id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1909.00236 | Hosein Ramezani Aval | H. Ramezani-Aval | The fermionic Unruh effect in relativistic eccentric uniformly rotating
frames | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate detection of Dirac quanta in a uniformly eccentric rotating
frame both with canonical and detector approaches by employing relativistic
rotational transformations. First we consider a relativistic uniformly
eccentric rotating detector that is coupled to the scalar density of a massless
Dirac field, and show that this detector has a nonzero response function and
observes a Planckian energy spectrum. Then using relativistic rotational
transformations, we investigate the canonical quantization of Dirac field in
relativistic eccentric rotating frame. We show that it's not possible to obtain
the analytic solution for Dirac equation in this frame and so canonical
approach can not be carried out.
| [
{
"created": "Sat, 31 Aug 2019 16:14:05 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Ramezani-Aval",
"H.",
""
]
] | We investigate detection of Dirac quanta in a uniformly eccentric rotating frame both with canonical and detector approaches by employing relativistic rotational transformations. First we consider a relativistic uniformly eccentric rotating detector that is coupled to the scalar density of a massless Dirac field, and show that this detector has a nonzero response function and observes a Planckian energy spectrum. Then using relativistic rotational transformations, we investigate the canonical quantization of Dirac field in relativistic eccentric rotating frame. We show that it's not possible to obtain the analytic solution for Dirac equation in this frame and so canonical approach can not be carried out. |
1007.3732 | Simone Mercuri | Simone Mercuri | Modifications in the Spectrum of Primordial Gravitational Waves Induced
by Instantonic Fluctuations | V1: 8 pages. V2: 8 pages, some points clarified, typos corrected,
some references added, final result unchanged. V3: 8 pages, title changed,
presentation improved, discussion of phenomenological consequences added,
comments very welcome. V4: Discussion further improved, comments very very
welcome | Phys.Rev.D84:044035,2011 | 10.1103/PhysRevD.84.044035 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Vacuum to vacuum instantonic transitions modify the power spectrum of
primordial gravitational waves. We evaluate the new form of the power spectrum
for ordinary gravity as well as the parity violation induced in the spectrum by
a modification of General Relativity known as Holst term and we outline the
possible experimental consequences.
| [
{
"created": "Wed, 21 Jul 2010 19:51:23 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jul 2010 00:36:13 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Mar 2011 18:01:30 GMT",
"version": "v3"
},
{
"created": "Mon, 25 Jul 2011 16:29:54 GMT",
"version": "v4"
}
] | 2011-09-08 | [
[
"Mercuri",
"Simone",
""
]
] | Vacuum to vacuum instantonic transitions modify the power spectrum of primordial gravitational waves. We evaluate the new form of the power spectrum for ordinary gravity as well as the parity violation induced in the spectrum by a modification of General Relativity known as Holst term and we outline the possible experimental consequences. |
1402.5104 | Ahmed Farag Ali | Ahmed Farag Ali and Barun Majumder | Towards a Cosmology with Minimal Length and Maximal Energy | 14 pages, 3 figures, To appear in Class.Quant.Grav | Class.Quant.Grav. 31 (2014) 215007 | 10.1088/0264-9381/31/21/215007 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Friedmann-Robertson-Walker (FRW) universe and Bianchi I,II universes are
investigated in the framework of the generalized uncertainty principle (GUP)
with a linear and a quadratic term in Planck length and momentum, which
predicts minimum measurable length as well as maximum measurable momentum. We
get a dynamic cosmological bounce for the FRW universe. With Bianchi universe,
we found that the universe may be still isotropic by implementing GUP.
Moreover, the wall velocity appears to be stationary with respect to the
universe velocity which means that when the momentum of the Universe evolves
into a maximum measurable energy, the bounce is enhanced against the wall which
means no maximum limit angle is manifested anymore.
| [
{
"created": "Thu, 20 Feb 2014 19:06:30 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Feb 2014 15:31:13 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Aug 2014 09:50:57 GMT",
"version": "v3"
}
] | 2014-10-21 | [
[
"Ali",
"Ahmed Farag",
""
],
[
"Majumder",
"Barun",
""
]
] | The Friedmann-Robertson-Walker (FRW) universe and Bianchi I,II universes are investigated in the framework of the generalized uncertainty principle (GUP) with a linear and a quadratic term in Planck length and momentum, which predicts minimum measurable length as well as maximum measurable momentum. We get a dynamic cosmological bounce for the FRW universe. With Bianchi universe, we found that the universe may be still isotropic by implementing GUP. Moreover, the wall velocity appears to be stationary with respect to the universe velocity which means that when the momentum of the Universe evolves into a maximum measurable energy, the bounce is enhanced against the wall which means no maximum limit angle is manifested anymore. |
2112.10590 | Xun Xue | Junhui Lai and Xun Xue | The Scattering of Dirac and Majorana Fermions in Spherically Symmetric
Gravitational Field and Torsion Field | 11 pages, no figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The possibility to distinguish Dirac from Majorana fermion by gravitational
interaction and torsion coupling is discussed. The scattering of both Dirac and
Majorana particles are the same in the spherically symmetric gravitational
field up to the first order perturbation of the fermion-gravity interaction.
The scattering behaviors of Dirac and Majorana fermion are also the same by
axial vector torsion but different by vector torsion. We get the conclusion
that the scattering by vector torsion field can distinguish the Dirac from
Majorana neutrino.
| [
{
"created": "Mon, 20 Dec 2021 15:09:14 GMT",
"version": "v1"
}
] | 2021-12-21 | [
[
"Lai",
"Junhui",
""
],
[
"Xue",
"Xun",
""
]
] | The possibility to distinguish Dirac from Majorana fermion by gravitational interaction and torsion coupling is discussed. The scattering of both Dirac and Majorana particles are the same in the spherically symmetric gravitational field up to the first order perturbation of the fermion-gravity interaction. The scattering behaviors of Dirac and Majorana fermion are also the same by axial vector torsion but different by vector torsion. We get the conclusion that the scattering by vector torsion field can distinguish the Dirac from Majorana neutrino. |
gr-qc/0207055 | Horacio Casini | H. Casini | A geometrical origin for the covariant entropy bound | 20 pages, 8 figures, final version | Class.Quant.Grav. 20 (2003) 2509-2526 | 10.1088/0264-9381/20/13/304 | CPT-2002/P.4395 | gr-qc hep-th | null | Causal diamond-shaped subsets of space-time are naturally associated with
operator algebras in quantum field theory, and they are also related to the
Bousso covariant entropy bound. In this work we argue that the net of these
causal sets to which are assigned the local operator algebras of quantum
theories should be taken to be non orthomodular if there is some lowest scale
for the description of space-time as a manifold. This geometry can be related
to a reduction in the degrees of freedom of the holographic type under certain
natural conditions for the local algebras. A non orthomodular net of causal
sets that implements the cutoff in a covariant manner is constructed. It gives
an explanation, in a simple example, of the non positive expansion condition
for light-sheet selection in the covariant entropy bound. It also suggests a
different covariant formulation of entropy bound.
| [
{
"created": "Mon, 15 Jul 2002 08:42:07 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Aug 2002 09:28:02 GMT",
"version": "v2"
},
{
"created": "Fri, 9 May 2003 12:22:05 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Casini",
"H.",
""
]
] | Causal diamond-shaped subsets of space-time are naturally associated with operator algebras in quantum field theory, and they are also related to the Bousso covariant entropy bound. In this work we argue that the net of these causal sets to which are assigned the local operator algebras of quantum theories should be taken to be non orthomodular if there is some lowest scale for the description of space-time as a manifold. This geometry can be related to a reduction in the degrees of freedom of the holographic type under certain natural conditions for the local algebras. A non orthomodular net of causal sets that implements the cutoff in a covariant manner is constructed. It gives an explanation, in a simple example, of the non positive expansion condition for light-sheet selection in the covariant entropy bound. It also suggests a different covariant formulation of entropy bound. |
1103.3415 | Etera R. Livine | Valentin Bonzom, Etera R. Livine | A New Recursion Relation for the 6j-Symbol | 10 pages, v2: title and introduction changed, paper re-structured;
Annales Henri Poincare (2011) | null | 10.1007/s00023-011-0143-y | pi-qg-218 | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 6j-symbol is a fundamental object from the re-coupling theory of SU(2)
representations. In the limit of large angular momenta, its asymptotics is
known to be described by the geometry of a tetrahedron with quantized lengths.
This article presents a new recursion formula for the square of the 6j-symbol.
In the asymptotic regime, the new recursion is shown to characterize the
closure of the relevant tetrahedron. Since the 6j-symbol is the basic building
block of the Ponzano-Regge model for pure three-dimensional quantum gravity, we
also discuss how to generalize the method to derive more general recursion
relations on the full amplitudes.
| [
{
"created": "Thu, 17 Mar 2011 13:56:30 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Nov 2011 19:33:47 GMT",
"version": "v2"
}
] | 2011-11-16 | [
[
"Bonzom",
"Valentin",
""
],
[
"Livine",
"Etera R.",
""
]
] | The 6j-symbol is a fundamental object from the re-coupling theory of SU(2) representations. In the limit of large angular momenta, its asymptotics is known to be described by the geometry of a tetrahedron with quantized lengths. This article presents a new recursion formula for the square of the 6j-symbol. In the asymptotic regime, the new recursion is shown to characterize the closure of the relevant tetrahedron. Since the 6j-symbol is the basic building block of the Ponzano-Regge model for pure three-dimensional quantum gravity, we also discuss how to generalize the method to derive more general recursion relations on the full amplitudes. |
2305.15185 | Andrew L. Miller | Andrew L. Miller | Recent results from continuous gravitational wave searches using data
from LIGO/Virgo/KAGRA's third observing run | Contribution to the 2023 Gravitation session of the 57th Rencontres
de Moriond | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The third observing run of advanced LIGO, Virgo and KAGRA brought
unprecedented sensitivity towards a variety of quasi-monochromatic, persistent
gravitational-wave signals. Continuous waves allow us to probe not just the
existence of canonical asymmetrically rotating neutron stars, but also
different forms of dark matter, thus showing the wide-ranging astrophysical
implications of using a relatively simple signal model. I will describe the
major results from the numerous continuous-wave searches that were performed in
O3, both inside and outside the LIGO/Virgo/KAGRA collaborations, and show how
impactful to multi-messenger physics that they have been.
| [
{
"created": "Wed, 24 May 2023 14:25:43 GMT",
"version": "v1"
}
] | 2023-05-25 | [
[
"Miller",
"Andrew L.",
""
]
] | The third observing run of advanced LIGO, Virgo and KAGRA brought unprecedented sensitivity towards a variety of quasi-monochromatic, persistent gravitational-wave signals. Continuous waves allow us to probe not just the existence of canonical asymmetrically rotating neutron stars, but also different forms of dark matter, thus showing the wide-ranging astrophysical implications of using a relatively simple signal model. I will describe the major results from the numerous continuous-wave searches that were performed in O3, both inside and outside the LIGO/Virgo/KAGRA collaborations, and show how impactful to multi-messenger physics that they have been. |
gr-qc/0608088 | Asuncion Fuente | A. Fuente, T. Alonso-Albi, R. Bachiller, A. Natta, L. Testi, R. Neri,
P. Planesas | A Keplerian gaseous disk around the B0 star R Mon | 5 pages | Astrophys.J.649:L119-L122,2006 | 10.1086/508349 | null | gr-qc astro-ph | null | We present high-angular resolution observations of the circumstellar disk
around the massive Herbig Be star R Mon (M~8 Msun) in the continuum at 2.7mm
and 1.3mm and the CO 1->0 and 2->1 rotational lines. Based on the new 1.3mm
continuum image we estimate a disk mass (gas+dust) of 0.007 Msun and an outer
radius of <150 AU. Our CO images are consistent with the existence of a
Keplerian rotating gaseous disk around this star. Up to our knowledge, this is
the most clear evidence for the existence of Keplerian disks around massive
stars reported thus far. The mass and physical characteristics of this disk are
similar to thoseof the more evolved T Tauri stars and indicate a shorter
timescale for the evolution and dispersal of circumstellar disks around massive
stars which lose most of their mass before the star becomes visible.
| [
{
"created": "Fri, 18 Aug 2006 14:11:44 GMT",
"version": "v1"
}
] | 2011-02-11 | [
[
"Fuente",
"A.",
""
],
[
"Alonso-Albi",
"T.",
""
],
[
"Bachiller",
"R.",
""
],
[
"Natta",
"A.",
""
],
[
"Testi",
"L.",
""
],
[
"Neri",
"R.",
""
],
[
"Planesas",
"P.",
""
]
] | We present high-angular resolution observations of the circumstellar disk around the massive Herbig Be star R Mon (M~8 Msun) in the continuum at 2.7mm and 1.3mm and the CO 1->0 and 2->1 rotational lines. Based on the new 1.3mm continuum image we estimate a disk mass (gas+dust) of 0.007 Msun and an outer radius of <150 AU. Our CO images are consistent with the existence of a Keplerian rotating gaseous disk around this star. Up to our knowledge, this is the most clear evidence for the existence of Keplerian disks around massive stars reported thus far. The mass and physical characteristics of this disk are similar to thoseof the more evolved T Tauri stars and indicate a shorter timescale for the evolution and dispersal of circumstellar disks around massive stars which lose most of their mass before the star becomes visible. |
1512.04676 | Peng Xu | Peng Xu and Ho Jung Paik | First-order post-Newtonian analysis of the relativistic tidal effects
for satellite gradiometry and the Mashhoon-Theiss anomaly | Typos in Eq. (11) and Eq. (22b) are corrected. 10 pages, 3 figures | Phys. Rev. D 93, 044057 (2016) | 10.1103/PhysRevD.93.044057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With continuous advances in technology, future satellite gradiometry missions
will be capable of performing precision relativistic experiments and imposing
constraints on modern gravity theories. To this end, the full first-order
post-Newtonian tidal tensor under inertially guided and Earth-pointing local
frames along post-Newtonian orbits is worked out. The physical picture behind
the "Mashhoon-Theiss anomaly" is explained at the post-Newtonian level. The
relativistic precession of the local frame with respect to the sidereal frame
will produce modulations of Newtonian tidal forces along certain bases, which
gives rise to two different kinds of secular tidal tensors. The measurements of
the secular tidal force from the frame-dragging effect is also discussed.
| [
{
"created": "Tue, 15 Dec 2015 08:33:59 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Feb 2016 07:22:26 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Sep 2016 08:38:06 GMT",
"version": "v3"
}
] | 2016-09-29 | [
[
"Xu",
"Peng",
""
],
[
"Paik",
"Ho Jung",
""
]
] | With continuous advances in technology, future satellite gradiometry missions will be capable of performing precision relativistic experiments and imposing constraints on modern gravity theories. To this end, the full first-order post-Newtonian tidal tensor under inertially guided and Earth-pointing local frames along post-Newtonian orbits is worked out. The physical picture behind the "Mashhoon-Theiss anomaly" is explained at the post-Newtonian level. The relativistic precession of the local frame with respect to the sidereal frame will produce modulations of Newtonian tidal forces along certain bases, which gives rise to two different kinds of secular tidal tensors. The measurements of the secular tidal force from the frame-dragging effect is also discussed. |
gr-qc/0702077 | Michel Leclerc | M. Leclerc | Hamiltonian reduction of spin-two theory and of solvable cosmologies | minor changes, refs. added | Class.Quant.Grav.24:4337-4360,2007 | 10.1088/0264-9381/24/17/005 | null | gr-qc | null | The Hamiltonian reduction of the massless spin-two field theory is carried
out following the Faddeev-Jackiw approach. The reduced Hamiltonian contains
only the traceless-transverse fields, but not all of the non-propagating
components can be determined by the constraints of the theory. The reason for
this is found in the fact that the Hamiltonian is not gauge invariant.
Consequences and implications for General Relativity are discussed and
illustrated on the example of Robertson-Walker cosmologies with a scalar field.
Also, it it shown that for those explicitely solvable models, the reduced form
of the dynamics uniquely determines the operator ordering that has to be
adopted in the Wheeler-DeWitt equation in order to maintain consistency.
| [
{
"created": "Wed, 14 Feb 2007 09:43:47 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2007 13:57:23 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Leclerc",
"M.",
""
]
] | The Hamiltonian reduction of the massless spin-two field theory is carried out following the Faddeev-Jackiw approach. The reduced Hamiltonian contains only the traceless-transverse fields, but not all of the non-propagating components can be determined by the constraints of the theory. The reason for this is found in the fact that the Hamiltonian is not gauge invariant. Consequences and implications for General Relativity are discussed and illustrated on the example of Robertson-Walker cosmologies with a scalar field. Also, it it shown that for those explicitely solvable models, the reduced form of the dynamics uniquely determines the operator ordering that has to be adopted in the Wheeler-DeWitt equation in order to maintain consistency. |
gr-qc/0509077 | Daniel Grumiller | Daniel Grumiller | The Volume of 2D Black Holes | 9 pages, 3 figures, uses iopart_mod.cls | J.Phys.Conf.Ser. 33 (2006) 361-366 | 10.1088/1742-6596/33/1/044 | null | gr-qc | null | It is shown that the definition for the volume of stationary black holes
advocated in hep-th/0508108 readily generalizes to the case of dilaton gravity
in D=2. The dilaton field is included as part of the measure. A feature
observed in D=3 and 4 has been the impossibility to obtain infinite volume
while retaining finite area without encountering some kind of pathology. It is
demonstrated that this also holds in D=2. Consistency with spherically reduced
gravity is shown. For the Witten black hole it is found that the area is
proportional to the volume.
| [
{
"created": "Tue, 20 Sep 2005 11:43:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Grumiller",
"Daniel",
""
]
] | It is shown that the definition for the volume of stationary black holes advocated in hep-th/0508108 readily generalizes to the case of dilaton gravity in D=2. The dilaton field is included as part of the measure. A feature observed in D=3 and 4 has been the impossibility to obtain infinite volume while retaining finite area without encountering some kind of pathology. It is demonstrated that this also holds in D=2. Consistency with spherically reduced gravity is shown. For the Witten black hole it is found that the area is proportional to the volume. |
1906.08920 | Jianbo Lu | Jianbo Lu, Xin Zhao, Guoying Chee | Cosmology in symmetric teleparallel gravity and its dynamical system | 13 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1806.10437, arXiv:1301.0865 by other authors | Eur. Phys. J. C (2019) 79:530 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore an extension of the symmetric teleparallel gravity denoted the
$f(Q)$ theory, by considering a function of the nonmetricity invariant $Q$ as
the gravitational Lagrangian. Some interesting properties could be found in the
$f(Q)$ theory by comparing with the $f(R)$ and $f(T)$ theories. The field
equations are derived in the $f(Q)$ theory. The cosmological application is
investigated. In this theory the accelerating expansion is an intrinsic
property of the universe geometry without need of either exotic dark energy or
extra fields. And the state equation of the geometrical dark energy can cross
over the phantom divide line in the $f(Q)$ theory. In addition, the dynamical
system method are investigated. It is shown that there are five critical points
in the STG model for taking $f(Q)=Q+\alpha Q^2$. The critical points $P_{4}$
and $P_{5}$ are stable. $P_{4}$ corresponds to the geometrical dark energy
dominated de Sitter universe ($w_{tot}^{eff}$=-1), while $P_{5}$ corresponds to
the matter dominated universe ($w_{tot}^{eff}$=0). Given that $P_{4}$
represents an attractor, the cosmological constant problems, such as the fine
tuning problem, could be solved in the STG model.
| [
{
"created": "Fri, 21 Jun 2019 02:21:47 GMT",
"version": "v1"
}
] | 2019-06-24 | [
[
"Lu",
"Jianbo",
""
],
[
"Zhao",
"Xin",
""
],
[
"Chee",
"Guoying",
""
]
] | We explore an extension of the symmetric teleparallel gravity denoted the $f(Q)$ theory, by considering a function of the nonmetricity invariant $Q$ as the gravitational Lagrangian. Some interesting properties could be found in the $f(Q)$ theory by comparing with the $f(R)$ and $f(T)$ theories. The field equations are derived in the $f(Q)$ theory. The cosmological application is investigated. In this theory the accelerating expansion is an intrinsic property of the universe geometry without need of either exotic dark energy or extra fields. And the state equation of the geometrical dark energy can cross over the phantom divide line in the $f(Q)$ theory. In addition, the dynamical system method are investigated. It is shown that there are five critical points in the STG model for taking $f(Q)=Q+\alpha Q^2$. The critical points $P_{4}$ and $P_{5}$ are stable. $P_{4}$ corresponds to the geometrical dark energy dominated de Sitter universe ($w_{tot}^{eff}$=-1), while $P_{5}$ corresponds to the matter dominated universe ($w_{tot}^{eff}$=0). Given that $P_{4}$ represents an attractor, the cosmological constant problems, such as the fine tuning problem, could be solved in the STG model. |
2201.06976 | Priyasri Kar | Priyasri Kar | Classes of exact solutions for the massless Dirac particle in the
$C$-metric | 18 pages | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The massless Dirac particle in the $C$-metric, representing the exterior
gravitational field of a uniformly accelerating black hole, is studied. Classes
of (quasi-)polynomial solutions to the radial and the polar parts of the Dirac
equation, each of which is equivalent to the general Heun equation~(GHE), are
obtained exploiting the underlying $su(1,1)$ algebraic structures of the GHE.
| [
{
"created": "Tue, 18 Jan 2022 13:35:13 GMT",
"version": "v1"
}
] | 2022-01-19 | [
[
"Kar",
"Priyasri",
""
]
] | The massless Dirac particle in the $C$-metric, representing the exterior gravitational field of a uniformly accelerating black hole, is studied. Classes of (quasi-)polynomial solutions to the radial and the polar parts of the Dirac equation, each of which is equivalent to the general Heun equation~(GHE), are obtained exploiting the underlying $su(1,1)$ algebraic structures of the GHE. |
2404.17941 | Naman Kumar | Naman Kumar | Variable Brane Tension and Dark Energy | null | EPL 145 39001 (2024) | 10.1209/0295-5075/ad233f | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we show that in a particular braneworld scenario with
variable brane tension, we obtain matter acting as dark energy while the
gravitational constant $G$ promoted to a scalar field on the brane plays the
role of matter (both in the sense they have an 'effective' Equation of State
equivalent to that of dark energy and matter respectively). This result is
interpreted from the Friedmann equation obtained from our model that exactly
matches the standard Friedmann equation of General Relativity with a
cosmological constant $\Lambda$ in terms of the aforementioned quantities. The
universe is assumed to consist of only matter and dark energy in this model
which is a good approximation for our universe.
| [
{
"created": "Sat, 27 Apr 2024 15:44:36 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Kumar",
"Naman",
""
]
] | In this letter, we show that in a particular braneworld scenario with variable brane tension, we obtain matter acting as dark energy while the gravitational constant $G$ promoted to a scalar field on the brane plays the role of matter (both in the sense they have an 'effective' Equation of State equivalent to that of dark energy and matter respectively). This result is interpreted from the Friedmann equation obtained from our model that exactly matches the standard Friedmann equation of General Relativity with a cosmological constant $\Lambda$ in terms of the aforementioned quantities. The universe is assumed to consist of only matter and dark energy in this model which is a good approximation for our universe. |
1312.4173 | Alexander Stottmeister | Alexander Stottmeister and Thomas Thiemann | The microlocal spectrum condition, initial value formulations and
background independence | some typos corrected, extended discussion | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the implications of the microlocal spectrum/Hadamard condition for
states in a (linear) quantum field theory on a globally hyperbolic spacetime
$M$ in the context of a (distributional) initial value formulation. More
specifically, we work in a $3+1$-split $M\cong\mathbb{R}\times\Sigma$ and give
a bound, independent of the spacetime metric, on the wave front sets of the
initial data for a quasi-free Hadamard state in the quantum field theory
defined by a normally hyperbolic differential operator $P$ acting in a vector
bundle $E\stackrel{\pi}{\rightarrow}M$. This aims at a possible way to apply
the concept of Hadamard states within approaches to quantum field
theory/gravity relying on a Hamiltonian formulation, potentially without a
(classical) background metric $g$.
| [
{
"created": "Sun, 15 Dec 2013 17:44:56 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Apr 2015 01:17:50 GMT",
"version": "v2"
}
] | 2015-04-10 | [
[
"Stottmeister",
"Alexander",
""
],
[
"Thiemann",
"Thomas",
""
]
] | We analyze the implications of the microlocal spectrum/Hadamard condition for states in a (linear) quantum field theory on a globally hyperbolic spacetime $M$ in the context of a (distributional) initial value formulation. More specifically, we work in a $3+1$-split $M\cong\mathbb{R}\times\Sigma$ and give a bound, independent of the spacetime metric, on the wave front sets of the initial data for a quasi-free Hadamard state in the quantum field theory defined by a normally hyperbolic differential operator $P$ acting in a vector bundle $E\stackrel{\pi}{\rightarrow}M$. This aims at a possible way to apply the concept of Hadamard states within approaches to quantum field theory/gravity relying on a Hamiltonian formulation, potentially without a (classical) background metric $g$. |
1404.4036 | Edward Wilson-Ewing | Tomasz Pawlowski, Roberto Pierini, Edward Wilson-Ewing | Loop quantum cosmology of a radiation-dominated flat FLRW universe | 29 pages, 6 figures, v2: Clarifications added, notation improved and
presentation streamlined; matches the version accepted for publication in PRD | Phys. Rev. D 90, 123538 (2014) | 10.1103/PhysRevD.90.123538 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the loop quantum cosmology of a flat
Friedmann-Lemaitre-Robertson-Walker space-time with a Maxwell field. We show
that many of the qualitative properties derived for the case of a massless
scalar field also hold for a Maxwell field. In particular, the big-bang
singularity is replaced by a quantum bounce, and the operator corresponding to
the matter energy density is bounded above by the same critical energy density.
We also numerically study the evolution of wave functions that are sharply
peaked in the low energy regime, and derive effective equations which very
closely approximate the full quantum dynamics of sharply peaked states at all
times, including the near-bounce epoch. In the process, the analytical and
numerical methods originally used to study the dynamics in LQC for the case of
a massless scalar field are substantially improved to handle the difficulties
(that generically arise for matter content other than a massless scalar field)
related to the presence of a Maxwell field.
| [
{
"created": "Tue, 15 Apr 2014 19:40:20 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Dec 2014 14:48:26 GMT",
"version": "v2"
}
] | 2015-01-07 | [
[
"Pawlowski",
"Tomasz",
""
],
[
"Pierini",
"Roberto",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | We study the loop quantum cosmology of a flat Friedmann-Lemaitre-Robertson-Walker space-time with a Maxwell field. We show that many of the qualitative properties derived for the case of a massless scalar field also hold for a Maxwell field. In particular, the big-bang singularity is replaced by a quantum bounce, and the operator corresponding to the matter energy density is bounded above by the same critical energy density. We also numerically study the evolution of wave functions that are sharply peaked in the low energy regime, and derive effective equations which very closely approximate the full quantum dynamics of sharply peaked states at all times, including the near-bounce epoch. In the process, the analytical and numerical methods originally used to study the dynamics in LQC for the case of a massless scalar field are substantially improved to handle the difficulties (that generically arise for matter content other than a massless scalar field) related to the presence of a Maxwell field. |
1010.2843 | Jose Luis Hernandez-Pastora | J.L. Hernandez-Pastora and J. Ospino | New Representation of some Static and Axisymmetric Vacuum Solutions | Submitted to General Relativity and Gravitation | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the Einstein vacuum-equations for the case of static and
axisymmetric solutions in a system of coordinates different from the Weyl
standard one. We prove that there exists a class of solutions with the
appropriate asymptotical behaviour which can be written in a simple compact
form, in terms of a function that must satisfies certain Cauchy-Newman problem.
The relation between the choice of coordinates and the form of the metric
functions that describe the solution is given by providing that analytic
function which characterizes the metric as well as the gauge.
| [
{
"created": "Thu, 14 Oct 2010 08:04:09 GMT",
"version": "v1"
}
] | 2010-10-15 | [
[
"Hernandez-Pastora",
"J. L.",
""
],
[
"Ospino",
"J.",
""
]
] | We solve the Einstein vacuum-equations for the case of static and axisymmetric solutions in a system of coordinates different from the Weyl standard one. We prove that there exists a class of solutions with the appropriate asymptotical behaviour which can be written in a simple compact form, in terms of a function that must satisfies certain Cauchy-Newman problem. The relation between the choice of coordinates and the form of the metric functions that describe the solution is given by providing that analytic function which characterizes the metric as well as the gauge. |
gr-qc/9301006 | Steve Carlip | S. Carlip | Real Tunneling Solutions and the Hartle-Hawking Wave Function | 10 pages, LaTeX, UCD-92-30 | Class.Quant.Grav.10:1057-1064,1993 | 10.1088/0264-9381/10/6/004 | null | gr-qc hep-th | null | A real tunneling solution is an instanton for the Hartle-Hawking path
integral with vanishing extrinsic curvature (vanishing ``momentum'') at the
boundary. Since the final momentum is fixed, its conjugate cannot be specified
freely; consequently, such an instanton will contribute to the wave function at
only one or a few isolated spatial geometries. I show that these geometries are
the extrema of the Hartle-Hawking wave function in the semiclassical
approximation, and provide some evidence that with a suitable choice of time
parameter, these extrema are the maxima of the wave function at a fixed time.
| [
{
"created": "Fri, 8 Jan 1993 21:37:54 GMT",
"version": "v1"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | A real tunneling solution is an instanton for the Hartle-Hawking path integral with vanishing extrinsic curvature (vanishing ``momentum'') at the boundary. Since the final momentum is fixed, its conjugate cannot be specified freely; consequently, such an instanton will contribute to the wave function at only one or a few isolated spatial geometries. I show that these geometries are the extrema of the Hartle-Hawking wave function in the semiclassical approximation, and provide some evidence that with a suitable choice of time parameter, these extrema are the maxima of the wave function at a fixed time. |
1905.00030 | B\'eatrice Bonga | B\'eatrice Bonga, Huan Yang and Scott A. Hughes | Tidal resonance in extreme mass-ratio inspirals | 5 pages; v2: matches version published in PRL | Phys. Rev. Lett. 123, 101103 (2019) | 10.1103/PhysRevLett.123.101103 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a new class of resonances for extreme mass-ratio inspirals
(EMRIs): tidal resonances, induced by the tidal field of nearby stars or
stellar-mass black holes. A tidal resonance can be viewed as a general
relativistic extension of the Kozai-Lidov resonances in Newtonian systems, and
is distinct from the transient resonance already known for EMRI systems. Tidal
resonances will generically occur for EMRIs. By probing their influence on the
phase of an EMRI waveform, we can learn about the tidal environmental of the
EMRI system, albeit at the cost of a more complicated waveform model.
Observations by LISA of EMRI systems therefore have the potential to provide
information about the distribution of stellar-mass objects near their host
galactic-center black holes.
| [
{
"created": "Tue, 30 Apr 2019 18:00:03 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Sep 2019 18:03:29 GMT",
"version": "v2"
}
] | 2019-09-24 | [
[
"Bonga",
"Béatrice",
""
],
[
"Yang",
"Huan",
""
],
[
"Hughes",
"Scott A.",
""
]
] | We describe a new class of resonances for extreme mass-ratio inspirals (EMRIs): tidal resonances, induced by the tidal field of nearby stars or stellar-mass black holes. A tidal resonance can be viewed as a general relativistic extension of the Kozai-Lidov resonances in Newtonian systems, and is distinct from the transient resonance already known for EMRI systems. Tidal resonances will generically occur for EMRIs. By probing their influence on the phase of an EMRI waveform, we can learn about the tidal environmental of the EMRI system, albeit at the cost of a more complicated waveform model. Observations by LISA of EMRI systems therefore have the potential to provide information about the distribution of stellar-mass objects near their host galactic-center black holes. |
gr-qc/0605149 | Lau Loi So | Lau Loi So | A modification of the Chen-Nester quasilocal expressions | 11 pages | Int.J.Mod.Phys.D16:875-884,2007 | 10.1142/S0218271807010444 | null | gr-qc | null | Chen and Nester proposed four boundary expressions for the quasilocal
quantities using the covariant Hamiltonian formalism. Based on these four
expressions, there is a simple generalization that one can consider, so that a
two parameter set of boundary expressions can be constructed. Using these
modified expressions, a nice result for gravitational energy-momentum can be
obtained in holonomic frames.
| [
{
"created": "Wed, 31 May 2006 09:23:09 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"So",
"Lau Loi",
""
]
] | Chen and Nester proposed four boundary expressions for the quasilocal quantities using the covariant Hamiltonian formalism. Based on these four expressions, there is a simple generalization that one can consider, so that a two parameter set of boundary expressions can be constructed. Using these modified expressions, a nice result for gravitational energy-momentum can be obtained in holonomic frames. |
gr-qc/9809008 | Alejandro Jakubi | Alejandro S. Jakubi | Generalized power expansions in cosmology | 22 pages, LaTeX, elsart.sty. To be published in Computer Physics
Communications Thematic Issue "Computer Algebra in Physics Research" | Comput.Phys.Commun. 115 (1998) 284-299 | 10.1016/S0010-4655(98)00131-3 | null | gr-qc | null | It is given an algorithm to obtain generalized power asymptotic expansions of
the solutions of the Einstein equations arising for several homogeneous
cosmological models. This allows to investigate their behavior near the initial
singularity or for large times. An implementation of this algorithm in the CAS
system Maple V Release 4 is described and detailed calculations for three
equations are shown.
| [
{
"created": "Tue, 1 Sep 1998 19:35:18 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Jakubi",
"Alejandro S.",
""
]
] | It is given an algorithm to obtain generalized power asymptotic expansions of the solutions of the Einstein equations arising for several homogeneous cosmological models. This allows to investigate their behavior near the initial singularity or for large times. An implementation of this algorithm in the CAS system Maple V Release 4 is described and detailed calculations for three equations are shown. |
0809.0537 | Celine Cattoen | Celine Cattoen (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington) | Cosmographic Hubble fits to the supernova data | 28 pages, 4 figures | Phys.Rev.D78:063501,2008 | 10.1103/PhysRevD.78.063501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hubble relation between distance and redshift is a purely cosmographic
relation that depends only on the symmetries of a FLRW spacetime, but does not
intrinsically make any dynamical assumptions. This suggests that it should be
possible to estimate the parameters defining the Hubble relation without making
any dynamical assumptions. To test this idea, we perform a number of
inter-related cosmographic fits to the legacy05 and gold06 supernova datasets.
Based on this supernova data, the "preponderance of evidence" certainly
suggests an accelerating universe. However we would argue that (unless one uses
additional dynamical and observational information) this conclusion is not
currently supported "beyond reasonable doubt". As part of the analysis we
develop two particularly transparent graphical representations of the
redshift-distance relation -- representations in which acceleration versus
deceleration reduces to the question of whether the relevant graph slopes up or
down. Turning to the details of the cosmographic fits, three issues in
particular concern us: First, the fitted value for the deceleration parameter
changes significantly depending on whether one performs a chi^2 fit to the
luminosity distance, proper motion distance or other suitable distance
surrogate. Second, the fitted value for the deceleration parameter changes
significantly depending on whether one uses the traditional redshift variable
z, or what we shall argue is on theoretical grounds an improved
parameterization y=z/(1+z). Third, the published estimates for systematic
uncertainties are sufficiently large that they certainly impact on, and to a
large extent undermine, the usual purely statistical tests of significance. We
conclude that the supernova data should be treated with some caution.
| [
{
"created": "Wed, 3 Sep 2008 02:09:57 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cattoen",
"Celine",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The Hubble relation between distance and redshift is a purely cosmographic relation that depends only on the symmetries of a FLRW spacetime, but does not intrinsically make any dynamical assumptions. This suggests that it should be possible to estimate the parameters defining the Hubble relation without making any dynamical assumptions. To test this idea, we perform a number of inter-related cosmographic fits to the legacy05 and gold06 supernova datasets. Based on this supernova data, the "preponderance of evidence" certainly suggests an accelerating universe. However we would argue that (unless one uses additional dynamical and observational information) this conclusion is not currently supported "beyond reasonable doubt". As part of the analysis we develop two particularly transparent graphical representations of the redshift-distance relation -- representations in which acceleration versus deceleration reduces to the question of whether the relevant graph slopes up or down. Turning to the details of the cosmographic fits, three issues in particular concern us: First, the fitted value for the deceleration parameter changes significantly depending on whether one performs a chi^2 fit to the luminosity distance, proper motion distance or other suitable distance surrogate. Second, the fitted value for the deceleration parameter changes significantly depending on whether one uses the traditional redshift variable z, or what we shall argue is on theoretical grounds an improved parameterization y=z/(1+z). Third, the published estimates for systematic uncertainties are sufficiently large that they certainly impact on, and to a large extent undermine, the usual purely statistical tests of significance. We conclude that the supernova data should be treated with some caution. |
1005.4314 | Mauro Cattani | M.Cattani | Einstein Gravitation Theory: Experimental Tests I | 12 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Einstein gravitation theory (EGT) we calculate the Schwarzschild
metric that is defined in the surrounding vacuum of a spherically symmetric
mass distribution, not in rotation. The field equations of the EGT with this
metric were applied to analyze the time dilation and the Doppler Effect of the
light in order to test the validity of the EGT. This article was written to
graduate and postgraduate students of Physics.
| [
{
"created": "Mon, 24 May 2010 11:49:09 GMT",
"version": "v1"
}
] | 2010-05-25 | [
[
"Cattani",
"M.",
""
]
] | Using the Einstein gravitation theory (EGT) we calculate the Schwarzschild metric that is defined in the surrounding vacuum of a spherically symmetric mass distribution, not in rotation. The field equations of the EGT with this metric were applied to analyze the time dilation and the Doppler Effect of the light in order to test the validity of the EGT. This article was written to graduate and postgraduate students of Physics. |
gr-qc/9508003 | null | Nemanja Kaloper | A No-Go Theorem in String Cosmology | 7 pages, latex, no figures, contributed talk at the 6th Canadian
Conference on General Relativity and Relativistic Astrophysics, University of
New Brunswick, Fredericton, NB, May 24-28 | null | null | McGill 95-41 | gr-qc | null | A no-go theorem pertaining to the graceful exit problem in Pre-Big-Bang
inflation is reviewed. It is shown that dilaton self-interactions and string
fluid sources fail to facilitate branch changing necessary to avoid
singularities. A comment on the failure of the higher genus corrections to
induce graceful exit is also included.
| [
{
"created": "Wed, 2 Aug 1995 20:25:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kaloper",
"Nemanja",
""
]
] | A no-go theorem pertaining to the graceful exit problem in Pre-Big-Bang inflation is reviewed. It is shown that dilaton self-interactions and string fluid sources fail to facilitate branch changing necessary to avoid singularities. A comment on the failure of the higher genus corrections to induce graceful exit is also included. |
2307.11798 | Amna Ali | Niyaz Uddin Molla, Amna Ali and Ujjal Debnath | Observational Signatures of Modified Bardeen Black Hole: Shadow and
Strong Gravitational Lensing | 20 pages, 30 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | This paper is devoted to studying the observational signatures modified by
Bardeen black hole via shadow and strong lensing observations. Influence of the
modified Bardeen black hole parameters q, g, and the parameter $\mu$ on the
shadow radius of the black hole have been investigated numerically and
graphically. Recently, EHT collaboration observed the image and shadow of
supermassive black holes $M87^*$ and $SgrA^*$ where the shadow angular diameter
$\theta_d=42\pm3$ for $M87^*$ and $\theta_d=51.8\pm2.3$ for $SgrA^*$. The
modified black hole parameters q and $\mu$ for the fixed value of g have been
constrained by the EHT collaboration data for the angular shadow diameter of
$M87^*$ and $SgrA^*$. It has been observed that the constrain ranges of the
parameters $\mu$ and $q$ of modified Bardeen black hole as $-0.89\leq \mu/8M^2
\leq 0.4$ and $0\leq |q|\leq 0.185$ for $M87^*$; and $-1.38\leq \mu/8M^2 \leq
0.1$ and $0\leq |q|\leq 0.058$ for $SgrA^*$, keeping the fixed value
$g/2M=0.2$. Modified Bardeen black holes with the additional parameters
$\mu$,$g$ and $q$ besides the mass M of the black hole as the supermassive
black holes $M87^*$ and $SgrA^*$; and it is observed that to be a viable
astrophysical black hole candidate. Furthermore, Gravitational lensing in the
strong field limit for modified Bardeen black hole has been investigated
numerically as well as graphically and compared to the other ordinary
astrophysical black hole such as Schwarzschild ($\mu=\&q=0$) and regular
Bardeen ($\mu=0$) black hole.
| [
{
"created": "Fri, 21 Jul 2023 09:46:23 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Nov 2023 12:55:58 GMT",
"version": "v2"
}
] | 2023-11-21 | [
[
"Molla",
"Niyaz Uddin",
""
],
[
"Ali",
"Amna",
""
],
[
"Debnath",
"Ujjal",
""
]
] | This paper is devoted to studying the observational signatures modified by Bardeen black hole via shadow and strong lensing observations. Influence of the modified Bardeen black hole parameters q, g, and the parameter $\mu$ on the shadow radius of the black hole have been investigated numerically and graphically. Recently, EHT collaboration observed the image and shadow of supermassive black holes $M87^*$ and $SgrA^*$ where the shadow angular diameter $\theta_d=42\pm3$ for $M87^*$ and $\theta_d=51.8\pm2.3$ for $SgrA^*$. The modified black hole parameters q and $\mu$ for the fixed value of g have been constrained by the EHT collaboration data for the angular shadow diameter of $M87^*$ and $SgrA^*$. It has been observed that the constrain ranges of the parameters $\mu$ and $q$ of modified Bardeen black hole as $-0.89\leq \mu/8M^2 \leq 0.4$ and $0\leq |q|\leq 0.185$ for $M87^*$; and $-1.38\leq \mu/8M^2 \leq 0.1$ and $0\leq |q|\leq 0.058$ for $SgrA^*$, keeping the fixed value $g/2M=0.2$. Modified Bardeen black holes with the additional parameters $\mu$,$g$ and $q$ besides the mass M of the black hole as the supermassive black holes $M87^*$ and $SgrA^*$; and it is observed that to be a viable astrophysical black hole candidate. Furthermore, Gravitational lensing in the strong field limit for modified Bardeen black hole has been investigated numerically as well as graphically and compared to the other ordinary astrophysical black hole such as Schwarzschild ($\mu=\&q=0$) and regular Bardeen ($\mu=0$) black hole. |
1511.05377 | Corneliu \c{S}ochichiu | Jaehun Lee and Corneliu Sochichiu | Action-angle variables in curved space-time | 8 pages, corrected misspelled name of one of authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a relativistic and curved space version of action- angle
variables for a particle trapped in a gravity and electromagnetic background
with time-like isometry. As an example, we consider a particle in AdS
background. Furthermore, we obtain the semiclassical quantisation of its energy
levels.
| [
{
"created": "Tue, 17 Nov 2015 12:27:28 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2015 07:28:41 GMT",
"version": "v2"
}
] | 2015-11-25 | [
[
"Lee",
"Jaehun",
""
],
[
"Sochichiu",
"Corneliu",
""
]
] | We construct a relativistic and curved space version of action- angle variables for a particle trapped in a gravity and electromagnetic background with time-like isometry. As an example, we consider a particle in AdS background. Furthermore, we obtain the semiclassical quantisation of its energy levels. |
1201.6448 | Hamid Reza Sepangi | Zahra Haghani, Hamid Reza Sepangi, Shahab Shahidi | Cosmological dynamics of brane f(R) gravity | 18 pages, 4 figures, to appear in JCAP | JCAP 02 (2012) 031 | 10.1088/1475-7516/2012/02/031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological dynamics of a brane world scenario where the bulk action is
taken as a generic function of the Ricci scalar is considered in a framework
where the use of the $\mathbb{Z}_2$ symmetry and Israel junction conditions are
relaxed. The corresponding cosmological solutions for some specific forms of
$f(\mc{R})$ are obtained and shown to be in the form of exponential as well as
power law for a vacuum brane space-time. It is shown that the existence of
matter dominated epoch for a bulk action in the form of a power law for $\cal
R$ can only be obtained in the presence of ordinary matter. Using phase space
analysis, we show that the universe must start from an unstable matter
dominated epoch and eventually falls into a stable accelerated expanding phase.
| [
{
"created": "Tue, 31 Jan 2012 05:07:02 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Mar 2012 07:47:52 GMT",
"version": "v2"
}
] | 2013-08-13 | [
[
"Haghani",
"Zahra",
""
],
[
"Sepangi",
"Hamid Reza",
""
],
[
"Shahidi",
"Shahab",
""
]
] | The cosmological dynamics of a brane world scenario where the bulk action is taken as a generic function of the Ricci scalar is considered in a framework where the use of the $\mathbb{Z}_2$ symmetry and Israel junction conditions are relaxed. The corresponding cosmological solutions for some specific forms of $f(\mc{R})$ are obtained and shown to be in the form of exponential as well as power law for a vacuum brane space-time. It is shown that the existence of matter dominated epoch for a bulk action in the form of a power law for $\cal R$ can only be obtained in the presence of ordinary matter. Using phase space analysis, we show that the universe must start from an unstable matter dominated epoch and eventually falls into a stable accelerated expanding phase. |
1510.04333 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Singular Inflationary Universe from $F(R)$ Gravity | null | null | 10.1103/PhysRevD.92.124024 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unlike crushing singularities, the so-called Type IV finite-time singularity
offers the possibility that the Universe passes smoothly through it, without
any catastrophic effects. Then the question is if the effects of a Type IV
singularity can be detected in the process of cosmic evolution. In this paper
we address this question in the context of $F(R)$ gravity. As we demonstrate,
the effects of a Type IV singularity appear in the Hubble flow parameters,
which determine the dynamical evolution of the cosmological system. So we study
various inflation models incorporating a Type IV singularity, with the
singularity occurring at the end of inflation. Particularly we study a toy
model and a singular version of the $R^2$ gravity Hubble rate. As we evince,
some of the Hubble flow parameters become singular at the singularity, an
effect which indicates that at that point a dynamical instability occurs. This
dynamical instability eventually indicates the graceful exit from inflation. We
demonstrate that the toy model has an unstable de Sitter point at the
singularity, so indeed graceful exit could be triggered. In the case of the
singular inflation model, graceful exit proceeds in the standard way. In the
case of the singular inflation model, we found various scenarios for singular
evolution, most of which are compatible with observations, and only one leads
to severe instabilities. We also compare the ordinary Starobinsky with the
singular inflation model, and we point out the qualitative and quantitative
differences. Finally, we study the late-time dynamics of the toy model and of
the singular inflation model and we demonstrate that the unification of early
and late-time acceleration can be achieved. We also show that it is possible to
achieve late-time acceleration similar to the $\Lambda$-Cold Dark Matter model.
| [
{
"created": "Wed, 14 Oct 2015 22:19:00 GMT",
"version": "v1"
}
] | 2015-12-23 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | Unlike crushing singularities, the so-called Type IV finite-time singularity offers the possibility that the Universe passes smoothly through it, without any catastrophic effects. Then the question is if the effects of a Type IV singularity can be detected in the process of cosmic evolution. In this paper we address this question in the context of $F(R)$ gravity. As we demonstrate, the effects of a Type IV singularity appear in the Hubble flow parameters, which determine the dynamical evolution of the cosmological system. So we study various inflation models incorporating a Type IV singularity, with the singularity occurring at the end of inflation. Particularly we study a toy model and a singular version of the $R^2$ gravity Hubble rate. As we evince, some of the Hubble flow parameters become singular at the singularity, an effect which indicates that at that point a dynamical instability occurs. This dynamical instability eventually indicates the graceful exit from inflation. We demonstrate that the toy model has an unstable de Sitter point at the singularity, so indeed graceful exit could be triggered. In the case of the singular inflation model, graceful exit proceeds in the standard way. In the case of the singular inflation model, we found various scenarios for singular evolution, most of which are compatible with observations, and only one leads to severe instabilities. We also compare the ordinary Starobinsky with the singular inflation model, and we point out the qualitative and quantitative differences. Finally, we study the late-time dynamics of the toy model and of the singular inflation model and we demonstrate that the unification of early and late-time acceleration can be achieved. We also show that it is possible to achieve late-time acceleration similar to the $\Lambda$-Cold Dark Matter model. |
1807.05024 | Changjun Gao | Shuang Yu and Changjun Gao | Quansinormal modes of static and spherically symmetric black holes with
the derivative coupling | 13 pages,7 figures. GRG accepted | General Relativity and Gravitation (2019) 51:16 | 10.1007/s10714-019-2500-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the quasinormal modes of a class of static and spherically
symmetric black holes with the derivative coupling. The derivative coupling has
rarely been paid attention to the study of black hole quasinormal modes.
Specifically, we study the effect of derivative coupling on the quasinormal
modes for four kinds of black holes. They are Reissner-Nordstrom black holes,
Bardeen black holes, noncommunicative geometry inspired black holes and dilaton
black holes. These black holes are not the solutions of vacuum Einstein
equations which guarantees the effect of derivative coupling is not trivial. We
find the influence of derivative coupling on the quasinormal modes roughly
mimics the overtone numbers. In other words, there is a qualitative similarity
in the trend of quasinormal modes frequencies due to increasing either the
coupling constant and the overtone number.
| [
{
"created": "Fri, 13 Jul 2018 11:57:00 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Dec 2018 07:06:23 GMT",
"version": "v2"
}
] | 2019-01-23 | [
[
"Yu",
"Shuang",
""
],
[
"Gao",
"Changjun",
""
]
] | We investigate the quasinormal modes of a class of static and spherically symmetric black holes with the derivative coupling. The derivative coupling has rarely been paid attention to the study of black hole quasinormal modes. Specifically, we study the effect of derivative coupling on the quasinormal modes for four kinds of black holes. They are Reissner-Nordstrom black holes, Bardeen black holes, noncommunicative geometry inspired black holes and dilaton black holes. These black holes are not the solutions of vacuum Einstein equations which guarantees the effect of derivative coupling is not trivial. We find the influence of derivative coupling on the quasinormal modes roughly mimics the overtone numbers. In other words, there is a qualitative similarity in the trend of quasinormal modes frequencies due to increasing either the coupling constant and the overtone number. |
gr-qc/0612055 | Puxun Wu | Puxun Wu and Hongwei Yu | Generalized Chaplygin gas model: constraints from Hubble parameter
versus Redshift Data | 13 pages, 5 figures, to appear in PLB | Phys.Lett.B644:16-19,2007 | 10.1016/j.physletb.2006.11.028 | null | gr-qc | null | We examine observational constraints on the generalized Chaplygin gas (GCG)
model for dark energy from the 9 Hubble parameter data points, the 115 SNLS Sne
Ia data and the size of baryonic acoustic oscillation peak at redshift,
$z=0.35$. At a 95.4% confidence level, a combination of three data sets gives
$0.67\leq A_s\leq 0.83$ and $-0.21\leq \alpha\leq 0.42$, which is within the
allowed parameters ranges of the GCG as a candidate of the unified dark matter
and dark energy. It is found that the standard Chaplygin gas model ($\alpha=1$)
is ruled out by these data at the 99.7% confidence level.
| [
{
"created": "Sat, 9 Dec 2006 02:43:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | We examine observational constraints on the generalized Chaplygin gas (GCG) model for dark energy from the 9 Hubble parameter data points, the 115 SNLS Sne Ia data and the size of baryonic acoustic oscillation peak at redshift, $z=0.35$. At a 95.4% confidence level, a combination of three data sets gives $0.67\leq A_s\leq 0.83$ and $-0.21\leq \alpha\leq 0.42$, which is within the allowed parameters ranges of the GCG as a candidate of the unified dark matter and dark energy. It is found that the standard Chaplygin gas model ($\alpha=1$) is ruled out by these data at the 99.7% confidence level. |
gr-qc/9807083 | Hyeong-Chan Kim | Hyeong-Chan Kim, Yoonbai Kim, Phillial Oh | Black Hole Entropy and Exclusion Statistics | REVTeX file, 12 pages | null | null | SNUTP/98-065, MIT-CTP/2766 | gr-qc | null | We compute the entropy of systems of quantum particles satisfying the
fractional exclusion statistics in the space-time of 2+1 dimensional black hole
by using the brick-wall method. We show that the entropy of each effective
quantum field theory with a Planck scale ultraviolet cutoff obeys the area law,
irrespective of the angular momentum of the black hole and the statistics
interpolating between Bose-Einstein and Fermi-Dirac statistics.
| [
{
"created": "Thu, 30 Jul 1998 14:46:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kim",
"Hyeong-Chan",
""
],
[
"Kim",
"Yoonbai",
""
],
[
"Oh",
"Phillial",
""
]
] | We compute the entropy of systems of quantum particles satisfying the fractional exclusion statistics in the space-time of 2+1 dimensional black hole by using the brick-wall method. We show that the entropy of each effective quantum field theory with a Planck scale ultraviolet cutoff obeys the area law, irrespective of the angular momentum of the black hole and the statistics interpolating between Bose-Einstein and Fermi-Dirac statistics. |
gr-qc/9707003 | Martin Goliath | Kjell Rosquist and Martin Goliath | Lax pair tensors and integrable spacetimes | 10 pages, LaTeX | Gen.Rel.Grav. 30 (1998) 1521-1534 | 10.1023/A:1018817209424 | null | gr-qc nlin.SI solv-int | null | The use of Lax pair tensors as a unifying framework for Killing tensors of
arbitrary rank is discussed. Some properties of the tensorial Lax pair
formulation are stated. A mechanical system with a well-known Lax
representation -- the three-particle open Toda lattice -- is geometrized by a
suitable canonical transformation. In this way the Toda lattice is realized as
the geodesic system of a certain Riemannian geometry. By using different
canonical transformations we obtain two inequivalent geometries which both
represent the original system. Adding a timelike dimension gives
four-dimensional spacetimes which admit two Killing vector fields and are
completely integrable.
| [
{
"created": "Wed, 2 Jul 1997 08:18:39 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Rosquist",
"Kjell",
""
],
[
"Goliath",
"Martin",
""
]
] | The use of Lax pair tensors as a unifying framework for Killing tensors of arbitrary rank is discussed. Some properties of the tensorial Lax pair formulation are stated. A mechanical system with a well-known Lax representation -- the three-particle open Toda lattice -- is geometrized by a suitable canonical transformation. In this way the Toda lattice is realized as the geodesic system of a certain Riemannian geometry. By using different canonical transformations we obtain two inequivalent geometries which both represent the original system. Adding a timelike dimension gives four-dimensional spacetimes which admit two Killing vector fields and are completely integrable. |
0707.2749 | Boris Kosyakov | B.P.Kosyakov | Black holes: interfacing the classical and the quantum | comment: LaTeX, 12 pages | Found.Phys.38:678-694,2008 | 10.1007/s10701-008-9227-z | null | gr-qc | null | The central idea advocated in this paper is that {forming the black hole
horizon is attended with transition from the classical regime of evolution to
the quantum one}. We justify the following criterion for discriminating between
the classical and the quantum: {spontaneous creations and annihilations of
particle-antiparticle pairs are impossible in the classical world but possible
in the quantum world}. We show that it is sufficient to {change the overall
sign of the spacetime signature in the classical picture of field propagation
for it to be treated as its associated quantum picture}. To describe a
self-gravitating object at the last stage of its classical evolution, we
propose to use the Foldy--Wouthuysen representation of the Dirac equation in
curved spacetimes, and the Gozzi classical path integral. In both approaches,
maintaining the dynamics in the classical regime is controlled by
supersymmetry.
| [
{
"created": "Wed, 18 Jul 2007 15:36:54 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kosyakov",
"B. P.",
""
]
] | The central idea advocated in this paper is that {forming the black hole horizon is attended with transition from the classical regime of evolution to the quantum one}. We justify the following criterion for discriminating between the classical and the quantum: {spontaneous creations and annihilations of particle-antiparticle pairs are impossible in the classical world but possible in the quantum world}. We show that it is sufficient to {change the overall sign of the spacetime signature in the classical picture of field propagation for it to be treated as its associated quantum picture}. To describe a self-gravitating object at the last stage of its classical evolution, we propose to use the Foldy--Wouthuysen representation of the Dirac equation in curved spacetimes, and the Gozzi classical path integral. In both approaches, maintaining the dynamics in the classical regime is controlled by supersymmetry. |
0904.0574 | Francesco Cianfrani dr | Francesco Cianfrani, Giovanni Montani | Review on Extended Approaches in the Kaluza-Klein Model | 5 pages, Proceedings of The 3rd Stueckelberg Workshop on Relativistic
Field Theories | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A review of the Kaluza-Klein formulation is provided, with a particular
emphasis on the geometrization issue. The failure at reproducing quantum
numbers of particles and the appearance of huge mass terms are outlined. The
possibility to solve these points by an extended approach based on an averaging
procedure is discussed.
| [
{
"created": "Fri, 3 Apr 2009 13:23:39 GMT",
"version": "v1"
}
] | 2009-04-06 | [
[
"Cianfrani",
"Francesco",
""
],
[
"Montani",
"Giovanni",
""
]
] | A review of the Kaluza-Klein formulation is provided, with a particular emphasis on the geometrization issue. The failure at reproducing quantum numbers of particles and the appearance of huge mass terms are outlined. The possibility to solve these points by an extended approach based on an averaging procedure is discussed. |
gr-qc/0207122 | Pascual-Sanchez J.-F. | J.-F. Pascual-S\'anchez | TELEPENSOUTH project: Measurement of the Earth gravitomagnetic field in
a terrestrial laboratory | 7 pages, LaTeX, Springer style files included. Contribution to the
Proceedings of the Spanish Relativity Meeting-ERE-2001 (Madrid, September
2001). To appear in the book "Relativistic Astrophysics", Lecture Notes in
Physics, Springer Verlag (2002), edited by L. Fernandez-Jambrina, L.M.
Gonzalez-Romero | Lect.Notes Phys. 617 (2003) 330-336 | 10.1007/3-540-36973-2_20 | null | gr-qc astro-ph | null | We will expose a preliminary study on the feasibility of an experiment
leading to a direct measurement of the gravitomagnetic field generated by the
rotational motion of the Earth. This measurement would be achieved by means of
an appropriate coupling of a TELEscope and a Foucault PENdulum in a laboratory
on ground, preferably at the SOUTH pole. An experiment of this kind was firstly
proposed by Braginski, Polnarev and Thorne, 18 years ago, but it was never
re-analyzed.
| [
{
"created": "Tue, 30 Jul 2002 21:35:16 GMT",
"version": "v1"
}
] | 2022-09-21 | [
[
"Pascual-Sánchez",
"J. -F.",
""
]
] | We will expose a preliminary study on the feasibility of an experiment leading to a direct measurement of the gravitomagnetic field generated by the rotational motion of the Earth. This measurement would be achieved by means of an appropriate coupling of a TELEscope and a Foucault PENdulum in a laboratory on ground, preferably at the SOUTH pole. An experiment of this kind was firstly proposed by Braginski, Polnarev and Thorne, 18 years ago, but it was never re-analyzed. |
2206.08689 | Igor Yu. Potemine | Igor Yu. Potemine | Hyperverse, 5-dimensional gravity and multiverses as nested
Gogberashvili shells | 8 pages, 1 figure | null | 10.4236/jhepgc.2022.84069 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider the Hyperverse as a collection of multiverses in 5-dimensional
spacetime with gravitational constant $G$. Each multiverse in our simplified
model is a bouquet of nested spherical Gogberashvili shells. If $g_k$ is the
gravitational constant of a thin shell $S_k$ and $\varepsilon_k^{}$ its
thickness then $G\sim\varepsilon_k^{}g_k^{}$. The physical universe is supposed
to be one of those shells inside the local nested bouquet called Local
Multiverse. We relate this construction to Robinson-Trautman metrics describing
expanding spacetimes with spherical gravitational waves. Supermassive
astronomical black holes, located at cores of elliptic/spiral galaxies, are
also conjecturally described within this theory. Our constructions are equally
consistent with the modern theory of cosmological coupling.
| [
{
"created": "Fri, 17 Jun 2022 11:16:34 GMT",
"version": "v1"
}
] | 2024-04-23 | [
[
"Potemine",
"Igor Yu.",
""
]
] | We consider the Hyperverse as a collection of multiverses in 5-dimensional spacetime with gravitational constant $G$. Each multiverse in our simplified model is a bouquet of nested spherical Gogberashvili shells. If $g_k$ is the gravitational constant of a thin shell $S_k$ and $\varepsilon_k^{}$ its thickness then $G\sim\varepsilon_k^{}g_k^{}$. The physical universe is supposed to be one of those shells inside the local nested bouquet called Local Multiverse. We relate this construction to Robinson-Trautman metrics describing expanding spacetimes with spherical gravitational waves. Supermassive astronomical black holes, located at cores of elliptic/spiral galaxies, are also conjecturally described within this theory. Our constructions are equally consistent with the modern theory of cosmological coupling. |
gr-qc/9912118 | Steven Carlip | S. Carlip | Black Hole Entropy from Horizon Conformal Field Theory | 8 pages, LaTeX; talk given at QG99,``Constrained Dynamics and Quantum
Gravity,'' Villasimius, Sept. 1999 | Nucl.Phys.Proc.Suppl.88:10-16,2000 | 10.1016/S0920-5632(00)00748-9 | null | gr-qc hep-th | null | String theory and ``quantum geometry'' have recently offered independent
statistical mechanical explanations of black hole thermodynamics. But these
successes raise a new problem: why should models with such different
microscopic degrees of freedom yield identical results? I propose that the
asymptotic behavior of the density of states at a black hole horizon may be
determined by an underlying symmetry inherited from classical general
relativity, independent of the details of quantum gravity. I offer evidence
that a two-dimensional conformal symmetry at the horizon, with a classical
central extension, may provide the needed behavior.
| [
{
"created": "Wed, 29 Dec 1999 20:44:22 GMT",
"version": "v1"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | String theory and ``quantum geometry'' have recently offered independent statistical mechanical explanations of black hole thermodynamics. But these successes raise a new problem: why should models with such different microscopic degrees of freedom yield identical results? I propose that the asymptotic behavior of the density of states at a black hole horizon may be determined by an underlying symmetry inherited from classical general relativity, independent of the details of quantum gravity. I offer evidence that a two-dimensional conformal symmetry at the horizon, with a classical central extension, may provide the needed behavior. |
1603.07621 | Kenji Tomita | Kenji Tomita | Note on Nariai and Tomita's and Starobinsky's cosmological solutions in
the R^2 modified gravity | 5 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological solutions derived by Nariai and Tomita (1971) and by Starobinsky
(1980) are compared, and it is shown that the former derived de Sitter
expansion in the R^2 modified gravity (without cosmological constant) at the
earliest stage, and nine years later the latter derived the well-known
inflationary solution. Next the property of their simplified models is
described using the method of conformal transformations, and how the inflation
arises and the singularity is avoided is shown. Finally the initial and final
states of the inflation are discussed.
| [
{
"created": "Sun, 20 Mar 2016 06:53:57 GMT",
"version": "v1"
}
] | 2016-03-25 | [
[
"Tomita",
"Kenji",
""
]
] | Cosmological solutions derived by Nariai and Tomita (1971) and by Starobinsky (1980) are compared, and it is shown that the former derived de Sitter expansion in the R^2 modified gravity (without cosmological constant) at the earliest stage, and nine years later the latter derived the well-known inflationary solution. Next the property of their simplified models is described using the method of conformal transformations, and how the inflation arises and the singularity is avoided is shown. Finally the initial and final states of the inflation are discussed. |
1912.01869 | Giampiero Esposito Dr. | Donato Bini, Giampiero Esposito | New solutions of the Ermakov-Pinney equation in curved space-time | 20 pages, 10 figures. The presentation has been improved | null | 10.1007/s10714-020-02713-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An Ermakov-Pinney-like equation associated with the scalar wave equation in
curved space-time is here studied. The example of Schwarzschild space-time
considered in the present work shows that this equation can be viewed more as a
model equation, with interesting applications in black hole physics. Other
applications studied involve cosmological space-times (de Sitter) and pulse of
plane gravitational waves. In all these cases the evolution of the
Ermakov-Pinney field seems to be consistent with a rapid blow-up, unlike the
Schwarzschild case where spatially damped oscillations are allowed. Eventually,
the phase function is also evaluated in many of the above space-time models.
| [
{
"created": "Wed, 4 Dec 2019 09:57:50 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Apr 2020 07:21:32 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"Bini",
"Donato",
""
],
[
"Esposito",
"Giampiero",
""
]
] | An Ermakov-Pinney-like equation associated with the scalar wave equation in curved space-time is here studied. The example of Schwarzschild space-time considered in the present work shows that this equation can be viewed more as a model equation, with interesting applications in black hole physics. Other applications studied involve cosmological space-times (de Sitter) and pulse of plane gravitational waves. In all these cases the evolution of the Ermakov-Pinney field seems to be consistent with a rapid blow-up, unlike the Schwarzschild case where spatially damped oscillations are allowed. Eventually, the phase function is also evaluated in many of the above space-time models. |
gr-qc/9803018 | Jorge Pullin | Rodolfo Gambini, Jorge Griego, Jorge Pullin | Vassiliev invariants: a new framework for quantum gravity | 15 pages, several figures included with psfig | Nucl.Phys. B534 (1998) 675-696 | 10.1016/S0550-3213(98)80012-6 | CGPG-98/3-1 | gr-qc | null | We show that Vassiliev invariants of knots, appropriately generalized to the
spin network context, are loop differentiable in spite of being diffeomorphism
invariant. This opens the possibility of defining rigorously the constraints of
quantum gravity as geometrical operators acting on the space of Vassiliev
invariants of spin nets. We show how to explicitly realize the diffeomorphism
constraint on this space and present proposals for the construction of
Hamiltonian constraints.
| [
{
"created": "Thu, 5 Mar 1998 05:36:10 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Griego",
"Jorge",
""
],
[
"Pullin",
"Jorge",
""
]
] | We show that Vassiliev invariants of knots, appropriately generalized to the spin network context, are loop differentiable in spite of being diffeomorphism invariant. This opens the possibility of defining rigorously the constraints of quantum gravity as geometrical operators acting on the space of Vassiliev invariants of spin nets. We show how to explicitly realize the diffeomorphism constraint on this space and present proposals for the construction of Hamiltonian constraints. |
1810.02725 | Nadia Bolis | Nadia Bolis, Constantinos Skordis, Daniel B Thomas, Tom Zlosnik | The Parameterized Post-Newtonian-Vainshteinian formalism for the
Galileon field | 18 pages, 2 figure | Phys. Rev. D 99, 084009 (2019) | 10.1103/PhysRevD.99.084009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, an extension to the Parameterized Post-Newtonian (PPN) formalism
has been proposed. This formalism, the Parameterized
Post-Newtonian-Vainshteinian (PPNV) formalism, is well suited to theories which
exhibit Vainshtein screening of scalar fields. In this paper we apply the PPNV
formalism to the Quartic and Quintic Galileon theories for the first time. As
simple generalizations of standard scalar-tensor field theories they are
important guides for the generalization of parameterized approaches to the
effects of gravity beyond General Relativity. In the Quartic case, we find new
PPNV potentials for both screened and un-screened regions of spacetime, showing
that in principle these theories can be tested. In the Quintic case we show
that Vainshtein screening does not occur to Newtonian order, meaning that the
theory behaves as Brans-Dicke to this order, and we discuss possible higher
order effects.
| [
{
"created": "Fri, 5 Oct 2018 14:42:48 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Mar 2019 14:06:43 GMT",
"version": "v2"
}
] | 2019-04-17 | [
[
"Bolis",
"Nadia",
""
],
[
"Skordis",
"Constantinos",
""
],
[
"Thomas",
"Daniel B",
""
],
[
"Zlosnik",
"Tom",
""
]
] | Recently, an extension to the Parameterized Post-Newtonian (PPN) formalism has been proposed. This formalism, the Parameterized Post-Newtonian-Vainshteinian (PPNV) formalism, is well suited to theories which exhibit Vainshtein screening of scalar fields. In this paper we apply the PPNV formalism to the Quartic and Quintic Galileon theories for the first time. As simple generalizations of standard scalar-tensor field theories they are important guides for the generalization of parameterized approaches to the effects of gravity beyond General Relativity. In the Quartic case, we find new PPNV potentials for both screened and un-screened regions of spacetime, showing that in principle these theories can be tested. In the Quintic case we show that Vainshtein screening does not occur to Newtonian order, meaning that the theory behaves as Brans-Dicke to this order, and we discuss possible higher order effects. |
0908.4476 | Simone Speziale | J. Daniel Christensen, Igor Khavkine, Etera R. Livine and Simone
Speziale | Sub-leading asymptotic behaviour of area correlations in the
Barrett-Crane model | 20 pages, 15 figures | Class.Quant.Grav.27:035012,2010 | 10.1088/0264-9381/27/3/035012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Barrett-Crane spin foam model for quantum gravity provides an excellent
setting for testing analytical and numerical tools used to probe spinfoam
models. Here, we complete the report on the numerical analysis of the single
4-simplex area correlations begun in Phys. Lett. B670 (2009) 403-406,
discussing the next-to-leading order corrections ("one-loop" corrections) with
particular attention to their measure dependence, and the difference between
the Gaussian and Bessel ansatze for the boundary state.
| [
{
"created": "Mon, 31 Aug 2009 08:39:00 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Christensen",
"J. Daniel",
""
],
[
"Khavkine",
"Igor",
""
],
[
"Livine",
"Etera R.",
""
],
[
"Speziale",
"Simone",
""
]
] | The Barrett-Crane spin foam model for quantum gravity provides an excellent setting for testing analytical and numerical tools used to probe spinfoam models. Here, we complete the report on the numerical analysis of the single 4-simplex area correlations begun in Phys. Lett. B670 (2009) 403-406, discussing the next-to-leading order corrections ("one-loop" corrections) with particular attention to their measure dependence, and the difference between the Gaussian and Bessel ansatze for the boundary state. |
2101.10802 | Morteza Kerachian | M. Kerachian and G. Acquaviva and G. Lukes-Gerakopoulos | Dynamical analysis approaches in spatially curved FRW spacetimes | 11 pages, 2 figures, 1 table | Proceedings of RAGtime 20-22, 15-19 Oct., 16-20 Sept., 19-23 Oct.,
2018/2019/2020, Opava, Czech Republic, Z. Stuchlik, G. Torok and V. Karas,
editors, Silesian University in Opava, 2020, pp. 133-143 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we summarize two agnostic approaches in the framework of
spatially curved Friedmann-Robertson-Walker (FRW) cosmologies discussed in
detail in (Kerachian et al., 2020, 2019). The first case concerns the dynamics
of a fluid with an unspecified barotropic equation of state (EoS), for which
the only assumption made is the non-negativity of the fluid's energy density.
The second case concerns the dynamics of a non-minimally coupled real scalar
field with unspecified positive potential. For each of these models, we define
a new set of dimensionless variables and a new evolution parameter. In the
framework of these agnostic setups, we are able to identify several general
features, like symmetries, invariant subsets and critical points, and provide
their cosmological interpretation.
| [
{
"created": "Tue, 26 Jan 2021 14:26:09 GMT",
"version": "v1"
}
] | 2021-01-27 | [
[
"Kerachian",
"M.",
""
],
[
"Acquaviva",
"G.",
""
],
[
"Lukes-Gerakopoulos",
"G.",
""
]
] | In this article, we summarize two agnostic approaches in the framework of spatially curved Friedmann-Robertson-Walker (FRW) cosmologies discussed in detail in (Kerachian et al., 2020, 2019). The first case concerns the dynamics of a fluid with an unspecified barotropic equation of state (EoS), for which the only assumption made is the non-negativity of the fluid's energy density. The second case concerns the dynamics of a non-minimally coupled real scalar field with unspecified positive potential. For each of these models, we define a new set of dimensionless variables and a new evolution parameter. In the framework of these agnostic setups, we are able to identify several general features, like symmetries, invariant subsets and critical points, and provide their cosmological interpretation. |
0805.1417 | Gerald Marsh | Gerald E. Marsh | Charge, geometry, and effective mass in the Kerr-Newman solution to the
Einstein field equations | To appear in Foundations of Physics. Misprints have been corrected.
14 pages, 4 figures | null | 10.1007/s10701-008-9245-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that for the Reissner-Nordstrom solution to the vacuum
Einstein field equations charge, like mass, has a unique space-time signature
[Found. Phys. 38, 293-300 (2008)]. The presence of charge results in a negative
curvature. This work, which includes a discussion of effective mass, is
extended here to the Kerr-Newman solution.
| [
{
"created": "Fri, 9 May 2008 20:16:53 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Oct 2008 19:31:57 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Marsh",
"Gerald E.",
""
]
] | It has been shown that for the Reissner-Nordstrom solution to the vacuum Einstein field equations charge, like mass, has a unique space-time signature [Found. Phys. 38, 293-300 (2008)]. The presence of charge results in a negative curvature. This work, which includes a discussion of effective mass, is extended here to the Kerr-Newman solution. |
0809.1571 | Claude Warnick | G. W. Gibbons, C. M. Warnick | Universal properties of the near-horizon optical geometry | null | Phys.Rev.D79:064031,2009 | 10.1103/PhysRevD.79.064031 | DAMTP-2008-80 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make use of the fact that the optical geometry near a static
non-degenerate Killing horizon is asymptotically hyperbolic to investigate
universal features of black hole physics. We show how the Gauss-Bonnet theorem
allows certain lensing scenarios to be ruled in or out. We find rates for the
loss of scalar, vector and fermionic `hair' as objects fall quasi- statically
towards the horizon. In the process we find the Lienard-Wiechert potential for
hyperbolic space and calculate the force between electrons mediated by
neutrinos, extending the flat space result of Feinberg and Sucher. We use the
enhanced conformal symmetry of the Schwarzschild and Reissner-Nordstrom
backgrounds to re-derive the electrostatic field due to a point charge in a
simple fashion.
| [
{
"created": "Tue, 9 Sep 2008 14:42:03 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Gibbons",
"G. W.",
""
],
[
"Warnick",
"C. M.",
""
]
] | We make use of the fact that the optical geometry near a static non-degenerate Killing horizon is asymptotically hyperbolic to investigate universal features of black hole physics. We show how the Gauss-Bonnet theorem allows certain lensing scenarios to be ruled in or out. We find rates for the loss of scalar, vector and fermionic `hair' as objects fall quasi- statically towards the horizon. In the process we find the Lienard-Wiechert potential for hyperbolic space and calculate the force between electrons mediated by neutrinos, extending the flat space result of Feinberg and Sucher. We use the enhanced conformal symmetry of the Schwarzschild and Reissner-Nordstrom backgrounds to re-derive the electrostatic field due to a point charge in a simple fashion. |
0805.0519 | Rakesh Tibrewala | Cenalo Vaz, Rakesh Tibrewala and T.P. Singh | Classical and Quantum Gravitational Collapse in d-dim AdS Spacetime II.
Quantum States and Hawking Radiation | 20 pages | Phys.Rev.D78:024019,2008 | 10.1103/PhysRevD.78.024019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous paper we studied the collapse of a spherically symmetric dust
distribution (marginally bound LTB) in d-dimensional AdS spacetime and obtained
the condition for the formation of trapped surfaces. Here we extend the
analysis by giving the canonical theory for the same and subsequently quantize
the system by solving the Wheeler-DeWitt equation. We show that for the case of
small dust perturbations around a black hole the wave functionals so obtained
describe an AdS-Schwarzschild black hole in equilibrium with a thermal bath at
Hawking temperature and show the non-trivial dependence of this temperature on
the number of spacetime dimensions and the cosmological constant.
| [
{
"created": "Mon, 5 May 2008 12:37:06 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Vaz",
"Cenalo",
""
],
[
"Tibrewala",
"Rakesh",
""
],
[
"Singh",
"T. P.",
""
]
] | In a previous paper we studied the collapse of a spherically symmetric dust distribution (marginally bound LTB) in d-dimensional AdS spacetime and obtained the condition for the formation of trapped surfaces. Here we extend the analysis by giving the canonical theory for the same and subsequently quantize the system by solving the Wheeler-DeWitt equation. We show that for the case of small dust perturbations around a black hole the wave functionals so obtained describe an AdS-Schwarzschild black hole in equilibrium with a thermal bath at Hawking temperature and show the non-trivial dependence of this temperature on the number of spacetime dimensions and the cosmological constant. |
2006.10462 | Antonina Zinhailo | R. A. Konoplya, A. F. Zinhailo and Z. Stuchlik | Quasinormal modes and Hawking radiation of black holes in cubic gravity | 10 pages, revtex, 11 figures, the version to match the published PRD
version A typo in formula 27 | Phys. Rev. D 102, 044023 (2020) | 10.1103/PhysRevD.102.044023 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider quasinormal modes and Hawking radiation of four-dimensional
asymptotically flat black holes in the most general up
to-cubic-order-in-curvature dimension-independent Einsteinian theory of gravity
that shares its graviton spectrum with the Einstein theory on constant
curvature backgrounds. We show that damping rate and real oscillation
frequencies of quasinormal modes for scalar, electromagnetic and Dirac fields
are suppressed once the coupling with the cubic term is on. The intensity of
Hawking radiation is suppressed as well, leading to, roughly, one order longer
lifetime at a sufficiently large coupling constant.
| [
{
"created": "Thu, 18 Jun 2020 12:16:09 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jun 2020 00:44:24 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Aug 2020 14:20:50 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Sep 2021 08:46:56 GMT",
"version": "v4"
}
] | 2021-09-20 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zinhailo",
"A. F.",
""
],
[
"Stuchlik",
"Z.",
""
]
] | We consider quasinormal modes and Hawking radiation of four-dimensional asymptotically flat black holes in the most general up to-cubic-order-in-curvature dimension-independent Einsteinian theory of gravity that shares its graviton spectrum with the Einstein theory on constant curvature backgrounds. We show that damping rate and real oscillation frequencies of quasinormal modes for scalar, electromagnetic and Dirac fields are suppressed once the coupling with the cubic term is on. The intensity of Hawking radiation is suppressed as well, leading to, roughly, one order longer lifetime at a sufficiently large coupling constant. |
1010.5090 | Francesco Cianfrani dr | Francesco Cianfrani, Giovanni Montani, Marco Muccino | Semi-Classical Isotropization of the Universe during a de Sitter phase | 6 pages, accepted for publication in Phys. Rev. D | Phys.Rev.D82:103524,2010 | 10.1103/PhysRevD.82.103524 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Semi-classical states for the Wheeler-DeWitt equation of a Bianchi type I
model in the presence of a scalar field are analyzed. It is outlined how this
scheme can effectively describe more general situations, where the curvature of
the Bianchi type IX model and a proper potential term for the scalar field are
present. The introduction of a cosmological constant term accounts for the
quasi-isotropization mechanism which bridges the proposed framework with a late
isotropic phase. This result makes the semi-classical Bianchi I model a
plausible scenario for the Universe pre-inflationary phase.
| [
{
"created": "Mon, 25 Oct 2010 11:13:25 GMT",
"version": "v1"
}
] | 2010-12-23 | [
[
"Cianfrani",
"Francesco",
""
],
[
"Montani",
"Giovanni",
""
],
[
"Muccino",
"Marco",
""
]
] | Semi-classical states for the Wheeler-DeWitt equation of a Bianchi type I model in the presence of a scalar field are analyzed. It is outlined how this scheme can effectively describe more general situations, where the curvature of the Bianchi type IX model and a proper potential term for the scalar field are present. The introduction of a cosmological constant term accounts for the quasi-isotropization mechanism which bridges the proposed framework with a late isotropic phase. This result makes the semi-classical Bianchi I model a plausible scenario for the Universe pre-inflationary phase. |
1808.03825 | Miguel Cruz | Miguel Cruz, Samuel Lepe and Sergei D. Odintsov | Thermodynamically allowed phantom cosmology with viscous fluid | 9 pages, 3 figures. Accepted version in PRD | Phys. Rev. D 98, 083515 (2018) | 10.1103/PhysRevD.98.083515 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present an analysis of the phantom zone in a causal viscous
cosmology from a thermodynamic point of view. In this description we consider a
chemical potential and the approach of irreversible processes. We assume a flat
universe filled with a single dissipative fluid described by a barotropic
equation of state, $p = \omega \rho$. This model allows to construct a negative
chemical potential for the phantom regime but also this construction allows us
to have positive definite temperature and entropy.
| [
{
"created": "Sat, 11 Aug 2018 16:12:21 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Sep 2018 15:45:03 GMT",
"version": "v2"
},
{
"created": "Sun, 30 Sep 2018 13:20:34 GMT",
"version": "v3"
}
] | 2018-10-11 | [
[
"Cruz",
"Miguel",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | In this work we present an analysis of the phantom zone in a causal viscous cosmology from a thermodynamic point of view. In this description we consider a chemical potential and the approach of irreversible processes. We assume a flat universe filled with a single dissipative fluid described by a barotropic equation of state, $p = \omega \rho$. This model allows to construct a negative chemical potential for the phantom regime but also this construction allows us to have positive definite temperature and entropy. |
gr-qc/0306112 | Glenn Barnich | Glenn Barnich, Friedemann Brandt and Kim Claes | Asymptotically anti-de Sitter space-times: symmetries and conservation
laws revisited | 6 pages Latex file, Proceedings for the conference "Renormalization
Group and Anomalies in Gravity and Cosmology", Ouro Preto, Brazil, 17 - 23
March, 2003 | null | 10.1016/S0920-5632(03)02410-1 | ULB-TH/03-26, MPI-MIS-51/2003 | gr-qc hep-th | null | In this short note, we verify explicitly in static coordinates that the non
trivial asymptotic Killing vectors at spatial infinity for anti-de Sitter
space-times correspond one to one to the conformal Killing vectors of the
conformally flat metric induced on the boundary. The fall-off conditions for
the metric perturbations that guarantee finiteness of the associated conserved
charges are derived.
| [
{
"created": "Wed, 25 Jun 2003 13:13:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Barnich",
"Glenn",
""
],
[
"Brandt",
"Friedemann",
""
],
[
"Claes",
"Kim",
""
]
] | In this short note, we verify explicitly in static coordinates that the non trivial asymptotic Killing vectors at spatial infinity for anti-de Sitter space-times correspond one to one to the conformal Killing vectors of the conformally flat metric induced on the boundary. The fall-off conditions for the metric perturbations that guarantee finiteness of the associated conserved charges are derived. |
2003.01934 | Aya Iyonaga | Aya Iyonaga, Kazufumi Takahashi and Tsutomu Kobayashi | Extended Cuscuton as Dark Energy | 12 pages, 2 figures | JCAP 07 (2020) 004 | 10.1088/1475-7516/2020/07/004 | RUP-20-6, KOBE-COSMO-20-02 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Late-time cosmology in the extended cuscuton theory is studied, in which
gravity is modified while one still has no extra dynamical degrees of freedom
other than two tensor modes. We present a simple example admitting analytic
solutions for the cosmological background evolution that mimics $\Lambda$CDM
cosmology. We argue that the extended cuscuton as dark energy can be
constrained, like usual scalar-tensor theories, by the growth history of matter
density perturbations and the time variation of Newton's constant.
| [
{
"created": "Wed, 4 Mar 2020 07:58:27 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jul 2020 14:51:37 GMT",
"version": "v2"
}
] | 2020-07-03 | [
[
"Iyonaga",
"Aya",
""
],
[
"Takahashi",
"Kazufumi",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] | Late-time cosmology in the extended cuscuton theory is studied, in which gravity is modified while one still has no extra dynamical degrees of freedom other than two tensor modes. We present a simple example admitting analytic solutions for the cosmological background evolution that mimics $\Lambda$CDM cosmology. We argue that the extended cuscuton as dark energy can be constrained, like usual scalar-tensor theories, by the growth history of matter density perturbations and the time variation of Newton's constant. |
1901.01363 | Hernando Quevedo | Antonio C. Guti\'errez-Pi\~neres and Hernando Quevedo | $C^3$ matching for asymptotically flat spacetimes | null | null | 10.1088/1361-6382/ab2422 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a criterion for finding the minimum distance at which an interior
solution of Einstein's equations can be matched with an exterior asymptotically
flat solution. It is based upon the analysis of the eigenvalues of the Riemann
curvature tensor and their first derivatives, implying $C^3$ differentiability
conditions. The matching itself is performed by demanding continuity of the
curvature eigenvalues across the matching surface. We apply the $C^3$ matching
approach to spherically symmetric perfect fluid spacetimes and obtain the
physically meaningful condition that density and pressure should vanish on the
matching surface. Several perfect fluid solutions in Newton and Einstein
gravity are tested.
| [
{
"created": "Sat, 5 Jan 2019 04:18:46 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"Quevedo",
"Hernando",
""
]
] | We propose a criterion for finding the minimum distance at which an interior solution of Einstein's equations can be matched with an exterior asymptotically flat solution. It is based upon the analysis of the eigenvalues of the Riemann curvature tensor and their first derivatives, implying $C^3$ differentiability conditions. The matching itself is performed by demanding continuity of the curvature eigenvalues across the matching surface. We apply the $C^3$ matching approach to spherically symmetric perfect fluid spacetimes and obtain the physically meaningful condition that density and pressure should vanish on the matching surface. Several perfect fluid solutions in Newton and Einstein gravity are tested. |
gr-qc/0407089 | Nikolaos Mavromatos | John Ellis (CERN), N.E. Mavromatos (King's Coll. Lon.), D.V.
Nanopoulos (TAMU) and A. Sakharov (CERN and ETH) | Brany Liouville Inflation | 23 pages LATEX, two eps figures incorporated; version accepted for
publication in NJP | New J.Phys.6:171,2004 | 10.1088/1367-2630/6/1/171 | CERN-PH-TH/2004-134 | gr-qc astro-ph hep-ph hep-th | null | We present a specific model for cosmological inflation driven by the
Liouville field in a non-critical supersymmetric string framework, in which the
departure from criticality is due to open strings stretched between the two
moving Type-II 5-branes. We use WMAP and other data on fluctuations in the
cosmic microwave background to fix parameters of the model, such as the
relative separation and velocity of the 5-branes, respecting also the
constraints imposed by data on light propagation from distant gamma-ray
bursters. The model also suggests a small, relaxing component in the present
vacuum energy that may accommodate the breaking of supersymmetry.
| [
{
"created": "Fri, 23 Jul 2004 15:23:17 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jul 2004 09:57:13 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Aug 2004 15:58:55 GMT",
"version": "v3"
},
{
"created": "Mon, 8 Nov 2004 13:56:55 GMT",
"version": "v4"
}
] | 2009-09-11 | [
[
"Ellis",
"John",
"",
"CERN"
],
[
"Mavromatos",
"N. E.",
"",
"King's Coll. Lon."
],
[
"Nanopoulos",
"D. V.",
"",
"TAMU"
],
[
"Sakharov",
"A.",
"",
"CERN and ETH"
]
] | We present a specific model for cosmological inflation driven by the Liouville field in a non-critical supersymmetric string framework, in which the departure from criticality is due to open strings stretched between the two moving Type-II 5-branes. We use WMAP and other data on fluctuations in the cosmic microwave background to fix parameters of the model, such as the relative separation and velocity of the 5-branes, respecting also the constraints imposed by data on light propagation from distant gamma-ray bursters. The model also suggests a small, relaxing component in the present vacuum energy that may accommodate the breaking of supersymmetry. |
1704.04961 | Grigoris Panotopoulos | Grigoris Panotopoulos | Strange stars in $f(R)$ theories of gravity in the Palatini formalism | 10 pages, 2 figures | Gen Relativ Gravit (2017) 49: 69 | 10.1007/s10714-017-2230-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we study strange stars in $f(R)$ theories of gravity in
the Palatini formalism. We consider two concrete well-known cases, namely the
$R+R^2/(6 M^2)$ model as well as the $R-\mu^4/R$ model for two different values
of the mass parameter $M$ or $\mu$. We integrate the modified
Tolman-Oppenheimer-Volkoff equations numerically, and we show the mass-radius
diagram for each model separately. The standard case corresponding to the
General Relativity is also shown in the same figure for comparison. Our
numerical results show that the interior solution can be vastly different
depending on the model and/or the value of the parameter of each model. In
addition, our findings imply that i) for the cosmologically interesting values
of the mass scales $M,\mu$ the effect of modified gravity on strange stars is
negligible, while ii) for the values predicting an observable effect, the
modified gravity models discussed here would be ruled out by their cosmological
effects.
| [
{
"created": "Mon, 17 Apr 2017 13:30:48 GMT",
"version": "v1"
}
] | 2017-05-03 | [
[
"Panotopoulos",
"Grigoris",
""
]
] | In the present work we study strange stars in $f(R)$ theories of gravity in the Palatini formalism. We consider two concrete well-known cases, namely the $R+R^2/(6 M^2)$ model as well as the $R-\mu^4/R$ model for two different values of the mass parameter $M$ or $\mu$. We integrate the modified Tolman-Oppenheimer-Volkoff equations numerically, and we show the mass-radius diagram for each model separately. The standard case corresponding to the General Relativity is also shown in the same figure for comparison. Our numerical results show that the interior solution can be vastly different depending on the model and/or the value of the parameter of each model. In addition, our findings imply that i) for the cosmologically interesting values of the mass scales $M,\mu$ the effect of modified gravity on strange stars is negligible, while ii) for the values predicting an observable effect, the modified gravity models discussed here would be ruled out by their cosmological effects. |
1806.06791 | Rhiannon Cuttell | Rhiannon Cuttell and Mairi Sakellariadou | Deformed general relativity and scalar-tensor models | 20 pages, 4 figures, authors' accepted manuscript | Class.Quant.Grav. 35, 225005, (2018) | 10.1088/1361-6382/aae442 | KCL-PH-TH/2018-26 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the most general action for a scalar-tensor model up to
quadratic order in derivatives with deformed general covariance and non-minimal
coupling. We demonstrate how different choices of the free functions recover
specific well known scalar-tensor models. We look at the cosmological dynamics
and find the general conditions for either inflation or a big bounce. Using
this we present a novel non-minimally coupled scalar model which produces a
bounce, and describe how to find similar models.
| [
{
"created": "Mon, 18 Jun 2018 15:59:50 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Oct 2018 15:11:48 GMT",
"version": "v2"
}
] | 2018-10-24 | [
[
"Cuttell",
"Rhiannon",
""
],
[
"Sakellariadou",
"Mairi",
""
]
] | We calculate the most general action for a scalar-tensor model up to quadratic order in derivatives with deformed general covariance and non-minimal coupling. We demonstrate how different choices of the free functions recover specific well known scalar-tensor models. We look at the cosmological dynamics and find the general conditions for either inflation or a big bounce. Using this we present a novel non-minimally coupled scalar model which produces a bounce, and describe how to find similar models. |
1203.2679 | Matilde Marcolli | Christopher Estrada and Matilde Marcolli | Noncommutative Mixmaster Cosmologies | 24 pages LaTeX | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate a variant of the classical mixmaster universe
model of anisotropic cosmology, where the spatial sections are noncommutative
3-tori. We consider ways in which the discrete dynamical system describing the
mixmaster dynamics can be extended to act on the noncommutative torus moduli,
and how the resulting dynamics differs from the classical one, for example, in
the appearance of exotic smooth structures. We discuss properties of the
spectral action, focussing on how the slow-roll inflation potential determined
by the spectral action affects the mixmaster dynamics. We relate the model to
other recent results on spectral action computation and we identify other
physical contexts in which this model may be relevant.
| [
{
"created": "Tue, 13 Mar 2012 00:31:43 GMT",
"version": "v1"
}
] | 2012-03-14 | [
[
"Estrada",
"Christopher",
""
],
[
"Marcolli",
"Matilde",
""
]
] | In this paper we investigate a variant of the classical mixmaster universe model of anisotropic cosmology, where the spatial sections are noncommutative 3-tori. We consider ways in which the discrete dynamical system describing the mixmaster dynamics can be extended to act on the noncommutative torus moduli, and how the resulting dynamics differs from the classical one, for example, in the appearance of exotic smooth structures. We discuss properties of the spectral action, focussing on how the slow-roll inflation potential determined by the spectral action affects the mixmaster dynamics. We relate the model to other recent results on spectral action computation and we identify other physical contexts in which this model may be relevant. |
gr-qc/0009025 | Michael L. Fil'chenkov | I.G. Dymnikova (Institute of Mathematics, Informatics and Physics,
University of Warmia and Mazury in Olsztyn, Olsztyn, Poland), M.L.
Fil'chenkov (Alexander Friedmann Laboratory for Theoretical Physics, St.
Petersburg, Russia; Institute of Gravitation and Cosmology, Peoples'
Friendship University of Russia, Moscow, Russia) | Quantum Birth of a Hot Universe | 9 pages, no figures, LaTex, submitted to Phys. Rev. D | Phys.Lett. B545 (2002) 214-220 | 10.1016/S0370-2693(02)02620-5 | null | gr-qc | null | We consider quantum birth of a hot Universe in the framework of quantum
qeometrodynamics in the minisuperspace model. The energy spectrum of the
Universe in the pre-de-Sitter domain naturally explains the cosmic microwave
background (CMB) anisotropy. The false vacuum where the Universe tunnels from
the pre-de-Sitter domain is assumed to be of a Grand Unification Theory (GUT)
scale. The probability of the birth of a hot Universe from a quantum level
proves to be about $10^{-10^{14}}$. In the presence of matter with a negative
pressure (quintessence) it is possible for open and flat universes to be born
as well as closed ones.
| [
{
"created": "Fri, 8 Sep 2000 22:40:10 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dymnikova",
"I. G.",
"",
"Institute of Mathematics, Informatics and Physics,\n University of Warmia and Mazury in Olsztyn, Olsztyn, Poland"
],
[
"Fil'chenkov",
"M. L.",
"",
"Alexander Friedmann Laboratory for Theoretical Physics, St.\n Petersburg, Russia; Institute of Gravitation and Cosmology, Peoples'\n Friendship University of Russia, Moscow, Russia"
]
] | We consider quantum birth of a hot Universe in the framework of quantum qeometrodynamics in the minisuperspace model. The energy spectrum of the Universe in the pre-de-Sitter domain naturally explains the cosmic microwave background (CMB) anisotropy. The false vacuum where the Universe tunnels from the pre-de-Sitter domain is assumed to be of a Grand Unification Theory (GUT) scale. The probability of the birth of a hot Universe from a quantum level proves to be about $10^{-10^{14}}$. In the presence of matter with a negative pressure (quintessence) it is possible for open and flat universes to be born as well as closed ones. |
1812.02835 | Roberto Pierini | Roberto Pierini, Shahpoor Moradi, and Stefano Mancini | Entanglement in anisotropic expanding spacetime | null | Eur. Phys. J. D (2019) 73: 33 | 10.1140/epjd/e2019-90463-y | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effect of space anisotropy in the entanglement generated by
expanding universe on spin 0 and 1/2 fields. For massive scalar field we find
revivals of entanglement entropy vs momentum after decreasing from the maximum
at k = 0. In massive Dirac field the effect is a slight distortion of the
non-monotonic profile giving rise to the maximum of entanglement entropy at k >
0. More interestingly, massless field of both type can only get entangled
through anisotropy, with a maximum of entanglement entropy occurring at k > 0.
| [
{
"created": "Thu, 6 Dec 2018 22:27:40 GMT",
"version": "v1"
}
] | 2019-03-13 | [
[
"Pierini",
"Roberto",
""
],
[
"Moradi",
"Shahpoor",
""
],
[
"Mancini",
"Stefano",
""
]
] | We study the effect of space anisotropy in the entanglement generated by expanding universe on spin 0 and 1/2 fields. For massive scalar field we find revivals of entanglement entropy vs momentum after decreasing from the maximum at k = 0. In massive Dirac field the effect is a slight distortion of the non-monotonic profile giving rise to the maximum of entanglement entropy at k > 0. More interestingly, massless field of both type can only get entangled through anisotropy, with a maximum of entanglement entropy occurring at k > 0. |
2208.04906 | Vyacheslav Dokuchaev | Victor A. Berezin and Vyacheslav I. Dokuchaev | Weyl geometry and cosmological particle creation | 20 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | These are lectures for students at the summer school conducted by the Faculty
of Fundamental Sciences, Bauman Moscow State Technical University at 2022.
| [
{
"created": "Tue, 9 Aug 2022 17:06:35 GMT",
"version": "v1"
}
] | 2022-08-10 | [
[
"Berezin",
"Victor A.",
""
],
[
"Dokuchaev",
"Vyacheslav I.",
""
]
] | These are lectures for students at the summer school conducted by the Faculty of Fundamental Sciences, Bauman Moscow State Technical University at 2022. |
1706.10091 | Oliver J. Tattersall | Oliver J. Tattersall, Macarena Lagos, Pedro G. Ferreira | A covariant approach to parameterised cosmological perturbations | Updated to match published version | Phys. Rev. D Volume 96 Issue 6 (2017) | 10.1103/PhysRevD.96.064011 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a covariant formulation for constructing general quadratic actions
for cosmological perturbations, invariant under a given set of gauge symmetries
for a given field content. This approach allows us to analyse scalar, vector
and tensor perturbations at the same time in a straightforward manner. We apply
the procedure to diffeomorphism invariant single-tensor, scalar-tensor and
vector-tensor theories and show explicitly the full covariant form of the
quadratic actions in such cases, in addition to the actions determining the
evolution of vector and tensor perturbations. We also discuss the role of the
symmetry of the background in identifying the set of cosmologically relevant
free parameters describing these classes of theories, including calculating the
relevant free parameters for an axisymmetric Bianchi-I vacuum universe.
| [
{
"created": "Fri, 30 Jun 2017 09:49:17 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Sep 2017 08:36:40 GMT",
"version": "v2"
}
] | 2017-09-13 | [
[
"Tattersall",
"Oliver J.",
""
],
[
"Lagos",
"Macarena",
""
],
[
"Ferreira",
"Pedro G.",
""
]
] | We present a covariant formulation for constructing general quadratic actions for cosmological perturbations, invariant under a given set of gauge symmetries for a given field content. This approach allows us to analyse scalar, vector and tensor perturbations at the same time in a straightforward manner. We apply the procedure to diffeomorphism invariant single-tensor, scalar-tensor and vector-tensor theories and show explicitly the full covariant form of the quadratic actions in such cases, in addition to the actions determining the evolution of vector and tensor perturbations. We also discuss the role of the symmetry of the background in identifying the set of cosmologically relevant free parameters describing these classes of theories, including calculating the relevant free parameters for an axisymmetric Bianchi-I vacuum universe. |
1404.0092 | Nicholas Loutrel | Nicholas Loutrel, Nicolas Yunes, Frans Pretorius | A Parametrized post-Einsteinian Framework for Gravitational Wave Bursts | 20 pages, 2 figures. Replacement of previous version. Added erratum | Phys. Rev. D 96, 089901 (2017) | 10.1103/PhysRevD.90.104010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The population of stellar-mass, compact object binaries that merge with
non-negligible eccentricity may be large enough to motivate searches with
ground-based gravitational wave detectors. Such events could be exceptional
laboratories to test General Relativity in the dynamical, strong-field regime,
as a larger fraction of the energy is emitted at high-velocities, compared to
quasi-circular inspirals. A serious obstacle here, however, is the challenge of
computing theoretical waveforms for eccentric systems with the requisite
accuracy for use in a matched-filter search. The corresponding waveforms are
more a sequence of concentrated bursts of energy emitted near periapse than a
continuous waveform. Based on this, an alternative approach, stacking excess
power over the set of time-frequency tiles coincident with the bursts, was
recently suggested as a more practical (though sub-optimal) detection strategy.
The leading-order "observable" that would be inferred from such a detection
would be a sequence of discrete numbers characterizing the position and size of
each time-frequency tile. In General Relativity, this (possibly large) sequence
of numbers is uniquely determined by the small set of parameters describing the
binary at formation. In this work, following the spirit of the parameterized
post-Einsteinian framework developed for quasi-circular inspiral, we propose a
simple, parameterized deformation of the baseline general relativistic burst
algorithm for eccentric inspiral events that would allow for model-independent
tests of Einstein's theory in this high-velocity, strong-field regime.
| [
{
"created": "Tue, 1 Apr 2014 00:59:31 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Oct 2014 17:52:19 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Oct 2017 18:30:19 GMT",
"version": "v3"
}
] | 2017-10-11 | [
[
"Loutrel",
"Nicholas",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Pretorius",
"Frans",
""
]
] | The population of stellar-mass, compact object binaries that merge with non-negligible eccentricity may be large enough to motivate searches with ground-based gravitational wave detectors. Such events could be exceptional laboratories to test General Relativity in the dynamical, strong-field regime, as a larger fraction of the energy is emitted at high-velocities, compared to quasi-circular inspirals. A serious obstacle here, however, is the challenge of computing theoretical waveforms for eccentric systems with the requisite accuracy for use in a matched-filter search. The corresponding waveforms are more a sequence of concentrated bursts of energy emitted near periapse than a continuous waveform. Based on this, an alternative approach, stacking excess power over the set of time-frequency tiles coincident with the bursts, was recently suggested as a more practical (though sub-optimal) detection strategy. The leading-order "observable" that would be inferred from such a detection would be a sequence of discrete numbers characterizing the position and size of each time-frequency tile. In General Relativity, this (possibly large) sequence of numbers is uniquely determined by the small set of parameters describing the binary at formation. In this work, following the spirit of the parameterized post-Einsteinian framework developed for quasi-circular inspiral, we propose a simple, parameterized deformation of the baseline general relativistic burst algorithm for eccentric inspiral events that would allow for model-independent tests of Einstein's theory in this high-velocity, strong-field regime. |
0907.1015 | Yuri Levin | Bruin Benthem (Lorentz Institute) and Yuri Levin (Leiden Observatory
and Lorentz Institute) | Thermo-refractive and thermo-chemical noise in the beamsplitter of
GEO600 gravitational-wave interferometer | 5 pages, submitted to Phys. Rev. D | Phys.Rev.D80:062004,2009 | 10.1103/PhysRevD.80.062004 | null | gr-qc astro-ph.IM physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Braginsky, Gorodetsky, and Vyatchanin have shown that thermo-refractive
fluctuations are an important source of noise in interferometric
gravitational-wave detectors. In particular, the thermo-refractive noise in the
GEO600 beamsplitter is expected to make a substantial contribution to the
interferometer's total noise budget. Here we present a new computation of the
GEO600 thermo-refractive noise which takes into account the beam's elliptical
profile and, more importantly, the fact that the laser beam induces a standing
electromagnetic wave in the beamsplitter. The use of updated parameters results
in the overall reduction of the calculated noise amplitude by a factor of about
5 in the low-frequency part of the GEO600 band, compared to the previous
estimates. We also find, by contrast with previous calculations, that
thermo-refractive fluctuations result in white noise between 600 Hz and 39 MHz,
at a level of $8.5\cdot 10^{-24}$Hz$^{-1/2}$. Finally, we describe a new type
of thermal noise, which we call the thermo-chemical noise. This is caused by a
random motion of optically-active chemical impurities or structural defects in
the direction along a steep intensity gradient of the standing wave. We discuss
the potential relevance of the thermo-chemical noise for GEO600.
| [
{
"created": "Mon, 6 Jul 2009 15:33:43 GMT",
"version": "v1"
}
] | 2010-02-22 | [
[
"Benthem",
"Bruin",
"",
"Lorentz Institute"
],
[
"Levin",
"Yuri",
"",
"Leiden Observatory\n and Lorentz Institute"
]
] | Braginsky, Gorodetsky, and Vyatchanin have shown that thermo-refractive fluctuations are an important source of noise in interferometric gravitational-wave detectors. In particular, the thermo-refractive noise in the GEO600 beamsplitter is expected to make a substantial contribution to the interferometer's total noise budget. Here we present a new computation of the GEO600 thermo-refractive noise which takes into account the beam's elliptical profile and, more importantly, the fact that the laser beam induces a standing electromagnetic wave in the beamsplitter. The use of updated parameters results in the overall reduction of the calculated noise amplitude by a factor of about 5 in the low-frequency part of the GEO600 band, compared to the previous estimates. We also find, by contrast with previous calculations, that thermo-refractive fluctuations result in white noise between 600 Hz and 39 MHz, at a level of $8.5\cdot 10^{-24}$Hz$^{-1/2}$. Finally, we describe a new type of thermal noise, which we call the thermo-chemical noise. This is caused by a random motion of optically-active chemical impurities or structural defects in the direction along a steep intensity gradient of the standing wave. We discuss the potential relevance of the thermo-chemical noise for GEO600. |
1512.05277 | Xiao-Kan Guo | Xiao-Kan Guo | Black hole thermodynamics from decoherence | v1:11 pages. v2:12 pages, new references are added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an approach to the four laws of black hole thermodynamics by
utilizing the thermodynamics of quantum coherence. Firstly, Hawking effect is
attributed to the decoherence of the two-mode squeezed state in a black hole
spacetime. Then use is made of the relative entropy between undecohered and
decohered squeezed states whose monotonicity gives the zeroth and the second
law, while the first law can be obtained either by the vanishing of the first
derivative of relative entropy or by studying the effective thermal model
generated by the modular Hamiltonian. Futhermore, information-theoretic
arguments give a Planck's form of the third law of black hole thermodynamics.
With this approach we can understand the laboratory analogues of black holes
solely by quantum theory, and find a way to detect the thermodynamics of black
holes produced in colliders.
| [
{
"created": "Tue, 15 Dec 2015 04:05:51 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Dec 2016 15:18:14 GMT",
"version": "v2"
}
] | 2016-12-07 | [
[
"Guo",
"Xiao-Kan",
""
]
] | We present an approach to the four laws of black hole thermodynamics by utilizing the thermodynamics of quantum coherence. Firstly, Hawking effect is attributed to the decoherence of the two-mode squeezed state in a black hole spacetime. Then use is made of the relative entropy between undecohered and decohered squeezed states whose monotonicity gives the zeroth and the second law, while the first law can be obtained either by the vanishing of the first derivative of relative entropy or by studying the effective thermal model generated by the modular Hamiltonian. Futhermore, information-theoretic arguments give a Planck's form of the third law of black hole thermodynamics. With this approach we can understand the laboratory analogues of black holes solely by quantum theory, and find a way to detect the thermodynamics of black holes produced in colliders. |
gr-qc/0002050 | Andrzej Woszczyna | Zdzislaw A. Golda, Andrzej Woszczyna | Acoustics of early universe. I. Flat versus open universe models | The new version extended by 2 sections. Changes in notation. Some
important comments added | Class.Quant.Grav. 18 (2001) 543-554 | 10.1088/0264-9381/18/3/313 | null | gr-qc astro-ph | null | A simple perturbation description unique for all signs of curvature, and
based on the gauge-invariant formalisms is proposed to demonstrate that:
(1) The density perturbations propagate in the flat radiation-dominated
universe in exactly the same way as electromagnetic or gravitational waves
propagate in the epoch of the matter domination.
(2) In the open universe, sounds are dispersed by curvature. The space
curvature defines the minimal frequency $\omega_{\rm c}$ below which the
propagation of perturbations is forbidden.
Gaussian acoustic fields are considered and the curvature imprint in the
perturbations spectrum is discussed.
| [
{
"created": "Tue, 15 Feb 2000 11:44:59 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Dec 2000 18:37:35 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Golda",
"Zdzislaw A.",
""
],
[
"Woszczyna",
"Andrzej",
""
]
] | A simple perturbation description unique for all signs of curvature, and based on the gauge-invariant formalisms is proposed to demonstrate that: (1) The density perturbations propagate in the flat radiation-dominated universe in exactly the same way as electromagnetic or gravitational waves propagate in the epoch of the matter domination. (2) In the open universe, sounds are dispersed by curvature. The space curvature defines the minimal frequency $\omega_{\rm c}$ below which the propagation of perturbations is forbidden. Gaussian acoustic fields are considered and the curvature imprint in the perturbations spectrum is discussed. |
gr-qc/0603123 | Alex Rivero E | Alejandro Rivero | Some bounds extracted from a quantum of area | 10 pages, no figures | null | null | null | gr-qc | null | Asking very elementary relativistic quantum mechanics to meet quantums of
area and time, it is possible to observe at a general level: a) the seesaw
bound for the mass of neutrinos, and b) the need of a gauge group at energies
below Planck mass.
| [
{
"created": "Thu, 30 Mar 2006 12:03:38 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rivero",
"Alejandro",
""
]
] | Asking very elementary relativistic quantum mechanics to meet quantums of area and time, it is possible to observe at a general level: a) the seesaw bound for the mass of neutrinos, and b) the need of a gauge group at energies below Planck mass. |
2010.03033 | Genly Le\'on | Genly Leon (Catolica del Norte U.), Alfredo Millano (Catolica del
Norte U.), Joey Latta (Dalhousie U., Math. Dept.) | Einstein-aether models III: conformally static metrics, perfect fluid
and scalar fields | 39 pages, 15 compound figures | Eur. Phys. J. C (2020) 80:1192 | 10.1140/epjc/s10052-020-08731-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The asymptotic properties of conformally static metrics in Einstein-aether
theory with a perfect fluid source and a scalar field are analyzed. In case of
perfect fluid, some relativistic solutions are recovered such as: Minkowski
spacetime, the Kasner solution, a flat FLRW space and static orbits depending
on the barotropic parameter $\gamma$. To analyze locally the behavior of the
solutions near a sonic line $v^2=\gamma-1$, where $v$ is the tilt, a new
"shock" variable is used. Two new equilibrium point on this line are found.
These points do not exist in General Relativity when $1 <\gamma<2 $. In the
limiting case of General Relativity these points represent stiff solutions with
extreme tilt. Lines of equilibrium points associated with a change of causality
of the homothetic vector field are found in the limit of General Relativity.
For non-homogeneous scalar field $\phi(t,x)$ with potential $V(\phi(t,x))$ the
symmetry of the conformally static metric restrict the scalar fields to be
considered to $ \phi(t,x)=\psi (x)-\lambda t, V(\phi(t,x))= e^{-2 t}
U(\psi(x))$, $U(\psi)=U_0 e^{-\frac{2 \psi}{\lambda}}$. An exhaustive analysis
(analytical or numerical) of the stability conditions is provided for some
particular cases.
| [
{
"created": "Tue, 6 Oct 2020 21:07:57 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jan 2021 23:32:22 GMT",
"version": "v2"
}
] | 2021-01-11 | [
[
"Leon",
"Genly",
"",
"Catolica del Norte U."
],
[
"Millano",
"Alfredo",
"",
"Catolica del\n Norte U."
],
[
"Latta",
"Joey",
"",
"Dalhousie U., Math. Dept."
]
] | The asymptotic properties of conformally static metrics in Einstein-aether theory with a perfect fluid source and a scalar field are analyzed. In case of perfect fluid, some relativistic solutions are recovered such as: Minkowski spacetime, the Kasner solution, a flat FLRW space and static orbits depending on the barotropic parameter $\gamma$. To analyze locally the behavior of the solutions near a sonic line $v^2=\gamma-1$, where $v$ is the tilt, a new "shock" variable is used. Two new equilibrium point on this line are found. These points do not exist in General Relativity when $1 <\gamma<2 $. In the limiting case of General Relativity these points represent stiff solutions with extreme tilt. Lines of equilibrium points associated with a change of causality of the homothetic vector field are found in the limit of General Relativity. For non-homogeneous scalar field $\phi(t,x)$ with potential $V(\phi(t,x))$ the symmetry of the conformally static metric restrict the scalar fields to be considered to $ \phi(t,x)=\psi (x)-\lambda t, V(\phi(t,x))= e^{-2 t} U(\psi(x))$, $U(\psi)=U_0 e^{-\frac{2 \psi}{\lambda}}$. An exhaustive analysis (analytical or numerical) of the stability conditions is provided for some particular cases. |
gr-qc/0409088 | Kayll Lake | Benjamin K. Tippett and Kayll Lake | Energy conditions and a bounce in FLRW cosmologies | 4 pages revtex4 | null | null | null | gr-qc astro-ph | null | Exploiting the existence of two "cosmological" constants, one associated with
the classical Lovelock theorem and one with the vacuum energy density, we
argue, in a model independent way, that in spatially closed FLRW cosmologies
with a positive definite effective cosmological constant there exists a range
in this constant that serves as a sufficient condition for the satisfaction of
the null, weak, strong and dominant energy conditions at a bounce. The
application of energy conditions is not unambiguous and we show how the bounce
can be considered classically and how, we believe more reasonably, it can be
considered a matter of quantum cosmology.
| [
{
"created": "Wed, 22 Sep 2004 22:12:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tippett",
"Benjamin K.",
""
],
[
"Lake",
"Kayll",
""
]
] | Exploiting the existence of two "cosmological" constants, one associated with the classical Lovelock theorem and one with the vacuum energy density, we argue, in a model independent way, that in spatially closed FLRW cosmologies with a positive definite effective cosmological constant there exists a range in this constant that serves as a sufficient condition for the satisfaction of the null, weak, strong and dominant energy conditions at a bounce. The application of energy conditions is not unambiguous and we show how the bounce can be considered classically and how, we believe more reasonably, it can be considered a matter of quantum cosmology. |
2303.13717 | Shinji Tsujikawa | Katsuki Aoki, Shinji Tsujikawa | Coupled vector Gauss-Bonnet theories and hairy black holes | 16 pages, 2 figures | Phys. Lett. B 843 (2023) 138022 | 10.1016/j.physletb.2023.138022 | YITP-23-38, WUCG-23-03 | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We study vector-tensor theories in which a 4-dimensional vector field
$A_{\mu}$ is coupled to a vector quantity ${\cal J}^{\mu}$, which is expressed
in terms of $A_{\mu}$ and a metric tensor $g_{\mu \nu}$. The divergence of
${\cal J}^{\mu}$ is equivalent to a Gauss-Bonnet (GB) term. We show that an
interacting Lagrangian of the form $f(X)A_{\mu}{\cal J}^{\mu}$, where $f$ is an
arbitrary function of $X=-(1/2)A_{\mu}A^{\mu}$, belongs to a scheme of beyond
generalized Proca theories. For $f(X)=\alpha={\rm constant}$, this interacting
Lagrangian reduces to a particular class of generalized Proca theories. We
apply the latter coupling to a static and spherically symmetric vacuum
configuration by incorporating the Einstein-Hilbert term, Maxwell scalar, and
vector mass term $\eta X$ ($\eta$ is a constant). Under an expansion of the
small coupling constant $\alpha$ with $\eta \neq 0$, we derive hairy black hole
solutions endowed with nonvanishing temporal and radial vector field profiles.
The asymptotic properties of solutions around the horizon and at spatial
infinity are different from those of hairy black holes present in scalar-GB
theories. We also show that black hole solutions without the vector mass term,
i.e., $\eta=0$, are prone to ghost instability of odd-parity perturbations.
| [
{
"created": "Fri, 24 Mar 2023 00:01:30 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jun 2023 00:04:56 GMT",
"version": "v2"
}
] | 2023-06-23 | [
[
"Aoki",
"Katsuki",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | We study vector-tensor theories in which a 4-dimensional vector field $A_{\mu}$ is coupled to a vector quantity ${\cal J}^{\mu}$, which is expressed in terms of $A_{\mu}$ and a metric tensor $g_{\mu \nu}$. The divergence of ${\cal J}^{\mu}$ is equivalent to a Gauss-Bonnet (GB) term. We show that an interacting Lagrangian of the form $f(X)A_{\mu}{\cal J}^{\mu}$, where $f$ is an arbitrary function of $X=-(1/2)A_{\mu}A^{\mu}$, belongs to a scheme of beyond generalized Proca theories. For $f(X)=\alpha={\rm constant}$, this interacting Lagrangian reduces to a particular class of generalized Proca theories. We apply the latter coupling to a static and spherically symmetric vacuum configuration by incorporating the Einstein-Hilbert term, Maxwell scalar, and vector mass term $\eta X$ ($\eta$ is a constant). Under an expansion of the small coupling constant $\alpha$ with $\eta \neq 0$, we derive hairy black hole solutions endowed with nonvanishing temporal and radial vector field profiles. The asymptotic properties of solutions around the horizon and at spatial infinity are different from those of hairy black holes present in scalar-GB theories. We also show that black hole solutions without the vector mass term, i.e., $\eta=0$, are prone to ghost instability of odd-parity perturbations. |
2005.08428 | Katsuki Aoki | Katsuki Aoki, Mohammad Ali Gorji, and Shinji Mukohyama | Cosmology and gravitational waves in consistent $D\to 4$
Einstein-Gauss-Bonnet gravity | 18 pages, no figures, new subsection added, accepted for publication
in JCAP, observational constraints corrected | null | null | YITP-20-72, IPMU20-0058 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a very recent paper [1], we have proposed a novel $4$-dimensional
gravitational theory with two dynamical degrees of freedom, which serves as a
consistent realization of $D\to4$ Einstein-Gauss-Bonnet gravity with the
rescaled Gauss-Bonnet coupling constant $\tilde{\alpha}$. This has been made
possible by breaking a part of diffeomorphism invariance, and thus is
consistent with the Lovelock theorem. In the present paper, we study
cosmological implications of the theory in the presence of a perfect fluid and
clarify the similarities and differences between the results obtained from the
consistent $4$-dimensional theory and those from the previously considered,
naive (and inconsistent) $D\rightarrow 4$ limit. Studying the linear
perturbations, we explicitly show that the theory only has tensorial
gravitational degrees of freedom (besides the matter degree) and that for
$\tilde{\alpha}>0$ and $\dot{H}<0$, perturbations are free of any pathologies
so that we can implement the setup to construct early and/or late time
cosmological models. Interestingly, a $k^4$ term appears in the dispersion
relation of tensor modes which plays significant roles at small scales and
makes the theory different than not only general relativity but also many other
modified gravity theories as well as the naive (and inconsistent) $D\to 4$
limit. Taking into account the $k^4$ term, the observational constraint on the
propagation of gravitational waves yields the bound $\tilde{\alpha} \lesssim
(10\,{\rm meV})^{-2}$. This is the first bound on the only parameter (besides
the Newton's constant and the choice of a constraint that stems from a temporal
gauge fixing) in the consistent theory of $D\to 4$ Einstein-Gauss-Bonnet
gravity.
| [
{
"created": "Mon, 18 May 2020 02:35:53 GMT",
"version": "v1"
},
{
"created": "Mon, 25 May 2020 08:22:38 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Aug 2020 02:50:13 GMT",
"version": "v3"
},
{
"created": "Wed, 28 Apr 2021 04:44:20 GMT",
"version": "v4"
}
] | 2021-04-29 | [
[
"Aoki",
"Katsuki",
""
],
[
"Gorji",
"Mohammad Ali",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | In a very recent paper [1], we have proposed a novel $4$-dimensional gravitational theory with two dynamical degrees of freedom, which serves as a consistent realization of $D\to4$ Einstein-Gauss-Bonnet gravity with the rescaled Gauss-Bonnet coupling constant $\tilde{\alpha}$. This has been made possible by breaking a part of diffeomorphism invariance, and thus is consistent with the Lovelock theorem. In the present paper, we study cosmological implications of the theory in the presence of a perfect fluid and clarify the similarities and differences between the results obtained from the consistent $4$-dimensional theory and those from the previously considered, naive (and inconsistent) $D\rightarrow 4$ limit. Studying the linear perturbations, we explicitly show that the theory only has tensorial gravitational degrees of freedom (besides the matter degree) and that for $\tilde{\alpha}>0$ and $\dot{H}<0$, perturbations are free of any pathologies so that we can implement the setup to construct early and/or late time cosmological models. Interestingly, a $k^4$ term appears in the dispersion relation of tensor modes which plays significant roles at small scales and makes the theory different than not only general relativity but also many other modified gravity theories as well as the naive (and inconsistent) $D\to 4$ limit. Taking into account the $k^4$ term, the observational constraint on the propagation of gravitational waves yields the bound $\tilde{\alpha} \lesssim (10\,{\rm meV})^{-2}$. This is the first bound on the only parameter (besides the Newton's constant and the choice of a constraint that stems from a temporal gauge fixing) in the consistent theory of $D\to 4$ Einstein-Gauss-Bonnet gravity. |
2011.08005 | Alesandro Santos | J. S. Gon\c{c}alves and A. F. Santos | A study on causality in $f(R,\phi,X)$ theory | 14 pages, accepted for publication in IJMPA | null | 10.1142/S0217751X21500093 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The $k$-essence modified $f(R)$ gravity model, i.e., $f(R,\phi,X)$ theory is
studied. The question of violation of causality, in the framework of
G\"{o}del-type universes, is investigated in this gravitational model. Causal
and non-causal solutions are allowed. A critical radius for non-causal solution
is calculated. It is shown that the violation of causality depends on the
content of matter.
| [
{
"created": "Mon, 16 Nov 2020 14:51:08 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Gonçalves",
"J. S.",
""
],
[
"Santos",
"A. F.",
""
]
] | The $k$-essence modified $f(R)$ gravity model, i.e., $f(R,\phi,X)$ theory is studied. The question of violation of causality, in the framework of G\"{o}del-type universes, is investigated in this gravitational model. Causal and non-causal solutions are allowed. A critical radius for non-causal solution is calculated. It is shown that the violation of causality depends on the content of matter. |
1109.1694 | C. Q. Geng | Kazuharu Bamba and Chao-Qiang Geng | Thermodynamics of cosmological horizons in $f(T)$ gravity | 18 pages, no figure, version accepted for publication in JCAP | null | 10.1088/1475-7516/2011/11/008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore thermodynamics of the apparent horizon in $f(T)$ gravity with both
equilibrium and non-equilibrium descriptions. We find the same dual
equilibrium/non-equilibrium formulation for $f(T)$ as for $f(R)$ gravity. In
particular, we show that the second law of thermodynamics can be satisfied for
the universe with the same temperature of the outside and inside the apparent
horizon.
| [
{
"created": "Thu, 8 Sep 2011 11:52:45 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Oct 2011 10:39:21 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Geng",
"Chao-Qiang",
""
]
] | We explore thermodynamics of the apparent horizon in $f(T)$ gravity with both equilibrium and non-equilibrium descriptions. We find the same dual equilibrium/non-equilibrium formulation for $f(T)$ as for $f(R)$ gravity. In particular, we show that the second law of thermodynamics can be satisfied for the universe with the same temperature of the outside and inside the apparent horizon. |
1508.03343 | Ivica Smoli\'c | Maro Cvitan, Predrag Dominis Prester, Ivica Smoli\'c | Does three dimensional electromagnetic field inherit the spacetime
symmetries? | 10 pages; published version (some comments and references added) | Class. Quantum Grav. 33 (2016) 077001 | 10.1088/0264-9381/33/7/077001 | ZTF-EP-15-04 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that the electromagnetic field in a (1+2)-dimensional spacetime
necessarily inherits the symmetries of the spacetime metric in a large class of
generalized Einstein-Maxwell theories. The Lagrangians of the studied theories
have general diff-covariant gravitational part and include both the
gravitational and the gauge Chern-Simons terms.
| [
{
"created": "Thu, 13 Aug 2015 20:10:26 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2016 21:22:10 GMT",
"version": "v2"
}
] | 2016-03-30 | [
[
"Cvitan",
"Maro",
""
],
[
"Prester",
"Predrag Dominis",
""
],
[
"Smolić",
"Ivica",
""
]
] | We prove that the electromagnetic field in a (1+2)-dimensional spacetime necessarily inherits the symmetries of the spacetime metric in a large class of generalized Einstein-Maxwell theories. The Lagrangians of the studied theories have general diff-covariant gravitational part and include both the gravitational and the gauge Chern-Simons terms. |
2003.03366 | Adrien Kuntz | Adrien Kuntz | Half-solution to the two-body problem in General Relativity | 16 pages, 6 figures. More detailed version accepted in PRD | Phys. Rev. D 102, 064019 (2020) | 10.1103/PhysRevD.102.064019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the introduction of two worldline parameters defines a different
approach to computations in the effective field theory approach to the two-body
problem in General Relativity and present some preliminary evidence for a
reduction in computational complexity. These parameters obey a polynomial
equation whose perturbative expansion recovers an infinite series of diagrams.
Futhermore, we show that our equations define an effective two-body horizon for
interacting particles in General Relativity; in the circular orbit case, it
corresponds to the smallest conceivable separation up to which the orbit can
remain circular. We expect our results to simplify higher-order computations in
the two-body problem, as well as to give insights on the nonperturbative
properties of interacting binaries.
| [
{
"created": "Fri, 6 Mar 2020 18:55:34 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2020 13:48:11 GMT",
"version": "v2"
}
] | 2020-09-16 | [
[
"Kuntz",
"Adrien",
""
]
] | We show that the introduction of two worldline parameters defines a different approach to computations in the effective field theory approach to the two-body problem in General Relativity and present some preliminary evidence for a reduction in computational complexity. These parameters obey a polynomial equation whose perturbative expansion recovers an infinite series of diagrams. Futhermore, we show that our equations define an effective two-body horizon for interacting particles in General Relativity; in the circular orbit case, it corresponds to the smallest conceivable separation up to which the orbit can remain circular. We expect our results to simplify higher-order computations in the two-body problem, as well as to give insights on the nonperturbative properties of interacting binaries. |
1501.02837 | Mahdi Godazgar | Gabriel Bernardi de Freitas, Mahdi Godazgar, Harvey S. Reall | Uniqueness of the Kerr-de Sitter spacetime as an algebraically special
solution in five dimensions | 30 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the most general solution of the five-dimensional vacuum
Einstein equation, allowing for a cosmological constant, with (i) a Weyl tensor
that is type II or more special in the classification of Coley et al., (ii) a
non-degenerate "optical matrix" encoding the expansion, rotation and shear of
the aligned null direction. The solution is specified by three parameters. It
is locally isometric to the 5d Kerr-de Sitter solution, or related to this
solution by analytic continuation or taking a limit. This is in contrast with
four dimensions, where there exist infinitely many solutions with properties
(i) and (ii).
| [
{
"created": "Mon, 12 Jan 2015 21:56:44 GMT",
"version": "v1"
}
] | 2015-01-14 | [
[
"de Freitas",
"Gabriel Bernardi",
""
],
[
"Godazgar",
"Mahdi",
""
],
[
"Reall",
"Harvey S.",
""
]
] | We determine the most general solution of the five-dimensional vacuum Einstein equation, allowing for a cosmological constant, with (i) a Weyl tensor that is type II or more special in the classification of Coley et al., (ii) a non-degenerate "optical matrix" encoding the expansion, rotation and shear of the aligned null direction. The solution is specified by three parameters. It is locally isometric to the 5d Kerr-de Sitter solution, or related to this solution by analytic continuation or taking a limit. This is in contrast with four dimensions, where there exist infinitely many solutions with properties (i) and (ii). |
gr-qc/9506073 | null | Hugo A. Morales-Tecotl and Giampiero Esposito | Self-Dual Action for Fermionic Fields and Gravitation | 13 pages, plain-tex, recently appearing in Nuovo Cimento B, volume
109, pages 973-982, September 1994 | NuovoCim.B109:973-982,1994 | 10.1007/BF02726144 | DSF 94/23 | gr-qc | null | This paper studies the self-dual Einstein-Dirac theory. A generalization is
obtained of the Jacobson-Smolin proof of the equivalence between the self-dual
and Palatini purely gravitational actions. Hence one proves equivalence of
self-dual Einstein-Dirac theory to the Einstein-Cartan-Sciama-Kibble-Dirac
theory. The Bianchi symmetry of the curvature, core of the proof, now contains
a non-vanishing torsion. Thus, in the self-dual framework, the extra terms
entering the equations of motion with respect to the standard Einstein-Dirac
field equations, are neatly associated with torsion.
| [
{
"created": "Thu, 29 Jun 1995 09:39:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Morales-Tecotl",
"Hugo A.",
""
],
[
"Esposito",
"Giampiero",
""
]
] | This paper studies the self-dual Einstein-Dirac theory. A generalization is obtained of the Jacobson-Smolin proof of the equivalence between the self-dual and Palatini purely gravitational actions. Hence one proves equivalence of self-dual Einstein-Dirac theory to the Einstein-Cartan-Sciama-Kibble-Dirac theory. The Bianchi symmetry of the curvature, core of the proof, now contains a non-vanishing torsion. Thus, in the self-dual framework, the extra terms entering the equations of motion with respect to the standard Einstein-Dirac field equations, are neatly associated with torsion. |
1312.0784 | Francisco Lobo | Salvatore Capozziello, Francisco S. N. Lobo, Jos\'e P. Mimoso | Energy conditions in modified gravity | 4 pages. V2: 5 pages; version to appear in Physics Letters B. V3:
typo in Eq. (4) corrected | Phys.Lett.B730:280-283,2014 | 10.1016/j.physletb.2014.01.066 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider generalized energy conditions in modified theories of gravity by
taking into account the further degrees of freedom related to scalar fields and
curvature invariants. The latter are usually recast as generalized {\it
geometrical fluids} that have different meanings with respect to the standard
matter fluids generally adopted as sources of the field equations. More
specifically, in modified gravity the curvature terms are grouped in a tensor
$H^{ab}$ and a coupling $g(\Psi^i)$ that can be reorganized in effective
Einstein field equations, as corrections to the energy-momentum tensor of
matter. The formal validity of such inequalities does not assure some basic
requirements such as the attractive nature of gravity, so that the energy
conditions have to be considered in a wider sense.
| [
{
"created": "Tue, 3 Dec 2013 11:52:41 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jan 2014 10:41:44 GMT",
"version": "v2"
},
{
"created": "Thu, 13 Feb 2014 15:02:00 GMT",
"version": "v3"
}
] | 2014-02-14 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Mimoso",
"José P.",
""
]
] | We consider generalized energy conditions in modified theories of gravity by taking into account the further degrees of freedom related to scalar fields and curvature invariants. The latter are usually recast as generalized {\it geometrical fluids} that have different meanings with respect to the standard matter fluids generally adopted as sources of the field equations. More specifically, in modified gravity the curvature terms are grouped in a tensor $H^{ab}$ and a coupling $g(\Psi^i)$ that can be reorganized in effective Einstein field equations, as corrections to the energy-momentum tensor of matter. The formal validity of such inequalities does not assure some basic requirements such as the attractive nature of gravity, so that the energy conditions have to be considered in a wider sense. |
2111.11596 | Changjun Gao | Changjun Gao | New understanding of Majumdar-Papapetrou and Perj\'es-Israel-Wilson
solutions | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hartle and Hawking have shown that, except for the case of only point
monopoles as sources, both the Majumdar-Papapetrou and the
Perj\'es-Israel-Wilson solutions have naked singularities if the space is
asymptotically flat. In this article, by using the method of introducing
interior solutions, these naked singularities are erased.
| [
{
"created": "Tue, 23 Nov 2021 00:59:42 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Nov 2021 06:27:12 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Jan 2022 09:25:57 GMT",
"version": "v3"
},
{
"created": "Tue, 8 Feb 2022 22:51:19 GMT",
"version": "v4"
},
{
"created": "Tue, 12 Apr 2022 01:15:03 GMT",
"version": "v5"
},
{
"created": "Fri, 15 Apr 2022 00:37:43 GMT",
"version": "v6"
}
] | 2022-04-18 | [
[
"Gao",
"Changjun",
""
]
] | Hartle and Hawking have shown that, except for the case of only point monopoles as sources, both the Majumdar-Papapetrou and the Perj\'es-Israel-Wilson solutions have naked singularities if the space is asymptotically flat. In this article, by using the method of introducing interior solutions, these naked singularities are erased. |
1603.01655 | Ahmad Borzou | Ahmad Borzou | A Macroscopically Effective Lorentz Gauge Theory of Gravity | 17 pages, 2 figures, accepted for publication in CQG | Classical and Quantum Gravity, 33 (2016) 235006 | 10.1088/0264-9381/33/23/235006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following the ideas of effective field theories, we derive classically
effective field equations of recently developed Lorentz gauge theory of
gravity. It is shown that Newton's gravitational constant emerges as an
effective coupling parameter if an extremely small length is integrated out of
the underlying theory. The linear version of the effective theory is shown to
be fully consistent with the Newtonian gravity. We also derive a numerical
solution for the interior of a star and show that in the non-linear regions,
the behavior of the effective theory deviates from the predictions of general
relativity.
| [
{
"created": "Fri, 4 Mar 2016 23:25:09 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Oct 2016 11:22:28 GMT",
"version": "v2"
}
] | 2016-11-01 | [
[
"Borzou",
"Ahmad",
""
]
] | Following the ideas of effective field theories, we derive classically effective field equations of recently developed Lorentz gauge theory of gravity. It is shown that Newton's gravitational constant emerges as an effective coupling parameter if an extremely small length is integrated out of the underlying theory. The linear version of the effective theory is shown to be fully consistent with the Newtonian gravity. We also derive a numerical solution for the interior of a star and show that in the non-linear regions, the behavior of the effective theory deviates from the predictions of general relativity. |
gr-qc/0404099 | Brendan Foster | Edward Anderson, Julian Barbour, Brendan Z. Foster, Bryan Kelleher,
and Niall O'Murchadha | A first-principles derivation of York scaling and the Lichnerowicz-York
equation | 4 pages | null | null | null | gr-qc | null | The only efficient and robust method of generating consistent initial data in
general relativity is the conformal technique initiated by Lichnerowicz and
perfected by York. In the spatially compact case, the complete scheme consists
of the Arnowitt-Deser-Misner (ADM) Hamiltonian and momentum constraints, the
ADM Euler-Lagrange equations, York's constant-mean-curvature (CMC) condition,
and a lapse-fixing equation (LFE) that ensures propagation of the CMC condition
by the Euler-Lagrange equations. The Hamiltonian constraint is rewritten as the
Lichnerowicz-York equation for the conformal factor (psi) of the physical
metric (psi)^4(g_{ij}) given an initial unphysical 3-metric (g_{ij}). The CMC
condition and LFE introduce a distinguished foliation (definition of
simultaneity) on spacetime, and separate scaling laws for the canonical momenta
and their trace are used. In this article, we derive all these features in a
single package by seeking a gauge theory of geometrodynamics (evolving
3-geometries) invariant under both three-dimensional diffeomorphisms and
volume-preserving conformal transformations.
| [
{
"created": "Thu, 22 Apr 2004 15:53:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Anderson",
"Edward",
""
],
[
"Barbour",
"Julian",
""
],
[
"Foster",
"Brendan Z.",
""
],
[
"Kelleher",
"Bryan",
""
],
[
"O'Murchadha",
"Niall",
""
]
] | The only efficient and robust method of generating consistent initial data in general relativity is the conformal technique initiated by Lichnerowicz and perfected by York. In the spatially compact case, the complete scheme consists of the Arnowitt-Deser-Misner (ADM) Hamiltonian and momentum constraints, the ADM Euler-Lagrange equations, York's constant-mean-curvature (CMC) condition, and a lapse-fixing equation (LFE) that ensures propagation of the CMC condition by the Euler-Lagrange equations. The Hamiltonian constraint is rewritten as the Lichnerowicz-York equation for the conformal factor (psi) of the physical metric (psi)^4(g_{ij}) given an initial unphysical 3-metric (g_{ij}). The CMC condition and LFE introduce a distinguished foliation (definition of simultaneity) on spacetime, and separate scaling laws for the canonical momenta and their trace are used. In this article, we derive all these features in a single package by seeking a gauge theory of geometrodynamics (evolving 3-geometries) invariant under both three-dimensional diffeomorphisms and volume-preserving conformal transformations. |
gr-qc/0301077 | Jose Geraldo Pereira | R. Aldrovandi, P. B. Barros, J. G. Pereira | Gravitation as Anholonomy | RevTeX4, 10 pages, no figures. To appear in Gen. Rel. Grav | Gen.Rel.Grav. 35 (2003) 991-1005 | 10.1023/A:1024060732690 | null | gr-qc | null | A gravitational field can be seen as the anholonomy of the tetrad fields.
This is more explicit in the teleparallel approach, in which the gravitational
field-strength is the torsion of the ensuing Weitzenboeck connection. In a
tetrad frame, that torsion is just the anholonomy of that frame. The infinitely
many tetrad fields taking the Lorentz metric into a given Riemannian metric
differ by point-dependent Lorentz transformations. Inertial frames constitute a
smaller infinity of them, differing by fixed-point Lorentz transformations.
Holonomic tetrads take the Lorentz metric into itself, and correspond to
Minkowski flat spacetime. An accelerated frame is necessarily anholonomic and
sees the electromagnetic field strength with an additional term.
| [
{
"created": "Tue, 21 Jan 2003 13:11:23 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Aldrovandi",
"R.",
""
],
[
"Barros",
"P. B.",
""
],
[
"Pereira",
"J. G.",
""
]
] | A gravitational field can be seen as the anholonomy of the tetrad fields. This is more explicit in the teleparallel approach, in which the gravitational field-strength is the torsion of the ensuing Weitzenboeck connection. In a tetrad frame, that torsion is just the anholonomy of that frame. The infinitely many tetrad fields taking the Lorentz metric into a given Riemannian metric differ by point-dependent Lorentz transformations. Inertial frames constitute a smaller infinity of them, differing by fixed-point Lorentz transformations. Holonomic tetrads take the Lorentz metric into itself, and correspond to Minkowski flat spacetime. An accelerated frame is necessarily anholonomic and sees the electromagnetic field strength with an additional term. |
2312.15991 | Andrzej Okolow | Andrzej Okolow | Constraints of the Teleparallel Equivalent of General Relativity in a
gauge | 32 pages, no figure, LaTeX, the paper substantially rewritten | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a specific Hamiltonian formulation of the Teleparallel Equivalent
of General Relativity, where the canonical variables are expressed by means of
differential forms. We show that some ``position'' variables of this
formulation can be always gauge-transformed to zero. In this gauge the
constraints of the theory become simpler, and the other ``position'' variables
acquire a nice geometric interpretation that allows for an alternative, clearer
form of the constraints. Based on these results we derive some exact solutions
to the constraints.
| [
{
"created": "Tue, 26 Dec 2023 10:45:29 GMT",
"version": "v1"
},
{
"created": "Wed, 22 May 2024 14:49:02 GMT",
"version": "v2"
}
] | 2024-05-24 | [
[
"Okolow",
"Andrzej",
""
]
] | We consider a specific Hamiltonian formulation of the Teleparallel Equivalent of General Relativity, where the canonical variables are expressed by means of differential forms. We show that some ``position'' variables of this formulation can be always gauge-transformed to zero. In this gauge the constraints of the theory become simpler, and the other ``position'' variables acquire a nice geometric interpretation that allows for an alternative, clearer form of the constraints. Based on these results we derive some exact solutions to the constraints. |
gr-qc/0405028 | Aleks Kleyn | Aleks Kleyn | Metric-Affine Manifold | English text - 20 pages; Russian text - 21 pages; 1 figure. (revised
v3): Added Lie derivative of the connection | null | null | null | gr-qc math.DG | null | We call a manifold with torsion and nonmetricity the metric-affine manifold.
The nonmetricity leads to a difference between the auto parallel line and the
extreme line, and to a change in the expression of the Frenet transport and
moving basis. The torsion leads to a change in the Killing equation. We also
need to add a similar equation for the connection.
The analysis of the Frenet transport leads to the concept of the Cartan
transport and an introduction of the connection compatible with the metric
tensor. The dynamics of a particle follows to the Cartan transport. We need
additional physical constraints to make a nonmetricity observable.
| [
{
"created": "Thu, 6 May 2004 03:48:56 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Jun 2004 04:07:50 GMT",
"version": "v2"
},
{
"created": "Sat, 24 Jul 2004 04:07:44 GMT",
"version": "v3"
},
{
"created": "Mon, 20 Dec 2004 00:05:16 GMT",
"version": "v4"
},
{
"created": "Fri, 29 Feb 2008 05:02:56 GMT",
"version": "v5"
}
] | 2008-02-29 | [
[
"Kleyn",
"Aleks",
""
]
] | We call a manifold with torsion and nonmetricity the metric-affine manifold. The nonmetricity leads to a difference between the auto parallel line and the extreme line, and to a change in the expression of the Frenet transport and moving basis. The torsion leads to a change in the Killing equation. We also need to add a similar equation for the connection. The analysis of the Frenet transport leads to the concept of the Cartan transport and an introduction of the connection compatible with the metric tensor. The dynamics of a particle follows to the Cartan transport. We need additional physical constraints to make a nonmetricity observable. |
gr-qc/0510119 | Jeanette E. Nelson | L. Chekhov (Steklov Mathematical Institute and Institute for
Experimental and Theoretical Physics, Moscow, Russia), J.E.Nelson
(Universita` and INFN, Torino, Italy) and T. Regge (Politecnico di Torino,
Torino, Italy) | Extension of geodesic algebras to continuous genus | 16 pages, submitted to Lett.Math.Phys | Lett.Math.Phys. 78 (2006) 17-26 | 10.1007/s11005-006-0112-4 | null | gr-qc hep-th math-ph math.MP | null | Using the Penner--Fock parameterization for Teichmuller spaces of Riemann
surfaces with holes, we construct the string-like free-field representation of
the Poisson and quantum algebras of geodesic functions in the continuous-genus
limit. The mapping class group acts naturally in the obtained representation.
| [
{
"created": "Fri, 28 Oct 2005 16:51:43 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Chekhov",
"L.",
"",
"Steklov Mathematical Institute and Institute for\n Experimental and Theoretical Physics, Moscow, Russia"
],
[
"Nelson",
"J. E.",
"",
"Universita` and INFN, Torino, Italy"
],
[
"Regge",
"T.",
"",
"Politecnico di Torino,\n Torino, Italy"
]
] | Using the Penner--Fock parameterization for Teichmuller spaces of Riemann surfaces with holes, we construct the string-like free-field representation of the Poisson and quantum algebras of geodesic functions in the continuous-genus limit. The mapping class group acts naturally in the obtained representation. |
2206.11097 | George Macaulay Mr | George Macaulay | Linear Newman-Penrose charges as subleading BMS and dual BMS charges | 26 pages | null | 10.1088/1402-4896/aca0cf | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we further develop previous work on asymptotically flat
spacetimes and extend subleading BMS and dual BMS charges in a large $r$
expansion to all orders in $r^{-1}$. This forms a complete account of this
prescription in relation to the previously discovered Newman-Penrose charges.
We provide an explanation for the origin of the infinite tower of linear
Newman-Penrose charges with regards to asymptotic symmetries and justify why
these charges fail to be conserved at the non-linear level as well as failing
to exhibit full supertranslation invariance even at the linear level.
| [
{
"created": "Wed, 22 Jun 2022 13:55:31 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jun 2022 15:08:44 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Nov 2022 11:02:02 GMT",
"version": "v3"
},
{
"created": "Tue, 25 Apr 2023 11:27:12 GMT",
"version": "v4"
}
] | 2023-04-26 | [
[
"Macaulay",
"George",
""
]
] | In this paper, we further develop previous work on asymptotically flat spacetimes and extend subleading BMS and dual BMS charges in a large $r$ expansion to all orders in $r^{-1}$. This forms a complete account of this prescription in relation to the previously discovered Newman-Penrose charges. We provide an explanation for the origin of the infinite tower of linear Newman-Penrose charges with regards to asymptotic symmetries and justify why these charges fail to be conserved at the non-linear level as well as failing to exhibit full supertranslation invariance even at the linear level. |
gr-qc/0205075 | Vishwakarma R. G. | R. G. Vishwakarma | A Machian Model of Dark Energy | Received an Honorable mention in the Essay Contest-2002 sponsored by
the Gravity Research Foundation; A paragraph added on how the model can
explain the CMB anisotropy observations; To appear in the Classical and
Quantum Gravity | Class.Quant.Grav.19:4747-4752,2002 | 10.1088/0264-9381/19/18/309 | null | gr-qc astro-ph | null | Einstein believed that Mach's principle should play a major role in finding a
meaningful spacetime geometry, though it was discovered later that his field
equations gave some solutions which were not Machian. It is shown, in this
essay, that the kinematical $\Lambda$ models, which are invoked to solve the
cosmological constant problem, are in fact consistent with Mach's ideas. One
particular model in this category is described which results from the
microstructure of spacetime and seems to explain the current observations
successfully and also has some benefits over the conventional models. This
forces one to think whether the Mach's ideas and the cosmological constant are
interrelated in some way.
| [
{
"created": "Fri, 17 May 2002 08:10:39 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Aug 2002 15:08:21 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Vishwakarma",
"R. G.",
""
]
] | Einstein believed that Mach's principle should play a major role in finding a meaningful spacetime geometry, though it was discovered later that his field equations gave some solutions which were not Machian. It is shown, in this essay, that the kinematical $\Lambda$ models, which are invoked to solve the cosmological constant problem, are in fact consistent with Mach's ideas. One particular model in this category is described which results from the microstructure of spacetime and seems to explain the current observations successfully and also has some benefits over the conventional models. This forces one to think whether the Mach's ideas and the cosmological constant are interrelated in some way. |
1807.08270 | Xiang-Hua Zhai | Xin-zhou Li, Xiang-hua Zhai, Ping Li | Generalized Birkhoff theorem and its applications in mimetic gravity | 11 pages | null | null | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is undetermined potential function $V(\phi)$ in the action of mimetic
gravity which should be resolved through physical means. In general
relativity(GR), the static spherically symmetric(SSS) solution to the Einstein
equation is a benchmark and its deformation also plays a crucial role in
mimetic gravity. The equation of motion is provided with high nonlinearity, but
we can reduce primal nonlinearity to a frequent Riccati form in the SSS case of
mimetic gravity. In other words, we obtain an expression of solution to the
functional differential equation of motion with any potential function.
Remarkably, we proved rigorously that there is a zero point of first order for
the metric function $\beta(r)$ if another metric function $\alpha(r)$ possesses
a pole of first order within mimetic gravity. The zero point theorem may be
regarded as the generalization of Birkhoff theorem $\alpha\beta=1$ in GR. As a
corollary, we show that there is a modified black hole solution for any given
$V(\phi)$, which can pass the test of solar system. As another corollary, the
zero point theorem provides a dynamical mechanism for the maximum size of
galaxies. Especially, there are two analytic solutions which provide good fits
to the rotation curves of galaxies without the demand for particle dark matter.
| [
{
"created": "Sun, 22 Jul 2018 10:55:40 GMT",
"version": "v1"
}
] | 2018-07-24 | [
[
"Li",
"Xin-zhou",
""
],
[
"Zhai",
"Xiang-hua",
""
],
[
"Li",
"Ping",
""
]
] | There is undetermined potential function $V(\phi)$ in the action of mimetic gravity which should be resolved through physical means. In general relativity(GR), the static spherically symmetric(SSS) solution to the Einstein equation is a benchmark and its deformation also plays a crucial role in mimetic gravity. The equation of motion is provided with high nonlinearity, but we can reduce primal nonlinearity to a frequent Riccati form in the SSS case of mimetic gravity. In other words, we obtain an expression of solution to the functional differential equation of motion with any potential function. Remarkably, we proved rigorously that there is a zero point of first order for the metric function $\beta(r)$ if another metric function $\alpha(r)$ possesses a pole of first order within mimetic gravity. The zero point theorem may be regarded as the generalization of Birkhoff theorem $\alpha\beta=1$ in GR. As a corollary, we show that there is a modified black hole solution for any given $V(\phi)$, which can pass the test of solar system. As another corollary, the zero point theorem provides a dynamical mechanism for the maximum size of galaxies. Especially, there are two analytic solutions which provide good fits to the rotation curves of galaxies without the demand for particle dark matter. |
2402.18791 | Krishnakanta Bhattacharya | Krishnakanta Bhattacharya, Kazuharu Bamba, and Douglas Singleton | Topological interpretation of extremal and Davies-type phase transitions
of black holes | 19 pages, Two figures, To appear in PLB | Phys. Lett. B 854 (2024) 138722 | 10.1016/j.physletb.2024.138722 | Local Report number: FU-PCG-132 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Topological arguments are currently being used as a novel scheme to discern
the properties of black holes while ignoring their detailed structure and
specific field equations. Among various avenues of black hole physics, where
this novel approach is being utilized, the phase transition in black hole
thermodynamics lies at the forefront. There are several types of phase
transition in black holes; such as the van der Waals type phase transition,
Davies-type phase transition, extremal phase transition, and Hawking-Page (HP)
transition. So far, the topological interpretation, where the critical point
has been identified with the non-zero topological charge, has been obtained
only for the van der Waals type phase transition and HP transition in different
spacetimes. To complete the picture, here we provide the same interpretation
for two other phase transitions: Davies-type phase transition and extremal
phase transition. The entire analysis is general and is valid for any spacetime
where these types of phase transitions are observed. More importantly, our
analysis suggests that amid the apparent differences in these phase
transitions, they share the same topological characteristics, \textit{i.e.}
non-zero topological charge arising from different thermodynamic potentials in
different types of phase transition.
| [
{
"created": "Thu, 29 Feb 2024 01:39:32 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2024 07:48:46 GMT",
"version": "v2"
}
] | 2024-05-22 | [
[
"Bhattacharya",
"Krishnakanta",
""
],
[
"Bamba",
"Kazuharu",
""
],
[
"Singleton",
"Douglas",
""
]
] | Topological arguments are currently being used as a novel scheme to discern the properties of black holes while ignoring their detailed structure and specific field equations. Among various avenues of black hole physics, where this novel approach is being utilized, the phase transition in black hole thermodynamics lies at the forefront. There are several types of phase transition in black holes; such as the van der Waals type phase transition, Davies-type phase transition, extremal phase transition, and Hawking-Page (HP) transition. So far, the topological interpretation, where the critical point has been identified with the non-zero topological charge, has been obtained only for the van der Waals type phase transition and HP transition in different spacetimes. To complete the picture, here we provide the same interpretation for two other phase transitions: Davies-type phase transition and extremal phase transition. The entire analysis is general and is valid for any spacetime where these types of phase transitions are observed. More importantly, our analysis suggests that amid the apparent differences in these phase transitions, they share the same topological characteristics, \textit{i.e.} non-zero topological charge arising from different thermodynamic potentials in different types of phase transition. |
1504.05914 | Jesse Cresswell | Jesse C. Cresswell and Dan N. Vollick | Lorenz gauge quantization in conformally flat spacetimes | 8 pages | Phys. Rev. D 91, 084008 (2015) | 10.1103/PhysRevD.91.084008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it was shown that Dirac's method of quantizing constrained dynamical
systems can be used to impose the Lorenz gauge condition in a four-dimensional
cosmological spacetime. In this paper we use Dirac's method to impose the
Lorenz gauge condition in a general four-dimensional conformally flat spacetime
and find that there is no particle production. We show that in cosmological
spacetimes with dimension $D\neq 4$ there will be particle production when the
scale factor changes, and we calculate the particle production due to a sudden
change.
| [
{
"created": "Wed, 22 Apr 2015 18:32:13 GMT",
"version": "v1"
}
] | 2015-04-23 | [
[
"Cresswell",
"Jesse C.",
""
],
[
"Vollick",
"Dan N.",
""
]
] | Recently it was shown that Dirac's method of quantizing constrained dynamical systems can be used to impose the Lorenz gauge condition in a four-dimensional cosmological spacetime. In this paper we use Dirac's method to impose the Lorenz gauge condition in a general four-dimensional conformally flat spacetime and find that there is no particle production. We show that in cosmological spacetimes with dimension $D\neq 4$ there will be particle production when the scale factor changes, and we calculate the particle production due to a sudden change. |
1507.07722 | Orfeu Bertolami | O. Bertolami and P. Leal | Aspects of Phase-Space Noncommutative Quantum Mechanics | 16 pages, no figures | null | 10.1016/j.physletb.2015.08.024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work some issues in the context of Noncommutative Quantum Mechanics
(NCQM) are addressed. The main focus is on finding whether symmetries present
in Quantum Mechanics still hold in the phase-space noncommutative version. In
particular, the issues related with gauge invariance of the electromagnetic
field and the weak equivalence principle (WEP) in the context of the
gravitational quantum well (GQW) are considered. The question of the Lorentz
symmetry and the associated dispersion relation is also examined. Constraints
are set on the relevant noncommutative parameters so that gauge invariance and
Lorentz invariance holds. In opposition, the WEP is verified to hold in the
noncommutative set up, and it is only possible to observe a violation through
an anisotropy of the noncommutative parameters.
| [
{
"created": "Tue, 28 Jul 2015 10:59:06 GMT",
"version": "v1"
}
] | 2015-09-30 | [
[
"Bertolami",
"O.",
""
],
[
"Leal",
"P.",
""
]
] | In this work some issues in the context of Noncommutative Quantum Mechanics (NCQM) are addressed. The main focus is on finding whether symmetries present in Quantum Mechanics still hold in the phase-space noncommutative version. In particular, the issues related with gauge invariance of the electromagnetic field and the weak equivalence principle (WEP) in the context of the gravitational quantum well (GQW) are considered. The question of the Lorentz symmetry and the associated dispersion relation is also examined. Constraints are set on the relevant noncommutative parameters so that gauge invariance and Lorentz invariance holds. In opposition, the WEP is verified to hold in the noncommutative set up, and it is only possible to observe a violation through an anisotropy of the noncommutative parameters. |
gr-qc/0505043 | Jorge Pullin | Rodolfo Gambini, Marcelo Ponce, Jorge Pullin | Consistent discretizations: the Gowdy spacetimes | 10 pages, 8 figures | Phys.Rev. D72 (2005) 024031 | 10.1103/PhysRevD.72.024031 | LSU-REL-051005 | gr-qc | null | We apply the consistent discretization scheme to general relativity
particularized to the Gowdy space-times. This is the first time the framework
has been applied in detail in a non-linear generally-covariant gravitational
situation with local degrees of freedom. We show that the scheme can be
correctly used to numerically evolve the space-times. We show that the
resulting numerical schemes are convergent and preserve approximately the
constraints as expected.
| [
{
"created": "Tue, 10 May 2005 17:04:38 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Ponce",
"Marcelo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We apply the consistent discretization scheme to general relativity particularized to the Gowdy space-times. This is the first time the framework has been applied in detail in a non-linear generally-covariant gravitational situation with local degrees of freedom. We show that the scheme can be correctly used to numerically evolve the space-times. We show that the resulting numerical schemes are convergent and preserve approximately the constraints as expected. |
2108.12414 | Jorge Gigante Valcarcel | Sebastian Bahamonde, Jorge Gigante Valcarcel | Rotating Kerr-Newman space-times in Metric-Affine Gravity | 13 pages, 0 figures, minor changes, references added. It matches the
version published in JCAP | null | 10.1088/1475-7516/2022/01/011 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new rotating vacuum configurations endowed with both dynamical
torsion and nonmetricity fields in the framework of Metric-Affine gauge theory
of gravity. For this task, we consider scalar-flat Weyl-Cartan geometries and
obtain an axisymmetric Kerr-Newman solution in the decoupling limit between the
orbital and the spin angular momentum. The corresponding Kerr-Newman-de Sitter
solution is also compatible with a cosmological constant and additional
electromagnetic fields.
| [
{
"created": "Fri, 27 Aug 2021 17:46:38 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jan 2022 04:01:45 GMT",
"version": "v2"
}
] | 2022-01-12 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Valcarcel",
"Jorge Gigante",
""
]
] | We present new rotating vacuum configurations endowed with both dynamical torsion and nonmetricity fields in the framework of Metric-Affine gauge theory of gravity. For this task, we consider scalar-flat Weyl-Cartan geometries and obtain an axisymmetric Kerr-Newman solution in the decoupling limit between the orbital and the spin angular momentum. The corresponding Kerr-Newman-de Sitter solution is also compatible with a cosmological constant and additional electromagnetic fields. |
1109.5618 | Mercedes Martin-Benito | Mercedes Mart\'in-Benito | Cosmolog\'ia Cu\'antica de Lazos: Anisotrop\'ias e Inhomogeneidades | PhD. Thesis 2010, in Spanish (summary and conclusions in English),
225 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop Quantum Cosmology adapts the techniques of Loop Quantum Gravity in the
quantization of homogeneous cosmological models obtained from General
Relativity by symmetry reduction. As a necessary step towards the extraction of
realistic results from Loop Quantum Cosmology, we should consider the inclusion
of inhomogeneities, which play a central role in current cosmology. The main
goal of this thesis is to progress in this direction. With this aim we have
studied a natural test bed to incorporate inhomogeneities in Loop Quantum
Cosmology: the linearly polarized Gowdy T3 model. This model can be regarded as
a homogeneous Bianchi I background filled with inhomogeneities propagating in
one direction. We have completed its quantization by means of a hybrid
approach, that combines the loop quantization of the homogeneous sector, within
the so-called improved dynamics scheme, with a Fock quantization for the
inhomogeneities. In order to perform this quantization as thorough as possible,
we have also reviewed the (improved dynamics) loop quantization of flat FRW
cosmologies, paradigmatic model in LQC, as well as that of the Bianchi I model.
We have proposed a new prescription for the Hamiltonian constraint operator of
these models, that displays nicer features than those of previous proposals. In
particular, we get simpler superselection sectors with a global and
well-understood Wheeler-DeWitt limit in the large volume regime, which serve to
improve our understanding of the physical Hilbert space of these models.
| [
{
"created": "Mon, 26 Sep 2011 15:54:34 GMT",
"version": "v1"
}
] | 2011-09-27 | [
[
"Martín-Benito",
"Mercedes",
""
]
] | Loop Quantum Cosmology adapts the techniques of Loop Quantum Gravity in the quantization of homogeneous cosmological models obtained from General Relativity by symmetry reduction. As a necessary step towards the extraction of realistic results from Loop Quantum Cosmology, we should consider the inclusion of inhomogeneities, which play a central role in current cosmology. The main goal of this thesis is to progress in this direction. With this aim we have studied a natural test bed to incorporate inhomogeneities in Loop Quantum Cosmology: the linearly polarized Gowdy T3 model. This model can be regarded as a homogeneous Bianchi I background filled with inhomogeneities propagating in one direction. We have completed its quantization by means of a hybrid approach, that combines the loop quantization of the homogeneous sector, within the so-called improved dynamics scheme, with a Fock quantization for the inhomogeneities. In order to perform this quantization as thorough as possible, we have also reviewed the (improved dynamics) loop quantization of flat FRW cosmologies, paradigmatic model in LQC, as well as that of the Bianchi I model. We have proposed a new prescription for the Hamiltonian constraint operator of these models, that displays nicer features than those of previous proposals. In particular, we get simpler superselection sectors with a global and well-understood Wheeler-DeWitt limit in the large volume regime, which serve to improve our understanding of the physical Hilbert space of these models. |
gr-qc/0401122 | John D. Swain | John Swain | The Pauli Exclusion Principle and SU(2) Versus SO(3) in Loop Quantum
Gravity | An earlier paper (gr-qc/0305073) with a slightly different title
received an "honorable mention" in the 2003 Essay Competition of the Gravity
Research Foundation. This paper argues from geometric quantization for a
spin-statistics connection even when the SU(2) under consideration to define
``spin'' is not that of rotations in 3 space dimensions | Int.J.Mod.Phys. D12 (2003) 729 | null | null | gr-qc | null | Recent attempts to resolve the ambiguity in the loop quantum gravity
description of the quantization of area has led to the idea that $j=1$ edges of
spin-networks dominate in their contribution to black hole areas as opposed to
$j=1/2$ which would naively be expected. This suggests that the true gauge
group involved might be SO(3) rather than SU(2) with attendant difficulties. We
argue that the assumption that a version of the Pauli principle is present in
loop quantum gravity allows one to maintain SU(2) as the gauge group while
still naturally achieving the desired suppression of spin-1/2 punctures. Areas
come from $j=1$ punctures rather than $j=1/2$ punctures for much the same
reason that photons lead to macroscopic classically observable fields while
electrons do not.
| [
{
"created": "Thu, 29 Jan 2004 21:00:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Swain",
"John",
""
]
] | Recent attempts to resolve the ambiguity in the loop quantum gravity description of the quantization of area has led to the idea that $j=1$ edges of spin-networks dominate in their contribution to black hole areas as opposed to $j=1/2$ which would naively be expected. This suggests that the true gauge group involved might be SO(3) rather than SU(2) with attendant difficulties. We argue that the assumption that a version of the Pauli principle is present in loop quantum gravity allows one to maintain SU(2) as the gauge group while still naturally achieving the desired suppression of spin-1/2 punctures. Areas come from $j=1$ punctures rather than $j=1/2$ punctures for much the same reason that photons lead to macroscopic classically observable fields while electrons do not. |
2004.12138 | Yves Brihaye | Y. Brihaye, J. Renaux | Scalarized-charged wormholes in Einstein-Gauss-Bonnet gravity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein-Maxwell-Klein-Gordon Lagrangian is supplemented by a non-minimal
coupling of the real scalar field to the Gauss-Bonnet invariant. The non
minimal coupling function is chosen as a general second degree polynomial in
the scalar field for which the system is known to admit hairy black holes. The
new interaction leads naturally to a violation of the null energy condition,
allowing for wormholes to exist without the need of exotic matter.
Spherically symmetric, charged wormholes are constructed and their domain of
existence is determined in terms of the different choices of the non-minimal
coupling constants and of the electric charge. A special emphasis is set to the
case of the purely quadratic coupling function.
A phenomenon reminiscent to spontaneously scalarised black holes occurs for
wormholes. The interaction with the electromagnetic field leads to new families
of wormholes supported by a non-vanishing, large enough, electric charge.
| [
{
"created": "Sat, 25 Apr 2020 13:15:30 GMT",
"version": "v1"
}
] | 2020-04-28 | [
[
"Brihaye",
"Y.",
""
],
[
"Renaux",
"J.",
""
]
] | The Einstein-Maxwell-Klein-Gordon Lagrangian is supplemented by a non-minimal coupling of the real scalar field to the Gauss-Bonnet invariant. The non minimal coupling function is chosen as a general second degree polynomial in the scalar field for which the system is known to admit hairy black holes. The new interaction leads naturally to a violation of the null energy condition, allowing for wormholes to exist without the need of exotic matter. Spherically symmetric, charged wormholes are constructed and their domain of existence is determined in terms of the different choices of the non-minimal coupling constants and of the electric charge. A special emphasis is set to the case of the purely quadratic coupling function. A phenomenon reminiscent to spontaneously scalarised black holes occurs for wormholes. The interaction with the electromagnetic field leads to new families of wormholes supported by a non-vanishing, large enough, electric charge. |
2304.08520 | Zhen Zhong | Vitor Cardoso, Jo\~ao L. Costa, Jos\'e Nat\'ario, Zhen Zhong | Message in a bottle: energy extraction from bouncing geometries | 6 pages, 3 figures. v2: references added | null | 10.1103/PhysRevD.108.024071 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity phenomenology suggests the interesting possibility that black
holes are not eternal. Collapse could be halted by some unknown mechanism, or
Hawking radiation might leave behind a regular spacetime. Here we investigate a
simple bouncing geometry, with (outer and inner) apparent horizons but no event
horizon. We show that the inner horizon blueshifts radiation, which can lead to
a gigantic amplification of energy observable from far away regions. Thus, if
such phenomena exists in our universe, they can power high-energy bursts at
late stages in their lives, when the horizons disappear and spacetime bounces
back to a flat geometry.
| [
{
"created": "Mon, 17 Apr 2023 18:00:04 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Apr 2023 15:12:28 GMT",
"version": "v2"
}
] | 2023-08-09 | [
[
"Cardoso",
"Vitor",
""
],
[
"Costa",
"João L.",
""
],
[
"Natário",
"José",
""
],
[
"Zhong",
"Zhen",
""
]
] | Quantum gravity phenomenology suggests the interesting possibility that black holes are not eternal. Collapse could be halted by some unknown mechanism, or Hawking radiation might leave behind a regular spacetime. Here we investigate a simple bouncing geometry, with (outer and inner) apparent horizons but no event horizon. We show that the inner horizon blueshifts radiation, which can lead to a gigantic amplification of energy observable from far away regions. Thus, if such phenomena exists in our universe, they can power high-energy bursts at late stages in their lives, when the horizons disappear and spacetime bounces back to a flat geometry. |
1512.01172 | Ozcan Sert | \"Ozcan Sert | Regular Black Hole Solutions of the Non-minimally Coupled $Y(R)F^2$
Gravity | 11 pages, some typos are corrected | Journal of Mathematical Physics 57, 032501 (2016) | 10.1063/1.4944428 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study we investigate regular black hole solutions of the
non-minimally coupled $ Y(R)F^2 $ gravity model. We give two regular black hole
solutions and the corresponding non-minimal model for both electrically or
magnetically charged cases. We calculate all the energy conditions for these
solutions.
| [
{
"created": "Thu, 3 Dec 2015 17:51:19 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Mar 2016 08:46:15 GMT",
"version": "v2"
}
] | 2016-03-25 | [
[
"Sert",
"Özcan",
""
]
] | In this study we investigate regular black hole solutions of the non-minimally coupled $ Y(R)F^2 $ gravity model. We give two regular black hole solutions and the corresponding non-minimal model for both electrically or magnetically charged cases. We calculate all the energy conditions for these solutions. |
1609.01964 | Mohammad Malekjani | Mohammad Malekjani, Spyros Basilakos and Neda Heidari | Spherical collapse model and cluster number counts in power law $f(T)$
gravity | 9 pages, 7 figures, accepted in MNRAS | MNRAS 466(3), 3488 (2017) | 10.1093/mnras/stw3367 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the spherical collapse model (SCM) in the framework of spatially
flat power law $f(T) \propto (-T)^{b}$ gravity model. We find that the linear
and non-linear growth of spherical overdensities of this particular $f(T)$
model are affected by the power-law parameter $b$. Finally, we compute the
predicted number counts of virialized haloes in order to distinguish the
current $f(T)$ model from the expectations of the concordance $\Lambda$
cosmology. Specifically, the present analysis suggests that the $f(T)$ gravity
model with positive (negative) $b$ predicts more (less) virialized objects with
respect to those of $\Lambda$CDM.
| [
{
"created": "Sat, 3 Sep 2016 15:54:19 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Dec 2016 06:34:36 GMT",
"version": "v2"
}
] | 2017-02-17 | [
[
"Malekjani",
"Mohammad",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Heidari",
"Neda",
""
]
] | We study the spherical collapse model (SCM) in the framework of spatially flat power law $f(T) \propto (-T)^{b}$ gravity model. We find that the linear and non-linear growth of spherical overdensities of this particular $f(T)$ model are affected by the power-law parameter $b$. Finally, we compute the predicted number counts of virialized haloes in order to distinguish the current $f(T)$ model from the expectations of the concordance $\Lambda$ cosmology. Specifically, the present analysis suggests that the $f(T)$ gravity model with positive (negative) $b$ predicts more (less) virialized objects with respect to those of $\Lambda$CDM. |
1412.3604 | Kourosh Nozari | Amir Etemadi and Kourosh Nozari | A note on Hilbert Space Representation of Quantum Mechanics with Minimal
Length | 12 pages, no figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study some fundamental issues related to the Hilbert space representation
of quantum mechanics in the presence of a minimal length and maximal momentum.
In this framework, the maximally localized states and quasi-position
representation introduced by Kempf et al. are reconsidered and modified. We
show that all studies in recent years, including [15] and [16] need serious
modification in order to be a consistent framework for quantum mechanics in
Planck scale.
| [
{
"created": "Thu, 11 Dec 2014 11:10:04 GMT",
"version": "v1"
}
] | 2014-12-12 | [
[
"Etemadi",
"Amir",
""
],
[
"Nozari",
"Kourosh",
""
]
] | We study some fundamental issues related to the Hilbert space representation of quantum mechanics in the presence of a minimal length and maximal momentum. In this framework, the maximally localized states and quasi-position representation introduced by Kempf et al. are reconsidered and modified. We show that all studies in recent years, including [15] and [16] need serious modification in order to be a consistent framework for quantum mechanics in Planck scale. |
1910.07337 | Huan Yang | Huan Yang, B\'eatrice Bonga, Zhipeng Peng, Gongjie Li | Relativistic Mean Motion Resonance | 19 pages, 10 figures | Phys. Rev. D 100, 124056 (2019) | 10.1103/PhysRevD.100.124056 | null | gr-qc astro-ph.EP astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mean motion resonances are commonly seen in planetary systems, e.g., in the
formation of orbital structure of Jupiter's moons and the gaps in the rings of
Saturn. In this work we study their effects in fully relativistic systems. We
consider a model problem with two stellar mass black holes orbiting around a
supermassive black hole. By adopting a two time-scale expansion technique and
averaging over the fast varying orbital variables, we derive the effective
Hamiltonian for the slowly varying dynamical variables. The formalism is
illustrated with a n'_phi : n'_r : n_phi= 2:1:-2 resonance in Schwarzschild
spacetime, which naturally becomes the 3:2 resonance widely studied in the
Newtonian limit. We also derive the multi-body Hamiltonian in the
post-Newtonian regime, where the radial and azimuthal frequencies are different
because of the post-Newtonian precession. The capture and breaking conditions
for these relativistic mean motion resonances are also discussed. In
particular, pairs of stellar mass black holes surrounding the supermassive
black hole could be locked into resonances as they enter the LISA band, and
this would affect their gravitational wave waveforms.
| [
{
"created": "Wed, 16 Oct 2019 13:30:13 GMT",
"version": "v1"
}
] | 2020-01-01 | [
[
"Yang",
"Huan",
""
],
[
"Bonga",
"Béatrice",
""
],
[
"Peng",
"Zhipeng",
""
],
[
"Li",
"Gongjie",
""
]
] | Mean motion resonances are commonly seen in planetary systems, e.g., in the formation of orbital structure of Jupiter's moons and the gaps in the rings of Saturn. In this work we study their effects in fully relativistic systems. We consider a model problem with two stellar mass black holes orbiting around a supermassive black hole. By adopting a two time-scale expansion technique and averaging over the fast varying orbital variables, we derive the effective Hamiltonian for the slowly varying dynamical variables. The formalism is illustrated with a n'_phi : n'_r : n_phi= 2:1:-2 resonance in Schwarzschild spacetime, which naturally becomes the 3:2 resonance widely studied in the Newtonian limit. We also derive the multi-body Hamiltonian in the post-Newtonian regime, where the radial and azimuthal frequencies are different because of the post-Newtonian precession. The capture and breaking conditions for these relativistic mean motion resonances are also discussed. In particular, pairs of stellar mass black holes surrounding the supermassive black hole could be locked into resonances as they enter the LISA band, and this would affect their gravitational wave waveforms. |
gr-qc/0302064 | Jorge Pullin | Rodolfo Gambini, Rafael Porto and Jorge Pullin | Consistent discrete gravity solution of the problem of time: a model | 15 pages, no figures | null | 10.1142/9789812791238_0004 | LSU-GRG-021603 | gr-qc hep-th | null | The recently introduced consistent discrete lattice formulation of canonical
general relativity produces a discrete theory that is constraint-free. This
immediately allows to overcome several of the traditional obstacles posed by
the ``problem of time'' in totally constrained systems and quantum gravity and
cosmology. In particular, one can implement the Page--Wootters relational
quantization. This brief paper discusses this idea in the context of a simple
model system --the parameterized particle-- that is usually considered one of
the crucial tests for any proposal for solution to the problem of time in
quantum gravity.
| [
{
"created": "Sun, 16 Feb 2003 17:13:57 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Porto",
"Rafael",
""
],
[
"Pullin",
"Jorge",
""
]
] | The recently introduced consistent discrete lattice formulation of canonical general relativity produces a discrete theory that is constraint-free. This immediately allows to overcome several of the traditional obstacles posed by the ``problem of time'' in totally constrained systems and quantum gravity and cosmology. In particular, one can implement the Page--Wootters relational quantization. This brief paper discusses this idea in the context of a simple model system --the parameterized particle-- that is usually considered one of the crucial tests for any proposal for solution to the problem of time in quantum gravity. |
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