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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2110.05920 | Joao Magueijo | Joao Magueijo | Connection between cosmological time and the constants of Nature | Version to be published in Physical Review D | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We examine in greater detail the proposal that time is the conjugate of the
constants of nature. Fundamentally distinct times are associated with different
constants, a situation often found in "relational time" settings. We show in
detail how in regions dominated by a single constant the Hamiltonian constraint
can be reframed as a Schrodinger equation in the corresponding time, solved in
the connection representation by outgoing-only monochromatic plane waves moving
in a "space" that generalizes the Chern-Simons functional. We pay special
attention to the issues of unitarity and the measure employed for the inner
product. Normalizable superpositions can be built, including solitons,
"light-rays" and coherent/squeezed states saturating a Heisenberg uncertainty
relation between constants and their times. A healthy classical limit is
obtained for factorizable coherent states, both in mono-fluid and multi-fluid
situations. For the latter, we show how to deal with transition regions, where
one is passing on the baton from one time to to another, and investigate the
fate of the subdominant clock. For this purpose minisuperspace is best seen as
a dispersive medium, with packets moving with a group speed distinct from the
phase speed. We show that the motion of the packets' peaks reproduces the
classical limit even during the transition periods, and for subdominant clocks
once the transition is over. Deviations from the coherent/semi-classical limit
are expected in these cases, however. The fact that we have recently
transitioned from a decelerating to an accelerating Universe renders this
proposal potentially testable, as explored elsewhere.
| [
{
"created": "Tue, 12 Oct 2021 12:05:47 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2022 14:41:32 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Mar 2022 09:19:17 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Oct 2022 16:09:21 GMT",
"version": "v4"
}
] | 2022-10-14 | [
[
"Magueijo",
"Joao",
""
]
] | We examine in greater detail the proposal that time is the conjugate of the constants of nature. Fundamentally distinct times are associated with different constants, a situation often found in "relational time" settings. We show in detail how in regions dominated by a single constant the Hamiltonian constraint can be reframed as a Schrodinger equation in the corresponding time, solved in the connection representation by outgoing-only monochromatic plane waves moving in a "space" that generalizes the Chern-Simons functional. We pay special attention to the issues of unitarity and the measure employed for the inner product. Normalizable superpositions can be built, including solitons, "light-rays" and coherent/squeezed states saturating a Heisenberg uncertainty relation between constants and their times. A healthy classical limit is obtained for factorizable coherent states, both in mono-fluid and multi-fluid situations. For the latter, we show how to deal with transition regions, where one is passing on the baton from one time to to another, and investigate the fate of the subdominant clock. For this purpose minisuperspace is best seen as a dispersive medium, with packets moving with a group speed distinct from the phase speed. We show that the motion of the packets' peaks reproduces the classical limit even during the transition periods, and for subdominant clocks once the transition is over. Deviations from the coherent/semi-classical limit are expected in these cases, however. The fact that we have recently transitioned from a decelerating to an accelerating Universe renders this proposal potentially testable, as explored elsewhere. |
1512.00605 | Norbert Bodendorfer | Norbert Bodendorfer | A note on conformally compactified connection dynamics tailored for
anti-de Sitter space | 8 pages; v2: journal version, title changed, minor clarifications and
comments added | Class. Quantum Grav. 33 (2016) 237002 | 10.1088/0264-9381/33/23/237002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A framework conceptually based on the conformal techniques employed to study
the structure of the gravitational field at infinity is set up in the context
of loop quantum gravity to describe asymptotically anti-de Sitter quantum
spacetimes. A conformal compactification of the spatial slice is performed,
which, in terms of the rescaled metric, has now finite volume, and can thus be
conveniently described by spin networks states. The conformal factor used is a
physical scalar field, which has the necessary asymptotics for many
asymptotically AdS black hole solutions.
| [
{
"created": "Wed, 2 Dec 2015 08:22:18 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Nov 2016 11:07:54 GMT",
"version": "v2"
}
] | 2016-11-30 | [
[
"Bodendorfer",
"Norbert",
""
]
] | A framework conceptually based on the conformal techniques employed to study the structure of the gravitational field at infinity is set up in the context of loop quantum gravity to describe asymptotically anti-de Sitter quantum spacetimes. A conformal compactification of the spatial slice is performed, which, in terms of the rescaled metric, has now finite volume, and can thus be conveniently described by spin networks states. The conformal factor used is a physical scalar field, which has the necessary asymptotics for many asymptotically AdS black hole solutions. |
gr-qc/9812038 | Fernando Lombardo | Fernando C. Lombardo | Quantum to classical transition in quantum field theory | 127 pages, LaTex, 8 figures. PhD Thesis, University of Buenos Aires
(in Spanish) | null | null | null | gr-qc hep-th | null | We study the quatum to classical transition process in the context of quantum
field theory. Extending the influence functional formalism of Feynman and
Vernon, we study the decoherence process for self-interacting quantum fields in
flat space. We also use this formalism for arbitrary geometries to analyze the
quantum to classical transition in quantum gravity. After summarizing the main
results known for the quantum Brownian motion, we consider a self-interacting
field theory in Minkowski spacetime. We compute a coarse grained effective
action by integrating out the field modes with wavelength shorter than a
critical value. From this effective action we obtain the evolution equation for
the reduced density matrix (master equation). We compute the diffusion
coefficients for this equation and analyze the decoherence induced on the
long-wavelength modes. We generalize the results to the case of a conformally
coupled scalar field in de Sitter spacetime. We show that the decoherence is
effective as long as the critical wavelength is taken to be not shorter than
the Hubble radius. On the other hand, we study the classical limit for
scalar-tensorial models in two dimensions. We consider different couplings
between the dilaton and the scalar field. We discuss the Hawking radiation
process and, from an exact evaluation of the influence functional, we study the
conditions by which decoherence ensures the validity of the semiclassical
approximation in cosmological metrics. Finally we consider four dimensional
models with massive scalar fields, arbitrary coupled to the geometry. We
compute the Einstein-Langevin equations in order to study the effect of the
fluctuations induced by the quantum fields on the classical geometry.
| [
{
"created": "Fri, 11 Dec 1998 15:03:11 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Lombardo",
"Fernando C.",
""
]
] | We study the quatum to classical transition process in the context of quantum field theory. Extending the influence functional formalism of Feynman and Vernon, we study the decoherence process for self-interacting quantum fields in flat space. We also use this formalism for arbitrary geometries to analyze the quantum to classical transition in quantum gravity. After summarizing the main results known for the quantum Brownian motion, we consider a self-interacting field theory in Minkowski spacetime. We compute a coarse grained effective action by integrating out the field modes with wavelength shorter than a critical value. From this effective action we obtain the evolution equation for the reduced density matrix (master equation). We compute the diffusion coefficients for this equation and analyze the decoherence induced on the long-wavelength modes. We generalize the results to the case of a conformally coupled scalar field in de Sitter spacetime. We show that the decoherence is effective as long as the critical wavelength is taken to be not shorter than the Hubble radius. On the other hand, we study the classical limit for scalar-tensorial models in two dimensions. We consider different couplings between the dilaton and the scalar field. We discuss the Hawking radiation process and, from an exact evaluation of the influence functional, we study the conditions by which decoherence ensures the validity of the semiclassical approximation in cosmological metrics. Finally we consider four dimensional models with massive scalar fields, arbitrary coupled to the geometry. We compute the Einstein-Langevin equations in order to study the effect of the fluctuations induced by the quantum fields on the classical geometry. |
1009.3093 | Shayeste Ghaffari | K. Karami, A. Sheykhi, N. Sahraei, S. Ghaffari | Generalized second law of thermodynamics in modified FRW cosmology with
corrected entropy-area relation | 9 pages, accepted for publication in Europhysics Letters | Europhys.Lett.93:29002,2011 | 10.1209/0295-5075/93/29002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the corrected entropy-area relation motivated by the loop quantum
gravity, we investigate the validity of the generalized second law of
thermodynamics in the framework of modified FRW cosmology. We consider a
non-flat universe filled with an interacting viscous dark energy with dark
matter and radiation. The boundary of the universe is assumed to be the
dynamical apparent horizon. We find out that the generalized second law is
always satisfied throughout the history of the universe for any spatial
curvature regardless of the dark energy model.
| [
{
"created": "Thu, 16 Sep 2010 05:49:36 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Jan 2011 10:14:38 GMT",
"version": "v2"
}
] | 2011-04-21 | [
[
"Karami",
"K.",
""
],
[
"Sheykhi",
"A.",
""
],
[
"Sahraei",
"N.",
""
],
[
"Ghaffari",
"S.",
""
]
] | Using the corrected entropy-area relation motivated by the loop quantum gravity, we investigate the validity of the generalized second law of thermodynamics in the framework of modified FRW cosmology. We consider a non-flat universe filled with an interacting viscous dark energy with dark matter and radiation. The boundary of the universe is assumed to be the dynamical apparent horizon. We find out that the generalized second law is always satisfied throughout the history of the universe for any spatial curvature regardless of the dark energy model. |
2306.13044 | Jose M. Isidro | P. Fernandez de Cordoba, J.M. Isidro, Rudranil Roy | Spacetime metric from quantum-gravity corrected Feynman propagators | Refs. added, some clarifications made | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Differentiation of the scalar Feynman propagator with respect to the
spacetime coordinates yields the metric on the background spacetime that the
scalar particle propagates in. Now Feynman propagators can be modified in order
to include quantum-gravity corrections as induced by a zero-point length $L>0$.
These corrections cause the length element $\sqrt{s^2}$ to be replaced with
$\sqrt{s^2 + 4L^2}$ within the Feynman propagator. In this paper we compute the
metrics derived from both the quantum-gravity free propagators and from their
quantum-gravity corrected counterparts. We verify that the latter propagators
yield the same spacetime metrics as the former, provided one measures distances
greater than the quantum of length $L$. We perform this analysis in the case of
the background spacetime $\mathbb{R}^D$ in the Euclidean sector.
| [
{
"created": "Thu, 22 Jun 2023 17:11:11 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2023 19:04:56 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Jan 2024 15:06:31 GMT",
"version": "v3"
}
] | 2024-01-18 | [
[
"de Cordoba",
"P. Fernandez",
""
],
[
"Isidro",
"J. M.",
""
],
[
"Roy",
"Rudranil",
""
]
] | Differentiation of the scalar Feynman propagator with respect to the spacetime coordinates yields the metric on the background spacetime that the scalar particle propagates in. Now Feynman propagators can be modified in order to include quantum-gravity corrections as induced by a zero-point length $L>0$. These corrections cause the length element $\sqrt{s^2}$ to be replaced with $\sqrt{s^2 + 4L^2}$ within the Feynman propagator. In this paper we compute the metrics derived from both the quantum-gravity free propagators and from their quantum-gravity corrected counterparts. We verify that the latter propagators yield the same spacetime metrics as the former, provided one measures distances greater than the quantum of length $L$. We perform this analysis in the case of the background spacetime $\mathbb{R}^D$ in the Euclidean sector. |
0903.4757 | Belinch\'on Jos\'e Antonio | Jos\'e Antonio Belinch\'on | Massive cosmic strings in Bianchi type II | 7 pages, RevTeX | Astrophys. Space Sci. 323, 307, (2009) | 10.1007/s10509-009-0065-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a massive cosmic strings with BII symmetries cosmological models in
two contexts. The first of them is the standard one with a barotropic equation
of state. In the second one we explore the possibility of taking into account
variable \textquotedblleft constants\textquotedblright ($G$ and $\Lambda
).$Both models are studied under the self-similar hypothesis. We put special
emphasis in calculating the numerical values for the equations of state. We
find that for $\omega\in(0,1]$, $G$, is a growing time function while
$\Lambda$, behaves as positive decreasing time function. If $\omega=0,$ both
\textquotedblleft constants\textquotedblright, $G$ and $\Lambda,$ behave as
true constants.
| [
{
"created": "Fri, 27 Mar 2009 10:01:22 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Belinchón",
"José Antonio",
""
]
] | We study a massive cosmic strings with BII symmetries cosmological models in two contexts. The first of them is the standard one with a barotropic equation of state. In the second one we explore the possibility of taking into account variable \textquotedblleft constants\textquotedblright ($G$ and $\Lambda ).$Both models are studied under the self-similar hypothesis. We put special emphasis in calculating the numerical values for the equations of state. We find that for $\omega\in(0,1]$, $G$, is a growing time function while $\Lambda$, behaves as positive decreasing time function. If $\omega=0,$ both \textquotedblleft constants\textquotedblright, $G$ and $\Lambda,$ behave as true constants. |
2311.03656 | Ryan Magee | Ryan Magee, Maximiliano Isi, Ethan Payne, Katerina Chatziioannou, Will
M. Farr, Geraint Pratten, and Salvatore Vitale | The impact of selection biases on tests of general relativity with
gravitational-wave inspirals | null | null | 10.1103/PhysRevD.109.023014 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Tests of general relativity with gravitational wave observations from merging
compact binaries continue to confirm Einstein's theory of gravity with
increasing precision. However, these tests have so far only been applied to
signals that were first confidently detected by matched-filter searches
assuming general relativity templates. This raises the question of selection
biases: what is the largest deviation from general relativity that current
searches can detect, and are current constraints on such deviations necessarily
narrow because they are based on signals that were detected by templated
searches in the first place? In this paper, we estimate the impact of selection
effects for tests of the inspiral phase evolution of compact binary signals
with a simplified version of the GstLAL search pipeline. We find that selection
biases affect the search for very large values of the deviation parameters,
much larger than the constraints implied by the detected signals. Therefore,
combined population constraints from confidently detected events are mostly
unaffected by selection biases, with the largest effect being a broadening at
the $\sim10$ % level for the $-1$PN term. These findings suggest that current
population constraints on the inspiral phase are robust without factoring in
selection biases. Our study does not rule out a disjoint, undetectable binary
population with large deviations from general relativity, or stronger selection
effects in other tests or search procedures.
| [
{
"created": "Tue, 7 Nov 2023 01:58:12 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jan 2024 15:07:34 GMT",
"version": "v2"
}
] | 2024-01-29 | [
[
"Magee",
"Ryan",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Payne",
"Ethan",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Farr",
"Will M.",
""
],
[
"Pratten",
"Geraint",
""
],
[
"Vitale",
"Salvatore",
""
]
] | Tests of general relativity with gravitational wave observations from merging compact binaries continue to confirm Einstein's theory of gravity with increasing precision. However, these tests have so far only been applied to signals that were first confidently detected by matched-filter searches assuming general relativity templates. This raises the question of selection biases: what is the largest deviation from general relativity that current searches can detect, and are current constraints on such deviations necessarily narrow because they are based on signals that were detected by templated searches in the first place? In this paper, we estimate the impact of selection effects for tests of the inspiral phase evolution of compact binary signals with a simplified version of the GstLAL search pipeline. We find that selection biases affect the search for very large values of the deviation parameters, much larger than the constraints implied by the detected signals. Therefore, combined population constraints from confidently detected events are mostly unaffected by selection biases, with the largest effect being a broadening at the $\sim10$ % level for the $-1$PN term. These findings suggest that current population constraints on the inspiral phase are robust without factoring in selection biases. Our study does not rule out a disjoint, undetectable binary population with large deviations from general relativity, or stronger selection effects in other tests or search procedures. |
1311.5915 | Emmanuil Saridakis | Spyros Basilakos (RCAAM, Academy of Athens), Alexandros P. Kouretsis
(Aristotle U., Thessaloniki), Emmanuel N. Saridakis (Natl. Tech. U., Athens
and Valparaiso U., Catolica), Panayiotis Stavrinos (Athens U.) | Resembling dark energy and modified gravity with Finsler-Randers
cosmology | 12 pages, accepted for publication at Phys. Rev. D | Phys. Rev. D 88 (2013) 123510 | 10.1103/PhysRevD.88.123510 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we present the cosmological equivalence between the
relativistic Finsler-Randers cosmology, with dark energy and modified gravity
constructions, at the background level. Starting from a small deviation from
the quadraticity of the Riemannian geometry, through which the local structure
of General Relativity is modified and the curvature theory is extended, we
extract the modified Friedmann equation. The corresponding extended
Finsler-Randers cosmology is very interesting, and it can mimic dark-energy and
modified gravity, describing a large class of scale-factor evolutions, from
inflation to late-time acceleration, including the phantom regime. In this
respect, the non-trivial universe evolution is not attributed to a new scalar
field, or to gravitational modification, but it arises from the modification of
the geometry itself.
| [
{
"created": "Thu, 21 Nov 2013 19:36:03 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Dec 2013 15:41:17 GMT",
"version": "v2"
}
] | 2013-12-17 | [
[
"Basilakos",
"Spyros",
"",
"RCAAM, Academy of Athens"
],
[
"Kouretsis",
"Alexandros P.",
"",
"Aristotle U., Thessaloniki"
],
[
"Saridakis",
"Emmanuel N.",
"",
"Natl. Tech. U., Athens\n and Valparaiso U., Catolica"
],
[
"Stavrinos",
"Panayiotis",
"",
"Athens U."
]
] | In this article we present the cosmological equivalence between the relativistic Finsler-Randers cosmology, with dark energy and modified gravity constructions, at the background level. Starting from a small deviation from the quadraticity of the Riemannian geometry, through which the local structure of General Relativity is modified and the curvature theory is extended, we extract the modified Friedmann equation. The corresponding extended Finsler-Randers cosmology is very interesting, and it can mimic dark-energy and modified gravity, describing a large class of scale-factor evolutions, from inflation to late-time acceleration, including the phantom regime. In this respect, the non-trivial universe evolution is not attributed to a new scalar field, or to gravitational modification, but it arises from the modification of the geometry itself. |
gr-qc/9811095 | Luis Lehner | Luis Lehner | A dissipative algorithm for wave-like equations in the characteristic
formulation | 23 pages, 7 figures | null | 10.1006/jcph.1998.6137 | null | gr-qc | null | We present a dissipative algorithm for solving nonlinear wave-like equations
when the initial data is specified on characteristic surfaces. The dissipative
properties built in this algorithm make it particularly useful when studying
the highly nonlinear regime where previous methods have failed to give a stable
evolution in three dimensions. The algorithm presented in this work is directly
applicable to hyperbolic systems proper of Electromagnetism, Yang-Mills and
General Relativity theories. We carry out an analysis of the stability of the
algorithm and test its properties with linear waves propagating on a Minkowski
background and the scattering off a Scwharszchild black hole in General
Relativity.
| [
{
"created": "Mon, 30 Nov 1998 15:56:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Lehner",
"Luis",
""
]
] | We present a dissipative algorithm for solving nonlinear wave-like equations when the initial data is specified on characteristic surfaces. The dissipative properties built in this algorithm make it particularly useful when studying the highly nonlinear regime where previous methods have failed to give a stable evolution in three dimensions. The algorithm presented in this work is directly applicable to hyperbolic systems proper of Electromagnetism, Yang-Mills and General Relativity theories. We carry out an analysis of the stability of the algorithm and test its properties with linear waves propagating on a Minkowski background and the scattering off a Scwharszchild black hole in General Relativity. |
gr-qc/0106095 | Jonathan Halliwell | J.J.Halliwell and J.Thorwart | Decoherent histories analysis of the relativistic particle | 51 pages, plain Tex | Phys.Rev. D64 (2001) 124018 | 10.1103/PhysRevD.64.124018 | Imperial College preprint TP/0-01/20 | gr-qc | null | The Klein-Gordon equation is a useful test arena for quantum cosmological
models described by the Wheeler-DeWitt equation. We use the decoherent
histories approach to quantum theory to obtain the probability that a free
relativistic particle crosses a section of spacelike surface. The decoherence
functional is constructed using path integral methods with initial states
attached using the (positive definite) ``induced'' inner product between
solutions to the constraint equation. The notion of crossing a spacelike
surface requires some attention, given that the paths in the path integral may
cross such a surface many times, but we show that first and last crossings are
in essence the only useful possibilities. Different possible results for the
probabilities are obtained, depending on how the relativistic particle is
quantized (using the Klein-Gordon equation, or its square root, with the
associated Newton-Wigner states). In the Klein-Gordon quantization, the
decoherence is only approximate, due to the fact that the paths in the path
integral may go backwards and forwards in time. We compare with the results
obtained using operators which commute with the constraint (the ``evolving
constants'' method).
| [
{
"created": "Fri, 29 Jun 2001 13:26:34 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jul 2001 14:01:48 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Halliwell",
"J. J.",
""
],
[
"Thorwart",
"J.",
""
]
] | The Klein-Gordon equation is a useful test arena for quantum cosmological models described by the Wheeler-DeWitt equation. We use the decoherent histories approach to quantum theory to obtain the probability that a free relativistic particle crosses a section of spacelike surface. The decoherence functional is constructed using path integral methods with initial states attached using the (positive definite) ``induced'' inner product between solutions to the constraint equation. The notion of crossing a spacelike surface requires some attention, given that the paths in the path integral may cross such a surface many times, but we show that first and last crossings are in essence the only useful possibilities. Different possible results for the probabilities are obtained, depending on how the relativistic particle is quantized (using the Klein-Gordon equation, or its square root, with the associated Newton-Wigner states). In the Klein-Gordon quantization, the decoherence is only approximate, due to the fact that the paths in the path integral may go backwards and forwards in time. We compare with the results obtained using operators which commute with the constraint (the ``evolving constants'' method). |
1209.1257 | Abhijnan Rej | Abhijnan Rej | Dimension, Divergence and Desingularization | A lightly-edited version of a submission to the 2012 FQXi Essay
Contest | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I argue that consistent geometrical descriptions of the universe are far from
unique even as low-energy limits and that an abstract "atomic" description of
spacetime and gauge-theoretic geometry in terms of K-theories of algebraic and
analytic cycles has the promise to restore uniqueness to our description.
| [
{
"created": "Thu, 6 Sep 2012 11:29:16 GMT",
"version": "v1"
}
] | 2012-09-07 | [
[
"Rej",
"Abhijnan",
""
]
] | I argue that consistent geometrical descriptions of the universe are far from unique even as low-energy limits and that an abstract "atomic" description of spacetime and gauge-theoretic geometry in terms of K-theories of algebraic and analytic cycles has the promise to restore uniqueness to our description. |
2301.02881 | Juan M. Z\'arate Pretel | Juan M. Z. Pretel | Moment of inertia of slowly rotating anisotropic neutron stars in
$f(R,T)$ gravity | 9 pages, 5 figures | Mod. Phys. Lett. A 37 (2022) 2250188 | 10.1142/S0217732322501887 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of $f(R,T)$ theories of gravity, we investigate the
hydrostatic equilibrium of anisotropic neutron stars with a physically relevant
equation of state (EoS) for the radial pressure. In particular, we focus on the
$f(R,T) = R+ 2\beta T$ model, where $\beta$ is a minimal coupling constant. In
the slowly rotating approximation, we derive the modified TOV equations and the
expression for the relativistic moment of inertia. The main properties of
neutron stars, such as radius, mass and moment of inertia, are studied in
detail. Our results revel that the main consequence of the $2\beta T$ term is a
substantial increase in the surface radius for low enough central densities.
Nevertheless, such a term slightly modifies the total gravitational mass and
moment of inertia of the slowly rotating stars. Furthermore, the changes are
noticeable when anisotropy is incorporated into the stellar fluid, and it is
possible to obtain higher masses that are consistent with the current
observational data.
| [
{
"created": "Sat, 7 Jan 2023 16:02:39 GMT",
"version": "v1"
}
] | 2023-01-10 | [
[
"Pretel",
"Juan M. Z.",
""
]
] | Within the framework of $f(R,T)$ theories of gravity, we investigate the hydrostatic equilibrium of anisotropic neutron stars with a physically relevant equation of state (EoS) for the radial pressure. In particular, we focus on the $f(R,T) = R+ 2\beta T$ model, where $\beta$ is a minimal coupling constant. In the slowly rotating approximation, we derive the modified TOV equations and the expression for the relativistic moment of inertia. The main properties of neutron stars, such as radius, mass and moment of inertia, are studied in detail. Our results revel that the main consequence of the $2\beta T$ term is a substantial increase in the surface radius for low enough central densities. Nevertheless, such a term slightly modifies the total gravitational mass and moment of inertia of the slowly rotating stars. Furthermore, the changes are noticeable when anisotropy is incorporated into the stellar fluid, and it is possible to obtain higher masses that are consistent with the current observational data. |
2302.13333 | Serge Parnovsky | S L Parnovsky | Can black holes be a source of dark energy? | 6 pages | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The hypothesis that the mass of black holes increases with time according to
the same law as the volume of the part of the Universe containing it and
therefore the population of BHs is similar to dark energy in its action was
recently proposed. We demonstrate the reasons why it cannot be accepted, even
if all the assumptions on which this hypothesis is based are considered true.
| [
{
"created": "Sun, 26 Feb 2023 15:18:58 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Mar 2023 20:10:07 GMT",
"version": "v2"
}
] | 2023-03-28 | [
[
"Parnovsky",
"S L",
""
]
] | The hypothesis that the mass of black holes increases with time according to the same law as the volume of the part of the Universe containing it and therefore the population of BHs is similar to dark energy in its action was recently proposed. We demonstrate the reasons why it cannot be accepted, even if all the assumptions on which this hypothesis is based are considered true. |
1803.09534 | Daniela Doneva | Stoytcho S. Yazadjiev, Daniela D. Doneva, Kostas D. Kokkotas | Tidal Love numbers of neutron stars in $f(R)$ gravity | 10 pages, 3 figures | null | 10.1140/epjc/s10052-018-6285-z | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent detection of gravitational waves from a neutron star merger was a
significant step towards constraining the nuclear matter equation of state by
using the tidal Love numbers (TLNs) of the merging neutron stars. Measuring or
constraining the neutron star TLNs allows us in principle to exclude or
constraint many equations of state. This approach, however, has the drawback
that many modified theories of gravity could produce deviations from General
Relativity similar to the deviations coming from the uncertainties in the
equation of state. The first and the most natural step in resolving the
mentioned problem is to quantify the effects on the TLNs from the modifications
of General Relativity. With this motivation in mind, in the present paper we
calculate the TLNs of (non-rotating) neutron stars in $f(R)$ gravity. For this
purpose, we first derived the equations describing both the polar and the axial
stationary perturbations of neutron stars in a particular class of $f(R)$
gravity, the so-called $R^2$-gravity. Then, by solving numerically the
perturbation equations, we calculate explicitly the polar and the axial $l=2$
TLNs of the neutron stars in $R^2$-gravity for three characteristic realistic
equations of state. Our results show that while the polar TLNs are slightly
influenced by the $R^2$ modification of General Relativity, the axial TLNs can
be several times larger (in terms of the absolute value) compared to the
general relativistic case.
| [
{
"created": "Mon, 26 Mar 2018 12:03:31 GMT",
"version": "v1"
}
] | 2018-11-14 | [
[
"Yazadjiev",
"Stoytcho S.",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | The recent detection of gravitational waves from a neutron star merger was a significant step towards constraining the nuclear matter equation of state by using the tidal Love numbers (TLNs) of the merging neutron stars. Measuring or constraining the neutron star TLNs allows us in principle to exclude or constraint many equations of state. This approach, however, has the drawback that many modified theories of gravity could produce deviations from General Relativity similar to the deviations coming from the uncertainties in the equation of state. The first and the most natural step in resolving the mentioned problem is to quantify the effects on the TLNs from the modifications of General Relativity. With this motivation in mind, in the present paper we calculate the TLNs of (non-rotating) neutron stars in $f(R)$ gravity. For this purpose, we first derived the equations describing both the polar and the axial stationary perturbations of neutron stars in a particular class of $f(R)$ gravity, the so-called $R^2$-gravity. Then, by solving numerically the perturbation equations, we calculate explicitly the polar and the axial $l=2$ TLNs of the neutron stars in $R^2$-gravity for three characteristic realistic equations of state. Our results show that while the polar TLNs are slightly influenced by the $R^2$ modification of General Relativity, the axial TLNs can be several times larger (in terms of the absolute value) compared to the general relativistic case. |
1310.0627 | Hirotada Okawa | Masaru Shibata, Keisuke Taniguchi, Hirotada Okawa, Alessandra Buonanno | Coalescence of binary neutron stars in a scalar-tensor theory of gravity | 17 pages, 12 figures | null | 10.1103/PhysRevD.89.084005 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We carry out numerical-relativity simulations of coalescing binary neutron
stars in a scalar-tensor theory that admits spontaneous scalarization. We model
neutron stars with realistic equations of state. We choose the free parameters
of the theory taking into account the constraints imposed by the latest
observations of neutron-star-- white-dwarf binaries with pulsar timing. We show
that even within those severe constraints, scalarization can still affect the
evolution of the binary neutron stars not only during the late inspiral, but
also during the merger stage. We also confirm that even when both neutron stars
have quite small scalar charge at large separations, they can be strongly
scalarized dynamically during the final stages of the inspiral. In particular,
we identify the binary parameters for which scalarization occurs either during
the late inspiral or only after the onset of the merger when a remnant,
supramassive or hypermassive neutron star is formed. We also discuss how those
results can impact the extraction of physical information on gravitational
waves once they are detected.
| [
{
"created": "Wed, 2 Oct 2013 09:10:30 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Oct 2013 10:34:54 GMT",
"version": "v2"
}
] | 2015-06-17 | [
[
"Shibata",
"Masaru",
""
],
[
"Taniguchi",
"Keisuke",
""
],
[
"Okawa",
"Hirotada",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | We carry out numerical-relativity simulations of coalescing binary neutron stars in a scalar-tensor theory that admits spontaneous scalarization. We model neutron stars with realistic equations of state. We choose the free parameters of the theory taking into account the constraints imposed by the latest observations of neutron-star-- white-dwarf binaries with pulsar timing. We show that even within those severe constraints, scalarization can still affect the evolution of the binary neutron stars not only during the late inspiral, but also during the merger stage. We also confirm that even when both neutron stars have quite small scalar charge at large separations, they can be strongly scalarized dynamically during the final stages of the inspiral. In particular, we identify the binary parameters for which scalarization occurs either during the late inspiral or only after the onset of the merger when a remnant, supramassive or hypermassive neutron star is formed. We also discuss how those results can impact the extraction of physical information on gravitational waves once they are detected. |
2206.13062 | Arthur Touati | Arthur Touati | High-frequency solutions to the constraint equations | 36 pages, revised version after referee reports, accepted in
Communications in Mathematical Physics | null | 10.1007/s00220-023-04715-8 | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | We construct high-frequency initial data for the Einstein vacuum equations in
dimension 3+1 by solving the constraint equations on $\mathbb{R}^3$. Our family
of solutions $(\bar{g}_\lambda,K_\lambda)_{\lambda\in(0,1]}$ is defined through
a high-frequency expansion similar to the geometric optics approach and is
close in a particular sense to the data of a null dust. In order to solve the
constraint equations, we use their conformal formulation and the main challenge
of our proof is to adapt this method in the high-frequency context. The main
application of this article is our companion article \cite{Touati2022a} where
we construct high-frequency gravitational waves in generalised wave gauge.
| [
{
"created": "Mon, 27 Jun 2022 06:06:07 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Apr 2023 12:36:49 GMT",
"version": "v2"
}
] | 2023-05-17 | [
[
"Touati",
"Arthur",
""
]
] | We construct high-frequency initial data for the Einstein vacuum equations in dimension 3+1 by solving the constraint equations on $\mathbb{R}^3$. Our family of solutions $(\bar{g}_\lambda,K_\lambda)_{\lambda\in(0,1]}$ is defined through a high-frequency expansion similar to the geometric optics approach and is close in a particular sense to the data of a null dust. In order to solve the constraint equations, we use their conformal formulation and the main challenge of our proof is to adapt this method in the high-frequency context. The main application of this article is our companion article \cite{Touati2022a} where we construct high-frequency gravitational waves in generalised wave gauge. |
2111.09214 | Gregory Ashton | Gregory Ashton, Tim Dietrich | Understanding binary neutron star collisions with hypermodels | 10 pages, 5 figures, 1 table. Published Nature Astronomy | Nature Astronomy, Volume 6, p. 961-967 (2022) | 10.1038/s41550-022-01707-x | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Gravitational waves from the collision of binary neutron stars provide a
unique opportunity to study the behaviour of supranuclear matter, the
fundamental properties of gravity, and the cosmic history of our Universe.
However, given the complexity of Einstein's Field Equations, theoretical models
that enable source-property inference suffer from systematic uncertainties due
to simplifying assumptions. We develop a hypermodel approach to compare and
measure the uncertainty gravitational-wave approximants. Using state-of-the-art
models, we apply this new technique to the binary neutron star observations
GW170817 and GW190425 and the sub-threshold candidate GW200311_103121. Our
analysis reveals subtle systematic differences between waveform models, and a
frequency-dependence study suggests that this is due to the treatment of the
tidal sector. This new technique provides a proving ground for model
development, and a means to identify waveform-systematics in future observing
runs where detector improvements will increase the number and clarity of binary
neutron star collisions we observe.
| [
{
"created": "Wed, 17 Nov 2021 16:14:27 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Nov 2022 16:14:09 GMT",
"version": "v2"
}
] | 2022-11-02 | [
[
"Ashton",
"Gregory",
""
],
[
"Dietrich",
"Tim",
""
]
] | Gravitational waves from the collision of binary neutron stars provide a unique opportunity to study the behaviour of supranuclear matter, the fundamental properties of gravity, and the cosmic history of our Universe. However, given the complexity of Einstein's Field Equations, theoretical models that enable source-property inference suffer from systematic uncertainties due to simplifying assumptions. We develop a hypermodel approach to compare and measure the uncertainty gravitational-wave approximants. Using state-of-the-art models, we apply this new technique to the binary neutron star observations GW170817 and GW190425 and the sub-threshold candidate GW200311_103121. Our analysis reveals subtle systematic differences between waveform models, and a frequency-dependence study suggests that this is due to the treatment of the tidal sector. This new technique provides a proving ground for model development, and a means to identify waveform-systematics in future observing runs where detector improvements will increase the number and clarity of binary neutron star collisions we observe. |
1406.4526 | Edmund Schluessel | Edmund Schluessel | Propagation of gravitational waves in a universe with slowly-changing
equation of state | figures to be added later | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An exact solution for the expansion of a flat universe with dark energy
evolving according to a simple model is explored. The equation for weak
primordial gravitational waves propagating in this universe is solved and
explored; gravitational waves in a flat cosmology possessing both a "big bang"
singularity and a "big rip" singularity can be described with confluent Heun
functions. We develop approximation methods for confluent Heun equations in
regimes of interest to gravitational wave astronomers and predict the
diminution in gravitational wave amplitude in a universe with both a Big Bang
and a Big Rip.
| [
{
"created": "Tue, 17 Jun 2014 20:22:38 GMT",
"version": "v1"
}
] | 2014-06-19 | [
[
"Schluessel",
"Edmund",
""
]
] | An exact solution for the expansion of a flat universe with dark energy evolving according to a simple model is explored. The equation for weak primordial gravitational waves propagating in this universe is solved and explored; gravitational waves in a flat cosmology possessing both a "big bang" singularity and a "big rip" singularity can be described with confluent Heun functions. We develop approximation methods for confluent Heun equations in regimes of interest to gravitational wave astronomers and predict the diminution in gravitational wave amplitude in a universe with both a Big Bang and a Big Rip. |
0811.0629 | James Lindesay | Beth A. Brown and James Lindesay | Construction of a Penrose Diagram for an Accreting Black Hole | 7 pages, 1 figure | Class.Quant.Grav.26:045010,2009 | 10.1088/0264-9381/26/4/045010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Penrose diagram is constructed for a spatially coherent black hole that
accretes at stepwise steady rates as measured by a distant observer from an
initial state described by a metric of Minkowski form. Coordinate lines are
computationally derived, and radial light-like trajectories verify the
viability of the diagram. Coordinate dependencies of significant features, such
as the horizon and radial mass scale, are clearly demonstrated on the diagram.
The onset of a singularity at the origin is shown to open a new region in
space-time that contains the interior of the black hole.
| [
{
"created": "Tue, 4 Nov 2008 23:35:12 GMT",
"version": "v1"
}
] | 2009-02-09 | [
[
"Brown",
"Beth A.",
""
],
[
"Lindesay",
"James",
""
]
] | A Penrose diagram is constructed for a spatially coherent black hole that accretes at stepwise steady rates as measured by a distant observer from an initial state described by a metric of Minkowski form. Coordinate lines are computationally derived, and radial light-like trajectories verify the viability of the diagram. Coordinate dependencies of significant features, such as the horizon and radial mass scale, are clearly demonstrated on the diagram. The onset of a singularity at the origin is shown to open a new region in space-time that contains the interior of the black hole. |
1611.07802 | Vicente Antunes | V. Antunes, I. Bediaga, M. Novello | Gravitational mechanism for baryogenesis in the cosmological QCD phase
transition | 14 pages, 4 figures, replacement with correct figures and captions | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the biggest puzzles in modern cosmology is the observed baryon
asymmetry in the universe. In current models of baryogenesis gravity plays a
secondary role, although the process is believed to have happened in the early
universe, under the influence of an intense gravitational field. In the present
work we resume Sakharov's original program for baryogenesis and propose a
central role for gravity in the process. This is achieved through a non-minimal
coupling (NMC) between the gravitational field and both the strong interaction
field and the quark fields. When in action, the present mechanism leads to
baryon number non-conservation and CP violation. Moreover, the NMC induces
reduced effective quark masses, which favours a first order QCD phase
transition. As a consequence, a baryon asymmetry can be attained in the
transition from the quark epoch to the hadron epoch.
| [
{
"created": "Wed, 23 Nov 2016 14:01:25 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Nov 2016 18:29:14 GMT",
"version": "v2"
}
] | 2016-11-28 | [
[
"Antunes",
"V.",
""
],
[
"Bediaga",
"I.",
""
],
[
"Novello",
"M.",
""
]
] | One of the biggest puzzles in modern cosmology is the observed baryon asymmetry in the universe. In current models of baryogenesis gravity plays a secondary role, although the process is believed to have happened in the early universe, under the influence of an intense gravitational field. In the present work we resume Sakharov's original program for baryogenesis and propose a central role for gravity in the process. This is achieved through a non-minimal coupling (NMC) between the gravitational field and both the strong interaction field and the quark fields. When in action, the present mechanism leads to baryon number non-conservation and CP violation. Moreover, the NMC induces reduced effective quark masses, which favours a first order QCD phase transition. As a consequence, a baryon asymmetry can be attained in the transition from the quark epoch to the hadron epoch. |
1310.0780 | Nelson Videla Dr. | Ramon Herrera, Marco Olivares, and Nelson Videla | General dissipative coefficient in warm intermediate and logamediate
inflation | 29 pages, 9 figures | Physical Review D 88, 063535 (2013) | 10.1103/PhysRevD.88.063535 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a general form for the dissipative coefficient
$\Gamma(T,\phi)=C_\phi\,T^{m}/\phi^{m-1}$ in the context of warm intermediate
and logamediate inflationary universe models. We analyze these models in the
weak and strong dissipative regimes. In the slow-roll approximation, we
describe in great detail the characteristics of these models. In both regimes,
we use recent data from the WMAP nine-year data and Planck data to constrain
the parameters appearing in our models.
| [
{
"created": "Wed, 2 Oct 2013 17:31:17 GMT",
"version": "v1"
}
] | 2014-04-14 | [
[
"Herrera",
"Ramon",
""
],
[
"Olivares",
"Marco",
""
],
[
"Videla",
"Nelson",
""
]
] | We study a general form for the dissipative coefficient $\Gamma(T,\phi)=C_\phi\,T^{m}/\phi^{m-1}$ in the context of warm intermediate and logamediate inflationary universe models. We analyze these models in the weak and strong dissipative regimes. In the slow-roll approximation, we describe in great detail the characteristics of these models. In both regimes, we use recent data from the WMAP nine-year data and Planck data to constrain the parameters appearing in our models. |
gr-qc/0201032 | P. A. Letelier | Bruno Boisseau and Patricio S. Letelier | Relativistic Multipoles and the Advance of the Perihelia | 28 pages, 2 figures, to appear in GRG | Gen.Rel.Grav. 34 (2002) 1077-1096 | 10.1023/A:1016566005478 | null | gr-qc | null | In order to shed some light in the meaning of the relativistic multipolar
expansions we consider different static solutions of the axially symmetric
vacuum Einstein equations that in the non relativistic limit have same
Newtonian moments. The motion of test particles orbiting around different
deformed attraction centers with the same Newtonian limit is studied paying
special attention to the advance of the perihelion. We find discrepancies in
the fourth order of the dimensionless parameter (mass of the attraction
center)/(semilatus rectum). An evolution equation for the difference of the
radial coordinate due to the use of different general relativistic multipole
expansions is presented.
| [
{
"created": "Thu, 10 Jan 2002 13:14:42 GMT",
"version": "v1"
}
] | 2021-10-20 | [
[
"Boisseau",
"Bruno",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | In order to shed some light in the meaning of the relativistic multipolar expansions we consider different static solutions of the axially symmetric vacuum Einstein equations that in the non relativistic limit have same Newtonian moments. The motion of test particles orbiting around different deformed attraction centers with the same Newtonian limit is studied paying special attention to the advance of the perihelion. We find discrepancies in the fourth order of the dimensionless parameter (mass of the attraction center)/(semilatus rectum). An evolution equation for the difference of the radial coordinate due to the use of different general relativistic multipole expansions is presented. |
0802.1757 | Myungseok Yoon | Wontae Kim, Edwin J. Son, and Myungseok Yoon | Thermodynamic similarity between the noncommutative Schwarzschild black
hole and the Reissner-Nordstr\"om black hole | 10 pages, 6 figures | JHEP0804:042,2008 | 10.1088/1126-6708/2008/04/042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study thermodynamic quantities and examine the stability of a black hole
in a cavity inspired by the noncommutative geometry. It turns out that
thermodynamic behavior of the noncommutative black hole is analogous to that of
the Reissner-Nordstr\"om black hole in the near extremal limit. Moreover, we
identify the noncommutative parameter with the squared electric charge with
some constants.
| [
{
"created": "Wed, 13 Feb 2008 03:20:39 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Sep 2009 09:45:58 GMT",
"version": "v2"
}
] | 2009-09-11 | [
[
"Kim",
"Wontae",
""
],
[
"Son",
"Edwin J.",
""
],
[
"Yoon",
"Myungseok",
""
]
] | We study thermodynamic quantities and examine the stability of a black hole in a cavity inspired by the noncommutative geometry. It turns out that thermodynamic behavior of the noncommutative black hole is analogous to that of the Reissner-Nordstr\"om black hole in the near extremal limit. Moreover, we identify the noncommutative parameter with the squared electric charge with some constants. |
gr-qc/9506039 | Philip Tuckey | W. Drechsler and Philip A. Tuckey (MPI for Physics, Munich) | On quantum and parallel transport in a Hilbert bundle over spacetime | 25 pages, Plain TeX, harvmac/lanlmac | Class.Quant.Grav. 13 (1996) 611-632 | 10.1088/0264-9381/13/4/004 | MPI-PhT/95-37 | gr-qc | null | We study the Hilbert bundle description of stochastic quantum mechanics in
curved spacetime developed by Prugove\v{c}ki, which gives a powerful new
framework for exploring the quantum mechanical propagation of states in curved
spacetime. We concentrate on the quantum transport law in the bundle,
specifically on the information which can be obtained from the flat space
limit. We give a detailed proof that quantum transport coincides with parallel
transport in the bundle in this limit, confirming statements of Prugove\v{c}ki.
We furthermore show that the quantum-geometric propagator in curved spacetime
proposed by Prugove\v{c}ki, yielding a Feynman path integral-like formula
involving integrations over intermediate phase space variables, is Poincar\'e
gauge covariant (i.e.$\!$ is gauge invariant except for transformations at the
endpoints of the path) provided the integration measure is interpreted as a
``contact point measure'' in the soldered stochastic phase space bundle raised
over curved spacetime.
| [
{
"created": "Tue, 20 Jun 1995 12:38:17 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Jul 1995 14:44:24 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Sep 1995 16:01:06 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Drechsler",
"W.",
"",
"MPI for Physics, Munich"
],
[
"Tuckey",
"Philip A.",
"",
"MPI for Physics, Munich"
]
] | We study the Hilbert bundle description of stochastic quantum mechanics in curved spacetime developed by Prugove\v{c}ki, which gives a powerful new framework for exploring the quantum mechanical propagation of states in curved spacetime. We concentrate on the quantum transport law in the bundle, specifically on the information which can be obtained from the flat space limit. We give a detailed proof that quantum transport coincides with parallel transport in the bundle in this limit, confirming statements of Prugove\v{c}ki. We furthermore show that the quantum-geometric propagator in curved spacetime proposed by Prugove\v{c}ki, yielding a Feynman path integral-like formula involving integrations over intermediate phase space variables, is Poincar\'e gauge covariant (i.e.$\!$ is gauge invariant except for transformations at the endpoints of the path) provided the integration measure is interpreted as a ``contact point measure'' in the soldered stochastic phase space bundle raised over curved spacetime. |
1506.06054 | Moataz Emam | Jesse Chandler, Moataz H. Emam | Geodesic structure of five-dimensional non-asymptotically flat 2-branes | 14 pages, 14 figures | Physical Review D 91, 125024 (2015) | 10.1103/PhysRevD.91.125024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geodesics of a five dimensional non-asymptotically flat
dilatonic 2-brane. Although the metric's warp function diverges logarithmically
in the far field region of the transverse space, the curvature does not. The
brane has two naked singularities, the usual central singularity and a circular
singularity at the radius where the warp function vanishes. This creates two
causally disconnected regions of the transverse space. Using the methods of
energy conservation and effective potentials we study the null and timelike
orbital and radial geodesics in both regions and show that they exhibit
opposing energy requirements.
| [
{
"created": "Fri, 19 Jun 2015 15:35:32 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Chandler",
"Jesse",
""
],
[
"Emam",
"Moataz H.",
""
]
] | We study the geodesics of a five dimensional non-asymptotically flat dilatonic 2-brane. Although the metric's warp function diverges logarithmically in the far field region of the transverse space, the curvature does not. The brane has two naked singularities, the usual central singularity and a circular singularity at the radius where the warp function vanishes. This creates two causally disconnected regions of the transverse space. Using the methods of energy conservation and effective potentials we study the null and timelike orbital and radial geodesics in both regions and show that they exhibit opposing energy requirements. |
gr-qc/0502028 | Eric Poisson | Karl Martel and Eric Poisson | Gravitational perturbations of the Schwarzschild spacetime: A practical
covariant and gauge-invariant formalism | 21 pages | Phys.Rev. D71 (2005) 104003 | 10.1103/PhysRevD.71.104003 | null | gr-qc | null | We present a formalism to study the metric perturbations of the Schwarzschild
spacetime. The formalism is gauge invariant, and it is also covariant under
two-dimensional coordinate transformations that leave the angular coordinates
unchanged. The formalism is applied to the typical problem of calculating the
gravitational waves produced by material sources moving in the Schwarzschild
spacetime. We examine the radiation escaping to future null infinity as well as
the radiation crossing the event horizon. The waveforms, the energy radiated,
and the angular-momentum radiated can all be expressed in terms of two
gauge-invariant scalar functions that satisfy one-dimensional wave equations.
The first is the Zerilli-Moncrief function, which satisfies the Zerilli
equation, and which represents the even-parity sector of the perturbation. The
second is the Cunningham-Price-Moncrief function, which satisfies the
Regge-Wheeler equation, and which represents the odd-parity sector of the
perturbation. The covariant forms of these wave equations are presented here,
complete with covariant source terms that are derived from the stress-energy
tensor of the matter responsible for the perturbation. Our presentation of the
formalism is concluded with a separate examination of the monopole and dipole
components of the metric perturbation.
| [
{
"created": "Tue, 8 Feb 2005 16:58:57 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Martel",
"Karl",
""
],
[
"Poisson",
"Eric",
""
]
] | We present a formalism to study the metric perturbations of the Schwarzschild spacetime. The formalism is gauge invariant, and it is also covariant under two-dimensional coordinate transformations that leave the angular coordinates unchanged. The formalism is applied to the typical problem of calculating the gravitational waves produced by material sources moving in the Schwarzschild spacetime. We examine the radiation escaping to future null infinity as well as the radiation crossing the event horizon. The waveforms, the energy radiated, and the angular-momentum radiated can all be expressed in terms of two gauge-invariant scalar functions that satisfy one-dimensional wave equations. The first is the Zerilli-Moncrief function, which satisfies the Zerilli equation, and which represents the even-parity sector of the perturbation. The second is the Cunningham-Price-Moncrief function, which satisfies the Regge-Wheeler equation, and which represents the odd-parity sector of the perturbation. The covariant forms of these wave equations are presented here, complete with covariant source terms that are derived from the stress-energy tensor of the matter responsible for the perturbation. Our presentation of the formalism is concluded with a separate examination of the monopole and dipole components of the metric perturbation. |
2309.12175 | Hryhorii Ovcharenko | H.V.Ovcharenko and O.B.Zaslavskii | Dynamics of redshift/blueshift during free fall under the Schwarzschild
horizon | 30 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a free-falling observer who crosses the event horizon in the
Schwarzschild background. In the course of this fall, he/she can receive
signals from an object (like a star surface) that emits radiation. We study how
the frequency received by an observer changes depending on the proper time on
his/her trajectory. The scenarios are classified depending on whether the
frequency is infinite, finite or zero near the singularity and the horizon.
This depends crucially on the angular momenta of an observer and a photon. In
this work we consider also emission process, and, as we show, conditions of
emission strongly influence parameters of a photon, and thus received
frequency. As one of our main results, we present numerical calculations
showing evolution of the received frequency during the process of diving into a
black hole, depending on parameters of an observer and emitter. We also analyze
how a falling observer will see a night sky as he/she approaches the
singularity. We show that there appear several blind zones, which were not
analyzed previously.
| [
{
"created": "Thu, 21 Sep 2023 15:33:18 GMT",
"version": "v1"
}
] | 2023-09-22 | [
[
"Ovcharenko",
"H. V.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | We consider a free-falling observer who crosses the event horizon in the Schwarzschild background. In the course of this fall, he/she can receive signals from an object (like a star surface) that emits radiation. We study how the frequency received by an observer changes depending on the proper time on his/her trajectory. The scenarios are classified depending on whether the frequency is infinite, finite or zero near the singularity and the horizon. This depends crucially on the angular momenta of an observer and a photon. In this work we consider also emission process, and, as we show, conditions of emission strongly influence parameters of a photon, and thus received frequency. As one of our main results, we present numerical calculations showing evolution of the received frequency during the process of diving into a black hole, depending on parameters of an observer and emitter. We also analyze how a falling observer will see a night sky as he/she approaches the singularity. We show that there appear several blind zones, which were not analyzed previously. |
2303.11094 | William Barker Dr | W. E. V. Barker and M. P. Hobson and A. N. Lasenby | Does gravitational confinement sustain flat galactic rotation curves
without dark matter? | 33 pages, 19 figures | null | null | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | The short answer is $\textit{probably no}$. Specifically, this paper
considers a recent body of work which suggests that general relativity requires
neither the support of dark matter halos, nor unconventional baryonic profiles,
nor any infrared modification, to be consistent after all with the anomalously
rapid orbits observed in many galactic discs. In particular, the
gravitoelectric flux is alleged to collapse nonlinearly into regions of
enhanced force, in an analogue of the colour-confining chromoelectric flux tube
model which has yet to be captured by conventional post-Newtonian methods.
However, we show that the scalar gravity model underpinning this proposal is
wholly inconsistent with the nonlinear Einstein equations, which themselves
appear to prohibit the linear confinement-type potentials which could indicate
a disordered gravitational phase. Our findings challenge the fidelity of the
previous Euclidean lattice analyses. We confirm by direct calculation using a
number of perturbation schemes and gauges that the next-to-leading order
gravitoelectric correction to the rotation curve of a reasonable baryonic
profile would be imperceptible. The `gravitoelectric flux collapse' programme
was also supported by using intragalactic lensing near a specific galactic
baryon profile as a field strength heuristic. We recalculate this lensing
effect, and conclude that it has been overstated by three orders of magnitude.
As a by-product, our analysis suggests fresh approaches to (i) the fluid ball
conjecture and (ii) gravitational energy localisation, both to be pursued in
future work. In summary, whilst it may be interesting to consider the
possibility of confinement-type effects in gravity, we may at least conclude
here that confinement-type effects $\textit{cannot play any significant part}$
in explaining flat or rising galactic rotation curves without dark matter
halos.
| [
{
"created": "Mon, 20 Mar 2023 13:29:29 GMT",
"version": "v1"
}
] | 2023-03-21 | [
[
"Barker",
"W. E. V.",
""
],
[
"Hobson",
"M. P.",
""
],
[
"Lasenby",
"A. N.",
""
]
] | The short answer is $\textit{probably no}$. Specifically, this paper considers a recent body of work which suggests that general relativity requires neither the support of dark matter halos, nor unconventional baryonic profiles, nor any infrared modification, to be consistent after all with the anomalously rapid orbits observed in many galactic discs. In particular, the gravitoelectric flux is alleged to collapse nonlinearly into regions of enhanced force, in an analogue of the colour-confining chromoelectric flux tube model which has yet to be captured by conventional post-Newtonian methods. However, we show that the scalar gravity model underpinning this proposal is wholly inconsistent with the nonlinear Einstein equations, which themselves appear to prohibit the linear confinement-type potentials which could indicate a disordered gravitational phase. Our findings challenge the fidelity of the previous Euclidean lattice analyses. We confirm by direct calculation using a number of perturbation schemes and gauges that the next-to-leading order gravitoelectric correction to the rotation curve of a reasonable baryonic profile would be imperceptible. The `gravitoelectric flux collapse' programme was also supported by using intragalactic lensing near a specific galactic baryon profile as a field strength heuristic. We recalculate this lensing effect, and conclude that it has been overstated by three orders of magnitude. As a by-product, our analysis suggests fresh approaches to (i) the fluid ball conjecture and (ii) gravitational energy localisation, both to be pursued in future work. In summary, whilst it may be interesting to consider the possibility of confinement-type effects in gravity, we may at least conclude here that confinement-type effects $\textit{cannot play any significant part}$ in explaining flat or rising galactic rotation curves without dark matter halos. |
2305.15733 | Haojie Lin | Hao-Jie Lin, Tao Zhu, Shao-Jun Zhang, and Anzhong Wang | Black hole scalarizations induced by parity violations | 9 pages, 3 figures, 1 table | Phys. Rev. D 108, 044005 (2023) | 10.1103/PhysRevD.108.044005 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It is well-known that parity symmetry is broken in the weak interaction but
conserved for Einstein's general relativity and Maxwell's electromagnetic
theory. Nevertheless, parity symmetry could also be violated in the
gravitational/electromagnetic sectors if a fundamental scalar field couples to
the parity-violating gravitational/electromagnetic curvature terms. Such
parity-violating terms, which flip signs under reversed spatial directions, can
inevitably lead to a negative effective mass squared for the scalar field
perturbations near nonspherically symmetric black holes and thus are expected
to trigger tachyonic instability. As illustrative examples, we show that the
scalar field coupled to gravitational/electromagnetic Chern-Simons terms near a
Kerr-Newmann spacetime can develop tachyonic instabilities, leading to
equilibrium scalar field configurations in certain parameter regions of black
holes. This instability, which is an indication of the black hole scalarization
process, can occur in a broad class of nonspherically symmetric black holes and
parity-violating theories.
| [
{
"created": "Thu, 25 May 2023 05:34:11 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jul 2023 09:17:11 GMT",
"version": "v2"
}
] | 2024-04-17 | [
[
"Lin",
"Hao-Jie",
""
],
[
"Zhu",
"Tao",
""
],
[
"Zhang",
"Shao-Jun",
""
],
[
"Wang",
"Anzhong",
""
]
] | It is well-known that parity symmetry is broken in the weak interaction but conserved for Einstein's general relativity and Maxwell's electromagnetic theory. Nevertheless, parity symmetry could also be violated in the gravitational/electromagnetic sectors if a fundamental scalar field couples to the parity-violating gravitational/electromagnetic curvature terms. Such parity-violating terms, which flip signs under reversed spatial directions, can inevitably lead to a negative effective mass squared for the scalar field perturbations near nonspherically symmetric black holes and thus are expected to trigger tachyonic instability. As illustrative examples, we show that the scalar field coupled to gravitational/electromagnetic Chern-Simons terms near a Kerr-Newmann spacetime can develop tachyonic instabilities, leading to equilibrium scalar field configurations in certain parameter regions of black holes. This instability, which is an indication of the black hole scalarization process, can occur in a broad class of nonspherically symmetric black holes and parity-violating theories. |
gr-qc/9910102 | Allan Widom | T. Sakai, A. Widom, Y.N. Srivastava | Entropy Production and Cosmological Inflation | 5 Pages, ReVTeX, 1 figure | null | null | gr-100 | gr-qc | null | The notion of inflation (past or present) in standard cosmological models is
shown to be a consequence of a sufficiently high second law entropy production
from the internal heating of the universal expansion. The longitudinal viscous
internal heating of matter requires neither ``inflaton'' fields nor
``quintessence'' fields which in theory may induce a cosmological term into the
Einstein equations. The purely thermodynamic principles required to understand
inflation within the context of the standard general relativity equations will
be discussed in detail.
| [
{
"created": "Thu, 28 Oct 1999 00:24:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sakai",
"T.",
""
],
[
"Widom",
"A.",
""
],
[
"Srivastava",
"Y. N.",
""
]
] | The notion of inflation (past or present) in standard cosmological models is shown to be a consequence of a sufficiently high second law entropy production from the internal heating of the universal expansion. The longitudinal viscous internal heating of matter requires neither ``inflaton'' fields nor ``quintessence'' fields which in theory may induce a cosmological term into the Einstein equations. The purely thermodynamic principles required to understand inflation within the context of the standard general relativity equations will be discussed in detail. |
1707.04169 | Roger Penrose | Roger Penrose | Correlated "noise" in LIGO gravitational wave signals: an implication of
Conformal Cyclic Cosmology | 8 pages | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been reported by Cresswell et al. [1] that correlations in
the noise surrounding the observed gravitational wave signals, GW150194,
GW151226, and GW170194 were found by the two LIGO detectors in Hanford and
Livingston with the same time delay as the signals themselves. This raised some
issues about the statistical reliability of the signals themselves, which led
to much discussion, the current view appearing to support the contention that
there is something unexplained that may be of genuine astrophysical interest
[2]. In this note, it is pointed out that a resolution of this puzzle may be
found in a proposal very recently put forward by the author [3], see also [4],
that what seems to be spuriously generated noise may in fact be gravitational
events caused by the decay of dark-matter particles (erebons) of mass around
10^-5g, the existence of such events being a clear implication of the
cosmological scheme of conformal cyclic cosmology, or CCC [5], [6]. A brief
outline of the salient points of CCC is provided here, especially with regard
to its prediction of erebons and their impulsive gravitational signals.
| [
{
"created": "Wed, 12 Jul 2017 15:53:38 GMT",
"version": "v1"
}
] | 2017-07-14 | [
[
"Penrose",
"Roger",
""
]
] | It has recently been reported by Cresswell et al. [1] that correlations in the noise surrounding the observed gravitational wave signals, GW150194, GW151226, and GW170194 were found by the two LIGO detectors in Hanford and Livingston with the same time delay as the signals themselves. This raised some issues about the statistical reliability of the signals themselves, which led to much discussion, the current view appearing to support the contention that there is something unexplained that may be of genuine astrophysical interest [2]. In this note, it is pointed out that a resolution of this puzzle may be found in a proposal very recently put forward by the author [3], see also [4], that what seems to be spuriously generated noise may in fact be gravitational events caused by the decay of dark-matter particles (erebons) of mass around 10^-5g, the existence of such events being a clear implication of the cosmological scheme of conformal cyclic cosmology, or CCC [5], [6]. A brief outline of the salient points of CCC is provided here, especially with regard to its prediction of erebons and their impulsive gravitational signals. |
1904.06727 | Kirill Bronnikov | S.V. Bolokhov, K.A. Bronnikov and M.V. Skvortsova | Rotating cylinders with anisotropic fluids in general relativity | 10 two-column pages | Grav. Cosmol. 25, 122-130 (2019) | 10.1134/S020228931902004X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider anisotropic fluids with directional pressures $p_i = w_i \rho$
($\rho$ is the density, $w_i = $const, $i = 1,2,3$) as sources of gravity in
stationary cylindrically symmetric space-times. We describe a general way of
obtaining exact solutions with such sources, where the main features are
splitting of the Ricci tensor into static and rotational parts and using the
harmonic radial coordinate. Depending on the values of $w_i$, it appears
possible to obtain general or special solutions to the Einstein equations, thus
recovering some known solutions and finding new ones. Three particular examples
of exact solutions are briefly described: with a stiff isotropic perfect fluid
($p = \rho$), with a distribution of cosmic strings of azimuthal direction
(i.e., forming circles around the $z$ axis), and with a stationary combination
of two opposite radiation flows along the $z$ axis.
| [
{
"created": "Sun, 14 Apr 2019 17:13:02 GMT",
"version": "v1"
}
] | 2019-06-19 | [
[
"Bolokhov",
"S. V.",
""
],
[
"Bronnikov",
"K. A.",
""
],
[
"Skvortsova",
"M. V.",
""
]
] | We consider anisotropic fluids with directional pressures $p_i = w_i \rho$ ($\rho$ is the density, $w_i = $const, $i = 1,2,3$) as sources of gravity in stationary cylindrically symmetric space-times. We describe a general way of obtaining exact solutions with such sources, where the main features are splitting of the Ricci tensor into static and rotational parts and using the harmonic radial coordinate. Depending on the values of $w_i$, it appears possible to obtain general or special solutions to the Einstein equations, thus recovering some known solutions and finding new ones. Three particular examples of exact solutions are briefly described: with a stiff isotropic perfect fluid ($p = \rho$), with a distribution of cosmic strings of azimuthal direction (i.e., forming circles around the $z$ axis), and with a stationary combination of two opposite radiation flows along the $z$ axis. |
gr-qc/9302008 | null | P.S.Joshi and I.H.Dwivedi | The Structure of Naked Singularity in Self-similar Gravitational
Collapse II | 4 pages, TIFR preprint October 1992 | null | 10.1007/BF00739581 | null | gr-qc | null | Generalizing the results of Joshi and Dwivedi in Commun.Math.Phys. 146, p.333
(1992), it is pointed out that strong curvature naked singularities could occur
in the self-similar gravitational collapse of any form of matter satisfying the
weak energy condition for the positivity of mass-energy density.
| [
{
"created": "Tue, 9 Feb 1993 10:14:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Joshi",
"P. S.",
""
],
[
"Dwivedi",
"I. H.",
""
]
] | Generalizing the results of Joshi and Dwivedi in Commun.Math.Phys. 146, p.333 (1992), it is pointed out that strong curvature naked singularities could occur in the self-similar gravitational collapse of any form of matter satisfying the weak energy condition for the positivity of mass-energy density. |
gr-qc/9403034 | Hans-Juergen Matschull | Hans-Juergen Matschull | About Loop States in Supergravity | LaTeX, 20 pages, DESY-94-037 | Class.Quant.Grav.11:2395-2410,1994 | 10.1088/0264-9381/11/10/002 | null | gr-qc | null | The Wilson loop functionals in terms of Ashtekar's variables were the first
(formal) solutions to the quantized hamiltonian constraint of canonical
gravity. Here it is shown that the same functionals also solve the supergravity
constraints and some evidence is presented that they are artificially generated
by multiplying the constraints by the metric determinant, which has become a
widely accepted procedure. Using the same method in 2+1 dimensional gravity and
supergravity leads to wrong results, e.g.~2+1 gravity is no longer a purely
topological theory. As another feature of the densitized constraints it turns
out that the classical theory desribed by them is not invariant under space
time diffeomorphisms.
| [
{
"created": "Fri, 18 Mar 1994 11:17:40 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Matschull",
"Hans-Juergen",
""
]
] | The Wilson loop functionals in terms of Ashtekar's variables were the first (formal) solutions to the quantized hamiltonian constraint of canonical gravity. Here it is shown that the same functionals also solve the supergravity constraints and some evidence is presented that they are artificially generated by multiplying the constraints by the metric determinant, which has become a widely accepted procedure. Using the same method in 2+1 dimensional gravity and supergravity leads to wrong results, e.g.~2+1 gravity is no longer a purely topological theory. As another feature of the densitized constraints it turns out that the classical theory desribed by them is not invariant under space time diffeomorphisms. |
0704.1289 | M. D. Maia | M. D. Maia, Nildsen Silva and M.C.B. Fernandes | Brane-world Quantum Gravity | 14 pages, no figures, JHEP format, to appear in JHEP April 2007 | JHEP 0704:047,2007 | 10.1088/1126-6708/2007/04/047 | null | gr-qc | null | The Arnowitt-Deser-Misner canonical formulation of general relativity is
extended to the covariant brane-world theory in arbitrary dimensions. The
exclusive probing of the extra dimensions makes a substantial difference,
allowing for the construction of a non-constrained canonical theory. The
quantum states of the brane-world geometry are defined by the
Tomonaga-Schwinger equation, whose integrability conditions are determined by
the classical perturbations of submanifolds contained in the Nash's
differentiable embedding theorem. In principle, quantum brane-world theory can
be tested by current experiments in astrophysics and by near future laboratory
experiments at Tev energy. The implications to the black-hole information loss
problem, to the accelerating cosmology, and to a quantum mathematical theory of
four-sub manifolds are briefly commented.
| [
{
"created": "Tue, 10 Apr 2007 18:26:09 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Maia",
"M. D.",
""
],
[
"Silva",
"Nildsen",
""
],
[
"Fernandes",
"M. C. B.",
""
]
] | The Arnowitt-Deser-Misner canonical formulation of general relativity is extended to the covariant brane-world theory in arbitrary dimensions. The exclusive probing of the extra dimensions makes a substantial difference, allowing for the construction of a non-constrained canonical theory. The quantum states of the brane-world geometry are defined by the Tomonaga-Schwinger equation, whose integrability conditions are determined by the classical perturbations of submanifolds contained in the Nash's differentiable embedding theorem. In principle, quantum brane-world theory can be tested by current experiments in astrophysics and by near future laboratory experiments at Tev energy. The implications to the black-hole information loss problem, to the accelerating cosmology, and to a quantum mathematical theory of four-sub manifolds are briefly commented. |
gr-qc/0303048 | Guendel Eduardo | E.I.Guendelman (Ben Gurion University) | Conformally Invariant Braneworld and the Cosmological Constant | 10 pages, latex, no figures, few typos corrected | Phys.Lett. B580 (2004) 87-92 | 10.1016/j.physletb.2003.09.102 | BGU-Phys. 67/2003 | gr-qc | null | A six dimensional braneworld scenario based on a model describing the
interaction of gravity, gauge fields and 3+1 branes in a conformally invariant
way is described. The action of the model is defined using a measure of
integration built of degrees of freedom independent of the metric. There is no
need to fine tune any bulk cosmological constant or the tension of the two (in
the scenario described here) parallel branes to obtain zero cosmological
constant, the only solutions are those with zero 4-D cosmological constant. The
two extra dimensions are compactified in a "football" fashion and the branes
lie on the two opposite poles of the compact "football-shaped" sphere.
| [
{
"created": "Wed, 12 Mar 2003 10:08:24 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Mar 2003 13:04:57 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Guendelman",
"E. I.",
"",
"Ben Gurion University"
]
] | A six dimensional braneworld scenario based on a model describing the interaction of gravity, gauge fields and 3+1 branes in a conformally invariant way is described. The action of the model is defined using a measure of integration built of degrees of freedom independent of the metric. There is no need to fine tune any bulk cosmological constant or the tension of the two (in the scenario described here) parallel branes to obtain zero cosmological constant, the only solutions are those with zero 4-D cosmological constant. The two extra dimensions are compactified in a "football" fashion and the branes lie on the two opposite poles of the compact "football-shaped" sphere. |
gr-qc/9506029 | null | Kirill V.Krasnov | Quantum Loop Representation for Fermions coupled to Einstein-Maxwell
field | 28 pages, REVTeX 3.0, 15 uuencoded ps-figures. The construction of
the representation has been changed so that the representation space became
irreducible. One part is removed because it developed into a separate paper;
some corrections added | Phys. Rev. D 53, 1874 (1996) | 10.1103/PhysRevD.53.1874 | null | gr-qc | null | Quantization of the system comprising gravitational, fermionic and
electromagnetic fields is developed in the loop representation. As a result we
obtain a natural unified quantum theory. Gravitational field is treated in the
framework of Ashtekar formalism; fermions are described by two Grassmann-valued
fields. We define a $C^{*}$-algebra of configurational variables whose
generators are associated with oriented loops and curves; ``open'' states --
curves -- are necessary to embrace the fermionic degrees of freedom. Quantum
representation space is constructed as a space of cylindrical functionals on
the spectrum of this $C^{*}$-algebra. Choosing the basis of ``loop'' states we
describe the representation space as the space of oriented loops and curves;
then configurational and momentum loop variables become in this basis the
operators of creation and annihilation of loops and curves. The important
difference of the representation constructed from the loop representation of
pure gravity is that the momentum loop operators act in our case simply by
joining loops in the only compatible with their orientaiton way, while in the
case of pure gravity this action is more complicated.
| [
{
"created": "Fri, 16 Jun 1995 16:07:08 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Sep 1995 01:23:32 GMT",
"version": "v2"
}
] | 2016-08-24 | [
[
"Krasnov",
"Kirill V.",
""
]
] | Quantization of the system comprising gravitational, fermionic and electromagnetic fields is developed in the loop representation. As a result we obtain a natural unified quantum theory. Gravitational field is treated in the framework of Ashtekar formalism; fermions are described by two Grassmann-valued fields. We define a $C^{*}$-algebra of configurational variables whose generators are associated with oriented loops and curves; ``open'' states -- curves -- are necessary to embrace the fermionic degrees of freedom. Quantum representation space is constructed as a space of cylindrical functionals on the spectrum of this $C^{*}$-algebra. Choosing the basis of ``loop'' states we describe the representation space as the space of oriented loops and curves; then configurational and momentum loop variables become in this basis the operators of creation and annihilation of loops and curves. The important difference of the representation constructed from the loop representation of pure gravity is that the momentum loop operators act in our case simply by joining loops in the only compatible with their orientaiton way, while in the case of pure gravity this action is more complicated. |
2211.07991 | Mouhssine Koussour | M. Koussour, S. H. Shekh, M. Bennai and T. Ouali | Bulk viscous fluid in extended symmetric teleparallel gravity | CJPHY accepted version | Chinese Journal of Physics (2022) | 10.1016/j.cjph.2022.11.013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the existence of bulk viscous FLRW cosmological
models in a recently proposed extended symmetric teleparallel gravity or
$f\left( Q,T\right) $ gravity in which $Q$ is the non-metricity and $T$ is the
trace of the energy-momentum tensor. We consider a simple coupling between
matter and non-metricity, specifically, $f\left( Q,T\right) =\alpha
Q^{m+1}+\lambda T$ and $f\left( Q,T\right) =\alpha Q+\lambda T$ where $\alpha
$, $\lambda $ and $m$ are free model parameters. The exact cosmological
solutions are found by assuming the scale factor in the form of the hybrid
expansion law. This type of relation generates a time-varying deceleration
parameter with the transition of the Universe from the early decelerating phase
to the present accelerating phase. In the presence of viscous fluid, we analyze
some cosmological parameters of our cosmological model such as the energy
density, bulk viscous pressure, bulk viscous coefficient, equation of state
parameter, and energy conditions. Finally, we conclude our $f\left( Q,T\right)
$\ cosmological models agree with the recent astronomical observations.
| [
{
"created": "Tue, 15 Nov 2022 09:00:44 GMT",
"version": "v1"
}
] | 2022-12-01 | [
[
"Koussour",
"M.",
""
],
[
"Shekh",
"S. H.",
""
],
[
"Bennai",
"M.",
""
],
[
"Ouali",
"T.",
""
]
] | In this paper, we investigate the existence of bulk viscous FLRW cosmological models in a recently proposed extended symmetric teleparallel gravity or $f\left( Q,T\right) $ gravity in which $Q$ is the non-metricity and $T$ is the trace of the energy-momentum tensor. We consider a simple coupling between matter and non-metricity, specifically, $f\left( Q,T\right) =\alpha Q^{m+1}+\lambda T$ and $f\left( Q,T\right) =\alpha Q+\lambda T$ where $\alpha $, $\lambda $ and $m$ are free model parameters. The exact cosmological solutions are found by assuming the scale factor in the form of the hybrid expansion law. This type of relation generates a time-varying deceleration parameter with the transition of the Universe from the early decelerating phase to the present accelerating phase. In the presence of viscous fluid, we analyze some cosmological parameters of our cosmological model such as the energy density, bulk viscous pressure, bulk viscous coefficient, equation of state parameter, and energy conditions. Finally, we conclude our $f\left( Q,T\right) $\ cosmological models agree with the recent astronomical observations. |
gr-qc/9710004 | Enzo Leguizamon | Mirta S. Iriondo, Enzo O. Leguizam\'on and Oscar A. Reula | Einstein's equations in Ashtekar's variables constitute a symmetric
hyperbolic system | 4 pages, revteX | Phys.Rev.Lett. 79 (1997) 4732-4735 | 10.1103/PhysRevLett.79.4732 | null | gr-qc | null | We show that the 3+1 vacuum Einstein field equations in Ashtekar's variables
constitutes a first order symmetric hyperbolic system for arbitrary but fixed
lapse and shift fields, by suitable adding to the system terms proportional to
the constraint equations.
| [
{
"created": "Wed, 1 Oct 1997 17:31:45 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Iriondo",
"Mirta S.",
""
],
[
"Leguizamón",
"Enzo O.",
""
],
[
"Reula",
"Oscar A.",
""
]
] | We show that the 3+1 vacuum Einstein field equations in Ashtekar's variables constitutes a first order symmetric hyperbolic system for arbitrary but fixed lapse and shift fields, by suitable adding to the system terms proportional to the constraint equations. |
gr-qc/0309134 | Paul S. Wesson | Paul S. Wesson | Space-Time Uncertainty from Higher-Dimensional Determinism (or: How
Heisenberg was right in 4D because Einstein was right in 5D) | Accepted, J. Gen. Rel. and Grav., February 2004 | Gen.Rel.Grav. 36 (2004) 451-457 | 10.1023/B:GERG.0000010504.65118.fd | null | gr-qc | null | Heisenberg's uncertainty relation is commonly regarded as defining a level of
unpredictability that is fundamentally incompatible with the deterministic laws
embodied in classical field theories such as Einstein's general relativity. We
here show that this is not necessarily the case. Using 5D as an example of
dimensionally-extended relativity, we employ a novel metric to derive the
standard quantum rule for the action and a form of Heisenberg's relation that
applies to real and virtual particles. The philosophical implications of these
technical results are somewhat profound.
| [
{
"created": "Sun, 28 Sep 2003 14:54:31 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Wesson",
"Paul S.",
""
]
] | Heisenberg's uncertainty relation is commonly regarded as defining a level of unpredictability that is fundamentally incompatible with the deterministic laws embodied in classical field theories such as Einstein's general relativity. We here show that this is not necessarily the case. Using 5D as an example of dimensionally-extended relativity, we employ a novel metric to derive the standard quantum rule for the action and a form of Heisenberg's relation that applies to real and virtual particles. The philosophical implications of these technical results are somewhat profound. |
gr-qc/0510035 | Peter D'Eath | A.N.St.J.Farley and P.D.D'Eath | Spin-2 Amplitudes in Black-Hole Evaporation | null | null | 10.1088/0264-9381/22/13/015 | null | gr-qc | null | Quantum amplitudes for $s=2$ gravitational-wave perturbations of
Einstein/scalar collapse to a black hole are treated by analogy with $s=1$
Maxwell perturbations. The spin-2 perturbations split into parts with odd and
even parity. We use the Regge-Wheeler gauge; at a certain point we make a gauge
transformation to an asymptotically-flat gauge, such that the metric
perturbations have the expected falloff behaviour at large radii. By analogy
with $s=1$, for $s=2$ natural 'coordinate' variables are given by the magnetic
part $H_{ij} (i,j=1,2,3)$ of the Weyl tensor, which can be taken as boundary
data on a final space-like hypersurface $\Sigma_F$. For simplicity, we take the
data on the initial surface $\Sigma_I$ to be exactly spherically-symmetric. The
(large) Lorentzian proper-time interval between $\Sigma_I$ and $\Sigma_F$,
measured at spatial infinity, is denoted by $T$. We follow Feynman's
$+i\epsilon$ prescription and rotate $T$ into the complex: $T\to{\mid}T{\mid}
\exp(-i\theta)$, for $0<\theta\leq\pi/2$. The corresponding complexified {\it
classical} boundary-value problem is expected to be well-posed. The Lorentzian
quantum amplitude is recovered by taking the limit as $\theta\to 0_+$. For
boundary data well below the Planck scale, and for a locally supersymmetric
theory, this involves only the semi-classical amplitude $\exp(iS^{(2)}_{\rm
class}$, where $S^{(2)}_{\rm class}$ denotes the second-variation classical
action. The relations between the $s=1$ and $s=2$ natural boundary data,
involving supersymmetry, are investigated using 2-component spinor language in
terms of the Maxwell field strength $\phi_{AB}=\phi_{(AB)}$ and the Weyl spinor
$\Psi_{ABCD}=\Psi_{(ABCD)}$.
| [
{
"created": "Sat, 8 Oct 2005 10:09:54 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Farley",
"A. N. St. J.",
""
],
[
"D'Eath",
"P. D.",
""
]
] | Quantum amplitudes for $s=2$ gravitational-wave perturbations of Einstein/scalar collapse to a black hole are treated by analogy with $s=1$ Maxwell perturbations. The spin-2 perturbations split into parts with odd and even parity. We use the Regge-Wheeler gauge; at a certain point we make a gauge transformation to an asymptotically-flat gauge, such that the metric perturbations have the expected falloff behaviour at large radii. By analogy with $s=1$, for $s=2$ natural 'coordinate' variables are given by the magnetic part $H_{ij} (i,j=1,2,3)$ of the Weyl tensor, which can be taken as boundary data on a final space-like hypersurface $\Sigma_F$. For simplicity, we take the data on the initial surface $\Sigma_I$ to be exactly spherically-symmetric. The (large) Lorentzian proper-time interval between $\Sigma_I$ and $\Sigma_F$, measured at spatial infinity, is denoted by $T$. We follow Feynman's $+i\epsilon$ prescription and rotate $T$ into the complex: $T\to{\mid}T{\mid} \exp(-i\theta)$, for $0<\theta\leq\pi/2$. The corresponding complexified {\it classical} boundary-value problem is expected to be well-posed. The Lorentzian quantum amplitude is recovered by taking the limit as $\theta\to 0_+$. For boundary data well below the Planck scale, and for a locally supersymmetric theory, this involves only the semi-classical amplitude $\exp(iS^{(2)}_{\rm class}$, where $S^{(2)}_{\rm class}$ denotes the second-variation classical action. The relations between the $s=1$ and $s=2$ natural boundary data, involving supersymmetry, are investigated using 2-component spinor language in terms of the Maxwell field strength $\phi_{AB}=\phi_{(AB)}$ and the Weyl spinor $\Psi_{ABCD}=\Psi_{(ABCD)}$. |
2310.14653 | De-Cheng Zou | Bo Liu, Rui-Hong Yue, De-Cheng Zou, Lina Zhang, Zhan-Ying Yang and
Qiyuan Pan | Black holes in massive Einstein-dilaton gravity | 23 pages, 12 figures | Phys.Rev.D.109, 064013(2024) | 10.1103/PhysRevD.109.064013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we focus on massive Einstein-dilaton gravity including the
coupling of dilaton scalar field to massive graviton terms, and then derive
static and spherically symmetric solutions of dilatonic black holes in four
dimensional spacetime. We find that the dilatonic black hole could possess two
horizons (event and cosmological), extreme (Nariai) and naked singularity for
the suitably fixed parameters. In addition, we investigate thermodynamic
properties of these dilatonic black holes, and check the corresponding first
law of black hole thermodynamics. Extending to the massive Einstein-dilaton
gravity in high dimensions, we further obtain the dilatonic black hole
solutions in $(d+1)$ dimensional spacetime.
| [
{
"created": "Mon, 23 Oct 2023 07:48:41 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 01:19:37 GMT",
"version": "v2"
}
] | 2024-03-07 | [
[
"Liu",
"Bo",
""
],
[
"Yue",
"Rui-Hong",
""
],
[
"Zou",
"De-Cheng",
""
],
[
"Zhang",
"Lina",
""
],
[
"Yang",
"Zhan-Ying",
""
],
[
"Pan",
"Qiyuan",
""
]
] | In this paper, we focus on massive Einstein-dilaton gravity including the coupling of dilaton scalar field to massive graviton terms, and then derive static and spherically symmetric solutions of dilatonic black holes in four dimensional spacetime. We find that the dilatonic black hole could possess two horizons (event and cosmological), extreme (Nariai) and naked singularity for the suitably fixed parameters. In addition, we investigate thermodynamic properties of these dilatonic black holes, and check the corresponding first law of black hole thermodynamics. Extending to the massive Einstein-dilaton gravity in high dimensions, we further obtain the dilatonic black hole solutions in $(d+1)$ dimensional spacetime. |
2306.03599 | Xiongjun Fang | Wentao Liu, Xiongjun Fang, Jiliang Jing, Jieci Wang | Gravito-electromagnetic perturbations of MOG black holes with a
cosmological constant: Quasinormal modes and Ringdown waveforms | 18pages, 6 figures | JCAP 11 (2023) 057 | 10.1088/1475-7516/2023/11/057 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this paper, we present a black hole solution with a cosmological constant
in the Scalar-Tensor-Vector Modified Gravity (MOG) theory, where the strength
of the gravitational constant is determined by $G = G_\text{N}(1+\alpha)$. We
derive the master equations for gravito-electromagnetic perturbations and
numerically solve for the Quasinormal Mode (QNM) spectrum and the ringdown
waveforms. Our research results show that increasing the MOG parameter $\alpha$
leads to a decrease in both the real and imaginary parts of the QNM frequencies
for electromagnetic and gravitational modes. Similarly, increasing the
cosmological constant $\Lambda$ also results in a decrease in both the real and
imaginary parts of the QNM frequencies for these modes. These trends are
observed when compared to standard Schwarzschild-de Sitter (S-dS) or MOG black
holes, respectively. Meanwhile, the result indicates that in the MOG-de Sitter
spacetime, the frequencies for electromagnetic and gravitational modes display
isospectrality, and exhibit the same ringdown waveforms. Our findings have
implications for the ringdown phase of mergers involving massive compact
objects, which is of particular relevance given the recent detections of
gravitational waves by LIGO.
| [
{
"created": "Tue, 6 Jun 2023 11:40:39 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jun 2023 13:19:50 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Jun 2023 14:53:46 GMT",
"version": "v3"
},
{
"created": "Wed, 11 Oct 2023 02:56:43 GMT",
"version": "v4"
}
] | 2024-02-22 | [
[
"Liu",
"Wentao",
""
],
[
"Fang",
"Xiongjun",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Wang",
"Jieci",
""
]
] | In this paper, we present a black hole solution with a cosmological constant in the Scalar-Tensor-Vector Modified Gravity (MOG) theory, where the strength of the gravitational constant is determined by $G = G_\text{N}(1+\alpha)$. We derive the master equations for gravito-electromagnetic perturbations and numerically solve for the Quasinormal Mode (QNM) spectrum and the ringdown waveforms. Our research results show that increasing the MOG parameter $\alpha$ leads to a decrease in both the real and imaginary parts of the QNM frequencies for electromagnetic and gravitational modes. Similarly, increasing the cosmological constant $\Lambda$ also results in a decrease in both the real and imaginary parts of the QNM frequencies for these modes. These trends are observed when compared to standard Schwarzschild-de Sitter (S-dS) or MOG black holes, respectively. Meanwhile, the result indicates that in the MOG-de Sitter spacetime, the frequencies for electromagnetic and gravitational modes display isospectrality, and exhibit the same ringdown waveforms. Our findings have implications for the ringdown phase of mergers involving massive compact objects, which is of particular relevance given the recent detections of gravitational waves by LIGO. |
2305.09706 | Manuel Rodrigues | Ednaldo L. B. Junior, Manuel E. Rodrigues, Henrique A. Vieira | Is it possible to distinguish between different black hole solutions
using the Shapiro time delay? | null | Eur. Phys. J. C (2023) 83:409 | 10.1140/epjc/s10052-023-11520-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we propose to use Shapiro time delay as a tool to distinguish
between different black hole solutions. We calculate the analytic Shapiro time,
using first-order expansions, for four solutions. They are Schwarzschild,
Reissner-Nordstr\"o{}m, Bardeen, and Ay\'on-Beato and Garc\'ia. We created a
numerical experiment, based on measurements made in the solar system,
consisting of the round trip path of light passing through a black hole at the
center. We obtained different delay times varying between the order of
$10^{-4}$s and $10^{-6}$s, for a stellar black hole; and variations of the
order of hours, for a supermassive one. Considering that the accuracy currently
achieved in measurements made in the solar system are on the order of
$10^{-12}$s, we believe that this mechanism could be used in black hole model
determination in the near future.
| [
{
"created": "Tue, 16 May 2023 14:52:59 GMT",
"version": "v1"
}
] | 2023-05-18 | [
[
"Junior",
"Ednaldo L. B.",
""
],
[
"Rodrigues",
"Manuel E.",
""
],
[
"Vieira",
"Henrique A.",
""
]
] | In this paper we propose to use Shapiro time delay as a tool to distinguish between different black hole solutions. We calculate the analytic Shapiro time, using first-order expansions, for four solutions. They are Schwarzschild, Reissner-Nordstr\"o{}m, Bardeen, and Ay\'on-Beato and Garc\'ia. We created a numerical experiment, based on measurements made in the solar system, consisting of the round trip path of light passing through a black hole at the center. We obtained different delay times varying between the order of $10^{-4}$s and $10^{-6}$s, for a stellar black hole; and variations of the order of hours, for a supermassive one. Considering that the accuracy currently achieved in measurements made in the solar system are on the order of $10^{-12}$s, we believe that this mechanism could be used in black hole model determination in the near future. |
2105.14735 | Jiawei Hu | Yuebing Zhou, Jiawei Hu, Hongwei Yu | Entanglement dynamics for Unruh-DeWitt detectors interacting with
massive scalar fields: The Unruh and anti-Unruh effects | 37 pages, 12 figures, published version | JHEP 09(2021)088 | 10.1007/JHEP09(2021)088 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study, in the framework of open quantum systems, the entanglement dynamics
for a quantum system composed of two uniformly accelerated Unruh-Dewitt
detectors interacting with a bath of massive scalar fields in the Minkowski
vacuum. We find that the entanglement evolution for the quantum system coupled
with massive fields is always slower compared with that of the one coupled with
massless fields, and this time-delay effect brought by the field being massive
can however be counteracted by a large enough acceleration, in contrast to the
case of a static quantum system in a thermal bath, where this time delay is not
affected by the temperature. Remarkably, the maximal concurrence of the quantum
system generated during evolution may increase with acceleration for any
inter-detector separation while that for static ones in a thermal bath
decreases monotonically with temperature, and this can be considered as an
anti-Unruh effect in terms of the entanglement generated.
| [
{
"created": "Mon, 31 May 2021 06:57:59 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Sep 2021 02:18:45 GMT",
"version": "v2"
}
] | 2021-09-20 | [
[
"Zhou",
"Yuebing",
""
],
[
"Hu",
"Jiawei",
""
],
[
"Yu",
"Hongwei",
""
]
] | We study, in the framework of open quantum systems, the entanglement dynamics for a quantum system composed of two uniformly accelerated Unruh-Dewitt detectors interacting with a bath of massive scalar fields in the Minkowski vacuum. We find that the entanglement evolution for the quantum system coupled with massive fields is always slower compared with that of the one coupled with massless fields, and this time-delay effect brought by the field being massive can however be counteracted by a large enough acceleration, in contrast to the case of a static quantum system in a thermal bath, where this time delay is not affected by the temperature. Remarkably, the maximal concurrence of the quantum system generated during evolution may increase with acceleration for any inter-detector separation while that for static ones in a thermal bath decreases monotonically with temperature, and this can be considered as an anti-Unruh effect in terms of the entanglement generated. |
gr-qc/9912072 | Garcia | L.C.Garcia de Andrade | On de Sitter deflationary cosmology from the spin-torsion primordial
fluctuations and COBE data | Latex file 7 Kb | null | null | null | gr-qc | null | Fluctuations on de Sitter solution of Einstein-Cartan field equations are
obtained in terms of the matter density primordial density fluctuations and
spin-torsion density and matter density fluctuations obtained from COBE data.
Einstein-de Sitter solution is shown to be unstable even in the absence of
torsion.The spin-torsion density fluctuation to generate a deflationary phase
is computed from the COBE data.
| [
{
"created": "Thu, 16 Dec 1999 23:17:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | Fluctuations on de Sitter solution of Einstein-Cartan field equations are obtained in terms of the matter density primordial density fluctuations and spin-torsion density and matter density fluctuations obtained from COBE data. Einstein-de Sitter solution is shown to be unstable even in the absence of torsion.The spin-torsion density fluctuation to generate a deflationary phase is computed from the COBE data. |
0807.3896 | Grigory Volovik | F.R. Klinkhamer and G.E. Volovik | f(R) Cosmology from q-Theory | 6 pages, v4: this archive version corresponds to the published
version with a few minor corrections | JETP Lett.88:289-294,2008 | 10.1134/S0021364008170013 | KA-TP-18-2008 | gr-qc astro-ph cond-mat.other hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From a macroscopic theory of the quantum vacuum in terms of conserved
relativistic charges (generically denoted by q^{(a)} with label a), we have
obtained, in the low-energy limit, a particular type of f(R) model relevant to
cosmology. The macroscopic quantum-vacuum theory allows us to distinguish
between different phenomenological f(R) models on physical grounds.
| [
{
"created": "Thu, 24 Jul 2008 19:14:44 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jul 2008 11:41:47 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Aug 2008 13:13:17 GMT",
"version": "v3"
},
{
"created": "Sun, 8 Feb 2009 10:31:51 GMT",
"version": "v4"
}
] | 2009-02-19 | [
[
"Klinkhamer",
"F. R.",
""
],
[
"Volovik",
"G. E.",
""
]
] | From a macroscopic theory of the quantum vacuum in terms of conserved relativistic charges (generically denoted by q^{(a)} with label a), we have obtained, in the low-energy limit, a particular type of f(R) model relevant to cosmology. The macroscopic quantum-vacuum theory allows us to distinguish between different phenomenological f(R) models on physical grounds. |
0807.2834 | Ik Siong Heng | LIGO Scientific Collaboration: B. Abbott, et al | First joint search for gravitational-wave bursts in LIGO and GEO600 data | 30 pages, 8 figures | Class.Quant.Grav.25:245008,2008 | 10.1088/0264-9381/25/24/245008 | LIGO-P080008-A-Z | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the results of the first joint search for gravitational-wave
bursts by the LIGO and GEO600 detectors. We search for bursts with
characteristic central frequencies in the band 768 to 2048 Hz in the data
acquired between the 22nd of February and the 23rd of March, 2005 (fourth LSC
Science Run - S4). We discuss the inclusion of the GEO600 data in the
Waveburst-CorrPower pipeline that first searches for coincident excess power
events without taking into account differences in the antenna responses or
strain sensitivities of the various detectors. We compare the performance of
this pipeline to that of the coherent Waveburst pipeline based on the maximum
likelihood statistic. This likelihood statistic is derived from a coherent sum
of the detector data streams that takes into account the antenna patterns and
sensitivities of the different detectors in the network. We find that the
coherentWaveburst pipeline is sensitive to signals of amplitude 30 - 50%
smaller than the Waveburst-CorrPower pipeline. We perform a search for
gravitational-wave bursts using both pipelines and find no detection candidates
in the S4 data set when all four instruments were operating stably.
| [
{
"created": "Thu, 17 Jul 2008 16:58:25 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Oct 2008 10:10:09 GMT",
"version": "v2"
}
] | 2009-01-09 | [
[
"LIGO Scientific Collaboration",
"",
""
],
[
"Abbott",
"B.",
""
]
] | We present the results of the first joint search for gravitational-wave bursts by the LIGO and GEO600 detectors. We search for bursts with characteristic central frequencies in the band 768 to 2048 Hz in the data acquired between the 22nd of February and the 23rd of March, 2005 (fourth LSC Science Run - S4). We discuss the inclusion of the GEO600 data in the Waveburst-CorrPower pipeline that first searches for coincident excess power events without taking into account differences in the antenna responses or strain sensitivities of the various detectors. We compare the performance of this pipeline to that of the coherent Waveburst pipeline based on the maximum likelihood statistic. This likelihood statistic is derived from a coherent sum of the detector data streams that takes into account the antenna patterns and sensitivities of the different detectors in the network. We find that the coherentWaveburst pipeline is sensitive to signals of amplitude 30 - 50% smaller than the Waveburst-CorrPower pipeline. We perform a search for gravitational-wave bursts using both pipelines and find no detection candidates in the S4 data set when all four instruments were operating stably. |
1412.3522 | Zhi-Yong Wang | Zhi-Yong Wang | Spin-orbit couplings of quantum fields in Schwarzschild spacetime | 13 pages, no figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | In Schwarzschild spacetime, the gravitational spin-orbit couplings of the
massless Dirac field and the photon field can be studied in a unified way. In
contrary to the previous investigations presented mainly at the
quantum-mechanical level, our work is presented at the level of quantum field
theory without resorting to the Foldy-Wouthuysen transformation. If massless
Dirac particles and photons have the same momentums, their energy-level
splittings due to the gravitational spin-orbit couplings are the same. Massless
Dirac particles and photons coming from the Hawking radiations are partially
polarized as long as their original momentums are not parallel to the radial
direction of a Schwarzschild black hole.
| [
{
"created": "Thu, 11 Dec 2014 02:32:58 GMT",
"version": "v1"
}
] | 2014-12-12 | [
[
"Wang",
"Zhi-Yong",
""
]
] | In Schwarzschild spacetime, the gravitational spin-orbit couplings of the massless Dirac field and the photon field can be studied in a unified way. In contrary to the previous investigations presented mainly at the quantum-mechanical level, our work is presented at the level of quantum field theory without resorting to the Foldy-Wouthuysen transformation. If massless Dirac particles and photons have the same momentums, their energy-level splittings due to the gravitational spin-orbit couplings are the same. Massless Dirac particles and photons coming from the Hawking radiations are partially polarized as long as their original momentums are not parallel to the radial direction of a Schwarzschild black hole. |
1611.06522 | Carlo Pagani | Carlo Pagani and Martin Reuter | Composite Operators in Asymptotic Safety | 38 pages | Phys. Rev. D 95, 066002 (2017) | 10.1103/PhysRevD.95.066002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the role of composite operators in the Asymptotic Safety program for
quantum gravity. By including in the effective average action an explicit
dependence on new sources we are able to keep track of operators which do not
belong to the exact theory space and/or are normally discarded in a truncation.
Typical examples are geometric operators such as volumes, lengths, or geodesic
distances. We show that this set-up allows to investigate the scaling
properties of various interesting operators via a suitable exact
renormalization group equation. We test our framework in several settings,
including Quantum Einstein Gravity, the conformally reduced Einstein-Hilbert
truncation, and two dimensional quantum gravity. Finally, we briefly argue that
our construction paves the way to approach observables in the Asymptotic Safety
program.
| [
{
"created": "Sun, 20 Nov 2016 15:00:18 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Dec 2016 14:35:32 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Mar 2017 14:54:45 GMT",
"version": "v3"
}
] | 2017-03-21 | [
[
"Pagani",
"Carlo",
""
],
[
"Reuter",
"Martin",
""
]
] | We study the role of composite operators in the Asymptotic Safety program for quantum gravity. By including in the effective average action an explicit dependence on new sources we are able to keep track of operators which do not belong to the exact theory space and/or are normally discarded in a truncation. Typical examples are geometric operators such as volumes, lengths, or geodesic distances. We show that this set-up allows to investigate the scaling properties of various interesting operators via a suitable exact renormalization group equation. We test our framework in several settings, including Quantum Einstein Gravity, the conformally reduced Einstein-Hilbert truncation, and two dimensional quantum gravity. Finally, we briefly argue that our construction paves the way to approach observables in the Asymptotic Safety program. |
gr-qc/9712041 | Shahar Hod | Shahar Hod and Tsvi Piran | Late-Time Evolution of Charged Gravitational Collapse and Decay of
Charged Scalar Hair - I | 14 pages, latex, no figures | Phys.Rev. D58 (1998) 024017 | 10.1103/PhysRevD.58.024017 | null | gr-qc | null | We study analytically the asymptotic evolution of charged fields around a
Reissner-Nordstr\"om black-hole. Following the no-hair theorem we focus
attention on the dynamical mechanism by which the charged hair is radiated
away. We find an inverse power-law relaxation of the charged fields at future
timelike infinity, along future null infinity and an oscillatory inverse
power-law relaxation along the future outer horizon. We show that a charged
hair is shedd slower than a neutral one. Our results are also of importance to
the study of mass inflation and the stability of Cauchy horizons during a
dynamical gravitational collapse of charged matter to form a charged black-hole
| [
{
"created": "Tue, 9 Dec 1997 10:32:44 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Hod",
"Shahar",
""
],
[
"Piran",
"Tsvi",
""
]
] | We study analytically the asymptotic evolution of charged fields around a Reissner-Nordstr\"om black-hole. Following the no-hair theorem we focus attention on the dynamical mechanism by which the charged hair is radiated away. We find an inverse power-law relaxation of the charged fields at future timelike infinity, along future null infinity and an oscillatory inverse power-law relaxation along the future outer horizon. We show that a charged hair is shedd slower than a neutral one. Our results are also of importance to the study of mass inflation and the stability of Cauchy horizons during a dynamical gravitational collapse of charged matter to form a charged black-hole |
gr-qc/0701150 | Marcello Ortaggio | Marcello Ortaggio, Vojtech Pravda, Alena Pravdova | Ricci identities in higher dimensions | 8 pages. v2: typo corrected between Propositions 2 and 3. v3: typo in
the last term in the first line of (11f) corrected, missing term on the
r.h.s. of (11p) added, first sentence between Propositions 2 and 3 slightly
changed | Class.Quant.Grav.24:1657-1664,2007 | 10.1088/0264-9381/24/6/018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore connections between geometrical properties of null congruences and
the algebraic structure of the Weyl tensor in n>4 spacetime dimensions. First,
we present the full set of Ricci identities on a suitable "null" frame, thus
completing the extension of the Newman-Penrose formalism to higher dimensions.
Then we specialize to geodetic null congruences and study specific consequences
of the Sachs equations. These imply, for example, that Kundt spacetimes are of
type II or more special (like for n=4) and that for odd n a twisting geodetic
WAND must also be shearing (in contrast to the case n=4).
| [
{
"created": "Sat, 27 Jan 2007 21:36:26 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Mar 2007 15:18:43 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Feb 2012 15:22:30 GMT",
"version": "v3"
}
] | 2012-02-22 | [
[
"Ortaggio",
"Marcello",
""
],
[
"Pravda",
"Vojtech",
""
],
[
"Pravdova",
"Alena",
""
]
] | We explore connections between geometrical properties of null congruences and the algebraic structure of the Weyl tensor in n>4 spacetime dimensions. First, we present the full set of Ricci identities on a suitable "null" frame, thus completing the extension of the Newman-Penrose formalism to higher dimensions. Then we specialize to geodetic null congruences and study specific consequences of the Sachs equations. These imply, for example, that Kundt spacetimes are of type II or more special (like for n=4) and that for odd n a twisting geodetic WAND must also be shearing (in contrast to the case n=4). |
1702.02472 | Maaneli Derakhshani | Maaneli Derakhshani | Semiclassical Newtonian Field Theories Based On Stochastic Mechanics II | 19 pages (17 pages without references), no figures, LaTeX | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Continuing the development of the ZSM-Newton/Coulomb approach to
semiclassical Newtonian gravity/electrodynamics [1], we formulate a
ZSM-Newton/Coulomb version of the large N approximation scheme proposed by
Oriols et al. [2]. We show that this new large N scheme makes it possible to
self-consistently describe the center-of-mass evolution of a large number of
gravitationally/electrostatically interacting, identical, \emph{zbw} particles,
without assuming that the particles are weakly coupled, and without entailing
the problematic macroscopic semiclassical gravitational/electrostatic cat
states characteristic of the mean-field Schr{\"o}dinger-Newton/Coulomb
equations. We also show how to recover N-particle classical Newtonian
gravity/electrodynamics for many gravitationally/electrostatically interacting
macroscopic particles (composed of many interacting \emph{zbw} particles), as
well as classical Vlasov-Poisson mean-field theory for macroscopic particles
weakly interacting gravitationally/electrostatically. Finally, we outline an
explicit model of environmental decoherence that can be incorporated into
Oriols et al.'s scheme as applied to ZSM-Newton/Coulomb.
| [
{
"created": "Tue, 7 Feb 2017 16:29:38 GMT",
"version": "v1"
}
] | 2017-02-09 | [
[
"Derakhshani",
"Maaneli",
""
]
] | Continuing the development of the ZSM-Newton/Coulomb approach to semiclassical Newtonian gravity/electrodynamics [1], we formulate a ZSM-Newton/Coulomb version of the large N approximation scheme proposed by Oriols et al. [2]. We show that this new large N scheme makes it possible to self-consistently describe the center-of-mass evolution of a large number of gravitationally/electrostatically interacting, identical, \emph{zbw} particles, without assuming that the particles are weakly coupled, and without entailing the problematic macroscopic semiclassical gravitational/electrostatic cat states characteristic of the mean-field Schr{\"o}dinger-Newton/Coulomb equations. We also show how to recover N-particle classical Newtonian gravity/electrodynamics for many gravitationally/electrostatically interacting macroscopic particles (composed of many interacting \emph{zbw} particles), as well as classical Vlasov-Poisson mean-field theory for macroscopic particles weakly interacting gravitationally/electrostatically. Finally, we outline an explicit model of environmental decoherence that can be incorporated into Oriols et al.'s scheme as applied to ZSM-Newton/Coulomb. |
1207.2153 | Alberto Diez-Tejedor | Juan Barranco, Argelia Bernal, Juan Carlos Degollado, Alberto
Diez-Tejedor, Miguel Megevand, Miguel Alcubierre, Dar\'io N\'u\~nez and
Olivier Sarbach | Schwarzschild black holes can wear scalar wigs | 5 pages, 3 figures. Accepted for publication in Physical Review
Letters | Phys. Rev. Lett. 109, 081102 (2012) | 10.1103/PhysRevLett.109.081102 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of a massive scalar field surrounding a Schwarzschild
black hole and find configurations that can survive for arbitrarily long times,
provided the black hole or the scalar field mass is small enough. In
particular, both ultra-light scalar field dark matter around supermassive black
holes and axion-like scalar fields around primordial black holes can survive
for cosmological times. Moreover, these results are quite generic, in the sense
that fairly arbitrary initial data evolves, at late times, as a combination of
those long-lived configurations.
| [
{
"created": "Mon, 9 Jul 2012 20:00:04 GMT",
"version": "v1"
}
] | 2012-08-31 | [
[
"Barranco",
"Juan",
""
],
[
"Bernal",
"Argelia",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Diez-Tejedor",
"Alberto",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Alcubierre",
"Miguel",
""
],
[
"Núñez",
"Darío",
""
],
[
"Sarbach",
"Olivier",
""
]
] | We study the evolution of a massive scalar field surrounding a Schwarzschild black hole and find configurations that can survive for arbitrarily long times, provided the black hole or the scalar field mass is small enough. In particular, both ultra-light scalar field dark matter around supermassive black holes and axion-like scalar fields around primordial black holes can survive for cosmological times. Moreover, these results are quite generic, in the sense that fairly arbitrary initial data evolves, at late times, as a combination of those long-lived configurations. |
1511.00868 | Liwei Ji | Rong-Gen Cai, Li-Wei Ji, Run-Qiu Yang | Collapse of self-interacting scalar field in anti-de Sitter space | 7 pages, 5 figures | null | 10.1088/0253-6102/65/3/329 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational collapse of a massless scalar field with a self-interaction
term $\lambda\phi^4$ in anti-de Sitter space is investigated. We numerically
investigate the effect of the self-interaction term on the critical amplitudes,
forming time of apparent horizon, stable island and energy transformation. The
results show that a positive $\lambda$ suppresses the formation of black hole,
while a negative $\lambda$ enhances the process. We define two susceptibilities
to characterize the effect of the self-interaction on the black hole formation,
and find that near the critical amplitude, there exists a universal scaling
relation with the critical exponent $\alpha \approx 0.74$ for the time of black
hole formation.
| [
{
"created": "Tue, 3 Nov 2015 12:04:54 GMT",
"version": "v1"
}
] | 2016-04-20 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Ji",
"Li-Wei",
""
],
[
"Yang",
"Run-Qiu",
""
]
] | The gravitational collapse of a massless scalar field with a self-interaction term $\lambda\phi^4$ in anti-de Sitter space is investigated. We numerically investigate the effect of the self-interaction term on the critical amplitudes, forming time of apparent horizon, stable island and energy transformation. The results show that a positive $\lambda$ suppresses the formation of black hole, while a negative $\lambda$ enhances the process. We define two susceptibilities to characterize the effect of the self-interaction on the black hole formation, and find that near the critical amplitude, there exists a universal scaling relation with the critical exponent $\alpha \approx 0.74$ for the time of black hole formation. |
2309.09439 | Ioannis Soranidis | Fil Simovic, Ioannis Soranidis | Euclidean and Hamiltonian thermodynamics for regular black holes | 19 pages, 10 figures, Published version. Comments welcome! | Phys. Rev. D 109, 044029 (2024) | 10.1103/PhysRevD.109.044029 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We investigate the thermodynamic properties of the Hayward regular black hole
using both Euclidean path integral and Hamiltonian methods, in asymptotically
anti-de Sitter, Minkowski, and de Sitter spacetimes. With the inclusion of
matter fields which act as a source for the regular black hole geometry, an
effective temperature emerges that differs from the conventional definition
related to the Killing surface gravity. We posit that this temperature is the
appropriate choice for studying thermodynamic phenomena, by demonstrating
consistency between the Euclidean and Hamiltonian formulations in the
appropriate limits. We examine the thermodynamic properties and phase structure
of the Hayward black hole in the canonical ensemble and show that, counter to
some earlier indications, standard mean-field theory critical behavior is
observed when the cosmological constant is treated as a thermodynamic pressure.
We note the absence of a Hawking-Page transition, and conjecture that quantum
gravity corrections which are suitably strong to regulate the Schwarzschild
singularity generically prevent the transition from occurring. We also show
that the Smarr relation remains linear in all cases, despite the absence of a
linearity proof for nonlinear electrodynamic theories with nonsymmetry
inheriting fields.
| [
{
"created": "Mon, 18 Sep 2023 02:42:30 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Feb 2024 23:01:26 GMT",
"version": "v2"
}
] | 2024-03-04 | [
[
"Simovic",
"Fil",
""
],
[
"Soranidis",
"Ioannis",
""
]
] | We investigate the thermodynamic properties of the Hayward regular black hole using both Euclidean path integral and Hamiltonian methods, in asymptotically anti-de Sitter, Minkowski, and de Sitter spacetimes. With the inclusion of matter fields which act as a source for the regular black hole geometry, an effective temperature emerges that differs from the conventional definition related to the Killing surface gravity. We posit that this temperature is the appropriate choice for studying thermodynamic phenomena, by demonstrating consistency between the Euclidean and Hamiltonian formulations in the appropriate limits. We examine the thermodynamic properties and phase structure of the Hayward black hole in the canonical ensemble and show that, counter to some earlier indications, standard mean-field theory critical behavior is observed when the cosmological constant is treated as a thermodynamic pressure. We note the absence of a Hawking-Page transition, and conjecture that quantum gravity corrections which are suitably strong to regulate the Schwarzschild singularity generically prevent the transition from occurring. We also show that the Smarr relation remains linear in all cases, despite the absence of a linearity proof for nonlinear electrodynamic theories with nonsymmetry inheriting fields. |
2112.04313 | Christos Tsagas | Christos G. Tsagas | The deceleration parameter in `tilted' universes: generalising the
Friedmann background | Minor revision, references added. To appear in EPJC | null | 10.1140/epjc/s10052-022-10452-4 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Large-scale bulk peculiar motions introduce a characteristic length scale,
inside which the local kinematics are dominated by peculiar-velocity
perturbations rather than by the background Hubble expansion. Regions smaller
than the aforementioned critical length, which typically varies between few
hundred and several hundred Mpc, can be heavily "contaminated" by the
observers' relative motion. For example, at the critical length -- hereafter
referred to as the "transition scale", the sign of the locally measured
deceleration parameter can change from positive to negative, while the
surrounding universe is still decelerating globally. Overall, distant observers
can assign very different values to their local deceleration parameters,
entirely because of their relative motion. In practice, this suggests that
information selected from regions inside and close to the transition scale hold
only locally and they should not be readily extrapolated to the global
universe. We show that this principle applies to essentially all Friedmann
backgrounds, irrespective of their equation of state and spatial curvature. Put
another way, the transition scale and the related effects are generic to linear
peculiar-velocity perturbations. This study generalises previous work applied,
primarily for reasons of mathematical simplicity, to a perturbed Einstein-de
Sitter universe.
| [
{
"created": "Wed, 8 Dec 2021 14:42:47 GMT",
"version": "v1"
},
{
"created": "Thu, 26 May 2022 10:51:56 GMT",
"version": "v2"
}
] | 2022-06-29 | [
[
"Tsagas",
"Christos G.",
""
]
] | Large-scale bulk peculiar motions introduce a characteristic length scale, inside which the local kinematics are dominated by peculiar-velocity perturbations rather than by the background Hubble expansion. Regions smaller than the aforementioned critical length, which typically varies between few hundred and several hundred Mpc, can be heavily "contaminated" by the observers' relative motion. For example, at the critical length -- hereafter referred to as the "transition scale", the sign of the locally measured deceleration parameter can change from positive to negative, while the surrounding universe is still decelerating globally. Overall, distant observers can assign very different values to their local deceleration parameters, entirely because of their relative motion. In practice, this suggests that information selected from regions inside and close to the transition scale hold only locally and they should not be readily extrapolated to the global universe. We show that this principle applies to essentially all Friedmann backgrounds, irrespective of their equation of state and spatial curvature. Put another way, the transition scale and the related effects are generic to linear peculiar-velocity perturbations. This study generalises previous work applied, primarily for reasons of mathematical simplicity, to a perturbed Einstein-de Sitter universe. |
gr-qc/9910022 | Mark Miller | Mark Miller, Wai-Mo Suen, and Malcolm Tobias | Collision of 1.4 $M_{\odot}$ Neutron Stars: Dynamical or
Quasi-Equilibrium? | 5 pages, 4 figures | null | null | null | gr-qc astro-ph | null | Shapiro put forth a conjecture stating that neutron stars in head-on
collisions (infalling from infinity) will not collapse to black holes before
neutrino cooling, independent of the mass of the neutron stars. In a previous
paper we carried out a numerical simulation showing a counter example based on
1.4 $M_{\odot}$ neutron stars, and provided an analysis explaining why
Shapiro's argument was not applicable for this case. A recent paper by Shapiro
put forth an argument suggesting that numerical simulations of the 1.4
$M_{\odot}$ collisions could not disprove the conjecture with the accuracy that
is presently attainable. We show in this paper that this argument is not
applicable for the same reason that the Shapiro conjecture is not applicable to
the 1.4 $M_{\odot}$ neutron star collision, namely, the collision is too
dynamical to be treated by quasi-equilibrium arguments.
| [
{
"created": "Wed, 6 Oct 1999 18:13:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Miller",
"Mark",
""
],
[
"Suen",
"Wai-Mo",
""
],
[
"Tobias",
"Malcolm",
""
]
] | Shapiro put forth a conjecture stating that neutron stars in head-on collisions (infalling from infinity) will not collapse to black holes before neutrino cooling, independent of the mass of the neutron stars. In a previous paper we carried out a numerical simulation showing a counter example based on 1.4 $M_{\odot}$ neutron stars, and provided an analysis explaining why Shapiro's argument was not applicable for this case. A recent paper by Shapiro put forth an argument suggesting that numerical simulations of the 1.4 $M_{\odot}$ collisions could not disprove the conjecture with the accuracy that is presently attainable. We show in this paper that this argument is not applicable for the same reason that the Shapiro conjecture is not applicable to the 1.4 $M_{\odot}$ neutron star collision, namely, the collision is too dynamical to be treated by quasi-equilibrium arguments. |
0807.0969 | Karim Noui | Karim Noui | A model for the motion of a particle in a quantum background | 21 pages | Phys.Rev.D78:105008,2008 | 10.1103/PhysRevD.78.105008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We are studying the dynamics of a one-dimensional field in a non-commutative
Euclidean space. The non-commutative space we consider is the one that emerges
in the context of three dimensional Euclidean quantum gravity: it is a
deformation of the classical Euclidean space and the Planck length plays the
role of the deformation parameter. The field is interpreted as a particle which
evolves in a quantum background. When the dynamics of the particle is linear,
the resulting motion is similar to the standard motion in the classical space.
However, non-linear dynamics on the non-commutative space are different from
the corresponding non-linear dynamics on the classical space. These
discrepencies are interpreted as "quantum gravity" effects. Finally, we propose
a background independent description of the propagation of the particle in the
quantum geometry.
| [
{
"created": "Mon, 7 Jul 2008 08:56:52 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Noui",
"Karim",
""
]
] | We are studying the dynamics of a one-dimensional field in a non-commutative Euclidean space. The non-commutative space we consider is the one that emerges in the context of three dimensional Euclidean quantum gravity: it is a deformation of the classical Euclidean space and the Planck length plays the role of the deformation parameter. The field is interpreted as a particle which evolves in a quantum background. When the dynamics of the particle is linear, the resulting motion is similar to the standard motion in the classical space. However, non-linear dynamics on the non-commutative space are different from the corresponding non-linear dynamics on the classical space. These discrepencies are interpreted as "quantum gravity" effects. Finally, we propose a background independent description of the propagation of the particle in the quantum geometry. |
2307.16098 | Giorgi Tukhashvili | Giorgi Tukhashvili and Paul J. Steinhardt | Cosmological Bounces Induced by a Fermion Condensate | 5 pages, 4 figures; to appear in PRL | Phys. Rev. Lett. 131, 091001 (2023) | 10.1103/PhysRevLett.131.091001 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that it is possible for fermion condensation of the
Nambu-Jona-Lasinio type to induce a non-singular bounce that smoothly connects
a phase of slow contraction to a phase of expansion. A chiral condensate -- a
non-zero vacuum expectation value of the spinor bilinear $\langle
\bar{\Psi}\Psi \rangle$ -- can form spontaneously after a slow contraction
phase smooths and flattens the universe and the Ricci-curvature exceeds a
critical value. In this approach, a high density of spin-aligned free fermions
is not required, which avoids the problem of generating a large anisotropy and
initiating chaotic mixmaster behavior during the bounce phase.
| [
{
"created": "Sun, 30 Jul 2023 01:03:48 GMT",
"version": "v1"
}
] | 2023-08-30 | [
[
"Tukhashvili",
"Giorgi",
""
],
[
"Steinhardt",
"Paul J.",
""
]
] | We show that it is possible for fermion condensation of the Nambu-Jona-Lasinio type to induce a non-singular bounce that smoothly connects a phase of slow contraction to a phase of expansion. A chiral condensate -- a non-zero vacuum expectation value of the spinor bilinear $\langle \bar{\Psi}\Psi \rangle$ -- can form spontaneously after a slow contraction phase smooths and flattens the universe and the Ricci-curvature exceeds a critical value. In this approach, a high density of spin-aligned free fermions is not required, which avoids the problem of generating a large anisotropy and initiating chaotic mixmaster behavior during the bounce phase. |
1304.0672 | Nicola Tamanini | Nicola Tamanini and Christian G. Boehmer | Definition of Good Tetrads for f(T) Gravity | Prepared for the proceedings of the 13th Marcel Grossmann Meeting | null | 10.1142/9789814623995_0148 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The importance of choosing suitable tetrads for the study of exact solutions
in f(T) gravity is discussed. For any given metric, we define the concept of
good tetrads as the tetrads satisfying the field equations without constrainig
the function f(T). Employing local Lorentz transformations, good tetrads in the
context of spherical symmetry are found for Schwarzschild-de Sitter solutions.
| [
{
"created": "Tue, 2 Apr 2013 15:52:40 GMT",
"version": "v1"
}
] | 2017-02-22 | [
[
"Tamanini",
"Nicola",
""
],
[
"Boehmer",
"Christian G.",
""
]
] | The importance of choosing suitable tetrads for the study of exact solutions in f(T) gravity is discussed. For any given metric, we define the concept of good tetrads as the tetrads satisfying the field equations without constrainig the function f(T). Employing local Lorentz transformations, good tetrads in the context of spherical symmetry are found for Schwarzschild-de Sitter solutions. |
gr-qc/9704050 | Larry Ford | L.H. Ford and N.F. Svaiter | Cosmological and Black Hole Horizon Fluctuations | 22 pages, Latex, 4 figures, uses epsf | Phys. Rev. D 56, 2226 (1997) | 10.1103/PhysRevD.56.2226 | CBPF-NF-017/97, TUTP-97-8 | gr-qc hep-th | null | The quantum fluctuations of horizons in Robertson-Walker universes and in the
Schwarzschild spacetime are discussed. The source of the metric fluctuations is
taken to be quantum linear perturbations of the gravitational field. Lightcone
fluctuations arise when the retarded Green's function for a massless field is
averaged over these metric fluctuations. This averaging replaces the
delta-function on the classical lightcone with a Gaussian function, the width
of which is a measure of the scale of the lightcone fluctuations. Horizon
fluctuations are taken to be measured in the frame of a geodesic observer
falling through the horizon. In the case of an expanding universe, this is a
comoving observer either entering or leaving the horizon of another observer.
In the black hole case, we take this observer to be one who falls freely from
rest at infinity. We find that cosmological horizon fluctuations are typically
characterized by the Planck length. However, black hole horizon fluctuations in
this model are much smaller than Planck dimensions for black holes whose mass
exceeds the Planck mass. Furthermore, we find black hole horizon fluctuations
which are sufficiently small as not to invalidate the semiclassical derivation
of the Hawking process.
| [
{
"created": "Thu, 17 Apr 1997 17:48:44 GMT",
"version": "v1"
}
] | 2016-08-24 | [
[
"Ford",
"L. H.",
""
],
[
"Svaiter",
"N. F.",
""
]
] | The quantum fluctuations of horizons in Robertson-Walker universes and in the Schwarzschild spacetime are discussed. The source of the metric fluctuations is taken to be quantum linear perturbations of the gravitational field. Lightcone fluctuations arise when the retarded Green's function for a massless field is averaged over these metric fluctuations. This averaging replaces the delta-function on the classical lightcone with a Gaussian function, the width of which is a measure of the scale of the lightcone fluctuations. Horizon fluctuations are taken to be measured in the frame of a geodesic observer falling through the horizon. In the case of an expanding universe, this is a comoving observer either entering or leaving the horizon of another observer. In the black hole case, we take this observer to be one who falls freely from rest at infinity. We find that cosmological horizon fluctuations are typically characterized by the Planck length. However, black hole horizon fluctuations in this model are much smaller than Planck dimensions for black holes whose mass exceeds the Planck mass. Furthermore, we find black hole horizon fluctuations which are sufficiently small as not to invalidate the semiclassical derivation of the Hawking process. |
gr-qc/0409009 | Yuri Pavlov | Yu. V. Pavlov | Renormalization and dimensional regularization for a scalar field with
Gauss-Bonnet-type coupling to curvature | LATEX, 21 pages, no figure | Theor.Math.Phys. 140 (2004) 1095-1108; Teor.Mat.Fiz. 140 (2004)
241-255 | null | null | gr-qc hep-th | null | We consider a scalar field with a Gauss-Bonnet-type coupling to the curvature
in a curved space-time. For such a quadratic coupling to the curvature, the
metric energy-momentum tensor does not contain derivatives of the metric of
orders greater than two. We obtain the metric energy-momentum tensor and find
the geometric structure of the first three counterterms to the vacuum averages
of the energy-momentum tensor for an arbitrary background metric of an
N-dimensional space-time. In a homogeneous isotropic space, we obtain the first
three counterterms of the n-wave procedure, which allow calculating the
renormalized values of the vacuum averages of the energy-momentum tensors in
the dimensions N=4,5. Using dimensional regularization, we establish that the
geometric structures of the counterterms in the $n$-wave procedure coincide
with those in the effective action method.
| [
{
"created": "Thu, 2 Sep 2004 09:56:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pavlov",
"Yu. V.",
""
]
] | We consider a scalar field with a Gauss-Bonnet-type coupling to the curvature in a curved space-time. For such a quadratic coupling to the curvature, the metric energy-momentum tensor does not contain derivatives of the metric of orders greater than two. We obtain the metric energy-momentum tensor and find the geometric structure of the first three counterterms to the vacuum averages of the energy-momentum tensor for an arbitrary background metric of an N-dimensional space-time. In a homogeneous isotropic space, we obtain the first three counterterms of the n-wave procedure, which allow calculating the renormalized values of the vacuum averages of the energy-momentum tensors in the dimensions N=4,5. Using dimensional regularization, we establish that the geometric structures of the counterterms in the $n$-wave procedure coincide with those in the effective action method. |
gr-qc/9704070 | N. K. Dadhich | Naresh Dadhich and K. Narayan | On the third law of black hole dynamics | 9 pages, LaTeX version, Accepted in Physics Letters A | Phys.Lett. A231 (1997) 335-338 | 10.1016/S0375-9601(97)00337-X | IUCAA-31/97 | gr-qc | null | The third law of black hole dynamics states that the surface gravity
(temperature) of black hole cannot be reduced to zero in finite sequence of
physical interactions. We argue that the same is true when surface gravity is
replaced by gravitational charge. We demonstrate that the prescribed window for
infalling energy and radiation pinches off as extremality ($M^2 = a^2 + Q^2 $)
is approached.
| [
{
"created": "Fri, 25 Apr 1997 13:30:46 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Dadhich",
"Naresh",
""
],
[
"Narayan",
"K.",
""
]
] | The third law of black hole dynamics states that the surface gravity (temperature) of black hole cannot be reduced to zero in finite sequence of physical interactions. We argue that the same is true when surface gravity is replaced by gravitational charge. We demonstrate that the prescribed window for infalling energy and radiation pinches off as extremality ($M^2 = a^2 + Q^2 $) is approached. |
1602.03478 | Ichiro Oda | Ichiro Oda | Induced Gravity and Topological Quantum Field Theory | 7 pages | null | null | DPUR/TH/47 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct an induced gravity (pregeometry) where both the Newton constant
and the cosmological constant appear as integration constants in solving field
equations. By adding the kinetic terms of ghosts and antighosts, an action of
the induced gravity is transformed to a topological field theory. Moreover, by
solving field equations of the topological field theory in the FRW universe, we
find an inflation solution. The present study might shed some light on a close
relationship between the induced gravity and the topological quantum field
theory.
| [
{
"created": "Wed, 10 Feb 2016 18:34:34 GMT",
"version": "v1"
}
] | 2016-02-11 | [
[
"Oda",
"Ichiro",
""
]
] | We construct an induced gravity (pregeometry) where both the Newton constant and the cosmological constant appear as integration constants in solving field equations. By adding the kinetic terms of ghosts and antighosts, an action of the induced gravity is transformed to a topological field theory. Moreover, by solving field equations of the topological field theory in the FRW universe, we find an inflation solution. The present study might shed some light on a close relationship between the induced gravity and the topological quantum field theory. |
2204.05640 | Carlos A. R. Herdeiro | Carlos A. R. Herdeiro | Black holes: on the universality of the Kerr hypothesis | 16 pages, 3 figures, contribution to the forthcoming book "Modified
and Quantum Gravity - From theory to experimental searches on all scales" | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | To what extent are all astrophysical, dark, compact objects both black holes
(BHs) and described by the Kerr geometry? We embark on the exercise of defying
the universality of this remarkable idea, often called the "Kerr hypothesis".
After establishing its rationale and timeliness, we define a minimal set of
reasonability criteria for alternative models of dark compact objects. Then, as
proof of principle, we discuss concrete, dynamically robust non-Kerr BHs and
horizonless imitators, that 1) pass the basic theoretical, and in particular
dynamical, tests, 2) match (some of the) state of the art astrophysical
observables and 3) only emerge at some (macroscopic) scales. These examples
illustrate how the universality (at all macroscopic scales) of the Kerr
hypothesis can be challenged.
| [
{
"created": "Tue, 12 Apr 2022 09:06:40 GMT",
"version": "v1"
}
] | 2022-04-13 | [
[
"Herdeiro",
"Carlos A. R.",
""
]
] | To what extent are all astrophysical, dark, compact objects both black holes (BHs) and described by the Kerr geometry? We embark on the exercise of defying the universality of this remarkable idea, often called the "Kerr hypothesis". After establishing its rationale and timeliness, we define a minimal set of reasonability criteria for alternative models of dark compact objects. Then, as proof of principle, we discuss concrete, dynamically robust non-Kerr BHs and horizonless imitators, that 1) pass the basic theoretical, and in particular dynamical, tests, 2) match (some of the) state of the art astrophysical observables and 3) only emerge at some (macroscopic) scales. These examples illustrate how the universality (at all macroscopic scales) of the Kerr hypothesis can be challenged. |
1911.06315 | Jhonny Andres Agudelo Ruiz J. A. Agudelo Ruiz | Jhonny A. Agudelo Ruiz, Tib\'erio de Paula Netto, J\'ulio C. Fabris,
Ilya L. Shapiro | Primordial universe with the running cosmological constant | 24 pages, 6 figures, 1 table. Some misprints and notations corrected.
Version fits published in EPJC. Three references to the same group of authors
added due to the request of anonymous referee, with the corresponding
critical explanations | Eur. Phys. J. C 80, 851 (2020) | 10.1140/epjc/s10052-020-8226-x | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theoretically, the running of the cosmological constant in the IR region is
not ruled out. On the other hand, from the QFT viewpoint, the energy released
due to the variation of the cosmological constant in the late universe cannot
go to the matter sector. For this reason, the phenomenological bounds on such a
running are not sufficiently restrictive. The situation can be different in the
early universe when the gravitational field was sufficiently strong to provide
an efficient creation of particles from the vacuum. We develop a framework for
systematically exploring this ossibility. It is supposed that the running
occurs in the epoch when the Dark Matter already decoupled and is expanding
adiabatically, while baryons are approximately massless and can be abundantly
created from vacuum due to the decay of vacuum energy. By using the handy model
of Reduced Relativistic Gas for describing the Dark Matter, we consider the
dynamics of both cosmic background and linear perturbations and evaluate the
impact of the vacuum decay on the matter power spectrum and to the first CMB
peak. Additionally, using the combined data of CMB+BAO+SNIa we find the best
fit values for the free parameters of our model.
| [
{
"created": "Thu, 14 Nov 2019 18:55:39 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jan 2020 20:57:08 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Sep 2020 04:10:44 GMT",
"version": "v3"
}
] | 2020-09-30 | [
[
"Ruiz",
"Jhonny A. Agudelo",
""
],
[
"Netto",
"Tibério de Paula",
""
],
[
"Fabris",
"Júlio C.",
""
],
[
"Shapiro",
"Ilya L.",
""
]
] | Theoretically, the running of the cosmological constant in the IR region is not ruled out. On the other hand, from the QFT viewpoint, the energy released due to the variation of the cosmological constant in the late universe cannot go to the matter sector. For this reason, the phenomenological bounds on such a running are not sufficiently restrictive. The situation can be different in the early universe when the gravitational field was sufficiently strong to provide an efficient creation of particles from the vacuum. We develop a framework for systematically exploring this ossibility. It is supposed that the running occurs in the epoch when the Dark Matter already decoupled and is expanding adiabatically, while baryons are approximately massless and can be abundantly created from vacuum due to the decay of vacuum energy. By using the handy model of Reduced Relativistic Gas for describing the Dark Matter, we consider the dynamics of both cosmic background and linear perturbations and evaluate the impact of the vacuum decay on the matter power spectrum and to the first CMB peak. Additionally, using the combined data of CMB+BAO+SNIa we find the best fit values for the free parameters of our model. |
2111.14845 | Gargi Biswas | Gargi Biswas, M K Dutta and B Modak | Wormhole inducing inflation with Einstein Gauss Bonnet dilaton
interaction | 17 pages, 17 figures, communicated in MPLA. arXiv admin note: text
overlap with arXiv:2111.13913 | null | 10.1142/S0217732322501218 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We present a few Euclidean wormhole configurations using both the analytic
and numerical solutions of the field equations considering Einstein
Gauss-Bonnet dilaton interaction in 4-dimensional Robertson Walker Euclidean
background. In one analytic solution we present transition from a wormhole to
an exponential expansion with Lorentzian time $t$ using $\tau=it$ after passing
through an era of oscillating Euclidean wormhole. The numerical solutions of
the scale factor $a(\tau)$ show multiple local maxima and minima about a global
minimum for inverse power law potentials, while for exponential potential the
wormholes have a single minimum. The Hubble parameter and deceleration
parameter obtained by curve fit of $a(\tau)$ of the numerical solution show an
inflation away from the throat of the wormhole invoking analytic continuation
by $\tau=it$. A sharp decay of the potential is also observed.
| [
{
"created": "Mon, 29 Nov 2021 17:34:59 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Dec 2021 17:01:28 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Mar 2022 05:57:21 GMT",
"version": "v3"
},
{
"created": "Fri, 13 May 2022 07:52:35 GMT",
"version": "v4"
}
] | 2022-08-31 | [
[
"Biswas",
"Gargi",
""
],
[
"Dutta",
"M K",
""
],
[
"Modak",
"B",
""
]
] | We present a few Euclidean wormhole configurations using both the analytic and numerical solutions of the field equations considering Einstein Gauss-Bonnet dilaton interaction in 4-dimensional Robertson Walker Euclidean background. In one analytic solution we present transition from a wormhole to an exponential expansion with Lorentzian time $t$ using $\tau=it$ after passing through an era of oscillating Euclidean wormhole. The numerical solutions of the scale factor $a(\tau)$ show multiple local maxima and minima about a global minimum for inverse power law potentials, while for exponential potential the wormholes have a single minimum. The Hubble parameter and deceleration parameter obtained by curve fit of $a(\tau)$ of the numerical solution show an inflation away from the throat of the wormhole invoking analytic continuation by $\tau=it$. A sharp decay of the potential is also observed. |
2301.04834 | Soham Sen | Soham Sen, Rituparna Mandal and Sunandan Gangopadhyay | Near horizon approximation and beyond for a two-level atom falling into
a Kerr-Newman black hole | 15 Pages LATEX | Eur. Phys. J. Plus (2023) 138:855 | 10.1140/epjp/s13360-023-04482-4 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we investigate the phenomena of acceleration radiation for a
two-level atom falling into the event horizon of a Kerr-Newman black hole. In
https://link.aps.org/doi/10.1103/PhysRevD.104.065006 (Phys. Rev. D 104 (2021)
065006), it has been shown that conformal quantum mechanics has a connection to
the generated Planck-like spectrum due to acceleration radiation. In this
particular aspect, the near horizon approximation played a significant role. In
https://link.aps.org/doi/10.1103/PhysRevD.106.025004 (Phys. Rev. D 106 (2022)
025004), we have used the beyond near horizon approximation to show that the
excitation probability attains a Planck-like spectrum irrespective of the
non-existence of an underlying conformal symmetry for a general class of static
spherically symmetric black holes. In our analysis we have gone beyond the near
horizon approximation for the rotating and charged case and even without the
consideration of the conformal symmetry we observe a similar Planck-like
spectrum. However, the coefficient of the spectrum is significantly different
from the near horizon case. We have then considered a different scenario where
a two-level atom emits multiple photons while freely falling into the event
horizon of the Kerr-Newman black hole. It is observed that the Planck factor in
the excitation probability is significantly small than that of the case of
single-photon emission (for large number of simultaneously emitted photons from
the two-level atom). Finally, we have computed the von-Neumann entropy which is
also known as the horizon brightened acceleration radiation entropy or the HBAR
entropy. We have carried out our analysis for a scalar field only to see the
effect of the charge and rotation of the black hole in this particular
scenario.
| [
{
"created": "Thu, 12 Jan 2023 06:34:27 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Sep 2023 17:59:49 GMT",
"version": "v2"
}
] | 2023-09-28 | [
[
"Sen",
"Soham",
""
],
[
"Mandal",
"Rituparna",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | In this work we investigate the phenomena of acceleration radiation for a two-level atom falling into the event horizon of a Kerr-Newman black hole. In https://link.aps.org/doi/10.1103/PhysRevD.104.065006 (Phys. Rev. D 104 (2021) 065006), it has been shown that conformal quantum mechanics has a connection to the generated Planck-like spectrum due to acceleration radiation. In this particular aspect, the near horizon approximation played a significant role. In https://link.aps.org/doi/10.1103/PhysRevD.106.025004 (Phys. Rev. D 106 (2022) 025004), we have used the beyond near horizon approximation to show that the excitation probability attains a Planck-like spectrum irrespective of the non-existence of an underlying conformal symmetry for a general class of static spherically symmetric black holes. In our analysis we have gone beyond the near horizon approximation for the rotating and charged case and even without the consideration of the conformal symmetry we observe a similar Planck-like spectrum. However, the coefficient of the spectrum is significantly different from the near horizon case. We have then considered a different scenario where a two-level atom emits multiple photons while freely falling into the event horizon of the Kerr-Newman black hole. It is observed that the Planck factor in the excitation probability is significantly small than that of the case of single-photon emission (for large number of simultaneously emitted photons from the two-level atom). Finally, we have computed the von-Neumann entropy which is also known as the horizon brightened acceleration radiation entropy or the HBAR entropy. We have carried out our analysis for a scalar field only to see the effect of the charge and rotation of the black hole in this particular scenario. |
1905.06931 | Vadim Belov | Vadim Belov | On Geometry and Symmetries in Classical and Quantum Theories of Gauge
Gravity | PhD thesis, 167 pages. The first few chapters may serve an (almost)
self-contained introduction into differential geometry of Cartan connections
and gauge gravity. The special emphasis is paid to symmetries, as well as
contact between infinitesimal (`microscopic') and integral (`coarse-grained')
pictures is exhibited, in a background independent context | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin Foam and Loop approaches to Quantum Gravity reformulate Einstein's
theory of relativity in terms of connection variables. The metric properties
are encoded in face bivectors/conjugate fluxes that are required to satisfy
certain conditions, in order to allow for their geometric interpretation. We
show that the (sub-)set of the so-called `volume simplicity constraints' is not
implemented properly in the current EPRL-FK spinfoam vertex amplitude, if
extended to arbitrary polyhedra. We then propose that a certain knot-invariant
of the bivector geometry, induced on the boundary graph, encodes the missing
conditions, allowing for reconstruction of a polytope from its two-dimensional
faces. Implemented in the quantum amplitude, this leads to corrected
semi-classical asymptotics for a hypercuboid, and is conjectured to be
non-trivial in more general situations. The analysis of linear version of
`volume simplicity' suggests to switch from hypersurface normals to edge
lengths, that is from 3-forms directly to tetrads -- in the extended
configuration space of the Plebanski constrained formulation. We then give the
corresponding dual version of linear simplicity constraints, which prescribe 3d
volume for the polyhedral faces in the boundary of a 4d polytope. We also
analyse the status of metric/vielbein degrees of freedom and the role of local
translations in the classical Einstein-Cartan gravity, viewed as a Poincare
gauge theory. The relation with the diffeomorphism symmetry is established
through the key concept of development, which generalizes parallel transport of
vectors in the geometric theory of Cartan connections. We advocate the latter
to be the natural gauge-theoretic framework for the theory of relativity.
| [
{
"created": "Thu, 16 May 2019 17:47:43 GMT",
"version": "v1"
}
] | 2019-05-17 | [
[
"Belov",
"Vadim",
""
]
] | Spin Foam and Loop approaches to Quantum Gravity reformulate Einstein's theory of relativity in terms of connection variables. The metric properties are encoded in face bivectors/conjugate fluxes that are required to satisfy certain conditions, in order to allow for their geometric interpretation. We show that the (sub-)set of the so-called `volume simplicity constraints' is not implemented properly in the current EPRL-FK spinfoam vertex amplitude, if extended to arbitrary polyhedra. We then propose that a certain knot-invariant of the bivector geometry, induced on the boundary graph, encodes the missing conditions, allowing for reconstruction of a polytope from its two-dimensional faces. Implemented in the quantum amplitude, this leads to corrected semi-classical asymptotics for a hypercuboid, and is conjectured to be non-trivial in more general situations. The analysis of linear version of `volume simplicity' suggests to switch from hypersurface normals to edge lengths, that is from 3-forms directly to tetrads -- in the extended configuration space of the Plebanski constrained formulation. We then give the corresponding dual version of linear simplicity constraints, which prescribe 3d volume for the polyhedral faces in the boundary of a 4d polytope. We also analyse the status of metric/vielbein degrees of freedom and the role of local translations in the classical Einstein-Cartan gravity, viewed as a Poincare gauge theory. The relation with the diffeomorphism symmetry is established through the key concept of development, which generalizes parallel transport of vectors in the geometric theory of Cartan connections. We advocate the latter to be the natural gauge-theoretic framework for the theory of relativity. |
2112.03652 | Tiago Gon\c{c}alves | Tiago B. Gon\c{c}alves, Jo\~ao Lu\'is Rosa, Francisco S. N. Lobo | Cosmology in the novel scalar-tensor representation of $f(R,T)$ gravity | 11 pages, 3 figures; Contribution to the Sixteenth Marcel Grossman
Conference (MG16, Rome, July, 2021), to be published by World Scientific;
based on arXiv:2112.02541 [gr-qc] | The Sixteenth Marcel Grossmann Meeting, pp. 932-942 (2023) | 10.1142/9789811269776_0072 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply cosmological reconstruction methods to the $f(R,T)$ modified
gravity, in its recently developed scalar-tensor representation. We do this
analysis assuming a perfect fluid in a Friedmann-Lema\^{i}tre-Robsertson-Walker
(FLRW) universe. In this contribution we show the equations of motion obtained
and we present the solutions found for one of the particular cases we analysed:
an exponential evolution of the cosmological scale factor.
| [
{
"created": "Tue, 7 Dec 2021 12:03:08 GMT",
"version": "v1"
}
] | 2024-07-24 | [
[
"Gonçalves",
"Tiago B.",
""
],
[
"Rosa",
"João Luís",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | We apply cosmological reconstruction methods to the $f(R,T)$ modified gravity, in its recently developed scalar-tensor representation. We do this analysis assuming a perfect fluid in a Friedmann-Lema\^{i}tre-Robsertson-Walker (FLRW) universe. In this contribution we show the equations of motion obtained and we present the solutions found for one of the particular cases we analysed: an exponential evolution of the cosmological scale factor. |
1311.0732 | Ivan Arraut | Ivan Arraut | On the Black Holes in alternative theories of gravity: The case of
non-linear massive gravity | Final version to appear at Int.J.Mod.Phys. D. arXiv admin note:
substantial text overlap with arXiv:1305.0475 | Int. J. Mod. Phys. D 24, No. 4 (2015) 1550022 | 10.1142/S0218271815500224 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I derive general conditions in order to explain the origin of the Vainshtein
radius inside dRGT. The set of equations, which I have called "Vainshtein"
conditions are extremal conditions of the dynamical metric ($g_{\mu\nu}$)
containing all the degrees of freedom of the theory. The Vainshtein conditions
are able to explain the coincidence between the Vainshtein radius in dRGT and
the scale $r_0=\left(\frac{3}{2}r_s r_\Lambda^2\right)^{1/3}$, obtained
naturally from the Schwarzschild de-Sitter (S-dS) space inside General
Relativity (GR). In GR, this scale was interpreted as the maximum distance in
order to get bound orbits. The same scale corresponds to the static observer
position if we want to define the black hole temperature in an asymptotically
de-Sitter space. In dRGT, the scale marks a limit after which the extra degrees
of freedom of the theory become relevant.
| [
{
"created": "Mon, 4 Nov 2013 15:26:33 GMT",
"version": "v1"
},
{
"created": "Fri, 2 May 2014 12:20:39 GMT",
"version": "v2"
},
{
"created": "Sun, 11 May 2014 14:13:20 GMT",
"version": "v3"
},
{
"created": "Wed, 28 May 2014 05:06:34 GMT",
"version": "v4"
},
{
"created": "Wed, 23 Jul 2014 11:20:13 GMT",
"version": "v5"
},
{
"created": "Tue, 9 Dec 2014 11:11:56 GMT",
"version": "v6"
}
] | 2014-12-30 | [
[
"Arraut",
"Ivan",
""
]
] | I derive general conditions in order to explain the origin of the Vainshtein radius inside dRGT. The set of equations, which I have called "Vainshtein" conditions are extremal conditions of the dynamical metric ($g_{\mu\nu}$) containing all the degrees of freedom of the theory. The Vainshtein conditions are able to explain the coincidence between the Vainshtein radius in dRGT and the scale $r_0=\left(\frac{3}{2}r_s r_\Lambda^2\right)^{1/3}$, obtained naturally from the Schwarzschild de-Sitter (S-dS) space inside General Relativity (GR). In GR, this scale was interpreted as the maximum distance in order to get bound orbits. The same scale corresponds to the static observer position if we want to define the black hole temperature in an asymptotically de-Sitter space. In dRGT, the scale marks a limit after which the extra degrees of freedom of the theory become relevant. |
1201.5278 | Francesco Becattini | F. Becattini (University of Florence) | Covariant statistical mechanics and the stress-energy tensor | 4 pages. Final version accepted for publication in Phys. Rev. Lett | null | 10.1103/PhysRevLett.108.244502 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After recapitulating the covariant formalism of equilibrium statistical
mechanics in special relativity and extending it to the case of a non-vanishing
spin tensor, we show that the relativistic stress-energy tensor at
thermodynamical equilibrium can be obtained from a functional derivative of the
partition function with respect to the inverse temperature four-vector \beta.
For usual thermodynamical equilibrium, the stress-energy tensor turns out to be
the derivative of the relativistic thermodynamic potential current with respect
to the four-vector \beta, i.e. T^{\mu \nu} = - \partial \Phi^\mu/\partial
\beta_\nu. This formula establishes a relation between stress-energy tensor and
entropy current at equilibrium possibly extendable to non-equilibrium
hydrodynamics.
| [
{
"created": "Wed, 25 Jan 2012 14:23:34 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jan 2012 19:35:42 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Jun 2012 16:05:51 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Becattini",
"F.",
"",
"University of Florence"
]
] | After recapitulating the covariant formalism of equilibrium statistical mechanics in special relativity and extending it to the case of a non-vanishing spin tensor, we show that the relativistic stress-energy tensor at thermodynamical equilibrium can be obtained from a functional derivative of the partition function with respect to the inverse temperature four-vector \beta. For usual thermodynamical equilibrium, the stress-energy tensor turns out to be the derivative of the relativistic thermodynamic potential current with respect to the four-vector \beta, i.e. T^{\mu \nu} = - \partial \Phi^\mu/\partial \beta_\nu. This formula establishes a relation between stress-energy tensor and entropy current at equilibrium possibly extendable to non-equilibrium hydrodynamics. |
gr-qc/0108083 | Peter Anninos | Peter Anninos | Computational Cosmology: from the Early Universe to the Large Scale
Structure | appearing, Living Reviews in Relativity | null | 10.12942/lrr-2001-2 | null | gr-qc | null | In order to account for the observable Universe, any comprehensive theory or
model of cosmology must draw from many disciplines of physics, including gauge
theories of strong and weak interactions, the hydrodynamics and microphysics of
baryonic matter, electromagnetic fields, and spacetime curvature, for example.
Although it is difficult to incorporate all these physical elements into a
single complete model of our Universe, advances in computing methods and
technologies have contributed significantly towards our understanding of
cosmological models, the Universe, and astrophysical processes within them. A
sample of numerical calculations (and numerical methods) applied to specific
issues in cosmology are reviewed in this article: from the Big Bang singularity
dynamics to the fundamental interactions of gravitational waves; from the
quark-hadron phase transition to the large scale structure of the Universe. The
emphasis, although not exclusively, is on those calculations designed to test
different models of cosmology against the observed Universe.
| [
{
"created": "Fri, 31 Aug 2001 00:50:27 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Anninos",
"Peter",
""
]
] | In order to account for the observable Universe, any comprehensive theory or model of cosmology must draw from many disciplines of physics, including gauge theories of strong and weak interactions, the hydrodynamics and microphysics of baryonic matter, electromagnetic fields, and spacetime curvature, for example. Although it is difficult to incorporate all these physical elements into a single complete model of our Universe, advances in computing methods and technologies have contributed significantly towards our understanding of cosmological models, the Universe, and astrophysical processes within them. A sample of numerical calculations (and numerical methods) applied to specific issues in cosmology are reviewed in this article: from the Big Bang singularity dynamics to the fundamental interactions of gravitational waves; from the quark-hadron phase transition to the large scale structure of the Universe. The emphasis, although not exclusively, is on those calculations designed to test different models of cosmology against the observed Universe. |
1809.00670 | Ion I. Cotaescu | Ion I. Cotaescu | Integral representation of the Feynman propagators of the Dirac fermions
on the de Sitter expanding universe | 5 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1804.02842 | Eur. Phys. J. C (2018) 78:769 | 10.1140/epjc/s10052-018-6258-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The propagators of the Dirac fermions on the expanding portion of the
(1+3)-dimensional de Sitter spacetime are considered as mode sums in momentum
representation with a fixed vacuum of Bunch-Davies type. The principal result
reported here is a new integral representation of the Feynman propagators of
the massive and left-handed massless Dirac fields which can be used for
deriving the Feynman rules of the de Sitter QED in Coulomb gauge or of an
extended QFT.
| [
{
"created": "Mon, 3 Sep 2018 17:55:25 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Sep 2018 13:08:19 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Sep 2018 16:57:02 GMT",
"version": "v3"
}
] | 2018-10-17 | [
[
"Cotaescu",
"Ion I.",
""
]
] | The propagators of the Dirac fermions on the expanding portion of the (1+3)-dimensional de Sitter spacetime are considered as mode sums in momentum representation with a fixed vacuum of Bunch-Davies type. The principal result reported here is a new integral representation of the Feynman propagators of the massive and left-handed massless Dirac fields which can be used for deriving the Feynman rules of the de Sitter QED in Coulomb gauge or of an extended QFT. |
1810.11138 | Nobuyoshi Komatsu | Nobuyoshi Komatsu | Generalized thermodynamic constraints on holographic-principle-based
cosmological scenarios | Final version accepted for publication in PRD. Typos are fixed. [8
pages, 1 figure]. arXiv admin note: text overlap with arXiv:1707.09101 | Phys. Rev. D 99, 043523 (2019) | 10.1103/PhysRevD.99.043523 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The holographic principle can lead to cosmological scenarios, i.e.,
holographic equipartition models. In this model, an extra driving term
(corresponding to a time-varying cosmological term) in cosmological equations
depends on an associated entropy on the horizon of the universe. The driving
term is expected to be constrained by the second law of thermodynamics, as if
the cosmological constant problem could be discussed from a thermodynamics
viewpoint. In the present study, an arbitrary entropy on the horizon, $S_{H}$,
is assumed, extending previous analysis based on particular entropies [Phys.
Rev. D 96, 103507 (2017); (arXiv:1707.09101)]. The arbitrary entropy is applied
to the holographic equipartition model, in order to universally examine
thermodynamic constraints on the driving term in a flat
Friedmann--Robertson--Walker universe at late times. The second law of
thermodynamics for the holographic equipartition model is found to constrain
the upper limit of the driving term, even if the arbitrary entropy is assumed.
The upper limit implies that the order of the driving term is likely consistent
with the order of the cosmological constant measured by observations. An
approximately equivalent upper limit can be obtained from the positivity of
$S_{H}$ in the holographic equipartition model.
| [
{
"created": "Thu, 25 Oct 2018 23:37:45 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Feb 2019 23:46:02 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Feb 2019 00:20:45 GMT",
"version": "v3"
}
] | 2019-02-25 | [
[
"Komatsu",
"Nobuyoshi",
""
]
] | The holographic principle can lead to cosmological scenarios, i.e., holographic equipartition models. In this model, an extra driving term (corresponding to a time-varying cosmological term) in cosmological equations depends on an associated entropy on the horizon of the universe. The driving term is expected to be constrained by the second law of thermodynamics, as if the cosmological constant problem could be discussed from a thermodynamics viewpoint. In the present study, an arbitrary entropy on the horizon, $S_{H}$, is assumed, extending previous analysis based on particular entropies [Phys. Rev. D 96, 103507 (2017); (arXiv:1707.09101)]. The arbitrary entropy is applied to the holographic equipartition model, in order to universally examine thermodynamic constraints on the driving term in a flat Friedmann--Robertson--Walker universe at late times. The second law of thermodynamics for the holographic equipartition model is found to constrain the upper limit of the driving term, even if the arbitrary entropy is assumed. The upper limit implies that the order of the driving term is likely consistent with the order of the cosmological constant measured by observations. An approximately equivalent upper limit can be obtained from the positivity of $S_{H}$ in the holographic equipartition model. |
gr-qc/9812054 | Ken-ichi Oohara | Takashi Nakamura (YITP) and Ken-ichi Oohara (Niigata University) | A Way to 3D Numerical Relativity --- Coalescing Binary Neutron Stars --- | 11 pages, 9 figures, invited talk at Numerical Astrophysics 1998 | null | null | null | gr-qc astro-ph | null | One of the most promising sources of gravitational radiation is coalescence
of binary neutron stars or black holes. In order to study gravitational
radiation at the merging phase of coalescing binary neutron stars which is
called the last three-milliseconds, full general relativistic simulations are
required. Since coalescence of binary stars is a completely non-axisymmetric
and 3 dimensional (in space) event, which needs great powers of computers, we
have to develop a method of 3D numerical relativity using a vector-parallel
supercomputer. As a first step of this final goal, we started simulations using
post-Newtonian hydrodynamics including radiation reaction of gravitational
waves from 1989. They gave a lot of perspectives on coalescing events and
gravitational radiation from them. Next we started to attack 3D, fully
relativistic simulations. First, basic equations on the (3+1)-formalism of the
Einstein equations are shown. As for gauge conditions, we use conformal time
slicing and psuedo minimal distortion condtions at present. For these
conditions as well as to solve initial value equations, we should solve some
elliptic partial differential equations. It consumes the greatest part of CPU
time. We show recent results of test simulations on coalescing binary neutron
stars.
| [
{
"created": "Wed, 16 Dec 1998 07:33:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nakamura",
"Takashi",
"",
"YITP"
],
[
"Oohara",
"Ken-ichi",
"",
"Niigata University"
]
] | One of the most promising sources of gravitational radiation is coalescence of binary neutron stars or black holes. In order to study gravitational radiation at the merging phase of coalescing binary neutron stars which is called the last three-milliseconds, full general relativistic simulations are required. Since coalescence of binary stars is a completely non-axisymmetric and 3 dimensional (in space) event, which needs great powers of computers, we have to develop a method of 3D numerical relativity using a vector-parallel supercomputer. As a first step of this final goal, we started simulations using post-Newtonian hydrodynamics including radiation reaction of gravitational waves from 1989. They gave a lot of perspectives on coalescing events and gravitational radiation from them. Next we started to attack 3D, fully relativistic simulations. First, basic equations on the (3+1)-formalism of the Einstein equations are shown. As for gauge conditions, we use conformal time slicing and psuedo minimal distortion condtions at present. For these conditions as well as to solve initial value equations, we should solve some elliptic partial differential equations. It consumes the greatest part of CPU time. We show recent results of test simulations on coalescing binary neutron stars. |
gr-qc/9608009 | Raphael Bousso | Raphael Bousso and Stephen W. Hawking (DAMTP, Cambridge) | Primordial Black Holes: Tunnelling vs. No Boundary Proposal | 14 pages, LaTeX, 1 figure; contribution to the proceedings of COSMION
96 | Grav.Cosmol.Suppl.4:28-37,1998 | null | DAMTP/R-96/34 | gr-qc astro-ph | null | In the inflationary era, black holes came into existence together with the
universe through the quantum process of pair creation. We calculate the pair
creation rate from the no boundary proposal for the wave function of the
universe. Our results are physically sensible and fit in with other
descriptions of pair creation. The tunnelling proposal, on the other hand,
predicts a catastrophic instability of de Sitter space to the nucleation of
large black holes, and cannot be maintained.
| [
{
"created": "Fri, 2 Aug 1996 19:06:26 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Bousso",
"Raphael",
"",
"DAMTP, Cambridge"
],
[
"Hawking",
"Stephen W.",
"",
"DAMTP, Cambridge"
]
] | In the inflationary era, black holes came into existence together with the universe through the quantum process of pair creation. We calculate the pair creation rate from the no boundary proposal for the wave function of the universe. Our results are physically sensible and fit in with other descriptions of pair creation. The tunnelling proposal, on the other hand, predicts a catastrophic instability of de Sitter space to the nucleation of large black holes, and cannot be maintained. |
2407.17203 | Eleftherios-Ermis Tselentis | Eleftherios-Ermis Tselentis and \"Amin Baumeler | The M\"obius Game: A Quantum-Inspired Test of General Relativity | 5 pages, 4 figures, short version of arXiv:2309.15752 [qr-qc] with
new relativistic setup | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We present a tight inequality to test the dynamical nature of spacetime. A
general-relativistic violation of that inequality certifies change of
curvature, in the same sense as a quantum-mechanical violation of a Bell
inequality certifies a source of entanglement. The inequality arises from a
minimal generalization of the Bell setup. It represents a limit on the winning
chance of a collaborative multi-agent game played on the M\"obius graph. A long
version of this Letter including other games and how these games certify the
dynamical character of the celebrated quantum switch is accessible as
arXiv:2309.15752 [gr-qc].
| [
{
"created": "Wed, 24 Jul 2024 12:03:10 GMT",
"version": "v1"
}
] | 2024-07-26 | [
[
"Tselentis",
"Eleftherios-Ermis",
""
],
[
"Baumeler",
"Ämin",
""
]
] | We present a tight inequality to test the dynamical nature of spacetime. A general-relativistic violation of that inequality certifies change of curvature, in the same sense as a quantum-mechanical violation of a Bell inequality certifies a source of entanglement. The inequality arises from a minimal generalization of the Bell setup. It represents a limit on the winning chance of a collaborative multi-agent game played on the M\"obius graph. A long version of this Letter including other games and how these games certify the dynamical character of the celebrated quantum switch is accessible as arXiv:2309.15752 [gr-qc]. |
1109.1437 | Herbert Hamber | Herbert W. Hamber and Reiko Toriumi | Scale-Dependent Newton's Constant G in the Conformal Newtonian Gauge | 37 pages | null | 10.1103/PhysRevD.84.103507 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In classical gravity deviations from the predictions of the Einstein theory
are often discussed within the framework of the conformal Newtonian gauge,
where scalar perturbations are described by two potentials $\phi$ and $\psi$.
In this paper we use the above gauge to explore possible cosmological
consequences of a running Newton's constant $ G (\Box) $, as suggested by the
nontrivial ultraviolet fixed point scenario arising from the quantum
field-theoretic treatment of Einstein gravity with a cosmological constant
term. Here we focus on the effects of a scale-dependent coupling on the
so-called gravitational slip functions $\eta = \psi / \phi -1 $, whose
classical general relativity value is zero. Starting from a set of manifestly
covariant but non-local effective field equations derived earlier, we compute
the leading corrections in the potentials $\phi$ and $\psi$ for a
nonrelativistic, pressureless fluid. After providing an estimate for the
quantity $\eta$, we then focus on a comparison with results obtained in a
previous paper on matter density perturbations in the synchronous gauge, which
gave an estimate for the growth index parameter $\gamma$, also in the presence
of a running $G$. Our results indicate that, in the present framework and for a
given $ G (\Box) $, the corrections tend to be significantly larger in
magnitude for the perturbation growth exponents than for the conformal
Newtonian gauge slip function.
| [
{
"created": "Wed, 7 Sep 2011 12:40:04 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Oct 2011 21:54:21 GMT",
"version": "v2"
}
] | 2013-01-07 | [
[
"Hamber",
"Herbert W.",
""
],
[
"Toriumi",
"Reiko",
""
]
] | In classical gravity deviations from the predictions of the Einstein theory are often discussed within the framework of the conformal Newtonian gauge, where scalar perturbations are described by two potentials $\phi$ and $\psi$. In this paper we use the above gauge to explore possible cosmological consequences of a running Newton's constant $ G (\Box) $, as suggested by the nontrivial ultraviolet fixed point scenario arising from the quantum field-theoretic treatment of Einstein gravity with a cosmological constant term. Here we focus on the effects of a scale-dependent coupling on the so-called gravitational slip functions $\eta = \psi / \phi -1 $, whose classical general relativity value is zero. Starting from a set of manifestly covariant but non-local effective field equations derived earlier, we compute the leading corrections in the potentials $\phi$ and $\psi$ for a nonrelativistic, pressureless fluid. After providing an estimate for the quantity $\eta$, we then focus on a comparison with results obtained in a previous paper on matter density perturbations in the synchronous gauge, which gave an estimate for the growth index parameter $\gamma$, also in the presence of a running $G$. Our results indicate that, in the present framework and for a given $ G (\Box) $, the corrections tend to be significantly larger in magnitude for the perturbation growth exponents than for the conformal Newtonian gauge slip function. |
1810.04477 | Shibaji Banerjee | Shibaji Banerjee, Ashadul Halder, Sanjay K. Ghosh, Sibaji Raha,
Debasish Majumdar | Speeding up of Binary Merger Due to "Apparent" Gravitational Wave
Emissions | 17 Pages, 12 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves from binary black hole pairs have emerged as an important
observational tool in current times. The energy of the BH - BH binary pair is
radiated in the form of gravitational waves and to compensate for that energy,
kinetic energy of the system decreases gradually. Consequently the mutual
separation of the objects decreases with time and tends to merge. The whole
process may require a very long time comparable or longer than the age of the
universe, specially in the case of low mass mergers. We have examined the case
in which a massive object compared to the individual masses comprising the
binary pair is present nearby such a system. We have found that in this case
the merging process takes place much rapidly than that of the conventional
BH-BH merging process. Scenarios with both an Intermediate Mass Black Hole
(IBMH) ($10^{5}\:M_{\odot}$) as well as a Super Massive Black Hole (SMBH) have
been studied and the latter has been found to provide a much higher overall
rate for the BH-BH merger process.
| [
{
"created": "Wed, 10 Oct 2018 12:21:34 GMT",
"version": "v1"
}
] | 2018-10-11 | [
[
"Banerjee",
"Shibaji",
""
],
[
"Halder",
"Ashadul",
""
],
[
"Ghosh",
"Sanjay K.",
""
],
[
"Raha",
"Sibaji",
""
],
[
"Majumdar",
"Debasish",
""
]
] | Gravitational waves from binary black hole pairs have emerged as an important observational tool in current times. The energy of the BH - BH binary pair is radiated in the form of gravitational waves and to compensate for that energy, kinetic energy of the system decreases gradually. Consequently the mutual separation of the objects decreases with time and tends to merge. The whole process may require a very long time comparable or longer than the age of the universe, specially in the case of low mass mergers. We have examined the case in which a massive object compared to the individual masses comprising the binary pair is present nearby such a system. We have found that in this case the merging process takes place much rapidly than that of the conventional BH-BH merging process. Scenarios with both an Intermediate Mass Black Hole (IBMH) ($10^{5}\:M_{\odot}$) as well as a Super Massive Black Hole (SMBH) have been studied and the latter has been found to provide a much higher overall rate for the BH-BH merger process. |
2006.16036 | Joao Magueijo | John D. Barrow and Joao Magueijo | A contextual Planck parameter and the classical limit in quantum
cosmology | null | null | 10.1007/s10701-021-00433-0 | null | gr-qc astro-ph.CO quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose that whatever quantity controls the Heisenberg uncertainty
relations (for a given complementary pair of observables) it should be
identified with an effective Planck parameter. With this definition it is not
difficult to find examples where the Planck parameter depends on the region
under study, varies in time, and even depends on which pair of observables one
focuses on. In quantum cosmology the effective Planck parameter depends on the
size of the comoving region under study, and so depends on that chosen region
and on time. With this criterion, the classical limit is expected, not for
regions larger than the Planck length, $l_{P}$, but for those larger than
$l_{Q}=(l_{P}^{2}H^{-1})^{1/3}$, where $H$ is the Hubble parameter. In theories
where the cosmological constant is dynamical, it is possible for the latter to
remain quantum even in contexts where everything else is deemed classical.
These results are derived from standard quantization methods, but we also
include more speculative cases where ad hoc Planck parameters scale differently
with the length scale under observation. Even more speculatively, we examine
the possibility that similar complementary concepts affect thermodynamical
variables, such as the temperature and the entropy of a black hole.
| [
{
"created": "Mon, 29 Jun 2020 13:29:29 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jan 2021 18:45:27 GMT",
"version": "v2"
}
] | 2021-03-17 | [
[
"Barrow",
"John D.",
""
],
[
"Magueijo",
"Joao",
""
]
] | We propose that whatever quantity controls the Heisenberg uncertainty relations (for a given complementary pair of observables) it should be identified with an effective Planck parameter. With this definition it is not difficult to find examples where the Planck parameter depends on the region under study, varies in time, and even depends on which pair of observables one focuses on. In quantum cosmology the effective Planck parameter depends on the size of the comoving region under study, and so depends on that chosen region and on time. With this criterion, the classical limit is expected, not for regions larger than the Planck length, $l_{P}$, but for those larger than $l_{Q}=(l_{P}^{2}H^{-1})^{1/3}$, where $H$ is the Hubble parameter. In theories where the cosmological constant is dynamical, it is possible for the latter to remain quantum even in contexts where everything else is deemed classical. These results are derived from standard quantization methods, but we also include more speculative cases where ad hoc Planck parameters scale differently with the length scale under observation. Even more speculatively, we examine the possibility that similar complementary concepts affect thermodynamical variables, such as the temperature and the entropy of a black hole. |
gr-qc/0001032 | Alec Maassen van den Brink | Alec Maassen van den Brink | Analytic treatment of black-hole gravitational waves at the
algebraically special frequency | REVTeX, 17 pages, submitted to Phys. Rev. D | Phys.Rev. D62 (2000) 064009 | 10.1103/PhysRevD.62.064009 | ITFA 2000-02 | gr-qc | null | We study the Regge-Wheeler and Zerilli equations (RWE and ZE) at the
`algebraically special frequency' $\Omega$, where these equations admit an
exact solution (elaborated here), generating the SUSY relationship between
them. The physical significance of the SUSY generator and of the solutions at
$\Omega$ in general is elucidated as follows. The RWE has no (quasinormal or
total-transmission) modes at all; however, $\Omega$ is nonetheless `special' in
that (a) for the outgoing wave into the horizon one has a `miraculous'
cancellation of a divergence expected due to the exponential potential tail,
and (b) the branch-cut discontinuity at $\omega=\Omega$ vanishes in the
outgoing wave to infinity. Moreover, (a) and (b) are related. For the ZE, its
only mode is the-inverse-SUSY generator, which is at the same time a
quasinormal mode_and_ a total-transmission mode propagating to infinity. The
subtlety of these findings (of general relevance for future study of the
equations on or near the negative imaginary $\omega$-axis) may help explain why
the situation has sometimes been controversial. For finite black-hole rotation,
the algebraically special modes are shown to be totally transmitting, and the
implied singular nature of the Schwarzschild limit is clarified. The analysis
draws on a recent detailed investigation of SUSY in open systems
[math-ph/9909030].
| [
{
"created": "Tue, 11 Jan 2000 23:38:24 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Brink",
"Alec Maassen van den",
""
]
] | We study the Regge-Wheeler and Zerilli equations (RWE and ZE) at the `algebraically special frequency' $\Omega$, where these equations admit an exact solution (elaborated here), generating the SUSY relationship between them. The physical significance of the SUSY generator and of the solutions at $\Omega$ in general is elucidated as follows. The RWE has no (quasinormal or total-transmission) modes at all; however, $\Omega$ is nonetheless `special' in that (a) for the outgoing wave into the horizon one has a `miraculous' cancellation of a divergence expected due to the exponential potential tail, and (b) the branch-cut discontinuity at $\omega=\Omega$ vanishes in the outgoing wave to infinity. Moreover, (a) and (b) are related. For the ZE, its only mode is the-inverse-SUSY generator, which is at the same time a quasinormal mode_and_ a total-transmission mode propagating to infinity. The subtlety of these findings (of general relevance for future study of the equations on or near the negative imaginary $\omega$-axis) may help explain why the situation has sometimes been controversial. For finite black-hole rotation, the algebraically special modes are shown to be totally transmitting, and the implied singular nature of the Schwarzschild limit is clarified. The analysis draws on a recent detailed investigation of SUSY in open systems [math-ph/9909030]. |
1605.06026 | De-Chang Dai | De-Chang Dai, Dejan Stojkovic | Collapsing objects with the same gravitational trajectory can radiate
away different amount of energy | 5 pages, 5 figures, accepted by PLB. arXiv admin note: text overlap
with arXiv:1601.07921 | Physics Letters B, 758, 412-415 (2016) | 10.1016/j.physletb.2016.05.036 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study radiation emitted during the gravitational collapse from two
different types of shells. We assume that one shell is made of dark matter and
is completely transparent to the test scalar (for simplicity) field which
belongs to the standard model, while the other shell is made of the standard
model particles and is totally reflecting to the scalar field. These two shells
have exactly the same mass, charge and angular momentum (though we set the
charge and angular momentum to zero), and therefore follow the same geodesic
trajectory. However, we demonstrate that they radiate away different amount of
energy during the collapse. This difference can in principle be used by an
asymptotic observer to reconstruct the physical properties of the initial
collapsing object other than mass, charge and angular momentum. This result has
implications for the information paradox and expands the list of the type of
information which can be released from a collapsing object.
| [
{
"created": "Fri, 13 May 2016 01:33:44 GMT",
"version": "v1"
}
] | 2016-05-31 | [
[
"Dai",
"De-Chang",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | We study radiation emitted during the gravitational collapse from two different types of shells. We assume that one shell is made of dark matter and is completely transparent to the test scalar (for simplicity) field which belongs to the standard model, while the other shell is made of the standard model particles and is totally reflecting to the scalar field. These two shells have exactly the same mass, charge and angular momentum (though we set the charge and angular momentum to zero), and therefore follow the same geodesic trajectory. However, we demonstrate that they radiate away different amount of energy during the collapse. This difference can in principle be used by an asymptotic observer to reconstruct the physical properties of the initial collapsing object other than mass, charge and angular momentum. This result has implications for the information paradox and expands the list of the type of information which can be released from a collapsing object. |
gr-qc/0310121 | Yuri Obukhov | Yuri N. Obukhov | Generalized plane-fronted gravitational waves in any dimension | Revtex, 18 pages, no figures | Phys.Rev. D69 (2004) 024013 | 10.1103/PhysRevD.69.024013 | null | gr-qc hep-th | null | We study the gravitational waves in spacetimes of arbitrary dimension. They
generalize the pp-waves and the Kundt waves, obtained earlier in four
dimensions. Explicit solutions of the Einstein and Einstein-Maxwell equations
are derived for an arbitrary cosmological constant.
| [
{
"created": "Wed, 29 Oct 2003 19:18:03 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Obukhov",
"Yuri N.",
""
]
] | We study the gravitational waves in spacetimes of arbitrary dimension. They generalize the pp-waves and the Kundt waves, obtained earlier in four dimensions. Explicit solutions of the Einstein and Einstein-Maxwell equations are derived for an arbitrary cosmological constant. |
2212.11948 | Horng Sheng Chia | Horng Sheng Chia, Christoffel Doorman, Alexandra Wernersson, Tanja
Hinderer, Samaya Nissanke | Self-Interacting Gravitational Atoms in the Strong-Gravity Regime | 27 pages, 10 figures | null | 10.1088/1475-7516/2023/04/018 | null | gr-qc hep-ph hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We numerically investigate free and self-interacting ultralight scalar fields
around black holes in General Relativity. We focus on complex scalar fields
$\Phi$ whose self-interactions are described by the quartic potential $V
\propto \lambda |\Phi|^4$, and ignore the black hole spin in order to
disentangle the effects of self interactions on the boson cloud. Using the
spectral solver Kadath, we compute quasi-equilibrium configurations of the
dominant eigenstates, including their backreaction on the spacetime metric. For
scenarios with $- 10^{-2} \lesssim \lambda \lesssim 10^{-2}$ we find the mass
of the self-interacting scalar cloud to be up to $\sim 70\%$ larger than that
of a free scalar cloud, though the additional backreaction effect on the
spacetime metric is only up to $\sim 1\%$ due to the low-density nature of the
bosonic configurations. In this region of parameter space we observe
approximate quadratic scalings between the mass of the cloud with $\lambda$,
the scalar field amplitude, and the couplings between these two parameters. For
systems with $\lambda$ beyond this range, the eigenfrequencies differ
sufficiently from the known free-test-field values used as inputs in our
numerical setup to make the results, though convergent, physically unreliable.
This bounds the range of $\lambda$ in which the free scalar field solution
remains a good approximation to self-interacting scalar field configurations.
Our work is among the first nonperturbative explorations of self-interacting
bosonic clouds around black holes, yielding detailed new insights into such
systems in the nonlinear regime, while also overcoming technical challenges and
quantifying limitations. Additionally, our results provide useful inputs for
fully dynamical numerical relativity simulations and for future explorations of
spinning black holes and real scalar fields.
| [
{
"created": "Thu, 22 Dec 2022 18:34:22 GMT",
"version": "v1"
}
] | 2023-04-19 | [
[
"Chia",
"Horng Sheng",
""
],
[
"Doorman",
"Christoffel",
""
],
[
"Wernersson",
"Alexandra",
""
],
[
"Hinderer",
"Tanja",
""
],
[
"Nissanke",
"Samaya",
""
]
] | We numerically investigate free and self-interacting ultralight scalar fields around black holes in General Relativity. We focus on complex scalar fields $\Phi$ whose self-interactions are described by the quartic potential $V \propto \lambda |\Phi|^4$, and ignore the black hole spin in order to disentangle the effects of self interactions on the boson cloud. Using the spectral solver Kadath, we compute quasi-equilibrium configurations of the dominant eigenstates, including their backreaction on the spacetime metric. For scenarios with $- 10^{-2} \lesssim \lambda \lesssim 10^{-2}$ we find the mass of the self-interacting scalar cloud to be up to $\sim 70\%$ larger than that of a free scalar cloud, though the additional backreaction effect on the spacetime metric is only up to $\sim 1\%$ due to the low-density nature of the bosonic configurations. In this region of parameter space we observe approximate quadratic scalings between the mass of the cloud with $\lambda$, the scalar field amplitude, and the couplings between these two parameters. For systems with $\lambda$ beyond this range, the eigenfrequencies differ sufficiently from the known free-test-field values used as inputs in our numerical setup to make the results, though convergent, physically unreliable. This bounds the range of $\lambda$ in which the free scalar field solution remains a good approximation to self-interacting scalar field configurations. Our work is among the first nonperturbative explorations of self-interacting bosonic clouds around black holes, yielding detailed new insights into such systems in the nonlinear regime, while also overcoming technical challenges and quantifying limitations. Additionally, our results provide useful inputs for fully dynamical numerical relativity simulations and for future explorations of spinning black holes and real scalar fields. |
1510.07400 | Hiromu Ogawa | Hiromu Ogawa, Tsutomu Kobayashi, Teruaki Suyama | Instability of hairy black holes in shift-symmetric Horndeski theories | 9 pages, version accepted for publication in Physical Review D; Error
corrected in Section 3, Appendix A and Appendix B, results unchanged | Phys. Rev. D 93, 064078 (2016) | 10.1103/PhysRevD.93.064078 | RUP-15-22, RESCEU-27/15 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it was pointed out that in shift-symmetric scalar-tensor theories a
black hole can have nontrivial scalar hair which depends linearly on time. We
develop black hole perturbation theory for such solutions and compute the
quadratic action of odd-parity perturbations. We show that around all the
solutions known so far with such time-dependent scalar hair the perturbations
trigger instabilities or are presumably strongly coupled.
| [
{
"created": "Mon, 26 Oct 2015 08:35:17 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Apr 2016 08:29:06 GMT",
"version": "v2"
},
{
"created": "Sun, 11 Sep 2016 09:03:03 GMT",
"version": "v3"
}
] | 2016-09-13 | [
[
"Ogawa",
"Hiromu",
""
],
[
"Kobayashi",
"Tsutomu",
""
],
[
"Suyama",
"Teruaki",
""
]
] | Recently it was pointed out that in shift-symmetric scalar-tensor theories a black hole can have nontrivial scalar hair which depends linearly on time. We develop black hole perturbation theory for such solutions and compute the quadratic action of odd-parity perturbations. We show that around all the solutions known so far with such time-dependent scalar hair the perturbations trigger instabilities or are presumably strongly coupled. |
2011.02515 | Yosef Verbin | Y. Verbin | Magnetic and Electric Black Holes in the Vector-Tensor Horndeski Theory | 30 pages, significantly expanded version + title change. Accepted for
publication in PRD | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct exact solutions of magnetically charged black holes in the
vector-tensor Horndeski gravity and discuss their main features. Unlike the
analogous electric case, the field equations are linear in a simple (quite
standard) parametrization of the metric tensor and they can be solved
analytically even when a cosmological constant is added. The solutions are
presented in terms of hypergeometric functions which makes the analysis of the
black hole properties relatively straightforward. Some of the aspects of these
black holes are quite ordinary like the existence of extremal configurations
with maximal magnetic charge for a given mass, or the existence of a mass with
maximal temperature for a given charge, but others are somewhat unexpected,
like the existence of black holes with a repulsive gravitational field. We
perform our analysis for both signs of the non-minimal coupling constant and
find black hole solutions in both cases but with significant differences
between them. The most prominent difference is the fact that the black holes
for the negative coupling constant have a spherical surface of curvature
singularity rather than a single point. On the other hand, the gravitational
field produced around this kind of black holes is always attractive. Also, for
small enough magnetic charge and negative coupling constant, extremal black
holes do not exist and all magnetic black holes have a single horizon. In
addition we study the trajectories around these magnetic black holes for light
as well as massive particles either neutral or electrically charged. Finally,
we compare the main features of these black holes with their electric
counterparts, adding some aspects that have not been discussed before, like
temperature, particle trajectories and light deflection by electrically charged
Horndesky black holes.
| [
{
"created": "Wed, 4 Nov 2020 19:43:07 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Nov 2020 09:37:35 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Jul 2022 05:13:08 GMT",
"version": "v3"
}
] | 2022-07-18 | [
[
"Verbin",
"Y.",
""
]
] | We construct exact solutions of magnetically charged black holes in the vector-tensor Horndeski gravity and discuss their main features. Unlike the analogous electric case, the field equations are linear in a simple (quite standard) parametrization of the metric tensor and they can be solved analytically even when a cosmological constant is added. The solutions are presented in terms of hypergeometric functions which makes the analysis of the black hole properties relatively straightforward. Some of the aspects of these black holes are quite ordinary like the existence of extremal configurations with maximal magnetic charge for a given mass, or the existence of a mass with maximal temperature for a given charge, but others are somewhat unexpected, like the existence of black holes with a repulsive gravitational field. We perform our analysis for both signs of the non-minimal coupling constant and find black hole solutions in both cases but with significant differences between them. The most prominent difference is the fact that the black holes for the negative coupling constant have a spherical surface of curvature singularity rather than a single point. On the other hand, the gravitational field produced around this kind of black holes is always attractive. Also, for small enough magnetic charge and negative coupling constant, extremal black holes do not exist and all magnetic black holes have a single horizon. In addition we study the trajectories around these magnetic black holes for light as well as massive particles either neutral or electrically charged. Finally, we compare the main features of these black holes with their electric counterparts, adding some aspects that have not been discussed before, like temperature, particle trajectories and light deflection by electrically charged Horndesky black holes. |
2104.01917 | Mehdi Shokri | Mehdi Shokri, Jafar Sadeghi and Mohammad Reza Setare | The generalized $sl(2, R)$ and $su(1, 1)$ in non-minimal constant-roll
inflation | 6 pages | null | 10.1016/j.aop.2021.168487 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | In the present work, we consider the non-minimal coupling inflationary model
in the context of the constant-roll idea which is investigated by the
first-order formalism. We attempt to find the hidden symmetries behind the
model by the Lie symmetry method. We supply this aim by using the symmetry
features of the Heun function instead of Killing vector approach. We show that
the hidden symmetries of the non-minimal constant-roll inflation in the cases
of power-law and exponential couplings are characterized as a generalized form
of $sl(2, R)$ and $su(1, 1)$ algebra, respectively.
| [
{
"created": "Wed, 31 Mar 2021 13:12:37 GMT",
"version": "v1"
}
] | 2021-06-02 | [
[
"Shokri",
"Mehdi",
""
],
[
"Sadeghi",
"Jafar",
""
],
[
"Setare",
"Mohammad Reza",
""
]
] | In the present work, we consider the non-minimal coupling inflationary model in the context of the constant-roll idea which is investigated by the first-order formalism. We attempt to find the hidden symmetries behind the model by the Lie symmetry method. We supply this aim by using the symmetry features of the Heun function instead of Killing vector approach. We show that the hidden symmetries of the non-minimal constant-roll inflation in the cases of power-law and exponential couplings are characterized as a generalized form of $sl(2, R)$ and $su(1, 1)$ algebra, respectively. |
1602.05949 | Giuseppe Congedo | Giuseppe Congedo and Fabrizio De Marchi | Testing the Strong Equivalence Principle with spacecraft ranging towards
the nearby Lagrangian points | 8 pages, 2 figures, 2 tables | Phys. Rev. D 93, 102003 (2016) | 10.1103/PhysRevD.93.102003 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity is supported by great experimental evidence. Yet there is
a lot of interest in precisely setting its limits with on going and future
experiments. A question to answer is about the validity of the Strong
Equivalence Principle. Ground experiments and Lunar Laser Ranging have provided
the best upper limit on the Nordtvedt parameter $\sigma[\eta]=4.4\times
10^{-4}$. With the future planetary mission BepiColombo, this parameter will be
further improved by at least an order of magnitude. In this paper we envisage
yet another possible testing environment with spacecraft ranging towards the
nearby Sun-Earth collinear Lagrangian points. Neglecting errors in planetary
masses and ephemerides, we forecast $\sigma[\eta]=6.4\,(2.0)\times10^{-4}$ (5
yr integration time) via ranging towards $L_1$ in a realistic (optimistic)
scenario depending on current (future) range capabilities and knowledge of the
Earth's ephemerides. A combined measurement, $L_1$+$L_2$, gives instead
$4.8\,(1.7)\times10^{-4}$. In the optimistic scenario a single measurement of
one year would be enough to reach $\approx3\times10^{-4}$. All figures are
comparable with Lunar Laser Ranging, but worse than BepiColombo. Performances
could be much improved if data were integrated over time and over the number of
satellites flying around either of the two Lagrangian points. We point out that
some systematics (gravitational perturbations of other planets or figure
effects) are much more in control compared to other experiments. We do not
advocate a specific mission to constrain the Strong Equivalence Principle, but
we do suggest analysing ranging data of present and future spacecrafts flying
around $L_1$/$L_2$ (one key mission is, for instance, LISA Pathfinder). This
spacecraft ranging would be a new and complementary probe to constrain the
Strong Equivalence Principle in space.
| [
{
"created": "Thu, 18 Feb 2016 20:57:50 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Apr 2016 12:12:33 GMT",
"version": "v2"
}
] | 2016-05-11 | [
[
"Congedo",
"Giuseppe",
""
],
[
"De Marchi",
"Fabrizio",
""
]
] | General relativity is supported by great experimental evidence. Yet there is a lot of interest in precisely setting its limits with on going and future experiments. A question to answer is about the validity of the Strong Equivalence Principle. Ground experiments and Lunar Laser Ranging have provided the best upper limit on the Nordtvedt parameter $\sigma[\eta]=4.4\times 10^{-4}$. With the future planetary mission BepiColombo, this parameter will be further improved by at least an order of magnitude. In this paper we envisage yet another possible testing environment with spacecraft ranging towards the nearby Sun-Earth collinear Lagrangian points. Neglecting errors in planetary masses and ephemerides, we forecast $\sigma[\eta]=6.4\,(2.0)\times10^{-4}$ (5 yr integration time) via ranging towards $L_1$ in a realistic (optimistic) scenario depending on current (future) range capabilities and knowledge of the Earth's ephemerides. A combined measurement, $L_1$+$L_2$, gives instead $4.8\,(1.7)\times10^{-4}$. In the optimistic scenario a single measurement of one year would be enough to reach $\approx3\times10^{-4}$. All figures are comparable with Lunar Laser Ranging, but worse than BepiColombo. Performances could be much improved if data were integrated over time and over the number of satellites flying around either of the two Lagrangian points. We point out that some systematics (gravitational perturbations of other planets or figure effects) are much more in control compared to other experiments. We do not advocate a specific mission to constrain the Strong Equivalence Principle, but we do suggest analysing ranging data of present and future spacecrafts flying around $L_1$/$L_2$ (one key mission is, for instance, LISA Pathfinder). This spacecraft ranging would be a new and complementary probe to constrain the Strong Equivalence Principle in space. |
2211.14179 | Julian Barbour | Julian Barbour | Time's Arrow and Simultaneity: A Critique of Rovelli's Views | 6 pages, 1 figure | null | null | null | gr-qc cond-mat.stat-mech physics.hist-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In the joint paper "Bridging the neuroscience and physics of time" Rovelli,
as the physicist coauthor of neuroscientist Dean Buonomano, makes statements
that rely on theoretical frameworks employed when the laws of thermodynamics
and general relativity were discovered. Their reconsideration in the light of
subsequent insights suggests growth of entropy is not the origin of time's
arrow and that a notion of universal simultaneity may exist within general
relativity. This paper is a slightly extended form of my invited contribution
to the forthcoming Frontiers in Psychology special issue "Physical time within
human time".
| [
{
"created": "Fri, 25 Nov 2022 15:34:30 GMT",
"version": "v1"
}
] | 2022-11-28 | [
[
"Barbour",
"Julian",
""
]
] | In the joint paper "Bridging the neuroscience and physics of time" Rovelli, as the physicist coauthor of neuroscientist Dean Buonomano, makes statements that rely on theoretical frameworks employed when the laws of thermodynamics and general relativity were discovered. Their reconsideration in the light of subsequent insights suggests growth of entropy is not the origin of time's arrow and that a notion of universal simultaneity may exist within general relativity. This paper is a slightly extended form of my invited contribution to the forthcoming Frontiers in Psychology special issue "Physical time within human time". |
gr-qc/0112046 | Yuan-xing Gui | D. Yu, Y.-X. Gui, and X. Ye | The Relation of Thermal Fluctuation and Information-Entropy for
One-Dimensional Rindler Oscillator | 14 pages, 1 figure | Mod.Phys.Lett. A16 (2001) 2241-2248 | 10.1142/S0217732301005618 | gr-qc/0112046 | gr-qc | null | Within the framework of thermo-field-dynamics (TFD), the
information-entropies associated with the measurements of position and momentum
for one-dimensional Rindler oscillator are derived, and the connection between
its information-entropy and thermal fluctuation is obtained. A conclusion is
drawn that the thermal fluctuation leads to the loss of information.
| [
{
"created": "Wed, 19 Dec 2001 10:36:52 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Dec 2001 01:36:38 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Yu",
"D.",
""
],
[
"Gui",
"Y. -X.",
""
],
[
"Ye",
"X.",
""
]
] | Within the framework of thermo-field-dynamics (TFD), the information-entropies associated with the measurements of position and momentum for one-dimensional Rindler oscillator are derived, and the connection between its information-entropy and thermal fluctuation is obtained. A conclusion is drawn that the thermal fluctuation leads to the loss of information. |
gr-qc/0212059 | Edmundo M. Monte | Edmundo M. Monte (U.F.Paraiba) and M.D.Maia (U.Brasilia) | On Schwarzschild's Topology in Brane-Worlds | 6 pages | Int.J.Mod.Phys.A17:4355-4358,2002 | 10.1142/S0217751X02013411 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The topological structure of Schwarzschild's space-time and its maximal
analytic extension are investigated in context of brane-worlds. Using the
embedding coordinates, these geometries are seen as different states of the
evolution of a single brane-world. Comparing the topologies and the embeddings
it is shown that this evolution must be followed by a signature change in the
bulk.
| [
{
"created": "Fri, 13 Dec 2002 18:06:37 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Nov 2011 11:18:32 GMT",
"version": "v2"
}
] | 2011-11-30 | [
[
"Monte",
"Edmundo M.",
"",
"U.F.Paraiba"
],
[
"Maia",
"M. D.",
"",
"U.Brasilia"
]
] | The topological structure of Schwarzschild's space-time and its maximal analytic extension are investigated in context of brane-worlds. Using the embedding coordinates, these geometries are seen as different states of the evolution of a single brane-world. Comparing the topologies and the embeddings it is shown that this evolution must be followed by a signature change in the bulk. |
gr-qc/9707018 | null | Roy Maartens and Josep Triginer | Density perturbations with relativistic thermodynamics | Minor corrections to some equations. To appear Phys. Rev. D | Phys.Rev. D56 (1997) 4640-4650 | 10.1103/PhysRevD.56.4640 | null | gr-qc astro-ph | null | We investigate cosmological density perturbations in a covariant and
gauge-invariant formalism, incorporating relativistic causal thermodynamics to
give a self-consistent description. The gradient of density inhomogeneities
splits covariantly into a scalar part, equivalent to the usual density
perturbations, a rotational vector part that is determined by the vorticity,
and a tensor part that describes the shape. We give the evolution equations for
these parts in the general dissipative case. Causal thermodynamics gives
evolution equations for viscous stress and heat flux, which are coupled to the
density perturbation equation and to the entropy and temperature perturbation
equations. We give the full coupled system in the general dissipative case, and
simplify the system in certain cases. A companion paper uses the general
formalism to analyze damping of density perturbations before last scattering.
| [
{
"created": "Tue, 8 Jul 1997 16:24:43 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Sep 1997 08:33:50 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Maartens",
"Roy",
""
],
[
"Triginer",
"Josep",
""
]
] | We investigate cosmological density perturbations in a covariant and gauge-invariant formalism, incorporating relativistic causal thermodynamics to give a self-consistent description. The gradient of density inhomogeneities splits covariantly into a scalar part, equivalent to the usual density perturbations, a rotational vector part that is determined by the vorticity, and a tensor part that describes the shape. We give the evolution equations for these parts in the general dissipative case. Causal thermodynamics gives evolution equations for viscous stress and heat flux, which are coupled to the density perturbation equation and to the entropy and temperature perturbation equations. We give the full coupled system in the general dissipative case, and simplify the system in certain cases. A companion paper uses the general formalism to analyze damping of density perturbations before last scattering. |
2406.13521 | Gianluca Calcagni | Ido Ben-Dayan, Gianluca Calcagni, Maurizio Gasperini, Anupam Mazumdar,
Eliseo Pavone, Udaykrishna Thattarampilly, Amresh Verma | Gravitational-wave background in bouncing models from semi-classical,
quantum and string gravity | 1+33 pages, 4 figures | null | null | ET-0386A-24 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the primordial spectra and the gravitational-wave background (GWB)
of three models of semi-classical, quantum or string gravity where the big bang
is replaced by a bounce and the tensor spectrum is blue-tilted: ekpyrotic
universe with fast-rolling Galileons, string-gas cosmology with Atick-Witten
conjecture and pre-big-bang cosmology. We find that the ekpyrotic scenario does
not produce a GWB amplitude detectable by present or third-generation
interferometers, while the string-gas model is ruled out for producing too
large a signal. In contrast, the GWB of the pre-big-bang scenario falls within
the sensitivity window of both LISA and Einstein Telescope, where it takes the
form of a single or a broken power law depending on the choice of parameters.
The latter will be tightly constrained by both detectors.
| [
{
"created": "Wed, 19 Jun 2024 13:06:39 GMT",
"version": "v1"
}
] | 2024-06-21 | [
[
"Ben-Dayan",
"Ido",
""
],
[
"Calcagni",
"Gianluca",
""
],
[
"Gasperini",
"Maurizio",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Pavone",
"Eliseo",
""
],
[
"Thattarampilly",
"Udaykrishna",
""
],
[
"Verma",
"Amresh",
""
]
] | We study the primordial spectra and the gravitational-wave background (GWB) of three models of semi-classical, quantum or string gravity where the big bang is replaced by a bounce and the tensor spectrum is blue-tilted: ekpyrotic universe with fast-rolling Galileons, string-gas cosmology with Atick-Witten conjecture and pre-big-bang cosmology. We find that the ekpyrotic scenario does not produce a GWB amplitude detectable by present or third-generation interferometers, while the string-gas model is ruled out for producing too large a signal. In contrast, the GWB of the pre-big-bang scenario falls within the sensitivity window of both LISA and Einstein Telescope, where it takes the form of a single or a broken power law depending on the choice of parameters. The latter will be tightly constrained by both detectors. |
gr-qc/9808051 | Klemm Dietmar | Dietmar Klemm | Topological Black Holes in Weyl Conformal Gravity | 9 pages, revtex, no figures. To appear in Classical and Quantum
Gravity | Class.Quant.Grav. 15 (1998) 3195-3201 | 10.1088/0264-9381/15/10/020 | UTF 414 | gr-qc | null | We present a class of exact solutions of Weyl conformal gravity, which have
an interpretation as topological black holes. Solutions with negative, zero or
positive scalar curvature at infinity are found, the former generalizing the
well-known topological black holes in anti-de Sitter gravity. The rather
delicate question of thermodynamic properties of such objects in Weyl conformal
gravity is discussed; suggesting that the thermodynamics of the found solutions
should be treated within the framework of gravity as an induced phenomenon, in
the spirit of Sakharov's work.
| [
{
"created": "Wed, 19 Aug 1998 11:43:27 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Klemm",
"Dietmar",
""
]
] | We present a class of exact solutions of Weyl conformal gravity, which have an interpretation as topological black holes. Solutions with negative, zero or positive scalar curvature at infinity are found, the former generalizing the well-known topological black holes in anti-de Sitter gravity. The rather delicate question of thermodynamic properties of such objects in Weyl conformal gravity is discussed; suggesting that the thermodynamics of the found solutions should be treated within the framework of gravity as an induced phenomenon, in the spirit of Sakharov's work. |
1605.06390 | Fredy Dubeibe | F. L. Dubeibe and Jos\'e D. Sanabria-G\'omez | Geodesic motion in a stationary dihole spacetime | 10 pages, 9 figures | Phys. Rev. D 94, 044058 (2016) | 10.1103/PhysRevD.94.044058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The knowledge of the properties of the different exact solutions modeling
binary systems, is a necessary step towards the classification of physically
suitable solutions and its corresponding limits of applicability. In the
present paper, we perform an analysis of the geodesics around two
counter--rotating Kerr--Newman black holes endowed with opposite electric
charges, which achieve equilibrium by means of a strut between their
constituents. We find that bounded and unbounded orbits are possible. However,
test particles may cross between the black holes only if their angular momentum
equals zero, otherwise, there exist a repulsive potential, which prohibits such
orbits. Two important aspects are pointed out for these trajectories: ({\it i})
the motion of photons is affected once crossing the strut; and ({\it ii})
massive particles exhibit oscillatory motion, as a first analog of the Sitnikov
problem in general relativity. The radius of the innermost stable circular
orbit as a function of the physical parameters of the black holes is also
investigated.
| [
{
"created": "Fri, 20 May 2016 15:01:42 GMT",
"version": "v1"
}
] | 2016-09-07 | [
[
"Dubeibe",
"F. L.",
""
],
[
"Sanabria-Gómez",
"José D.",
""
]
] | The knowledge of the properties of the different exact solutions modeling binary systems, is a necessary step towards the classification of physically suitable solutions and its corresponding limits of applicability. In the present paper, we perform an analysis of the geodesics around two counter--rotating Kerr--Newman black holes endowed with opposite electric charges, which achieve equilibrium by means of a strut between their constituents. We find that bounded and unbounded orbits are possible. However, test particles may cross between the black holes only if their angular momentum equals zero, otherwise, there exist a repulsive potential, which prohibits such orbits. Two important aspects are pointed out for these trajectories: ({\it i}) the motion of photons is affected once crossing the strut; and ({\it ii}) massive particles exhibit oscillatory motion, as a first analog of the Sitnikov problem in general relativity. The radius of the innermost stable circular orbit as a function of the physical parameters of the black holes is also investigated. |
2010.13394 | Yiding Jia | Lina Wu, Qing Gao, Yungui Gong, Yiding Jia and Tianjun Li | The Upper Bound on the Tensor-to-Scalar Ratio Consistent with Quantum
Gravity | 12 pages | null | 10.1088/1572-9494/abf824 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the polynomial inflation with the tensor-to-scalar ratio as large
as possible which can be consistent with the Quantum Gravity (QG) corrections
and Effective Field Theory (EFT). To get a minimal field excursion $\Delta\phi$
for enough e-folding number $N$, the inflaton field traverses an extremely flat
part of the scalar potential, which results in the Lyth bound to be violated.
We get a CMB signal consistent with Planck data by numerically computing the
equation of motion for inflaton $\phi$ and using Mukhanov-Sasaki formalism for
primordial spectrum. Inflation ends at Hubble slow-roll parameter
$\epsilon_1^H=1$ or $\ddot{a}=0$. Interestingly, we find an excellent practical
bound on the inflaton excursion in the format $a+b{\sqrt r}$, where $a$ is a
tiny real number and $b$ is at the order 1. To be consistent with QG/EFT and
suppress the high-dimensional operators, we show that the concrete condition on
inflaton excursion is $\frac{\Delta \phi}{M_{\rm Pl}} < 0.2 \times
\sqrt{10}\simeq 0.632$. For $n_s=0.9649$, $N_e=55$, and $\frac{\Delta
\phi}{M_{\rm Pl}} < 0.632$, we predict that the tensor-to-scalar ratio is
smaller than 0.0012 for such polynomial inflation to be consistent with QG/EFT.
| [
{
"created": "Mon, 26 Oct 2020 07:43:31 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Wu",
"Lina",
""
],
[
"Gao",
"Qing",
""
],
[
"Gong",
"Yungui",
""
],
[
"Jia",
"Yiding",
""
],
[
"Li",
"Tianjun",
""
]
] | We consider the polynomial inflation with the tensor-to-scalar ratio as large as possible which can be consistent with the Quantum Gravity (QG) corrections and Effective Field Theory (EFT). To get a minimal field excursion $\Delta\phi$ for enough e-folding number $N$, the inflaton field traverses an extremely flat part of the scalar potential, which results in the Lyth bound to be violated. We get a CMB signal consistent with Planck data by numerically computing the equation of motion for inflaton $\phi$ and using Mukhanov-Sasaki formalism for primordial spectrum. Inflation ends at Hubble slow-roll parameter $\epsilon_1^H=1$ or $\ddot{a}=0$. Interestingly, we find an excellent practical bound on the inflaton excursion in the format $a+b{\sqrt r}$, where $a$ is a tiny real number and $b$ is at the order 1. To be consistent with QG/EFT and suppress the high-dimensional operators, we show that the concrete condition on inflaton excursion is $\frac{\Delta \phi}{M_{\rm Pl}} < 0.2 \times \sqrt{10}\simeq 0.632$. For $n_s=0.9649$, $N_e=55$, and $\frac{\Delta \phi}{M_{\rm Pl}} < 0.632$, we predict that the tensor-to-scalar ratio is smaller than 0.0012 for such polynomial inflation to be consistent with QG/EFT. |
1407.2446 | Mariam Bouhmadi-Lopez | Mariam Bouhmadi-Lopez, Ahmed Errahmani, Prado Martin-Moruno, Taoufik
Ouali, Yaser Tavakoli | The little sibling of the big rip singularity | 20 pages, 4 figures, clarifications included | Int.J.Mod.Phys.D Vol. 24, No. 10 (2015) 1550078 (20 pages) | 10.1142/S0218271815500789 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new cosmological event, which we named the little sibling of the
big rip. This event is much smoother than the big rip singularity. When the
little sibling of the big rip is reached, the Hubble rate and the scale factor
blow up but the cosmic derivative of the Hubble rate does not. This abrupt
event takes place at an infinite cosmic time where the scalar curvature
explodes. We show that a doomsday \'a la little sibling of the big rip is
compatible with an accelerating universe, indeed at present it would mimic
perfectly a LCDM scenario. It turns out that eventhough the event seems to be
harmless as it takes place in the infinite future, the bound structures in the
universe would be unavoidably destroyed on a finite cosmic time from now. The
model can be motivated by considering that the weak energy condition should not
be abusibely violated in our Universe, and it could give us some hints about
the status of recently formulated nonlinear energy conditions.
| [
{
"created": "Wed, 9 Jul 2014 12:01:57 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jun 2015 08:01:53 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Errahmani",
"Ahmed",
""
],
[
"Martin-Moruno",
"Prado",
""
],
[
"Ouali",
"Taoufik",
""
],
[
"Tavakoli",
"Yaser",
""
]
] | We present a new cosmological event, which we named the little sibling of the big rip. This event is much smoother than the big rip singularity. When the little sibling of the big rip is reached, the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not. This abrupt event takes place at an infinite cosmic time where the scalar curvature explodes. We show that a doomsday \'a la little sibling of the big rip is compatible with an accelerating universe, indeed at present it would mimic perfectly a LCDM scenario. It turns out that eventhough the event seems to be harmless as it takes place in the infinite future, the bound structures in the universe would be unavoidably destroyed on a finite cosmic time from now. The model can be motivated by considering that the weak energy condition should not be abusibely violated in our Universe, and it could give us some hints about the status of recently formulated nonlinear energy conditions. |
gr-qc/0012010 | Hideyuki Tagoshi | Hideyuki Tagoshi, Nobuyuki Kanda, Takahiro Tanaka, Daisuke Tatsumi,
Souichi Telada, et al. (The TAMA Collaboration) | The First Search for Gravitational Waves from Inspiraling Compact
Binaries using TAMA300 data | 5 pages, 4 figures. To appear Phsical Review D | Phys.Rev.D63:062001,2001 | 10.1103/PhysRevD.63.062001 | ICRR-Report-469-2000-13, OU-TAP-153 | gr-qc astro-ph | null | We analyzed 6 hours of data from the TAMA300 detector by matched filtering,
searching for gravitational waves from inspiraling compact binaries. We
incorporated a two-step hierarchical search strategy in matched filtering. We
obtained an upper limit of 0.59/hour (C.L.=90%) on the event rate of inspirals
of compact binaries with mass between 0.3M_solar and 10M_solar and with
signal-to-noise ratio greater than 7.2. The distance of 1.4M_solar (0.5M_solar)
binaries which produce the signal-to-noise ratio 7.2 was estimated to be 6.2kpc
(2.9kpc) when the position of the source on the sky and the inclination angle
of the binaries were optimal.
| [
{
"created": "Mon, 4 Dec 2000 08:10:06 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Tagoshi",
"Hideyuki",
""
],
[
"Kanda",
"Nobuyuki",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Tatsumi",
"Daisuke",
""
],
[
"Telada",
"Souichi",
""
]
] | We analyzed 6 hours of data from the TAMA300 detector by matched filtering, searching for gravitational waves from inspiraling compact binaries. We incorporated a two-step hierarchical search strategy in matched filtering. We obtained an upper limit of 0.59/hour (C.L.=90%) on the event rate of inspirals of compact binaries with mass between 0.3M_solar and 10M_solar and with signal-to-noise ratio greater than 7.2. The distance of 1.4M_solar (0.5M_solar) binaries which produce the signal-to-noise ratio 7.2 was estimated to be 6.2kpc (2.9kpc) when the position of the source on the sky and the inclination angle of the binaries were optimal. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.