principle distorted quintessence dynamics | 12. arXiv admin note: text overlap with arXiv:2404.09049 | null | null | null | gr-qc hep-th math-ph math.MP quant-ph | http://creativecommons.org/licenses/by/4.0/ | In this paper, we invoke a generalized uncertainty principle (GUP) in the
symmetry-reduced cosmological Hamiltonian for a universe driven by a
quintessence scalar field with potential. Our study focuses on semi-classical
regime. In particular, we derive the GUP-distorted Friedmann, Raychaudhuri, and
the Klein-Gordon equation. This is followed by a systematic analysis of the
qualitative dynamics for the choice of potential $V(\phi)= V_0 \sinh^{-n}{(\mu
\phi)}$. This involves constructing an autonomous dynamical system of equations
by choosing appropriate dynamical variables, followed by a qualitative study
using linear stability theory. Our analysis shows that incorporating GUP
significantly changes the existing fixed points compared to the limiting case
without quantum effects by switching off the GUP.
| [
{
"created": "Tue, 14 May 2024 15:03:06 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Bhandari",
"Gaurav",
""
],
[
"Pathak",
"S. D.",
""
],
[
"Sharma",
"Manabendra",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this paper, we invoke a generalized uncertainty principle (GUP) in the symmetry-reduced cosmological Hamiltonian for a universe driven by a quintessence scalar field with potential. Our study focuses on semi-classical regime. In particular, we derive the GUP-distorted Friedmann, Raychaudhuri, and the Klein-Gordon equation. This is followed by a systematic analysis of the qualitative dynamics for the choice of potential $V(\phi)= V_0 \sinh^{-n}{(\mu \phi)}$. This involves constructing an autonomous dynamical system of equations by choosing appropriate dynamical variables, followed by a qualitative study using linear stability theory. Our analysis shows that incorporating GUP significantly changes the existing fixed points compared to the limiting case without quantum effects by switching off the GUP. |
1905.05995 | Khalid Saifullah | Mudassar Rehman and Khalid Saifullah | Unified first law for traversable wormholes in non-minimal coupling of
curvature and matter | null | Annals of Physics 407 (2019) 57 | 10.1016/j.aop.2019.04.014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper thermodynamics of static Morris-Thorne wormholes has been
discussed in the context of $f(R)$ gravity. The generalized surface gravity,
unified first law of thermodynamics and wormhole dynamics have been studied at
trapping horizons. We have investigated thermodynamics in non-minimal coupling
of curvature and matter which produces very complex equations. Our results
generalize the results that have already been derived in Einstein's gravity in
the absence of curvature-matter coupling.
| [
{
"created": "Wed, 15 May 2019 07:34:23 GMT",
"version": "v1"
}
] | 2019-05-16 | [
[
"Rehman",
"Mudassar",
""
],
[
"Saifullah",
"Khalid",
""
]
] | In this paper thermodynamics of static Morris-Thorne wormholes has been discussed in the context of $f(R)$ gravity. The generalized surface gravity, unified first law of thermodynamics and wormhole dynamics have been studied at trapping horizons. We have investigated thermodynamics in non-minimal coupling of curvature and matter which produces very complex equations. Our results generalize the results that have already been derived in Einstein's gravity in the absence of curvature-matter coupling. |
2211.10612 | Mohaddeseh Seifi | Mohaddeseh Seifi and Akram S. Sefiedgar | Thermodynamics of Horndeski Black Holes with Generalized Uncertainty
Principle | 17pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Horndeski theory is the most general scalar-tensor extension of General
Relativity with second order field equations. It may be interesting to study
the effects of the Generalized Uncertainty Principle on a static and
asymptotically flat shift symmetric solutions of the Horndeski black holes.
With this motivation, here we obtain the modified black hole temperatures in
shift symmetric Horndeski gravity by employing the Generalized Uncertainty
Principle. Using the corrected temperature, the entropy and heat capacity are
calculated with details. We also investigate the tunneling probability of
particles from Horndeski black holes horizon and possible correlations between
the emitted modes (particles).
| [
{
"created": "Sat, 19 Nov 2022 08:09:28 GMT",
"version": "v1"
}
] | 2022-11-22 | [
[
"Seifi",
"Mohaddeseh",
""
],
[
"Sefiedgar",
"Akram S.",
""
]
] | Horndeski theory is the most general scalar-tensor extension of General Relativity with second order field equations. It may be interesting to study the effects of the Generalized Uncertainty Principle on a static and asymptotically flat shift symmetric solutions of the Horndeski black holes. With this motivation, here we obtain the modified black hole temperatures in shift symmetric Horndeski gravity by employing the Generalized Uncertainty Principle. Using the corrected temperature, the entropy and heat capacity are calculated with details. We also investigate the tunneling probability of particles from Horndeski black holes horizon and possible correlations between the emitted modes (particles). |
0907.3311 | Roman Kezerashvili | Roman Ya. Kezerashvili and Justin F. Vazquez-Poritz | Deviations from Keplerian Orbits for Solar Sails | 6 pages, 2 figures. Proceedings of the Sixth IAA Symposium on
Realistic Near-Term Advanced Scientific Space Missions. Missions to the Outer
Solar System and Beyond, pp. 37- 42, Aosta, Italy, 6-9 July, 2009 | null | null | null | gr-qc physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the curvature of spacetime, a possible net electric charge
on the sun, a small positive cosmological constant and the oblateness of the
sun, in conjunction with solar radiation pressure (SPR), affect the bound
orbital motion of solar sails and lead to deviations from Kepler's third law
for heliocentric and non-Keplerian orbits. With regards to the Lense-Thirring
effect, the SRP increases the amount of precession per orbit for polar orbits.
Non-Keplerian polar orbits exhibit an analog of the Lense-Thirring effect in
which the orbital plane precesses around the sun.
| [
{
"created": "Mon, 20 Jul 2009 01:28:31 GMT",
"version": "v1"
}
] | 2009-08-17 | [
[
"Kezerashvili",
"Roman Ya.",
""
],
[
"Vazquez-Poritz",
"Justin F.",
""
]
] | It is shown that the curvature of spacetime, a possible net electric charge on the sun, a small positive cosmological constant and the oblateness of the sun, in conjunction with solar radiation pressure (SPR), affect the bound orbital motion of solar sails and lead to deviations from Kepler's third law for heliocentric and non-Keplerian orbits. With regards to the Lense-Thirring effect, the SRP increases the amount of precession per orbit for polar orbits. Non-Keplerian polar orbits exhibit an analog of the Lense-Thirring effect in which the orbital plane precesses around the sun. |
1602.01041 | Anton Stupka | A. A. Stupka | Gravitation Field Dynamics in Jeans Theory | Time equations; Jeans theory; Bogolyubov reduced description method;
perturbation types.
http://www.ias.ac.in/article/fulltext/joaa/029/03-04/0379-0386 | Journal of Astrophysics and Astronomy, Volume 29 Issue 3-4
September-December 2008 pp 379-386 | 10.1007/s12036-008-0050-x | null | gr-qc astro-ph.GA cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Closed system of time equations for nonrelativistic gravitation field and
hydrodynamic medium was obtained by taking into account binary correlations of
the field, which is the generalization of Jeans theory. Distribution function
of the systemwas built on the basis of the Bogolyubov reduced description
method. Calculations were carried out up to the first order of a perturbation
theory in interaction. Adiabatic and enthropic types of perturbations were
corrected and two new types of perturbations were found.
| [
{
"created": "Tue, 2 Feb 2016 18:51:33 GMT",
"version": "v1"
}
] | 2016-02-10 | [
[
"Stupka",
"A. A.",
""
]
] | Closed system of time equations for nonrelativistic gravitation field and hydrodynamic medium was obtained by taking into account binary correlations of the field, which is the generalization of Jeans theory. Distribution function of the systemwas built on the basis of the Bogolyubov reduced description method. Calculations were carried out up to the first order of a perturbation theory in interaction. Adiabatic and enthropic types of perturbations were corrected and two new types of perturbations were found. |
1105.6228 | Muhammad Sharif | M. Sharif and Shamaila Rani | F(T) Models within Bianchi Type I Universe | 19 pages, accepted for publication in Mod. Phys. Lett. A | Mod. Phys. Lett. A26 (2011)1657-1671 | 10.1142/S0217732311036127 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider spatially homogenous and anisotropic Bianchi type
I universe in the context of F(T) gravity. We construct some corresponding
models using conservation equation and equation of state parameter representing
different phases of the universe. In particular, we take matter dominated era,
radiation dominated era, present dark energy phase and their combinations. It
is found that one of the models has a constant solution which may correspond to
the cosmological constant. We also derive equation of state parameter by using
two well-known F(T) models and discuss cosmic acceleration.
| [
{
"created": "Tue, 31 May 2011 09:55:22 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Sharif",
"M.",
""
],
[
"Rani",
"Shamaila",
""
]
] | In this paper, we consider spatially homogenous and anisotropic Bianchi type I universe in the context of F(T) gravity. We construct some corresponding models using conservation equation and equation of state parameter representing different phases of the universe. In particular, we take matter dominated era, radiation dominated era, present dark energy phase and their combinations. It is found that one of the models has a constant solution which may correspond to the cosmological constant. We also derive equation of state parameter by using two well-known F(T) models and discuss cosmic acceleration. |
2408.04402 | Foad Parsaei | Sara Rastgoo and Foad Parsaei | Wormholes in $f(R,T)$ gravity with variable equation of state | 11 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this work, we introduce a novel set of asymptotically flat wormhole
solutions within the framework of $f(R,T)$ theory of gravity. Considering a
linear
$f(R,T)=R+ 2\lambda T$ form, we show that a wide variety of wormhole
solutions with asymptotically linear equation of state exist. Our solutions
satisfy all the energy conditions, namely the null, weak, strong and dominant
energy conditions. The relationship between free parameters in the shape
function and boundary conditions is analyzed.
| [
{
"created": "Thu, 8 Aug 2024 12:10:07 GMT",
"version": "v1"
}
] | 2024-08-09 | [
[
"Rastgoo",
"Sara",
""
],
[
"Parsaei",
"Foad",
""
]
] | In this work, we introduce a novel set of asymptotically flat wormhole solutions within the framework of $f(R,T)$ theory of gravity. Considering a linear $f(R,T)=R+ 2\lambda T$ form, we show that a wide variety of wormhole solutions with asymptotically linear equation of state exist. Our solutions satisfy all the energy conditions, namely the null, weak, strong and dominant energy conditions. The relationship between free parameters in the shape function and boundary conditions is analyzed. |
2306.06911 | Ayanendu Dutta | Ayanendu Dutta, Dhritimalya Roy, Nihal Jalal Pullisseri, and Subenoy
Chakraborty | Wormhole formation in massive gravity: An analytic description | 13 pages, 6 figures, 1 table. Few typos are corrected from the
previous version | Eur. Phys. J. C 83 (6), 500 (2023) | 10.1140/epjc/s10052-023-11681-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present study analyses the wormhole solution both in the dRGT-$ f(R,T) $
massive gravity and Einstein massive gravity. In both the models, the
anisotropic pressure solution in ultrastatic wormhole geometry gives rise to
the shape function that involves massive gravity parameters $ \gamma $ and $
\Lambda $. However, the terms consisting of $ \gamma $ and $ \Lambda $ acts in
such a way that the spacetime loses asymptotic flatness. Similar to the black
hole solution in massive gravity, this inconsistency arises due to the
repulsive effect of gravity which can be represented by the photon deflection
angle that goes negative after a certain radial distance. It is investigated
that the repulsive effect induced in the massive gravitons push the spacetime
geometry so strongly that the asymptotic flatness is effected. On the other
hand, in this model, one can have a wormhole with ordinary matter at the throat
that satisfies all the energy conditions while the negative energy density is
sourced by massive gravitons. Finally, using the TOV equation, it is found that
the model is stable under the hydrostatic equilibrium condition.
| [
{
"created": "Mon, 12 Jun 2023 07:33:20 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jul 2024 13:15:50 GMT",
"version": "v2"
}
] | 2024-07-02 | [
[
"Dutta",
"Ayanendu",
""
],
[
"Roy",
"Dhritimalya",
""
],
[
"Pullisseri",
"Nihal Jalal",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present study analyses the wormhole solution both in the dRGT-$ f(R,T) $ massive gravity and Einstein massive gravity. In both the models, the anisotropic pressure solution in ultrastatic wormhole geometry gives rise to the shape function that involves massive gravity parameters $ \gamma $ and $ \Lambda $. However, the terms consisting of $ \gamma $ and $ \Lambda $ acts in such a way that the spacetime loses asymptotic flatness. Similar to the black hole solution in massive gravity, this inconsistency arises due to the repulsive effect of gravity which can be represented by the photon deflection angle that goes negative after a certain radial distance. It is investigated that the repulsive effect induced in the massive gravitons push the spacetime geometry so strongly that the asymptotic flatness is effected. On the other hand, in this model, one can have a wormhole with ordinary matter at the throat that satisfies all the energy conditions while the negative energy density is sourced by massive gravitons. Finally, using the TOV equation, it is found that the model is stable under the hydrostatic equilibrium condition. |
gr-qc/0408053 | Alan D. Rendall | Alan D. Rendall | Mathematical properties of cosmological models with accelerated
expansion | Based on a lecture given at Bad Honnef | Lect.Notes Phys. 692 (2006) 141-155 | 10.1007/11550259_7 | AEI-2004-061 | gr-qc | null | An introduction to solutions of the Einstein equations defining cosmological
models with accelerated expansion is given. Connections between mathematical
and physical issues are explored. Theorems which have been proved for solutions
with positive cosmological constant or nonlinear scalar fields are reviewed.
Some remarks are made on more exotic models such as the Chaplygin gas, tachyons
and $k$-essence.
| [
{
"created": "Tue, 17 Aug 2004 12:08:47 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Rendall",
"Alan D.",
""
]
] | An introduction to solutions of the Einstein equations defining cosmological models with accelerated expansion is given. Connections between mathematical and physical issues are explored. Theorems which have been proved for solutions with positive cosmological constant or nonlinear scalar fields are reviewed. Some remarks are made on more exotic models such as the Chaplygin gas, tachyons and $k$-essence. |
1906.05749 | Genly Le\'on | Genly Leon, A. Coley, Andronikos Paliathanasis | Static Spherically Symmetric Einstein-aether models II: Integrability
and the Modified Tolman-Oppenheimer-Volkoff approach | 85 pages, 18 compound figures, first revision, references and
discussion added | null | 10.1016/j.aop.2019.168002 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the existence of analytic solutions for the field equations in
the Einstein-\ae ther theory for a static spherically symmetric spacetime and
provide a detailed dynamical system analysis of the field equations. In
particular, we investigate if the gravitational field equations in the
Einstein-\ae ther model in the static spherically symmetric spacetime possesses
the Painlev\`e property, so that an analytic explicit integration can be
performed. We find that analytic solutions can be presented in terms of Laurent
expansion only when the matter source consists of a perfect fluid with linear
equation of state (EoS) $\mu =\mu _{0}+\left( \texttt{h} -1\right)
p,~\texttt{h} >1$. In order to study the field equations we apply the
Tolman-Oppenheimer-Volkoff (TOV) approach and other approaches. We find that
the relativistic TOV equations are drastically modified in Einstein-\ae ther
theory, and we explore the physical implications of this modification. We study
perfect fluid models with a scalar field with an exponential potential. We
discuss all of the equilibrium points and discuss their physical properties.
| [
{
"created": "Thu, 13 Jun 2019 15:17:11 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Aug 2019 04:49:28 GMT",
"version": "v2"
}
] | 2020-01-08 | [
[
"Leon",
"Genly",
""
],
[
"Coley",
"A.",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | We investigate the existence of analytic solutions for the field equations in the Einstein-\ae ther theory for a static spherically symmetric spacetime and provide a detailed dynamical system analysis of the field equations. In particular, we investigate if the gravitational field equations in the Einstein-\ae ther model in the static spherically symmetric spacetime possesses the Painlev\`e property, so that an analytic explicit integration can be performed. We find that analytic solutions can be presented in terms of Laurent expansion only when the matter source consists of a perfect fluid with linear equation of state (EoS) $\mu =\mu _{0}+\left( \texttt{h} -1\right) p,~\texttt{h} >1$. In order to study the field equations we apply the Tolman-Oppenheimer-Volkoff (TOV) approach and other approaches. We find that the relativistic TOV equations are drastically modified in Einstein-\ae ther theory, and we explore the physical implications of this modification. We study perfect fluid models with a scalar field with an exponential potential. We discuss all of the equilibrium points and discuss their physical properties. |
2001.03943 | Ulf Leonhardt | Ulf Leonhardt | The case for a Casimir cosmology | Discussion paper for lecture at
https://royalsociety.org/science-events-and-lectures/2019/12/analogue-gravity/ | null | 10.1098/rsta.2019.0229 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological constant, also known as dark energy, was believed to be
caused by vacuum fluctuations, but naive calculations give results in stark
disagreement with fact. In the Casimir effect, vacuum fluctuations cause forces
in dielectric media, which is very well described by Lifshitz theory. Recently,
using the analogy between geometries and media, a cosmological constant of the
correct order of magnitude was calculated with Lifshitz theory [U. Leonhardt,
Ann. Phys. (New York) 411, 167973 (2019)]. This paper discusses the empirical
evidence and the ideas behind the Lifshitz theory of the cosmological constant
without requiring prior knowledge of cosmology and quantum field theory.
| [
{
"created": "Sun, 12 Jan 2020 15:04:45 GMT",
"version": "v1"
}
] | 2021-03-03 | [
[
"Leonhardt",
"Ulf",
""
]
] | The cosmological constant, also known as dark energy, was believed to be caused by vacuum fluctuations, but naive calculations give results in stark disagreement with fact. In the Casimir effect, vacuum fluctuations cause forces in dielectric media, which is very well described by Lifshitz theory. Recently, using the analogy between geometries and media, a cosmological constant of the correct order of magnitude was calculated with Lifshitz theory [U. Leonhardt, Ann. Phys. (New York) 411, 167973 (2019)]. This paper discusses the empirical evidence and the ideas behind the Lifshitz theory of the cosmological constant without requiring prior knowledge of cosmology and quantum field theory. |
2101.00654 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Comparing $f(R)$ modified gravity and noncommutative geometry in the
context of dark matter and traversable wormholes: a survey | 9 pages, no figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Noncommutative geometry, as conceptualized by Nicolini, Smailagic, and
Spallucci, may be viewed as a slight modification of Einstein's theory. The
same can be said for $f(R)$ modified gravity for an appropriate choice of the
function $f(R)$. Since such an $f(R)$ could be determined from the
noncommutative-geometry background, these gravitational theories make very
similar predictions in the discussion of (a) dark matter and (b) traversable
wormholes; they can therefore be taken as equally viable models.
| [
{
"created": "Sun, 3 Jan 2021 16:25:07 GMT",
"version": "v1"
}
] | 2021-01-05 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | Noncommutative geometry, as conceptualized by Nicolini, Smailagic, and Spallucci, may be viewed as a slight modification of Einstein's theory. The same can be said for $f(R)$ modified gravity for an appropriate choice of the function $f(R)$. Since such an $f(R)$ could be determined from the noncommutative-geometry background, these gravitational theories make very similar predictions in the discussion of (a) dark matter and (b) traversable wormholes; they can therefore be taken as equally viable models. |
1801.01966 | Tomohiro Harada | Tomohiro Harada, B. J. Carr, Takahisa Igata | Complete conformal classification of the
Friedmann-Lemaitre-Robertson-Walker solutions with a linear equation of state | 37 pages, 8 figures, minor correction, accepted for publication in
Classical and Quantum Gravity | null | 10.1088/1361-6382/aab99f | RUP-17-27 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We completely classify Friedmann-Lema\^{i}tre-Robertson-Walker solutions with
spatial curvature $K=0,\pm 1$ and equation of state $p=w\rho$, according to
their conformal structure, singularities and trapping horizons. We do not
assume any energy conditions and allow $\rho < 0$, thereby going beyond the
usual well-known solutions. For each spatial curvature, there is an initial
spacelike big-bang singularity for $w>-1/3$ and $\rho>0$, while no big-bang
singularity for $w<-1$ and $\rho>0$. For $K=0$ or $-1$, $-1<w<-1/3$ and
$\rho>0$, there is an initial null big-bang singularity. For each spatial
curvature, there is a final spacelike future big-rip singularity for $w<-1$ and
$\rho>0$, with null geodesics being future complete for $-5/3\le w<-1$ but
incomplete for $w<-5/3$. For $w=-1/3$, the expansion speed is constant. For
$-1<w<-1/3$ and $K=1$, the universe contracts from infinity, then bounces and
expands back to infinity. For $K=0$, the past boundary consists of timelike
infinity and a regular null hypersurface for $-5/3<w<-1$, while it consists of
past timelike and past null infinities for $w\le -5/3$. For $w<-1$ and $K=1$,
the spacetime contracts from an initial spacelike past big-rip singularity,
then bounces and blows up at a final spacelike future big-rip singularity. For
$w<-1$ and $K=-1$, the past boundary consists of a regular null hypersurface.
The trapping horizons are timelike, null and spacelike for $w\in (-1,1/3)$,
$w\in \{1/3, -1\}$ and $w\in (-\infty,-1)\cup (1/3,\infty)$, respectively. A
negative energy density ($\rho <0$) is possible only for $K=-1$. In this case,
for $w>-1/3$, the universe contracts from infinity, then bounces and expands to
infinity; for $-1<w<-1/3$, it starts from a big-bang singularity and contracts
to a big-crunch singularity; for $w<-1$, it expands from a regular null
hypersurface and contracts to another regular null hypersurface.
| [
{
"created": "Sat, 6 Jan 2018 04:52:28 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Mar 2018 06:00:41 GMT",
"version": "v2"
}
] | 2018-05-02 | [
[
"Harada",
"Tomohiro",
""
],
[
"Carr",
"B. J.",
""
],
[
"Igata",
"Takahisa",
""
]
] | We completely classify Friedmann-Lema\^{i}tre-Robertson-Walker solutions with spatial curvature $K=0,\pm 1$ and equation of state $p=w\rho$, according to their conformal structure, singularities and trapping horizons. We do not assume any energy conditions and allow $\rho < 0$, thereby going beyond the usual well-known solutions. For each spatial curvature, there is an initial spacelike big-bang singularity for $w>-1/3$ and $\rho>0$, while no big-bang singularity for $w<-1$ and $\rho>0$. For $K=0$ or $-1$, $-1<w<-1/3$ and $\rho>0$, there is an initial null big-bang singularity. For each spatial curvature, there is a final spacelike future big-rip singularity for $w<-1$ and $\rho>0$, with null geodesics being future complete for $-5/3\le w<-1$ but incomplete for $w<-5/3$. For $w=-1/3$, the expansion speed is constant. For $-1<w<-1/3$ and $K=1$, the universe contracts from infinity, then bounces and expands back to infinity. For $K=0$, the past boundary consists of timelike infinity and a regular null hypersurface for $-5/3<w<-1$, while it consists of past timelike and past null infinities for $w\le -5/3$. For $w<-1$ and $K=1$, the spacetime contracts from an initial spacelike past big-rip singularity, then bounces and blows up at a final spacelike future big-rip singularity. For $w<-1$ and $K=-1$, the past boundary consists of a regular null hypersurface. The trapping horizons are timelike, null and spacelike for $w\in (-1,1/3)$, $w\in \{1/3, -1\}$ and $w\in (-\infty,-1)\cup (1/3,\infty)$, respectively. A negative energy density ($\rho <0$) is possible only for $K=-1$. In this case, for $w>-1/3$, the universe contracts from infinity, then bounces and expands to infinity; for $-1<w<-1/3$, it starts from a big-bang singularity and contracts to a big-crunch singularity; for $w<-1$, it expands from a regular null hypersurface and contracts to another regular null hypersurface. |
2106.14761 | Soumya Chakrabarti | Soumya Chakrabarti (Saha Institute of Nuclear Physics, Kolkata) and
Sayan Kar (IIT Kharagpur) | A wormhole geometry from gravitational collapse | 14 Pages, 8 Figures, Accepted for publication in Physical Review D | null | 10.1103/PhysRevD.104.024071 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a proposal on how gravitational collapse of a NEC (Null Energy
Condition) violating spherically symmetric fluid distribution can avoid the
formation of a zero proper volume singularity and eventually lead to a
Lorentzian wormhole geometry. Our idea is illustrated using a time-evolving
wormhole spacetime in which, we show how a collapsing sphere may never reach a
zero proper volume end-state. The nature of geodesic congruences in such
spacetimes is considered and analyzed. Our construction is inspired from a
recently proposed static wormhole geometry, the multi-parameter Simpson-Visser
line element, which is known to unite wormholes and black holes (regular and
singular) in a single framework.
| [
{
"created": "Mon, 28 Jun 2021 14:35:50 GMT",
"version": "v1"
}
] | 2021-08-11 | [
[
"Chakrabarti",
"Soumya",
"",
"Saha Institute of Nuclear Physics, Kolkata"
],
[
"Kar",
"Sayan",
"",
"IIT Kharagpur"
]
] | We discuss a proposal on how gravitational collapse of a NEC (Null Energy Condition) violating spherically symmetric fluid distribution can avoid the formation of a zero proper volume singularity and eventually lead to a Lorentzian wormhole geometry. Our idea is illustrated using a time-evolving wormhole spacetime in which, we show how a collapsing sphere may never reach a zero proper volume end-state. The nature of geodesic congruences in such spacetimes is considered and analyzed. Our construction is inspired from a recently proposed static wormhole geometry, the multi-parameter Simpson-Visser line element, which is known to unite wormholes and black holes (regular and singular) in a single framework. |
gr-qc/9602051 | Russell Cosgrove | R. Cosgrove | A Single Particle Interpretation of Relativistic Quantum Mechanics | 13 pages, LaTeX, no figures | null | null | null | gr-qc quant-ph | null | The relativistic free particle system in 1+1 dimensions is formulated as a
``bi-Hamiltonian system''. One Hamiltonian generates ordinary time
translations, and another generates (essentially) boosts. Any observer,
accelerated or not, sees evolution as the continuous unfolding of a canonical
transformation which may be described using the two Hamiltonians. When the
system is quantized both Hamiltonians become Hermitian operators in the
standard positive definite inner product. Hence, each observer sees the
evolution of the wave function as the continuous unfolding of a unitary
transformation in the standard positive definite inner product. The result
appears to be a consistent single particle interpretation of relativistic
quantum mechanics. This interpretation has the feature that the wave function
is observer dependent, and observables have non-local character, similar to
what one might expect in quantum gravity.
| [
{
"created": "Tue, 27 Feb 1996 01:47:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cosgrove",
"R.",
""
]
] | The relativistic free particle system in 1+1 dimensions is formulated as a ``bi-Hamiltonian system''. One Hamiltonian generates ordinary time translations, and another generates (essentially) boosts. Any observer, accelerated or not, sees evolution as the continuous unfolding of a canonical transformation which may be described using the two Hamiltonians. When the system is quantized both Hamiltonians become Hermitian operators in the standard positive definite inner product. Hence, each observer sees the evolution of the wave function as the continuous unfolding of a unitary transformation in the standard positive definite inner product. The result appears to be a consistent single particle interpretation of relativistic quantum mechanics. This interpretation has the feature that the wave function is observer dependent, and observables have non-local character, similar to what one might expect in quantum gravity. |
1001.1961 | J. Ponce de Leon | J. Ponce de Leon | Brans-Dicke Cosmology in 4D from scalar-vacuum in 5D | A typo in equation (4) is fixed. Accepted for publication in J.
Cosmol. Astropart. Phys. (JCAP) | JCAP 1003:030,2010 | 10.1088/1475-7516/2010/03/030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Brans-Dicke (BD) theory in 5D may explain the present cosmic
accelerated expansion without recurring to matter fields in 5D or dark energy
in 4D. Without making any assumption on the nature of the extra coordinate or
the matter content in 5D, here we demonstrate that the vacuum BD field
equations in 5D are equivalent, on every hypersurface orthogonal to the extra
dimension, to a BD theory in 4D with a self interacting potential and an
effective matter field. The potential is not introduced by hand, instead the
reduction procedure provides an expression that determines its shape up to a
constant of integration. It also establishes the explicit formulae for the
effective matter in 4D. In the context of FRW cosmologies, we show that the
reduced BD theory gives rise to models for accelerated expansion of a
matter-dominated universe which are consistent with current observations and
with a decelerating radiation-dominated epoch.
| [
{
"created": "Tue, 12 Jan 2010 18:01:36 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Mar 2010 12:27:05 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"de Leon",
"J. Ponce",
""
]
] | We show that Brans-Dicke (BD) theory in 5D may explain the present cosmic accelerated expansion without recurring to matter fields in 5D or dark energy in 4D. Without making any assumption on the nature of the extra coordinate or the matter content in 5D, here we demonstrate that the vacuum BD field equations in 5D are equivalent, on every hypersurface orthogonal to the extra dimension, to a BD theory in 4D with a self interacting potential and an effective matter field. The potential is not introduced by hand, instead the reduction procedure provides an expression that determines its shape up to a constant of integration. It also establishes the explicit formulae for the effective matter in 4D. In the context of FRW cosmologies, we show that the reduced BD theory gives rise to models for accelerated expansion of a matter-dominated universe which are consistent with current observations and with a decelerating radiation-dominated epoch. |
gr-qc/0506128 | Martin Bojowald | Martin Bojowald | Nonsingular Black Holes and Degrees of Freedom in Quantum Gravity | 4 pages | Phys.Rev.Lett.95:061301,2005 | 10.1103/PhysRevLett.95.061301 | AEI-2005-115 | gr-qc hep-th | null | Spherically symmetric space-times provide many examples for interesting black
hole solutions, which classically are all singular. Following a general
program, space-like singularities in spherically symmetric quantum geometry, as
well as other inhomogeneous models, are shown to be absent. Moreover, one sees
how the classical reduction from infinitely many kinematical degrees of freedom
to only one physical one, the mass, can arise, where aspects of quantum
cosmology such as the problem of initial conditions play a role.
| [
{
"created": "Tue, 28 Jun 2005 12:51:48 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Bojowald",
"Martin",
""
]
] | Spherically symmetric space-times provide many examples for interesting black hole solutions, which classically are all singular. Following a general program, space-like singularities in spherically symmetric quantum geometry, as well as other inhomogeneous models, are shown to be absent. Moreover, one sees how the classical reduction from infinitely many kinematical degrees of freedom to only one physical one, the mass, can arise, where aspects of quantum cosmology such as the problem of initial conditions play a role. |
2405.13544 | Iarley P. Lobo Dr | Gislaine Var\~ao, Iarley P. Lobo, Valdir B. Bezerra | Fractional quantum mechanics meets quantum gravity phenomenology | 9 pages, 2 figures | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | This paper extends previous findings on the modified Schr\"odinger evolution
inspired by quantum gravity phenomenology. By establishing a connection between
this approach and fractional quantum mechanics, we provide insights into a
potential deep infrared regime of quantum gravity, characterized by the
emergence of fractal dimensions, similar to behaviors observed in the deep
ultraviolet regime. Additionally, we briefly explore the requirements for
experimental investigations of this regime using Bose-Einstein condensates.
Notably, our analysis reveals a direct implication of this analogy: experiments
probing fractional quantum mechanics may serve as equivalent models of quantum
gravity. We identify instances of nonlocal behavior in such systems, suggesting
an analogous phenomenon of nonlocality in quantum gravity.
| [
{
"created": "Wed, 22 May 2024 11:28:22 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Varão",
"Gislaine",
""
],
[
"Lobo",
"Iarley P.",
""
],
[
"Bezerra",
"Valdir B.",
""
]
] | This paper extends previous findings on the modified Schr\"odinger evolution inspired by quantum gravity phenomenology. By establishing a connection between this approach and fractional quantum mechanics, we provide insights into a potential deep infrared regime of quantum gravity, characterized by the emergence of fractal dimensions, similar to behaviors observed in the deep ultraviolet regime. Additionally, we briefly explore the requirements for experimental investigations of this regime using Bose-Einstein condensates. Notably, our analysis reveals a direct implication of this analogy: experiments probing fractional quantum mechanics may serve as equivalent models of quantum gravity. We identify instances of nonlocal behavior in such systems, suggesting an analogous phenomenon of nonlocality in quantum gravity. |
1602.06436 | Jesper M{\o}ller Grimstrup | Johannes Aastrup and Jesper M. Grimstrup | On a Lattice-Independent Formulation of Quantum Holonomy Theory | 22 pages, 1 figure. Title and section on Dirac operator changed | null | 10.1088/0264-9381/33/21/215002 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum holonomy theory is a candidate for a non-perturbative theory of
quantum gravity coupled to fermions. The theory is based on the QHD(M) algebra,
which essentially encodes how matter degrees of freedom are moved on a
three-dimensional manifold. In this paper we commence the development of a
lattice-independent formulation. We first introduce a flow-dependent version of
the QHD(M) algebra and formulate necessary conditions for a state to exist
hereon. We then use the GNS construction to build a kinematical Hilbert space.
Finally we find that operators, that correspond to the Dirac and gravitational
Hamiltonians in a semi-classical limit, are background independent.
| [
{
"created": "Sat, 20 Feb 2016 18:40:09 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2016 15:33:52 GMT",
"version": "v2"
}
] | 2016-10-19 | [
[
"Aastrup",
"Johannes",
""
],
[
"Grimstrup",
"Jesper M.",
""
]
] | Quantum holonomy theory is a candidate for a non-perturbative theory of quantum gravity coupled to fermions. The theory is based on the QHD(M) algebra, which essentially encodes how matter degrees of freedom are moved on a three-dimensional manifold. In this paper we commence the development of a lattice-independent formulation. We first introduce a flow-dependent version of the QHD(M) algebra and formulate necessary conditions for a state to exist hereon. We then use the GNS construction to build a kinematical Hilbert space. Finally we find that operators, that correspond to the Dirac and gravitational Hamiltonians in a semi-classical limit, are background independent. |
2404.00159 | Viktoria Kabel | Anne-Catherine de la Hamette, Viktoria Kabel, \v{C}aslav Brukner | What an event is not: unravelling the identity of events in quantum
theory and gravity | 6 pages, 1 figure. Essay written for the Gravity Research Foundation
2024 Awards for Essays on Gravitation | null | null | null | gr-qc physics.hist-ph quant-ph | http://creativecommons.org/licenses/by/4.0/ | We explore the notion of events at the intersection between quantum physics
and gravity, inspired by recent research on superpositions of semiclassical
spacetimes. By going through various experiments and thought experiments --
from a decaying atom, to the double-slit experiment, to the quantum switch --
we analyse which properties can and cannot be used to define events in such
non-classical contexts. Our findings suggest an operational, context-dependent
definition of events which emphasises that their properties can be accessed
without destroying or altering observed phenomena. We discuss the implications
of this understanding of events for indefinite causal order as well as the
non-absoluteness of events in the Wigner's friend thought experiment. These
findings provide a first step for developing a notion of event in quantum
spacetime.
| [
{
"created": "Fri, 29 Mar 2024 21:22:16 GMT",
"version": "v1"
}
] | 2024-04-02 | [
[
"de la Hamette",
"Anne-Catherine",
""
],
[
"Kabel",
"Viktoria",
""
],
[
"Brukner",
"Časlav",
""
]
] | We explore the notion of events at the intersection between quantum physics and gravity, inspired by recent research on superpositions of semiclassical spacetimes. By going through various experiments and thought experiments -- from a decaying atom, to the double-slit experiment, to the quantum switch -- we analyse which properties can and cannot be used to define events in such non-classical contexts. Our findings suggest an operational, context-dependent definition of events which emphasises that their properties can be accessed without destroying or altering observed phenomena. We discuss the implications of this understanding of events for indefinite causal order as well as the non-absoluteness of events in the Wigner's friend thought experiment. These findings provide a first step for developing a notion of event in quantum spacetime. |
1001.1158 | Piero Nicolini | Davide Batic, Piero Nicolini | Fuzziness at the horizon | 4 pages, 1 figure, new version matching that accepted for publication | Phys.Lett.B692:32-35,2010 | 10.1016/j.physletb.2010.07.007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability of the noncommutative Schwarzschild black hole
interior by analysing the propagation of a massless scalar field between the
two horizons. We show that the spacetime fuzziness triggered by the field
higher momenta can cure the classical exponential blue shift divergence,
suppressing the emergence of infinite energy density in a region nearby the
Cauchy horizon.
| [
{
"created": "Thu, 7 Jan 2010 21:09:35 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Aug 2010 13:49:41 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Batic",
"Davide",
""
],
[
"Nicolini",
"Piero",
""
]
] | We study the stability of the noncommutative Schwarzschild black hole interior by analysing the propagation of a massless scalar field between the two horizons. We show that the spacetime fuzziness triggered by the field higher momenta can cure the classical exponential blue shift divergence, suppressing the emergence of infinite energy density in a region nearby the Cauchy horizon. |
2001.03478 | Adrien Druart | Geoffrey Comp\`ere and Adrien Druart | Near-horizon geodesics of high-spin black holes | Accepted for publication in PRD, 4 ancillary files, 62 pages, 31
figures | Phys. Rev. D 101, 084042 (2020) | 10.1103/PhysRevD.101.084042 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide an exhaustive and illustrated classification of timelike and null
geodesics in the near-horizon region of near-extremal Kerr black holes. The
classification of polar motion extends to Kerr black holes of arbitrary spin.
The classification of radial motion leads to a simple parametrization of the
separatrix between bound and unbound motion. Furthermore, we prove that each
timelike or null geodesic is related via conformal transformations and discrete
symmetries to spherical orbits and we provide the explicit mappings. We detail
the high-spin behavior of both the innermost stable and the innermost bound
spherical orbits.
| [
{
"created": "Fri, 10 Jan 2020 14:39:33 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Apr 2020 08:04:44 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Jun 2020 09:02:09 GMT",
"version": "v3"
}
] | 2020-06-24 | [
[
"Compère",
"Geoffrey",
""
],
[
"Druart",
"Adrien",
""
]
] | We provide an exhaustive and illustrated classification of timelike and null geodesics in the near-horizon region of near-extremal Kerr black holes. The classification of polar motion extends to Kerr black holes of arbitrary spin. The classification of radial motion leads to a simple parametrization of the separatrix between bound and unbound motion. Furthermore, we prove that each timelike or null geodesic is related via conformal transformations and discrete symmetries to spherical orbits and we provide the explicit mappings. We detail the high-spin behavior of both the innermost stable and the innermost bound spherical orbits. |
2008.04506 | Yunho Kim | Yunho Kim and Archil Kobakhidze | Topologically induced black hole charge and its astrophysical
manifestations | 6 pages, 2 figures | null | null | null | gr-qc astro-ph.GA astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum corrected effective action for gravity contains massive spin-2 ghost
degrees of freedom and admits a topological term which couples longitudinal
vector degrees of freedom of the massive spin-2 to Maxwell's electromagnetism.
We argue that in the presence of otherwise unobservable gravimagnetic poles
this topological term induces an electric charge on a black hole which can be
probed through the associated electric and magnetic fields. In particular, we
discuss the electromagnetic follow up from the LIGO-sensitive charged black
hole binary coalescence due to the synchrotron radiation from the surrounding
plasma and the shadow of super-massive charged black holes.
| [
{
"created": "Tue, 11 Aug 2020 04:06:06 GMT",
"version": "v1"
}
] | 2020-08-12 | [
[
"Kim",
"Yunho",
""
],
[
"Kobakhidze",
"Archil",
""
]
] | Quantum corrected effective action for gravity contains massive spin-2 ghost degrees of freedom and admits a topological term which couples longitudinal vector degrees of freedom of the massive spin-2 to Maxwell's electromagnetism. We argue that in the presence of otherwise unobservable gravimagnetic poles this topological term induces an electric charge on a black hole which can be probed through the associated electric and magnetic fields. In particular, we discuss the electromagnetic follow up from the LIGO-sensitive charged black hole binary coalescence due to the synchrotron radiation from the surrounding plasma and the shadow of super-massive charged black holes. |
gr-qc/9808076 | Benjamin J. Owen | Benjamin J. Owen (1) and B. S. Sathyaprakash (1 and 2) ((1) Caltech,
(2) Cardiff) | Matched filtering of gravitational waves from inspiraling compact
binaries: Computational cost and template placement | 15 pages, 4 figures, submitted to Phys. Rev. D | Phys.Rev.D60:022002,1999 | 10.1103/PhysRevD.60.022002 | GRP-505 | gr-qc | null | We estimate the number of templates, computational power, and storage
required for a one-step matched filtering search for gravitational waves from
inspiraling compact binaries. These estimates should serve as benchmarks for
the evaluation of more sophisticated strategies such as hierarchical searches.
We use waveform templates based on the second post-Newtonian approximation for
binaries composed of nonspinning compact bodies in circular orbits. We present
estimates for six noise curves: LIGO (three configurations), VIRGO, GEO600, and
TAMA. To search for binaries with components more massive than 0.2M_o while
losing no more than 10% of events due to coarseness of template spacing,
initial LIGO will require about 1*10^11 flops (floating point operations per
second) for data analysis to keep up with data acquisition. This is several
times higher than estimated in previous work by Owen, in part because of the
improved family of templates and in part because we use more realistic (higher)
sampling rates. Enhanced LIGO, GEO600, and TAMA will require computational
power similar to initial LIGO. Advanced LIGO will require 8*10^11 flops, and
VIRGO will require 5*10^12 flops. If the templates are stored rather than
generated as needed, storage requirements range from 1.5*10^11 real numbers for
TAMA to 6*10^14 for VIRGO. We also sketch and discuss an algorithm for placing
the templates in the parameter space.
| [
{
"created": "Thu, 27 Aug 1998 20:53:36 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Owen",
"Benjamin J.",
"",
"1 and 2"
],
[
"Sathyaprakash",
"B. S.",
"",
"1 and 2"
]
] | We estimate the number of templates, computational power, and storage required for a one-step matched filtering search for gravitational waves from inspiraling compact binaries. These estimates should serve as benchmarks for the evaluation of more sophisticated strategies such as hierarchical searches. We use waveform templates based on the second post-Newtonian approximation for binaries composed of nonspinning compact bodies in circular orbits. We present estimates for six noise curves: LIGO (three configurations), VIRGO, GEO600, and TAMA. To search for binaries with components more massive than 0.2M_o while losing no more than 10% of events due to coarseness of template spacing, initial LIGO will require about 1*10^11 flops (floating point operations per second) for data analysis to keep up with data acquisition. This is several times higher than estimated in previous work by Owen, in part because of the improved family of templates and in part because we use more realistic (higher) sampling rates. Enhanced LIGO, GEO600, and TAMA will require computational power similar to initial LIGO. Advanced LIGO will require 8*10^11 flops, and VIRGO will require 5*10^12 flops. If the templates are stored rather than generated as needed, storage requirements range from 1.5*10^11 real numbers for TAMA to 6*10^14 for VIRGO. We also sketch and discuss an algorithm for placing the templates in the parameter space. |
1110.2905 | Francesca Vidotto | Francesca Vidotto | General covariant transition amplitudes in quantum cosmology | 4-page review for Scientifica Acta | Scientifica Acta 5, No. 1, Ph 17-21 (2011) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The path-integral approach to cosmology consists in the computation of
transition amplitudes between states of the quantum geometry of the universe.
In the past, the concrete computation of these transitions amplitudes has been
performed in a perturbative regime, breaking the full general covariance of the
theory. Here I present how it is possible to define a general covariant path
integral in quantum cosmology, by relying on the most recent results of the
canonical and covariant formulations of Loop Quantum Gravity. I present two
strategies that have been implemented. The first starts from the full Spinfoam
theory, i.e. the path-integral framework for Loop Quantum Gravity, and defines
a cosmological system. This is not obtained from symmetry reduced variables
that are successively quantized, but directly considering the approximations
that are characteristic of the full theory. The Spinfoam Cosmology obtained in
this way includes quantum fluctuations beyond standard perturbation theory. The
second strategy exploits the Hamiltonian constraint of Loop Quantum Cosmology,
that is exponentiated in the formal expression of the usual path integral. The
result is a general covariant path integral, that reproduces the form of the
amplitude in the full Spinfoam theory. Therefore, this procedure connects the
canonical and the covariant formalisms.
| [
{
"created": "Thu, 13 Oct 2011 12:07:18 GMT",
"version": "v1"
}
] | 2012-05-22 | [
[
"Vidotto",
"Francesca",
""
]
] | The path-integral approach to cosmology consists in the computation of transition amplitudes between states of the quantum geometry of the universe. In the past, the concrete computation of these transitions amplitudes has been performed in a perturbative regime, breaking the full general covariance of the theory. Here I present how it is possible to define a general covariant path integral in quantum cosmology, by relying on the most recent results of the canonical and covariant formulations of Loop Quantum Gravity. I present two strategies that have been implemented. The first starts from the full Spinfoam theory, i.e. the path-integral framework for Loop Quantum Gravity, and defines a cosmological system. This is not obtained from symmetry reduced variables that are successively quantized, but directly considering the approximations that are characteristic of the full theory. The Spinfoam Cosmology obtained in this way includes quantum fluctuations beyond standard perturbation theory. The second strategy exploits the Hamiltonian constraint of Loop Quantum Cosmology, that is exponentiated in the formal expression of the usual path integral. The result is a general covariant path integral, that reproduces the form of the amplitude in the full Spinfoam theory. Therefore, this procedure connects the canonical and the covariant formalisms. |
gr-qc/9809072 | Roger Ellman | Roger Ellman (The-Origin Foundation, Inc) | Gravitational and Anti-gravitational Applications | 20 pages. See http://www.the-origin.org for related info | null | null | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is now possible to partially deflect gravitation away from an object so
that the gravitational attraction on the object is reduced. That effect makes
it possible to extract energy from the gravitational field, which makes the
generation of gravito-electric power technologically feasible. Such plants
would be similar to hydro-electric plants and would have their advantages of
not needing fuel and not polluting the environment.
Physically, the action of deflecting away gravitational attraction, which of
course is directed toward the gravitation source, produces an equal but
opposite reaction on the mechanism that produces the deflection of the
gravitational action [the deflector], a reaction directed away from the
gravitation source.
The result is the combination of reducing the gravitational attractive
acceleration of the object toward the gravitation source plus the introducing
of a reactive acceleration on the object in the direction away from the
gravitation source.
Such a deflector, engineered to enable controlled adjustment of the amount
and the direction of its action, could provide for a spacecraft both launch
levitation and deep space travel acceleration. It could provide both levitation
and horizontal motion for a flying vehicle over a planet surface.
This technology, which uses readily abundantly available materials and
techniques, is ready now for research and engineering refinement.
| [
{
"created": "Sat, 26 Sep 1998 16:25:55 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Oct 1998 03:09:18 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Nov 1998 20:07:42 GMT",
"version": "v3"
},
{
"created": "Tue, 29 Jun 1999 22:18:32 GMT",
"version": "v4"
},
{
"created": "Sun, 9 Jun 2013 18:29:15 GMT",
"version": "v5"
}
] | 2013-06-11 | [
[
"Ellman",
"Roger",
"",
"The-Origin Foundation, Inc"
]
] | It is now possible to partially deflect gravitation away from an object so that the gravitational attraction on the object is reduced. That effect makes it possible to extract energy from the gravitational field, which makes the generation of gravito-electric power technologically feasible. Such plants would be similar to hydro-electric plants and would have their advantages of not needing fuel and not polluting the environment. Physically, the action of deflecting away gravitational attraction, which of course is directed toward the gravitation source, produces an equal but opposite reaction on the mechanism that produces the deflection of the gravitational action [the deflector], a reaction directed away from the gravitation source. The result is the combination of reducing the gravitational attractive acceleration of the object toward the gravitation source plus the introducing of a reactive acceleration on the object in the direction away from the gravitation source. Such a deflector, engineered to enable controlled adjustment of the amount and the direction of its action, could provide for a spacecraft both launch levitation and deep space travel acceleration. It could provide both levitation and horizontal motion for a flying vehicle over a planet surface. This technology, which uses readily abundantly available materials and techniques, is ready now for research and engineering refinement. |
gr-qc/0502008 | Spiros Cotsakis | Spiros Cotsakis | Slice Energy and Theories of Gravitation | 16 pages, In: Proceedings of the 11th Greek Relativity Meeting | J.Phys.Conf.Ser. 8 (2005) 39-48 | 10.1088/1742-6596/8/1/006 | null | gr-qc | null | We review recent work on the use of the slice energy concept in generalized
theories of gravitation. We focus on two special features in these theories,
namely, the energy exchange between the matter component and the scalar field
generated by the conformal transformation to the Einstein frame of such
theories and the issue of the physical equivalence of different conformal frame
representations. We show that all such conformally-related, generalized
theories of gravitation allow for the slice energy to be invariably defined and
its fundamental properties be insensitive to conformal transformations.
| [
{
"created": "Wed, 2 Feb 2005 11:16:24 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Cotsakis",
"Spiros",
""
]
] | We review recent work on the use of the slice energy concept in generalized theories of gravitation. We focus on two special features in these theories, namely, the energy exchange between the matter component and the scalar field generated by the conformal transformation to the Einstein frame of such theories and the issue of the physical equivalence of different conformal frame representations. We show that all such conformally-related, generalized theories of gravitation allow for the slice energy to be invariably defined and its fundamental properties be insensitive to conformal transformations. |
2204.02755 | P. A. Gonzalez | Sharmanthie Fernando, P. A. Gonz\'alez, Yerko V\'asquez | Extreme Dilaton Black Holes in 2 +1 Dimensions: Quasinormal modes | 19 pages, 1 figure | null | 10.1140/epjc/s10052-022-10554-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study neutral massless scalar field perturbations around an extreme
dilaton black hole in 2 +1 dimensions: the wave equations of the massless
scalar field is shown to be exactly solvable in terms of Whittaker functions.
Thus, the quasinormal modes are computed exactly and shown to be purely
imaginary: we show the existence of stable and unstable modes. Interestingly,
the quasinormal modes do not depend on the black holes parameters and the
fundamental mode is always unstable and depends only on the parameters of the
test field. Also, we determine the quasinormal frequencies via the improved
asymptotic iteration method which shows a good agreement with the analytical
results.
| [
{
"created": "Wed, 6 Apr 2022 12:01:58 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Fernando",
"Sharmanthie",
""
],
[
"González",
"P. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We study neutral massless scalar field perturbations around an extreme dilaton black hole in 2 +1 dimensions: the wave equations of the massless scalar field is shown to be exactly solvable in terms of Whittaker functions. Thus, the quasinormal modes are computed exactly and shown to be purely imaginary: we show the existence of stable and unstable modes. Interestingly, the quasinormal modes do not depend on the black holes parameters and the fundamental mode is always unstable and depends only on the parameters of the test field. Also, we determine the quasinormal frequencies via the improved asymptotic iteration method which shows a good agreement with the analytical results. |
2011.14623 | Xiao-Min Zhang | Xiao-Min Zhang, Ang Fu, Kai Li, Qian Li, Peng-Cheng Chu, Hong-Yang Ma
and Jian-Yang Zhu | Consistency of a kind of general noncanonical warm inflation | 6 pages, 0figures | Phys. Rev. D 103, 023511 (2021) | 10.1103/PhysRevD.103.023511 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The framework of a kind of noncanonical warm inflation is introduced, and the
dynamical equations of this scenario are presented. We propose the slow roll
approximations and give some redefining slow roll parameters in this scenario
which remain dimensionless. Performing systemic stability analysis, we
calculate the slow roll conditions to guarantee that slow roll approximations
hold. The slow roll conditions suggest slow roll inflation in general
noncanonical warm inflationary scenario can still exist, and in addition, the
slow roll approximations are more easily to be satisfied. Then, a concrete
Dirac-Born-Infeld warm inflationary model is studied.
| [
{
"created": "Mon, 30 Nov 2020 08:52:40 GMT",
"version": "v1"
}
] | 2021-01-13 | [
[
"Zhang",
"Xiao-Min",
""
],
[
"Fu",
"Ang",
""
],
[
"Li",
"Kai",
""
],
[
"Li",
"Qian",
""
],
[
"Chu",
"Peng-Cheng",
""
],
[
"Ma",
"Hong-Yang",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | The framework of a kind of noncanonical warm inflation is introduced, and the dynamical equations of this scenario are presented. We propose the slow roll approximations and give some redefining slow roll parameters in this scenario which remain dimensionless. Performing systemic stability analysis, we calculate the slow roll conditions to guarantee that slow roll approximations hold. The slow roll conditions suggest slow roll inflation in general noncanonical warm inflationary scenario can still exist, and in addition, the slow roll approximations are more easily to be satisfied. Then, a concrete Dirac-Born-Infeld warm inflationary model is studied. |
gr-qc/0511165 | Valerii Dryuma sem | V.Dryuma | On the Riemann Extension of the G\"odel Space-Time metric | 17 pages | null | null | null | gr-qc | null | Some properties of the G\"odel space-time metric and its Riemann extension
are studied
| [
{
"created": "Wed, 30 Nov 2005 13:04:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dryuma",
"V.",
""
]
] | Some properties of the G\"odel space-time metric and its Riemann extension are studied |
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