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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2005.07260 | Mauricio Bellini | Mauricio Bellini (IFIMAR - CONICET & UNMdP) | Quantum magnetic monopoles at the Planck era from unified spinor fields | Published in Phys. Dark Univ | Phys. Dark Univ. 30: 100693 (2020) | 10.1016/j.dark.2020.100693 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I use Unified Spinor Fields (USF), to discuss the creation of magnetic
monopoles during preinflation, as excitations of the quantum vacuum coming from
a condensate of massive charged vector bosons. For a primordial universe with
total energy $M_p$, and for magnetic monopoles created with a total Planck
magnetic charge $q_M=q_P=\pm e/\sqrt{\alpha}$ and a total mass $m_M$, it is
obtained after quantisation of the action that the fine-structure constant is
given by: $\alpha= \frac{5}{6} \left(1- \frac{16 \,m_M}{5 \,M_p}\right)
\,\left(\frac{e}{q_M}\right)^2$. If these magnetic monopoles were with total
magnetic charge $q_M=\pm e$ and a small mass $m=m_M/n$, there would be a large
number of small quantum magnetic monopoles which could be candidates to explain
the presence of dark matter with a $30.97\,\%$ of the energy in the primordial
universe at the Planck era. The case of milli-magnetically charged particles is
also analysed. We demonstrate that magnetic monopoles (MM) with masses less
than $3.6\times 10^3$ GeV, can exist with a very small charges of up to
$10^{-14}\,e$, which are quantities of interest for searches to be performed in
the ATLAS and MoEDAL experiments.
| [
{
"created": "Thu, 14 May 2020 21:10:45 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jun 2020 13:44:51 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Aug 2020 13:20:09 GMT",
"version": "v3"
}
] | 2020-08-04 | [
[
"Bellini",
"Mauricio",
"",
"IFIMAR - CONICET & UNMdP"
]
] | I use Unified Spinor Fields (USF), to discuss the creation of magnetic monopoles during preinflation, as excitations of the quantum vacuum coming from a condensate of massive charged vector bosons. For a primordial universe with total energy $M_p$, and for magnetic monopoles created with a total Planck magnetic charge $q_M=q_P=\pm e/\sqrt{\alpha}$ and a total mass $m_M$, it is obtained after quantisation of the action that the fine-structure constant is given by: $\alpha= \frac{5}{6} \left(1- \frac{16 \,m_M}{5 \,M_p}\right) \,\left(\frac{e}{q_M}\right)^2$. If these magnetic monopoles were with total magnetic charge $q_M=\pm e$ and a small mass $m=m_M/n$, there would be a large number of small quantum magnetic monopoles which could be candidates to explain the presence of dark matter with a $30.97\,\%$ of the energy in the primordial universe at the Planck era. The case of milli-magnetically charged particles is also analysed. We demonstrate that magnetic monopoles (MM) with masses less than $3.6\times 10^3$ GeV, can exist with a very small charges of up to $10^{-14}\,e$, which are quantities of interest for searches to be performed in the ATLAS and MoEDAL experiments. |
2201.12317 | Alex Pandya | Alex Pandya, Elias R. Most, and Frans Pretorius | Conservative finite volume scheme for first-order viscous relativistic
hydrodynamics | 24 pages, 9 figures; updated to match published version | null | 10.1103/PhysRevD.105.123001 | null | gr-qc astro-ph.HE nucl-th physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first conservative finite volume numerical scheme for the
causal, stable relativistic Navier-Stokes equations developed by Bemfica,
Disconzi, Noronha, and Kovtun (BDNK). BDNK theory has arisen very recently as a
promising means of incorporating entropy-generating effects (viscosity, heat
conduction) into relativistic fluid models, appearing as a possible alternative
to the so-called M\"uller-Israel-Stewart (MIS) theory successfully used to
model quark-gluon plasma. The major difference between the two lies in the
structure of the system of PDEs: BDNK theory only has a set of conservation
laws, whereas MIS also includes a set of evolution equations for its
dissipative degrees of freedom. The simpler structure of the BDNK PDEs in this
respect allows for rigorous proofs of stability, causality, and hyperbolicity
in full generality which have as yet been impossible for MIS. To capitalize on
these advantages, we present the first fully conservative multi-dimensional
fluid solver for the BDNK equations suitable for physical applications. The
scheme includes a flux-conservative discretization, non-oscillatory
reconstruction, and a central-upwind numerical flux, and is designed to
smoothly transition to a high-resolution shock-capturing perfect fluid solver
in the inviscid limit. We assess the robustness of our new method in a series
of flat-spacetime tests for a conformal fluid, and provide a detailed
comparison with previous approaches of Pandya & Pretorius (2021).
| [
{
"created": "Fri, 28 Jan 2022 18:30:38 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 01:01:54 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Jun 2022 01:21:18 GMT",
"version": "v3"
}
] | 2022-06-15 | [
[
"Pandya",
"Alex",
""
],
[
"Most",
"Elias R.",
""
],
[
"Pretorius",
"Frans",
""
]
] | We present the first conservative finite volume numerical scheme for the causal, stable relativistic Navier-Stokes equations developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK). BDNK theory has arisen very recently as a promising means of incorporating entropy-generating effects (viscosity, heat conduction) into relativistic fluid models, appearing as a possible alternative to the so-called M\"uller-Israel-Stewart (MIS) theory successfully used to model quark-gluon plasma. The major difference between the two lies in the structure of the system of PDEs: BDNK theory only has a set of conservation laws, whereas MIS also includes a set of evolution equations for its dissipative degrees of freedom. The simpler structure of the BDNK PDEs in this respect allows for rigorous proofs of stability, causality, and hyperbolicity in full generality which have as yet been impossible for MIS. To capitalize on these advantages, we present the first fully conservative multi-dimensional fluid solver for the BDNK equations suitable for physical applications. The scheme includes a flux-conservative discretization, non-oscillatory reconstruction, and a central-upwind numerical flux, and is designed to smoothly transition to a high-resolution shock-capturing perfect fluid solver in the inviscid limit. We assess the robustness of our new method in a series of flat-spacetime tests for a conformal fluid, and provide a detailed comparison with previous approaches of Pandya & Pretorius (2021). |
gr-qc/0612020 | Alexei Zayats | Alexander B. Balakin, Alexei E. Zayats | Curvature coupling in Einstein-Yang-Mills theory and non-minimal
self-duality | 6 pages, no figures, accepted for publication in Gravitation and
Cosmology | Grav.Cosmol.12:302-306,2006 | null | null | gr-qc astro-ph hep-ph hep-th | null | A self-consistent non-minimal non-Abelian Einstein-Yang-Mills model,
containing three phenomenological coupling constants, is formulated. The ansatz
of a vanishing Yang-Mills induction is considered as a particular case of the
self-duality requirement for the gauge field. Such an ansatz is shown to allow
obtaining an exact solution of the self-consistent set of equations when the
space-time has a constant curvature. An example describing a pure magnetic
gauge field in the de Sitter cosmological model is discussed in detail.
| [
{
"created": "Sun, 3 Dec 2006 12:23:18 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Dec 2006 13:54:32 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Zayats",
"Alexei E.",
""
]
] | A self-consistent non-minimal non-Abelian Einstein-Yang-Mills model, containing three phenomenological coupling constants, is formulated. The ansatz of a vanishing Yang-Mills induction is considered as a particular case of the self-duality requirement for the gauge field. Such an ansatz is shown to allow obtaining an exact solution of the self-consistent set of equations when the space-time has a constant curvature. An example describing a pure magnetic gauge field in the de Sitter cosmological model is discussed in detail. |
1606.06627 | Jeremy Sakstein | Eugeny Babichev, Kazuya Koyama, David Langlois, Ryo Saito, Jeremy
Sakstein | Relativistic Stars in Beyond Horndeski Theories | 13 pages, five figures. Updated to reflect published version. Results
unchanged but added plots for positive Upsilon | 2016 Class. Quantum Grav. 33 235014 | 10.1088/0264-9381/33/23/235014 | YITP-16-76, LPT-Orsay-16-46 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work studies relativistic stars in beyond Horndeski scalar-tensor
theories that exhibit a breaking of the Vainshtein mechanism inside matter,
focusing on a model based on the quartic beyond Horndeski Lagrangian. We
self-consistently derive the scalar field profile for static spherically
symmetric objects in asymptotically de Sitter space-time and show that the
Vainshtein breaking branch of the solutions is the physical branch thereby
resolving several ambiguities with non-relativistic frameworks. The geometry
outside the star is shown to be exactly Schwarzschild-de Sitter and therefore
the PPN parameter $\beta_{\rm PPN}=1$, confirming that the external screening
works at the post-Newtonian level. The Tolman-Oppenheimer-Volkoff (TOV)
equations are derived and a new lower bound on the Vainshtein breaking
parameter $\Upsilon_1>-4/9$ is found by requiring the existence of static
spherically symmetric stars. Focusing on the unconstrained case where
$\Upsilon_1<0$, we numerically solve the TOV equations for polytropic and
realistic equations of state and find stars with larger radii at fixed mass.
Furthermore, the maximum mass can increase dramatically and stars with masses
in excess of $3M_\odot$ can be found for relatively small values of the
Vainshtein breaking parameter. We re-examine white dwarf stars and show that
post-Newtonian corrections are important in beyond Horndeski theories and
therefore the bounds coming from previous analyses should be revisited.
| [
{
"created": "Tue, 21 Jun 2016 15:51:53 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Oct 2016 16:05:12 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Nov 2016 14:14:30 GMT",
"version": "v3"
}
] | 2016-11-16 | [
[
"Babichev",
"Eugeny",
""
],
[
"Koyama",
"Kazuya",
""
],
[
"Langlois",
"David",
""
],
[
"Saito",
"Ryo",
""
],
[
"Sakstein",
"Jeremy",
""
]
] | This work studies relativistic stars in beyond Horndeski scalar-tensor theories that exhibit a breaking of the Vainshtein mechanism inside matter, focusing on a model based on the quartic beyond Horndeski Lagrangian. We self-consistently derive the scalar field profile for static spherically symmetric objects in asymptotically de Sitter space-time and show that the Vainshtein breaking branch of the solutions is the physical branch thereby resolving several ambiguities with non-relativistic frameworks. The geometry outside the star is shown to be exactly Schwarzschild-de Sitter and therefore the PPN parameter $\beta_{\rm PPN}=1$, confirming that the external screening works at the post-Newtonian level. The Tolman-Oppenheimer-Volkoff (TOV) equations are derived and a new lower bound on the Vainshtein breaking parameter $\Upsilon_1>-4/9$ is found by requiring the existence of static spherically symmetric stars. Focusing on the unconstrained case where $\Upsilon_1<0$, we numerically solve the TOV equations for polytropic and realistic equations of state and find stars with larger radii at fixed mass. Furthermore, the maximum mass can increase dramatically and stars with masses in excess of $3M_\odot$ can be found for relatively small values of the Vainshtein breaking parameter. We re-examine white dwarf stars and show that post-Newtonian corrections are important in beyond Horndeski theories and therefore the bounds coming from previous analyses should be revisited. |
1206.5341 | Luis P. Chimento | Mario Castagnino and Luis Chimento | Two Theorems on Flat Space-Time Gravitational Theories | 11 pages | General Relativity and Gravitation, Vol. 12, No. 10, 825, 1980 | 10.1007/BF00763058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first theorem states that all flat space-time gravitational theories must
have a Lagrangian with a first term that is an homogeneous (degree-I) function
of the 4-velocity $u^i$, plus a functional of $\eta_{ij}u^i u^j$. The second
theorem states that all gravitational theories that satisfy the strong
equivalence principle have a Lagrangian with a first term $g_{ij}(x)u^i u^j$
plus an irrelevant term. In both cases the theories must issue from a unique
variational principle. Therefore, under this condition it is impossible to find
a flat space-time theory that satisfies the strong equivalence principle.
| [
{
"created": "Sat, 23 Jun 2012 00:00:17 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Castagnino",
"Mario",
""
],
[
"Chimento",
"Luis",
""
]
] | The first theorem states that all flat space-time gravitational theories must have a Lagrangian with a first term that is an homogeneous (degree-I) function of the 4-velocity $u^i$, plus a functional of $\eta_{ij}u^i u^j$. The second theorem states that all gravitational theories that satisfy the strong equivalence principle have a Lagrangian with a first term $g_{ij}(x)u^i u^j$ plus an irrelevant term. In both cases the theories must issue from a unique variational principle. Therefore, under this condition it is impossible to find a flat space-time theory that satisfies the strong equivalence principle. |
1408.4635 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Quantum shells in a quantum space-time | 5 pages, 3 figures | null | 10.1088/0264-9381/32/3/035003 | LSU-REL-082014 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum motion of null shells in the quantum space-time of a
black hole in loop quantum gravity. We treat the shells as test fields and use
an effective dynamics for the propagation equations. The shells propagate
through the region where the singularity was present in the classical black
hole space-time, but is absent in the quantum space-time, eventually emerging
through a white hole to a new asymptotic region of the quantum space-time. The
profiles of the shells get distorted due to the quantum fluctuations in the
Planckian region that replaces the singularity. The evolution of the shells is
unitary throughout the whole process.
| [
{
"created": "Wed, 20 Aug 2014 12:54:10 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We study the quantum motion of null shells in the quantum space-time of a black hole in loop quantum gravity. We treat the shells as test fields and use an effective dynamics for the propagation equations. The shells propagate through the region where the singularity was present in the classical black hole space-time, but is absent in the quantum space-time, eventually emerging through a white hole to a new asymptotic region of the quantum space-time. The profiles of the shells get distorted due to the quantum fluctuations in the Planckian region that replaces the singularity. The evolution of the shells is unitary throughout the whole process. |
1702.00909 | Hee-Suk Cho | Hee-Suk Cho | Systematic Bias Due to Nonspinning Template Waveforms in the
Gravitational Wave Parameter Estimation for Aligned-Spin Binary Black Holes | 5 pages, 2 figures, updated to match published version | JKPS 70, 735 (2017) | 10.3938/jkps.70.735 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the parameter estimation of gravitational waves for aligned-spin
binary black hole (BBH) signals and assess the impact of bias that can be
produced by using nonspinning template waveforms. We employ simple methods to
calculate the statistical uncertainty from an overlap distribution. For the
fiducial waveform model, we use a phenomenological model, which is designed to
generate the gravitational waveforms emitted from merging BBH systems. We show
that the mass parameters recovered by nonspinning waveform templates can be
significantly biased from the true values of aligned-spin signals. By comparing
the systematic bias with the statistical uncertainty, we examine the validity
of nonspinning templates for the parameter estimation of aligned-spin BBHs.
| [
{
"created": "Fri, 3 Feb 2017 05:33:19 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2017 04:14:21 GMT",
"version": "v2"
}
] | 2017-04-12 | [
[
"Cho",
"Hee-Suk",
""
]
] | We study the parameter estimation of gravitational waves for aligned-spin binary black hole (BBH) signals and assess the impact of bias that can be produced by using nonspinning template waveforms. We employ simple methods to calculate the statistical uncertainty from an overlap distribution. For the fiducial waveform model, we use a phenomenological model, which is designed to generate the gravitational waveforms emitted from merging BBH systems. We show that the mass parameters recovered by nonspinning waveform templates can be significantly biased from the true values of aligned-spin signals. By comparing the systematic bias with the statistical uncertainty, we examine the validity of nonspinning templates for the parameter estimation of aligned-spin BBHs. |
2110.07056 | D. Ghilencea | D. M. Ghilencea, T. Harko | Cosmological evolution in Weyl conformal geometry | 23 pages, LaTeX, 4 figures | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the cosmological evolution of the Weyl conformal geometry and its
associated Weyl quadratic gravity. The Einstein gravity (with a positive
cosmological constant) is recovered in the spontaneously broken phase of Weyl
gravity; this happens after the Weyl gauge field ($\omega_\mu$) of scale
symmetry, that is part of the Weyl geometry, becomes massive by Stueckelberg
mechanism and then decouples. This breaking is a natural result of the
cosmological evolution of Weyl geometry, in the absence of matter. Of
particular interest in the analysis is the special limiting case of Weyl
integrable geometry. Both this case and the general one provide an accelerated
expansion of the Universe, controlled by the scalar mode of the $\tilde R^2$
term in the action and by $\omega_0$. Their comparison to the $\Lambda$CDM
model shows a very good agreement to this model for the (dimensionless) Hubble
function $h(z)$ and the deceleration $q(z)$ for redshift $z\leq 3$. Therefore,
the Weyl conformal geometry and its associated Weyl quadratic gravity provide
an interesting alternative to the $\Lambda$CDM model and to the Einstein
gravity.
| [
{
"created": "Wed, 13 Oct 2021 22:16:45 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2022 22:29:01 GMT",
"version": "v2"
}
] | 2022-06-24 | [
[
"Ghilencea",
"D. M.",
""
],
[
"Harko",
"T.",
""
]
] | We discuss the cosmological evolution of the Weyl conformal geometry and its associated Weyl quadratic gravity. The Einstein gravity (with a positive cosmological constant) is recovered in the spontaneously broken phase of Weyl gravity; this happens after the Weyl gauge field ($\omega_\mu$) of scale symmetry, that is part of the Weyl geometry, becomes massive by Stueckelberg mechanism and then decouples. This breaking is a natural result of the cosmological evolution of Weyl geometry, in the absence of matter. Of particular interest in the analysis is the special limiting case of Weyl integrable geometry. Both this case and the general one provide an accelerated expansion of the Universe, controlled by the scalar mode of the $\tilde R^2$ term in the action and by $\omega_0$. Their comparison to the $\Lambda$CDM model shows a very good agreement to this model for the (dimensionless) Hubble function $h(z)$ and the deceleration $q(z)$ for redshift $z\leq 3$. Therefore, the Weyl conformal geometry and its associated Weyl quadratic gravity provide an interesting alternative to the $\Lambda$CDM model and to the Einstein gravity. |
gr-qc/0306034 | Konstantina Savvidou | Ntina Savvidou | General relativity histories theory I: The spacetime character of the
canonical description | 23 pages, submitted to Class. Quant. Grav | Class.Quant.Grav. 21 (2004) 615 | 10.1088/0264-9381/21/2/020 | IMPERIAL/TP/2-03/16 | gr-qc hep-th math-ph math.MP quant-ph | null | The problem of time in canonical quantum gravity is related to the fact that
the canonical description is based on the prior choice of a spacelike
foliation, hence making a reference to a spacetime metric. However, the metric
is expected to be a dynamical, fluctuating quantity in quantum gravity. We show
how this problem can be solved in the histories formulation of general
relativity. We implement the 3+1 decomposition using metric-dependent
foliations which remain spacelike with respect to all possible Lorentzian
metrics. This allows us to find an explicit relation of covariant and canonical
quantities which preserves the spacetime character of the canonical
description. In this new construction, we also have a coexistence of the
spacetime diffeomorphisms group, and the Dirac algebra of constraints.
| [
{
"created": "Mon, 9 Jun 2003 15:26:50 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Savvidou",
"Ntina",
""
]
] | The problem of time in canonical quantum gravity is related to the fact that the canonical description is based on the prior choice of a spacelike foliation, hence making a reference to a spacetime metric. However, the metric is expected to be a dynamical, fluctuating quantity in quantum gravity. We show how this problem can be solved in the histories formulation of general relativity. We implement the 3+1 decomposition using metric-dependent foliations which remain spacelike with respect to all possible Lorentzian metrics. This allows us to find an explicit relation of covariant and canonical quantities which preserves the spacetime character of the canonical description. In this new construction, we also have a coexistence of the spacetime diffeomorphisms group, and the Dirac algebra of constraints. |
0810.5039 | Marco Valerio Battisti | Marco Valerio Battisti | Deformed spaces and loop cosmology | 5 pages, talk given at NEB-XIII Recent Developments in Gravity,
Thessaloniki June 2008 | J.Phys.Conf.Ser.189:012005,2009 | 10.1088/1742-6596/189/1/012005 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | The non-singular bouncing solution of loop quantum cosmology is reproduced by
a deformed minisuperspace Heisenberg algebra. This algebra is a realization of
the Snyder space, is almost unique and is related to the $\kappa$-Poincar\'e
one. Since the sign of the deformation parameter it is not fixed, the Friedmann
equation of braneworlds theory can also be obtained. Moreover, the sign is the
only freedom in the picture and these frameworks are the only ones which can be
reproduced by our deformed scheme. A generalized uncertainty principle for loop
quantum cosmology is also proposed.
| [
{
"created": "Tue, 28 Oct 2008 14:35:20 GMT",
"version": "v1"
}
] | 2009-11-05 | [
[
"Battisti",
"Marco Valerio",
""
]
] | The non-singular bouncing solution of loop quantum cosmology is reproduced by a deformed minisuperspace Heisenberg algebra. This algebra is a realization of the Snyder space, is almost unique and is related to the $\kappa$-Poincar\'e one. Since the sign of the deformation parameter it is not fixed, the Friedmann equation of braneworlds theory can also be obtained. Moreover, the sign is the only freedom in the picture and these frameworks are the only ones which can be reproduced by our deformed scheme. A generalized uncertainty principle for loop quantum cosmology is also proposed. |
2202.12463 | Pedro Mario Ca\~nate Casseres | Pedro Ca\~nate, F. H. Maldonado-Villamizar | Novel traversable wormhole in General Relativity and
Einstein-Scalar-Gauss-Bonnet theory supported by nonlinear electrodynamics | 22 pages, 4 figures | null | 10.1103/PhysRevD.106.044063 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several traversable wormholes (T-WHs) of the Morris-Thorne type have been
presented as exact solutions of Einstein-nonlinear electrodynamics gravity
(GR-NLED), e.g. \cite{Arellano2009, Bronnikov2018,Bronnikov_Walia2021,
Canate_Breton2018, Canate_Breton_Ortiz2020, Canate_Magos_Breton2020}. However,
none of these solutions is support by a nonlinear electrodynamics model
satisfying plausible conditions. In this work, we present the first traversable
wormhole solution of Einstein-nonlinear electrodynamics gravity coupled to a
self-interacting phantom scalar field (GR-NLED-SF) with a NLED model such that
in the limit of weak field becomes the Maxwell electrodynamics, is presented.
Furthermore, we show that this novel T-WH spacetime is also an exact solution
of the Einstein-scalar-Gauss-Bonnet (EsGB) theory with a nonlinear
electrodynamics source, but now with a real scalar field having a positive
kinetic term.
| [
{
"created": "Fri, 25 Feb 2022 02:34:53 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Aug 2022 21:26:10 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Cañate",
"Pedro",
""
],
[
"Maldonado-Villamizar",
"F. H.",
""
]
] | Several traversable wormholes (T-WHs) of the Morris-Thorne type have been presented as exact solutions of Einstein-nonlinear electrodynamics gravity (GR-NLED), e.g. \cite{Arellano2009, Bronnikov2018,Bronnikov_Walia2021, Canate_Breton2018, Canate_Breton_Ortiz2020, Canate_Magos_Breton2020}. However, none of these solutions is support by a nonlinear electrodynamics model satisfying plausible conditions. In this work, we present the first traversable wormhole solution of Einstein-nonlinear electrodynamics gravity coupled to a self-interacting phantom scalar field (GR-NLED-SF) with a NLED model such that in the limit of weak field becomes the Maxwell electrodynamics, is presented. Furthermore, we show that this novel T-WH spacetime is also an exact solution of the Einstein-scalar-Gauss-Bonnet (EsGB) theory with a nonlinear electrodynamics source, but now with a real scalar field having a positive kinetic term. |
1912.06143 | Axel Polaczek | Steffen Gielen, Axel Polaczek | Generalised effective cosmology from group field theory | 38 pages, 5 figures; v2: improved discussion, added references,
additional figure | Class. Quantum Grav. 37 (2020), 165004 | 10.1088/1361-6382/ab8f67 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend various recent results regarding the derivation of effective
cosmological Friedmann equations from the dynamics of group field theory (GFT).
Restricting ourselves to a single GFT field mode (or fixed values of Peter-Weyl
representation labels), we first consider dynamics given by a quadratic
Hamiltonian, which takes the form of a squeezing operator, and then add a
quartic interaction that can be seen as a toy model for interactions in full
GFT. Our derivation of effective Friedmann equations does not require a
mean-field approximation; we mostly follow a general approach in which these
equations in fact hold for any state. The resulting cosmological equations
exhibit corrections to classical Friedmann dynamics similar to those of loop
quantum cosmology, leading to generic singularity resolution, but also involve
further state-dependent terms. We then specify these equations to various types
of coherent states, such as Fock coherent states or Perelomov-Gilmore states
based on the su(1,1) structure of harmonic quantum cosmology. We compute
relative uncertainties of volume and energy in these states, clarifying whether
they can be interpreted as semiclassical. In the interacting case, both
analytical and numerical approximations are used to obtain modified
cosmological dynamics. Our results clarify how effective cosmological equations
derived from GFT can provide reliable approximations to the full dynamics.
| [
{
"created": "Thu, 12 Dec 2019 19:00:01 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jun 2020 07:18:24 GMT",
"version": "v2"
}
] | 2022-01-11 | [
[
"Gielen",
"Steffen",
""
],
[
"Polaczek",
"Axel",
""
]
] | We extend various recent results regarding the derivation of effective cosmological Friedmann equations from the dynamics of group field theory (GFT). Restricting ourselves to a single GFT field mode (or fixed values of Peter-Weyl representation labels), we first consider dynamics given by a quadratic Hamiltonian, which takes the form of a squeezing operator, and then add a quartic interaction that can be seen as a toy model for interactions in full GFT. Our derivation of effective Friedmann equations does not require a mean-field approximation; we mostly follow a general approach in which these equations in fact hold for any state. The resulting cosmological equations exhibit corrections to classical Friedmann dynamics similar to those of loop quantum cosmology, leading to generic singularity resolution, but also involve further state-dependent terms. We then specify these equations to various types of coherent states, such as Fock coherent states or Perelomov-Gilmore states based on the su(1,1) structure of harmonic quantum cosmology. We compute relative uncertainties of volume and energy in these states, clarifying whether they can be interpreted as semiclassical. In the interacting case, both analytical and numerical approximations are used to obtain modified cosmological dynamics. Our results clarify how effective cosmological equations derived from GFT can provide reliable approximations to the full dynamics. |
2008.11396 | Jian-dong Zhang | Miaoxin Liu, Jian-dong Zhang | Augmented analytic kludge waveform with quadrupole moment correction | 9 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most important sources for future space-borne gravitational wave
detectors such as TianQin and LISA is EMRI. It happens when a stellar orgin
compact object orbiting around a massive black hole(MBH) in the center of
galaxies and has many benefits in the study of astrophysics and fundamental
theories. One of the most important objectives is to test the no-hair theorem
by measuring the quadrupole moment of the MBH. This requires us to estimate the
parameters of an EMRI system accurately enough, which means we also need an
accurate waveform templet for this process. Based on the fast and fiducial
augmented analytic kludge (AAK) waveform for the standard Kerr black hole, we
develop a waveform model for a metric with non-Kerr quadrupole moment. We also
analyze the accuracy of parameter estimation for different sources and
detectors.
| [
{
"created": "Wed, 26 Aug 2020 06:29:56 GMT",
"version": "v1"
}
] | 2020-08-27 | [
[
"Liu",
"Miaoxin",
""
],
[
"Zhang",
"Jian-dong",
""
]
] | One of the most important sources for future space-borne gravitational wave detectors such as TianQin and LISA is EMRI. It happens when a stellar orgin compact object orbiting around a massive black hole(MBH) in the center of galaxies and has many benefits in the study of astrophysics and fundamental theories. One of the most important objectives is to test the no-hair theorem by measuring the quadrupole moment of the MBH. This requires us to estimate the parameters of an EMRI system accurately enough, which means we also need an accurate waveform templet for this process. Based on the fast and fiducial augmented analytic kludge (AAK) waveform for the standard Kerr black hole, we develop a waveform model for a metric with non-Kerr quadrupole moment. We also analyze the accuracy of parameter estimation for different sources and detectors. |
1601.05809 | Benjamin Koch | Crist\'obal Armaza, Sergio A. Hojman, Benjamin Koch, and Nicol\'as
Zalaquett | On the Possibility of Non-Geodesic Motion of the Massless Spinning Top | 16 pages, no figures | null | 10.1088/0264-9381/33/14/145011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of spinning massless particles in gravitationally curved
backgrounds is revisited by considering new types of constraints. Those
constraints guarantee zero mass ($P_\mu P^\mu=0$) and they allow for the
possibility of trajectories which are not simply null geodesics. To exemplify
this previously unknown possibility, the equations of motion are solved for
radial motion in Schwarzschild background. It is found that the particle
experiences a spin-induced energy shift, which is proportional to the Hawking
temperature of the black hole background.
| [
{
"created": "Thu, 21 Jan 2016 21:00:39 GMT",
"version": "v1"
}
] | 2016-07-06 | [
[
"Armaza",
"Cristóbal",
""
],
[
"Hojman",
"Sergio A.",
""
],
[
"Koch",
"Benjamin",
""
],
[
"Zalaquett",
"Nicolás",
""
]
] | The motion of spinning massless particles in gravitationally curved backgrounds is revisited by considering new types of constraints. Those constraints guarantee zero mass ($P_\mu P^\mu=0$) and they allow for the possibility of trajectories which are not simply null geodesics. To exemplify this previously unknown possibility, the equations of motion are solved for radial motion in Schwarzschild background. It is found that the particle experiences a spin-induced energy shift, which is proportional to the Hawking temperature of the black hole background. |
1806.09516 | Robert \v{S}varc | Robert Svarc, Jiri Podolsky, Vojtech Pravda, Alena Pravdova | Exact black holes in quadratic gravity with any cosmological constant | 6 pages, 3 figures: accepted for publication in Physical Review
Letters | Phys. Rev. Lett. 121, 231104 (2018) | 10.1103/PhysRevLett.121.231104 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new explicit class of black holes in general quadratic gravity
with a cosmological constant. These spherically symmetric
Schwarzschild-Bach-(anti-)de Sitter geometries (Schwa-Bach-(A)dS), derived
under the assumption of constant scalar curvature, form a three-parameter
family determined by the black-hole horizon position, the value of Bach
invariant on the horizon, and the cosmological constant. Using a conformal to
Kundt metric ansatz, the fourth-order field equations simplify to a compact
autonomous system. Its solutions are found as power series, enabling us to
directly set the Bach parameter and/or cosmological constant equal to zero. To
interpret these spacetimes, we analyse the metric functions. In particular, we
demonstrate that for a certain range of positive cosmological constant there
are both black-hole and cosmological horizons, with a static region between
them. The tidal effects on free test particles and basic thermodynamic
quantities are also determined.
| [
{
"created": "Mon, 25 Jun 2018 15:04:17 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 14:33:34 GMT",
"version": "v2"
}
] | 2018-12-10 | [
[
"Svarc",
"Robert",
""
],
[
"Podolsky",
"Jiri",
""
],
[
"Pravda",
"Vojtech",
""
],
[
"Pravdova",
"Alena",
""
]
] | We present a new explicit class of black holes in general quadratic gravity with a cosmological constant. These spherically symmetric Schwarzschild-Bach-(anti-)de Sitter geometries (Schwa-Bach-(A)dS), derived under the assumption of constant scalar curvature, form a three-parameter family determined by the black-hole horizon position, the value of Bach invariant on the horizon, and the cosmological constant. Using a conformal to Kundt metric ansatz, the fourth-order field equations simplify to a compact autonomous system. Its solutions are found as power series, enabling us to directly set the Bach parameter and/or cosmological constant equal to zero. To interpret these spacetimes, we analyse the metric functions. In particular, we demonstrate that for a certain range of positive cosmological constant there are both black-hole and cosmological horizons, with a static region between them. The tidal effects on free test particles and basic thermodynamic quantities are also determined. |
1201.3840 | Bianca Dittrich | Bianca Dittrich | How to construct diffeomorphism symmetry on the lattice | 21 pages, to appear in the Proceedings of the 3rd Quantum Gravity and
Quantum Geometry School 2011, Zakopane, Poland | null | null | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Diffeomorphism symmetry, the fundamental invariance of general relativity, is
generically broken under discretization. After discussing the meaning and
implications of diffeomorphism symmetry in the discrete, in particular for the
continuum limit, we introduce a perturbative framework to construct
discretizations with an exact notion of diffeomorphism symmetry. We will see
that for such a perturbative framework consistency conditions need to be
satisfied which enforce the preservation of the gauge symmetry to the
perturbative order under discussion. These consistency conditions will allow
structural investigations of diffeomorphism invariant discretizations.
| [
{
"created": "Wed, 18 Jan 2012 16:37:03 GMT",
"version": "v1"
}
] | 2012-01-19 | [
[
"Dittrich",
"Bianca",
""
]
] | Diffeomorphism symmetry, the fundamental invariance of general relativity, is generically broken under discretization. After discussing the meaning and implications of diffeomorphism symmetry in the discrete, in particular for the continuum limit, we introduce a perturbative framework to construct discretizations with an exact notion of diffeomorphism symmetry. We will see that for such a perturbative framework consistency conditions need to be satisfied which enforce the preservation of the gauge symmetry to the perturbative order under discussion. These consistency conditions will allow structural investigations of diffeomorphism invariant discretizations. |
1604.05638 | David Kofro\v{n} | David Kofro\v{n} | Separability of test fields equations on the C-metric background II.
Rotating case and the Meissner effect | 6 pages, accepted for publication in Physical Review D | Phys. Rev. D 93, 104012 (2016) | 10.1103/PhysRevD.93.104012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the separation of the Teukolsky master equation for the test field
of arbitrary spin on the background of the rotating C-metric. We also summarize
and simplify some known results about Debye potentials of these fields on type
D background. The equation for the Debye potential is also separated.
Solving for the Debye potential of the electromagnetic field we show that on
the extremely rotating C-metric no magnetic field can penetrate through the
outer black hole horizon --- we thus recover the Meissner effect for the
C-metric.
| [
{
"created": "Tue, 19 Apr 2016 16:25:22 GMT",
"version": "v1"
}
] | 2020-03-25 | [
[
"Kofroň",
"David",
""
]
] | We present the separation of the Teukolsky master equation for the test field of arbitrary spin on the background of the rotating C-metric. We also summarize and simplify some known results about Debye potentials of these fields on type D background. The equation for the Debye potential is also separated. Solving for the Debye potential of the electromagnetic field we show that on the extremely rotating C-metric no magnetic field can penetrate through the outer black hole horizon --- we thus recover the Meissner effect for the C-metric. |
gr-qc/0207018 | Jorge Pullin | Gioel Calabrese, Jorge Pullin, Olivier Sarbach, Manuel Tiglio | Convergence and stability in numerical relativity | 5 pages, RevTex, 4 figures | Phys.Rev. D66 (2002) 041501 | 10.1103/PhysRevD.66.041501 | LSU-REL-070202 | gr-qc | null | It is often the case in numerical relativity that schemes that are known to
be convergent for well posed systems are used in evolutions of weakly
hyperbolic (WH) formulations of Einstein's equations. Here we explicitly show
that with several of the discretizations that have been used through out the
years, this procedure leads to non-convergent schemes. That is, arbitrarily
small initial errors are amplified without bound when resolution is increased,
independently of the amount of numerical dissipation introduced. The lack of
convergence introduced by this instability can be particularly subtle, in the
sense that it can be missed by several convergence tests, especially in 3+1
dimensional codes. We propose tests and methods to analyze convergence that may
help detect these situations.
| [
{
"created": "Tue, 2 Jul 2002 18:08:41 GMT",
"version": "v1"
}
] | 2016-08-16 | [
[
"Calabrese",
"Gioel",
""
],
[
"Pullin",
"Jorge",
""
],
[
"Sarbach",
"Olivier",
""
],
[
"Tiglio",
"Manuel",
""
]
] | It is often the case in numerical relativity that schemes that are known to be convergent for well posed systems are used in evolutions of weakly hyperbolic (WH) formulations of Einstein's equations. Here we explicitly show that with several of the discretizations that have been used through out the years, this procedure leads to non-convergent schemes. That is, arbitrarily small initial errors are amplified without bound when resolution is increased, independently of the amount of numerical dissipation introduced. The lack of convergence introduced by this instability can be particularly subtle, in the sense that it can be missed by several convergence tests, especially in 3+1 dimensional codes. We propose tests and methods to analyze convergence that may help detect these situations. |
gr-qc/0703059 | S. Mignemi | S. Mignemi | Asymptotic properties of black hole solutions in dimensionally reduced
Einstein-Gauss-Bonnet gravity | 9 pages, plain TeX | Gen.Rel.Grav.39:815-824,2007 | 10.1007/s10714-007-0423-5 | null | gr-qc | null | We study the asymptotic behavior of the spherically symmetric solutions of
the system obtained from the dimensional reduction of the six-dimensional
Einstein- Gauss-Bonnet action. We show that in general the scalar field that
parametrizes the size of the internal space is not trivial, but nevertheless
the solutions depend on a single parameter. In analogy with other models
containing Gauss-Bonnet terms, naked singularities are avoided if a minimal
radius for the horizon is assumed.
| [
{
"created": "Thu, 8 Mar 2007 17:00:06 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mignemi",
"S.",
""
]
] | We study the asymptotic behavior of the spherically symmetric solutions of the system obtained from the dimensional reduction of the six-dimensional Einstein- Gauss-Bonnet action. We show that in general the scalar field that parametrizes the size of the internal space is not trivial, but nevertheless the solutions depend on a single parameter. In analogy with other models containing Gauss-Bonnet terms, naked singularities are avoided if a minimal radius for the horizon is assumed. |
gr-qc/9706013 | Alexander L. Gromov | Alexander Gromov (St-Petersburg State Thechnical University, Russia) | Singularities and asymptotic behavior of the Tolman-Bondi model | LaTeX, pages,; submitted to International Journal of Theoretical
Physics | null | null | IRB-StP-GR-050797 | gr-qc | null | The Bondi formula for calculation of the invariant mass in the Tolman- Bondi
(TB) model is interprated as a transformation rule on the set of co-moving
coordinates. The general procedure by which the three arbitrary functions of
the TB model are determined explicitly is presented. The properties of the TB
model, produced by the transformation rule are studied. Two applications are
studied: for the falling TB flat model the equation of motion of two
singularities hypersurfaces are obtained; for the expanding TB flat model the
dependence of size of area with friedmann-like solution on initial conditions
is studied in the limit $t \to +\infty$.
| [
{
"created": "Wed, 4 Jun 1997 13:46:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gromov",
"Alexander",
"",
"St-Petersburg State Thechnical University, Russia"
]
] | The Bondi formula for calculation of the invariant mass in the Tolman- Bondi (TB) model is interprated as a transformation rule on the set of co-moving coordinates. The general procedure by which the three arbitrary functions of the TB model are determined explicitly is presented. The properties of the TB model, produced by the transformation rule are studied. Two applications are studied: for the falling TB flat model the equation of motion of two singularities hypersurfaces are obtained; for the expanding TB flat model the dependence of size of area with friedmann-like solution on initial conditions is studied in the limit $t \to +\infty$. |
2105.09997 | Tony Rothman | Tony Rothman | Addendum to "Hasen\"ohrl and the Equivalence of Mass and Energy" | 4 pages, 1 figure | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This addendum addresses several objections regarding accelerating cavities in
the paper by Boughn and Rothman, "Hasen\"ohrl and the Equivalence of Mass and
Energy," arXiv:1108.2250.
| [
{
"created": "Thu, 20 May 2021 19:16:11 GMT",
"version": "v1"
}
] | 2021-05-24 | [
[
"Rothman",
"Tony",
""
]
] | This addendum addresses several objections regarding accelerating cavities in the paper by Boughn and Rothman, "Hasen\"ohrl and the Equivalence of Mass and Energy," arXiv:1108.2250. |
gr-qc/9602062 | Marco Cavaglia | Marco Cavaglia` and Vittorio de Alfaro | Quantization of a 2D Minisuperspace Model in Dilaton-Einstein Gravity | 10 pages, plain tex, no figures | Int.J.Mod.Phys. D6 (1997) 39-48 | 10.1142/S0218271897000030 | DFTT 10/96 | gr-qc | null | We investigate a minisuperspace model of Einstein gravity plus dilaton that
describes a static spherically symmetric configuration or a Kantowski - Sachs
like universe. We develop the canonical formalism and identify canonical
quantities that generate rigid symmetries of the Hamiltonian. Quantization is
performed by the Dirac and the reduced methods. Both approaches lead to the
same positive definite Hilbert space.
| [
{
"created": "Thu, 29 Feb 1996 15:14:43 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Cavaglia`",
"Marco",
""
],
[
"de Alfaro",
"Vittorio",
""
]
] | We investigate a minisuperspace model of Einstein gravity plus dilaton that describes a static spherically symmetric configuration or a Kantowski - Sachs like universe. We develop the canonical formalism and identify canonical quantities that generate rigid symmetries of the Hamiltonian. Quantization is performed by the Dirac and the reduced methods. Both approaches lead to the same positive definite Hilbert space. |
1907.13209 | Robert Bluhm | Robert Bluhm, Hannah Bossi, and Yuewei Wen | Gravity with explicit spacetime symmetry breaking and the Standard-Model
Extension | Published version | Phys. Rev. D 100, 084022 (2019) | 10.1103/PhysRevD.100.084022 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Standard-Model Extension (SME) is the general phenomenological framework
used to investigate Lorentz violation at the level of effective field theory.
It has been used to obtain stringent experimental bounds on Lorentz violation
in a wide range of tests. In the gravity sector of the SME, it is typically
assumed that the spacetime symmetry breaking occurs spontaneously in order to
avoid potential conflicts with the Bianchi identities. A post-Newtonian limit
as well as matter-gravity couplings in the SME have been developed and
investigated based on this assumption. In this paper, the possibility of using
the SME to also describe gravity theories with explicit spacetime symmetry
breaking is investigated. It is found that in a wide range of cases,
particularly when matter-gravity couplings are included, consistency with the
Bianchi identities can be maintained, and therefore the SME can be used to
search for signals of the symmetry breaking. Two examples with explicit
breaking are considered. The first is ghost-free massive gravity with an
effective metric that couples to matter. The second is Horava gravity coupled
with matter in an infrared limit.
| [
{
"created": "Tue, 30 Jul 2019 20:12:27 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Oct 2019 14:01:21 GMT",
"version": "v2"
}
] | 2019-10-16 | [
[
"Bluhm",
"Robert",
""
],
[
"Bossi",
"Hannah",
""
],
[
"Wen",
"Yuewei",
""
]
] | The Standard-Model Extension (SME) is the general phenomenological framework used to investigate Lorentz violation at the level of effective field theory. It has been used to obtain stringent experimental bounds on Lorentz violation in a wide range of tests. In the gravity sector of the SME, it is typically assumed that the spacetime symmetry breaking occurs spontaneously in order to avoid potential conflicts with the Bianchi identities. A post-Newtonian limit as well as matter-gravity couplings in the SME have been developed and investigated based on this assumption. In this paper, the possibility of using the SME to also describe gravity theories with explicit spacetime symmetry breaking is investigated. It is found that in a wide range of cases, particularly when matter-gravity couplings are included, consistency with the Bianchi identities can be maintained, and therefore the SME can be used to search for signals of the symmetry breaking. Two examples with explicit breaking are considered. The first is ghost-free massive gravity with an effective metric that couples to matter. The second is Horava gravity coupled with matter in an infrared limit. |
0906.3818 | Marcello Ortaggio | Marcello Ortaggio | Bel-Debever criteria for the classification of the Weyl tensors in
higher dimensions | 8 pages | Class.Quant.Grav.26:195015,2009 | 10.1088/0264-9381/26/19/195015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An extension to higher dimensions of the Bel-Debever characterization of the
Weyl tensor is considered. This provides algebraic conditions that uniquely
determine the multiplicity of a Weyl aligned null direction (WAND), and thus
the principal Weyl type, in a frame independent way. The specification of
several "subtypes" is also encompassed by the criteria. We further comment on a
Cartan-like geometrical interpretation of WANDs in terms of their invariance
properties under parallel transport around infinitesimal loops. As a result,
restrictions on the algebraic types permitted in spacetimes that admit a
recurrent/covariantly constant vector field are outlined.
| [
{
"created": "Sat, 20 Jun 2009 17:02:57 GMT",
"version": "v1"
}
] | 2009-10-02 | [
[
"Ortaggio",
"Marcello",
""
]
] | An extension to higher dimensions of the Bel-Debever characterization of the Weyl tensor is considered. This provides algebraic conditions that uniquely determine the multiplicity of a Weyl aligned null direction (WAND), and thus the principal Weyl type, in a frame independent way. The specification of several "subtypes" is also encompassed by the criteria. We further comment on a Cartan-like geometrical interpretation of WANDs in terms of their invariance properties under parallel transport around infinitesimal loops. As a result, restrictions on the algebraic types permitted in spacetimes that admit a recurrent/covariantly constant vector field are outlined. |
1406.2253 | Jan Harms | Jan Harms, Stefan Hild | Passive Newtonian noise suppression for gravitational-wave observatories
based on shaping of the local topography | 12 pages, 5 figures | null | 10.1088/0264-9381/31/18/185011 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we propose a new method for reducing Newtonian noise in
laser-interferometric gravitational-wave detectors located on the Earth's
surface. We show that by excavating meter-scale recesses in the ground around
the main test masses of a gravitational wave detector it is possible to reduce
the coupling of Rayleigh wave driven seismic disturbances to test mass
displacement. A discussion of the optimal recess shape is given and we use
finite element simulations to derive the scaling of the Newtonian noise
suppression with the parameters of the recess as well as the frequency of the
seismic excitation. Considering an interferometer similar to an Advance LIGO
configuration, our simulations indicate a frequency dependent Newtonian noise
suppression factor of 2 to 4 in the relevant frequency range for a recesses of
4m depth and a width and length of 11m and 5m, respectively. Though a retrofit
to existing interferometers seems not impossible, the application of our
concept to future infrastructures seems to provide a better benefit/cost ratio
and therefore a higher feasibility.
| [
{
"created": "Mon, 9 Jun 2014 17:37:31 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Harms",
"Jan",
""
],
[
"Hild",
"Stefan",
""
]
] | In this article we propose a new method for reducing Newtonian noise in laser-interferometric gravitational-wave detectors located on the Earth's surface. We show that by excavating meter-scale recesses in the ground around the main test masses of a gravitational wave detector it is possible to reduce the coupling of Rayleigh wave driven seismic disturbances to test mass displacement. A discussion of the optimal recess shape is given and we use finite element simulations to derive the scaling of the Newtonian noise suppression with the parameters of the recess as well as the frequency of the seismic excitation. Considering an interferometer similar to an Advance LIGO configuration, our simulations indicate a frequency dependent Newtonian noise suppression factor of 2 to 4 in the relevant frequency range for a recesses of 4m depth and a width and length of 11m and 5m, respectively. Though a retrofit to existing interferometers seems not impossible, the application of our concept to future infrastructures seems to provide a better benefit/cost ratio and therefore a higher feasibility. |
1607.01420 | Noah Sennett | Noah Sennett, Sylvain Marsat and Alessandra Buonanno | Gravitational waveforms in scalar-tensor gravity at 2PN relative order | 23 pages | Phys. Rev. D 94, 084003 (2016) | 10.1103/PhysRevD.94.084003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the gravitational waveform from a binary system in scalar-tensor
gravity at 2PN relative order. We restrict our calculation to non-spinning
binary systems on quasi-circular orbits and compute the spin-weighted spherical
modes of the radiation. The evolution of the phase of the waveform is computed
in the time and frequency domains. The emission of dipolar radiation is the
lowest-order dissipative process in scalar-tensor gravity. However, stringent
constraints set by current astrophysical observations indicate that this effect
is subdominant to quadrupolar radiation for most prospective gravitational-wave
sources. We compute the waveform for systems whose inspiral is driven by: (a)
dipolar radiation (e.g., binary pulsars or spontaneously scalarized systems)
and (b) quadrupolar radiation (e.g., typical sources for space-based and
ground-based detectors).
| [
{
"created": "Tue, 5 Jul 2016 21:20:09 GMT",
"version": "v1"
}
] | 2017-10-11 | [
[
"Sennett",
"Noah",
""
],
[
"Marsat",
"Sylvain",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | We compute the gravitational waveform from a binary system in scalar-tensor gravity at 2PN relative order. We restrict our calculation to non-spinning binary systems on quasi-circular orbits and compute the spin-weighted spherical modes of the radiation. The evolution of the phase of the waveform is computed in the time and frequency domains. The emission of dipolar radiation is the lowest-order dissipative process in scalar-tensor gravity. However, stringent constraints set by current astrophysical observations indicate that this effect is subdominant to quadrupolar radiation for most prospective gravitational-wave sources. We compute the waveform for systems whose inspiral is driven by: (a) dipolar radiation (e.g., binary pulsars or spontaneously scalarized systems) and (b) quadrupolar radiation (e.g., typical sources for space-based and ground-based detectors). |
0807.1043 | Donald Neville | Donald E. Neville | On the Classical Limit of Spin Network Gravity: Two Conjectures | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Estimates are given of the time scales which govern spreading of a coherent
state wave packet. The estimates, based on dimensional analysis, suggest that
spreading should be small for coherent states with average angular momentum of
order 100 or larger. It is conjectured that in the classical limit, terms in
the Hamiltonian which add a new vertex will be suppressed, compared to terms
which modify the existing spin network without changing the number of vertices.
| [
{
"created": "Mon, 7 Jul 2008 15:32:50 GMT",
"version": "v1"
}
] | 2008-07-08 | [
[
"Neville",
"Donald E.",
""
]
] | Estimates are given of the time scales which govern spreading of a coherent state wave packet. The estimates, based on dimensional analysis, suggest that spreading should be small for coherent states with average angular momentum of order 100 or larger. It is conjectured that in the classical limit, terms in the Hamiltonian which add a new vertex will be suppressed, compared to terms which modify the existing spin network without changing the number of vertices. |
2201.10748 | Yunqi Liu | Hong Guo, Yunqi Liu, Chao Zhang, Yungui Gong, Wei-Liang Qian, Rui-Hong
Yue | Detection of scalar fields by Extreme Mass Ratio Inspirals with a Kerr
black hole | 22 pages, 7 figures | PhysRevD.106.024047 (2022) | 10.1103/PhysRevD.106.024047 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study extreme mass ratio inspirals occurring in modified gravity, for
which the system is modeled by a small compact object with scalar charge
spiraling into a supermassive Kerr black hole. Besides the tensorial
gravitational waves arising from the metric perturbations, radiations are also
induced by the scalar field. The relevant metric and scalar perturbations are
triggered by the orbital motion of the small object, which give rise to a
system of inhomogeneous differential equations under the adiabatic
approximation. Such a system of equations is then solved numerically using
Green's function furnished by the solutions of the corresponding homogeneous
equations. To explore the present scenario from an observational perspective,
we investigate how the pertinent observables are dependent on specific
spacetime configurations. In this regard, the energy fluxes and the
gravitational wave dephasing accumulated during the process are evaluated, as
functions of the scalar charge, mass ratio, and spin of the central
supermassive black hole. In particular, the presence of additional scalar
emission leads to a more significant rate of overall energy loss, which, in
turn, decreases the total number of orbital cycles before the small object
plunges into the central black hole. Moreover, for a central black hole with a
higher spin, the imprints of the scalar charge on the resultant gravitational
radiations are found to be more significant, which indicates the possibility of
detecting the scalar charge.
| [
{
"created": "Wed, 26 Jan 2022 04:50:23 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jul 2022 03:24:38 GMT",
"version": "v2"
}
] | 2022-07-28 | [
[
"Guo",
"Hong",
""
],
[
"Liu",
"Yunqi",
""
],
[
"Zhang",
"Chao",
""
],
[
"Gong",
"Yungui",
""
],
[
"Qian",
"Wei-Liang",
""
],
[
"Yue",
"Rui-Hong",
""
]
] | We study extreme mass ratio inspirals occurring in modified gravity, for which the system is modeled by a small compact object with scalar charge spiraling into a supermassive Kerr black hole. Besides the tensorial gravitational waves arising from the metric perturbations, radiations are also induced by the scalar field. The relevant metric and scalar perturbations are triggered by the orbital motion of the small object, which give rise to a system of inhomogeneous differential equations under the adiabatic approximation. Such a system of equations is then solved numerically using Green's function furnished by the solutions of the corresponding homogeneous equations. To explore the present scenario from an observational perspective, we investigate how the pertinent observables are dependent on specific spacetime configurations. In this regard, the energy fluxes and the gravitational wave dephasing accumulated during the process are evaluated, as functions of the scalar charge, mass ratio, and spin of the central supermassive black hole. In particular, the presence of additional scalar emission leads to a more significant rate of overall energy loss, which, in turn, decreases the total number of orbital cycles before the small object plunges into the central black hole. Moreover, for a central black hole with a higher spin, the imprints of the scalar charge on the resultant gravitational radiations are found to be more significant, which indicates the possibility of detecting the scalar charge. |
gr-qc/9808068 | Alena Pravdova | J. Bicak, A. Pravdova | Symmetries of asymptotically flat electrovacuum spacetimes and radiation | 23 pages, RevTeX, to appear in JMP | J.Math.Phys. 39 (1998) 6011-6039 | 10.1063/1.532611 | null | gr-qc | null | Symmetries compatible with asymptotic flatness and admitting gravitational
and electromagnetic radiation are studied by using the Bondi-Sachs-van der Burg
formalism. It is shown that in axially symmetric electrovacuum spacetimes in
which at least locally a smooth null infinity in the sense of Penrose exists,
the only second allowable symmetry is either the translational symmetry or the
boost symmetry. Translationally invariant spacetimes with in general a straight
"cosmic string" along the axis of symmetry are non-radiative although they can
have a non-vanishing news function. The boost-rotation symmetric spacetimes are
radiative. They describe "uniformly accelerated charged particles" or black
holes which in general may also be rotating - the axial and an additional
Killing vector are not assumed to be hypersurface orthogonal. The general
functional forms of both gravitational and electromagnetic news functions, and
of the mass aspect and total mass of asymptotically flat boost-rotation
symmetric spacetimes at null infinity are obtained. The expressions for the
mass are new even in the case of vacuum boost-rotation symmetric spacetimes
with hypersurface orthogonal Killing vectors. In Appendices some errors
appearing in previous works are corrected.
| [
{
"created": "Tue, 25 Aug 1998 14:50:59 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bicak",
"J.",
""
],
[
"Pravdova",
"A.",
""
]
] | Symmetries compatible with asymptotic flatness and admitting gravitational and electromagnetic radiation are studied by using the Bondi-Sachs-van der Burg formalism. It is shown that in axially symmetric electrovacuum spacetimes in which at least locally a smooth null infinity in the sense of Penrose exists, the only second allowable symmetry is either the translational symmetry or the boost symmetry. Translationally invariant spacetimes with in general a straight "cosmic string" along the axis of symmetry are non-radiative although they can have a non-vanishing news function. The boost-rotation symmetric spacetimes are radiative. They describe "uniformly accelerated charged particles" or black holes which in general may also be rotating - the axial and an additional Killing vector are not assumed to be hypersurface orthogonal. The general functional forms of both gravitational and electromagnetic news functions, and of the mass aspect and total mass of asymptotically flat boost-rotation symmetric spacetimes at null infinity are obtained. The expressions for the mass are new even in the case of vacuum boost-rotation symmetric spacetimes with hypersurface orthogonal Killing vectors. In Appendices some errors appearing in previous works are corrected. |
1409.8144 | Lisa Glaser | Lisa Glaser | Endeavours in Discrete Lorentzian Geometry; A thesis in five papers | Ph.D. thesis, slight modification for online version, 105 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To solve the path integral for quantum gravity, one needs to regularise the
space-times that are summed over. This regularisation usually is a
discretisation, which makes it necessary to give up some paradigms or
symmetries of continuum physics.
Causal dynamical triangulations regularises the path integral through a
simplicial discretisation that introduces a preferred time foliation.
The first part of this thesis presents three articles on causal dynamical
triangulations. The first article shows how to obtain a multicritical 2d model
by coupling the theory to hard dimers. The second explores the connection to
Ho\v{r}ava-Lifshitz gravity that is suggested by the time foliation and
establishes that in 2d the theories are equivalent. The last article does not
directly concern causal dynamical triangulations but Euclidian dynamical
triangulations with an additional measure term, which are examined to
understand whether they contain an extended phase without the need for a
preferred time foliation.
Causal set theory uses an explicitly Lorentz invariant discretisation, which
introduces non-local effects.
The second part of this thesis presents two articles in causal set theory.
The first explicitly calculates closed form expressions for the d'Alembertian
operator in any dimension, which can be implemented in computer simulations.
The second develops a ruler to examine the manifoldlikeness of small regions in
a causal set, and can be used to recover locality.
| [
{
"created": "Mon, 29 Sep 2014 14:55:27 GMT",
"version": "v1"
}
] | 2014-09-30 | [
[
"Glaser",
"Lisa",
""
]
] | To solve the path integral for quantum gravity, one needs to regularise the space-times that are summed over. This regularisation usually is a discretisation, which makes it necessary to give up some paradigms or symmetries of continuum physics. Causal dynamical triangulations regularises the path integral through a simplicial discretisation that introduces a preferred time foliation. The first part of this thesis presents three articles on causal dynamical triangulations. The first article shows how to obtain a multicritical 2d model by coupling the theory to hard dimers. The second explores the connection to Ho\v{r}ava-Lifshitz gravity that is suggested by the time foliation and establishes that in 2d the theories are equivalent. The last article does not directly concern causal dynamical triangulations but Euclidian dynamical triangulations with an additional measure term, which are examined to understand whether they contain an extended phase without the need for a preferred time foliation. Causal set theory uses an explicitly Lorentz invariant discretisation, which introduces non-local effects. The second part of this thesis presents two articles in causal set theory. The first explicitly calculates closed form expressions for the d'Alembertian operator in any dimension, which can be implemented in computer simulations. The second develops a ruler to examine the manifoldlikeness of small regions in a causal set, and can be used to recover locality. |
1509.03884 | Cosimo Bambi | Cosimo Bambi | Testing black hole candidates with electromagnetic radiation | 47 pages, 26 figures. Invited review paper for Reviews of Modern
Physics. v3: refereed version. v4: minor typos corrected | Rev. Mod. Phys. 89, 025001 (2017) | 10.1103/RevModPhys.89.025001 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astrophysical black hole candidates are thought to be the Kerr black holes of
general relativity, but there is not yet direct observational evidence that the
spacetime geometry around these objects is described by the Kerr solution. The
study of the properties of the electromagnetic radiation emitted by gas or
stars orbiting these objects can potentially test the Kerr black hole
hypothesis. In this paper, I review the state of the art of this research
field, describing the possible approaches to test the Kerr metric with current
and future observational facilities and discussing current constraints.
| [
{
"created": "Sun, 13 Sep 2015 19:05:18 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Sep 2015 19:18:54 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Nov 2016 18:20:50 GMT",
"version": "v3"
},
{
"created": "Thu, 6 Apr 2017 21:41:09 GMT",
"version": "v4"
}
] | 2017-04-10 | [
[
"Bambi",
"Cosimo",
""
]
] | Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity, but there is not yet direct observational evidence that the spacetime geometry around these objects is described by the Kerr solution. The study of the properties of the electromagnetic radiation emitted by gas or stars orbiting these objects can potentially test the Kerr black hole hypothesis. In this paper, I review the state of the art of this research field, describing the possible approaches to test the Kerr metric with current and future observational facilities and discussing current constraints. |
1206.0506 | Chiang-Mei Chen | Ming-Fan Wu, Chiang-Mei Chen, Jian-Liang Liu, James M. Nester | Quasi-local Energy for Spherically Symmetric Spacetimes | 16 pages, no figures | null | 10.1007/s10714-012-1399-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present two complementary approaches for determining the reference for the
covariant Hamiltonian boundary term quasi-local energy and test them on
spherically symmetric spacetimes. On the one hand, we isometrically match the
2-surface and extremize the energy. This can be done in two ways, which we call
programs I (without constraint) and II (with additional constraints). On the
other hand, we match the orthonormal 4-frames of the dynamic and the reference
spacetimes. Then, if we further specify the observer by requiring the reference
displacement to be the timelike Killing vector of the reference, the result is
the same as program I, and the energy can be positive, zero, or even negative.
If, instead, we require that the Lie derivatives of the two-area along the
displacement vector in both the dynamic and reference spacetimes to be the
same, the result is the same as program II, and it satisfies the usual
criteria: the energies are non-negative and vanish only for Minkowski (or
anti-de Sitter) spacetime.
| [
{
"created": "Mon, 4 Jun 2012 01:21:28 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Wu",
"Ming-Fan",
""
],
[
"Chen",
"Chiang-Mei",
""
],
[
"Liu",
"Jian-Liang",
""
],
[
"Nester",
"James M.",
""
]
] | We present two complementary approaches for determining the reference for the covariant Hamiltonian boundary term quasi-local energy and test them on spherically symmetric spacetimes. On the one hand, we isometrically match the 2-surface and extremize the energy. This can be done in two ways, which we call programs I (without constraint) and II (with additional constraints). On the other hand, we match the orthonormal 4-frames of the dynamic and the reference spacetimes. Then, if we further specify the observer by requiring the reference displacement to be the timelike Killing vector of the reference, the result is the same as program I, and the energy can be positive, zero, or even negative. If, instead, we require that the Lie derivatives of the two-area along the displacement vector in both the dynamic and reference spacetimes to be the same, the result is the same as program II, and it satisfies the usual criteria: the energies are non-negative and vanish only for Minkowski (or anti-de Sitter) spacetime. |
2105.05954 | Marco Schreck MS | Carlos M. Reyes and Marco Schreck | Hamiltonian formulation of an effective modified gravity with
nondynamical background fields | 79 pages, 1 figure, prepared for submission to JHEP | null | 10.1103/PhysRevD.104.124042 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current paper is dedicated to developing a (3+1) decomposition for the
minimal gravitational Standard-Model Extension. Our setting is explicit
diffeomorphism violation and we focus on the background fields known in the
literature as $u$ and $s^{\mu\nu}$. The Hamiltonian formalism is developed for
these contributions, which amounts to deriving modified Hamiltonian and
momentum constraints. We then study the connection between these modified
constraints and the modified Einstein equations. Implications are drawn on the
form of the background fields to guarantee the internal consistency of the
corresponding modified-gravity theories. In the course of our analysis, we
obtain a set of consistency requirements for $u$ and certain sectors of
$s^{\mu\nu}$. We argue that the constraint structure remains untouched when
these conditions are satisfied. Our results shed light on explicit violations
of diffeomorphism invariance and local Lorentz invariance in gravity. They may
turn out to be valuable for developing a better understanding of effective
modified-gravity theories.
| [
{
"created": "Wed, 12 May 2021 20:30:37 GMT",
"version": "v1"
}
] | 2022-01-05 | [
[
"Reyes",
"Carlos M.",
""
],
[
"Schreck",
"Marco",
""
]
] | The current paper is dedicated to developing a (3+1) decomposition for the minimal gravitational Standard-Model Extension. Our setting is explicit diffeomorphism violation and we focus on the background fields known in the literature as $u$ and $s^{\mu\nu}$. The Hamiltonian formalism is developed for these contributions, which amounts to deriving modified Hamiltonian and momentum constraints. We then study the connection between these modified constraints and the modified Einstein equations. Implications are drawn on the form of the background fields to guarantee the internal consistency of the corresponding modified-gravity theories. In the course of our analysis, we obtain a set of consistency requirements for $u$ and certain sectors of $s^{\mu\nu}$. We argue that the constraint structure remains untouched when these conditions are satisfied. Our results shed light on explicit violations of diffeomorphism invariance and local Lorentz invariance in gravity. They may turn out to be valuable for developing a better understanding of effective modified-gravity theories. |
1203.3963 | Daniela Doneva | Daniela D. Doneva, Stoytcho S. Yazadjiev | Non-radial oscillations of anisotropic neutron stars in the Cowling
approximation | 17 pages, 8 figures; title changed, comments added | Phys. Rev. D 85, 124023 (2012) | 10.1103/PhysRevD.85.124023 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most common assumptions in the study of neutron star models and
their oscillations is that the pressure is isotopic, however there are
arguments that this may not be correct. Thus in the present paper we make a
first step towards studying the nonradial oscillations of neutron stars with an
anisotropic pressure. We adopt the so-called Cowling approximation where the
spacetime metric is kept fixed and the oscillation spectrum for the first few
fluid modes is obtained. The effect of the anisotropy on the frequencies is
apparent, although with the present results it might be hard to distinguish it
from the changes in the frequencies caused by different equations of state.
| [
{
"created": "Sun, 18 Mar 2012 15:39:44 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jun 2012 12:22:03 GMT",
"version": "v2"
}
] | 2012-06-25 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | One of the most common assumptions in the study of neutron star models and their oscillations is that the pressure is isotopic, however there are arguments that this may not be correct. Thus in the present paper we make a first step towards studying the nonradial oscillations of neutron stars with an anisotropic pressure. We adopt the so-called Cowling approximation where the spacetime metric is kept fixed and the oscillation spectrum for the first few fluid modes is obtained. The effect of the anisotropy on the frequencies is apparent, although with the present results it might be hard to distinguish it from the changes in the frequencies caused by different equations of state. |
0711.4554 | Diana Lopez Nacir | Diana L\'opez Nacir and Francisco D. Mazzitelli | New counterterms induced by trans-Planckian physics in semiclassical
gravity | null | Phys.Rev.D78:044001,2008 | 10.1103/PhysRevD.78.044001 | null | gr-qc hep-th | null | We consider free and self-interacting quantum scalar fields satisfying
modified dispersion relations in the framework of Einstein-Aether theory. Using
adiabatic regularization, we study the renormalization of the equation for the
mean value of the field in the self-interacting case, and the renormalization
of the semiclassical Einstein-Aether equations for free fields. In both cases
we consider Bianchi type I background spacetimes. Contrary to what happens for
{\it free} fields in {\it flat} Robertson-Walker spacetimes, the
self-interaction and/or the anisotropy produce non-purely geometric terms in
the adiabatic expansion, i.e terms that involve both the metric $g_{\mu\nu}$
and the aether field $u_{\mu}$. We argue that, in a general spacetime, the
renormalization of the theory would involve new counterterms constructed with
$g_{\mu\nu}$ and $u_{\mu}$, generating a fine-tuning problem for the
Einstein-Aether theory.
| [
{
"created": "Wed, 28 Nov 2007 18:16:56 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nacir",
"Diana López",
""
],
[
"Mazzitelli",
"Francisco D.",
""
]
] | We consider free and self-interacting quantum scalar fields satisfying modified dispersion relations in the framework of Einstein-Aether theory. Using adiabatic regularization, we study the renormalization of the equation for the mean value of the field in the self-interacting case, and the renormalization of the semiclassical Einstein-Aether equations for free fields. In both cases we consider Bianchi type I background spacetimes. Contrary to what happens for {\it free} fields in {\it flat} Robertson-Walker spacetimes, the self-interaction and/or the anisotropy produce non-purely geometric terms in the adiabatic expansion, i.e terms that involve both the metric $g_{\mu\nu}$ and the aether field $u_{\mu}$. We argue that, in a general spacetime, the renormalization of the theory would involve new counterterms constructed with $g_{\mu\nu}$ and $u_{\mu}$, generating a fine-tuning problem for the Einstein-Aether theory. |
1612.07390 | H\'el\`ene Pihan-Le Bars | H. Pihan-Le Bars, C. Guerlin, R.-D. Lasseri, J.-P. Ebran, Q. G.
Bailey, S. Bize, E. Khan, P. Wolf | Lorentz-symmetry test at Planck-scale suppression with nucleons in a
spin-polarized $^{133}$Cs cold atom clock | null | Phys. Rev. D 95, 075026 (2017) | 10.1103/PhysRevD.95.075026 | null | gr-qc hep-ex nucl-th physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce an improved model that links the frequency shift of the
$^{133}\text{Cs}$ hyperfine Zeeman transitions $\vert F = 3, m_F>
\longleftrightarrow \vert F = 4, m_F >$ to the Lorentz-violating Standard-Model
Extension (SME) coefficients of the proton and neutron. The new model uses
Lorentz transformations developed to second order in boost and additionally
takes the nuclear structure into account, beyond the simple Schmidt model used
previously in SME analyses, thereby providing access to both proton and neutron
SME coefficients including the isotropic coefficient $\tilde{c}_{TT}$. Using
this new model in a second analysis of the data delivered by the FO2 dual Cs/Rb
fountain at Paris Observatory and previously analysed in
arXiv:hep-ph/0601024v1, we improve by up to 12 orders of magnitude the present
maximum sensitivities (see arXiv:0801.0287v9) on the $\tilde{c}_{Q}$,
$\tilde{c}_{TJ}$ and $\tilde{c}_{TT}$ coefficients for the neutron and on the
$\tilde{c}_{TT}$ coefficient for the proton, reaching respectively $10^{-20}$,
$10^{-17}$, $10^{-13}$ and $10^{-15}$ GeV.
| [
{
"created": "Wed, 21 Dec 2016 23:32:35 GMT",
"version": "v1"
},
{
"created": "Wed, 31 May 2017 09:46:47 GMT",
"version": "v2"
}
] | 2017-06-01 | [
[
"Bars",
"H. Pihan-Le",
""
],
[
"Guerlin",
"C.",
""
],
[
"Lasseri",
"R. -D.",
""
],
[
"Ebran",
"J. -P.",
""
],
[
"Bailey",
"Q. G.",
""
],
[
"Bize",
"S.",
""
],
[
"Khan",
"E.",
""
],
[
"Wolf",
"P.... | We introduce an improved model that links the frequency shift of the $^{133}\text{Cs}$ hyperfine Zeeman transitions $\vert F = 3, m_F> \longleftrightarrow \vert F = 4, m_F >$ to the Lorentz-violating Standard-Model Extension (SME) coefficients of the proton and neutron. The new model uses Lorentz transformations developed to second order in boost and additionally takes the nuclear structure into account, beyond the simple Schmidt model used previously in SME analyses, thereby providing access to both proton and neutron SME coefficients including the isotropic coefficient $\tilde{c}_{TT}$. Using this new model in a second analysis of the data delivered by the FO2 dual Cs/Rb fountain at Paris Observatory and previously analysed in arXiv:hep-ph/0601024v1, we improve by up to 12 orders of magnitude the present maximum sensitivities (see arXiv:0801.0287v9) on the $\tilde{c}_{Q}$, $\tilde{c}_{TJ}$ and $\tilde{c}_{TT}$ coefficients for the neutron and on the $\tilde{c}_{TT}$ coefficient for the proton, reaching respectively $10^{-20}$, $10^{-17}$, $10^{-13}$ and $10^{-15}$ GeV. |
1607.06185 | Yong-Wan Kim | Yong-Wan Kim, Seung Kook Kim, Young-Jai Park | Thermodynamic stability of modified Schwarzschild-AdS black hole in
rainbow gravity | 24 pages, 9 figures, references added, version to appear in EPJC | null | 10.1140/epjc/s10052-016-4393-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have extended the previous study of the thermodynamics and
phase transition of the Schwarzschild black hole in the rainbow gravity to the
Schwarzschild-AdS black hole where metric depends on the energy of a probe.
Making use of the Heisenberg uncertainty principle and the modified dispersion
relation, we have obtained the modified local Hawking temperature and
thermodynamic quantities in an isothermal cavity. Moreover, we carry out the
analysis of constant temperature slices of a black hole. As a result, we have
shown that there also exists another Hawking-Page-like phase transition in
which case a locally stable small black hole tunnels into a globally stable
large black hole as well as the standard Hawking-Page phase transition from a
hot flat space to a black hole.
| [
{
"created": "Thu, 21 Jul 2016 04:26:58 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jul 2016 06:46:42 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Sep 2016 02:03:42 GMT",
"version": "v3"
}
] | 2016-11-23 | [
[
"Kim",
"Yong-Wan",
""
],
[
"Kim",
"Seung Kook",
""
],
[
"Park",
"Young-Jai",
""
]
] | In this paper, we have extended the previous study of the thermodynamics and phase transition of the Schwarzschild black hole in the rainbow gravity to the Schwarzschild-AdS black hole where metric depends on the energy of a probe. Making use of the Heisenberg uncertainty principle and the modified dispersion relation, we have obtained the modified local Hawking temperature and thermodynamic quantities in an isothermal cavity. Moreover, we carry out the analysis of constant temperature slices of a black hole. As a result, we have shown that there also exists another Hawking-Page-like phase transition in which case a locally stable small black hole tunnels into a globally stable large black hole as well as the standard Hawking-Page phase transition from a hot flat space to a black hole. |
1304.2679 | Norbert Bodendorfer | Norbert Bodendorfer, Thomas Thiemann, Andreas Thurn | New Variables for Classical and Quantum Gravity in all Dimensions V.
Isolated Horizon Boundary Degrees of Freedom | 49 pages. v2. journal version. Reference added | Class. Quantum Grav. 31 (2014) 055002 | 10.1088/0264-9381/31/5/055002 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we generalise the treatment of isolated horizons in loop
quantum gravity, resulting in a Chern-Simons theory on the boundary in the
four-dimensional case, to non-distorted isolated horizons in 2(n+1)-dimensional
spacetimes. The key idea is to generalise the four-dimensional isolated horizon
boundary condition by using the Euler topological density of a spatial slice of
the black hole horizon as a measure of distortion. The resulting symplectic
structure on the horizon coincides with the one of higher-dimensional
SO(2(n+1))-Chern-Simons theory in terms of a Peldan-type hybrid connection and
resembles closely the usual treatment in 3+1 dimensions. We comment briefly on
a possible quantisation of the horizon theory. Here, some subtleties arise
since higher-dimensional non-Abelian Chern-Simons theory has local degrees of
freedom. However, when replacing the natural generalisation to higher
dimensions of the usual boundary condition by an equally natural stronger one,
it is conceivable that the problems originating from the local degrees of
freedom are avoided, thus possibly resulting in a finite entropy.
| [
{
"created": "Tue, 9 Apr 2013 18:00:34 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Nov 2014 11:42:41 GMT",
"version": "v2"
}
] | 2014-11-25 | [
[
"Bodendorfer",
"Norbert",
""
],
[
"Thiemann",
"Thomas",
""
],
[
"Thurn",
"Andreas",
""
]
] | In this paper, we generalise the treatment of isolated horizons in loop quantum gravity, resulting in a Chern-Simons theory on the boundary in the four-dimensional case, to non-distorted isolated horizons in 2(n+1)-dimensional spacetimes. The key idea is to generalise the four-dimensional isolated horizon boundary condition by using the Euler topological density of a spatial slice of the black hole horizon as a measure of distortion. The resulting symplectic structure on the horizon coincides with the one of higher-dimensional SO(2(n+1))-Chern-Simons theory in terms of a Peldan-type hybrid connection and resembles closely the usual treatment in 3+1 dimensions. We comment briefly on a possible quantisation of the horizon theory. Here, some subtleties arise since higher-dimensional non-Abelian Chern-Simons theory has local degrees of freedom. However, when replacing the natural generalisation to higher dimensions of the usual boundary condition by an equally natural stronger one, it is conceivable that the problems originating from the local degrees of freedom are avoided, thus possibly resulting in a finite entropy. |
1801.00272 | Klaus Kassner | Klaus Kassner | Radially falling test particle approaching an evaporating black hole | 12 pages, 3 figures, revised version, likely to be accepted by
Canadian Journal of Physics | null | 10.1139/cjp-2017-1001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A simple model for an evaporating non-rotating black hole is considered,
employing a global time that does not become singular at the putative horizon.
The dynamics of a test particle falling radially towards the center of the
black hole is then investigated. Contrary to a previous approach, we find that
the particle may pass the Schwarzschild radius before the black hole has gone.
Backreaction effects of Hawking radiation on the space-time metric are not
considered, rather a purely kinematical point of view is taken here. The
importance of choosing an appropriate time coordinate when describing physical
processes in the vicinity of the Schwarzschild radius is emphasized. For a
shrinking black hole, the true event horizon is found to be inside the sphere
delimited by that radius.
| [
{
"created": "Sun, 31 Dec 2017 12:03:25 GMT",
"version": "v1"
},
{
"created": "Fri, 11 May 2018 15:31:52 GMT",
"version": "v2"
}
] | 2019-02-26 | [
[
"Kassner",
"Klaus",
""
]
] | A simple model for an evaporating non-rotating black hole is considered, employing a global time that does not become singular at the putative horizon. The dynamics of a test particle falling radially towards the center of the black hole is then investigated. Contrary to a previous approach, we find that the particle may pass the Schwarzschild radius before the black hole has gone. Backreaction effects of Hawking radiation on the space-time metric are not considered, rather a purely kinematical point of view is taken here. The importance of choosing an appropriate time coordinate when describing physical processes in the vicinity of the Schwarzschild radius is emphasized. For a shrinking black hole, the true event horizon is found to be inside the sphere delimited by that radius. |
gr-qc/0404060 | Kostadin Trencevski | Kostadin Trencevski, Emilija G. Celakoska and Vladimir Balan | Research of Gravitation in Flat Minkowski Space | 28 pages | International Journal of Theoretical Physics, 50(1) (2011), 1-26 | 10.1007/s10773-010-0488-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper it is introduced and studied an alternative theory of
gravitation in flat Minkowski space. Using an antisymmetric tensor, which is
analogous to the tensor of electromagnetic field, a non-linear connection is
introduced. It is very convenient for studying the perihelion/periastron shift,
deflection of the light rays near the Sun and the frame dragging together with
geodetic precession, i.e. effects where angles are involved. Although the
corresponding results are obtained in rather different way, they are the same
as in the General Relativity. The results about the barycenter of two bodies
are also the same as in the General Relativity. Comparing the derived equations
of motion for the $n$-body problem with the Einstein-Infeld-Hoffmann equations,
it is found that they differ from the EIH equations by Lorentz invariant terms
of order $c^{-2}$.
| [
{
"created": "Tue, 13 Apr 2004 16:31:12 GMT",
"version": "v1"
},
{
"created": "Sat, 15 May 2004 18:02:10 GMT",
"version": "v2"
},
{
"created": "Sat, 14 Dec 2013 09:32:26 GMT",
"version": "v3"
}
] | 2013-12-17 | [
[
"Trencevski",
"Kostadin",
""
],
[
"Celakoska",
"Emilija G.",
""
],
[
"Balan",
"Vladimir",
""
]
] | In this paper it is introduced and studied an alternative theory of gravitation in flat Minkowski space. Using an antisymmetric tensor, which is analogous to the tensor of electromagnetic field, a non-linear connection is introduced. It is very convenient for studying the perihelion/periastron shift, deflection of the light rays near the Sun and the frame dragging together with geodetic precession, i.e. effects where angles are involved. Although the corresponding results are obtained in rather different way, they are the same as in the General Relativity. The results about the barycenter of two bodies are also the same as in the General Relativity. Comparing the derived equations of motion for the $n$-body problem with the Einstein-Infeld-Hoffmann equations, it is found that they differ from the EIH equations by Lorentz invariant terms of order $c^{-2}$. |
1910.06785 | Jerzy Kocik | Jerzy Kocik | Making sense of relativistic composition of velocities | 17 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | What does it mean to ``add'' velocities relativistically -- clarification of
the conceptual problems, new derivations of the related formulas, and
identification of the source of the non-associativity of the standard vector
version of the addition formula are addressed.
| [
{
"created": "Mon, 14 Oct 2019 07:18:14 GMT",
"version": "v1"
}
] | 2019-10-16 | [
[
"Kocik",
"Jerzy",
""
]
] | What does it mean to ``add'' velocities relativistically -- clarification of the conceptual problems, new derivations of the related formulas, and identification of the source of the non-associativity of the standard vector version of the addition formula are addressed. |
1406.5652 | Mariafelicia De Laurentis Professor | Salvatore Capozziello, Mariafelicia De Laurentis, Sergei D. Odintsov | Noether Symmetry Approach in Gauss-Bonnet Cosmology | 9 pages, to appear in Mod. Phys. Lett. A | Modern Physics Letters A Volume 29, Issue 30, 28 September 2014 | 10.1142/S0217732314501648 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the Noether Symmetry Approach in the framework of Gauss-Bonnet
cosmology showing that the functional form of the $F(R, {\cal G})$ function,
where $R$ is the Ricci scalar and ${\cal G}$ is the Gauss-Bonnet topological
invariant, can be determined by the presence of symmetries. Besides, the method
allows to find out exact solutions due to the reduction of cosmological
dynamical system and the presence of conserved quantities. Some specific
cosmological models are worked out
| [
{
"created": "Sat, 21 Jun 2014 21:35:11 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Aug 2014 10:03:46 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Aug 2014 12:22:08 GMT",
"version": "v3"
}
] | 2014-11-13 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | We discuss the Noether Symmetry Approach in the framework of Gauss-Bonnet cosmology showing that the functional form of the $F(R, {\cal G})$ function, where $R$ is the Ricci scalar and ${\cal G}$ is the Gauss-Bonnet topological invariant, can be determined by the presence of symmetries. Besides, the method allows to find out exact solutions due to the reduction of cosmological dynamical system and the presence of conserved quantities. Some specific cosmological models are worked out |
2312.12302 | Lu\'is Filipe Costa | L. Filipe O. Costa, Jos\'e Nat\'ario | Relativistic effects cannot explain galactic dynamics | 11 pages, 6 figures. Slightly improved Section III.A.2, footnotes 3
and 5 added, right plot in Fig. 4 corrected, references added. Version to be
submitted | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been suggested in recent literature that non-linear and/or
gravitomagnetic general relativistic effects can play a leading role in
galactic dynamics, partially or totally replacing dark matter. Using the 1+3
"quasi-Maxwell" formalism, we show, on general grounds, such hypothesis to be
impossible.
| [
{
"created": "Tue, 19 Dec 2023 16:21:47 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Mar 2024 17:34:55 GMT",
"version": "v2"
}
] | 2024-03-15 | [
[
"Costa",
"L. Filipe O.",
""
],
[
"Natário",
"José",
""
]
] | It has been suggested in recent literature that non-linear and/or gravitomagnetic general relativistic effects can play a leading role in galactic dynamics, partially or totally replacing dark matter. Using the 1+3 "quasi-Maxwell" formalism, we show, on general grounds, such hypothesis to be impossible. |
gr-qc/9305012 | Ulf Danielsson | Ulf H. Danielsson and Marcelo Schiffer | Quantum Mechanics, Common Sense and the Black Hole Information Paradox | 15 pages, Latex, CERN-TH.6889/93 | Phys.Rev. D48 (1993) 4779-4784 | 10.1103/PhysRevD.48.4779 | null | gr-qc hep-th | null | The purpose of this paper is to analyse, in the light of information theory
and with the arsenal of (elementary) quantum mechanics (EPR correlations,
copying machines, teleportation, mixing produced in sub-systems owing to a
trace operation, etc.) the scenarios available on the market to resolve the
so-called black-hole information paradox. We shall conclude that the only
plausible ones are those where either the unitary evolution of quantum
mechanics is given up, in which information leaks continuously in the course of
black-hole evaporation through non-local processes, or those in which the world
is polluted by an infinite number of meta-stable remnants.
| [
{
"created": "Fri, 14 May 1993 14:02:00 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Danielsson",
"Ulf H.",
""
],
[
"Schiffer",
"Marcelo",
""
]
] | The purpose of this paper is to analyse, in the light of information theory and with the arsenal of (elementary) quantum mechanics (EPR correlations, copying machines, teleportation, mixing produced in sub-systems owing to a trace operation, etc.) the scenarios available on the market to resolve the so-called black-hole information paradox. We shall conclude that the only plausible ones are those where either the unitary evolution of quantum mechanics is given up, in which information leaks continuously in the course of black-hole evaporation through non-local processes, or those in which the world is polluted by an infinite number of meta-stable remnants. |
2306.07715 | Peter Hintz | Peter Hintz | The linearized Einstein equations with sources | 9 pages | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On vacuum spacetimes of general dimension, we study the linearized Einstein
vacuum equations with a spatially compactly supported and (necessarily)
divergence-free source. We prove that the vanishing of appropriate charges of
the source, defined in terms of Killing vector fields on the spacetime, is
necessary and sufficient for solvability within the class of spatially
compactly supported metric perturbations. The proof combines classical results
by Moncrief with the solvability theory of the linearized constraint equations
with control on supports developed by Corvino and Chru\'sciel-Delay.
| [
{
"created": "Tue, 13 Jun 2023 12:06:23 GMT",
"version": "v1"
}
] | 2023-06-14 | [
[
"Hintz",
"Peter",
""
]
] | On vacuum spacetimes of general dimension, we study the linearized Einstein vacuum equations with a spatially compactly supported and (necessarily) divergence-free source. We prove that the vanishing of appropriate charges of the source, defined in terms of Killing vector fields on the spacetime, is necessary and sufficient for solvability within the class of spatially compactly supported metric perturbations. The proof combines classical results by Moncrief with the solvability theory of the linearized constraint equations with control on supports developed by Corvino and Chru\'sciel-Delay. |
gr-qc/9904055 | Jose M. M. Senovilla | G. Bergqvist and J.M.M. Senovilla | On the Causal Propagation of Fields | LaTeX, 9 pages, improved and enlarged version with references added.
To appear as a Letter to Ed. in Clas. Quantum Grav | Class.Quant.Grav.16:L55-L61,1999 | 10.1088/0264-9381/16/10/101 | null | gr-qc hep-th | null | By using geometric methods and superenergy tensors, we find new simple
criteria for the causal propagation of physical fields in spacetimes of any
dimension. The method can be applied easily to many different theories and to
arbitrary fields (such as scalar or electromagnetic ones). In particular, it
provides a conservation theorem of the free gravitational field in all
N-dimensional spacetimes conformally related to Einstein spaces (including
vacuum solutions). In the case of general relativity, our criteria provide
simple proofs and a unified treatment of conservation theorems for neutrinos,
photons, electrons and all other massless and massive free spin n/2 fields. The
uniqueness of the solution to the field equations also follows from our
treatment under certain circumstances.
| [
{
"created": "Wed, 21 Apr 1999 13:51:08 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Aug 1999 17:11:40 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Bergqvist",
"G.",
""
],
[
"Senovilla",
"J. M. M.",
""
]
] | By using geometric methods and superenergy tensors, we find new simple criteria for the causal propagation of physical fields in spacetimes of any dimension. The method can be applied easily to many different theories and to arbitrary fields (such as scalar or electromagnetic ones). In particular, it provides a conservation theorem of the free gravitational field in all N-dimensional spacetimes conformally related to Einstein spaces (including vacuum solutions). In the case of general relativity, our criteria provide simple proofs and a unified treatment of conservation theorems for neutrinos, photons, electrons and all other massless and massive free spin n/2 fields. The uniqueness of the solution to the field equations also follows from our treatment under certain circumstances. |
1401.4344 | John Barrow | John D. Barrow | Cosmology: the search for twenty-four (or more) functions | 12 pages, no figs, typos corrected, extra discussion in Sec. V and in
refs | Phys. Rev. D89, 064022 (2014) | 10.1103/PhysRevD.89.064022 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We enumerate the 4(1+F)+2S independent arbitrary functions of space require
to describe a general relativistic cosmology containing an arbitrary number of
non-interacting fluid (F) and scalar fields (S). Results are also given for
arbitrary space dimension and for higher-order gravity theories, where the
number increases to 16+4F+2S. Both counts are subject to assumptions about
whether the dark energy is a cosmological constant. A more detailed analysis is
provided when global homogeneity is assumed and the functions become constants.
This situation is also studied in the case where the flat and open universes
have compact spatial topologies. This changes the relative generalities
significantly and places new constraints on the types of expansion anisotropy
that are permitted. The most general compact homogeneous universes containing
Friedmann models are spatially flat and described by 8+4F+2S constants.
Comparisons are made with the simple 6-parameter lambda-CDM model and physical
interpretations provided for the parameters needed to describe the most general
cosmological models.
| [
{
"created": "Fri, 17 Jan 2014 13:55:59 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Feb 2014 14:38:45 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Barrow",
"John D.",
""
]
] | We enumerate the 4(1+F)+2S independent arbitrary functions of space require to describe a general relativistic cosmology containing an arbitrary number of non-interacting fluid (F) and scalar fields (S). Results are also given for arbitrary space dimension and for higher-order gravity theories, where the number increases to 16+4F+2S. Both counts are subject to assumptions about whether the dark energy is a cosmological constant. A more detailed analysis is provided when global homogeneity is assumed and the functions become constants. This situation is also studied in the case where the flat and open universes have compact spatial topologies. This changes the relative generalities significantly and places new constraints on the types of expansion anisotropy that are permitted. The most general compact homogeneous universes containing Friedmann models are spatially flat and described by 8+4F+2S constants. Comparisons are made with the simple 6-parameter lambda-CDM model and physical interpretations provided for the parameters needed to describe the most general cosmological models. |
2101.02676 | Klaus Liegener Dr | Benjamin Bahr, Klaus Liegener | Properties of the Hamiltonian Renormalisation and its application to
quantum mechanics on the circle | 16 pages | Class.Quant.Grav. 39 (2022) 7, 075010 | 10.1088/1361-6382/ac5050 | null | gr-qc hep-lat math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Hamiltonian renormalisation group flow of discretised
one-dimensional physical theories. In particular, we investigate the influence
the choice of different embedding maps has on the RG flow and the resulting
continuum limit, and show in which sense they are, and in which sense they are
not equivalent as physical theories. We are furthermore elucidating the
interplay of the RG flow and the algebras operators satisfy, both on the
discrete and the continuum. Further, we propose preferred renormalisation
prescriptions for operator algebras guaranteeing to arrive at preferred
algebraic relations in the continuum, if suitable extension properties are
assumed. Finally, we introduce a weaker form of distributional equivalence, and
show how unitarily inequivalent continuum limits, which arise due to a choice
of different embedding maps, can still be weakly equivalent in that sense.
| [
{
"created": "Thu, 7 Jan 2021 18:35:57 GMT",
"version": "v1"
}
] | 2023-05-05 | [
[
"Bahr",
"Benjamin",
""
],
[
"Liegener",
"Klaus",
""
]
] | We consider the Hamiltonian renormalisation group flow of discretised one-dimensional physical theories. In particular, we investigate the influence the choice of different embedding maps has on the RG flow and the resulting continuum limit, and show in which sense they are, and in which sense they are not equivalent as physical theories. We are furthermore elucidating the interplay of the RG flow and the algebras operators satisfy, both on the discrete and the continuum. Further, we propose preferred renormalisation prescriptions for operator algebras guaranteeing to arrive at preferred algebraic relations in the continuum, if suitable extension properties are assumed. Finally, we introduce a weaker form of distributional equivalence, and show how unitarily inequivalent continuum limits, which arise due to a choice of different embedding maps, can still be weakly equivalent in that sense. |
gr-qc/9605015 | Carlos O. Lousto | Carlos O. Lousto (Univ. Utah) and N. Sanchez (Obs. Paris) | String dynamics in cosmological and black hole backgrounds: The null
string expansion | 17 pages, REVTEX, no figures | Phys.Rev. D54 (1996) 6399-6407 | 10.1103/PhysRevD.54.6399 | null | gr-qc astro-ph hep-th | null | We study the classical dynamics of a bosonic string in the $D$--dimensional
flat Friedmann--Robertson--Walker and Schwarzschild backgrounds. We make a
perturbative development in the string coordinates around a {\it null} string
configuration; the background geometry is taken into account exactly. In the
cosmological case we uncouple and solve the first order fluctuations; the
string time evolution with the conformal gauge world-sheet $\tau$--coordinate
is given by $X^0(\sigma, \tau)=q(\sigma)\tau^{1\over1+2\beta}+c^2B^0(\sigma,
\tau)+\cdots$, $B^0(\sigma,\tau)=\sum_k b_k(\sigma)\tau^k$ where $b_k(\sigma)$
are given by Eqs.\ (3.15), and $\beta$ is the exponent of the conformal factor
in the Friedmann--Robertson--Walker metric, i.e. $R\sim\eta^\beta$. The string
proper size, at first order in the fluctuations, grows like the conformal
factor $R(\eta)$ and the string energy--momentum tensor corresponds to that of
a null fluid. For a string in the black hole background, we study the planar
case, but keep the dimensionality of the spacetime $D$ generic. In the null
string expansion, the radial, azimuthal, and time coordinates $(r,\phi,t)$ are
$r=\sum_n A^1_{n}(\sigma)(-\tau)^{2n/(D+1)}~,$ $\phi=\sum_n
A^3_{n}(\sigma)(-\tau)^{(D-5+2n)/(D+1)}~,$ and $t=\sum_n A^0_{n}
(\sigma)(-\tau)^{1+2n(D-3)/(D+1)}~.$ The first terms of the series represent a
{\it generic} approach to the Schwarzschild singularity at $r=0$. First and
higher order string perturbations contribute with higher powers of $\tau$. The
integrated string energy-momentum tensor corresponds to that of a null fluid in
$D-1$ dimensions. As the string approaches the $r=0$ singularity its proper
size grows indefinitely like $\sim(-\tau)^{-(D-3)/(D+1)}$. We end the paper
giving three particular exact string solutions inside the black hole.
| [
{
"created": "Wed, 8 May 1996 20:21:13 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Lousto",
"Carlos O.",
"",
"Univ. Utah"
],
[
"Sanchez",
"N.",
"",
"Obs. Paris"
]
] | We study the classical dynamics of a bosonic string in the $D$--dimensional flat Friedmann--Robertson--Walker and Schwarzschild backgrounds. We make a perturbative development in the string coordinates around a {\it null} string configuration; the background geometry is taken into account exactly. In the cosmological case we uncouple and solve the first order fluctuations; the string time evolution with the conformal gauge world-sheet $\tau$--coordinate is given by $X^0(\sigma, \tau)=q(\sigma)\tau^{1\over1+2\beta}+c^2B^0(\sigma, \tau)+\cdots$, $B^0(\sigma,\tau)=\sum_k b_k(\sigma)\tau^k$ where $b_k(\sigma)$ are given by Eqs.\ (3.15), and $\beta$ is the exponent of the conformal factor in the Friedmann--Robertson--Walker metric, i.e. $R\sim\eta^\beta$. The string proper size, at first order in the fluctuations, grows like the conformal factor $R(\eta)$ and the string energy--momentum tensor corresponds to that of a null fluid. For a string in the black hole background, we study the planar case, but keep the dimensionality of the spacetime $D$ generic. In the null string expansion, the radial, azimuthal, and time coordinates $(r,\phi,t)$ are $r=\sum_n A^1_{n}(\sigma)(-\tau)^{2n/(D+1)}~,$ $\phi=\sum_n A^3_{n}(\sigma)(-\tau)^{(D-5+2n)/(D+1)}~,$ and $t=\sum_n A^0_{n} (\sigma)(-\tau)^{1+2n(D-3)/(D+1)}~.$ The first terms of the series represent a {\it generic} approach to the Schwarzschild singularity at $r=0$. First and higher order string perturbations contribute with higher powers of $\tau$. The integrated string energy-momentum tensor corresponds to that of a null fluid in $D-1$ dimensions. As the string approaches the $r=0$ singularity its proper size grows indefinitely like $\sim(-\tau)^{-(D-3)/(D+1)}$. We end the paper giving three particular exact string solutions inside the black hole. |
1205.2838 | Alikram Aliev | Alikram N. Aliev, G\"oksel Daylan Esmer, Pamir Talazan | Strong Gravity Effects of Rotating Black Holes: Quasiperiodic
Oscillations | 23 pages, 3 figures, 6 tabels; REVTeX; Some changes made to match
published version | Class. Quantum Grav. 30 (2013) 045010 | 10.1088/0264-9381/30/4/045010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore strong gravity effects of the geodesic motion in the spacetime of
rotating black holes in general relativity and braneworld gravity. We focus on
the description of the motion in terms of three fundamental frequencies: The
orbital frequency, the radial and vertical epicyclic frequencies. For a Kerr
black hole, we perform a detailed numerical analysis of these frequencies at
the innermost stable circular orbits and beyond them as well as at the
characteristic stable orbits, at which the radial epicyclic frequency attains
its highest value. We find that the values of the epicyclic frequencies for a
class of stable orbits exhibit good qualitative agreement with the observed
frequencies of the twin peaks quasiperiodic oscillations (QPOs) in some black
hole binaries. We also find that at the characteristic stable circular orbits,
where the radial (or the vertical) epicyclic frequency has maxima, the vertical
and radial epicyclic frequencies exhibit an approximate 2 : 1 ratio even in the
case of near-extreme rotation of the black hole. Next, we perform a similar
analysis of the fundamental frequencies for a rotating braneworld black hole
and argue that the existence of such a black hole with a negative tidal charge,
whose angular momentum exceeds the Kerr bound in general relativity, does not
confront with the observations of high frequency QPOs.
| [
{
"created": "Sun, 13 May 2012 07:32:47 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Feb 2013 08:54:56 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Aliev",
"Alikram N.",
""
],
[
"Esmer",
"Göksel Daylan",
""
],
[
"Talazan",
"Pamir",
""
]
] | We explore strong gravity effects of the geodesic motion in the spacetime of rotating black holes in general relativity and braneworld gravity. We focus on the description of the motion in terms of three fundamental frequencies: The orbital frequency, the radial and vertical epicyclic frequencies. For a Kerr black hole, we perform a detailed numerical analysis of these frequencies at the innermost stable circular orbits and beyond them as well as at the characteristic stable orbits, at which the radial epicyclic frequency attains its highest value. We find that the values of the epicyclic frequencies for a class of stable orbits exhibit good qualitative agreement with the observed frequencies of the twin peaks quasiperiodic oscillations (QPOs) in some black hole binaries. We also find that at the characteristic stable circular orbits, where the radial (or the vertical) epicyclic frequency has maxima, the vertical and radial epicyclic frequencies exhibit an approximate 2 : 1 ratio even in the case of near-extreme rotation of the black hole. Next, we perform a similar analysis of the fundamental frequencies for a rotating braneworld black hole and argue that the existence of such a black hole with a negative tidal charge, whose angular momentum exceeds the Kerr bound in general relativity, does not confront with the observations of high frequency QPOs. |
1905.13557 | Ian H. Redmount | James M. Starke and Ian H. Redmount | Dynamics of Tachyonic Dark Matter | 18 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Usually considered highly speculative, tachyons can be treated via
straightforward Einsteinian dynamics. Kinetic theory and thermodynamics for a
gas of ``dark'' tachyons are readily constructed. Such a gas exhibits density
and pressure which, for the dominant constituent of a suitable
Friedmann-Robertson-Walker spacetime, can drive cosmic evolution with features
both similar to and distinct from those of a standard dark-energy/dark-matter
model. Hence, tachyons might bear further consideration as a cosmic dark-matter
candidate.
| [
{
"created": "Wed, 29 May 2019 20:39:43 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jun 2022 20:52:15 GMT",
"version": "v2"
}
] | 2022-06-15 | [
[
"Starke",
"James M.",
""
],
[
"Redmount",
"Ian H.",
""
]
] | Usually considered highly speculative, tachyons can be treated via straightforward Einsteinian dynamics. Kinetic theory and thermodynamics for a gas of ``dark'' tachyons are readily constructed. Such a gas exhibits density and pressure which, for the dominant constituent of a suitable Friedmann-Robertson-Walker spacetime, can drive cosmic evolution with features both similar to and distinct from those of a standard dark-energy/dark-matter model. Hence, tachyons might bear further consideration as a cosmic dark-matter candidate. |
1711.01808 | Vee-Liem Saw | Vee-Liem Saw | Bondi mass with a cosmological constant | 29 pages, accepted for publication by Physical Review D | Phys. Rev. D 97, 084017 (2018) | 10.1103/PhysRevD.97.084017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mass loss of an isolated gravitating system due to energy carried away by
gravitational waves with a cosmological constant $\Lambda\in\R$ was recently
worked out, using the Newman-Penrose-Unti approach. In that same article, an
expression for the Bondi mass of the isolated system, $M_\Lambda$, for the
$\Lambda>0$ case was proposed. The stipulated mass $M_\Lambda$ would ensure
that in the absence of any incoming gravitational radiation from elsewhere, the
emitted gravitational waves must carry away a positive-definite energy. That
suggested quantity however, introduced a $\Lambda$-correction term to the Bondi
mass $M_B$ (where $M_B$ is the usual Bondi mass for asymptotically flat
spacetimes) which would involve not just information on the state of the system
at that moment, but ostensibly also its past history. In this paper, we derive
the identical mass-loss equation using an integral formula on a hypersurface
formulated by Frauendiener based on the Nester-Witten identity, and argue that
one may adopt a generalisation of the Bondi mass with $\Lambda\in\R$
\emph{without any correction}, viz. $M_\Lambda=M_B$ for any $\Lambda\in\R$.
Furthermore with $M_\Lambda=M_B$, we show that for \emph{purely quadrupole
gravitational waves} given off by the isolated system (i.e. when the "Bondi
news" $\sigma^o$ comprises only the $l=2$ components of the "spherical
harmonics with spin-weight 2"), the energy carried away is \emph{manifestly
positive-definite} for the $\Lambda>0$ case. For a general $\sigma^o$ having
higher multipole moments, this perspicuous property in the $\Lambda>0$ case
still holds if those $l>2$ contributions are weak --- more precisely, if they
satisfy any of the inequalities given in this paper.
| [
{
"created": "Mon, 6 Nov 2017 10:01:05 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Mar 2018 19:38:36 GMT",
"version": "v2"
}
] | 2018-04-18 | [
[
"Saw",
"Vee-Liem",
""
]
] | The mass loss of an isolated gravitating system due to energy carried away by gravitational waves with a cosmological constant $\Lambda\in\R$ was recently worked out, using the Newman-Penrose-Unti approach. In that same article, an expression for the Bondi mass of the isolated system, $M_\Lambda$, for the $\Lambda>0$ case was proposed. The stipulated mass $M_\Lambda$ would ensure that in the absence of any incoming gravitational radiation from elsewhere, the emitted gravitational waves must carry away a positive-definite energy. That suggested quantity however, introduced a $\Lambda$-correction term to the Bondi mass $M_B$ (where $M_B$ is the usual Bondi mass for asymptotically flat spacetimes) which would involve not just information on the state of the system at that moment, but ostensibly also its past history. In this paper, we derive the identical mass-loss equation using an integral formula on a hypersurface formulated by Frauendiener based on the Nester-Witten identity, and argue that one may adopt a generalisation of the Bondi mass with $\Lambda\in\R$ \emph{without any correction}, viz. $M_\Lambda=M_B$ for any $\Lambda\in\R$. Furthermore with $M_\Lambda=M_B$, we show that for \emph{purely quadrupole gravitational waves} given off by the isolated system (i.e. when the "Bondi news" $\sigma^o$ comprises only the $l=2$ components of the "spherical harmonics with spin-weight 2"), the energy carried away is \emph{manifestly positive-definite} for the $\Lambda>0$ case. For a general $\sigma^o$ having higher multipole moments, this perspicuous property in the $\Lambda>0$ case still holds if those $l>2$ contributions are weak --- more precisely, if they satisfy any of the inequalities given in this paper. |
2001.07268 | Zbigniew Haba | Z.Haba | Stochastic inflaton wave equation from an expanding environment | minor changes, 10 pages | Eur.Phys.Journ.C80,321(2020) | 10.1140/epjc/s10052-020-7877-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the inflaton $\phi$ in an environment of scalar fields $\chi_{n}$
on flat and curved manifolds. We average over the environmental fields
$\chi_{n}$. We study a contribution of superhorizon $k<<aH$ as well as
subhorizon $k>> aH$ modes $\chi_{n}({\bf k})$. As a result we obtain a
stochastic wave equation with a friction and noise. We show that in the
subhorizon regime in field theory a finite number of fields is sufficient to
produce a friction and diffusion owing to the infinite number of degrees of
freedom corresponding to different ${\bf k}$ in $\chi_{n}({\bf k})$. We
investigate the slow roll and the Markovian approximaions to the stochastic
wave equation. A determination of the metric from the stochastic
Einstein-Klein-Gordon equations is briefly discussed,
| [
{
"created": "Mon, 20 Jan 2020 22:24:23 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Apr 2020 19:44:04 GMT",
"version": "v2"
}
] | 2020-04-24 | [
[
"Haba",
"Z.",
""
]
] | We discuss the inflaton $\phi$ in an environment of scalar fields $\chi_{n}$ on flat and curved manifolds. We average over the environmental fields $\chi_{n}$. We study a contribution of superhorizon $k<<aH$ as well as subhorizon $k>> aH$ modes $\chi_{n}({\bf k})$. As a result we obtain a stochastic wave equation with a friction and noise. We show that in the subhorizon regime in field theory a finite number of fields is sufficient to produce a friction and diffusion owing to the infinite number of degrees of freedom corresponding to different ${\bf k}$ in $\chi_{n}({\bf k})$. We investigate the slow roll and the Markovian approximaions to the stochastic wave equation. A determination of the metric from the stochastic Einstein-Klein-Gordon equations is briefly discussed, |
2109.03376 | Qing-Guo Huang | Rong-Zhen Guo, Chen Yuan and Qing-Guo Huang | Near-horizon microstructure and superradiant instability of black holes | 5 pages | null | 10.1103/PhysRevD.105.064029 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Ultralight bosons, as important candidates of dark matter, can condense
around spinning black holes (BHs) to form long-lived ``boson clouds'' due to
superradiance instability. The boson-BH system can be observed through
gravitational wave detection and may become a new window to find traces of
ultralight bosons. In this letter we explore the effects on the superradiant
instability of BHs from the near-horizon microstructure. By introducing the
reflection parameter near a BH horizon, we derived analytical results on the
corrections to both energy levels of bosonic cloud and its characteristic
frequencies of superradiance instability. Our results imply that the evolution
of a boson-BH system and gravitational waves it emits would be influenced by
the near-horizon physics of a BH.
| [
{
"created": "Wed, 8 Sep 2021 00:28:40 GMT",
"version": "v1"
}
] | 2022-04-06 | [
[
"Guo",
"Rong-Zhen",
""
],
[
"Yuan",
"Chen",
""
],
[
"Huang",
"Qing-Guo",
""
]
] | Ultralight bosons, as important candidates of dark matter, can condense around spinning black holes (BHs) to form long-lived ``boson clouds'' due to superradiance instability. The boson-BH system can be observed through gravitational wave detection and may become a new window to find traces of ultralight bosons. In this letter we explore the effects on the superradiant instability of BHs from the near-horizon microstructure. By introducing the reflection parameter near a BH horizon, we derived analytical results on the corrections to both energy levels of bosonic cloud and its characteristic frequencies of superradiance instability. Our results imply that the evolution of a boson-BH system and gravitational waves it emits would be influenced by the near-horizon physics of a BH. |
1001.3569 | Daniela Doneva | Daniela D. Doneva, Stoytcho S. Yazadjiev, Kostas D. Kokkotas, Ivan Zh.
Stefanov, Michail D. Todorov | Charged anti-de Sitter scalar-tensor black holes and their thermodynamic
phase structure | 35 pages, 23 figures; v2: typos corrected, comments and references
added | Phys.Rev.D81:104030,2010 | 10.1103/PhysRevD.81.104030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we numerically construct new charged anti-de Sitter
black holes coupled to nonlinear Born-Infeld electrodynamics within a certain
class of scalar-tensor theories. The properties of the solutions are
investigated both numerically and analytically. We also study the
thermodynamics of the black holes in the canonical ensemble. For large values
of the Born-Infeld parameter and for a certain interval of the charge values we
find the existence of a first-order phase transition between small and very
large black holes. An unexpected result is that for a certain small charge
subinterval two phase transitions have been observed, one of zeroth and one of
first order. It is important to note that such phase transitions are also
observed for pure Einstein-Born-Infeld-AdS black holes.
| [
{
"created": "Wed, 20 Jan 2010 19:47:31 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Feb 2011 19:17:12 GMT",
"version": "v2"
}
] | 2011-02-15 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
],
[
"Kokkotas",
"Kostas D.",
""
],
[
"Stefanov",
"Ivan Zh.",
""
],
[
"Todorov",
"Michail D.",
""
]
] | In the present paper we numerically construct new charged anti-de Sitter black holes coupled to nonlinear Born-Infeld electrodynamics within a certain class of scalar-tensor theories. The properties of the solutions are investigated both numerically and analytically. We also study the thermodynamics of the black holes in the canonical ensemble. For large values of the Born-Infeld parameter and for a certain interval of the charge values we find the existence of a first-order phase transition between small and very large black holes. An unexpected result is that for a certain small charge subinterval two phase transitions have been observed, one of zeroth and one of first order. It is important to note that such phase transitions are also observed for pure Einstein-Born-Infeld-AdS black holes. |
1508.01630 | Ahmet Baykal | Ahmet Baykal and Tekin Dereli | A nonminimally coupled Einstein-Maxwell model in a non-Riemann
space-time with torsion | 1+10 pages, minor corrections to the text, published version | Phys.Rev. D92 (2015) 6, 065018 | 10.1103/PhysRevD.92.065018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A system of field equations for an Einstein-Maxwell model with $RF^2$-type
nonminimal coupling in a non-Riemannian space-time with a non-vanishing torsion
is derived and the resulting field equations are expressed in terms of the
Riemannian quantities based on a metric with a Lorentzian signature. The
torsion is generated by the gradients of the electromagnetic field invariants.
An electromagnetic constitutive tensor is introduced in the formulation of the
field equations.
| [
{
"created": "Fri, 7 Aug 2015 07:43:00 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Oct 2015 06:38:11 GMT",
"version": "v2"
}
] | 2015-10-28 | [
[
"Baykal",
"Ahmet",
""
],
[
"Dereli",
"Tekin",
""
]
] | A system of field equations for an Einstein-Maxwell model with $RF^2$-type nonminimal coupling in a non-Riemannian space-time with a non-vanishing torsion is derived and the resulting field equations are expressed in terms of the Riemannian quantities based on a metric with a Lorentzian signature. The torsion is generated by the gradients of the electromagnetic field invariants. An electromagnetic constitutive tensor is introduced in the formulation of the field equations. |
1205.6269 | Shao-Feng Wu | Xiao-Qing Shen, Shao-Feng Wu, Guo-Hong Yang | Spontaneously induced general relativity with holographic interior and
general exterior | 16 pages, 5 figures; v3: clarification improved, revised version
accepted by PLB | Physics Letters B 716 (2012) pp. 370-376 | 10.1016/j.physletb.2012.08.048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the spontaneously induced general relativity (GR) from the
scalar-tensor gravity. We demonstrate by numerical methods that a novel inner
core can be connected to the Schwarzschild exterior with cosmological constants
and any sectional curvature. Deriving an analytic core metric for a general
exterior, we show that all the nontrivial features of the core, including the
locally holographic entropy packing, are universal for the general exterior in
static spacetimes. We also investigate whether the f(R) gravity can accommodate
the nontrivial core.
| [
{
"created": "Tue, 29 May 2012 05:42:38 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jul 2012 11:33:48 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Aug 2012 08:47:23 GMT",
"version": "v3"
}
] | 2012-09-03 | [
[
"Shen",
"Xiao-Qing",
""
],
[
"Wu",
"Shao-Feng",
""
],
[
"Yang",
"Guo-Hong",
""
]
] | We study the spontaneously induced general relativity (GR) from the scalar-tensor gravity. We demonstrate by numerical methods that a novel inner core can be connected to the Schwarzschild exterior with cosmological constants and any sectional curvature. Deriving an analytic core metric for a general exterior, we show that all the nontrivial features of the core, including the locally holographic entropy packing, are universal for the general exterior in static spacetimes. We also investigate whether the f(R) gravity can accommodate the nontrivial core. |
2103.12319 | Miguel Cruz | V\'ictor H. C\'ardenas, Miguel Cruz and Samuel Lepe | Matter production effects and interacting scenario within a
reconstructed mimetic cosmology for late times | 24 pages, 8 figures, references added. Accepted for publication in
EPJC | Eur. Phys. J. C 81, 631 (2021) | 10.1140/epjc/s10052-021-09442-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore two possible scenarios that can be considered to
extend a recent proposed model by the authors known as reconstructed mimetic
cosmology. This study is complemented with an statistical analysis for each
case. The first scenario considers the inclusion of matter production as a
possible source of cosmic expansion in the reconstructed mimetic model, at
effective level was found that this construction can cross the phantom divide,
the model evolves from quintessence to phantom dark energy. The second scenario
corresponds to a construction of an interacting scheme for the dark sector
which is described by the unified mimetic model. The resulting interaction term
(not imposed by an Ansatz), $Q$, exhibits changes of sign leading to the
violation of the second law along the cosmic evolution and non adiabaticity;
the temperatures for the components of the dark sector are computed and such
components are shown to be out of thermal equilibrium.
| [
{
"created": "Tue, 23 Mar 2021 05:23:51 GMT",
"version": "v1"
},
{
"created": "Fri, 21 May 2021 19:06:02 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Jul 2021 10:21:52 GMT",
"version": "v3"
}
] | 2021-07-23 | [
[
"Cárdenas",
"Víctor H.",
""
],
[
"Cruz",
"Miguel",
""
],
[
"Lepe",
"Samuel",
""
]
] | In this work we explore two possible scenarios that can be considered to extend a recent proposed model by the authors known as reconstructed mimetic cosmology. This study is complemented with an statistical analysis for each case. The first scenario considers the inclusion of matter production as a possible source of cosmic expansion in the reconstructed mimetic model, at effective level was found that this construction can cross the phantom divide, the model evolves from quintessence to phantom dark energy. The second scenario corresponds to a construction of an interacting scheme for the dark sector which is described by the unified mimetic model. The resulting interaction term (not imposed by an Ansatz), $Q$, exhibits changes of sign leading to the violation of the second law along the cosmic evolution and non adiabaticity; the temperatures for the components of the dark sector are computed and such components are shown to be out of thermal equilibrium. |
gr-qc/0407115 | Wei-Tou Ni | Yi-Cheng Huang and Wei-Tou Ni | Propagation of Dirac Wave Functions in Accelerated Frames of Reference | 20 pages | null | null | null | gr-qc | null | The first-order gravity effects of Dirac wave functions are found from the
inertial effects in the accelerated frames of reference. Derivations and
discussions about Lense-Thirring effect and the gyrogravitational ratio for
intrinsic spin are presented. We use coordinate transformations among reference
frames to study and understand the Lense-Thirring effect of a scalar particle.
For a Dirac particle, the wave-function transformation operator from an
inertial frame to a moving accelerated frame is obtained. From this, the Dirac
wave function is solved and its change of polarization gives the
gyrogravitational ratio 1 for the first-order gravitational effects. The
eikonal approach to this problem is presented in the end for ready extension to
investigations involving curvature terms.
| [
{
"created": "Fri, 30 Jul 2004 09:03:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Huang",
"Yi-Cheng",
""
],
[
"Ni",
"Wei-Tou",
""
]
] | The first-order gravity effects of Dirac wave functions are found from the inertial effects in the accelerated frames of reference. Derivations and discussions about Lense-Thirring effect and the gyrogravitational ratio for intrinsic spin are presented. We use coordinate transformations among reference frames to study and understand the Lense-Thirring effect of a scalar particle. For a Dirac particle, the wave-function transformation operator from an inertial frame to a moving accelerated frame is obtained. From this, the Dirac wave function is solved and its change of polarization gives the gyrogravitational ratio 1 for the first-order gravitational effects. The eikonal approach to this problem is presented in the end for ready extension to investigations involving curvature terms. |
gr-qc/0401095 | Banibrata Mukhopadhyay | Banibrata Mukhopadhyay | Neutrino asymmetry in presence of gravitational interaction | 3 latex pages; to appear in the proceedings of X Marcel Grossmann
Meeting, Rio de Janeiro, 20-26 July 2003; on the basis of talk presented | null | 10.1142/9789812704030_0078 | null | gr-qc astro-ph hep-ph | null | Propagation of fermions in curved space-time generates a gravitational
interaction due to the coupling between spin of the fermion and space-time
curvature. This gravitational interaction, which is an axial-vector appears as
the CPT violating term in the Lagrangian, can generate the neutrino asymmetry
in Universe. If the back-ground metric is spherically asymmetric, say, of
rotating black hole, the axisymmetric space-time of an expanding Universe, this
interaction as well as the neutrino asymmetry is non-zero.
| [
{
"created": "Thu, 22 Jan 2004 10:26:56 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Feb 2004 19:38:53 GMT",
"version": "v2"
}
] | 2016-11-09 | [
[
"Mukhopadhyay",
"Banibrata",
""
]
] | Propagation of fermions in curved space-time generates a gravitational interaction due to the coupling between spin of the fermion and space-time curvature. This gravitational interaction, which is an axial-vector appears as the CPT violating term in the Lagrangian, can generate the neutrino asymmetry in Universe. If the back-ground metric is spherically asymmetric, say, of rotating black hole, the axisymmetric space-time of an expanding Universe, this interaction as well as the neutrino asymmetry is non-zero. |
gr-qc/0207109 | Juan P. Pertierra | C.B. Hart, R. Held, P.K. Hoiland, S. Jenks, F. Loup, D. Martins, J.
Nyman, J.P. Pertierra, P.A. Santos, M.A. Shore, R. Sims, M. Stabno, T.O.M.
Teage | On the Problems of Hazardous Matter and Radiation at Faster than Light
Speeds in the Warp Drive Space-Time | 9 pages | null | null | null | gr-qc | null | The problems of hazardous radiation and collisions with matter on a warp
driven ship pose considerable obstacles to this possibility for interstellar
travel. A solution to these problems lies in the Broeck metric. It is
demonstrated that both threats to the ship will be greatly reduced. It is also
shown that the horizon problem no longer exists.
| [
{
"created": "Sat, 27 Jul 2002 05:06:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hart",
"C. B.",
""
],
[
"Held",
"R.",
""
],
[
"Hoiland",
"P. K.",
""
],
[
"Jenks",
"S.",
""
],
[
"Loup",
"F.",
""
],
[
"Martins",
"D.",
""
],
[
"Nyman",
"J.",
""
],
[
"Pertierra",
"J. P.",
... | The problems of hazardous radiation and collisions with matter on a warp driven ship pose considerable obstacles to this possibility for interstellar travel. A solution to these problems lies in the Broeck metric. It is demonstrated that both threats to the ship will be greatly reduced. It is also shown that the horizon problem no longer exists. |
1503.02063 | Hannu Nyrhinen | Tomi Koivisto and Hannu J. Nyrhinen | Stability of disformally coupled accretion disks | 14 pages, 6 figures, abstract and introduction rewritten, typos
corrected | Phys. Scr. 92 105301 (2017) | 10.1088/1402-4896/aa85cc | NORDITA-2015-28, HIP-2015-10/TH | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The no-hair theorem postulates that the only externally observable properties
of a black hole are its mass, its electric charge, and its angular momentum. In
scalar-tensor theories of gravity, a matter distribution around a black hole
can lead to the so called "spontaneous scalarisation" instability that triggers
the development of scalar hair. In the Brans-Dicke type theories, this effect
can be understood as a result of tachyonic effective mass of the scalar field.
Here we consider the instability in the generalised class of scalar-theories
that feature non-conformal, i.e. "disformal", couplings to matter. Such
theories have gained considerable interest in the recent years and have been
studied in a wide variety of systems, both cosmological and astrophysical. In
view of the prospects of gravitational wave astronomy, it is relevant to
explore the implications of the theories in the strong-gravity regime. In this
article, we concentrate on the spontaneous scalarisation of matter
configurations around Schwarzschild and Kerr black holes. We find that in the
more generic scalar-tensor theories, the instability of the Brans-Dicke theory
can be enhanced, suggesting violations of the no-hair theorem. On the other
hand, we find that, especially if the coupling is very strong, or if the
gradients in the matter distribution are negligible, the disformal coupling
tends to stabilise the system.
| [
{
"created": "Fri, 6 Mar 2015 20:44:21 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jun 2015 17:11:07 GMT",
"version": "v2"
},
{
"created": "Sun, 20 Aug 2017 14:29:58 GMT",
"version": "v3"
}
] | 2017-09-14 | [
[
"Koivisto",
"Tomi",
""
],
[
"Nyrhinen",
"Hannu J.",
""
]
] | The no-hair theorem postulates that the only externally observable properties of a black hole are its mass, its electric charge, and its angular momentum. In scalar-tensor theories of gravity, a matter distribution around a black hole can lead to the so called "spontaneous scalarisation" instability that triggers the development of scalar hair. In the Brans-Dicke type theories, this effect can be understood as a result of tachyonic effective mass of the scalar field. Here we consider the instability in the generalised class of scalar-theories that feature non-conformal, i.e. "disformal", couplings to matter. Such theories have gained considerable interest in the recent years and have been studied in a wide variety of systems, both cosmological and astrophysical. In view of the prospects of gravitational wave astronomy, it is relevant to explore the implications of the theories in the strong-gravity regime. In this article, we concentrate on the spontaneous scalarisation of matter configurations around Schwarzschild and Kerr black holes. We find that in the more generic scalar-tensor theories, the instability of the Brans-Dicke theory can be enhanced, suggesting violations of the no-hair theorem. On the other hand, we find that, especially if the coupling is very strong, or if the gradients in the matter distribution are negligible, the disformal coupling tends to stabilise the system. |
1802.04795 | Cristobal Corral | Yuri Bonder and Cristobal Corral | Unimodular Einstein--Cartan gravity: Dynamics and conservation laws | 8 pages, 1 Appendix, matches published version | Phys. Rev. D 97, 084001 (2018) | 10.1103/PhysRevD.97.084001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unimodular gravity is an interesting approach to address the cosmological
constant problem, since the vacuum energy density of quantum fields does not
gravitate in this framework, and the cosmological constant appears as an
integration constant. These features arise as a consequence of considering a
constrained volume element 4-form that breaks the diffeomorphisms invariance
down to volume preserving diffeomorphisms. In this work, the first-order
formulation of unimodular gravity is presented by considering the spin density
of matter fields as a source of spacetime torsion. Even though the most general
matter Lagrangian allowed by the symmetries is considered, dynamical
restrictions arise on their functional dependence. The field equations are
obtained and the conservation laws associated with the symmetries are derived.
It is found that, analogous to torsion-free unimodular gravity, the field
equation for the vierbein is traceless; nevertheless, torsion is algebraically
related to the spin density as in standard Einstein-Cartan theory. The
particular example of massless Dirac spinors is studied, and comparisons with
standard Einstein-Cartan theory are shown.
| [
{
"created": "Tue, 13 Feb 2018 18:58:45 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Apr 2018 18:31:15 GMT",
"version": "v2"
}
] | 2018-04-11 | [
[
"Bonder",
"Yuri",
""
],
[
"Corral",
"Cristobal",
""
]
] | Unimodular gravity is an interesting approach to address the cosmological constant problem, since the vacuum energy density of quantum fields does not gravitate in this framework, and the cosmological constant appears as an integration constant. These features arise as a consequence of considering a constrained volume element 4-form that breaks the diffeomorphisms invariance down to volume preserving diffeomorphisms. In this work, the first-order formulation of unimodular gravity is presented by considering the spin density of matter fields as a source of spacetime torsion. Even though the most general matter Lagrangian allowed by the symmetries is considered, dynamical restrictions arise on their functional dependence. The field equations are obtained and the conservation laws associated with the symmetries are derived. It is found that, analogous to torsion-free unimodular gravity, the field equation for the vierbein is traceless; nevertheless, torsion is algebraically related to the spin density as in standard Einstein-Cartan theory. The particular example of massless Dirac spinors is studied, and comparisons with standard Einstein-Cartan theory are shown. |
1608.02283 | Istvan Racz | Istv\'an R\'acz | Can we prescribe the physical parameters of multiple black holes? | updated to the published version | Mathematics 9, no. 24: 3170 (2021) | 10.3390/math9243170 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The parabolic-hyperbolic form of the constraints and superposed Kerr-Schild
black holes have already been used to provide a radically new initialization of
binary black hole configurations. The method generalizes straightforwardly to
multiple black hole systems. This paper is to verify that each of the global
Arnowitt-Deser-Misner quantities of the constructed multiple black hole initial
data can always be prescribed, as desired, in advance of solving the
constraints. These global charges are shown to be uniquely determined by the
physical parameters of the involved individual Kerr-Schild black holes.
| [
{
"created": "Sun, 7 Aug 2016 23:53:00 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Aug 2016 15:13:09 GMT",
"version": "v2"
},
{
"created": "Sun, 20 Nov 2016 17:55:23 GMT",
"version": "v3"
},
{
"created": "Mon, 6 Feb 2017 21:38:28 GMT",
"version": "v4"
},
{
"cre... | 2021-12-10 | [
[
"Rácz",
"István",
""
]
] | The parabolic-hyperbolic form of the constraints and superposed Kerr-Schild black holes have already been used to provide a radically new initialization of binary black hole configurations. The method generalizes straightforwardly to multiple black hole systems. This paper is to verify that each of the global Arnowitt-Deser-Misner quantities of the constructed multiple black hole initial data can always be prescribed, as desired, in advance of solving the constraints. These global charges are shown to be uniquely determined by the physical parameters of the involved individual Kerr-Schild black holes. |
1304.0529 | Shahar Hod | Shahar Hod | Asymptotic spectrum of the oblate spin-weighted spheroidal harmonics: a
WKB analysis | 4 pages | Physics Letters B 717, 462 (2012) | 10.1016/j.physletb.2012.09.057 | null | gr-qc astro-ph.HE hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin-weighted spheroidal harmonics play a central role in the mathematical
description of diverse physical phenomena, including black-hole perturbation
theory and wave scattering. We present a novel and compact derivation of the
asymptotic eigenvalues of these important functions. Our analysis is based on a
simple trick which transforms the corresponding spin-weighted spheroidal
angular equation into a Schr\"odinger-like wave equation which is amenable to a
standard WKB analysis.
| [
{
"created": "Tue, 2 Apr 2013 04:47:33 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Hod",
"Shahar",
""
]
] | Spin-weighted spheroidal harmonics play a central role in the mathematical description of diverse physical phenomena, including black-hole perturbation theory and wave scattering. We present a novel and compact derivation of the asymptotic eigenvalues of these important functions. Our analysis is based on a simple trick which transforms the corresponding spin-weighted spheroidal angular equation into a Schr\"odinger-like wave equation which is amenable to a standard WKB analysis. |
gr-qc/0105097 | Donald C. Salisbury | Donald C. Salisbury | Quantum general invariance and loop gravity | To appear in Foundations of Physics | Found.Phys. 31 (2001) 1105-1118 | null | null | gr-qc | null | A quantum physical projector is proposed for generally covariant theories
which are derivable from a Lagrangian. The projector is the quantum analogue of
the integral over the generators of finite one-parameter subgroups of the gauge
symmetry transformations which are connected to the identity. Gauge variables
are retained in this formalism, thus permitting the construction of spacetime
area and volume operators in a tentative spacetime loop formulation of quantum
general relativity.
| [
{
"created": "Sun, 27 May 2001 06:04:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Salisbury",
"Donald C.",
""
]
] | A quantum physical projector is proposed for generally covariant theories which are derivable from a Lagrangian. The projector is the quantum analogue of the integral over the generators of finite one-parameter subgroups of the gauge symmetry transformations which are connected to the identity. Gauge variables are retained in this formalism, thus permitting the construction of spacetime area and volume operators in a tentative spacetime loop formulation of quantum general relativity. |
gr-qc/0609024 | Tanmay Vachaspati | Tanmay Vachaspati, Dejan Stojkovic and Lawrence M. Krauss | Observation of Incipient Black Holes and the Information Loss Problem | 15 pages; 9 figures. Changes made in response to referee's comments
and to clarify arguments, in particular to describe clearly that the results
represent observations made by an asymptotic observer. Accepted for
publication in Phys. Rev. D | Phys.Rev.D76:024005,2007 | 10.1103/PhysRevD.76.024005 | null | gr-qc astro-ph hep-ph hep-th | null | We study the formation of black holes by spherical domain wall collapse as
seen by an asymptotic observer, using the functional Schrodinger formalism. To
explore what signals such observers will see, we study radiation of a scalar
quantum field in the collapsing domain wall background. The total energy flux
radiated diverges when backreaction of the radiation on the collapsing wall is
ignored, and the domain wall is seen by the asymptotic observer to evaporate by
non-thermal ``pre-Hawking radiation'' during the collapse process. Evaporation
by pre-Hawking radiation implies that an asymptotic observer can never lose
objects down a black hole. Together with the non-thermal nature of the
radiation, this may resolve the black hole information loss problem.
| [
{
"created": "Thu, 7 Sep 2006 11:06:26 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Oct 2006 01:29:50 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jun 2007 15:01:01 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Vachaspati",
"Tanmay",
""
],
[
"Stojkovic",
"Dejan",
""
],
[
"Krauss",
"Lawrence M.",
""
]
] | We study the formation of black holes by spherical domain wall collapse as seen by an asymptotic observer, using the functional Schrodinger formalism. To explore what signals such observers will see, we study radiation of a scalar quantum field in the collapsing domain wall background. The total energy flux radiated diverges when backreaction of the radiation on the collapsing wall is ignored, and the domain wall is seen by the asymptotic observer to evaporate by non-thermal ``pre-Hawking radiation'' during the collapse process. Evaporation by pre-Hawking radiation implies that an asymptotic observer can never lose objects down a black hole. Together with the non-thermal nature of the radiation, this may resolve the black hole information loss problem. |
0803.0518 | Joel Saavedra | Samuel Lepe, Francisco Pe\~na and Joel Saavedra | Randall-Sundrum model with $\lambda<0$ and bulk brane viscosity | 4 pages. Submitted to PLB | Phys.Lett.B662:217-219,2008 | 10.1016/j.physletb.2008.03.016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effect of the inclusion of bulk brane viscosity on brane world
(BW) cosmology in the framework of the Eckart's theory, we focus in the
Randall-Sundrum model with negative tension on the brane.
| [
{
"created": "Tue, 4 Mar 2008 18:55:37 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lepe",
"Samuel",
""
],
[
"Peña",
"Francisco",
""
],
[
"Saavedra",
"Joel",
""
]
] | We study the effect of the inclusion of bulk brane viscosity on brane world (BW) cosmology in the framework of the Eckart's theory, we focus in the Randall-Sundrum model with negative tension on the brane. |
1511.00572 | Gopi Kant Goswami Dr | G. K. Goswami, R. N. Dewangan, Anil Kumar Yadav | $\Lambda$-CDM type Heckmann - Suchuking model and union 2.1 compilation | 9 pages, 5 figures | Gravitation & Cosmology (Springer),Vol. 22, 388 - 393 (2016) | 10.1134/S0202289316040083 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have investigated $\Lambda$CDM type cosmological model in
Heckmann-Schucking space-time, by using 287 high red shift ($ .3 \leq z \leq
1.4$ ) SN Ia data of observed absolute magnitude along with their possible
error from Union 2.1 compilation. We have used $\chi^{2}$ test to compare Union
2.1 compilation observed data and corresponding theoretical values of apparent
magnitude $(m)$. It is found that the best fit value for $(\Omega_{m})_0$,
$(\Omega_{\Lambda})_0$ and $(\Omega_{\sigma})_0$ are $0.2940$, $0.7058$ and
$0.0002$ respectively and the derived model represents the features of
accelerating universe which is consistent with recent astrophysical
observations.
| [
{
"created": "Sun, 18 Oct 2015 05:37:55 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Feb 2016 14:19:55 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Oct 2016 14:57:58 GMT",
"version": "v3"
}
] | 2016-11-01 | [
[
"Goswami",
"G. K.",
""
],
[
"Dewangan",
"R. N.",
""
],
[
"Yadav",
"Anil Kumar",
""
]
] | In this paper, we have investigated $\Lambda$CDM type cosmological model in Heckmann-Schucking space-time, by using 287 high red shift ($ .3 \leq z \leq 1.4$ ) SN Ia data of observed absolute magnitude along with their possible error from Union 2.1 compilation. We have used $\chi^{2}$ test to compare Union 2.1 compilation observed data and corresponding theoretical values of apparent magnitude $(m)$. It is found that the best fit value for $(\Omega_{m})_0$, $(\Omega_{\Lambda})_0$ and $(\Omega_{\sigma})_0$ are $0.2940$, $0.7058$ and $0.0002$ respectively and the derived model represents the features of accelerating universe which is consistent with recent astrophysical observations. |
1101.3933 | Vladimir Kobelev V. | V. Kobelev | The variant of post-Newtonian mechanics with generalized fractional
derivatives | null | CHAOS 16, 043117 (2006) | 10.1063/1.2384864 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we investigate mathematically the variant of post-Newtonian
mechanics using generalized fractional derivatives. The relativistic-covariant
generalization of the classical equations for gravitational field is studied.
The equations match to (i) the weak Newtonian limit on the moderate scales,
(ii) deliver a potential higher, that Newtonian, on certain, large-distance
characteristic scales. The perturbation of the gravitational field results in
the tiny secular perihelion shift and exhibits some unusual effects on large
scales. The general representation of the solution for fractional wave equation
is given in form of retarded potentials. The solutions for the Riesz wave
equation and classical wave equation are clearly distinctive in an important
sense. The Riesz wave demonstrates the space diffusion of gravitational wave at
the scales of metric constant. The diffusion leads to the blur of the peak and
disruption of the sharp wave front. This contrasts with the solution of
D'Alembert classi-cal wave equation, which obeys the Huygens principle and does
not diffuse.
| [
{
"created": "Thu, 20 Jan 2011 15:31:56 GMT",
"version": "v1"
}
] | 2011-01-21 | [
[
"Kobelev",
"V.",
""
]
] | In this article we investigate mathematically the variant of post-Newtonian mechanics using generalized fractional derivatives. The relativistic-covariant generalization of the classical equations for gravitational field is studied. The equations match to (i) the weak Newtonian limit on the moderate scales, (ii) deliver a potential higher, that Newtonian, on certain, large-distance characteristic scales. The perturbation of the gravitational field results in the tiny secular perihelion shift and exhibits some unusual effects on large scales. The general representation of the solution for fractional wave equation is given in form of retarded potentials. The solutions for the Riesz wave equation and classical wave equation are clearly distinctive in an important sense. The Riesz wave demonstrates the space diffusion of gravitational wave at the scales of metric constant. The diffusion leads to the blur of the peak and disruption of the sharp wave front. This contrasts with the solution of D'Alembert classi-cal wave equation, which obeys the Huygens principle and does not diffuse. |
2111.03243 | Kota Ogasawara | Kota Ogasawara, Takahisa Igata | Photon escape in the extremal Kerr black hole spacetime | 17pages, 23figures | null | 10.1103/PhysRevD.105.024031 | KUNS-2900, KEK-Cosmo-0279, KEK-TH-2363 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider necessary and sufficient conditions for photons emitted from an
arbitrary spacetime position of the extremal Kerr black hole to escape to
infinity. The radial equation of motion determines the necessary conditions for
photons emitted from $r=r_*$ to escape to infinity, and the polar angle
equation of motion further restricts the allowed region of photon motion. From
these two conditions, we provide a method to visualize a two-dimensional photon
impact parameter space that allows photons to escape to infinity, i.e., the
escapable region. Finally, we completely identify the escapable region for the
extremal Kerr black hole spacetime. This study has generalized our previous
result [K.~Ogasawara and T.~Igata, Phys. Rev. D \textbf{103}, 044029 (2021)],
which focused only on light sources near the horizon, to the classification
covering light sources in the entire region.
| [
{
"created": "Fri, 5 Nov 2021 03:41:49 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jan 2022 10:15:23 GMT",
"version": "v2"
}
] | 2022-01-19 | [
[
"Ogasawara",
"Kota",
""
],
[
"Igata",
"Takahisa",
""
]
] | We consider necessary and sufficient conditions for photons emitted from an arbitrary spacetime position of the extremal Kerr black hole to escape to infinity. The radial equation of motion determines the necessary conditions for photons emitted from $r=r_*$ to escape to infinity, and the polar angle equation of motion further restricts the allowed region of photon motion. From these two conditions, we provide a method to visualize a two-dimensional photon impact parameter space that allows photons to escape to infinity, i.e., the escapable region. Finally, we completely identify the escapable region for the extremal Kerr black hole spacetime. This study has generalized our previous result [K.~Ogasawara and T.~Igata, Phys. Rev. D \textbf{103}, 044029 (2021)], which focused only on light sources near the horizon, to the classification covering light sources in the entire region. |
2307.14555 | Hyerim Noh | Jai-chan Hwang and Hyerim Noh | Maxwell equations in curved spacetime | 12 pages, no figure, published in Eur. Phys. J. C | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In curved spacetime, Maxwell's equations can be expressed in forms valid in
Minkowski background, with the effect of the metric (gravity) appearing as
effective polarizations and magnetizations. The electric and magnetic (EM)
fields depend on the observer's frame four-vector. We derive Maxwell's
equations valid in general curved spacetime using the fields defined in the
normal frame, the coordinate frame, and two other non-covariant methods used in
the literature. By analyzing the case in the generic frame we show that the EM
fields, as well as the charge and current densities, defined in non-covariant
ways do not correspond to physical ones measured by an observer. We show that
modification of the homogeneous part is inevitable to any observer, and such a
modification is difficult to interpret as the effective medium property. The
normal frame is the relevant one to use as it gives the EM fields measured by
an Eulerian observer.
| [
{
"created": "Thu, 27 Jul 2023 00:30:00 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Dec 2023 00:01:00 GMT",
"version": "v2"
}
] | 2023-12-25 | [
[
"Hwang",
"Jai-chan",
""
],
[
"Noh",
"Hyerim",
""
]
] | In curved spacetime, Maxwell's equations can be expressed in forms valid in Minkowski background, with the effect of the metric (gravity) appearing as effective polarizations and magnetizations. The electric and magnetic (EM) fields depend on the observer's frame four-vector. We derive Maxwell's equations valid in general curved spacetime using the fields defined in the normal frame, the coordinate frame, and two other non-covariant methods used in the literature. By analyzing the case in the generic frame we show that the EM fields, as well as the charge and current densities, defined in non-covariant ways do not correspond to physical ones measured by an observer. We show that modification of the homogeneous part is inevitable to any observer, and such a modification is difficult to interpret as the effective medium property. The normal frame is the relevant one to use as it gives the EM fields measured by an Eulerian observer. |
gr-qc/0205068 | Tatyana P. Shestakova | T. P. Shestakova | Quantum geometrodynamical description of the Universe in different
reference frames | LaTeX, 6 pages, talk presented at the V International Conference on
Gravitation and Astrophysics of Asian-Pacific countries, Moscow, October 2001 | Grav.Cosmol.Suppl. 8N2 (2002) 140-142 | null | null | gr-qc | null | Several years ago the so-called quantum geometrodynamics in extended phase
space was proposed. The main role in this version of quantum geometrodynamics
is given to a wave function that carries information about geometry of the
Universe as well as about a reference frame in which this geometry is studied.
We consider the evolution of a physical object (the Universe) in ``physical''
subspace of extended configurational space, the latter including gauge and
ghost degrees of freedom. A measure of the ``physical'' subspace depends on a
chosen reference frame, in particular, a small variation of a gauge-fixing
function results in changing the measure. Thus, a transition to another gauge
condition (another reference frame) leads to non-unitary transformation of a
physical part of the wave function. From the viewpoint of the evolution of the
Universe in the ``physical'' subspace a transition to another reference frame
is an irreversible process that may be important when spacetime manifold has a
nontrivial topology.
| [
{
"created": "Thu, 16 May 2002 10:58:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shestakova",
"T. P.",
""
]
] | Several years ago the so-called quantum geometrodynamics in extended phase space was proposed. The main role in this version of quantum geometrodynamics is given to a wave function that carries information about geometry of the Universe as well as about a reference frame in which this geometry is studied. We consider the evolution of a physical object (the Universe) in ``physical'' subspace of extended configurational space, the latter including gauge and ghost degrees of freedom. A measure of the ``physical'' subspace depends on a chosen reference frame, in particular, a small variation of a gauge-fixing function results in changing the measure. Thus, a transition to another gauge condition (another reference frame) leads to non-unitary transformation of a physical part of the wave function. From the viewpoint of the evolution of the Universe in the ``physical'' subspace a transition to another reference frame is an irreversible process that may be important when spacetime manifold has a nontrivial topology. |
1601.00471 | Julio Cesar Fabris | Manuel E. Rodrigues, Julio C. Fabris, Ednaldo L. B. Junior, Glauber T.
Marques | Generalization of Regular Black Holes in General Relativity to $f(R)$
Gravity | Latex file, 11 pages, 5 figures in eps format | null | 10.1140/epjc/s10052-016-4085-x | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we determine regular black hole solutions using a very general
$f(R)$ theory, coupled to a non-linear electromagnetic field given by a
Lagrangian $\mathcal{L}_{NED}$. The functions $f(R)$ and $\mathcal{L}_{NED}$
are left in principle unspecified. Instead, the model is constructed through a
choice of the mass function $M(r)$ presented in the metric coefficients.
Solutions which have a regular behaviour of the geometric invariants are found.
These solutions have two horizons, the event horizon and the Cauchy horizon.
All energy conditions are satisfied in the whole space-time, except the strong
energy condition (SEC) which is violated near the Cauchy horizon.
| [
{
"created": "Mon, 4 Jan 2016 12:13:36 GMT",
"version": "v1"
}
] | 2016-05-25 | [
[
"Rodrigues",
"Manuel E.",
""
],
[
"Fabris",
"Julio C.",
""
],
[
"Junior",
"Ednaldo L. B.",
""
],
[
"Marques",
"Glauber T.",
""
]
] | In this paper, we determine regular black hole solutions using a very general $f(R)$ theory, coupled to a non-linear electromagnetic field given by a Lagrangian $\mathcal{L}_{NED}$. The functions $f(R)$ and $\mathcal{L}_{NED}$ are left in principle unspecified. Instead, the model is constructed through a choice of the mass function $M(r)$ presented in the metric coefficients. Solutions which have a regular behaviour of the geometric invariants are found. These solutions have two horizons, the event horizon and the Cauchy horizon. All energy conditions are satisfied in the whole space-time, except the strong energy condition (SEC) which is violated near the Cauchy horizon. |
gr-qc/0405016 | Bernd Reimann | Bernd Reimann | Slice Stretching at the Event Horizon when Geodesically Slicing the
Schwarzschild Spacetime with Excision | 5 pages, 2 figures, published version including minor amendments
suggested by the referee | Class.Quant.Grav. 21 (2004) 4297-4304 | 10.1088/0264-9381/21/18/002 | AEI-2004-039 | gr-qc | null | Slice-stretching effects are discussed as they arise at the event horizon
when geodesically slicing the extended Schwarzschild black-hole spacetime while
using singularity excision. In particular, for Novikov and isotropic spatial
coordinates the outward movement of the event horizon (``slice sucking'') and
the unbounded growth there of the radial metric component (``slice wrapping'')
are analyzed. For the overall slice stretching, very similar late time behavior
is found when comparing with maximal slicing. Thus, the intuitive argument that
attributes slice stretching to singularity avoidance is incorrect.
| [
{
"created": "Tue, 4 May 2004 21:53:13 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Aug 2004 21:21:55 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Reimann",
"Bernd",
""
]
] | Slice-stretching effects are discussed as they arise at the event horizon when geodesically slicing the extended Schwarzschild black-hole spacetime while using singularity excision. In particular, for Novikov and isotropic spatial coordinates the outward movement of the event horizon (``slice sucking'') and the unbounded growth there of the radial metric component (``slice wrapping'') are analyzed. For the overall slice stretching, very similar late time behavior is found when comparing with maximal slicing. Thus, the intuitive argument that attributes slice stretching to singularity avoidance is incorrect. |
gr-qc/0502098 | Dinesh Singh | Dinesh Singh, Nader Mobed, Giorgio Papini | Neutrino Wave Packet Propagation in Gravitational Fields | Updated with more details; 9 pages, 8 figures | Phys.Lett.A351:373-378,2006 | 10.1016/j.physleta.2005.11.032 | null | gr-qc hep-ph hep-th | null | We discuss the propagation of neutrino wave packets in a Lense-Thirring
space-time using a gravitational phase approach. We show that the neutrino
oscillation length is altered by gravitational corrections and that neutrinos
are subject to helicity flip induced by stellar rotation. For the case of a
rapidly rotating neutron star, we show that absolute neutrino masses can be
derived, in principle, from rotational contributions to the mass-induced energy
shift, without recourse to mass generation models presently discussed in the
literature.
| [
{
"created": "Wed, 23 Feb 2005 15:31:15 GMT",
"version": "v1"
},
{
"created": "Thu, 12 May 2005 23:58:24 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Singh",
"Dinesh",
""
],
[
"Mobed",
"Nader",
""
],
[
"Papini",
"Giorgio",
""
]
] | We discuss the propagation of neutrino wave packets in a Lense-Thirring space-time using a gravitational phase approach. We show that the neutrino oscillation length is altered by gravitational corrections and that neutrinos are subject to helicity flip induced by stellar rotation. For the case of a rapidly rotating neutron star, we show that absolute neutrino masses can be derived, in principle, from rotational contributions to the mass-induced energy shift, without recourse to mass generation models presently discussed in the literature. |
2207.08687 | Bibhas Majhi Ranjan | Partha Nandi, Sounak Pal, Sayan Kumar Pal, Bibhas Ranjan Majhi | Low frequency gravitational waves emerge Berry phase | Revised version, title changed, to appear in Phys. Rev. D | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of low frequency gravitational waves (LFGWs) astronomy has
marked an advent of new era in the domain of astrophysics and general
relativity. Using the framework of interaction between GWs and a point
two-particles like detector, within linearized gravity approach, we propose a
toy detector model whose quantum state is being investigated at a low-frequency
of GWs. The detector is in simultaneous interaction with GWs and an external
time-dependent (tuneable) two-dimensional harmonic potential. We observe that
the interaction with low frequency GWs naturally provides adiabatic
approximation in the calculation, and thereby can lead to a quantal geometric
phase in the quantum states of the detector. Moreover this can be controlled by
tuning the frequency of the external harmonic potential trap. We argue that
such geometric phase detection may serve as a manifestation of the footprint of
GWs. More importantly, our theoretical model may be capable of providing a
layout for the detection of very small frequency GWs through Berry phase.
| [
{
"created": "Mon, 18 Jul 2022 15:37:16 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Nov 2023 07:26:47 GMT",
"version": "v2"
}
] | 2023-11-29 | [
[
"Nandi",
"Partha",
""
],
[
"Pal",
"Sounak",
""
],
[
"Pal",
"Sayan Kumar",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | The detection of low frequency gravitational waves (LFGWs) astronomy has marked an advent of new era in the domain of astrophysics and general relativity. Using the framework of interaction between GWs and a point two-particles like detector, within linearized gravity approach, we propose a toy detector model whose quantum state is being investigated at a low-frequency of GWs. The detector is in simultaneous interaction with GWs and an external time-dependent (tuneable) two-dimensional harmonic potential. We observe that the interaction with low frequency GWs naturally provides adiabatic approximation in the calculation, and thereby can lead to a quantal geometric phase in the quantum states of the detector. Moreover this can be controlled by tuning the frequency of the external harmonic potential trap. We argue that such geometric phase detection may serve as a manifestation of the footprint of GWs. More importantly, our theoretical model may be capable of providing a layout for the detection of very small frequency GWs through Berry phase. |
2105.08523 | Faizuddin Ahmed | Faizuddin Ahmed | Type III Spacetime with Closed Timelike Curves | 10 pages, no figure, appeared in PROGRESS IN PHYSICS (PiP) Volume 12,
Issue 4 (October), pp. 329-331 (2016), http://www.ptep-online.com | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a cyclic symmetric space-time, admitting closed time-like curves
(CTCs) which appear after a certain instant of time, i. e., a time-machine
space-time. These closed time-like curves evolve from an initial spacelike
hypersurface on the plane $z$=constant in a causally well-behaved manner. The
space-time discussed here is free from curvature singularities and a 4D
generalization of the Misner space in curved space-time. The matter field is of
pure radiation with a negative cosmological constant
| [
{
"created": "Mon, 17 May 2021 07:13:41 GMT",
"version": "v1"
}
] | 2021-05-19 | [
[
"Ahmed",
"Faizuddin",
""
]
] | We present a cyclic symmetric space-time, admitting closed time-like curves (CTCs) which appear after a certain instant of time, i. e., a time-machine space-time. These closed time-like curves evolve from an initial spacelike hypersurface on the plane $z$=constant in a causally well-behaved manner. The space-time discussed here is free from curvature singularities and a 4D generalization of the Misner space in curved space-time. The matter field is of pure radiation with a negative cosmological constant |
0806.3065 | Juri Agresti | Juri Agresti | Researches on Non-standard Optics for Advanced Gravitational Waves
Interferometers | Ph.D. thesis, University of Pisa & LIGO-Caltech, 185 pages | null | null | LIGO-P080010-00-R | gr-qc physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis presents a collection of different researches on non-standard
optics in view of enhancing the performances of the Advanced Gravitational
waves interferometric detectors, where the thermal noise of the test masses is
expected to be a limiting factor for their sensitivity.
We provide a quantitative analysis of the impact of non-Gaussian beams on
different kinds of thermal noises. We developed the theory of mesa beam, in
view of a future implementation in advanced GW interferometers of the mesa beam
idea, focusing on the analytical derivation of the quantities (i.e. beam width,
divergence, propagation factor), which are chosen as ISO standard reference
parameters for the characterization of an optical beam. We also analytically
proved a new duality relation between optical cavities with non-spherical
mirrors. The interest of the GW community in this new beam technology led us to
the construction and testing of a prototype mesa beam Fabry-Perot cavity with
Mexican-hat mirror. Part of the work of this thesis was devoted to the
development of new simulation programs of optical systems. These programs
provided the theoretical expected behaviour of our experiment, in particular
cavity modes structure and misalignments sensitivity to be confronted with the
experimental results. We also explored another complementary way of reducing
the mirror thermal noise, beside the beam shaping, that is the multi-layered
coating thickness optimization. We show it to be effective in reducing the
coating noise and explore the possible implications for GW interferometers in
terms of sensitivity. During this analysis we developed an independent model
for the coating effective elastic parameters, which is based on the well
understood subject of homogenization theory.
| [
{
"created": "Wed, 18 Jun 2008 18:33:07 GMT",
"version": "v1"
}
] | 2009-12-05 | [
[
"Agresti",
"Juri",
""
]
] | This thesis presents a collection of different researches on non-standard optics in view of enhancing the performances of the Advanced Gravitational waves interferometric detectors, where the thermal noise of the test masses is expected to be a limiting factor for their sensitivity. We provide a quantitative analysis of the impact of non-Gaussian beams on different kinds of thermal noises. We developed the theory of mesa beam, in view of a future implementation in advanced GW interferometers of the mesa beam idea, focusing on the analytical derivation of the quantities (i.e. beam width, divergence, propagation factor), which are chosen as ISO standard reference parameters for the characterization of an optical beam. We also analytically proved a new duality relation between optical cavities with non-spherical mirrors. The interest of the GW community in this new beam technology led us to the construction and testing of a prototype mesa beam Fabry-Perot cavity with Mexican-hat mirror. Part of the work of this thesis was devoted to the development of new simulation programs of optical systems. These programs provided the theoretical expected behaviour of our experiment, in particular cavity modes structure and misalignments sensitivity to be confronted with the experimental results. We also explored another complementary way of reducing the mirror thermal noise, beside the beam shaping, that is the multi-layered coating thickness optimization. We show it to be effective in reducing the coating noise and explore the possible implications for GW interferometers in terms of sensitivity. During this analysis we developed an independent model for the coating effective elastic parameters, which is based on the well understood subject of homogenization theory. |
2404.15164 | Eneko Aranguren | Eneko Aranguren and Ra\"ul Vera | Review on the matching conditions for the tidal problem: towards the
application to more general contexts | null | Gen Relativ Gravit 56, 50 (2024) | 10.1007/s10714-024-03237-5 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The tidal problem is used to obtain the tidal deformability (or Love number)
of stars. The semi-analytical study is usually treated in perturbation theory
as a first order perturbation problem over a spherically symmetric background
configuration consisting of a stellar interior region matched across a boundary
to a vacuum exterior region that models the tidal field. The field equations
for the metric and matter perturbations at the interior and exterior regions
are complemented with corresponding boundary conditions. The data of the two
problems at the common boundary are related by the so called matching
conditions. These conditions for the tidal problem are known in the contexts of
perfect fluid stars and superfluid stars modelled by a two-fluid. Here we
review the obtaining of the matching conditions for the tidal problem starting
from a purely geometrical setting, and present them so that they can be readily
applied to more general contexts, such as other types of matter fields,
different multiple layers or phase transitions. As a guide on how to use the
matching conditions, we recover the known results for perfect fluid and
superfluid neutron stars.
| [
{
"created": "Tue, 23 Apr 2024 16:02:42 GMT",
"version": "v1"
}
] | 2024-04-24 | [
[
"Aranguren",
"Eneko",
""
],
[
"Vera",
"Raül",
""
]
] | The tidal problem is used to obtain the tidal deformability (or Love number) of stars. The semi-analytical study is usually treated in perturbation theory as a first order perturbation problem over a spherically symmetric background configuration consisting of a stellar interior region matched across a boundary to a vacuum exterior region that models the tidal field. The field equations for the metric and matter perturbations at the interior and exterior regions are complemented with corresponding boundary conditions. The data of the two problems at the common boundary are related by the so called matching conditions. These conditions for the tidal problem are known in the contexts of perfect fluid stars and superfluid stars modelled by a two-fluid. Here we review the obtaining of the matching conditions for the tidal problem starting from a purely geometrical setting, and present them so that they can be readily applied to more general contexts, such as other types of matter fields, different multiple layers or phase transitions. As a guide on how to use the matching conditions, we recover the known results for perfect fluid and superfluid neutron stars. |
0902.4753 | Muhammad Sharif | M. Sharif and Javaria Zanub | Parallel and Orthogonal Cylindrically Symmetric Self-Similar Solutions | 15 pages, accepted for publication in J. Korean Physical Society | J. Korean Physical Society 54(2009)1373-1379 | 10.3938/jkps.54.1373 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we evaluate kinematic self-similar perfect fluid and dust
solutions for the most general cylindrically symmetric spacetime. We explore
kinematic self-similar solutions of the first, second, zeroth and infinite
kinds for parallel and orthogonal cases. It is found that the parallel case
gives solutions for both perfect fluid and dust cases in all kinds except the
zeroth kind of the dust case where there exists no solution. The orthogonal
perfect fluid case gives stiff fluid solution only in the first kind and vacuum
solution for the dust case. We obtain a total of thirteen solutions out of
which eleven are independent. The correspondence of these solutions with those
already available in the literature is also given.
| [
{
"created": "Fri, 27 Feb 2009 03:11:43 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Sharif",
"M.",
""
],
[
"Zanub",
"Javaria",
""
]
] | In this paper, we evaluate kinematic self-similar perfect fluid and dust solutions for the most general cylindrically symmetric spacetime. We explore kinematic self-similar solutions of the first, second, zeroth and infinite kinds for parallel and orthogonal cases. It is found that the parallel case gives solutions for both perfect fluid and dust cases in all kinds except the zeroth kind of the dust case where there exists no solution. The orthogonal perfect fluid case gives stiff fluid solution only in the first kind and vacuum solution for the dust case. We obtain a total of thirteen solutions out of which eleven are independent. The correspondence of these solutions with those already available in the literature is also given. |
2311.15295 | Changkai Chen | Changkai Chen, Jiliang Jing | Gravitational wave fluxes on generic orbits in near-extreme Kerr
spacetime: higher spin and large eccentricity | 14 pages. Update: corrected errors in Eqs. (32-33) | Sci. China-Phys. Mech. Astron. 67, 110411 (2024) | 10.1007/s11433-024-2431-0 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | To obtain the waveform template of gravitational waves (GWs), substantial
computational resources and exceedingly high precision are often required. In
the previous study [JCAP 11 (2023) 070], we efficiently and accurately
calculate GW fluxes of a particle in circular orbits around a Schwarzschild
black hole using the confluent Heun function. We extend the previous method to
calculate the asymptotic GW fluxes from a particle in generic orbits around a
near-extreme Kerr black hole. Especially when dealing with the computational
difficulties in large eccentricity $e=0.9$, higher spin $a=0.999$, higher
harmonic modes, and strong-field regions, our results are much better than the
results of the numerical integration method based on the Mano-Suzuki-Takasugi
method.
| [
{
"created": "Sun, 26 Nov 2023 13:30:18 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Apr 2024 07:55:57 GMT",
"version": "v2"
},
{
"created": "Sat, 8 Jun 2024 15:58:47 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Jun 2024 10:19:36 GMT",
"version": "v4"
},
{
"cr... | 2024-07-25 | [
[
"Chen",
"Changkai",
""
],
[
"Jing",
"Jiliang",
""
]
] | To obtain the waveform template of gravitational waves (GWs), substantial computational resources and exceedingly high precision are often required. In the previous study [JCAP 11 (2023) 070], we efficiently and accurately calculate GW fluxes of a particle in circular orbits around a Schwarzschild black hole using the confluent Heun function. We extend the previous method to calculate the asymptotic GW fluxes from a particle in generic orbits around a near-extreme Kerr black hole. Especially when dealing with the computational difficulties in large eccentricity $e=0.9$, higher spin $a=0.999$, higher harmonic modes, and strong-field regions, our results are much better than the results of the numerical integration method based on the Mano-Suzuki-Takasugi method. |
1604.01012 | Muhammad Sharif | M. Sharif and Saadia Mumtaz | Stability of Thin-Shell Wormholes from Regular ABG Black Hole | 26 pages, 13 figures, submitted for publication | Eur. Phys. J. Plus 132(2017)26 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we construct thin-shell wormholes from regular Ayon-Beato and
Garcia black hole by employing cut and paste formalism and examine their
stability. We analyze attractive and repulsive characteristics of wormholes
corresponding to outward and inward-directed acceleration components,
respectively. A general equation of state is assumed as a linear perturbation
to explore stability of these constructed wormholes with and without
cosmological constant. We consider linear, logarithmic and Chaplygin gas models
for exotic matter and evaluate stability regions for different values of
charge. For horizon-free case, it is found that the generalized Chaplygin gas
model provides maximum stable regions in de Sitter background while the
modified generalized Chaplygin gas and logarithmic gas yield maximum stable
regions in anti-de Sitter spacetime.
| [
{
"created": "Sat, 2 Apr 2016 05:24:46 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Mar 2017 06:10:48 GMT",
"version": "v2"
}
] | 2017-03-08 | [
[
"Sharif",
"M.",
""
],
[
"Mumtaz",
"Saadia",
""
]
] | In this paper, we construct thin-shell wormholes from regular Ayon-Beato and Garcia black hole by employing cut and paste formalism and examine their stability. We analyze attractive and repulsive characteristics of wormholes corresponding to outward and inward-directed acceleration components, respectively. A general equation of state is assumed as a linear perturbation to explore stability of these constructed wormholes with and without cosmological constant. We consider linear, logarithmic and Chaplygin gas models for exotic matter and evaluate stability regions for different values of charge. For horizon-free case, it is found that the generalized Chaplygin gas model provides maximum stable regions in de Sitter background while the modified generalized Chaplygin gas and logarithmic gas yield maximum stable regions in anti-de Sitter spacetime. |
1903.11622 | Francesco Zappa | Francesco Zappa, Sebastiano Bernuzzi, Francesco Pannarale, Michela
Mapelli, Nicola Giacobbo | Black-hole remnants from black-hole--neutron-star mergers | null | Phys. Rev. Lett. 123, 041102 (2019) | 10.1103/PhysRevLett.123.041102 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observations of gravitational waves and their electromagnetic counterparts
may soon uncover the existence of coalescing compact binary systems formed by a
stellar-mass black hole and a neutron star. These mergers result in a remnant
black hole, possibly surrounded by an accretion disk. The mass and spin of the
remnant black hole depend on the properties of the coalescing binary. We
construct a map from the binary components to the remnant black hole using a
sample of numerical-relativity simulations of different mass ratios $q$,
(anti-)aligned dimensionless spins of the black hole $a_{\rm BH}$, and several
neutron star equations of state. Given the binary total mass, the mass and spin
of the remnant black hole can therefore be determined from the three parameters
$(q,a_{\rm BH},\Lambda)$, where $\Lambda$ is the tidal deformability of the
neutron star. Our models also incorporate the binary black hole and test-mass
limit cases and we discuss a simple extension for generic black hole spins. We
combine the remnant characterization with recent population synthesis
simulations for various metallicities of the progenitor stars that generated
the binary system. We predict that black-hole-neutron-star mergers produce a
population of remnant black holes with masses distributed around $7M_\odot$ and
$9M_\odot$. For isotropic spin distributions, nonmassive accretion disks are
favoured: no bright electromagnetic counterparts are expected in such mergers.
| [
{
"created": "Wed, 27 Mar 2019 18:02:25 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Jan 2020 15:01:08 GMT",
"version": "v2"
}
] | 2020-01-31 | [
[
"Zappa",
"Francesco",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Pannarale",
"Francesco",
""
],
[
"Mapelli",
"Michela",
""
],
[
"Giacobbo",
"Nicola",
""
]
] | Observations of gravitational waves and their electromagnetic counterparts may soon uncover the existence of coalescing compact binary systems formed by a stellar-mass black hole and a neutron star. These mergers result in a remnant black hole, possibly surrounded by an accretion disk. The mass and spin of the remnant black hole depend on the properties of the coalescing binary. We construct a map from the binary components to the remnant black hole using a sample of numerical-relativity simulations of different mass ratios $q$, (anti-)aligned dimensionless spins of the black hole $a_{\rm BH}$, and several neutron star equations of state. Given the binary total mass, the mass and spin of the remnant black hole can therefore be determined from the three parameters $(q,a_{\rm BH},\Lambda)$, where $\Lambda$ is the tidal deformability of the neutron star. Our models also incorporate the binary black hole and test-mass limit cases and we discuss a simple extension for generic black hole spins. We combine the remnant characterization with recent population synthesis simulations for various metallicities of the progenitor stars that generated the binary system. We predict that black-hole-neutron-star mergers produce a population of remnant black holes with masses distributed around $7M_\odot$ and $9M_\odot$. For isotropic spin distributions, nonmassive accretion disks are favoured: no bright electromagnetic counterparts are expected in such mergers. |
2109.08645 | Gabriele Barca | Gabriele Barca, Eleonora Giovannetti, Giovanni Montani | An Overview on the Nature of the Bounce in LQC and PQM | Review article. Appears in special issue "Quantum Cosmology" of the
journal "Universe". 51 pages, 19 figures. See the article for full abstract | Universe 2021, 7, 327 | 10.3390/universe7090327 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a review on basic aspects of quantum cosmology in the presence of
cut-off physics. We first analyze how the Wheeler-DeWitt equation in a pure
metric approach describes the quantum Universe, showing how the singularity is
not removed. We then discuss basic features of loop quantum cosmology. For the
isotropic Universe, we compare the original $\mu_0$ scheme and the most
commonly accepted formulation, the $\bar{\mu}$ scheme. Some results concerning
the Bianchi Universes are also discussed. Finally, we consider some relevant
criticisms on the real link between full loop quantum gravity and its
minisuperspace implementation. In the second part of the review we consider the
isotropic Universe and the Bianchi models in the framework of polymer quantum
mechanics. We first address the polymerization in terms of the
Ashtekar-Barbero-Immirzi connection and show how the resulting dynamics is
isomorphic to the $\mu_0$. Then we analyze the polymerization of volume-like
variables, and we see the resulting dynamics is isomorphic to the $\bar{\mu}$
scheme with a fixed critical energy density. Finally, we consider the polymer
quantum dynamics of the homogeneous and inhomogeneous Mixmaster model through a
metric approach. We compare the results obtained by using the volume variable
to the standard Misner variable. In the latter case we find a cosmology that is
still singular, and its chaotic properties depend on the ratio between the
lattice steps for the isotropic and anisotropic variables. We conclude the
review with some considerations on changing variables in the polymer
representation. In particular we consider how the dynamics can be mapped in two
different sets of variables (at the price of using a coordinate-dependent
lattice step), and we infer some possible implications on the equivalence of
the $\mu_0$ and $\bar{\mu}$ scheme of loop quantum cosmology.
| [
{
"created": "Fri, 17 Sep 2021 16:58:37 GMT",
"version": "v1"
}
] | 2021-09-20 | [
[
"Barca",
"Gabriele",
""
],
[
"Giovannetti",
"Eleonora",
""
],
[
"Montani",
"Giovanni",
""
]
] | We present a review on basic aspects of quantum cosmology in the presence of cut-off physics. We first analyze how the Wheeler-DeWitt equation in a pure metric approach describes the quantum Universe, showing how the singularity is not removed. We then discuss basic features of loop quantum cosmology. For the isotropic Universe, we compare the original $\mu_0$ scheme and the most commonly accepted formulation, the $\bar{\mu}$ scheme. Some results concerning the Bianchi Universes are also discussed. Finally, we consider some relevant criticisms on the real link between full loop quantum gravity and its minisuperspace implementation. In the second part of the review we consider the isotropic Universe and the Bianchi models in the framework of polymer quantum mechanics. We first address the polymerization in terms of the Ashtekar-Barbero-Immirzi connection and show how the resulting dynamics is isomorphic to the $\mu_0$. Then we analyze the polymerization of volume-like variables, and we see the resulting dynamics is isomorphic to the $\bar{\mu}$ scheme with a fixed critical energy density. Finally, we consider the polymer quantum dynamics of the homogeneous and inhomogeneous Mixmaster model through a metric approach. We compare the results obtained by using the volume variable to the standard Misner variable. In the latter case we find a cosmology that is still singular, and its chaotic properties depend on the ratio between the lattice steps for the isotropic and anisotropic variables. We conclude the review with some considerations on changing variables in the polymer representation. In particular we consider how the dynamics can be mapped in two different sets of variables (at the price of using a coordinate-dependent lattice step), and we infer some possible implications on the equivalence of the $\mu_0$ and $\bar{\mu}$ scheme of loop quantum cosmology. |
2310.15183 | Frank Imbens | Frank Imbens | Graphical Processing of Geodesic Propagation in Python | 32 pages, 99 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Black holes and other compact objects are powerful tools to observationally
test Einsteins theory of General Relativity. We develop raytracing code to
create visual images of compact objects that are solutions of Einsteins field
equations. These include Kerr black holes and Manko-Novikov spacetimes with
extra independent multipole moments. Using parallel processing on a graphical
processing unit we can trace the millions of geodesics required to create such
images of compact objects. The loss of symmetry in Manko-Novikov spacetime
leads to strange features such as chaotic regions in the dynamics. We also
analyse other properties of geodesics, such as their exit times from the strong
field nearby the object, their redshift, or behaviour near capture regions. We
also add objects such as accretion disks to our spacetime, and determine how
they are lensed by the object. The main draw of this code is it's efficiency
and simplicity, as it allows for creating these images even on older hardware,
while still allowing any time independent metric to be studied. The code is
publicly available on github.
| [
{
"created": "Fri, 20 Oct 2023 13:03:30 GMT",
"version": "v1"
}
] | 2023-10-25 | [
[
"Imbens",
"Frank",
""
]
] | Black holes and other compact objects are powerful tools to observationally test Einsteins theory of General Relativity. We develop raytracing code to create visual images of compact objects that are solutions of Einsteins field equations. These include Kerr black holes and Manko-Novikov spacetimes with extra independent multipole moments. Using parallel processing on a graphical processing unit we can trace the millions of geodesics required to create such images of compact objects. The loss of symmetry in Manko-Novikov spacetime leads to strange features such as chaotic regions in the dynamics. We also analyse other properties of geodesics, such as their exit times from the strong field nearby the object, their redshift, or behaviour near capture regions. We also add objects such as accretion disks to our spacetime, and determine how they are lensed by the object. The main draw of this code is it's efficiency and simplicity, as it allows for creating these images even on older hardware, while still allowing any time independent metric to be studied. The code is publicly available on github. |
1502.06987 | Casey Handmer | Casey J. Handmer and B\'ela Szil\'agyi and Jeffrey Winicour | Gauge Invariant Spectral Cauchy Characteristic Extraction | null | null | 10.1088/0264-9381/32/23/235018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present gauge invariant spectral Cauchy characteristic extraction. We
compare gravitational waveforms extracted from a head-on black hole merger
simulated in two different gauges by two different codes. We show rapid
convergence, demonstrating both gauge invariance of the extraction algorithm
and consistency between the legacy Pitt null code and the much faster Spectral
Einstein Code (SpEC).
| [
{
"created": "Tue, 24 Feb 2015 22:04:02 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Aug 2015 23:34:42 GMT",
"version": "v2"
}
] | 2015-12-09 | [
[
"Handmer",
"Casey J.",
""
],
[
"Szilágyi",
"Béla",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We present gauge invariant spectral Cauchy characteristic extraction. We compare gravitational waveforms extracted from a head-on black hole merger simulated in two different gauges by two different codes. We show rapid convergence, demonstrating both gauge invariance of the extraction algorithm and consistency between the legacy Pitt null code and the much faster Spectral Einstein Code (SpEC). |
1704.04114 | Jos\'e Tom\'as G\'alvez Ghersi | Andrei V. Frolov, Jos\'e T. G\'alvez Ghersi and Alex Zucca | Unscreening scalarons with a black hole | REVTeX 4.1; 18 pages, 24 figures. Minor corrections and references
added | Phys. Rev. D. 95, 104041 (2017) | 10.1103/PhysRevD.95.104041 | SCG-2017-04 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is typically believed that the additional degrees of freedom in any
modification of gravity are completely suppressed by the large energy densities
coexisting with an astrophysical black hole. In this paper, we find that this
might not always be the case. This belief holds for black holes formed via
gravitational collapse in very dense environments, whereas the black holes with
sufficiently low accretion rates that have low matter densities inside
innermost stable circular orbit will generally unscreen chameleons. We develop
a novel technique to study the dynamics of accretion of a scalar field onto a
Schwarzschild-like black hole which is accurate on both short and long time
scales. In particular, we study the behavior of the extra scalar degree of
freedom in the Starobinsky and Hu-Sawicki $f(R)$ theories, for the symmetron
model, and for the Ratra-Peebles model. Aside from calculating non-trivial
static field profiles outside the black hole, we provide the tools to study the
(in)stability and evolution towards the equilibrium solution for any generic
well behaved set of parameters and initial conditions. Our code is made
publicly available for further research and modifications to study other
models.
| [
{
"created": "Tue, 11 Apr 2017 20:19:18 GMT",
"version": "v1"
},
{
"created": "Sat, 6 May 2017 08:40:00 GMT",
"version": "v2"
},
{
"created": "Tue, 30 May 2017 16:55:34 GMT",
"version": "v3"
}
] | 2017-05-31 | [
[
"Frolov",
"Andrei V.",
""
],
[
"Ghersi",
"José T. Gálvez",
""
],
[
"Zucca",
"Alex",
""
]
] | It is typically believed that the additional degrees of freedom in any modification of gravity are completely suppressed by the large energy densities coexisting with an astrophysical black hole. In this paper, we find that this might not always be the case. This belief holds for black holes formed via gravitational collapse in very dense environments, whereas the black holes with sufficiently low accretion rates that have low matter densities inside innermost stable circular orbit will generally unscreen chameleons. We develop a novel technique to study the dynamics of accretion of a scalar field onto a Schwarzschild-like black hole which is accurate on both short and long time scales. In particular, we study the behavior of the extra scalar degree of freedom in the Starobinsky and Hu-Sawicki $f(R)$ theories, for the symmetron model, and for the Ratra-Peebles model. Aside from calculating non-trivial static field profiles outside the black hole, we provide the tools to study the (in)stability and evolution towards the equilibrium solution for any generic well behaved set of parameters and initial conditions. Our code is made publicly available for further research and modifications to study other models. |
1601.07516 | Farhad Darabi | K. Atazadeh, F. Darabi, M. Mousavi | Dark matter as the Bose-Einstein condensation in loop quantum cosmology | 16 pages, 2 figures, minor revision | Eur. Phys. J. C, 76 (2016) 327 | 10.1140/epjc/s10052-016-4182-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the FLRW universe in a loop quantum cosmological model filled
with the radiation, baryonic matter (with negligible pressure), dark energy and
dark matter. The dark matter sector is supposed to be of Bose-Einstein
condensate type. The Bose-Einstein condensation process in a cosmological
context by supposing it as an approximate first order phase transition, has
been already studied in the literature. Here, we study the evolution of the
physical quantities related to the early universe description such as the
energy density, temperature and scale factor of the universe, before, during
and after the condensation process. We also consider in detail the evolution
era of the universe in a mixed normal-condensate dark matter phase. The
behavior and time evolution of the condensate dark matter fraction is also
analyzed.
| [
{
"created": "Wed, 27 Jan 2016 19:35:28 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2016 23:04:12 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Jun 2016 14:19:45 GMT",
"version": "v3"
}
] | 2016-09-07 | [
[
"Atazadeh",
"K.",
""
],
[
"Darabi",
"F.",
""
],
[
"Mousavi",
"M.",
""
]
] | We consider the FLRW universe in a loop quantum cosmological model filled with the radiation, baryonic matter (with negligible pressure), dark energy and dark matter. The dark matter sector is supposed to be of Bose-Einstein condensate type. The Bose-Einstein condensation process in a cosmological context by supposing it as an approximate first order phase transition, has been already studied in the literature. Here, we study the evolution of the physical quantities related to the early universe description such as the energy density, temperature and scale factor of the universe, before, during and after the condensation process. We also consider in detail the evolution era of the universe in a mixed normal-condensate dark matter phase. The behavior and time evolution of the condensate dark matter fraction is also analyzed. |
1107.5727 | Santiago Esteban Perez Bergliaffa | Santiago Esteban Perez Bergliaffa and Yves Eduardo Chifarelli de
Oliveira Nunes | Static and spherically symmetric black holes in $f(R)$ theories | null | null | 10.1103/PhysRevD.84.084006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study some features of static and spherically symmetric solutions (SSS)
with a horizon in $f(R)$ theories of gravitation by means of a near-horizon
analysis. A necessary condition for an $f(R)$ theory to have this type of
solution is obtained. General features of the effective potential are deduced,
and it is shown that there exists a limit on the curvature at the horizon, in
both cases for any $f(R$). Finally, we calculate the expression for the energy
of the collision of two masive particles in the center of mass frame.
| [
{
"created": "Thu, 28 Jul 2011 14:44:00 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Bergliaffa",
"Santiago Esteban Perez",
""
],
[
"Nunes",
"Yves Eduardo Chifarelli de Oliveira",
""
]
] | We study some features of static and spherically symmetric solutions (SSS) with a horizon in $f(R)$ theories of gravitation by means of a near-horizon analysis. A necessary condition for an $f(R)$ theory to have this type of solution is obtained. General features of the effective potential are deduced, and it is shown that there exists a limit on the curvature at the horizon, in both cases for any $f(R$). Finally, we calculate the expression for the energy of the collision of two masive particles in the center of mass frame. |
1808.09971 | Benjamin Bahr | Benjamin Bahr | Volume of 4-polytopes from bivectors | 19 pages, 13 figures | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we prove a formula for the volume of 4-dimensional polytopes,
in terms of their face bivectors, and the crossings within their boundary
graph. This proves that the volume is an invariant of bivector-coloured graphs
in $S^3$.
| [
{
"created": "Wed, 29 Aug 2018 18:00:02 GMT",
"version": "v1"
}
] | 2018-08-31 | [
[
"Bahr",
"Benjamin",
""
]
] | In this article we prove a formula for the volume of 4-dimensional polytopes, in terms of their face bivectors, and the crossings within their boundary graph. This proves that the volume is an invariant of bivector-coloured graphs in $S^3$. |
gr-qc/9904076 | Takahiro Tanaka | Yoshiaki Himemoto and Takahiro Tanaka | Generalization of the model of Hawking radiation with modified high
frequency dispersion relation | 23 pages, 5 postscript figures, submitted to Physical Review D | Phys.Rev. D61 (2000) 064004 | 10.1103/PhysRevD.61.064004 | OU-TAP 99 | gr-qc | null | The Hawking radiation is one of the most interesting phenomena predicted by
the theory of quantum field in curved space. The origin of Hawking radiation is
closely related to the fact that a particle which marginally escapes from
collapsing into a black hole is observed at the future infinity with infinitely
large redshift. In other words, such a particle had a very high frequency when
it was near the event horizon. Motivated by the possibility that the property
of Hawking radiation may be altered by some unknowned physics which may exist
beyond some critical scale, Unruh proposed a model which has higher order
spatial derivative terms. In his model, the effects of unknown physics are
modeled so as to be suppressed for the waves with a wavelength much longer than
the critical scale, $k_0^{-1}$. Surprisingly, it was shown that the thermal
spectrum is recovered for such modified models. To introduce such higher order
spatial derivative terms, the Lorentz invariance must be violated because one
special spatial direction needs to be chosen. In previous works, the rest frame
of freely-falling observers was employed as this special reference frame. Here
we give an extension by allowing a more general choice of the reference frame.
Developing the method taken by Corley, % and especially focusing on subluminal
case, we show that the resulting spectrum of created particles again becomes
the thermal one at the Hawking temperature even if the choice of the reference
frame is generalized. Using the technique of the matched asymptotic expansion,
we also show that the correction to the thermal radiation stays of order
$k_0^{-2}$ or smaller when the spectrum of radiated particle around its peak is
concerned.
| [
{
"created": "Thu, 29 Apr 1999 10:14:27 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 1999 15:21:16 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Sep 1999 06:52:45 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Himemoto",
"Yoshiaki",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | The Hawking radiation is one of the most interesting phenomena predicted by the theory of quantum field in curved space. The origin of Hawking radiation is closely related to the fact that a particle which marginally escapes from collapsing into a black hole is observed at the future infinity with infinitely large redshift. In other words, such a particle had a very high frequency when it was near the event horizon. Motivated by the possibility that the property of Hawking radiation may be altered by some unknowned physics which may exist beyond some critical scale, Unruh proposed a model which has higher order spatial derivative terms. In his model, the effects of unknown physics are modeled so as to be suppressed for the waves with a wavelength much longer than the critical scale, $k_0^{-1}$. Surprisingly, it was shown that the thermal spectrum is recovered for such modified models. To introduce such higher order spatial derivative terms, the Lorentz invariance must be violated because one special spatial direction needs to be chosen. In previous works, the rest frame of freely-falling observers was employed as this special reference frame. Here we give an extension by allowing a more general choice of the reference frame. Developing the method taken by Corley, % and especially focusing on subluminal case, we show that the resulting spectrum of created particles again becomes the thermal one at the Hawking temperature even if the choice of the reference frame is generalized. Using the technique of the matched asymptotic expansion, we also show that the correction to the thermal radiation stays of order $k_0^{-2}$ or smaller when the spectrum of radiated particle around its peak is concerned. |
1905.00446 | Qingwen Wang | Qingwen Wang, Naritaka Oshita, Niayesh Afshordi | Echoes from Quantum Black Holes | 9 pages, 8 figures, comments are welcome | Phys. Rev. D 101, 024031 (2020) | 10.1103/PhysRevD.101.024031 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most triumphant predictions of the theory if general relativity
was the recent LIGO-Virgo detection of gravitational wave (GW) signals produced
in binary black hole (BH) mergers. However, it is suggested that exotic compact
objects, proposed in quantum gravity models of BHs, may produce similar
classical GW waveforms, followed by delayed repeating "echoes". In a companion
paper [1], we have presented different arguments for a universal Boltzmann
reflectivity of quantum BH horizons. Here, we investigate the resulting echoes
from this prescription. We derive corresponding quasi-normal modes (QNMs) for
quantum BHs analytically, and show how their initial conditions can be related
to the QNMs of classical BHs. Ergoregion instability is suppressed by the
imperfect reflectivity. We then compare the analytic and numerical predictions
for echoes in real time, verifying their consistency. In particular, we find
that the amplitudes of the first ~20 echoes decay inversely with time, while
the subsequent echoes decay exponentially. Finally, we present predictions for
the signal-to-noise ratio of echoes for spinning BHs, which should be
imminently detectable for massive remnants, subject to the uncertainty in the
nonlinear initial conditions of the BH merger.
| [
{
"created": "Wed, 1 May 2019 18:44:14 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2019 18:29:06 GMT",
"version": "v2"
}
] | 2020-01-15 | [
[
"Wang",
"Qingwen",
""
],
[
"Oshita",
"Naritaka",
""
],
[
"Afshordi",
"Niayesh",
""
]
] | One of the most triumphant predictions of the theory if general relativity was the recent LIGO-Virgo detection of gravitational wave (GW) signals produced in binary black hole (BH) mergers. However, it is suggested that exotic compact objects, proposed in quantum gravity models of BHs, may produce similar classical GW waveforms, followed by delayed repeating "echoes". In a companion paper [1], we have presented different arguments for a universal Boltzmann reflectivity of quantum BH horizons. Here, we investigate the resulting echoes from this prescription. We derive corresponding quasi-normal modes (QNMs) for quantum BHs analytically, and show how their initial conditions can be related to the QNMs of classical BHs. Ergoregion instability is suppressed by the imperfect reflectivity. We then compare the analytic and numerical predictions for echoes in real time, verifying their consistency. In particular, we find that the amplitudes of the first ~20 echoes decay inversely with time, while the subsequent echoes decay exponentially. Finally, we present predictions for the signal-to-noise ratio of echoes for spinning BHs, which should be imminently detectable for massive remnants, subject to the uncertainty in the nonlinear initial conditions of the BH merger. |
2407.14035 | Chen-Kai Qiao | Chen-Kai Qiao | The Existence and Distribution of Photon Spheres Near Spherically
Symmetric Black Holes -- A Geometric Analysis | 18+2 pages, 10+1 figures, 4 Appendices V2: some references added | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Photon sphere has attracted significant attention since the discovery of
black hole shadow images by Event Horizon Telescope. Recently, a number of
studies have highlighted that the number of photon spheres and their
distributions near black holes are strongly constrained by black hole
properties. Specifically, for black holes with event horizons and proper
asymptotic behaviors, the number of stable and unstable photon spheres
satisfies the relation $n_{\text{stable}} - n_{\text{unstable}} = -1$. In this
study, we provide a novel proof on this relation using a completely new
geometric approach, in which the stable and unstable photon spheres are
determined by Gaussian curvature and geodesic curvature in the optical geometry
of black hole spacetimes. Firstly, we demonstrated the existence of photon
spheres near black holes with proper asymptotic behaviors (asymptotically flat
black holes, asymptotically de-Sitter and anti-de-Sitter black holes).
Subsequently, we proved that the stable and unstable photon spheres near black
holes must be one-to-one alternatively separated from each other, such that
each unstable photon sphere is sandwiched between two stable photon spheres
(and each stable photon sphere is sandwiched between two unstable photon
spheres). Our analysis in this study is limited to the spherically symmetric
black hole spacetime (with the spacetime metric
$ds^{2}=g_{tt}dt^{2}+g_{rr}dr^{2}+g_{\theta\theta}d\theta^{2}+g_{\phi\phi}d\phi^{2}$).
| [
{
"created": "Fri, 19 Jul 2024 05:19:04 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 2024 17:45:51 GMT",
"version": "v2"
}
] | 2024-08-02 | [
[
"Qiao",
"Chen-Kai",
""
]
] | Photon sphere has attracted significant attention since the discovery of black hole shadow images by Event Horizon Telescope. Recently, a number of studies have highlighted that the number of photon spheres and their distributions near black holes are strongly constrained by black hole properties. Specifically, for black holes with event horizons and proper asymptotic behaviors, the number of stable and unstable photon spheres satisfies the relation $n_{\text{stable}} - n_{\text{unstable}} = -1$. In this study, we provide a novel proof on this relation using a completely new geometric approach, in which the stable and unstable photon spheres are determined by Gaussian curvature and geodesic curvature in the optical geometry of black hole spacetimes. Firstly, we demonstrated the existence of photon spheres near black holes with proper asymptotic behaviors (asymptotically flat black holes, asymptotically de-Sitter and anti-de-Sitter black holes). Subsequently, we proved that the stable and unstable photon spheres near black holes must be one-to-one alternatively separated from each other, such that each unstable photon sphere is sandwiched between two stable photon spheres (and each stable photon sphere is sandwiched between two unstable photon spheres). Our analysis in this study is limited to the spherically symmetric black hole spacetime (with the spacetime metric $ds^{2}=g_{tt}dt^{2}+g_{rr}dr^{2}+g_{\theta\theta}d\theta^{2}+g_{\phi\phi}d\phi^{2}$). |
1706.08848 | Hongsheng Zhang | Hongsheng Zhang, Yi Zhang, Xin-Zhou Li | Dynamical spacetimes in conformal gravity | 13 pages, no fig | Nuclear Physics B, Volume 921, August 2017, Pages 522-537 | 10.1016/j.nuclphysb.2017.05.011 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | The conformal gravity remarkably boosts our prehension of gravity theories.
We find a series of dynamical solutions in the $W^2$-conformal gravity,
including generalized Schwarzschild-Friedmann-Robertson-Walker (GSFRW), charged
generalized Schwarzschild-Friedmann-Robertson-Walker (CGSFRW), especially
rotating Friedmann-Robertson-Walker (RFRW), charged rotating
Friedmann-Robertson-Walker (CRFRW), and a dynamical cylindrically symmetric
solutions. The RFRW, CRFRW and the dynamical cylindrically symmetric solutions
are never found in the Einstein gravity and modified gravities. The GSFRW and
CGSFRW solutions take different forms from the corresponding solutions in the
Einstein gravity.
| [
{
"created": "Mon, 26 Jun 2017 02:49:25 GMT",
"version": "v1"
}
] | 2017-06-28 | [
[
"Zhang",
"Hongsheng",
""
],
[
"Zhang",
"Yi",
""
],
[
"Li",
"Xin-Zhou",
""
]
] | The conformal gravity remarkably boosts our prehension of gravity theories. We find a series of dynamical solutions in the $W^2$-conformal gravity, including generalized Schwarzschild-Friedmann-Robertson-Walker (GSFRW), charged generalized Schwarzschild-Friedmann-Robertson-Walker (CGSFRW), especially rotating Friedmann-Robertson-Walker (RFRW), charged rotating Friedmann-Robertson-Walker (CRFRW), and a dynamical cylindrically symmetric solutions. The RFRW, CRFRW and the dynamical cylindrically symmetric solutions are never found in the Einstein gravity and modified gravities. The GSFRW and CGSFRW solutions take different forms from the corresponding solutions in the Einstein gravity. |
1306.0820 | Julio Cesar Fabris | N. Pinto-Neto, J.C. Fabris | Quantum cosmology from the de Broglie-Bohm perspective | Latex file, 75 pages, 3 figures in eps format. To appear in CQG as an
invited Topical Review | null | 10.1088/0264-9381/30/14/143001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the main results that have been obtained in quantum cosmology from
the perspective of the de Broglie-Bohm quantum theory. As it is a dynamical
theory of assumed objectively real trajectories in the configuration space of
the physical system under investigation, this quantum theory is not essentially
probabilistic and dispenses the collapse postulate, turning it suitable to be
applied to cosmology. In the framework of minisuperspace models, we show how
quantum cosmological effects in the de-Broglie-Bohm's approach can avoid the
initial singularity, and isotropize the Universe. We then extend minisuperspace
in order to include linear cosmological perturbations. We present the main
equations which govern the dynamics of quantum cosmological perturbations
evolving in non-singular quantum cosmological backgrounds, and calculate some
of their observational consequences. These results are not known how to be
obtained in other approaches to quantum theory. In the general case of full
superspace, we enumerate the possible structures of quantum space and time that
emerge from the de Broglie-Bohm picture. Finally, we compare some of the
results coming from the de Broglie-Bohm theory with other approaches, and
discuss the physical reasons for some discrepancies that occur.
| [
{
"created": "Tue, 4 Jun 2013 14:52:44 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Pinto-Neto",
"N.",
""
],
[
"Fabris",
"J. C.",
""
]
] | We review the main results that have been obtained in quantum cosmology from the perspective of the de Broglie-Bohm quantum theory. As it is a dynamical theory of assumed objectively real trajectories in the configuration space of the physical system under investigation, this quantum theory is not essentially probabilistic and dispenses the collapse postulate, turning it suitable to be applied to cosmology. In the framework of minisuperspace models, we show how quantum cosmological effects in the de-Broglie-Bohm's approach can avoid the initial singularity, and isotropize the Universe. We then extend minisuperspace in order to include linear cosmological perturbations. We present the main equations which govern the dynamics of quantum cosmological perturbations evolving in non-singular quantum cosmological backgrounds, and calculate some of their observational consequences. These results are not known how to be obtained in other approaches to quantum theory. In the general case of full superspace, we enumerate the possible structures of quantum space and time that emerge from the de Broglie-Bohm picture. Finally, we compare some of the results coming from the de Broglie-Bohm theory with other approaches, and discuss the physical reasons for some discrepancies that occur. |
1805.01405 | Klaus Kroencke | David Fajman, Klaus Kroencke | On the CMC-Einstein-Lambda flow | 12 pages, published version. Parts of this paper appeared in the
first version of arXiv:1504.00687 | Class. Quantum Grav. 35 (2018) no. 19, 195005 | 10.1088/1361-6382/aad843 | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We complement a recent work on the stability of fixed points of the
CMC-Einstein-$\Lambda$ flow. In particular, we modify the utilized gauge for
the Einstein equations and remove a restriction on the fixed points whose
stability we are able to prove by this method, and thereby generalize the
stability result. In addition, we consider the notion of the reduced
Hamiltonian, originally introduced by Fischer and Moncrief for the standard
CMC-Einstein flow. For the analog version of the flow in the presence of a
positive cosmological constant we identify the stationary points and relate
them to the long-time behavior of the flow on manifolds of different Yamabe
types. This entails conjectures on the asymptotic behaviour and potential
attractors.
| [
{
"created": "Thu, 3 May 2018 16:21:06 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Sep 2018 13:29:36 GMT",
"version": "v2"
}
] | 2018-09-10 | [
[
"Fajman",
"David",
""
],
[
"Kroencke",
"Klaus",
""
]
] | We complement a recent work on the stability of fixed points of the CMC-Einstein-$\Lambda$ flow. In particular, we modify the utilized gauge for the Einstein equations and remove a restriction on the fixed points whose stability we are able to prove by this method, and thereby generalize the stability result. In addition, we consider the notion of the reduced Hamiltonian, originally introduced by Fischer and Moncrief for the standard CMC-Einstein flow. For the analog version of the flow in the presence of a positive cosmological constant we identify the stationary points and relate them to the long-time behavior of the flow on manifolds of different Yamabe types. This entails conjectures on the asymptotic behaviour and potential attractors. |
0912.5015 | Brian Smtih | Brian Smith | Black hole initial data with a horizon of prescribed intrinsic and
extrinsic geometry | to appear in Contemporary Mathematics | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this work is to construct asymptotically flat, time symmetric
initial data with an apparent horizon of prescribed intrinsic and extrinsic
geometry. To do this, we use the parabolic partial differential equation for
prescribing scalar curvature. In this equation the horizon geometry is
contained within the freely specifiable part of the metric. This contrasts with
the conformal method in which the geometry of the horizon can only be specified
up to a conformal factor.
| [
{
"created": "Sat, 26 Dec 2009 12:51:28 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jun 2010 10:22:32 GMT",
"version": "v2"
}
] | 2010-06-15 | [
[
"Smith",
"Brian",
""
]
] | The purpose of this work is to construct asymptotically flat, time symmetric initial data with an apparent horizon of prescribed intrinsic and extrinsic geometry. To do this, we use the parabolic partial differential equation for prescribing scalar curvature. In this equation the horizon geometry is contained within the freely specifiable part of the metric. This contrasts with the conformal method in which the geometry of the horizon can only be specified up to a conformal factor. |
gr-qc/0210091 | A. N. Ivanov | A. N. Ivanov, A. P. Kobushkin, M. Wellenzohn | Storage rings as detectors for relic gravitational-wave background ? | 10 pages, 1 figure,All results of this manuscript have been delivered
online at ARIES WP6 Workshop: Storage Rings and Gravitational Waves
"SRGW2021", held from 2.02.2021 to 31.03.2021 and organized by CERN, Geneva
Switzerland | null | null | null | gr-qc astro-ph hep-ex hep-ph hep-th physics.acc-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that storage rings can be used for the detection of low-frequency
gravitational-wave background. We explain the systematic shrinkage of the
machine circumference of the storage ring of the SPring-8, observed by Takao
and Shimada (Proceedings of EPAC 2000, Vienna, 2000, p.1572), by the influence
of the relic gravitational-wave background. We show that the systematic
shrinkage of the machine circumference can be explained by a relic
gravitational-wave background even if it is treated as a stochastic system
incoming on the plane of the machine circumference from all quarters of the
Universe. We show that the rate of the systematic shrinkage of the machine
circumference does not depend on the radius of the storage ring and it should
be universal for storage rings with any radius.
| [
{
"created": "Sun, 27 Oct 2002 09:29:25 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Nov 2002 15:28:14 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Dec 2002 18:44:55 GMT",
"version": "v3"
},
{
"created": "Mon, 23 Jun 2003 17:52:57 GMT",
"version": "v4"
},
{
"cr... | 2021-03-31 | [
[
"Ivanov",
"A. N.",
""
],
[
"Kobushkin",
"A. P.",
""
],
[
"Wellenzohn",
"M.",
""
]
] | We argue that storage rings can be used for the detection of low-frequency gravitational-wave background. We explain the systematic shrinkage of the machine circumference of the storage ring of the SPring-8, observed by Takao and Shimada (Proceedings of EPAC 2000, Vienna, 2000, p.1572), by the influence of the relic gravitational-wave background. We show that the systematic shrinkage of the machine circumference can be explained by a relic gravitational-wave background even if it is treated as a stochastic system incoming on the plane of the machine circumference from all quarters of the Universe. We show that the rate of the systematic shrinkage of the machine circumference does not depend on the radius of the storage ring and it should be universal for storage rings with any radius. |
1509.07358 | Muhammad Sharif | M. Sharif and Rabia Saleem | Inflationary Weak Anisotropic Model with General Dissipation Coefficient | 24 pages, 12 figures. arXiv admin note: text overlap with
arXiv:1312.3502 by other authors | Astrophys. Space Sci. 361(2016)107 | 10.1007/s10509-016-2698-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper explores the dynamics of warm intermediate and logamediate
inflationary models during weak dissipative regime with a general form of
dissipative coefficient. We analyze these models within the framework of
locally rotationally symmetric Bianchi type I universe. In both cases, we
evaluate solution of inflaton, effective scalar potential, dissipative
coefficient, slow-roll parameters, scalar and tensor power spectra, scalar
spectral index and tensor to scalar ratio under slow-roll approximation. We
constrain the model parameters using recent data and conclude that anisotropic
inflationary universe model with generalized dissipation coefficient remains
compatible with WMAP9, Planck and BICEP2 data.
| [
{
"created": "Tue, 15 Sep 2015 10:14:51 GMT",
"version": "v1"
}
] | 2016-03-23 | [
[
"Sharif",
"M.",
""
],
[
"Saleem",
"Rabia",
""
]
] | This paper explores the dynamics of warm intermediate and logamediate inflationary models during weak dissipative regime with a general form of dissipative coefficient. We analyze these models within the framework of locally rotationally symmetric Bianchi type I universe. In both cases, we evaluate solution of inflaton, effective scalar potential, dissipative coefficient, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio under slow-roll approximation. We constrain the model parameters using recent data and conclude that anisotropic inflationary universe model with generalized dissipation coefficient remains compatible with WMAP9, Planck and BICEP2 data. |
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