id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1602.02561 | Rainer Collier | Rainer Collier | Dirac Equation and Planck-Scale Quantities | 19 pages | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work investigates in which form quantities with Planck dimensions occur
already in the common quantum theory with local Lorentz symmetry. Since such
Planck quantities as Planck length or Planck mass involve the Planck constant
h, the velocity of light c and the Newton gravitational constant G, the
relativistic Dirac equation (h, c) in the Newtonian gravitational potential (G)
can be considered as a test theory. The evaluation of the break-off condition
of the power series of the radial energy eigenfunctions of a purely
gravitational atom leads to exact terms for the energy eigenvalues E for
various special cases of the quantum numbers N, k and n = N + |k|. It turns out
that a meaningful atom model, based solely on Newtonian gravitational forces,
can result if, inter alia, the test mass m in the gravitational field of the
mass M is selected to be smaller than the Planck mass.
| [
{
"created": "Mon, 8 Feb 2016 13:31:43 GMT",
"version": "v1"
}
] | 2016-02-09 | [
[
"Collier",
"Rainer",
""
]
] | This work investigates in which form quantities with Planck dimensions occur already in the common quantum theory with local Lorentz symmetry. Since such Planck quantities as Planck length or Planck mass involve the Planck constant h, the velocity of light c and the Newton gravitational constant G, the relativistic Dirac equation (h, c) in the Newtonian gravitational potential (G) can be considered as a test theory. The evaluation of the break-off condition of the power series of the radial energy eigenfunctions of a purely gravitational atom leads to exact terms for the energy eigenvalues E for various special cases of the quantum numbers N, k and n = N + |k|. It turns out that a meaningful atom model, based solely on Newtonian gravitational forces, can result if, inter alia, the test mass m in the gravitational field of the mass M is selected to be smaller than the Planck mass. |
1811.05979 | Davide Gerosa | Davide Gerosa, Alicia Lima, Emanuele Berti, Ulrich Sperhake, Michael
Kesden, Richard O'Shaughnessy | Wide nutation: binary black-hole spins repeatedly oscillating from full
alignment to full anti-alignment | Animated version of Fig. 3 available at
https://davidegerosa.com/spinprecession - Published in CQG | Class. Quantum Grav. 36, 10, 105003 (2019) | 10.1088/1361-6382/ab14ae | null | gr-qc astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of 2PN black-hole binary spin precession, we explore
configurations where one of the two spins oscillates from being completely
aligned with the orbital angular momentum to being completely anti-aligned with
it during a single precession cycle. This "wide nutation" is the extreme limit
of the generic phenomenon of spin nutation in black-hole binaries. Crucially,
wide nutation happens on the short precession time scale and it is not a
secular effect due to gravitational-wave radiation reaction. The spins of these
binaries, therefore, flip repeatedly as one of these special configurations is
entered. Binaries with total mass $M$, mass ratio $q$, and dimensionless spin
$\chi_1$ ($\chi_2$) of the more (less) massive black hole are allowed to
undergo wide nutation at binary separations $r \leq r_{\rm wide} \equiv [(q
\chi_2 - \chi_1)/(1-q)]^2 M$. Sources that are more likely to nutate widely
have similar masses and effective spins close to zero.
| [
{
"created": "Wed, 14 Nov 2018 19:00:02 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Apr 2019 15:16:28 GMT",
"version": "v2"
}
] | 2019-04-16 | [
[
"Gerosa",
"Davide",
""
],
[
"Lima",
"Alicia",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Kesden",
"Michael",
""
],
[
"O'Shaughnessy",
"Richard",
""
]
] | Within the framework of 2PN black-hole binary spin precession, we explore configurations where one of the two spins oscillates from being completely aligned with the orbital angular momentum to being completely anti-aligned with it during a single precession cycle. This "wide nutation" is the extreme limit of the generic phenomenon of spin nutation in black-hole binaries. Crucially, wide nutation happens on the short precession time scale and it is not a secular effect due to gravitational-wave radiation reaction. The spins of these binaries, therefore, flip repeatedly as one of these special configurations is entered. Binaries with total mass $M$, mass ratio $q$, and dimensionless spin $\chi_1$ ($\chi_2$) of the more (less) massive black hole are allowed to undergo wide nutation at binary separations $r \leq r_{\rm wide} \equiv [(q \chi_2 - \chi_1)/(1-q)]^2 M$. Sources that are more likely to nutate widely have similar masses and effective spins close to zero. |
2302.05861 | Qiyuan Pan | Chengjia Chen, Qiyuan Pan, Jiliang Jing | Quasinormal modes of a scalar perturbation around a rotating BTZ-like
black hole in Einstein-bumblebee gravity | 15 pages, 1 figure | Phys. Lett. B 846, 138186 (2023) | 10.1016/j.physletb.2023.138186 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We analytically study the quasinormal modes of a scalar perturbation around a
rotating BTZ-like black hole in the Einstein-bumblebee gravity. We observe that
the Lorentz symmetry breaking parameter imprints only in the imaginary parts of
the quasinormal frequencies for the right-moving and left-moving modes. The
perturbational field decays more rapidly for the negative Lorentz symmetry
breaking parameter, but more slowly for the positive one. The forms of the real
parts are the same as those in the usual BTZ black holes. Moreover, we also
discuss the $AdS/CFT$ correspondence from the quasinormal modes and find that
the Lorentz symmetry breaking parameter enhances the left and right conformal
weights $h_L$ and $h_R$ of the operators dual to the scalar field in the
boundary. These results could be helpful to understand the $AdS/CFT$
correspondence and the Einstein-bumblebee gravity with the Lorentz symmetry
violation.
| [
{
"created": "Sun, 12 Feb 2023 06:31:42 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Sep 2023 08:53:27 GMT",
"version": "v2"
}
] | 2023-09-26 | [
[
"Chen",
"Chengjia",
""
],
[
"Pan",
"Qiyuan",
""
],
[
"Jing",
"Jiliang",
""
]
] | We analytically study the quasinormal modes of a scalar perturbation around a rotating BTZ-like black hole in the Einstein-bumblebee gravity. We observe that the Lorentz symmetry breaking parameter imprints only in the imaginary parts of the quasinormal frequencies for the right-moving and left-moving modes. The perturbational field decays more rapidly for the negative Lorentz symmetry breaking parameter, but more slowly for the positive one. The forms of the real parts are the same as those in the usual BTZ black holes. Moreover, we also discuss the $AdS/CFT$ correspondence from the quasinormal modes and find that the Lorentz symmetry breaking parameter enhances the left and right conformal weights $h_L$ and $h_R$ of the operators dual to the scalar field in the boundary. These results could be helpful to understand the $AdS/CFT$ correspondence and the Einstein-bumblebee gravity with the Lorentz symmetry violation. |
gr-qc/9705008 | Melnikov-Guest | Vladimir D. Ivashchuk | Wick Rotation, Regularization of Propagators by a Complex Metric and
Multidimensional Cosmology | 9 pages, Latex. To appear in Grav. and Cosmol. v.3, No.1 (1997) | Grav.Cosmol. 3 (1997) 8-16 | null | RGS-VNIIMS-97/04 | gr-qc hep-ph hep-th | null | The Wick rotation in quantum field theory is considered in terms of
analytical continuation in the signature matrix parameter w = eta_00.
Regularization of propagators by a complex metric parameter in most cases
preserves (i) the convergence of Feynmann integrals (understood as Lebesgue
integrals) if the corresponding integrals of Euclidean theory are convergent;
(ii) the regularity of propagators in the coordinate representation if there is
regularity in the Euclidean case. The well-known covariant regularization by a
complex mass does not in general satisfy these conditions. Theories with a
large family of propagators regularized by complex metric were previously
considered by the author, and analogues of the
Bogoliubov-Parasiuk-Hepp-Zimmermann theorems were proved. [V.D.Ivashchuk, Izv.
Akad. Nauk Mold. SSR, Ser. Fiz.-Tekhn. i Math. Nauk, 3 (1987), 8; 1 (1988),
10]. This paper shows that in the case of multidimensional cosmology describing
the evolution of n spaces M_i, i = 1, ..., n, the Wick rotation in the
minisuperspace may be performed by analytical continuation in the dimensions
N_i = dim M_i or in the dimension of the time submanifold M_0.
| [
{
"created": "Tue, 6 May 1997 17:57:40 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Ivashchuk",
"Vladimir D.",
""
]
] | The Wick rotation in quantum field theory is considered in terms of analytical continuation in the signature matrix parameter w = eta_00. Regularization of propagators by a complex metric parameter in most cases preserves (i) the convergence of Feynmann integrals (understood as Lebesgue integrals) if the corresponding integrals of Euclidean theory are convergent; (ii) the regularity of propagators in the coordinate representation if there is regularity in the Euclidean case. The well-known covariant regularization by a complex mass does not in general satisfy these conditions. Theories with a large family of propagators regularized by complex metric were previously considered by the author, and analogues of the Bogoliubov-Parasiuk-Hepp-Zimmermann theorems were proved. [V.D.Ivashchuk, Izv. Akad. Nauk Mold. SSR, Ser. Fiz.-Tekhn. i Math. Nauk, 3 (1987), 8; 1 (1988), 10]. This paper shows that in the case of multidimensional cosmology describing the evolution of n spaces M_i, i = 1, ..., n, the Wick rotation in the minisuperspace may be performed by analytical continuation in the dimensions N_i = dim M_i or in the dimension of the time submanifold M_0. |
gr-qc/9612016 | Herbert Liebl | W. Kummer (Vienna, Tech. U.) | General Treatment of All 2d Covariant Models | 17 pages (latex file) | null | null | TUW-96-13 | gr-qc | null | General matterless models of gravity include dilaton gravity, arbitrary
powers in curvature, but also dynamical torsion. They are a special class of
"Poisson-sigma-models" whose solutions are known completely, together with
their general global structure. Beside the ordinary black hole, arbitrary
singularity structures can be studied. It is also possible to derive an action
"backwards", starting from a given manifold. The role of conservation laws,
Noether charge and the quantization have been investigated. Scalar and
fermionic matter fields may be included as well.
| [
{
"created": "Fri, 6 Dec 1996 12:51:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kummer",
"W.",
"",
"Vienna, Tech. U."
]
] | General matterless models of gravity include dilaton gravity, arbitrary powers in curvature, but also dynamical torsion. They are a special class of "Poisson-sigma-models" whose solutions are known completely, together with their general global structure. Beside the ordinary black hole, arbitrary singularity structures can be studied. It is also possible to derive an action "backwards", starting from a given manifold. The role of conservation laws, Noether charge and the quantization have been investigated. Scalar and fermionic matter fields may be included as well. |
1501.00571 | Thomas Adams Dr | T. Adams, J. R. Leong, J. Slutsky, M. Was, C. Affeldt, J. Degallaix,
K. L. Dooley, H. Grote, S. Hild, H. Lueck, D. M. Macleod, L. K. Nuttall, M.
Prijatelj, E. Schreiber, B. Sorazu, K. A. Strain, P. J. Sutton, H. Vahlbruch,
H. Witte, K. Danzmann | Cost-benefit analysis for commissioning decisions in GEO600 | 17 pages, 17 figures, 2 tables | null | 10.1088/0264-9381/32/13/135014 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave interferometers are complex instruments, requiring years
of commissioning to achieve the required sensitivities for the detection of
gravitational waves, of order 10^-21 in dimensionless detector strain, in the
tens of Hz to several kHz frequency band. Investigations carried out by the
GEO600 detector characterisation group have shown that detector
characterisation techniques are useful when planning for commissioning work. At
the time of writing, GEO600 is the only large scale laser interferometer
currently in operation running with a high duty factor, 70%, limited chiefly by
the time spent commissioning the detector. The number of observable
gravitational wave sources scales as the product of the volume of space to
which the detector is sensitive and the observation time, so the goal of
commissioning is to improve the detector sensitivity with the least possible
detector down time. We demonstrate a method for increasing the number of
sources observable by such a detector, by assessing the severity of
non-astrophysical noise contaminations to efficiently guide commissioning. This
method will be particularly useful in the early stages and during the initial
science runs of the aLIGO and adVirgo detectors, as they are brought up to
design performance.
| [
{
"created": "Sat, 3 Jan 2015 15:33:06 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jul 2015 11:57:13 GMT",
"version": "v2"
}
] | 2015-07-13 | [
[
"Adams",
"T.",
""
],
[
"Leong",
"J. R.",
""
],
[
"Slutsky",
"J.",
""
],
[
"Was",
"M.",
""
],
[
"Affeldt",
"C.",
""
],
[
"Degallaix",
"J.",
""
],
[
"Dooley",
"K. L.",
""
],
[
"Grote",
"H.",
""
],
[
"Hild",
"S.",
""
],
[
"Lueck",
"H.",
""
],
[
"Macleod",
"D. M.",
""
],
[
"Nuttall",
"L. K.",
""
],
[
"Prijatelj",
"M.",
""
],
[
"Schreiber",
"E.",
""
],
[
"Sorazu",
"B.",
""
],
[
"Strain",
"K. A.",
""
],
[
"Sutton",
"P. J.",
""
],
[
"Vahlbruch",
"H.",
""
],
[
"Witte",
"H.",
""
],
[
"Danzmann",
"K.",
""
]
] | Gravitational wave interferometers are complex instruments, requiring years of commissioning to achieve the required sensitivities for the detection of gravitational waves, of order 10^-21 in dimensionless detector strain, in the tens of Hz to several kHz frequency band. Investigations carried out by the GEO600 detector characterisation group have shown that detector characterisation techniques are useful when planning for commissioning work. At the time of writing, GEO600 is the only large scale laser interferometer currently in operation running with a high duty factor, 70%, limited chiefly by the time spent commissioning the detector. The number of observable gravitational wave sources scales as the product of the volume of space to which the detector is sensitive and the observation time, so the goal of commissioning is to improve the detector sensitivity with the least possible detector down time. We demonstrate a method for increasing the number of sources observable by such a detector, by assessing the severity of non-astrophysical noise contaminations to efficiently guide commissioning. This method will be particularly useful in the early stages and during the initial science runs of the aLIGO and adVirgo detectors, as they are brought up to design performance. |
gr-qc/0008048 | Pablo Rafael Mora | Pablo Mora (Universidad de la Republica, Uruguay) | A Note in Cosmology and Loop Quantum Gravity | 9 pages, Latex | null | null | null | gr-qc | null | One possible description of the very early stages of the evolution of the
universe is provided by Chaotic Inflationary Cosmology. For that model the role
of the inflaton field is played by quantum gravitational effects. We study if
such a picture may arise within the framework of Loop Quantum gravity by
studying a simple model. While we were unable to reach definitive conclusions
we believe the general approach proposed in this paper may prove fruitful in
the future.
| [
{
"created": "Mon, 21 Aug 2000 01:09:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mora",
"Pablo",
"",
"Universidad de la Republica, Uruguay"
]
] | One possible description of the very early stages of the evolution of the universe is provided by Chaotic Inflationary Cosmology. For that model the role of the inflaton field is played by quantum gravitational effects. We study if such a picture may arise within the framework of Loop Quantum gravity by studying a simple model. While we were unable to reach definitive conclusions we believe the general approach proposed in this paper may prove fruitful in the future. |
2305.10933 | Mian Zhu | Yong Cai, Mian Zhu and Yun-Song Piao | Primordial black holes from null energy condition violation during
inflation | 9 pages, 5 figures + supplemental material, published in PRL | Physical Review Letters 133, 021001 (2024) | 10.1103/PhysRevLett.133.021001 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Primordial black holes (PBHs) and the violation of the null energy condition
(NEC) have significant implications for our understanding of the very early
universe. We present a novel approach to generate PBHs via the NEC violation in
a single-field inflationary scenario. In our scenario, the universe transitions
from a first slow-roll inflation stage with a Hubble parameter $H =
H_{\text{inf}1}$ to a second slow-roll inflation stage with $H =
H_{\text{inf}2}\gg H_{\text{inf}1}$, passing through an intermediate stage of
NEC violation. The NEC violation naturally enhances the primordial scalar power
spectrum at a certain wavelength, leading to the production of PBHs with masses
and abundances of observational interest. We also investigate the
phenomenological signatures of scalar-induced gravitational waves (SIGWs)
resulting from the enhanced density perturbations. Our work highlights the
potential of utilizing a combination of PBHs, SIGWs, and primordial
gravitational waves as a valuable probe for studying NEC violation during
inflation, opening up new avenues for exploring the early universe.
| [
{
"created": "Thu, 18 May 2023 12:49:32 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jul 2024 12:42:13 GMT",
"version": "v2"
}
] | 2024-07-10 | [
[
"Cai",
"Yong",
""
],
[
"Zhu",
"Mian",
""
],
[
"Piao",
"Yun-Song",
""
]
] | Primordial black holes (PBHs) and the violation of the null energy condition (NEC) have significant implications for our understanding of the very early universe. We present a novel approach to generate PBHs via the NEC violation in a single-field inflationary scenario. In our scenario, the universe transitions from a first slow-roll inflation stage with a Hubble parameter $H = H_{\text{inf}1}$ to a second slow-roll inflation stage with $H = H_{\text{inf}2}\gg H_{\text{inf}1}$, passing through an intermediate stage of NEC violation. The NEC violation naturally enhances the primordial scalar power spectrum at a certain wavelength, leading to the production of PBHs with masses and abundances of observational interest. We also investigate the phenomenological signatures of scalar-induced gravitational waves (SIGWs) resulting from the enhanced density perturbations. Our work highlights the potential of utilizing a combination of PBHs, SIGWs, and primordial gravitational waves as a valuable probe for studying NEC violation during inflation, opening up new avenues for exploring the early universe. |
0903.2678 | Paul Wesson | Paul S. Wesson | Classical Universes and Quantized Particles from Five-Dimensional Null
Paths | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All objects in 4D spacetime may in principle travel on null paths in a 5D
mani-fold. We use this, together with a change in the extra coordinate and the
signature of the metric, to construct a simple model of a classical universe
and a quantized particle. There are notable implications for the Weak
Equivalence Principle and the cosmological constant, and for astrophysics.
| [
{
"created": "Sun, 15 Mar 2009 23:34:29 GMT",
"version": "v1"
}
] | 2009-03-17 | [
[
"Wesson",
"Paul S.",
""
]
] | All objects in 4D spacetime may in principle travel on null paths in a 5D mani-fold. We use this, together with a change in the extra coordinate and the signature of the metric, to construct a simple model of a classical universe and a quantized particle. There are notable implications for the Weak Equivalence Principle and the cosmological constant, and for astrophysics. |
2304.10030 | Anna Ijjas | Anna Ijjas | Slow Contraction and the Weyl Curvature Hypothesis | 5 pages, 5 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the power of numerical relativity, we show that, beginning from generic
initial conditions that are far from flat, homogeneous and isotropic and have a
large Weyl curvature, a period of slow contraction rapidly drives spacetime
towards vanishingly small Weyl curvature as the total energy density grows,
thus providing a dynamical mechanism that satisfies the Weyl Curvature
Hypothesis. We also demonstrate a tight correlation between the Weyl Curvature
Hypothesis and ultralocal behavior for canonical scalar fields with a
sufficiently steep negative potential energy density.
| [
{
"created": "Thu, 20 Apr 2023 01:01:46 GMT",
"version": "v1"
}
] | 2023-04-24 | [
[
"Ijjas",
"Anna",
""
]
] | Using the power of numerical relativity, we show that, beginning from generic initial conditions that are far from flat, homogeneous and isotropic and have a large Weyl curvature, a period of slow contraction rapidly drives spacetime towards vanishingly small Weyl curvature as the total energy density grows, thus providing a dynamical mechanism that satisfies the Weyl Curvature Hypothesis. We also demonstrate a tight correlation between the Weyl Curvature Hypothesis and ultralocal behavior for canonical scalar fields with a sufficiently steep negative potential energy density. |
2204.07274 | Marc Holman | Marc Holman | Spatial Geometry of the Large-Scale Universe: The Role of Quantum
Gravity, Dark Energy and other Unknowns | 4 pages, 1 figure. Contribution to the 2022 Cosmology session of the
56th Rencontres de Moriond | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It has been known for some time that the usual inference drawn from the
observed near-flatness of the large-scale Universe - namely the existence of a
cosmological "flatness problem", which is then taken as a partial, but key
motivation for assuming the existence of an ultra-short, inflationary expansion
of the very early Universe - is in itself deeply problematic. The present
contribution consolidates the earlier results regarding the absence of a
cosmological flatness problem of the sort that could potentially be resolved by
inflation, by clearing up some common misunderstandings and by presenting some
arguments in more detail.
| [
{
"created": "Fri, 15 Apr 2022 00:17:40 GMT",
"version": "v1"
}
] | 2022-04-18 | [
[
"Holman",
"Marc",
""
]
] | It has been known for some time that the usual inference drawn from the observed near-flatness of the large-scale Universe - namely the existence of a cosmological "flatness problem", which is then taken as a partial, but key motivation for assuming the existence of an ultra-short, inflationary expansion of the very early Universe - is in itself deeply problematic. The present contribution consolidates the earlier results regarding the absence of a cosmological flatness problem of the sort that could potentially be resolved by inflation, by clearing up some common misunderstandings and by presenting some arguments in more detail. |
2203.07074 | Ovidiu Racorean Mr | Ovidiu Racorean | The Born rule in a timeless universe | 14 page | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In canonical quantization of gravity the wave function of the universe is CPT
invariant. Thus, if the quantum state of the universe contains a particular
history, than it must contain, with the same probability, the time-reversed
image of that history as well. In this work, we investigate the meaning of this
statement in the context of the conditional probability interpretation of Page
and Wootters. Accordingly, we show that a time-reversed history of the universe
is consistent with the Page and Wootters mechanism and we derive a
time-reversed Schrodinger equation for the evolution of the rest of the
universe. Since the same particular quantum state is acquired both in an
individual history with time running forward and in its time-reversed image
history, we demonstrate that conditioning the state of the universe on the
hands of the clock showing a specific time results in the probability of
finding the rest of the universe system in a particular state. In this
scenario, we conjecture that probability interpretation is an emergent property
of the quantum world.
| [
{
"created": "Fri, 11 Mar 2022 09:57:09 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Sep 2022 11:16:38 GMT",
"version": "v2"
}
] | 2022-09-14 | [
[
"Racorean",
"Ovidiu",
""
]
] | In canonical quantization of gravity the wave function of the universe is CPT invariant. Thus, if the quantum state of the universe contains a particular history, than it must contain, with the same probability, the time-reversed image of that history as well. In this work, we investigate the meaning of this statement in the context of the conditional probability interpretation of Page and Wootters. Accordingly, we show that a time-reversed history of the universe is consistent with the Page and Wootters mechanism and we derive a time-reversed Schrodinger equation for the evolution of the rest of the universe. Since the same particular quantum state is acquired both in an individual history with time running forward and in its time-reversed image history, we demonstrate that conditioning the state of the universe on the hands of the clock showing a specific time results in the probability of finding the rest of the universe system in a particular state. In this scenario, we conjecture that probability interpretation is an emergent property of the quantum world. |
gr-qc/0605029 | Tetsuya Shiromizu | Tetsuya Shiromizu, Sumio Yamada, Hirotaka Yoshino | On existence of matter outside a static black hole | 4pages, final version accepted for publication in Journal of
Mathematical Physics | J.Math.Phys.47:112502,2006 | 10.1063/1.2383009 | null | gr-qc astro-ph math.DG | null | It is expected that matter composed of a perfect fluid cannot be at rest
outside of a black hole if the spacetime is asymptotically flat and static
(non-rotating). However, there has not been a rigorous proof for this
expectation without assuming spheical symmetry. In this paper, we provide a
proof of non-existence of matter composed of a perfect fluid in static black
hole spacetimes under certain conditions, which can be interpreted as a
relation between the stellar mass and the black hole mass.
| [
{
"created": "Fri, 5 May 2006 00:54:10 GMT",
"version": "v1"
},
{
"created": "Tue, 9 May 2006 23:11:34 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Oct 2006 23:45:56 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Shiromizu",
"Tetsuya",
""
],
[
"Yamada",
"Sumio",
""
],
[
"Yoshino",
"Hirotaka",
""
]
] | It is expected that matter composed of a perfect fluid cannot be at rest outside of a black hole if the spacetime is asymptotically flat and static (non-rotating). However, there has not been a rigorous proof for this expectation without assuming spheical symmetry. In this paper, we provide a proof of non-existence of matter composed of a perfect fluid in static black hole spacetimes under certain conditions, which can be interpreted as a relation between the stellar mass and the black hole mass. |
gr-qc/0311038 | Matthew R. Francis | Matthew R. Francis and Arthur Kosowsky | Geodesics in the Generalized Schwarzschild Solution | 7 pages, 1 figure; revised to reflect referee comments; submitted to
Am. J. of Phys | Am.J.Phys. 72 (2004) 1204-1209 | 10.1119/1.1701846 | null | gr-qc | null | Since Schwarzshild discovered the point-mass solution to Einstein's equations
that bears his name, many equivalent forms of the metric have been catalogued.
Using an elementary coordinate transformation, we derive the most general form
for the stationary, spherically-symmetric vacuum metric, which contains one
free function. Different choices for the function correspond to common
expressions for the line element. From the general metric, we obtain particle
and photon trajectories, and use them to specify several time coordinates
adapted to physical situations. The most general form of the metric is only
slightly more complicated than the Schwarzschild form, which argues effectively
for teaching the general line element in place of the diagonal metric.
| [
{
"created": "Wed, 12 Nov 2003 20:38:26 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jan 2004 18:36:18 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Francis",
"Matthew R.",
""
],
[
"Kosowsky",
"Arthur",
""
]
] | Since Schwarzshild discovered the point-mass solution to Einstein's equations that bears his name, many equivalent forms of the metric have been catalogued. Using an elementary coordinate transformation, we derive the most general form for the stationary, spherically-symmetric vacuum metric, which contains one free function. Different choices for the function correspond to common expressions for the line element. From the general metric, we obtain particle and photon trajectories, and use them to specify several time coordinates adapted to physical situations. The most general form of the metric is only slightly more complicated than the Schwarzschild form, which argues effectively for teaching the general line element in place of the diagonal metric. |
2102.01600 | A. Yu. Petrov | J. R. Nascimento, A. Yu. Petrov, P. J. Porf\'irio | On the causality properties in non-local gravity theories | 16 pages, version accepted to EPJ C | European Physical Journal C81, 815 (2021) | 10.1140/epjc/s10052-021-09640-5 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | It is well known that non-local theories of gravity have been a flourish
arena of studies for many reasons, for instance, the UV incompleteness of
General Relativity (GR). In this paper we check the consistency of
ST-homogeneous G\"{o}del-type metrics within the non-local gravity framework.
The non-local models considered here are ghost-free but not necessarily
renormalizable since we focus on the classical solutions of the field
equations. Furthermore, the non-locality is displayed in the action through
transcendental entire functions of the d'Alembert operator $\Box$ that are
mathematically represented by a power series of the $\Box$-operator. We find
two exactly solutions for the field equations correspondent to the degenerate
($\omega=0$) and hyperbolic ($m^{2}=4\omega^2$) classes of ST-homogeneous
G\"{o}del-type metrics.
| [
{
"created": "Tue, 2 Feb 2021 16:51:44 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Sep 2021 16:11:13 GMT",
"version": "v2"
}
] | 2021-09-16 | [
[
"Nascimento",
"J. R.",
""
],
[
"Petrov",
"A. Yu.",
""
],
[
"Porfírio",
"P. J.",
""
]
] | It is well known that non-local theories of gravity have been a flourish arena of studies for many reasons, for instance, the UV incompleteness of General Relativity (GR). In this paper we check the consistency of ST-homogeneous G\"{o}del-type metrics within the non-local gravity framework. The non-local models considered here are ghost-free but not necessarily renormalizable since we focus on the classical solutions of the field equations. Furthermore, the non-locality is displayed in the action through transcendental entire functions of the d'Alembert operator $\Box$ that are mathematically represented by a power series of the $\Box$-operator. We find two exactly solutions for the field equations correspondent to the degenerate ($\omega=0$) and hyperbolic ($m^{2}=4\omega^2$) classes of ST-homogeneous G\"{o}del-type metrics. |
1812.06759 | Dmitry Chirkov | Dmitry Chirkov, Alexey Toporensky | Splitting into two isotropic subspaces as a result of cosmological
evolution in Einstein-Gauss-Bonnet gravity | 10 pages, 2 figures | Grav. Cosmol. Vol. 25, No. 3, p. 243 (2019) | 10.1134/S0202289319030058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider numerically dynamics of a flat anisotropic Universe in
Einstein-Gauss-Bonnet gravity with positive $\Lambda$ in dimensionalities 5+1
and 6+1. We identify three possible outcomes of the evolution, one singular and
two nonsingular. First nonsingular outcome is oscillatory. Second is the known
exponential solution. The simplest version of it is the isotropic de Sitter
solution. In Gauss-Bonnet cosmology there exist also anisotropic exponential
solutions. When an exponential solution being an outcome of cosmological
evolution has two different Hubble parameters, the evolution leads from
initially totally anisotropic stage to a sum of two isotropic subspaces. We
show that such type of evolution is rather typical and possible even in the
case when de Sitter solution also exists.
| [
{
"created": "Mon, 17 Dec 2018 13:40:35 GMT",
"version": "v1"
},
{
"created": "Fri, 3 May 2019 14:49:21 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Jul 2019 18:59:13 GMT",
"version": "v3"
}
] | 2019-07-25 | [
[
"Chirkov",
"Dmitry",
""
],
[
"Toporensky",
"Alexey",
""
]
] | We consider numerically dynamics of a flat anisotropic Universe in Einstein-Gauss-Bonnet gravity with positive $\Lambda$ in dimensionalities 5+1 and 6+1. We identify three possible outcomes of the evolution, one singular and two nonsingular. First nonsingular outcome is oscillatory. Second is the known exponential solution. The simplest version of it is the isotropic de Sitter solution. In Gauss-Bonnet cosmology there exist also anisotropic exponential solutions. When an exponential solution being an outcome of cosmological evolution has two different Hubble parameters, the evolution leads from initially totally anisotropic stage to a sum of two isotropic subspaces. We show that such type of evolution is rather typical and possible even in the case when de Sitter solution also exists. |
gr-qc/9601024 | null | Enrico Montanari, Pierluigi Fortini (University of Ferrara and INFN
sezione di Ferrara, Italy) | Coherent interaction of a monochromatic gravitational wave with both
elastic bodies and electromagnetic circuits | RevTeX, 8 pages plus 2 postscript figures; widely revised text; noise
analisys enhanced. Approved for publication in Phys. Rev. D | Phys.Rev. D59 (1999) 024001 | 10.1103/PhysRevD.59.024001 | null | gr-qc astro-ph | null | The interaction of a gravitational wave with a system made of an RLC circuit
forming one end of a mechanical harmonic oscillator is investigated. We show
that, in some configurations, the coherent interaction of the wave with both
the mechanical oscillator and the RLC circuit gives rise to a mechanical
quality factor increase of the electromagnetic signal. When this system is used
as an amplifier of gravitational periodic signals in the frequency range
50-1000 Hz, at ultracryogenic temperatures and for sufficiently long
integration times (up to 4 months), a sensitivity of 10^(-24)-10^(-27) on the
amplitude of the metric could be achieved when thermal noise, shot noise and
amplifier back--action are considered.
| [
{
"created": "Wed, 17 Jan 1996 12:01:16 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Aug 1998 14:53:47 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Montanari",
"Enrico",
"",
"University of Ferrara and INFN\n sezione di Ferrara, Italy"
],
[
"Fortini",
"Pierluigi",
"",
"University of Ferrara and INFN\n sezione di Ferrara, Italy"
]
] | The interaction of a gravitational wave with a system made of an RLC circuit forming one end of a mechanical harmonic oscillator is investigated. We show that, in some configurations, the coherent interaction of the wave with both the mechanical oscillator and the RLC circuit gives rise to a mechanical quality factor increase of the electromagnetic signal. When this system is used as an amplifier of gravitational periodic signals in the frequency range 50-1000 Hz, at ultracryogenic temperatures and for sufficiently long integration times (up to 4 months), a sensitivity of 10^(-24)-10^(-27) on the amplitude of the metric could be achieved when thermal noise, shot noise and amplifier back--action are considered. |
gr-qc/0404044 | Belinch\'on Jos\'e Antonio | Jos\'e Antonio Belinch\'on and Antonio Alfonso-Faus | A Theory of time-varying Constants | 15 pages, RevTeX4 | Int.J.Mod.Phys. D10 (2001) 299-310 | 10.1142/S0218271801000974 | null | gr-qc | null | We present a flat (K=0) cosmological model, described by a perfect fluid with
the ``constants'' $G,c$ and $\Lambda$ varying with cosmological time $t$. We
introduce Planck\'s ``constant'' $\hbar$ in the field equations through the
equation of state for the energy density of radiation. We then determine the
behaviour of the ``constants'' by using the zero divergence of the second
member of the modified Einstein\'s field equations i.e.
$div(\frac{G}{c^{4}}T_{i}^{j}+\delta_{i}^{j}\Lambda)=0,$ together with the
equation of state and the Einstein cosmological equations. Assuming realistic
physical and mathematical conditions we obtain a consistent result with $\hbar
c=constant$. In this way we obtain gauge invariance for the Schr\"{o}dinger
equation and the behaviour of the remaining ``constants''
| [
{
"created": "Fri, 9 Apr 2004 16:39:54 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Belinchón",
"José Antonio",
""
],
[
"Alfonso-Faus",
"Antonio",
""
]
] | We present a flat (K=0) cosmological model, described by a perfect fluid with the ``constants'' $G,c$ and $\Lambda$ varying with cosmological time $t$. We introduce Planck\'s ``constant'' $\hbar$ in the field equations through the equation of state for the energy density of radiation. We then determine the behaviour of the ``constants'' by using the zero divergence of the second member of the modified Einstein\'s field equations i.e. $div(\frac{G}{c^{4}}T_{i}^{j}+\delta_{i}^{j}\Lambda)=0,$ together with the equation of state and the Einstein cosmological equations. Assuming realistic physical and mathematical conditions we obtain a consistent result with $\hbar c=constant$. In this way we obtain gauge invariance for the Schr\"{o}dinger equation and the behaviour of the remaining ``constants'' |
2308.11323 | Gast\'on Creci | Gast\'on Creci, Tanja Hinderer and Jan Steinhoff | Tidal properties of neutron stars in scalar-tensor theories of gravity | v2, 44 pages, 29 figures. Discussion, references and plots added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A major science goal of gravitational-wave (GW) observations is to probe the
nature of gravity and constrain modifications to General Relativity. An
established class of modified gravity theories are scalar-tensor models, which
introduce an extra scalar degree of freedom. This affects the internal
structure of neutron stars (NSs), as well as their dynamics and GWs in binary
systems, where distinct novel features can arise from the appearance of scalar
condensates in parts of the parameter space. To improve the robustness of the
analyses of such GW events requires advances in modeling
internal-structure-dependent phenomena in scalar-tensor theories. We develop an
effective description of potentially scalarized NSs on large scales, where
information about the interior is encoded in characteristic Love numbers or
equivalently tidal deformabilities. We demonstrate that three independent tidal
deformabilities are needed to characterize the configurations: a scalar,
tensor, and a novel 'mixed' parameter, and develop the general methodology to
compute these quantities. We also present case studies for different NS
equations of state and scalar properties and provide the mapping between the
deformabilities in different frames often used for calculations. Our results
have direct applications for future GW tests of gravity and studies of
potential degeneracies with other uncertain physics such as the equation of
state or presence of dark matter in NS binary systems.
| [
{
"created": "Tue, 22 Aug 2023 09:55:38 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Oct 2023 12:31:47 GMT",
"version": "v2"
}
] | 2023-10-25 | [
[
"Creci",
"Gastón",
""
],
[
"Hinderer",
"Tanja",
""
],
[
"Steinhoff",
"Jan",
""
]
] | A major science goal of gravitational-wave (GW) observations is to probe the nature of gravity and constrain modifications to General Relativity. An established class of modified gravity theories are scalar-tensor models, which introduce an extra scalar degree of freedom. This affects the internal structure of neutron stars (NSs), as well as their dynamics and GWs in binary systems, where distinct novel features can arise from the appearance of scalar condensates in parts of the parameter space. To improve the robustness of the analyses of such GW events requires advances in modeling internal-structure-dependent phenomena in scalar-tensor theories. We develop an effective description of potentially scalarized NSs on large scales, where information about the interior is encoded in characteristic Love numbers or equivalently tidal deformabilities. We demonstrate that three independent tidal deformabilities are needed to characterize the configurations: a scalar, tensor, and a novel 'mixed' parameter, and develop the general methodology to compute these quantities. We also present case studies for different NS equations of state and scalar properties and provide the mapping between the deformabilities in different frames often used for calculations. Our results have direct applications for future GW tests of gravity and studies of potential degeneracies with other uncertain physics such as the equation of state or presence of dark matter in NS binary systems. |
1112.2202 | Llu\'is Bel | Llu\'is Bel | OPERA and the GPS | 4 pages | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I comment about the adequacy of the GPS to model a particularly defined
synchronization in a rotating frame of reference described in a general
relativistic framework.
| [
{
"created": "Thu, 8 Dec 2011 07:35:08 GMT",
"version": "v1"
}
] | 2011-12-12 | [
[
"Bel",
"Lluís",
""
]
] | I comment about the adequacy of the GPS to model a particularly defined synchronization in a rotating frame of reference described in a general relativistic framework. |
2305.04709 | Argyro Sasli | Argyro Sasli, Nikolaos Karnesis, Nikolaos Stergioulas | Heavy-tailed likelihoods for robustness against data outliers:
Applications to the analysis of gravitational wave data | 18 pages, 7 figures, matches published version | Phys. Rev. D 108, 103005 (2023) | 10.1103/PhysRevD.108.103005 | null | gr-qc astro-ph.IM physics.data-an physics.space-ph | http://creativecommons.org/licenses/by/4.0/ | In recent years, the field of Gravitational Wave Astronomy has flourished.
With the advent of more sophisticated ground-based detectors and space-based
observatories, it is anticipated that Gravitational Wave events will be
detected at a much higher rate in the near future. One of the future data
analysis challenges is performing robust statistical inference in the presence
of detector noise transients or non-stationarities, as well as in the presence
of stochastic Gravitational Wave signals of possible astrophysical and/or
cosmological origin. The incomplete knowledge of the total noise of the
observatory can introduce challenges in parameter estimation of detected
sources. In this work, we propose a heavy-tailed, Hyperbolic likelihood, based
on the Generalized Hyperbolic distribution. With the Hyperbolic likelihood we
obtain a robust data analysis framework against data outliers, noise
non-stationarities, and possible inaccurate modeling of the noise power
spectral density. We apply this methodology to examples drawn from
gravitational wave astronomy, and in particular to synthetic data sets from the
planned LISA mission.
| [
{
"created": "Mon, 8 May 2023 13:47:08 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Nov 2023 08:40:18 GMT",
"version": "v2"
}
] | 2023-11-07 | [
[
"Sasli",
"Argyro",
""
],
[
"Karnesis",
"Nikolaos",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | In recent years, the field of Gravitational Wave Astronomy has flourished. With the advent of more sophisticated ground-based detectors and space-based observatories, it is anticipated that Gravitational Wave events will be detected at a much higher rate in the near future. One of the future data analysis challenges is performing robust statistical inference in the presence of detector noise transients or non-stationarities, as well as in the presence of stochastic Gravitational Wave signals of possible astrophysical and/or cosmological origin. The incomplete knowledge of the total noise of the observatory can introduce challenges in parameter estimation of detected sources. In this work, we propose a heavy-tailed, Hyperbolic likelihood, based on the Generalized Hyperbolic distribution. With the Hyperbolic likelihood we obtain a robust data analysis framework against data outliers, noise non-stationarities, and possible inaccurate modeling of the noise power spectral density. We apply this methodology to examples drawn from gravitational wave astronomy, and in particular to synthetic data sets from the planned LISA mission. |
gr-qc/0001009 | null | Dan N. Vollick | Quantum Inequalities in Curved Two Dimensional Spacetimes | 10 pages, LaTeX | Phys.Rev. D61 (2000) 084022 | 10.1103/PhysRevD.61.084022 | null | gr-qc hep-th | null | In quantum field theory there exist states for which the energy density is
negative. It is important that these negative energy densities satisfy
constraints, such as quantum inequalities, to minimize possible violations of
causality, the second law of thermodynamics, and cosmic censorship. In this
paper I show that conformally invariant scalar and Dirac fields satisfy quantum
inequalities in two dimensional spacetimes with a conformal factor that depends
on $x$ only or on $t$ only. These inequalities are then applied to two
dimensional black hole and cosmological spacetimes. It is shown that the bound
on the negative energies diverges to minus infinity as the event horizon or
initial singularity is approached. Thus, neglecting back reaction, negative
energies become unconstrained near the horizon or initial singularity. The
results of this paper also support the hypothesis that the quantum interest
conjecture applies only to deviations from the vacuum polarization energy, not
to the total energy.
| [
{
"created": "Wed, 5 Jan 2000 23:20:07 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Vollick",
"Dan N.",
""
]
] | In quantum field theory there exist states for which the energy density is negative. It is important that these negative energy densities satisfy constraints, such as quantum inequalities, to minimize possible violations of causality, the second law of thermodynamics, and cosmic censorship. In this paper I show that conformally invariant scalar and Dirac fields satisfy quantum inequalities in two dimensional spacetimes with a conformal factor that depends on $x$ only or on $t$ only. These inequalities are then applied to two dimensional black hole and cosmological spacetimes. It is shown that the bound on the negative energies diverges to minus infinity as the event horizon or initial singularity is approached. Thus, neglecting back reaction, negative energies become unconstrained near the horizon or initial singularity. The results of this paper also support the hypothesis that the quantum interest conjecture applies only to deviations from the vacuum polarization energy, not to the total energy. |
1005.4926 | Stephan Schlamminger | Stephan Schlamminger, Charles A. Hagedorn, and Jens H. Gundlach | Indirect Evidence for L\'evy Walks in Squeeze Film Damping | 5 pages 5 figures accepted for PRD; typo in equation 3 and figure 1
fixed | Phys.Rev.D81:123008,2010 | 10.1103/PhysRevD.81.123008 | LIGO-P1000013 | gr-qc cond-mat.stat-mech physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Molecular flow gas damping of mechanical motion in confined geometries, and
its associated noise, is important in a variety of fields, including precision
measurement, gravitational wave detection, and MEMS devices. We used two
torsion balance instruments to measure the strength and distance-dependence of
`squeeze film' damping. Measured quality factors derived from free decay of
oscillation are consistent with gas particle superdiffusion in L\'evy walks and
inconsistent with those expected from traditional Gaussian random walk particle
motion. The distance-dependence of squeeze film damping observed in our
experiments is in agreement with a parameter-free Monte Carlo simulation. The
squeeze film damping of the motion of a plate suspended a distance d away from
a parallel surface scales with a fractional power between 1/d and 1/d^2.
| [
{
"created": "Wed, 26 May 2010 20:00:02 GMT",
"version": "v1"
},
{
"created": "Sat, 29 May 2010 04:43:17 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Schlamminger",
"Stephan",
""
],
[
"Hagedorn",
"Charles A.",
""
],
[
"Gundlach",
"Jens H.",
""
]
] | Molecular flow gas damping of mechanical motion in confined geometries, and its associated noise, is important in a variety of fields, including precision measurement, gravitational wave detection, and MEMS devices. We used two torsion balance instruments to measure the strength and distance-dependence of `squeeze film' damping. Measured quality factors derived from free decay of oscillation are consistent with gas particle superdiffusion in L\'evy walks and inconsistent with those expected from traditional Gaussian random walk particle motion. The distance-dependence of squeeze film damping observed in our experiments is in agreement with a parameter-free Monte Carlo simulation. The squeeze film damping of the motion of a plate suspended a distance d away from a parallel surface scales with a fractional power between 1/d and 1/d^2. |
gr-qc/0612154 | Farook Rahaman | F.Rahaman, A. Ghosh and M. Kalam | Does phantom energy produce black hole? | 5 pages. Published in Nuovo Cimento 121B, 279 (2006) | NuovoCim.B121:279,2006 | 10.1393/ncb/i2006-10033-x | null | gr-qc | null | We have found an exact solution of spherically symmetrical Einstein equations
describing a black hole with a special type phantom energy source. It is
surprising to note that our solution is analogous to Reissner-Nordstr\"{o}m
black hole.
| [
{
"created": "Sat, 23 Dec 2006 12:49:11 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Rahaman",
"F.",
""
],
[
"Ghosh",
"A.",
""
],
[
"Kalam",
"M.",
""
]
] | We have found an exact solution of spherically symmetrical Einstein equations describing a black hole with a special type phantom energy source. It is surprising to note that our solution is analogous to Reissner-Nordstr\"{o}m black hole. |
gr-qc/9711070 | Sumati Surya | Fay Dowker (Imperial Coll., London) and Sumati Surya (I.U.C.A.A.,
Pune) | Topology Change and Causal Continuity | Latex, 28 pages, 10 figures, small changes in text (one figure
removed), conclusions remain unchanged. Accepted for publication in Physical
Review D | Phys. Rev. D 58, 124019 (1998) | 10.1103/PhysRevD.58.124019 | Imperial/TP/97 -98/12 | gr-qc hep-th | null | The result that, for a scalar quantum field propagating on a ``trousers''
topology in 1+1 dimensions, the crotch singularity is a source for an infinite
burst of energy has been used to argue against the occurrence of topology
change in quantum gravity. We draw attention to a conjecture due to Sorkin that
it may be the particular type of topology change involved in the trousers
transition that is problematic and that other topology changes may not cause
the same difficulties. The conjecture links the singular behaviour to the
existence of ``causal discontinuities'' in the spacetime and relies on a
classification of topology changes using Morse theory. We investigate various
topology changing transitions, including the pair production of black holes and
of topological geons, in the light of these ideas.
| [
{
"created": "Sun, 23 Nov 1997 13:07:12 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Aug 1998 10:54:35 GMT",
"version": "v2"
}
] | 2016-08-25 | [
[
"Dowker",
"Fay",
"",
"Imperial Coll., London"
],
[
"Surya",
"Sumati",
"",
"I.U.C.A.A.,\n Pune"
]
] | The result that, for a scalar quantum field propagating on a ``trousers'' topology in 1+1 dimensions, the crotch singularity is a source for an infinite burst of energy has been used to argue against the occurrence of topology change in quantum gravity. We draw attention to a conjecture due to Sorkin that it may be the particular type of topology change involved in the trousers transition that is problematic and that other topology changes may not cause the same difficulties. The conjecture links the singular behaviour to the existence of ``causal discontinuities'' in the spacetime and relies on a classification of topology changes using Morse theory. We investigate various topology changing transitions, including the pair production of black holes and of topological geons, in the light of these ideas. |
gr-qc/0606069 | Alok Laddha | Alok Laddha | Polymer quantization of CGHS model- I | 50 pages, 2 figures | Class.Quant.Grav.24:4969-4988,2007 | 10.1088/0264-9381/24/20/005 | IMSc/2006/6/16 | gr-qc | null | We present a polymer(loop) quantization of a two dimensional theory of
dilatonic gravity known as the CGHS model. We recast the theory as a
parametrized free field theory on a flat 2-dimensional spacetime and quantize
the resulting phase space using techniques of loop quantization. The resulting
(kinematical) Hilbert space admits a unitary representation of the spacetime
diffeomorphism group. We obtain the complete spectrum of the theory using a
technique known as group averaging and perform quantization of Dirac
observables on the resulting Hilbert space. We argue that the algebra of Dirac
observables gets deformed in the quantum theory. Combining the ideas from
parametrized field theory with certain relational observables, evolution is
defined in the quantum theory in the Heisenberg picture. Finally the dilaton
field is quantized on the physical Hilbert space which carries information
about quantum geometry.
| [
{
"created": "Fri, 16 Jun 2006 09:42:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Laddha",
"Alok",
""
]
] | We present a polymer(loop) quantization of a two dimensional theory of dilatonic gravity known as the CGHS model. We recast the theory as a parametrized free field theory on a flat 2-dimensional spacetime and quantize the resulting phase space using techniques of loop quantization. The resulting (kinematical) Hilbert space admits a unitary representation of the spacetime diffeomorphism group. We obtain the complete spectrum of the theory using a technique known as group averaging and perform quantization of Dirac observables on the resulting Hilbert space. We argue that the algebra of Dirac observables gets deformed in the quantum theory. Combining the ideas from parametrized field theory with certain relational observables, evolution is defined in the quantum theory in the Heisenberg picture. Finally the dilaton field is quantized on the physical Hilbert space which carries information about quantum geometry. |
gr-qc/0101118 | Maurizio Gasperini | G. De Risi and M. Gasperini | A diagrammatic approach to the spectrum of cosmological perturbations | 12 pages, Latex, four figures included using epsfig. To appear in
Phys. Lett. B | Phys.Lett. B503 (2001) 140-146 | 10.1016/S0370-2693(01)00220-9 | BA-TH/00-398 | gr-qc hep-th | null | We compute the spectral distribution of the quantum fluctuations of the
vacuum, amplified by inflation, after an arbitrary number of background
transitions. Using a graphic representation of the process we find that the
final spectrum can be completely determined trough a synthetic set of working
rules, and a list of simple algebraic computations.
| [
{
"created": "Tue, 30 Jan 2001 15:11:08 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"De Risi",
"G.",
""
],
[
"Gasperini",
"M.",
""
]
] | We compute the spectral distribution of the quantum fluctuations of the vacuum, amplified by inflation, after an arbitrary number of background transitions. Using a graphic representation of the process we find that the final spectrum can be completely determined trough a synthetic set of working rules, and a list of simple algebraic computations. |
2105.00360 | Eleonora Giovannetti | E. Giovannetti, G. Montani, S. Schiattarella | Semiclassical and quantum features of the Bianchi I cosmology in the
polymer representation | null | Phys. Rev. D 105, 064011 Published 7 March 2022 | 10.1103/PhysRevD.105.064011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the Bianchi I cosmology in the presence of a massless scalar field
and describe its dynamics via a semiclassical and quantum polymer approach. We
study the morphology of the Big Bounce by adopting three different sets of
configurational variables: the Ashtekar connections, a set of anisotropic
volume-like coordinates and the Universe volume plus two anisotropy coordinates
(the latter two sets of variables would coincide in the case of an isotropic
Universe). In the semiclassical analysis we demonstrate that the value of the
critical matter energy density depends on the Cauchy problem for the dynamics
when adopting the Ashtekar connections or the anisotropic volume-like
coordinates. On the contrary, when the Universe volume is considered as a
configurational coordinate, we are able to derive a polymer-modified Friedmann
equation for the Bianchi I model, from which the expression of the critical
energy density can be derived. This analysis shows that the Big Bounce has
universal features only when the Universe volume is defined on the polymer
lattice. Then, a cosmological constant is included in the Ashtekar connections'
formulation and some interesting results are mentioned making a comparison
between the synchronous dynamics and that one when the scalar field is taken as
a relational time. From a pure quantum point of view, we investigate the
Bianchi I dynamics in terms of the Ashtekar connections. We apply the ADM
reduction of the variational principle and then we quantize the system. We
study the resulting Schr\"{o}dinger dynamics, stressing that the behavior of
the wave packet peak over time singles out common features with the
semiclassical trajectories, confirming the non-universal character of the
emerging Big Bounce also on a quantum level.
| [
{
"created": "Sun, 2 May 2021 00:03:27 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Aug 2021 21:01:58 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Mar 2022 13:54:19 GMT",
"version": "v3"
}
] | 2022-03-09 | [
[
"Giovannetti",
"E.",
""
],
[
"Montani",
"G.",
""
],
[
"Schiattarella",
"S.",
""
]
] | We analyze the Bianchi I cosmology in the presence of a massless scalar field and describe its dynamics via a semiclassical and quantum polymer approach. We study the morphology of the Big Bounce by adopting three different sets of configurational variables: the Ashtekar connections, a set of anisotropic volume-like coordinates and the Universe volume plus two anisotropy coordinates (the latter two sets of variables would coincide in the case of an isotropic Universe). In the semiclassical analysis we demonstrate that the value of the critical matter energy density depends on the Cauchy problem for the dynamics when adopting the Ashtekar connections or the anisotropic volume-like coordinates. On the contrary, when the Universe volume is considered as a configurational coordinate, we are able to derive a polymer-modified Friedmann equation for the Bianchi I model, from which the expression of the critical energy density can be derived. This analysis shows that the Big Bounce has universal features only when the Universe volume is defined on the polymer lattice. Then, a cosmological constant is included in the Ashtekar connections' formulation and some interesting results are mentioned making a comparison between the synchronous dynamics and that one when the scalar field is taken as a relational time. From a pure quantum point of view, we investigate the Bianchi I dynamics in terms of the Ashtekar connections. We apply the ADM reduction of the variational principle and then we quantize the system. We study the resulting Schr\"{o}dinger dynamics, stressing that the behavior of the wave packet peak over time singles out common features with the semiclassical trajectories, confirming the non-universal character of the emerging Big Bounce also on a quantum level. |
1604.00495 | Gon\c{c}alo Quinta | Gon\c{c}alo M. Quinta, Antonino Flachi, Jos\'e P. S. Lemos | Vacuum polarization in asymptotically Lifshitz black holes | null | Phys. Rev. D 93, 124073 (2016) | 10.1103/PhysRevD.93.124073 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There has been considerable interest in applying the gauge/gravity duality to
condensed matter theories with particular attention being devoted to gravity
duals (Lifshitz spacetimes) of theories that exhibit anisotropic scaling. In
this context, black hole solutions with Lifshitz asymptotics have also been
constructed aiming at incorporating finite temperature effects. The goal here
is to look at quantum polarization effects in these spacetimes, and to this
aim, we develop a way to compute the coincidence limit of the Green's function
for massive, non-minimally coupled scalar fields, adapting to the present
situation the analysis developed for the case of asymptotically anti de Sitter
black holes. The basics are similar to previous calculations, however in the
Lifshitz case one needs to extend previous results to include a more general
form for the metric and dependence on the dynamical exponent. All formulae are
shown to reduce to the AdS case studied before once the value of the dynamical
exponent is set to unity and the metric functions are accordingly chosen. The
analytical results we present are general and can be applied to a variety of
cases, in fact, to all spherically symmetric Lifshitz black hole solutions. We
also implement the numerical analysis choosing some known Lifshitz black hole
solutions as illustration.
| [
{
"created": "Sat, 2 Apr 2016 12:40:02 GMT",
"version": "v1"
}
] | 2016-07-06 | [
[
"Quinta",
"Gonçalo M.",
""
],
[
"Flachi",
"Antonino",
""
],
[
"Lemos",
"José P. S.",
""
]
] | There has been considerable interest in applying the gauge/gravity duality to condensed matter theories with particular attention being devoted to gravity duals (Lifshitz spacetimes) of theories that exhibit anisotropic scaling. In this context, black hole solutions with Lifshitz asymptotics have also been constructed aiming at incorporating finite temperature effects. The goal here is to look at quantum polarization effects in these spacetimes, and to this aim, we develop a way to compute the coincidence limit of the Green's function for massive, non-minimally coupled scalar fields, adapting to the present situation the analysis developed for the case of asymptotically anti de Sitter black holes. The basics are similar to previous calculations, however in the Lifshitz case one needs to extend previous results to include a more general form for the metric and dependence on the dynamical exponent. All formulae are shown to reduce to the AdS case studied before once the value of the dynamical exponent is set to unity and the metric functions are accordingly chosen. The analytical results we present are general and can be applied to a variety of cases, in fact, to all spherically symmetric Lifshitz black hole solutions. We also implement the numerical analysis choosing some known Lifshitz black hole solutions as illustration. |
1302.0093 | Andrew Makarenko | Salvatore Capozziello, Andrey N. Makarenko and Sergei D. Odintsov | Gauss-Bonnet dark energy by Lagrange multipliers | 14 pages, expanded version to appear in PRD | Phys. Rev. D 87, 084037 (2013) | 10.1103/PhysRevD.87.084037 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A string-inspired effective theory of gravity, containing Gauss-Bonnet
invariant interacting with a scalar field, is considered in view of obtaining
cosmological dark energy solutions. A Lagrange multiplier is inserted into the
action in order to achieve the cosmological reconstruction by selecting
suitable forms of couplings and potentials. Several cosmological exact
solutions (including dark energy of quintessence, phantom or Little Rip type)
are derived in presence and in absence of the Lagrange multiplier showing the
difference in the two dynamical approaches. In the models that we consider, the
Lagrange multiplier behaves as a sort of dust fluid that realizes the
transitions between matter dominated and dark energy epochs. The relation
between Lagrange multipliers and Noether symmetries is discussed.
| [
{
"created": "Fri, 1 Feb 2013 06:38:53 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Mar 2013 13:05:16 GMT",
"version": "v2"
}
] | 2013-04-23 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Makarenko",
"Andrey N.",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | A string-inspired effective theory of gravity, containing Gauss-Bonnet invariant interacting with a scalar field, is considered in view of obtaining cosmological dark energy solutions. A Lagrange multiplier is inserted into the action in order to achieve the cosmological reconstruction by selecting suitable forms of couplings and potentials. Several cosmological exact solutions (including dark energy of quintessence, phantom or Little Rip type) are derived in presence and in absence of the Lagrange multiplier showing the difference in the two dynamical approaches. In the models that we consider, the Lagrange multiplier behaves as a sort of dust fluid that realizes the transitions between matter dominated and dark energy epochs. The relation between Lagrange multipliers and Noether symmetries is discussed. |
gr-qc/9804041 | Jun'ichi Yokoyama | Jun'ichi Yokoyama (Stanford U. and Yukawa Institute, Kyoto U.) | Cosmological constraints on primordial black holes produced in the
near-critical gravitational collapse | 9 pages. Typos corrected. To appear in Physical Review D | Phys.Rev.D58:107502,1998 | 10.1103/PhysRevD.58.107502 | SU-ITP 98/18, YITP-98-23 | gr-qc astro-ph | null | The mass function of primordial black holes created through the near-critical
gravitational collapse is calculated in a manner fairly independent of the
statistical distribution of underlying density fluctuation, assuming that it
has a sharp peak on a specific scale. Comparing it with various cosmological
constraints on their mass spectrum, some newly excluded range is found in the
volume fraction of the region collapsing into black holes as a function of the
horizon mass.
| [
{
"created": "Sat, 18 Apr 1998 01:43:47 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jul 1998 18:01:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Yokoyama",
"Jun'ichi",
"",
"Stanford U. and Yukawa Institute, Kyoto U."
]
] | The mass function of primordial black holes created through the near-critical gravitational collapse is calculated in a manner fairly independent of the statistical distribution of underlying density fluctuation, assuming that it has a sharp peak on a specific scale. Comparing it with various cosmological constraints on their mass spectrum, some newly excluded range is found in the volume fraction of the region collapsing into black holes as a function of the horizon mass. |
1606.07924 | Jian-Yang Zhu | Long Chen and Jian-Yang Zhu | Inflationary spectra from a near $\Omega$-deformed space-time transition
point in Loop Quantum Cosmology | 7 pages,the final version published in PRD | Physical Review D 94,064037(2016) | 10.1103/PhysRevD.94.064037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Anomaly-free perturbations of loop quantum cosmology with holonomy
corrections reveal an $\Omega$ -deformed spacetime structure,
$\Omega:=1-2\rho/\rho_c$, where $\Omega<0$ indicates a Euclidean-like space and
$\Omega>0$ indicates a Lorentz-like space. It would be reasonable to give the
initial value at the spacetime transition point, $\rho=\rho_c/2$, but we find
that it is impossible to define a Minkowski-like vacuum even for large $k$
modes at that time. However, if we loosen the condition and give the initial
value slightly after $\Omega=0$, e.g., $\Omega\simeq 0.2$, the vacuum state can
be well defined and, furthermore the slow roll approximation also works well in
that region. Both scalar and tensor spectra are considered in the framework of
loop quantum cosmology with holonomy corrections. We find that if the energy
density is not too small in relation to $\rho_c/2$ when the considered $k$ mode
crossing the horizon, effective theory can give a much smaller scalar power
spectrum than classical theory and the spectrum of tensor perturbations could
blueshift. But when compared to other observations, since the energy densities
when the modes crossed the horizon were significantly smaller than $\rho_c$,the
results we get agree with previous work in the literature and with the
classical inflation theory.
| [
{
"created": "Sat, 25 Jun 2016 16:02:27 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2016 15:21:51 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"Chen",
"Long",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | Anomaly-free perturbations of loop quantum cosmology with holonomy corrections reveal an $\Omega$ -deformed spacetime structure, $\Omega:=1-2\rho/\rho_c$, where $\Omega<0$ indicates a Euclidean-like space and $\Omega>0$ indicates a Lorentz-like space. It would be reasonable to give the initial value at the spacetime transition point, $\rho=\rho_c/2$, but we find that it is impossible to define a Minkowski-like vacuum even for large $k$ modes at that time. However, if we loosen the condition and give the initial value slightly after $\Omega=0$, e.g., $\Omega\simeq 0.2$, the vacuum state can be well defined and, furthermore the slow roll approximation also works well in that region. Both scalar and tensor spectra are considered in the framework of loop quantum cosmology with holonomy corrections. We find that if the energy density is not too small in relation to $\rho_c/2$ when the considered $k$ mode crossing the horizon, effective theory can give a much smaller scalar power spectrum than classical theory and the spectrum of tensor perturbations could blueshift. But when compared to other observations, since the energy densities when the modes crossed the horizon were significantly smaller than $\rho_c$,the results we get agree with previous work in the literature and with the classical inflation theory. |
0806.3844 | Ion I. Cot{\ba}escu | Ion I Cotaescu | On the universality of the Carter and McLenaghan formula | 7 pages, no figures | Europhys.Lett.86:20003,2009 | 10.1209/0295-5075/86/20003 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the formula of the isometry generators of the spinor
representation given by Carter and McLenaghan is universal in the sense that
this holds for any representation either in local frames or even in natural
ones. The point-dependent spin matrices in natural frames are introduced for
any tensor representation deriving the covariant form of the isometry
generators in these frames.
| [
{
"created": "Tue, 24 Jun 2008 09:42:18 GMT",
"version": "v1"
}
] | 2014-10-08 | [
[
"Cotaescu",
"Ion I",
""
]
] | It is shown that the formula of the isometry generators of the spinor representation given by Carter and McLenaghan is universal in the sense that this holds for any representation either in local frames or even in natural ones. The point-dependent spin matrices in natural frames are introduced for any tensor representation deriving the covariant form of the isometry generators in these frames. |
gr-qc/9905022 | Roberto Scipioni | Roberto Scipioni | Isomorphism between Non-Riemannian gravity and Einstein-Proca-Weyl
theories extended to a class of Scalar gravity theories | 13 pages, tex file, accepted in Class. Quant. Grav | Class.Quant.Grav. 16 (1999) 2471-2478 | 10.1088/0264-9381/16/7/320 | null | gr-qc math-ph math.MP | null | We extend the recently proved relation between certain models of
Non-Riemannian gravitation and Einstein- Proca-Weyl theories to a class of
Scalar gravity theories. This is used to present a Black-Hole Dilaton solution
with non-Riemannian connection.
| [
{
"created": "Thu, 6 May 1999 21:18:21 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Scipioni",
"Roberto",
""
]
] | We extend the recently proved relation between certain models of Non-Riemannian gravitation and Einstein- Proca-Weyl theories to a class of Scalar gravity theories. This is used to present a Black-Hole Dilaton solution with non-Riemannian connection. |
2307.10986 | Pabitra Tripathy | Pabitra Tripathy, Pritam Nanda, Amit Ghosh | Local first law of black hole | null | Gen Relativ Gravit 56, 54 (2024) | 10.1007/s10714-024-03243-7 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigated the form and implications of the local first law of black
hole thermodynamics in relation to an observer located at a finite distance
from the black hole horizon. Our study is based on the quasilocal form of the
first law for black hole thermodynamics, given by $\delta
E=\frac{\bar{\kappa}}{8\pi}\delta A$, where $\delta E$ and $\delta A$ represent
the changes in the black hole mass and area, respectively, and $\bar{\kappa}$
denotes the quasilocal surface gravity. We show that even at a finite distance,
the quasilocal law still holds. It shows how the first law scales with the
observer's location.
| [
{
"created": "Thu, 20 Jul 2023 16:16:08 GMT",
"version": "v1"
}
] | 2024-05-08 | [
[
"Tripathy",
"Pabitra",
""
],
[
"Nanda",
"Pritam",
""
],
[
"Ghosh",
"Amit",
""
]
] | We investigated the form and implications of the local first law of black hole thermodynamics in relation to an observer located at a finite distance from the black hole horizon. Our study is based on the quasilocal form of the first law for black hole thermodynamics, given by $\delta E=\frac{\bar{\kappa}}{8\pi}\delta A$, where $\delta E$ and $\delta A$ represent the changes in the black hole mass and area, respectively, and $\bar{\kappa}$ denotes the quasilocal surface gravity. We show that even at a finite distance, the quasilocal law still holds. It shows how the first law scales with the observer's location. |
1203.6443 | Manuel Tiglio | Olivier Sarbach and Manuel Tiglio | Continuum and Discrete Initial-Boundary-Value Problems and Einstein's
Field Equations | To appear in Living Reviews in Relativity, 191 pages | null | 10.12942/lrr-2012-9 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many evolution problems in physics are described by partial differential
equations on an infinite domain; therefore, one is interested in the solutions
to such problems for a given initial dataset. A prominent example is the binary
black hole problem within Einstein's theory of gravitation, in which one
computes the gravitational radiation emitted from the inspiral of the two black
holes, merger and ringdown. Powerful mathematical tools can be used to
establish qualitative statements about the solutions, such as their existence,
uniqueness, continuous dependence on the initial data, or their asymptotic
behavior over large time scales. However, one is often interested in computing
the solution itself, and unless the partial differential equation is very
simple, or the initial data possesses a high degree of symmetry, this
computation requires approximation by numerical discretization. When solving
such discrete problems on a machine, one is faced with a finite limit to
computational resources, which leads to the replacement of the infinite
continuum domain with a finite computer grid. This, in turn, leads to a
discrete initial-boundary value problem. The hope is to recover, with high
accuracy, the exact solution in the limit where the grid spacing converges to
zero with the boundary being pushed to infinity.
The goal of this article is to review some of the theory necessary to
understand the continuum and discrete initial-boundary value problems arising
from hyperbolic partial differential equations and to discuss its applications
to numerical relativity; in particular, we present well-posed initial and
initial-boundary value formulations of Einstein's equations, and we discuss
multi-domain high-order finite difference and spectral methods to solve them.
| [
{
"created": "Thu, 29 Mar 2012 06:49:17 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Sarbach",
"Olivier",
""
],
[
"Tiglio",
"Manuel",
""
]
] | Many evolution problems in physics are described by partial differential equations on an infinite domain; therefore, one is interested in the solutions to such problems for a given initial dataset. A prominent example is the binary black hole problem within Einstein's theory of gravitation, in which one computes the gravitational radiation emitted from the inspiral of the two black holes, merger and ringdown. Powerful mathematical tools can be used to establish qualitative statements about the solutions, such as their existence, uniqueness, continuous dependence on the initial data, or their asymptotic behavior over large time scales. However, one is often interested in computing the solution itself, and unless the partial differential equation is very simple, or the initial data possesses a high degree of symmetry, this computation requires approximation by numerical discretization. When solving such discrete problems on a machine, one is faced with a finite limit to computational resources, which leads to the replacement of the infinite continuum domain with a finite computer grid. This, in turn, leads to a discrete initial-boundary value problem. The hope is to recover, with high accuracy, the exact solution in the limit where the grid spacing converges to zero with the boundary being pushed to infinity. The goal of this article is to review some of the theory necessary to understand the continuum and discrete initial-boundary value problems arising from hyperbolic partial differential equations and to discuss its applications to numerical relativity; in particular, we present well-posed initial and initial-boundary value formulations of Einstein's equations, and we discuss multi-domain high-order finite difference and spectral methods to solve them. |
1010.5279 | Leonardo Castaneda | Alejandro Guarnizo, Leonardo Castaneda, Juan M. Tejeiro | Geodesic Deviation Equation in f(R) Gravity | 13 pages, 1 figure. Accepted for publication in General Relativity
and Gravitation | Gen.Rel.Grav.43:2713-2728,2011 | 10.1007/s10714-011-1194-6 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the Geodesic Deviation Equation (GDE) in metric f(R)
gravity. We start giving a brief introduction of the GDE in General Relativity
in the case of the standard cosmology. Next we generalize the GDE for metric
f(R) gravity using again the FLRW metric. A generalization of the Mattig
relation is also obtained. Finally we give and equivalent expression to the
Dyer-Roeder equation in General Relativity in the context of f(R) gravity.
| [
{
"created": "Mon, 25 Oct 2010 22:44:40 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Nov 2010 17:01:41 GMT",
"version": "v2"
},
{
"created": "Tue, 3 May 2011 21:18:08 GMT",
"version": "v3"
}
] | 2011-09-30 | [
[
"Guarnizo",
"Alejandro",
""
],
[
"Castaneda",
"Leonardo",
""
],
[
"Tejeiro",
"Juan M.",
""
]
] | In this paper we study the Geodesic Deviation Equation (GDE) in metric f(R) gravity. We start giving a brief introduction of the GDE in General Relativity in the case of the standard cosmology. Next we generalize the GDE for metric f(R) gravity using again the FLRW metric. A generalization of the Mattig relation is also obtained. Finally we give and equivalent expression to the Dyer-Roeder equation in General Relativity in the context of f(R) gravity. |
gr-qc/9809071 | Coule D. H. | D.H. Coule | Achieving pole-law inflation:the extreme inflation | 12 pages | Phys.Lett. B450 (1999) 48-54 | 10.1016/S0370-2693(99)00143-4 | null | gr-qc | null | The pre-big bang's inflationary mechanism, when allowance is made for the
rapid change of Newton's constant, is not actually of pole-law form . We give
examples where pole-law inflation, which requires violation of the weak-energy
condition, is possible but unlikely due to its very unstable character.
| [
{
"created": "Thu, 24 Sep 1998 16:57:49 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Coule",
"D. H.",
""
]
] | The pre-big bang's inflationary mechanism, when allowance is made for the rapid change of Newton's constant, is not actually of pole-law form . We give examples where pole-law inflation, which requires violation of the weak-energy condition, is possible but unlikely due to its very unstable character. |
2405.19196 | Igor Bogush Dr. | Igor Bogush, Dmitri Gal'tsov, G\'erard Cl\'ement | Mass formulas for supergravity black holes with string singularities | 13 pages, revtex4 | null | null | LAPTH-029/24 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the derivation of mass formulas for stationary axisymmetric
asymptotically locally flat solutions with string singularities on the polar
axis to general supergravity actions containing vector and scalar fields. It is
based on the rod structure of the solutions in Weyl coordinates and is
applicable to black holes with Dirac and Misner strings. The obtained formulas
differ from the corresponding ones in Einstein-Maxwell theory only by summation
over all independent electric charges.
| [
{
"created": "Wed, 29 May 2024 15:37:23 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Bogush",
"Igor",
""
],
[
"Gal'tsov",
"Dmitri",
""
],
[
"Clément",
"Gérard",
""
]
] | We extend the derivation of mass formulas for stationary axisymmetric asymptotically locally flat solutions with string singularities on the polar axis to general supergravity actions containing vector and scalar fields. It is based on the rod structure of the solutions in Weyl coordinates and is applicable to black holes with Dirac and Misner strings. The obtained formulas differ from the corresponding ones in Einstein-Maxwell theory only by summation over all independent electric charges. |
1806.10126 | Sebastien Renaux-Petel | Lucas Pinol, S\'ebastien Renaux-Petel, Yuichiro Tada | Inflationary stochastic anomalies | 9 pages, 2 figures, additional numerical results, version published
as a Letter in Classical and Quantum Gravity | null | 10.1088/1361-6382/ab097f | null | gr-qc astro-ph.CO cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stochastic approach aims at describing the long-wavelength part of
quantum fields during inflation by a classical stochastic theory. It is usually
formulated in terms of Langevin equations, giving rise to a Fokker-Planck
equation for the probability distribution function of the fields, and possibly
their momenta. The link between these two descriptions is ambiguous in general,
as it depends on an implicit discretisation procedure, the two prominent ones
being the It\^o and Stratonovich prescriptions. Here we show that the
requirement of general covariance under field redefinitions is verified only in
the latter case, however at the expense of introducing spurious `frame'
dependences. This stochastic anomaly disappears when there is only one source
of stochasticity, like in slow-roll single-field inflation, but manifests
itself when taking into account the full phase space, or in the presence of
multiple fields. Despite these difficulties, we use physical arguments to write
down a covariant Fokker-Planck equation that describes the diffusion of light
scalar fields in non-linear sigma models in the overdamped limit. We apply it
to test scalar fields in de Sitter space and show that some statistical
properties of a class of two-field models with derivative interactions can be
reproduced by using a correspondence with a single-field model endowed with an
effective potential. We also present explicit results in a simple extension of
the single-field $\lambda \phi^4$ theory to a hyperbolic field space geometry.
The difficulties we describe seem to be the stochastic counterparts of the
notoriously difficult problem of maintaining general covariance in quantum
theories, and the related choices of operator ordering and path-integral
constructions. Our work thus opens new avenues of research at the crossroad
between cosmology, statistical physics, and quantum field theory.
| [
{
"created": "Tue, 26 Jun 2018 17:51:42 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Feb 2019 14:26:47 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Pinol",
"Lucas",
""
],
[
"Renaux-Petel",
"Sébastien",
""
],
[
"Tada",
"Yuichiro",
""
]
] | The stochastic approach aims at describing the long-wavelength part of quantum fields during inflation by a classical stochastic theory. It is usually formulated in terms of Langevin equations, giving rise to a Fokker-Planck equation for the probability distribution function of the fields, and possibly their momenta. The link between these two descriptions is ambiguous in general, as it depends on an implicit discretisation procedure, the two prominent ones being the It\^o and Stratonovich prescriptions. Here we show that the requirement of general covariance under field redefinitions is verified only in the latter case, however at the expense of introducing spurious `frame' dependences. This stochastic anomaly disappears when there is only one source of stochasticity, like in slow-roll single-field inflation, but manifests itself when taking into account the full phase space, or in the presence of multiple fields. Despite these difficulties, we use physical arguments to write down a covariant Fokker-Planck equation that describes the diffusion of light scalar fields in non-linear sigma models in the overdamped limit. We apply it to test scalar fields in de Sitter space and show that some statistical properties of a class of two-field models with derivative interactions can be reproduced by using a correspondence with a single-field model endowed with an effective potential. We also present explicit results in a simple extension of the single-field $\lambda \phi^4$ theory to a hyperbolic field space geometry. The difficulties we describe seem to be the stochastic counterparts of the notoriously difficult problem of maintaining general covariance in quantum theories, and the related choices of operator ordering and path-integral constructions. Our work thus opens new avenues of research at the crossroad between cosmology, statistical physics, and quantum field theory. |
gr-qc/0011030 | Modanese Giovanni | G. Modanese (Univ. of Bolzano and CIPA - Palo Alto) | The dipolar zero-modes of Einstein action: An informal summary with some
new issues | LaTeX, 8 pages. To appear in the proceedings of "Gravitation and
Cosmology: from the Hubble Radius to the Planck Scale. A Symposium in
Celebration of the 80th Birthday of Jean-Pierre Vigier", World Scientific
Editor | In "Gravitation and Cosmology: from the Hubble Radius to the
Planck Scale", edited by R.L. Amoroso, G. Hunter, M. Kafatos, J.-P. Vigier,
p. 259-266 (Kluwer Academic Publishers, Dordrecht, 2002) | null | null | gr-qc | null | We recall the main features of metric vacuum fluctuations which have the
global property int d^4x sqrt{g(x)} R(x) = 0, even though R(x) does not vanish
locally. We stress that these fluctuations could mediate an anomalous coupling
between the gravitational field and coherent matter. Some new issues are
discussed: (1) these fluctuations still imply that <T_{mu nu}(x)>=0; (2) they
are not extrema of the action; (3) for finite duration, their volume in phase
space is not zero; (4) vacuum fluctuations of this kind are not allowed in QED;
(5) their null-action property is a nonperturbative feature; (6) any -real-
pure e.m. field generates zero-modes of this kind, too, up to terms of order
G^2.
| [
{
"created": "Wed, 8 Nov 2000 01:35:04 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Modanese",
"G.",
"",
"Univ. of Bolzano and CIPA - Palo Alto"
]
] | We recall the main features of metric vacuum fluctuations which have the global property int d^4x sqrt{g(x)} R(x) = 0, even though R(x) does not vanish locally. We stress that these fluctuations could mediate an anomalous coupling between the gravitational field and coherent matter. Some new issues are discussed: (1) these fluctuations still imply that <T_{mu nu}(x)>=0; (2) they are not extrema of the action; (3) for finite duration, their volume in phase space is not zero; (4) vacuum fluctuations of this kind are not allowed in QED; (5) their null-action property is a nonperturbative feature; (6) any -real- pure e.m. field generates zero-modes of this kind, too, up to terms of order G^2. |
0711.2198 | Stefano Ansoldi | Stefano Ansoldi, Eduardo I. Guendelman and Idan Shilon | Stability, Singularities and Mass Thresholds in Child Universe
Production: a concise survey including some recent results and prospects | 19 pages LaTeX, including 68 references; to appear in the Proceedings
of "BH2, Dynamics and Thermodynamics of Blackholes and Naked Singularities",
May 10-12 2007, Milano, Italy; conference website:
http://www.mate.polimi.it/bh2 | null | null | KUNS-2109 | gr-qc hep-th | null | We present a review of selected topics concerning the creation and evolution
of child universes, together with a concise account of some recent progress in
the field.
| [
{
"created": "Wed, 14 Nov 2007 13:40:12 GMT",
"version": "v1"
}
] | 2007-12-10 | [
[
"Ansoldi",
"Stefano",
""
],
[
"Guendelman",
"Eduardo I.",
""
],
[
"Shilon",
"Idan",
""
]
] | We present a review of selected topics concerning the creation and evolution of child universes, together with a concise account of some recent progress in the field. |
0710.3108 | Andrew Moylan | Andrew J. Moylan, Susan M. Scott and Antony C. Searle | Functional programming framework for GRworkbench | null | Gen.Rel.Grav.37:1517-1528,2005 | 10.1007/s10714-005-0132-x | null | gr-qc | null | The software tool GRworkbench is an ongoing project in visual, numerical
General Relativity at The Australian National University. Recently, the
numerical differential geometric engine of GRworkbench has been rewritten using
functional programming techniques. By allowing functions to be directly
represented as program variables in C++ code, the functional framework enables
the mathematical formalism of Differential Geometry to be more closely
reflected in GRworkbench . The powerful technique of `automatic
differentiation' has replaced numerical differentiation of the metric
components, resulting in more accurate derivatives and an order-of-magnitude
performance increase for operations relying on differentiation.
| [
{
"created": "Tue, 16 Oct 2007 16:17:17 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Moylan",
"Andrew J.",
""
],
[
"Scott",
"Susan M.",
""
],
[
"Searle",
"Antony C.",
""
]
] | The software tool GRworkbench is an ongoing project in visual, numerical General Relativity at The Australian National University. Recently, the numerical differential geometric engine of GRworkbench has been rewritten using functional programming techniques. By allowing functions to be directly represented as program variables in C++ code, the functional framework enables the mathematical formalism of Differential Geometry to be more closely reflected in GRworkbench . The powerful technique of `automatic differentiation' has replaced numerical differentiation of the metric components, resulting in more accurate derivatives and an order-of-magnitude performance increase for operations relying on differentiation. |
gr-qc/0310099 | Takashi Tamaki | Takashi Tamaki | Black hole solutions coupled to Born-Infeld electrodynamics with
derivative corrections | 5 pages, 5 figures, explanation improved | JCAP0405:004,2004 | 10.1088/1475-7516/2004/05/004 | KUNS-1878 | gr-qc hep-th | null | We investigate black hole solutions in the Einstein-Born-Infeld system. We
clarify the role played by derivative corrections to the Born-Infeld (BI)
action. The qulitative differences from the case without derivative corrections
are: (i) there is no particlelike solution. (ii) the existence of the inner
horizon is restricted to the near extreme solutions. (iii) contribution of the
BI parameter $b$ to the gravitational mass and the Hawking temperature works in
the opposite direction.
| [
{
"created": "Mon, 20 Oct 2003 09:38:05 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Dec 2003 10:10:35 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Mar 2004 04:27:56 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Tamaki",
"Takashi",
""
]
] | We investigate black hole solutions in the Einstein-Born-Infeld system. We clarify the role played by derivative corrections to the Born-Infeld (BI) action. The qulitative differences from the case without derivative corrections are: (i) there is no particlelike solution. (ii) the existence of the inner horizon is restricted to the near extreme solutions. (iii) contribution of the BI parameter $b$ to the gravitational mass and the Hawking temperature works in the opposite direction. |
1105.5927 | Aur\'elien Hees | Aurelien Hees, Peter Wolf, Brahim Lamine, Serge Reynaud, Marc-Thierry
Jaekel, Christophe Le Poncin-Lafitte, Valery Lainey, Andre Fuzfa, Veronique
Dehant | Radioscience simulations in General Relativity and in alternative
theories of gravity | 4 pages; Proceedings of "Les Rencontres de Moriond 2011 - Gravitation
session" | Experimental Gravity and Gravitational Waves, p.259-262 (Th\'e
Gioi, 2011) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this communication, we focus on the possibility to test GR with
radioscience experiments. We present a new software that in a first step
simulates the Range/Doppler signals directly from the space time metric (thus
in GR and in alternative theories of gravity). In a second step, a
least-squares fit of the involved parameters is performed in GR. This software
allows one to get the order of magnitude and the signature of the modifications
induced by an alternative theory of gravity on radioscience signals. As
examples, we present some simulations for the Cassini mission in
Post-Einsteinian gravity and with the MOND External Field Effect.
| [
{
"created": "Mon, 30 May 2011 10:15:05 GMT",
"version": "v1"
}
] | 2014-09-16 | [
[
"Hees",
"Aurelien",
""
],
[
"Wolf",
"Peter",
""
],
[
"Lamine",
"Brahim",
""
],
[
"Reynaud",
"Serge",
""
],
[
"Jaekel",
"Marc-Thierry",
""
],
[
"Poncin-Lafitte",
"Christophe Le",
""
],
[
"Lainey",
"Valery",
""
],
[
"Fuzfa",
"Andre",
""
],
[
"Dehant",
"Veronique",
""
]
] | In this communication, we focus on the possibility to test GR with radioscience experiments. We present a new software that in a first step simulates the Range/Doppler signals directly from the space time metric (thus in GR and in alternative theories of gravity). In a second step, a least-squares fit of the involved parameters is performed in GR. This software allows one to get the order of magnitude and the signature of the modifications induced by an alternative theory of gravity on radioscience signals. As examples, we present some simulations for the Cassini mission in Post-Einsteinian gravity and with the MOND External Field Effect. |
2307.13071 | Betti Hartmann | Yves Brihaye (University of Mons, Belgium) and Betti Hartmann
(Department of Mathematics UCL, UK) | Note on super-critical charged boson stars | v2: results on black holes added | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the transition of charged boson stars from sub- to
super-criticality. This transition is defined as that choice of coupling
constants for which the Coulomb repulsion of two individual bosons (that make
up the star) exactly cancels their gravitational attraction. It was recently
shown that without self-interaction super-critical boson stars are unstable to
decay into their individual constituents. Here we show that this is no longer
true for the self-interacting case and that boson stars can possess spatial
oscillations in the scalar field. We also discuss the corresponding black hole
solutions that carry charged scalar hair.
| [
{
"created": "Mon, 24 Jul 2023 18:51:52 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Sep 2023 12:18:26 GMT",
"version": "v2"
}
] | 2023-09-04 | [
[
"Brihaye",
"Yves",
"",
"University of Mons, Belgium"
],
[
"Hartmann",
"Betti",
"",
"Department of Mathematics UCL, UK"
]
] | We study the transition of charged boson stars from sub- to super-criticality. This transition is defined as that choice of coupling constants for which the Coulomb repulsion of two individual bosons (that make up the star) exactly cancels their gravitational attraction. It was recently shown that without self-interaction super-critical boson stars are unstable to decay into their individual constituents. Here we show that this is no longer true for the self-interacting case and that boson stars can possess spatial oscillations in the scalar field. We also discuss the corresponding black hole solutions that carry charged scalar hair. |
1503.06238 | Sergei Kopeikin | Kopeikin S.M. (University of Missouri, USA) and Han W.-B. (Shanghai
Astronomical Observatory, China) | The Fresnel-Fizeau effect and the atmospheric time delay in geodetic
VLBI | 6 pages, 1 figure, submitted to the Journal of Geodesy | Journal of Geodesy, April 2015, pp. 1-6 | 10.1007/s00190-015-0812-6 | null | gr-qc physics.ao-ph physics.geo-ph physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Fresnel-Fizeau effect is a special relativistic effect that makes the
speed of light dependent on the velocity of a transparent, moving medium. We
present a theoretical formalism for discussing propagation of electromagnetic
signals through the moving Earth atmosphere with taking into account the
Fresnel-Fizeau effect. It provides the rigorous relativistic derivation of the
atmospheric time delay equation in the consensus model of geodetic VLBI
observations which was never published before. The paper confirms the
atmospheric time delay of the consensus VLBI model used in IERS Standards, and
provides a firm theoretical basis for calculation of even more subtle
relativistic corrections.
| [
{
"created": "Fri, 20 Mar 2015 21:56:35 GMT",
"version": "v1"
}
] | 2015-05-15 | [
[
"M.",
"Kopeikin S.",
"",
"University of Missouri, USA"
],
[
"-B.",
"Han W.",
"",
"Shanghai\n Astronomical Observatory, China"
]
] | The Fresnel-Fizeau effect is a special relativistic effect that makes the speed of light dependent on the velocity of a transparent, moving medium. We present a theoretical formalism for discussing propagation of electromagnetic signals through the moving Earth atmosphere with taking into account the Fresnel-Fizeau effect. It provides the rigorous relativistic derivation of the atmospheric time delay equation in the consensus model of geodetic VLBI observations which was never published before. The paper confirms the atmospheric time delay of the consensus VLBI model used in IERS Standards, and provides a firm theoretical basis for calculation of even more subtle relativistic corrections. |
1703.00447 | Vincent Vennin | Julien Grain, Vincent Vennin | Stochastic inflation in phase space: Is slow roll a stochastic
attractor? | Typo corrected in Eq. (3.45) and corrections propagated below,
conclusions unchanged. Changes made after publication | null | 10.1088/1475-7516/2017/05/045 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An appealing feature of inflationary cosmology is the presence of a
phase-space attractor, "slow roll", which washes out the dependence on initial
field velocities. We investigate the robustness of this property under
backreaction from quantum fluctuations using the stochastic inflation formalism
in the phase-space approach. A Hamiltonian formulation of stochastic inflation
is presented, where it is shown that the coarse-graining procedure - where
wavelengths smaller than the Hubble radius are integrated out - preserves the
canonical structure of free fields. This means that different sets of canonical
variables give rise to the same probability distribution which clarifies the
literature with respect to this issue. The role played by the
quantum-to-classical transition is also analysed and is shown to constrain the
coarse-graining scale. In the case of free fields, we find that quantum
diffusion is aligned in phase space with the slow-roll direction. This implies
that the classical slow-roll attractor is immune to stochastic effects and thus
generalises to a stochastic attractor regardless of initial conditions, with a
relaxation time at least as short as in the classical system. For non-test
fields or for test fields with non-linear self interactions however, quantum
diffusion and the classical slow-roll flow are misaligned. We derive a
condition on the coarse-graining scale so that observational corrections from
this misalignment are negligible at leading order in slow roll.
| [
{
"created": "Wed, 1 Mar 2017 17:50:36 GMT",
"version": "v1"
},
{
"created": "Tue, 23 May 2017 06:42:24 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Sep 2017 13:54:09 GMT",
"version": "v3"
},
{
"created": "Fri, 2 Apr 2021 14:26:30 GMT",
"version": "v4"
}
] | 2021-04-05 | [
[
"Grain",
"Julien",
""
],
[
"Vennin",
"Vincent",
""
]
] | An appealing feature of inflationary cosmology is the presence of a phase-space attractor, "slow roll", which washes out the dependence on initial field velocities. We investigate the robustness of this property under backreaction from quantum fluctuations using the stochastic inflation formalism in the phase-space approach. A Hamiltonian formulation of stochastic inflation is presented, where it is shown that the coarse-graining procedure - where wavelengths smaller than the Hubble radius are integrated out - preserves the canonical structure of free fields. This means that different sets of canonical variables give rise to the same probability distribution which clarifies the literature with respect to this issue. The role played by the quantum-to-classical transition is also analysed and is shown to constrain the coarse-graining scale. In the case of free fields, we find that quantum diffusion is aligned in phase space with the slow-roll direction. This implies that the classical slow-roll attractor is immune to stochastic effects and thus generalises to a stochastic attractor regardless of initial conditions, with a relaxation time at least as short as in the classical system. For non-test fields or for test fields with non-linear self interactions however, quantum diffusion and the classical slow-roll flow are misaligned. We derive a condition on the coarse-graining scale so that observational corrections from this misalignment are negligible at leading order in slow roll. |
gr-qc/0309003 | Anzhong Wang | Anzhong Wang | Comment on "Absence of trapped surfaces and singularities in cylindrical
collapse" | latex, 2 figures, the last version to appear in Phys. Rev. D | Phys.Rev.D72:108501,2005 | 10.1103/PhysRevD.72.108501 | null | gr-qc astro-ph hep-th math-ph math.MP | null | Recently, the gravitational collapse of an infinite cylindrical thin shell of
matter in an otherwise empty spacetime with two hypersurface orthogonal Killing
vectors was studied by Gon\c{c}alves [Phys. Rev. {\bf D65}, 084045 (2002).]. By
using three "alternative" criteria for trapped surfaces, the author claimed to
have shown that {\em they can never form either outside or on the shell,
regardingless of the matter content for the shell, except at asymptotical
future null infinite}.
Following Penrose's original idea, we first define trapped surfaces in
cylindrical spacetimes in terms of the expansions of null directions orthogonal
to the surfaces, and then show that the first criterion used by Gon\c{c}alves
is incorrect. We also show that his analysis of non-existence of trapped
surfaces in vacuum is incomplete. To confirm our claim, we present an example
that is a solution to the vacuum Einstein field equations and satisfies all the
regular conditions imposed by Gon\c{c}alves. After extending the solution to
the whole spacetime, we show explicitly that trapped surfaces exist in the
extended region.
| [
{
"created": "Sat, 30 Aug 2003 20:08:25 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Oct 2005 21:29:17 GMT",
"version": "v2"
}
] | 2009-07-07 | [
[
"Wang",
"Anzhong",
""
]
] | Recently, the gravitational collapse of an infinite cylindrical thin shell of matter in an otherwise empty spacetime with two hypersurface orthogonal Killing vectors was studied by Gon\c{c}alves [Phys. Rev. {\bf D65}, 084045 (2002).]. By using three "alternative" criteria for trapped surfaces, the author claimed to have shown that {\em they can never form either outside or on the shell, regardingless of the matter content for the shell, except at asymptotical future null infinite}. Following Penrose's original idea, we first define trapped surfaces in cylindrical spacetimes in terms of the expansions of null directions orthogonal to the surfaces, and then show that the first criterion used by Gon\c{c}alves is incorrect. We also show that his analysis of non-existence of trapped surfaces in vacuum is incomplete. To confirm our claim, we present an example that is a solution to the vacuum Einstein field equations and satisfies all the regular conditions imposed by Gon\c{c}alves. After extending the solution to the whole spacetime, we show explicitly that trapped surfaces exist in the extended region. |
1409.0202 | Katsuki Aoki | Katsuki Aoki and Kei-ichi Maeda | Dark matter in ghost-free bigravity theory: From a galaxy scale to the
universe | 15 pages, 7 figures, minor changes, references added | Phys. Rev. D 90, 124089 (2014) | 10.1103/PhysRevD.90.124089 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the origin of dark matter based on the ghost-free bigravity theory
with twin matter fluids. The present cosmic acceleration can be explained by
the existence of graviton mass, while dark matter is required in several
cosmological situations [the galactic missing mass, the cosmic structure
formation and the standard big-bang scenario (the cosmological nucleosynthesis
vs the CMB observation)]. Assuming that the Compton wavelength of the massive
graviton is shorter than a galactic scale, we show the bigravity theory can
explain dark matter by twin matter fluid as well as the cosmic acceleration by
tuning appropriate coupling constants.
| [
{
"created": "Sun, 31 Aug 2014 10:33:26 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Sep 2014 15:49:44 GMT",
"version": "v2"
}
] | 2015-01-07 | [
[
"Aoki",
"Katsuki",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We study the origin of dark matter based on the ghost-free bigravity theory with twin matter fluids. The present cosmic acceleration can be explained by the existence of graviton mass, while dark matter is required in several cosmological situations [the galactic missing mass, the cosmic structure formation and the standard big-bang scenario (the cosmological nucleosynthesis vs the CMB observation)]. Assuming that the Compton wavelength of the massive graviton is shorter than a galactic scale, we show the bigravity theory can explain dark matter by twin matter fluid as well as the cosmic acceleration by tuning appropriate coupling constants. |
2404.14621 | Hristu Culetu | Hristu Culetu | On geodesics in spherical Rindler space | 7 pages, no figures, references added | null | 10.1142/S0219887824502438 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geodesics in various spherical Rindler frames are investigated. A display
of some kinematical quantities of the spacetime is given. The constant
acceleration from the metric acts as the surface gravity of the horizon $r =
0$. The radial geodesics are computed both for the Balasubramanian et al. form
of the spherical Rindler space and for the non-diagonal metric of Huang and
Sun.
| [
{
"created": "Mon, 22 Apr 2024 23:13:42 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jul 2024 08:31:32 GMT",
"version": "v2"
}
] | 2024-07-04 | [
[
"Culetu",
"Hristu",
""
]
] | The geodesics in various spherical Rindler frames are investigated. A display of some kinematical quantities of the spacetime is given. The constant acceleration from the metric acts as the surface gravity of the horizon $r = 0$. The radial geodesics are computed both for the Balasubramanian et al. form of the spherical Rindler space and for the non-diagonal metric of Huang and Sun. |
1609.07814 | Francisco Jos\'e Maldonado Torralba | J. A. R. Cembranos, J. Gigante Valcarcel, F. J. Maldonado Torralba | Singularities and n-dimensional black holes in torsion theories | 11 pages, 0 figures, minor changes, references added. It matches the
version published in JCAP | JCAP04(2017)021 | 10.1088/1475-7516/2017/04/021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we have studied the singular behaviour of gravitational theories
with non symmetric connections. For this purpose we introduce a new criteria
for the appearance of singularities based on the existence of black/white hole
regions of arbitrary codimension defined inside a spacetime of arbitrary
dimension. We discuss this prescription by increasing the complexity of the
particular torsion theory under study. In this sense, we start with
Teleparallel Gravity, then we analyse Einstein-Cartan theory, and finally
dynamical torsion models.
| [
{
"created": "Sun, 25 Sep 2016 22:30:16 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2017 17:06:06 GMT",
"version": "v2"
}
] | 2017-04-12 | [
[
"Cembranos",
"J. A. R.",
""
],
[
"Valcarcel",
"J. Gigante",
""
],
[
"Torralba",
"F. J. Maldonado",
""
]
] | In this work we have studied the singular behaviour of gravitational theories with non symmetric connections. For this purpose we introduce a new criteria for the appearance of singularities based on the existence of black/white hole regions of arbitrary codimension defined inside a spacetime of arbitrary dimension. We discuss this prescription by increasing the complexity of the particular torsion theory under study. In this sense, we start with Teleparallel Gravity, then we analyse Einstein-Cartan theory, and finally dynamical torsion models. |
1411.6286 | Emanuele Berti | Hector O. Silva, Caio F. B. Macedo, Emanuele Berti, Lu\'is C. B.
Crispino | Slowly Rotating Anisotropic Neutron Stars in General Relativity and
Scalar-Tensor Theory | 19 pages, 7 figures, 1 table. Matches version in press in CQG. Fixed
small typos | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some models (such as the Skyrme model, a low-energy effective field theory
for QCD) suggest that the high-density matter prevailing in neutron star
interiors may be significantly anisotropic. Anisotropy is known to affect the
bulk properties of nonrotating neutron stars in General Relativity. In this
paper we study the effects of anisotropy on slowly rotating stars in General
Relativity. We also consider one of the most popular extensions of Einstein's
theory, namely scalar-tensor theories allowing for spontaneous scalarization (a
phase transition similar to spontaneous magnetization in ferromagnetic
materials). Anisotropy affects the moment of inertia of neutron stars (a
quantity that could potentially be measured in binary pulsar systems) in both
theories. We find that the effects of scalarization increase (decrease) when
the tangential pressure is bigger (smaller) than the radial pressure, and we
present a simple criterion to determine the onset of scalarization by
linearizing the scalar-field equation. Our calculations suggest that binary
pulsar observations may constrain the degree of anisotropy or even, more
optimistically, provide evidence for anisotropy in neutron star cores.
| [
{
"created": "Sun, 23 Nov 2014 19:15:22 GMT",
"version": "v1"
},
{
"created": "Mon, 11 May 2015 18:26:51 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Jun 2015 15:58:35 GMT",
"version": "v3"
}
] | 2015-06-05 | [
[
"Silva",
"Hector O.",
""
],
[
"Macedo",
"Caio F. B.",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Crispino",
"Luís C. B.",
""
]
] | Some models (such as the Skyrme model, a low-energy effective field theory for QCD) suggest that the high-density matter prevailing in neutron star interiors may be significantly anisotropic. Anisotropy is known to affect the bulk properties of nonrotating neutron stars in General Relativity. In this paper we study the effects of anisotropy on slowly rotating stars in General Relativity. We also consider one of the most popular extensions of Einstein's theory, namely scalar-tensor theories allowing for spontaneous scalarization (a phase transition similar to spontaneous magnetization in ferromagnetic materials). Anisotropy affects the moment of inertia of neutron stars (a quantity that could potentially be measured in binary pulsar systems) in both theories. We find that the effects of scalarization increase (decrease) when the tangential pressure is bigger (smaller) than the radial pressure, and we present a simple criterion to determine the onset of scalarization by linearizing the scalar-field equation. Our calculations suggest that binary pulsar observations may constrain the degree of anisotropy or even, more optimistically, provide evidence for anisotropy in neutron star cores. |
1102.3456 | Johan Brannlund | A. Coley, J. Brannlund, J. Latta | Unimodular Gravity and Averaging | 10 pages | null | 10.4236/jmp.2012.33036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The question of the averaging of inhomogeneous spacetimes in cosmology is
important for the correct interpretation of cosmological data. In this paper we
suggest a conceptually simpler approach to averaging in cosmology based on the
averaging of scalars within unimodular gravity. As an illustration, we consider
the example of an exact spherically symmetric dust model, and show that within
this approach averaging introduces correlations (corrections) to the effective
dynamical evolution equation in the form of a spatial curvature term.
| [
{
"created": "Wed, 16 Feb 2011 23:44:45 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Coley",
"A.",
""
],
[
"Brannlund",
"J.",
""
],
[
"Latta",
"J.",
""
]
] | The question of the averaging of inhomogeneous spacetimes in cosmology is important for the correct interpretation of cosmological data. In this paper we suggest a conceptually simpler approach to averaging in cosmology based on the averaging of scalars within unimodular gravity. As an illustration, we consider the example of an exact spherically symmetric dust model, and show that within this approach averaging introduces correlations (corrections) to the effective dynamical evolution equation in the form of a spatial curvature term. |
gr-qc/9903080 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Gravity-wave interferometers as probes of a low-energy effective quantum
gravity | LaTex, 33 pages | Phys.Rev. D62 (2000) 024015 | 10.1103/PhysRevD.62.024015 | CERN-TH/99-70 | gr-qc astro-ph hep-ph hep-th | null | The interferometry-based experimental tests of quantum properties of
space-time which the author sketched out in a recent short Letter [Nature 398
(1999) 216] are here discussed in self-contained fashion. Besides providing
detailed derivations of the results already announced in the previous Letter,
some new results are also derived; in particular, the analysis is extended to a
larger class of scenarios for space-time fuzziness and an absolute bound on the
measurability of the amplitude of a gravity wave is obtained. It is argued that
these studies could be helpful for the search of a theory describing a first
stage of partial unification of Gravity and Quantum Mechanics.
| [
{
"created": "Sat, 20 Mar 1999 23:03:41 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | The interferometry-based experimental tests of quantum properties of space-time which the author sketched out in a recent short Letter [Nature 398 (1999) 216] are here discussed in self-contained fashion. Besides providing detailed derivations of the results already announced in the previous Letter, some new results are also derived; in particular, the analysis is extended to a larger class of scenarios for space-time fuzziness and an absolute bound on the measurability of the amplitude of a gravity wave is obtained. It is argued that these studies could be helpful for the search of a theory describing a first stage of partial unification of Gravity and Quantum Mechanics. |
gr-qc/0602047 | Roman Konoplya | R. A. Konoplya, C. Molina, A. Zhidenko | Late time tails of the massive vector field in a black hole background | one author and new material are added | Phys.Rev.D75:084004,2007 | 10.1103/PhysRevD.75.084004 | null | gr-qc | null | We investigate the late-time behavior of the massive vector field in the
background of the Schwarzschild and Schwarzschild-de Sitter black holes. For
Schwarzschild black hole, at intermediately late times the massive vector field
is represented by three functions with different decay law $\Psi_{0} \sim
t^{-(\ell + 3/2)} \sin{m t}$, $\Psi_{1} \sim t^{-(\ell + 5/2)} \sin{m t}$,
$\Psi_{2} \sim t^{-(\ell + 1/2)} \sin{m t}$, while at asymptotically late times
the decay law $\Psi \sim t^{-5/6} \sin{(m t)}$ is universal, and does not
depend on the multipole number $\ell$. Together with previous study of massive
scalar and Dirac fields where the same asymptotically late-time decay law was
found, it means, that the asymptotically late-time decay law $\sim t^{-5/6}
\sin{(m t)}$ \emph{does not depend} also \emph{on the spin} of the field under
consideration. For Schwarzschild-de Sitter black holes it is observed two
different regimes in the late-time decay of perturbations: non-oscillatory
exponential damping for small values of $m$ and oscillatory quasinormal mode
decay for high enough $m$. Numerical and analytical results are found for these
quasinormal frequencies.
| [
{
"created": "Mon, 13 Feb 2006 19:29:59 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Feb 2007 18:16:56 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Konoplya",
"R. A.",
""
],
[
"Molina",
"C.",
""
],
[
"Zhidenko",
"A.",
""
]
] | We investigate the late-time behavior of the massive vector field in the background of the Schwarzschild and Schwarzschild-de Sitter black holes. For Schwarzschild black hole, at intermediately late times the massive vector field is represented by three functions with different decay law $\Psi_{0} \sim t^{-(\ell + 3/2)} \sin{m t}$, $\Psi_{1} \sim t^{-(\ell + 5/2)} \sin{m t}$, $\Psi_{2} \sim t^{-(\ell + 1/2)} \sin{m t}$, while at asymptotically late times the decay law $\Psi \sim t^{-5/6} \sin{(m t)}$ is universal, and does not depend on the multipole number $\ell$. Together with previous study of massive scalar and Dirac fields where the same asymptotically late-time decay law was found, it means, that the asymptotically late-time decay law $\sim t^{-5/6} \sin{(m t)}$ \emph{does not depend} also \emph{on the spin} of the field under consideration. For Schwarzschild-de Sitter black holes it is observed two different regimes in the late-time decay of perturbations: non-oscillatory exponential damping for small values of $m$ and oscillatory quasinormal mode decay for high enough $m$. Numerical and analytical results are found for these quasinormal frequencies. |
2203.09263 | Roberto Maluf | C. R, Muniz and R. V. Maluf | Generalized Ellis-Bronikov traversable wormholes in $f(R)$ gravity with
anisotropic dark matter | 15 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper studies generalized Ellis-Bronikov (E-B) traversable wormholes in
$f(R)$ extended gravity. We assume that these wormholes are supported by
anisotropic dark matter (DM) according to the most often used phenomenological
models, namely those of Navarro-Frenk-White (NFW), Thomas-Fermi (T-F), and
Pseudo-isothermal (PI). Initially, we obtain the field equations in a general
scenario of $f(R)$ theories in the metric formalism for the static and
spherically symmetric Morris-Thorne spacetime. Then we particularize to a
$f(R)$ model with power-law, including the Starobinky modified gravity.
Following, we analyze the energy conditions which are not dependent on the DM
models (Null and Weak Energy Conditions -- NEC and WEC) and those which are
model-dependent (Strong and Dominant Energy Conditions SEC and DEC). Finally,
we compare some E-B wormhole solutions and the mentioned DM models, discussing
the feasibility of the wormhole-dark matter system in different scenarios.
| [
{
"created": "Thu, 17 Mar 2022 11:32:39 GMT",
"version": "v1"
}
] | 2022-03-18 | [
[
"R",
"C.",
""
],
[
"Muniz",
"",
""
],
[
"Maluf",
"R. V.",
""
]
] | This paper studies generalized Ellis-Bronikov (E-B) traversable wormholes in $f(R)$ extended gravity. We assume that these wormholes are supported by anisotropic dark matter (DM) according to the most often used phenomenological models, namely those of Navarro-Frenk-White (NFW), Thomas-Fermi (T-F), and Pseudo-isothermal (PI). Initially, we obtain the field equations in a general scenario of $f(R)$ theories in the metric formalism for the static and spherically symmetric Morris-Thorne spacetime. Then we particularize to a $f(R)$ model with power-law, including the Starobinky modified gravity. Following, we analyze the energy conditions which are not dependent on the DM models (Null and Weak Energy Conditions -- NEC and WEC) and those which are model-dependent (Strong and Dominant Energy Conditions SEC and DEC). Finally, we compare some E-B wormhole solutions and the mentioned DM models, discussing the feasibility of the wormhole-dark matter system in different scenarios. |
1202.0174 | Alexander Kamenshchik | Alexander Y. Kamenshchik and Serena Manti | Classical and quantum Big Brake cosmology for scalar field and tachyonic
models | final version, to appear in Phys. Rev. D | null | 10.1103/PhysRevD.85.123518 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a relation between the cosmological singularities in classical and
quantum theory, comparing the classical and quantum dynamics in some models
possessing the Big Brake singularity - the model based on a scalar field and
two models based on a tachyon-pseudo-tachyon field . It is shown that the
effect of quantum avoidance is absent for the soft singularities of the Big
Brake type while it is present for the Big Bang and Big Crunch singularities.
Thus, there is some kind of a classical - quantum correspondence, because soft
singularities are traversable in classical cosmology, while the strong Big Bang
and Big Crunch singularities are not traversable.
| [
{
"created": "Wed, 1 Feb 2012 13:56:36 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jun 2012 11:34:30 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Kamenshchik",
"Alexander Y.",
""
],
[
"Manti",
"Serena",
""
]
] | We study a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in some models possessing the Big Brake singularity - the model based on a scalar field and two models based on a tachyon-pseudo-tachyon field . It is shown that the effect of quantum avoidance is absent for the soft singularities of the Big Brake type while it is present for the Big Bang and Big Crunch singularities. Thus, there is some kind of a classical - quantum correspondence, because soft singularities are traversable in classical cosmology, while the strong Big Bang and Big Crunch singularities are not traversable. |
1005.2976 | Massimo Bassan | Giuseppe Pucacco, Massimo Bassan and Massimo Visco | Autonomous perturbations of LISA orbits | 27pages, 20 figures - Accepted for publication on CQG | Class.Quant.Grav.27:235001,2010 | 10.1088/0264-9381/27/23/235001 | null | gr-qc nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate autonomous perturbations on the orbits of LISA, namely the
effects produced by fields that can be expressed only in terms of the position,
but not of time in the Hill frame. This first step in the study of the LISA
orbits has been the subject of recent papers which implement analytical
techniques based on a "post-epicyclic" approximation in the Hill frame to find
optimal unperturbed orbits. The natural step forward is to analyze the
perturbations to purely Keplerian orbits. In the present work a particular
emphasis is put on the tidal field of the Earth assumed to be stationary in the
Hill frame. An accurate interpretation of the global structure of the perturbed
solution sheds light on possible implications on injection in orbit when the
time base-line of the mission is longer than that assumed in previous papers.
Other relevant classes of autonomous perturbations are those given by the
corrections to the Solar field responsible for a slow precession and a global
stationary field, associated to sources like the interplanetary dust or a local
dark matter component. The inclusion of simple linear contributions in the
expansion of these fields produces secular solutions that can be compared with
the measurements and possibly used to evaluate some morphological property of
the perturbing components.
| [
{
"created": "Mon, 17 May 2010 17:05:44 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Sep 2010 18:17:03 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Pucacco",
"Giuseppe",
""
],
[
"Bassan",
"Massimo",
""
],
[
"Visco",
"Massimo",
""
]
] | We investigate autonomous perturbations on the orbits of LISA, namely the effects produced by fields that can be expressed only in terms of the position, but not of time in the Hill frame. This first step in the study of the LISA orbits has been the subject of recent papers which implement analytical techniques based on a "post-epicyclic" approximation in the Hill frame to find optimal unperturbed orbits. The natural step forward is to analyze the perturbations to purely Keplerian orbits. In the present work a particular emphasis is put on the tidal field of the Earth assumed to be stationary in the Hill frame. An accurate interpretation of the global structure of the perturbed solution sheds light on possible implications on injection in orbit when the time base-line of the mission is longer than that assumed in previous papers. Other relevant classes of autonomous perturbations are those given by the corrections to the Solar field responsible for a slow precession and a global stationary field, associated to sources like the interplanetary dust or a local dark matter component. The inclusion of simple linear contributions in the expansion of these fields produces secular solutions that can be compared with the measurements and possibly used to evaluate some morphological property of the perturbing components. |
gr-qc/9711020 | Andreas Aste | G"unter Scharf | Microcanonical Quantum Statistics of Schwarzschild Black Holes | 3 pages, latex | Nuovo Cim. B113 (1998) 821-824 | null | ZU-TH-32/97 | gr-qc | null | It is shown that a quantized Schwarzschild black hole, if described by a
square root energy spectrum with exponential multiplicity, can be treated as a
microcanonical ensemble without problem leading to the expected thermodynamical
properties.
| [
{
"created": "Thu, 6 Nov 1997 13:56:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Scharf",
"G\"unter",
""
]
] | It is shown that a quantized Schwarzschild black hole, if described by a square root energy spectrum with exponential multiplicity, can be treated as a microcanonical ensemble without problem leading to the expected thermodynamical properties. |
1806.11020 | Prado Martin-Moruno | Jose A. R. Cembranos, Mario Coma Diaz, Prado Martin-Moruno | Graviton-photon oscillation in alternative theories of gravity | V1: 5 pages. V2: 9 pages (new style); clarifications in the
discussion included, no physics changes; 3 references added. V3: 10 pages, 4
references added, discussion extended. Version accepted for publication in
Classical and Quantum Gravity | null | 10.1088/1361-6382/aae1d9 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate graviton-photon oscillation in the presence of
an external magnetic field in alternative theories of gravity. Whereas the
effect of an effective refractive index for the electromagnetic radiation was
already considered in the literature, we develop the first approach to take
into account the effect of the modification of the predictions for
gravitational waves in alternative theories of gravity in the phenomenon of
graviton-photon mixing.
| [
{
"created": "Thu, 28 Jun 2018 14:56:44 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jul 2018 05:50:21 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Sep 2018 08:06:57 GMT",
"version": "v3"
}
] | 2018-09-20 | [
[
"Cembranos",
"Jose A. R.",
""
],
[
"Diaz",
"Mario Coma",
""
],
[
"Martin-Moruno",
"Prado",
""
]
] | In this paper we investigate graviton-photon oscillation in the presence of an external magnetic field in alternative theories of gravity. Whereas the effect of an effective refractive index for the electromagnetic radiation was already considered in the literature, we develop the first approach to take into account the effect of the modification of the predictions for gravitational waves in alternative theories of gravity in the phenomenon of graviton-photon mixing. |
1806.02581 | Xing Zhang | Xing Zhang, Wen Zhao, Tan Liu, Kai Lin, Chao Zhang, Shaojun Zhang,
Xiang Zhao, Tao Zhu, Anzhong Wang | Evidence of deviations from general relativity in binary pulsars? | 5 pages, 3 figures, 2 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Testing gravitational theories by binary pulsars nowadays becomes a key
issue. For the general screened modified gravity (SMG), the post-Keplerian
parameters in the neutron star (NS) - white dwarf (WD) binaries differ from
those of general relativity (GR), and the differences are quantified by the
scalar charge $\epsilon_{\scriptscriptstyle\rm WD}$ of WD. After deriving the
constraints on $\epsilon_{\scriptscriptstyle\rm WD}$ from four different NS-WD
binaries, we find that $\epsilon_{\scriptscriptstyle\rm WD}$ is different from
zero at the 2$\sigma$ level in all the cases studied, and there exists an
inverse correlation between masses and scalar charges of low-mass WDs, which is
consistent with the screening mechanisms. In particular, two independent
binaries with measured radii of WDs follow the coincident constraints on the
vacuum expectation value of the scalar field. These self-consistent results
indicate that the observations in NS-WD binary pulsars seem in favor of SMG,
rather than GR.
| [
{
"created": "Thu, 7 Jun 2018 09:31:51 GMT",
"version": "v1"
}
] | 2018-06-08 | [
[
"Zhang",
"Xing",
""
],
[
"Zhao",
"Wen",
""
],
[
"Liu",
"Tan",
""
],
[
"Lin",
"Kai",
""
],
[
"Zhang",
"Chao",
""
],
[
"Zhang",
"Shaojun",
""
],
[
"Zhao",
"Xiang",
""
],
[
"Zhu",
"Tao",
""
],
[
"Wang",
"Anzhong",
""
]
] | Testing gravitational theories by binary pulsars nowadays becomes a key issue. For the general screened modified gravity (SMG), the post-Keplerian parameters in the neutron star (NS) - white dwarf (WD) binaries differ from those of general relativity (GR), and the differences are quantified by the scalar charge $\epsilon_{\scriptscriptstyle\rm WD}$ of WD. After deriving the constraints on $\epsilon_{\scriptscriptstyle\rm WD}$ from four different NS-WD binaries, we find that $\epsilon_{\scriptscriptstyle\rm WD}$ is different from zero at the 2$\sigma$ level in all the cases studied, and there exists an inverse correlation between masses and scalar charges of low-mass WDs, which is consistent with the screening mechanisms. In particular, two independent binaries with measured radii of WDs follow the coincident constraints on the vacuum expectation value of the scalar field. These self-consistent results indicate that the observations in NS-WD binary pulsars seem in favor of SMG, rather than GR. |
1305.3779 | Sante Carloni Dr | Stefano Vignolo, Sante Carloni and Francesco Vietri | Reconstructing exact scalar-tensor cosmologies via conformal
transformations | 8 pages, 2 figures | Phys. Rev. D 88, 023006 (2013) | 10.1103/PhysRevD.88.023006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new reconstruction method for scalar--tensor gravity based on
the use of conformal transformations. The new method allows the derivation of a
set of interesting exact cosmological solutions in brans Dicke gravity as well
as other extensions of General Relativity.
| [
{
"created": "Thu, 16 May 2013 12:27:47 GMT",
"version": "v1"
}
] | 2013-11-26 | [
[
"Vignolo",
"Stefano",
""
],
[
"Carloni",
"Sante",
""
],
[
"Vietri",
"Francesco",
""
]
] | We propose a new reconstruction method for scalar--tensor gravity based on the use of conformal transformations. The new method allows the derivation of a set of interesting exact cosmological solutions in brans Dicke gravity as well as other extensions of General Relativity. |
1511.06963 | Viktor G. Czinner | Viktor G. Czinner and Hideo Iguchi | R\'enyi entropy and the thermodynamic stability of black holes | 6 pages, 6 figures, accepted for publication in Phys. Lett. B | Phys. Lett. B 752 (2016) 306-310 | 10.1016/j.physletb.2015.11.061 | null | gr-qc cond-mat.stat-mech hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thermodynamic stability of black holes, described by the R\'enyi formula as
equilibrium compatible entropy function, is investigated. It is shown that
within this approach, asymptotically flat, Schwarzschild black holes can be in
stable equilibrium with thermal radiation at a fixed temperature. This implies
that the canonical ensemble exists just like in anti-de Sitter space, and
nonextensive effects can stabilize the black holes in a very similar way as it
is done by the gravitational potential of an anti-de Sitter space. Furthermore,
it is also shown that a Hawking-Page-like black hole phase transition occurs at
a critical temperature which depends on the $q$-parameter of the R\'enyi
formula.
| [
{
"created": "Sun, 22 Nov 2015 04:41:44 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"Czinner",
"Viktor G.",
""
],
[
"Iguchi",
"Hideo",
""
]
] | Thermodynamic stability of black holes, described by the R\'enyi formula as equilibrium compatible entropy function, is investigated. It is shown that within this approach, asymptotically flat, Schwarzschild black holes can be in stable equilibrium with thermal radiation at a fixed temperature. This implies that the canonical ensemble exists just like in anti-de Sitter space, and nonextensive effects can stabilize the black holes in a very similar way as it is done by the gravitational potential of an anti-de Sitter space. Furthermore, it is also shown that a Hawking-Page-like black hole phase transition occurs at a critical temperature which depends on the $q$-parameter of the R\'enyi formula. |
gr-qc/0212093 | Antoine Folacci | Yves D\'ecanini, Antoine Folacci, Bruce Jensen | Complex angular momentum in black hole physics and quasinormal modes | 6 pages, 3 figures, revised version | Phys.Rev. D67 (2003) 124017 | 10.1103/PhysRevD.67.124017 | null | gr-qc astro-ph hep-th | null | By using the complex angular momentum approach, we prove that the quasinormal
mode complex frequencies of the Schwarzschild black hole are Breit-Wigner type
resonances generated by a family of surface waves propagating close to the
unstable circular photon (graviton) orbit at $r=3M$. Furthermore, because each
surface wave is associated with a given Regge pole of the $S$-matrix, we can
construct the spectrum of the quasinormal-mode complex frequencies from Regge
trajectories. The notion of surface wave orbiting around black holes thus
appears as a fundamental concept which could be profitably introduced in
various areas of black hole physics in connection with the complex angular
momentum approach.
| [
{
"created": "Mon, 23 Dec 2002 13:25:50 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jun 2003 07:43:12 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Décanini",
"Yves",
""
],
[
"Folacci",
"Antoine",
""
],
[
"Jensen",
"Bruce",
""
]
] | By using the complex angular momentum approach, we prove that the quasinormal mode complex frequencies of the Schwarzschild black hole are Breit-Wigner type resonances generated by a family of surface waves propagating close to the unstable circular photon (graviton) orbit at $r=3M$. Furthermore, because each surface wave is associated with a given Regge pole of the $S$-matrix, we can construct the spectrum of the quasinormal-mode complex frequencies from Regge trajectories. The notion of surface wave orbiting around black holes thus appears as a fundamental concept which could be profitably introduced in various areas of black hole physics in connection with the complex angular momentum approach. |
1004.2406 | Lorenzo Iorio | Lorenzo Iorio | Some Applications of Binary Pulsars to Fundamental Physics | LaTex2e, 21 pages, 1 table, no figures. Invited chapter, to appear
in: Pulsars: Theory, Categories and Applications, Editor: Alexander D.
Morozov, 2010, Nova Science Publishers, ISBN: 978-1-61668-919-3 | A.D. Morozov (ed.) Pulsars: Theory, Categories and Applications,
Nova Science, Hauppauge, 2010, pp. 73-93 | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary systems containing at least one radiopulsar are excellent laboratories
to test several aspects of fundamental physics like matter properties in
conditions of extreme density and theories of gravitation like the Einstein's
General Theory of Gravitation (GTR) along with modifications/extensions of it.
In this Chapter we focus on the perspectives on measuring the moment of inertia
of the double pulsar, its usefulness in testing some modified models of
gravity, and the possibility of using the mean anomaly as a further
post-Keplerian orbital parameter to probe GTR.
| [
{
"created": "Wed, 14 Apr 2010 14:30:41 GMT",
"version": "v1"
}
] | 2010-12-08 | [
[
"Iorio",
"Lorenzo",
""
]
] | Binary systems containing at least one radiopulsar are excellent laboratories to test several aspects of fundamental physics like matter properties in conditions of extreme density and theories of gravitation like the Einstein's General Theory of Gravitation (GTR) along with modifications/extensions of it. In this Chapter we focus on the perspectives on measuring the moment of inertia of the double pulsar, its usefulness in testing some modified models of gravity, and the possibility of using the mean anomaly as a further post-Keplerian orbital parameter to probe GTR. |
1705.05722 | Jorge Pullin | Rodrigo Eyheralde, Miguel Campiglia, Rodolfo Gambini and Jorge Pullin | Quantum fluctuating geometries and the information paradox | 25 pages, 3 figures, removed extra figure in previous version and
made small changes | null | 10.1088/1361-6382/aa8e30 | LSU-REL-051617 | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study Hawking radiation on the quantum space-time of a collapsing null
shell. We use the geometric optics approximation as in Hawking's original
papers to treat the radiation. The quantum space-time is constructed by
superposing the classical geometries associated with collapsing shells with
uncertainty in their position and mass. We show that there are departures from
thermality in the radiation even though we are not considering back reaction.
One recovers the usual profile for the Hawking radiation as a function of
frequency in the limit where the space-time is classical. However, when quantum
corrections are taken into account, the profile of the Hawking radiation as a
function of time contains information about the initial state of the collapsing
shell. More work will be needed to determine if all the information can be
recovered. The calculations show that non-trivial quantum effects can occur in
regions of low curvature when horizons are involved, as for instance advocated
in the firewall scenario.
| [
{
"created": "Tue, 16 May 2017 14:28:04 GMT",
"version": "v1"
},
{
"created": "Thu, 18 May 2017 14:01:23 GMT",
"version": "v2"
},
{
"created": "Mon, 29 May 2017 16:52:15 GMT",
"version": "v3"
},
{
"created": "Wed, 31 May 2017 15:27:50 GMT",
"version": "v4"
}
] | 2017-12-06 | [
[
"Eyheralde",
"Rodrigo",
""
],
[
"Campiglia",
"Miguel",
""
],
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We study Hawking radiation on the quantum space-time of a collapsing null shell. We use the geometric optics approximation as in Hawking's original papers to treat the radiation. The quantum space-time is constructed by superposing the classical geometries associated with collapsing shells with uncertainty in their position and mass. We show that there are departures from thermality in the radiation even though we are not considering back reaction. One recovers the usual profile for the Hawking radiation as a function of frequency in the limit where the space-time is classical. However, when quantum corrections are taken into account, the profile of the Hawking radiation as a function of time contains information about the initial state of the collapsing shell. More work will be needed to determine if all the information can be recovered. The calculations show that non-trivial quantum effects can occur in regions of low curvature when horizons are involved, as for instance advocated in the firewall scenario. |
2111.09694 | Hristu Culetu | Hristu Culetu | On a conformal Schwarzschild-de Sitter spacetime | 11 pages, no figures. Version published in GRG 53:103 (2021) | null | 10.1007/s10714-021-02876-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of the C-metric, we investigate the conformal Schwarzschild -
deSitter spacetime and compute the source stress tensor and study its
properties, including the energy conditions. Then we study its extremal version
($b^{2} = 27m^{2}$, where $b$ is the deS radius and $m$ is the source mass),
when the metric is nonstatic. The weak-field version is analyzed in several
frames, and the metric becomes flat with the special choice $b = 1/a$, $a$
being the constant acceleration of the Schwarzschild-like mass or black hole.
This form is Rindler's geometry in disguise and is also conformal to a de
Sitter metric where the acceleration plays the role of the Hubble constant. In
its time dependent version, one finds that the proper acceleration of a static
observer is constant everywhere, in contrast with the standard Rindler case.
The timelike geodesics along the z-direction are calculated and proves to be
hyperbolae.
| [
{
"created": "Tue, 16 Nov 2021 22:03:43 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Nov 2021 13:50:34 GMT",
"version": "v2"
}
] | 2021-11-24 | [
[
"Culetu",
"Hristu",
""
]
] | On the basis of the C-metric, we investigate the conformal Schwarzschild - deSitter spacetime and compute the source stress tensor and study its properties, including the energy conditions. Then we study its extremal version ($b^{2} = 27m^{2}$, where $b$ is the deS radius and $m$ is the source mass), when the metric is nonstatic. The weak-field version is analyzed in several frames, and the metric becomes flat with the special choice $b = 1/a$, $a$ being the constant acceleration of the Schwarzschild-like mass or black hole. This form is Rindler's geometry in disguise and is also conformal to a de Sitter metric where the acceleration plays the role of the Hubble constant. In its time dependent version, one finds that the proper acceleration of a static observer is constant everywhere, in contrast with the standard Rindler case. The timelike geodesics along the z-direction are calculated and proves to be hyperbolae. |
gr-qc/0409087 | Franz Hinterleitner | Franz Hinterleitner | Canonical DSR | 11 pages | Phys.Rev.D71:025016,2005 | 10.1103/PhysRevD.71.025016 | null | gr-qc | null | For a certain example of a "doubly special relativity theory" the modified
space-time Lorentz transformations are obtained from momentum space
transformations by using canonical methods. In the sequel an energy-momentum
dependent space-time metric is constructed, which is essentially invariant
under the modified Lorentz transformations. By associating such a metric to
every Planck cell in space and the energy-momentum contained in it, a solution
of the problem of macroscopic bodies in doubly special relativity is suggested.
| [
{
"created": "Wed, 22 Sep 2004 12:49:18 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Oct 2004 13:44:42 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Dec 2004 11:34:30 GMT",
"version": "v3"
},
{
"created": "Tue, 1 Feb 2005 11:34:03 GMT",
"version": "v4"
}
] | 2014-11-17 | [
[
"Hinterleitner",
"Franz",
""
]
] | For a certain example of a "doubly special relativity theory" the modified space-time Lorentz transformations are obtained from momentum space transformations by using canonical methods. In the sequel an energy-momentum dependent space-time metric is constructed, which is essentially invariant under the modified Lorentz transformations. By associating such a metric to every Planck cell in space and the energy-momentum contained in it, a solution of the problem of macroscopic bodies in doubly special relativity is suggested. |
1106.4132 | Mew-Bing Wan | Mew-Bing Wan | Universality and properties of neutron star type I critical collapses | 13 pages, 12 figures, 1 new reference added | Class. Quantum Grav. 28 (2011) 155002 | 10.1088/0264-9381/28/15/155002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the neutron star axisymmetric critical solution previously found in
the numerical studies of neutron star mergers. Using neutron star-like initial
data and performing similar merger simulations, we demonstrate that the
solution is indeed a semi-attractor on the threshold plane separating the basin
of a neutron star and the basin of a black hole in the solution space of the
Einstein equations. In order to explore the extent of the attraction basin of
the neutron star semiattractor, we construct initial data phase spaces for
these neutron star-like initial data. From these phase spaces, we also observe
several interesting dynamical scenarios where the merged object is supported
from prompt collapse. The properties of the critical index of the solution, in
particular, its dependence on conserved quantities, are then studied. From the
study, it is found that a family of neutron star semi-attractors exist that can
be classified by both their rest masses and ADM masses.
| [
{
"created": "Tue, 21 Jun 2011 08:35:54 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Sep 2011 07:33:17 GMT",
"version": "v2"
}
] | 2011-09-27 | [
[
"Wan",
"Mew-Bing",
""
]
] | We study the neutron star axisymmetric critical solution previously found in the numerical studies of neutron star mergers. Using neutron star-like initial data and performing similar merger simulations, we demonstrate that the solution is indeed a semi-attractor on the threshold plane separating the basin of a neutron star and the basin of a black hole in the solution space of the Einstein equations. In order to explore the extent of the attraction basin of the neutron star semiattractor, we construct initial data phase spaces for these neutron star-like initial data. From these phase spaces, we also observe several interesting dynamical scenarios where the merged object is supported from prompt collapse. The properties of the critical index of the solution, in particular, its dependence on conserved quantities, are then studied. From the study, it is found that a family of neutron star semi-attractors exist that can be classified by both their rest masses and ADM masses. |
2404.05302 | Frederik Scholtz | L Horoto and F G Scholtz | A New Perspective on Kaluza-Klein Theories | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By assuming that the geometry of spacetime is uniquely determined by the
energy momentum tensor of matter alone, i.e. without any interactions, enables
us to construct the Lagrangian from which the metric of higher dimensional
spacetime follows. From the geodesic equations that follow it becomes clear
that the incorrect mass of elementary particles predicted by Kaluza-Klein
theories arises from the assumption that in the absence of gravity the solution
to the Einstein field equations reduces to the Minkowski metric. From
construction of a consistent theory of $4\mathcal{D}$ electromagnetism, we find
that this assumption does not only result in the incorrect mass of elementary
particles, but also the incorrect value of the cosmological constant. This
suggests that these incorrect predictions, which are often regarded as major
flaws of Kaluza-Klein theories, just reflects the inconsistency of some
postulates of general relativity and gauge theories. Abandoning this assumption
results in modifications of general relativity. We show that the unified
description of fundamental interactions naturally incorporates the Higgs
mechanism. For non-Abelian gauge fields, we find that the manifold comprising
the extra dimensions has to be a group manifold and show that the standard
model is realised in 16$\mathcal{D}$ spacetime. We show that charge and spin
are the same concept, but what makes them different is that the former follows
from symmetry of $4\mathcal{D}$ spacetime while the latter follows from
symmetry of the internal space.
| [
{
"created": "Mon, 8 Apr 2024 08:46:37 GMT",
"version": "v1"
}
] | 2024-04-09 | [
[
"Horoto",
"L",
""
],
[
"Scholtz",
"F G",
""
]
] | By assuming that the geometry of spacetime is uniquely determined by the energy momentum tensor of matter alone, i.e. without any interactions, enables us to construct the Lagrangian from which the metric of higher dimensional spacetime follows. From the geodesic equations that follow it becomes clear that the incorrect mass of elementary particles predicted by Kaluza-Klein theories arises from the assumption that in the absence of gravity the solution to the Einstein field equations reduces to the Minkowski metric. From construction of a consistent theory of $4\mathcal{D}$ electromagnetism, we find that this assumption does not only result in the incorrect mass of elementary particles, but also the incorrect value of the cosmological constant. This suggests that these incorrect predictions, which are often regarded as major flaws of Kaluza-Klein theories, just reflects the inconsistency of some postulates of general relativity and gauge theories. Abandoning this assumption results in modifications of general relativity. We show that the unified description of fundamental interactions naturally incorporates the Higgs mechanism. For non-Abelian gauge fields, we find that the manifold comprising the extra dimensions has to be a group manifold and show that the standard model is realised in 16$\mathcal{D}$ spacetime. We show that charge and spin are the same concept, but what makes them different is that the former follows from symmetry of $4\mathcal{D}$ spacetime while the latter follows from symmetry of the internal space. |
1605.04968 | Mu-Tao Wang | Mu-Tao Wang | Energy, momentum, and center of mass in general relativity | A paper based on the author's talk at the JDG 2014 conference on Sep
13-14, 2014. To be published in Surveys in Differential Geometry, Vol. 21
(2016) | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | These notions in the title are of fundamental importance in any branch of
physics. However, there have been great difficulties in finding physically
acceptable definitions of them in general relativity since Einstein's time. I
shall explain these difficulties and progresses that have been made. In
particular, I shall introduce new definitions of center of mass and angular
momentum at both the quasi-local and total levels, which are derived from first
principles in general relativity and by the method of geometric analysis. With
these new definitions, the classical formula p=mv is shown to be consistent
with Einstein's field equation for the first time. This paper is based on joint
work [14][15] with Po-Ning Chen and Shing-Tung Yau.
| [
{
"created": "Mon, 16 May 2016 22:17:25 GMT",
"version": "v1"
}
] | 2016-05-18 | [
[
"Wang",
"Mu-Tao",
""
]
] | These notions in the title are of fundamental importance in any branch of physics. However, there have been great difficulties in finding physically acceptable definitions of them in general relativity since Einstein's time. I shall explain these difficulties and progresses that have been made. In particular, I shall introduce new definitions of center of mass and angular momentum at both the quasi-local and total levels, which are derived from first principles in general relativity and by the method of geometric analysis. With these new definitions, the classical formula p=mv is shown to be consistent with Einstein's field equation for the first time. This paper is based on joint work [14][15] with Po-Ning Chen and Shing-Tung Yau. |
gr-qc/9709073 | Beverly K. Berger | B.K. Berger, D. Garfinkle, V. Moncrief | Numerical Study of Cosmological Singularities | 20 pages, 5 epsf figures, Latex, uses psfig. Based on talk presented
at Workshop on Black Hole Interiors, Haifa, June 22 - July 3, 1997 | null | null | null | gr-qc | null | The spatially homogeneous, isotropic Standard Cosmological Model appears to
describe our Universe reasonably well. However, Einstein's equations allow a
much larger class of cosmological solutions. Theorems originally due to Penrose
and Hawking predict that all such models (assuming reasonable matter
properties) will have an initial singularity. The nature of this singularity in
generic cosmologies remains a major open question in general relativity.
Spatially homogeneous but possibly anisotropic cosmologies have two types of
singularities: (1) velocity dominated---(reversing the time direction) the
universe evolves to the singularity with fixed anisotropic collapse rates ; (2)
Mixmaster---the anisotropic collapse rates change in a deterministically
chaotic way. Much less is known about spatially inhomogeneous universes.
Belinskii, Khalatnikov, and Lifshitz (BKL) claimed long ago that a generic
universe would evolve toward the singularity as a different Mixmaster universe
at each spatial point. We shall report on the results of a program to test the
BKL conjecture numerically. Results include a new algorithm to evolve
homogeneous Mixmaster models, demonstration of velocity dominance and
understanding of evolution toward velocity dominance in the plane symmetric
Gowdy universes (spatial dependence in one direction), demonstration of
velocity dominance in polarized U(1) symmetric cosmologies (spatial dependence
in two directions), and exploration of departures from velocity dominance in
generic U(1) universes.
| [
{
"created": "Fri, 26 Sep 1997 20:03:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Berger",
"B. K.",
""
],
[
"Garfinkle",
"D.",
""
],
[
"Moncrief",
"V.",
""
]
] | The spatially homogeneous, isotropic Standard Cosmological Model appears to describe our Universe reasonably well. However, Einstein's equations allow a much larger class of cosmological solutions. Theorems originally due to Penrose and Hawking predict that all such models (assuming reasonable matter properties) will have an initial singularity. The nature of this singularity in generic cosmologies remains a major open question in general relativity. Spatially homogeneous but possibly anisotropic cosmologies have two types of singularities: (1) velocity dominated---(reversing the time direction) the universe evolves to the singularity with fixed anisotropic collapse rates ; (2) Mixmaster---the anisotropic collapse rates change in a deterministically chaotic way. Much less is known about spatially inhomogeneous universes. Belinskii, Khalatnikov, and Lifshitz (BKL) claimed long ago that a generic universe would evolve toward the singularity as a different Mixmaster universe at each spatial point. We shall report on the results of a program to test the BKL conjecture numerically. Results include a new algorithm to evolve homogeneous Mixmaster models, demonstration of velocity dominance and understanding of evolution toward velocity dominance in the plane symmetric Gowdy universes (spatial dependence in one direction), demonstration of velocity dominance in polarized U(1) symmetric cosmologies (spatial dependence in two directions), and exploration of departures from velocity dominance in generic U(1) universes. |
1401.3480 | Saneesh Sebastian | Saneesh Sebastian and V. C. Kuriakose | Scattering of Scalar Field by an Extended Black Hole in F(R) gravity | 9 page, no figures, To appear in MPLA | null | 10.1142/S0217732314500059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we have studied the scattering of scalar field around an
extended black hole in F(R) gravity using WKB method. We have obtained the wave
function in different regions such as near the horizon region, away from
horizon and far away from horizon and the absorption cross section are
calculated. We find that the absorption cross section is inversely proportional
to the cube of Hawking temperature. We have also evaluated the Hawking
temperature of the black hole via tunneling method.
| [
{
"created": "Wed, 15 Jan 2014 05:34:29 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Sebastian",
"Saneesh",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | In this work we have studied the scattering of scalar field around an extended black hole in F(R) gravity using WKB method. We have obtained the wave function in different regions such as near the horizon region, away from horizon and far away from horizon and the absorption cross section are calculated. We find that the absorption cross section is inversely proportional to the cube of Hawking temperature. We have also evaluated the Hawking temperature of the black hole via tunneling method. |
0912.1317 | Adellane Sousa | A. A. Sousa, D. M. Oliveira and R. B. Pereira | Space-time Torsion and Neutrino Oscillations in Vacuum | 07 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The objective of this study is to verify the consistency of the prescription
of alternative minimum coupling (connection) proposed by the Teleparallel
Equivalent to General Relativity (TEGR) for the Dirac equation. With this aim,
we studied the problem of neutrino oscillations in Weitzenbock space-time in
the Schwarzschild metric. In particular, we calculate the phase dynamics of
neutrinos. The relation of spin of the neutrino with the space-time torsion is
clarified through the determination of the phase differences between spin
eigenstates of the neutrinos.
| [
{
"created": "Mon, 7 Dec 2009 19:31:08 GMT",
"version": "v1"
}
] | 2009-12-22 | [
[
"Sousa",
"A. A.",
""
],
[
"Oliveira",
"D. M.",
""
],
[
"Pereira",
"R. B.",
""
]
] | The objective of this study is to verify the consistency of the prescription of alternative minimum coupling (connection) proposed by the Teleparallel Equivalent to General Relativity (TEGR) for the Dirac equation. With this aim, we studied the problem of neutrino oscillations in Weitzenbock space-time in the Schwarzschild metric. In particular, we calculate the phase dynamics of neutrinos. The relation of spin of the neutrino with the space-time torsion is clarified through the determination of the phase differences between spin eigenstates of the neutrinos. |
1511.07775 | Angus Prain | Valerio Faraoni and Angus Prain | Understanding dynamical black hole apparent horizons | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical, non-asymptotically flat black holes are best characterized by
their apparent horizons. Cosmological black hole solutions of General
Relativity exhibit two types of apparent horizon behaviours which, thus far,
appeared to be completely disconnected. By taking the limit to General
Relativity of a class of Brans-Dicke spacetimes, it is shown how one of these
two behaviours is really a limit of the other.
| [
{
"created": "Tue, 24 Nov 2015 16:09:11 GMT",
"version": "v1"
}
] | 2015-11-25 | [
[
"Faraoni",
"Valerio",
""
],
[
"Prain",
"Angus",
""
]
] | Dynamical, non-asymptotically flat black holes are best characterized by their apparent horizons. Cosmological black hole solutions of General Relativity exhibit two types of apparent horizon behaviours which, thus far, appeared to be completely disconnected. By taking the limit to General Relativity of a class of Brans-Dicke spacetimes, it is shown how one of these two behaviours is really a limit of the other. |
2010.13730 | Stefano Foffa | Stefano Foffa, Riccardo Sturani, William J. Torres Bobadilla | Efficient resummation of high post-Newtonian contributions to the
binding energy | 17 pages, 3 figures. In v3: Section 2 expanded. Published on JHEP | null | 10.1007/JHEP02(2021)165 | IFIC/20-45; MPP-2020-191 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A factorisation property of Feynman diagrams in the context the Effective
Field Theory approach to the compact binary problem has been recently employed
to efficiently determine the static sector of the potential at fifth
post-Newtonian (5PN) order. We extend this procedure to the case of non-static
diagrams and we use it to fix, by means of elementary algebraic manipulations,
the value of more than one thousand diagrams at 5PN order, that is a
substantial fraction of the diagrams needed to fully determine the dynamics at
5PN. This procedure addresses the redundancy problem that plagues the
computation of the binding energy with respect to more "efficient" observables
like the scattering angle, thus making the EFT approach in harmonic gauge at
least as scalable as the others methods.
| [
{
"created": "Mon, 26 Oct 2020 17:14:49 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Nov 2020 14:17:59 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Feb 2021 16:06:45 GMT",
"version": "v3"
}
] | 2021-03-17 | [
[
"Foffa",
"Stefano",
""
],
[
"Sturani",
"Riccardo",
""
],
[
"Bobadilla",
"William J. Torres",
""
]
] | A factorisation property of Feynman diagrams in the context the Effective Field Theory approach to the compact binary problem has been recently employed to efficiently determine the static sector of the potential at fifth post-Newtonian (5PN) order. We extend this procedure to the case of non-static diagrams and we use it to fix, by means of elementary algebraic manipulations, the value of more than one thousand diagrams at 5PN order, that is a substantial fraction of the diagrams needed to fully determine the dynamics at 5PN. This procedure addresses the redundancy problem that plagues the computation of the binding energy with respect to more "efficient" observables like the scattering angle, thus making the EFT approach in harmonic gauge at least as scalable as the others methods. |
gr-qc/0109059 | Christodoulakis Theodosios | T. Christodoulakis | Lectures on Quantum Cosmology | 34 pages, LaTeX2e, No figures | Lect.Notes Phys.592:318-350,2002 | null | null | gr-qc | null | The problems encountered in trying to quantize the various cosmological
models, are brought forward by means of a concrete example. The Automorphism
groups are revealed as the key element through which G.C.T.'s can be used for a
general treatment of these problems. At the classical level, the time dependent
automorphisms lead to significant simplifications of the line element for the
generic spatially homogeneous geometry, without loss of generality. At the
quantum level, the ''frozen'' automorphisms entail an important reduction of
the configuration space --spanned by the 6 components of the scale factor
matrix-- on which the Wheeler-DeWitt equation, is to be based. In this spirit
the canonical quantization of the most general minisuperspace actions --i.e.
with all six scale factor as well as the lapse function and the shift vector
present-- describing the vacuum type II, I geometries, is considered. The
reduction to the corresponding physical degrees of freedom is achieved through
the usage of the linear constraints as well as the quantum version of the
entire set of all classical integrals of motion.
| [
{
"created": "Tue, 18 Sep 2001 09:39:16 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Christodoulakis",
"T.",
""
]
] | The problems encountered in trying to quantize the various cosmological models, are brought forward by means of a concrete example. The Automorphism groups are revealed as the key element through which G.C.T.'s can be used for a general treatment of these problems. At the classical level, the time dependent automorphisms lead to significant simplifications of the line element for the generic spatially homogeneous geometry, without loss of generality. At the quantum level, the ''frozen'' automorphisms entail an important reduction of the configuration space --spanned by the 6 components of the scale factor matrix-- on which the Wheeler-DeWitt equation, is to be based. In this spirit the canonical quantization of the most general minisuperspace actions --i.e. with all six scale factor as well as the lapse function and the shift vector present-- describing the vacuum type II, I geometries, is considered. The reduction to the corresponding physical degrees of freedom is achieved through the usage of the linear constraints as well as the quantum version of the entire set of all classical integrals of motion. |
2404.10309 | Saheb Soroushfar | Saheb Soroushfar, Hoda Farahani, and Sudhaker Upadhyay | Non-perturbative correction to thermodynamics of conformally dressed 3D
black hole | 13 pages, 5 figures | Physics of the Dark Universe 42 (2023) 101272 | 10.1016/j.dark.2023.101272 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We extend the study of corrected thermodynamics for the 3D black holes
conformally coupled to scalar field up to non-perturbative level. We calculate
the exponential correction to entropy arises due to the microstate counting for
quantum states on the boundary. This exponential correction in entropy
attributes to the other thermodynamical quantities also. We study the stability
and phase transition for this system of black hole under the influence of
non-perturbative correction. We also discuss the quantum work associated with
exponential corrected entropy. Finally, we justify the results from the view
point of thermodynamic geometry.
| [
{
"created": "Tue, 16 Apr 2024 06:34:49 GMT",
"version": "v1"
}
] | 2024-04-17 | [
[
"Soroushfar",
"Saheb",
""
],
[
"Farahani",
"Hoda",
""
],
[
"Upadhyay",
"Sudhaker",
""
]
] | We extend the study of corrected thermodynamics for the 3D black holes conformally coupled to scalar field up to non-perturbative level. We calculate the exponential correction to entropy arises due to the microstate counting for quantum states on the boundary. This exponential correction in entropy attributes to the other thermodynamical quantities also. We study the stability and phase transition for this system of black hole under the influence of non-perturbative correction. We also discuss the quantum work associated with exponential corrected entropy. Finally, we justify the results from the view point of thermodynamic geometry. |
2301.00682 | Hossein Ghaffarnejad | Hossein Ghaffarnejad, Tohid Ghorbani and Firoozeh Eidizadeh | On the stability of electrostatics stars with modified non-gauge
invariant Einstein-Maxwell gravity | 23 pages, 2 figure | General Relativity and Gravitation 2023 | 10.1007/s10714-023-03183-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a modified Einstein-Maxwell gravity to study stability of an
electrostatic spherical star. Correction terms in this model are scalers which
are made from contraction of Ricci tensor and electromagnetic vector potential.
Our motivation to use this kind of exotic EM gravity is inevitable influence of
cosmic magnetic field in inflation of the universe which is observed now but
its intensity suppresses in the usual gauge invariant EM gravity. In this work
we use dynamical systems approach to obtain stability conditions of such a star
and investigation of affects of interaction parts of the model on the
stability.
| [
{
"created": "Tue, 27 Dec 2022 21:18:23 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Aug 2023 22:10:39 GMT",
"version": "v2"
}
] | 2023-12-05 | [
[
"Ghaffarnejad",
"Hossein",
""
],
[
"Ghorbani",
"Tohid",
""
],
[
"Eidizadeh",
"Firoozeh",
""
]
] | We use a modified Einstein-Maxwell gravity to study stability of an electrostatic spherical star. Correction terms in this model are scalers which are made from contraction of Ricci tensor and electromagnetic vector potential. Our motivation to use this kind of exotic EM gravity is inevitable influence of cosmic magnetic field in inflation of the universe which is observed now but its intensity suppresses in the usual gauge invariant EM gravity. In this work we use dynamical systems approach to obtain stability conditions of such a star and investigation of affects of interaction parts of the model on the stability. |
1108.5086 | Gil Jannes | G. Jannes and G. E. Volovik | The cosmological constant: A lesson from the effective gravity of
topological Weyl media | 7 pages, no figures | JETP Lett.96:215-221, 2012 (Pisma Zh.Eksp.Teor.Fiz.96:231-237,
2012) | 10.1134/S0021364012160035 | null | gr-qc cond-mat.other hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Topological matter with Weyl points, such as superfluid 3He-A, provide an
explicit example where there is a direct connection between the properly
determined vacuum energy and the cosmological constant of the effective gravity
emerging in condensed matter. This is in contrast to the acoustic gravity
emerging in Bose-Einstein condensates, where the "value of this constant cannot
be easily predicted by just looking at the ground state energy of the
microscopic system from which spacetime and its dynamics should emerge" (S.
Finazzi, S. Liberati and L. Sindoni, The cosmological constant: a lesson from
Bose-Einstein condensates, Phys. Rev. Lett. 108, 071101 (2012)). The advantage
of topological matter is that the relativistic fermions and gauge bosons
emerging near the Weyl point obey the same effective metric and thus the
effective gravity is more closely related to real gravity. We study this
connection in the bi-metric gravity emerging in 3He-A, and its relation to the
graviton masses, by comparison with a fully relativistic bi-metric theory of
gravity. This shows that the parameter \lambda, which in 3He-A is the bi-metric
generalization of the cosmological constant, coincides with the difference in
the proper energy of the vacuum in two states (the nonequilibrium state without
gravity and the equilibrium state in which gravity emerges) and is on the order
of the characteristic Planck energy scale of the system. Although the
cosmological constant \lambda\ is huge, the cosmological term itself is
naturally non-constant and vanishes in the equilibrium vacuum, as dictated by
thermodynamics. This suggests that the equilibrium state of any system
including the final state of the Universe is not gravitating.
| [
{
"created": "Thu, 25 Aug 2011 13:40:50 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Aug 2011 16:14:37 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Nov 2011 10:19:35 GMT",
"version": "v3"
},
{
"created": "Mon, 19 Dec 2011 10:47:10 GMT",
"version": "v4"
},
{
"created": "Sun, 25 Dec 2011 19:41:09 GMT",
"version": "v5"
},
{
"created": "Fri, 17 Feb 2012 12:12:31 GMT",
"version": "v6"
},
{
"created": "Thu, 8 Mar 2012 13:51:12 GMT",
"version": "v7"
},
{
"created": "Fri, 25 May 2012 12:58:10 GMT",
"version": "v8"
}
] | 2013-02-18 | [
[
"Jannes",
"G.",
""
],
[
"Volovik",
"G. E.",
""
]
] | Topological matter with Weyl points, such as superfluid 3He-A, provide an explicit example where there is a direct connection between the properly determined vacuum energy and the cosmological constant of the effective gravity emerging in condensed matter. This is in contrast to the acoustic gravity emerging in Bose-Einstein condensates, where the "value of this constant cannot be easily predicted by just looking at the ground state energy of the microscopic system from which spacetime and its dynamics should emerge" (S. Finazzi, S. Liberati and L. Sindoni, The cosmological constant: a lesson from Bose-Einstein condensates, Phys. Rev. Lett. 108, 071101 (2012)). The advantage of topological matter is that the relativistic fermions and gauge bosons emerging near the Weyl point obey the same effective metric and thus the effective gravity is more closely related to real gravity. We study this connection in the bi-metric gravity emerging in 3He-A, and its relation to the graviton masses, by comparison with a fully relativistic bi-metric theory of gravity. This shows that the parameter \lambda, which in 3He-A is the bi-metric generalization of the cosmological constant, coincides with the difference in the proper energy of the vacuum in two states (the nonequilibrium state without gravity and the equilibrium state in which gravity emerges) and is on the order of the characteristic Planck energy scale of the system. Although the cosmological constant \lambda\ is huge, the cosmological term itself is naturally non-constant and vanishes in the equilibrium vacuum, as dictated by thermodynamics. This suggests that the equilibrium state of any system including the final state of the Universe is not gravitating. |
2306.10467 | Xiao-Mei Kuang | Meng-He Wu, Hong Guo, Xiao-Mei Kuang | Precession and Lense-Thirring effect of hairy Kerr spacetimes | 18 pages,12 figures, published on 17 March 2023 | PHYS. REV. D 107, 064033 (2023) | 10.1103/PhysRevD.107.064033 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the frame-dragging effect of the hairy Kerr spacetimes on the
spin of a test gyro and accretion disk. Firstly, we analyze Lense-Thirring (LT)
precession frequency, geodetic precession frequency, and the general spin
precession frequency of a test gyro attached to a stationary observer in the
spacetime. We find that the black hole hair suppresses those precession
frequencies in comparison with that occurs in Kerr spacetime in general
relativity. Moreover, using those frequencies as probe, we differentiate the
hairy Kerr black hole (BH) from naked singularity (NS). Specifically, as the
observer approaches the central source along any direction, the frequencies
grow sharply for the hairy Kerr BH, while for the hairy NS they are finite
except at the ring singularity. Then, we investigate the quasiperiodic
oscillations (QPOs) phenomena as the accretion disk approaches the hairy Kerr
BH or NS. To this end, we analyze the bound circular orbits and their
perturbations. We find that as the orbits approach the corresponding inner-most
stable circular orbit (ISCO), both LT precession frequency and periastron
precession frequency behave differently in the hairy Kerr BH and NS.
Additionally, the hairy parameters have significant effects on the two
frequencies. We expect that our theoretical studies could shed light on
astrophysical observations in distinguishing hairy theories from Einstein's
gravity, and also in distinguishing BH from NS in spacetime with hair.
| [
{
"created": "Sun, 18 Jun 2023 03:34:24 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Wu",
"Meng-He",
""
],
[
"Guo",
"Hong",
""
],
[
"Kuang",
"Xiao-Mei",
""
]
] | We investigate the frame-dragging effect of the hairy Kerr spacetimes on the spin of a test gyro and accretion disk. Firstly, we analyze Lense-Thirring (LT) precession frequency, geodetic precession frequency, and the general spin precession frequency of a test gyro attached to a stationary observer in the spacetime. We find that the black hole hair suppresses those precession frequencies in comparison with that occurs in Kerr spacetime in general relativity. Moreover, using those frequencies as probe, we differentiate the hairy Kerr black hole (BH) from naked singularity (NS). Specifically, as the observer approaches the central source along any direction, the frequencies grow sharply for the hairy Kerr BH, while for the hairy NS they are finite except at the ring singularity. Then, we investigate the quasiperiodic oscillations (QPOs) phenomena as the accretion disk approaches the hairy Kerr BH or NS. To this end, we analyze the bound circular orbits and their perturbations. We find that as the orbits approach the corresponding inner-most stable circular orbit (ISCO), both LT precession frequency and periastron precession frequency behave differently in the hairy Kerr BH and NS. Additionally, the hairy parameters have significant effects on the two frequencies. We expect that our theoretical studies could shed light on astrophysical observations in distinguishing hairy theories from Einstein's gravity, and also in distinguishing BH from NS in spacetime with hair. |
2210.10383 | Bahtiyar \"Ozg\"ur Sar{\i}o\u{g}lu | Ulf Lindstr\"om and \"Ozg\"ur Sar{\i}o\u{g}lu | Gravitational duality, Palatini variation and boundary terms: A synopsis | 15 pages, one figure; Ver. 2: 16 pages, one figure, various
clarifying remarks added, accepted for publication in CQG | Class. Quantum Grav. 40 (2023) 085003 | 10.1088/1361-6382/acc22f | Theoretical Physics Uppsala University preprint UUITP-43/22 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider $f(R)$ gravity and Born-Infeld-Einstein (BIE) gravity in
formulations where the metric and connection are treated independently and
integrate out the metric to find the corresponding models solely in terms of
the connection, the archetypical treatment being that of
Eddington-Schr\"odinger (ES) duality between cosmological Einstein and
Eddington theories. For dimensions $D\ne2$, we find that this requires $f(R)$
to have a specific form which makes the model Weyl invariant, and that its
Eddington reduction is then equivalent to that of BIE with certain parameters.
For $D=2$ dimensions, where ES duality is not applicable, we find that both
models are Weyl invariant and equivalent to a first order formulation of the
bosonic string. We also discuss the form of the boundary terms needed for the
variational principle to be well defined on manifolds with non-null boundaries.
This requires a modification of the Gibbons-Hawking-York (GHY) boundary term
for gravity. This modification also means that the dualities between metric and
connection formulations are consistent and include the boundary terms.
| [
{
"created": "Wed, 19 Oct 2022 08:51:57 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Mar 2023 11:36:29 GMT",
"version": "v2"
}
] | 2023-03-20 | [
[
"Lindström",
"Ulf",
""
],
[
"Sarıoğlu",
"Özgür",
""
]
] | We consider $f(R)$ gravity and Born-Infeld-Einstein (BIE) gravity in formulations where the metric and connection are treated independently and integrate out the metric to find the corresponding models solely in terms of the connection, the archetypical treatment being that of Eddington-Schr\"odinger (ES) duality between cosmological Einstein and Eddington theories. For dimensions $D\ne2$, we find that this requires $f(R)$ to have a specific form which makes the model Weyl invariant, and that its Eddington reduction is then equivalent to that of BIE with certain parameters. For $D=2$ dimensions, where ES duality is not applicable, we find that both models are Weyl invariant and equivalent to a first order formulation of the bosonic string. We also discuss the form of the boundary terms needed for the variational principle to be well defined on manifolds with non-null boundaries. This requires a modification of the Gibbons-Hawking-York (GHY) boundary term for gravity. This modification also means that the dualities between metric and connection formulations are consistent and include the boundary terms. |
2406.09526 | Diego S\'aez-Chill\'on G\'omez | Gerardo Mora-P\'erez, Gonzalo J. Olmo, Diego Rubiera-Garcia and Diego
S\'aez-Chill\'on G\'omez | Boundary terms and on-shell action in Ricci-based gravity theories: the
Hamiltonian formulation | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering the so-called Ricci-based gravity theories, a family of
extensions of General Relativity whose action is given by a non-linear function
of contractions and products of the (symmetric part of the) Ricci tensor of an
independent connection, the Hamiltonian formulation of the theory is obtained.
To do so, the independent connection is decomposed in two parts, one compatible
with a metric tensor and the other one given by a 3-rank tensor. Subsequently,
the Riemann tensor is expressed in terms of its projected components onto a
hypersurface, allowing to construct the $3+1$ decomposition of the theory and
the corresponding Gauss-Codazzi relations, where the boundary terms naturally
arise in the gravitational action. Finally, the ADM decomposition is followed
in order to construct the corresponding Hamiltonian and the ADM energy for any
Ricci-based gravity theory. The formalism is applied to the simple case of
Schwarzschild space-time.
| [
{
"created": "Thu, 13 Jun 2024 18:31:14 GMT",
"version": "v1"
}
] | 2024-06-17 | [
[
"Mora-Pérez",
"Gerardo",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
],
[
"Gómez",
"Diego Sáez-Chillón",
""
]
] | Considering the so-called Ricci-based gravity theories, a family of extensions of General Relativity whose action is given by a non-linear function of contractions and products of the (symmetric part of the) Ricci tensor of an independent connection, the Hamiltonian formulation of the theory is obtained. To do so, the independent connection is decomposed in two parts, one compatible with a metric tensor and the other one given by a 3-rank tensor. Subsequently, the Riemann tensor is expressed in terms of its projected components onto a hypersurface, allowing to construct the $3+1$ decomposition of the theory and the corresponding Gauss-Codazzi relations, where the boundary terms naturally arise in the gravitational action. Finally, the ADM decomposition is followed in order to construct the corresponding Hamiltonian and the ADM energy for any Ricci-based gravity theory. The formalism is applied to the simple case of Schwarzschild space-time. |
2004.11266 | Ayan Chatterjee | Ayan Chatterjee, Amit Ghosh and Suresh Jaryal | Marginally Trapped Surfaces in Spherical Gravitational Collapse | 50 pages, 16 figures, typos corrected, references added | Phys. Rev. D 102, 064048 (2020) | 10.1103/PhysRevD.102.064048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper deals with a detail study of gravitational collapse of dust and
viscous fluids under the assumptions of spherical symmetry. Our main goal is to
closely analyze the horizons which arise during this gravitational phenomenon.
To this end, we examine the formation and evolution of trapped surfaces in
these spacetimes, with special attention to trapped regions and cylinders
foliated by marginally trapped surfaces. The time evolution of trapped
surfaces, collapsing shell as well as the event horizon are identified
analytically as well as numerically. Using different density profiles of
matter, we analyze, how the nature of the marginally trapped surfaces modify as
we change the energy momentum tensor. These studies reveal that depending on
the mass function and the mass profile, it is possible to envisage situations
where dynamical horizons, timelike tubes or isolated horizons may arise.
| [
{
"created": "Thu, 23 Apr 2020 15:51:56 GMT",
"version": "v1"
},
{
"created": "Tue, 12 May 2020 15:31:31 GMT",
"version": "v2"
}
] | 2020-09-23 | [
[
"Chatterjee",
"Ayan",
""
],
[
"Ghosh",
"Amit",
""
],
[
"Jaryal",
"Suresh",
""
]
] | This paper deals with a detail study of gravitational collapse of dust and viscous fluids under the assumptions of spherical symmetry. Our main goal is to closely analyze the horizons which arise during this gravitational phenomenon. To this end, we examine the formation and evolution of trapped surfaces in these spacetimes, with special attention to trapped regions and cylinders foliated by marginally trapped surfaces. The time evolution of trapped surfaces, collapsing shell as well as the event horizon are identified analytically as well as numerically. Using different density profiles of matter, we analyze, how the nature of the marginally trapped surfaces modify as we change the energy momentum tensor. These studies reveal that depending on the mass function and the mass profile, it is possible to envisage situations where dynamical horizons, timelike tubes or isolated horizons may arise. |
1411.7553 | Francesco Caravelli | Leonardo Banchi, Francesco Caravelli | Geometric phases and cyclic isotropic cosmologies | 13 pages, 10 figures; new LQC analysis and citations added, text
improved, typos corrected | Classical and Quantum Gravity 10, Vol 33 (2016) | 10.1088/0264-9381/33/10/105003 | null | gr-qc cond-mat.other hep-th quant-ph | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In the present paper we study the evolution of the modes of a scalar field in
a cyclic cosmology. In order to keep the discussion clear, we study the
features of a scalar field in a toy model, a Friedman-Robertson-Walker universe
with a periodic scale factor, in which the universe expands, contracts and
bounces infinite times, in the approximation in which the dynamic features of
this universe are driven by some external factor, without the backreaction of
the scalar field under study. In particular, we show that particle production
exhibits features of the cyclic cosmology. Also, by studying the Berry phase of
the scalar field, we show that contrarily to what is commonly believed, the
scalar field carries information from one bounce to another in the form of a
global phase which occurs to be generically non-zero. {The Berry phase is then
evaluated numerically in the case of the effective Loop Quantum Cosmology
closed Universe. We observe that Berry's phase is nonzero, but that in the
quantum regime the particle content is non-negligible.
| [
{
"created": "Thu, 27 Nov 2014 11:23:03 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Dec 2014 10:01:43 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Dec 2014 15:36:27 GMT",
"version": "v3"
},
{
"created": "Mon, 27 Apr 2015 10:13:09 GMT",
"version": "v4"
},
{
"created": "Tue, 26 Jan 2016 12:37:05 GMT",
"version": "v5"
},
{
"created": "Wed, 20 Apr 2016 08:34:04 GMT",
"version": "v6"
}
] | 2017-03-15 | [
[
"Banchi",
"Leonardo",
""
],
[
"Caravelli",
"Francesco",
""
]
] | In the present paper we study the evolution of the modes of a scalar field in a cyclic cosmology. In order to keep the discussion clear, we study the features of a scalar field in a toy model, a Friedman-Robertson-Walker universe with a periodic scale factor, in which the universe expands, contracts and bounces infinite times, in the approximation in which the dynamic features of this universe are driven by some external factor, without the backreaction of the scalar field under study. In particular, we show that particle production exhibits features of the cyclic cosmology. Also, by studying the Berry phase of the scalar field, we show that contrarily to what is commonly believed, the scalar field carries information from one bounce to another in the form of a global phase which occurs to be generically non-zero. {The Berry phase is then evaluated numerically in the case of the effective Loop Quantum Cosmology closed Universe. We observe that Berry's phase is nonzero, but that in the quantum regime the particle content is non-negligible. |
2102.08222 | Milko Estrada | Milko Estrada | A new exact solution of black-strings-like with a dS core | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We provide a new five dimensional black string--like solution by means of the
embedding of a four dimensional regular black hole into a compact extra
dimension. We enunciate a list of constraints in order to that the five
dimensional black string--like solution to be regular, and, following these
constraints we construct our solution. Instead of the usual singularity, it is
formed a core whose topology corresponds to the product between the de--Sitter
core of the four dimensional Hayward solution and $S^1$. The horizon has
topology $S^2 \times S^1$. At infinity of the radial coordinate the regular
four dimensional geometry is asymptotically flat, {\it i.e}, at this place the
topology of the complete solution corresponds to the product between Minkowski
and $S^1$. At the induced four dimensional geometry we compute the correct
values of temperature and entropy.
| [
{
"created": "Tue, 16 Feb 2021 15:34:58 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Estrada",
"Milko",
""
]
] | We provide a new five dimensional black string--like solution by means of the embedding of a four dimensional regular black hole into a compact extra dimension. We enunciate a list of constraints in order to that the five dimensional black string--like solution to be regular, and, following these constraints we construct our solution. Instead of the usual singularity, it is formed a core whose topology corresponds to the product between the de--Sitter core of the four dimensional Hayward solution and $S^1$. The horizon has topology $S^2 \times S^1$. At infinity of the radial coordinate the regular four dimensional geometry is asymptotically flat, {\it i.e}, at this place the topology of the complete solution corresponds to the product between Minkowski and $S^1$. At the induced four dimensional geometry we compute the correct values of temperature and entropy. |
gr-qc/0111015 | George Japaridze | W.D.Flanders, G.S.Japaridze | On a description of Gravitational Interaction between moving objects in
terms of Spatial Gravitational Fields | Will appear in International Journal of Theoretical Physics | Int.J.Theor.Phys.39:89,2001 | null | null | gr-qc physics.class-ph | null | Analyzing two simple experimental situations we show that from Newton's law
of gravitation and Special Relativity it follows that the motion of particle in
an external gravitational field can be described in terms of effective spatial
fields which satisfy Maxwell-like system of equations and propagate with the
speed of light. The description is adequate in a linear approximation in
gravitational field and in a first order in v^2/c^2.
| [
{
"created": "Tue, 6 Nov 2001 16:20:45 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Flanders",
"W. D.",
""
],
[
"Japaridze",
"G. S.",
""
]
] | Analyzing two simple experimental situations we show that from Newton's law of gravitation and Special Relativity it follows that the motion of particle in an external gravitational field can be described in terms of effective spatial fields which satisfy Maxwell-like system of equations and propagate with the speed of light. The description is adequate in a linear approximation in gravitational field and in a first order in v^2/c^2. |
gr-qc/0110014 | Piotr Chrusciel | Piotr T. Chrusciel, Gabriel Nagy | The mass of spacelike hypersurfaces in asymptotically anti-de Sitter
space-times | 49 pages, Latex2e with several style files; minor misprints corrected
here and there | Adv.Theor.Math.Phys. 5 (2002) 697-754 | null | null | gr-qc | null | We give a Hamiltonian definition of mass for spacelike hypersurfaces in
space-times with metrics which are asymptotic to the anti-de Sitter one, or to
a class of generalizations thereof. We show that our definition provides a
geometric invariant for a spacelike hypersurface embedded in a space-time.
| [
{
"created": "Tue, 2 Oct 2001 19:21:07 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Jan 2002 22:05:05 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Chrusciel",
"Piotr T.",
""
],
[
"Nagy",
"Gabriel",
""
]
] | We give a Hamiltonian definition of mass for spacelike hypersurfaces in space-times with metrics which are asymptotic to the anti-de Sitter one, or to a class of generalizations thereof. We show that our definition provides a geometric invariant for a spacelike hypersurface embedded in a space-time. |
0905.1670 | Benjamin Bahr | Benjamin Bahr, Bianca Dittrich | (Broken) Gauge Symmetries and Constraints in Regge Calculus | 32 pages, 15 figures | Class.Quant.Grav.26:225011,2009 | 10.1088/0264-9381/26/22/225011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We will examine the issue of diffeomorphism symmetry in simplicial models of
(quantum) gravity, in particular for Regge calculus. We find that for a
solution with curvature there do not exist exact gauge symmetries on the
discrete level. Furthermore we derive a canonical formulation that exactly
matches the dynamics and hence symmetries of the covariant picture. In this
canonical formulation broken symmetries lead to the replacements of constraints
by so--called pseudo constraints. These considerations should be taken into
account in attempts to connect spin foam models, based on the Regge action,
with canonical loop quantum gravity, which aims at implementing proper
constraints. We will argue that the long standing problem of finding a
consistent constraint algebra for discretized gravity theories is equivalent to
the problem of finding an action with exact diffeomorphism symmetries. Finally
we will analyze different limits in which the pseudo constraints might turn
into proper constraints. This could be helpful to infer alternative
discretization schemes in which the symmetries are not broken.
| [
{
"created": "Mon, 11 May 2009 18:37:32 GMT",
"version": "v1"
}
] | 2009-12-15 | [
[
"Bahr",
"Benjamin",
""
],
[
"Dittrich",
"Bianca",
""
]
] | We will examine the issue of diffeomorphism symmetry in simplicial models of (quantum) gravity, in particular for Regge calculus. We find that for a solution with curvature there do not exist exact gauge symmetries on the discrete level. Furthermore we derive a canonical formulation that exactly matches the dynamics and hence symmetries of the covariant picture. In this canonical formulation broken symmetries lead to the replacements of constraints by so--called pseudo constraints. These considerations should be taken into account in attempts to connect spin foam models, based on the Regge action, with canonical loop quantum gravity, which aims at implementing proper constraints. We will argue that the long standing problem of finding a consistent constraint algebra for discretized gravity theories is equivalent to the problem of finding an action with exact diffeomorphism symmetries. Finally we will analyze different limits in which the pseudo constraints might turn into proper constraints. This could be helpful to infer alternative discretization schemes in which the symmetries are not broken. |
1909.01799 | Behnam Pourhassan | M. Rostami, J. Sadeghi, S. Miraboutalebi, B. Pourhassan and A. A.
Masoudi | Phase transition of modified Horndeski gravity with new method | 18 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the critical points of the $ P-V $ diagram and
the phase transitions of the Horndenski black holes. In fact, the usual
Horndeski black holes do not have $ P-V $ critical points, hence do not show
any phase transitions. However, we successfully modify the Horndeski black hole
solution to obtain such a phase transition behavior. This modified black holes
solution is satisfied by the equation of state of liquid-gas phase transition.
Also, we study the thermodynamics of our modified Horndeski black hole by
applying a new method based on the equation of state that originated from the
slope of temperature versus entropy. This new prescription provides us a simple
powerful way to study the critical behavior and the phase transition of the
black holes and concludes the novel results. The analytical interpretation of
possible phase transition points leads us to set some nonphysical range on the
horizon radius for the black hole.
| [
{
"created": "Mon, 2 Sep 2019 18:53:39 GMT",
"version": "v1"
}
] | 2019-09-05 | [
[
"Rostami",
"M.",
""
],
[
"Sadeghi",
"J.",
""
],
[
"Miraboutalebi",
"S.",
""
],
[
"Pourhassan",
"B.",
""
],
[
"Masoudi",
"A. A.",
""
]
] | In this paper, we investigate the critical points of the $ P-V $ diagram and the phase transitions of the Horndenski black holes. In fact, the usual Horndeski black holes do not have $ P-V $ critical points, hence do not show any phase transitions. However, we successfully modify the Horndeski black hole solution to obtain such a phase transition behavior. This modified black holes solution is satisfied by the equation of state of liquid-gas phase transition. Also, we study the thermodynamics of our modified Horndeski black hole by applying a new method based on the equation of state that originated from the slope of temperature versus entropy. This new prescription provides us a simple powerful way to study the critical behavior and the phase transition of the black holes and concludes the novel results. The analytical interpretation of possible phase transition points leads us to set some nonphysical range on the horizon radius for the black hole. |
1501.02671 | Sean Gryb B | Sean Gryb | Is Spacetime Countable? | 13 pages, 7 figures. Illustrations by Marc Ngui. To appear in
Foundations of Physics Frontiers Collections: It From Bit or Bit From It?
Winner of 4th prize in FQXi Essay contest | It From Bit or Bit From It? The Frontiers Collection. pp 153-168.
Springer, 2015 | 10.1007/978-3-319-12946-4_14 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Is there a number for every bit of spacetime, or is spacetime smooth like the
real line? The ultimate fate of a quantum theory of gravity might depend on it.
The troublesome infinities of quantum gravity can be cured by assuming that
spacetime comes in countable, discrete pieces which one could simulate on a
computer. But, perhaps there is another way? In this essay, we propose a
picture where scale is meaningless so that there can be no minimum length and,
hence, no fundamental discreteness. In this picture, Einstein's Special
Relativity, suitably modified to accommodate an expanding Universe, can be
reinterpreted as a theory where only the instantaneous shapes of configurations
count.
| [
{
"created": "Mon, 12 Jan 2015 14:49:06 GMT",
"version": "v1"
}
] | 2018-01-18 | [
[
"Gryb",
"Sean",
""
]
] | Is there a number for every bit of spacetime, or is spacetime smooth like the real line? The ultimate fate of a quantum theory of gravity might depend on it. The troublesome infinities of quantum gravity can be cured by assuming that spacetime comes in countable, discrete pieces which one could simulate on a computer. But, perhaps there is another way? In this essay, we propose a picture where scale is meaningless so that there can be no minimum length and, hence, no fundamental discreteness. In this picture, Einstein's Special Relativity, suitably modified to accommodate an expanding Universe, can be reinterpreted as a theory where only the instantaneous shapes of configurations count. |
gr-qc/9312009 | null | J.G. Russo | On black hole singularities in quantum gravity | 8 pages, 3 figures (included), UTTG-32-93 | Phys.Lett. B339 (1994) 35-40 | 10.1016/0370-2693(94)91129-0 | null | gr-qc hep-th | null | We show that absence of space-like boundaries in 1+1 dimensional dilaton
gravity implies a catastrophic event at the end point of black hole
evaporation. The proof is completely independent of the physics at Planck
scales, which suggests that the same will occur in any theory of quantum
gravity which only admits trivial space-time topologies.
| [
{
"created": "Fri, 3 Dec 1993 17:04:36 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Russo",
"J. G.",
""
]
] | We show that absence of space-like boundaries in 1+1 dimensional dilaton gravity implies a catastrophic event at the end point of black hole evaporation. The proof is completely independent of the physics at Planck scales, which suggests that the same will occur in any theory of quantum gravity which only admits trivial space-time topologies. |
2201.02220 | Leah Jenks | Stephon Alexander, Gregory Gabadadze, Leah Jenks, Nicol\'as Yunes | Black Hole Superradiance in Dynamical Chern-Simons Gravity | Error in Eq. 51-53 and 69-71 corrected, updated discussion | null | 10.1103/PhysRevD.107.084016 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole superradiance provides a window into the dynamics of light scalar
fields and their interactions close to a rotating black hole. Due to the
rotation of the black hole, the amplitude of the scalar field becomes
magnified, leading to a "black hole bomb" effect. Recent work has demonstrated
that rotating black holes in dynamical Chern-Simons gravity possess unique
structures, the "Chern-Simons caps," which may influence the behavior of matter
near the black hole. Motivated by the presence of these caps, we study
superradiance in dynamical Chern-Simons gravity in the context of a slowly
rotating black hole. We find that additional modes are excited and contribute
to the superradiance beyond what is expected for a Kerr black hole. Studying
the superradiant spectrum of perturbations, we find that the Chern-Simons
contributions give rise to small corrections to the angular dependence of the
resulting scalar cloud. Finally, we comment on potential observable
consequences and future avenues for investigation.
| [
{
"created": "Thu, 6 Jan 2022 19:25:20 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2023 17:28:27 GMT",
"version": "v2"
}
] | 2023-04-19 | [
[
"Alexander",
"Stephon",
""
],
[
"Gabadadze",
"Gregory",
""
],
[
"Jenks",
"Leah",
""
],
[
"Yunes",
"Nicolás",
""
]
] | Black hole superradiance provides a window into the dynamics of light scalar fields and their interactions close to a rotating black hole. Due to the rotation of the black hole, the amplitude of the scalar field becomes magnified, leading to a "black hole bomb" effect. Recent work has demonstrated that rotating black holes in dynamical Chern-Simons gravity possess unique structures, the "Chern-Simons caps," which may influence the behavior of matter near the black hole. Motivated by the presence of these caps, we study superradiance in dynamical Chern-Simons gravity in the context of a slowly rotating black hole. We find that additional modes are excited and contribute to the superradiance beyond what is expected for a Kerr black hole. Studying the superradiant spectrum of perturbations, we find that the Chern-Simons contributions give rise to small corrections to the angular dependence of the resulting scalar cloud. Finally, we comment on potential observable consequences and future avenues for investigation. |
gr-qc/9412005 | Laszlo E. Szabo | Laszlo E. Szabo | Is Quantum Mechanics Compatible with a Deterministic Universe? Two
Interpretations of Quantum Probabilities | REVISED VERSION! ONLY SMALL CHANGES IN THE TEXT! compressed and
uuencoded postscript, a uuencoded version of a demo program file (epr.exe for
DOS) is attached as a "Figure" | null | 10.1007/BF02186578 | null | gr-qc quant-ph | null | Two problems will be considered: the question of hidden parameters and the
problem of Kolmogorovity of quantum probabilities. Both of them will be
analyzed from the point of view of two distinct understandings of quantum
mechanical probabilities. Our analysis will be focused, as a particular
example, on the Aspect-type EPR experiment. It will be shown that the quantum
mechanical probabilities appearing in this experiment can be consistently
understood as conditional probabilities without any paradoxical consequences.
Therefore, nothing implies in the Aspect experiment that quantum theory is
incompatible with a deterministic universe.
| [
{
"created": "Thu, 1 Dec 1994 19:05:33 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Dec 1994 11:40:29 GMT",
"version": "v2"
},
{
"created": "Thu, 13 Apr 1995 14:44:45 GMT",
"version": "v3"
}
] | 2009-10-22 | [
[
"Szabo",
"Laszlo E.",
""
]
] | Two problems will be considered: the question of hidden parameters and the problem of Kolmogorovity of quantum probabilities. Both of them will be analyzed from the point of view of two distinct understandings of quantum mechanical probabilities. Our analysis will be focused, as a particular example, on the Aspect-type EPR experiment. It will be shown that the quantum mechanical probabilities appearing in this experiment can be consistently understood as conditional probabilities without any paradoxical consequences. Therefore, nothing implies in the Aspect experiment that quantum theory is incompatible with a deterministic universe. |
2103.14313 | Yuichi Miyashita | Luca Buoninfante, Yuichi Miyashita | Gravitational field of scalar lumps in higher-derivative gravity | 21 pages, 6 figures. V2: version accepted for publication in PRD | Phys. Rev. D 103, 124068 (2021) | 10.1103/PhysRevD.103.124068 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the gravitational field sourced by localized scalar fields (lumps)
in higher-derivative theories of gravity. By working in a static and
spherically symmetric configuration, we find the linearized spacetime metrics
generated by scalar lumps for several Lagrangians: the vanishing potential,
i.e. free massive scalar field, a polynomial potential, and the tachyon
potential in open string field theory. We perform the analysis for different
theories of gravity: Einstein's general relativity, four-derivative gravity,
and ghost-free nonlocal gravity. We discuss the limit of validity of our
analysis and comment on possible future applications in the context of
astrophysical compact objects.
| [
{
"created": "Fri, 26 Mar 2021 08:01:35 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jun 2021 09:37:25 GMT",
"version": "v2"
}
] | 2021-07-07 | [
[
"Buoninfante",
"Luca",
""
],
[
"Miyashita",
"Yuichi",
""
]
] | We study the gravitational field sourced by localized scalar fields (lumps) in higher-derivative theories of gravity. By working in a static and spherically symmetric configuration, we find the linearized spacetime metrics generated by scalar lumps for several Lagrangians: the vanishing potential, i.e. free massive scalar field, a polynomial potential, and the tachyon potential in open string field theory. We perform the analysis for different theories of gravity: Einstein's general relativity, four-derivative gravity, and ghost-free nonlocal gravity. We discuss the limit of validity of our analysis and comment on possible future applications in the context of astrophysical compact objects. |
gr-qc/0209079 | Bahram Mashhoon | Bahram Mashhoon | Modification of the Doppler Effect due to the Helicity-Rotation Coupling | LaTeX file, no figures, 15 pages, amended version | Phys.Lett. A306 (2002) 66-72 | 10.1016/S0375-9601(02)01537-2 | null | gr-qc astro-ph physics.optics | null | The helicity-rotation coupling and its current empirical basis are examined.
The modification of the Doppler effect due to the coupling of photon spin with
the rotation of the observer is considered in detail in connection with its
applications in the Doppler tracking of spacecraft. Further implications of
this coupling and the possibility of searching for it in the intensity response
of a rotating detector are briefly discussed.
| [
{
"created": "Sun, 22 Sep 2002 23:20:14 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Oct 2002 03:24:12 GMT",
"version": "v2"
}
] | 2010-04-05 | [
[
"Mashhoon",
"Bahram",
""
]
] | The helicity-rotation coupling and its current empirical basis are examined. The modification of the Doppler effect due to the coupling of photon spin with the rotation of the observer is considered in detail in connection with its applications in the Doppler tracking of spacecraft. Further implications of this coupling and the possibility of searching for it in the intensity response of a rotating detector are briefly discussed. |
1007.0953 | Volker Perlick | Volker Perlick and Anthony Carr | On the initial-value problem of the Maxwell-Lorentz equations | 13 pages, 3 figures. One reference added. To appear in J. Phys. A | J.Phys.A43:445502,2010 | 10.1088/1751-8113/43/44/445502 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Maxwell-Lorentz equations, i.e., the equation of motion of a
charged dust coupled to Maxwell's equations, on an arbitrary
general-relativistic spacetime. We decompose this system of equations into
evolution equations and constraints, and we demonstrate that the evolution
equations are strongly hyperbolic. This result guarantees that the
initial-value problem of the Maxwell-Lorentz equations is well-posed. We
illustrate this general result with a discussion of spherically symmetric
solutions on Minkowski spacetime.
| [
{
"created": "Tue, 6 Jul 2010 16:54:41 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Oct 2010 00:18:25 GMT",
"version": "v2"
}
] | 2011-04-08 | [
[
"Perlick",
"Volker",
""
],
[
"Carr",
"Anthony",
""
]
] | We consider the Maxwell-Lorentz equations, i.e., the equation of motion of a charged dust coupled to Maxwell's equations, on an arbitrary general-relativistic spacetime. We decompose this system of equations into evolution equations and constraints, and we demonstrate that the evolution equations are strongly hyperbolic. This result guarantees that the initial-value problem of the Maxwell-Lorentz equations is well-posed. We illustrate this general result with a discussion of spherically symmetric solutions on Minkowski spacetime. |
2302.09062 | Rikpratik Sengupta | Rikpratik Sengupta, B. C. Paul, M. Kalam, P. Paul and A. Aich | Non-singular flat universes in braneworld and Loop Quantum Cosmology | 23 Pages, 12 Figs | Eur.Phys.J.Plus (2023) 138:929 | 10.1140/epjp/s13360-023-04541-w | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper we take matter source with non-linear Equation of state (EoS)
that has produced non-singular Emergent cosmology for spatially flat universe
in General Relativity and minimally coupled scalar field with two different
potentials that produce an inflationary emergent universe for positive spatial
curvature in the relativistic context. We study all these three cases both in
the context of Randall-Sundrum braneworld and effective Loop quantum cosmology
(LQC) for zero spatial curvature that is observationally favoured and in the
absence of any effective cosmological constant term. We solve the modified
Friedmann equation in each case to obtain the time evolution of the scale
factor and use it to check whether the initial singularity can be averted. In
almost all the cases we find the initial singularity is absent. We study the
nature of the slow roll inflation in the cases where we obtain inflationary
emergent universes. The inflationary scenario is found to be improved than in a
standard relatvistic context and we compare the improved scenario for both the
braneworld and LQC models. Interestingly, we also obtain bouncing and cyclic
universes from our analysis in some cases. We find that the initial singularity
can be averted for a spatially flat universe with specific choice of matter EoS
or scalar field potential, which do not violate the Null Energy condition in
most cases, taking into account effective high energy (curvature) corrections
with or without extra dimensions.
| [
{
"created": "Fri, 17 Feb 2023 18:57:28 GMT",
"version": "v1"
}
] | 2023-10-23 | [
[
"Sengupta",
"Rikpratik",
""
],
[
"Paul",
"B. C.",
""
],
[
"Kalam",
"M.",
""
],
[
"Paul",
"P.",
""
],
[
"Aich",
"A.",
""
]
] | In this paper we take matter source with non-linear Equation of state (EoS) that has produced non-singular Emergent cosmology for spatially flat universe in General Relativity and minimally coupled scalar field with two different potentials that produce an inflationary emergent universe for positive spatial curvature in the relativistic context. We study all these three cases both in the context of Randall-Sundrum braneworld and effective Loop quantum cosmology (LQC) for zero spatial curvature that is observationally favoured and in the absence of any effective cosmological constant term. We solve the modified Friedmann equation in each case to obtain the time evolution of the scale factor and use it to check whether the initial singularity can be averted. In almost all the cases we find the initial singularity is absent. We study the nature of the slow roll inflation in the cases where we obtain inflationary emergent universes. The inflationary scenario is found to be improved than in a standard relatvistic context and we compare the improved scenario for both the braneworld and LQC models. Interestingly, we also obtain bouncing and cyclic universes from our analysis in some cases. We find that the initial singularity can be averted for a spatially flat universe with specific choice of matter EoS or scalar field potential, which do not violate the Null Energy condition in most cases, taking into account effective high energy (curvature) corrections with or without extra dimensions. |
gr-qc/0408036 | Deborah A. Konkowski | D.A. Konkowski, T.M. Helliwell, and C. Wieland | Quantum Singularities | 5 pages, no figures, references current | Gravitation and Cosmology: Proceedings of the Spanish Relativity
Meeting 2002, ed. A. Lobo (Barcelona, Spain: University of Barcelona Press,
2003) 193 | null | null | gr-qc | null | The definitions of classical and quantum singularities in general relativity
are reviewed. The occurence of quantum mechanical singularities in certain
spherically symmetric and cylindrically symmetric (including infinite line
mass)spacetimes is considered. A strong repulsive ``potential'' near the
classical singularity is shown to turn a classically singular spacetime into a
quantum mechanically nonsingular spacetime.
| [
{
"created": "Thu, 12 Aug 2004 14:43:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Konkowski",
"D. A.",
""
],
[
"Helliwell",
"T. M.",
""
],
[
"Wieland",
"C.",
""
]
] | The definitions of classical and quantum singularities in general relativity are reviewed. The occurence of quantum mechanical singularities in certain spherically symmetric and cylindrically symmetric (including infinite line mass)spacetimes is considered. A strong repulsive ``potential'' near the classical singularity is shown to turn a classically singular spacetime into a quantum mechanically nonsingular spacetime. |
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