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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1412.7337 | Laurence Eaves | Laurence Eaves | The apparent fine-tuning of the cosmological, gravitational and fine
structure constants | 7 pages, no figures New title, enhanced and refined discussion, more
references. Results unchanged. v3: There were some typographical errors in
the previous versions which were pointed out by an anonymous referee, to whom
I am grateful. These have now been corrected. I have also made other minor
additions to the text. v4: 4 minor corrections/edits made | null | 10.1016/j.physa.2015.09.090 | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A numerical coincidence relating the values of the cosmological,
gravitational and electromagnetic fine structure constants is presented and
discussed in relation to the apparent anthropic fine-tuning of these three
fundamental constants of nature.
| [
{
"created": "Tue, 23 Dec 2014 12:18:12 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Mar 2015 15:50:44 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Aug 2015 15:08:39 GMT",
"version": "v3"
},
{
"created": "Thu, 13 Aug 2015 10:20:05 GMT",
"version": "v4"
}
] | 2015-10-26 | [
[
"Eaves",
"Laurence",
""
]
] | A numerical coincidence relating the values of the cosmological, gravitational and electromagnetic fine structure constants is presented and discussed in relation to the apparent anthropic fine-tuning of these three fundamental constants of nature. |
1112.1572 | Gonzalo Olmo | Gonzalo J. Olmo | Palatini Approach Beyond Einstein's Gravity | To appear in the proceedings of the XII International Symposium
Fundamental Frontiers of Physics (Udine, Italy, Nov.21-23, 2011) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review recent results obtained for extensions of general relativity
formulated within the Palatini formalism, an approach in which metric and
connection are treated as independent geometrical entities. The peculiar
dynamics of these theories, governed by second-order equations and having no
new degrees of freedom, makes them specially suitable to address certain
aspects of quantum gravity phenomenology, construct nonsingular bouncing
cosmologies, and explore black hole interiors, which in the Reissner-Nordstrom
case develop a compact core of finite density instead of a point-like
singularity.
| [
{
"created": "Wed, 7 Dec 2011 14:15:50 GMT",
"version": "v1"
}
] | 2011-12-08 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | I review recent results obtained for extensions of general relativity formulated within the Palatini formalism, an approach in which metric and connection are treated as independent geometrical entities. The peculiar dynamics of these theories, governed by second-order equations and having no new degrees of freedom, makes them specially suitable to address certain aspects of quantum gravity phenomenology, construct nonsingular bouncing cosmologies, and explore black hole interiors, which in the Reissner-Nordstrom case develop a compact core of finite density instead of a point-like singularity. |
0803.2807 | Valentino Lacquaniti | Valentino Lacquaniti, Giovanni Montani | On Matter Coupling in 5D Kaluza-Klein Model | 4 pages, to appear in Proceedings of the II Stueckelberg Workshop -
Int. J. Mod. Phys. A | Int.J.Mod.Phys.A23:1270-1273,2008 | 10.1142/S0217751X08040202 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze some unphysical features of the geodesic approach to matter
coupling in a compactified Kaluza-Klein scenario, like the q/m puzzle and the
huge massive modes. We propose a new approach, based on Papapetrou multipole
expansion, that provides a new equation for the motion of a test particle. We
show how this equation provides right couplings and does not generate huge
massive modes.
| [
{
"created": "Wed, 19 Mar 2008 14:38:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lacquaniti",
"Valentino",
""
],
[
"Montani",
"Giovanni",
""
]
] | We analyze some unphysical features of the geodesic approach to matter coupling in a compactified Kaluza-Klein scenario, like the q/m puzzle and the huge massive modes. We propose a new approach, based on Papapetrou multipole expansion, that provides a new equation for the motion of a test particle. We show how this equation provides right couplings and does not generate huge massive modes. |
1507.01696 | Plyatsko Roman | Roman Plyatsko, Mykola Fenyk, Oleksandr Stefanyshyn | Solutions of Mathisson-Papapetrou equations for highly relativistic
spinning particles | 13 pages, 8 figures. Invited contribution as part of the Springer
series "Fundamental Theories of Physics", v.179 (2015), "Equations of Motion
in Relativistic gravity", D. Puetzfeld et al. (eds.), p. 165-190 | null | 10.1007/978-3-319-18335-0_4 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Different types of essentially nongeodesic motions of highly relativistic
spinning particles in Schwarzschild's and Kerr's background which follows from
the Mathisson-Papapetrou (MP) equations are considered. It is shown that
dependently on the correlation of signs of the spin and the particle's orbital
velocity the spin-gravity coupling acts as a significant repulsive or
attractive force. Numerical estimates for electrons, protons, and neutrinos in
the gravitational field of black holes are presented. The correspondence
between the general relativistic Dirac equation and MP equations is discussed.
It is stressed that for the highly relativistic motions the adequate
supplementary condition for the MP equations is the Mathisson-Pirani condition.
In the following it is important to study the possible role of the highly
relativistic spin-gravity coupling in astrophysics, cosmology, and high energy
physics.
| [
{
"created": "Tue, 7 Jul 2015 08:02:10 GMT",
"version": "v1"
}
] | 2021-04-07 | [
[
"Plyatsko",
"Roman",
""
],
[
"Fenyk",
"Mykola",
""
],
[
"Stefanyshyn",
"Oleksandr",
""
]
] | Different types of essentially nongeodesic motions of highly relativistic spinning particles in Schwarzschild's and Kerr's background which follows from the Mathisson-Papapetrou (MP) equations are considered. It is shown that dependently on the correlation of signs of the spin and the particle's orbital velocity the spin-gravity coupling acts as a significant repulsive or attractive force. Numerical estimates for electrons, protons, and neutrinos in the gravitational field of black holes are presented. The correspondence between the general relativistic Dirac equation and MP equations is discussed. It is stressed that for the highly relativistic motions the adequate supplementary condition for the MP equations is the Mathisson-Pirani condition. In the following it is important to study the possible role of the highly relativistic spin-gravity coupling in astrophysics, cosmology, and high energy physics. |
2312.07443 | Jan Sbierski | Jan Sbierski | The $C^0$-inextendibility of a class of FLRW spacetimes | 21 pages, 3 figures | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies the singularity structure of FLRW spacetimes without
particle horizons at the $C^0$-level of the metric. We show that in the case of
constant spatial curvature $K=+1$, and without any further assumptions on the
scale factor, the big bang singularity is sufficiently strong to exclude
continuous spacetime extensions to the past. On the other hand it is known that
in the case of constant spatial curvature $K=-1$ continuous spacetime
extensions through the big-bang exist for certain choices of scale factor [4],
giving rise to Milne-like cosmologies. Complementing these results we exhibit a
geometric obstruction to continuous spacetime extensions which is present for a
large range of scale factors in the case $K=-1$.
| [
{
"created": "Tue, 12 Dec 2023 17:12:39 GMT",
"version": "v1"
}
] | 2023-12-13 | [
[
"Sbierski",
"Jan",
""
]
] | This paper studies the singularity structure of FLRW spacetimes without particle horizons at the $C^0$-level of the metric. We show that in the case of constant spatial curvature $K=+1$, and without any further assumptions on the scale factor, the big bang singularity is sufficiently strong to exclude continuous spacetime extensions to the past. On the other hand it is known that in the case of constant spatial curvature $K=-1$ continuous spacetime extensions through the big-bang exist for certain choices of scale factor [4], giving rise to Milne-like cosmologies. Complementing these results we exhibit a geometric obstruction to continuous spacetime extensions which is present for a large range of scale factors in the case $K=-1$. |
1907.05659 | Sajal Mukherjee | Sajal Mukherjee, Georgios Lukes-Gerakopoulos and Rajesh Kumble Nayak | Extended bodies moving on geodesic trajectories | 28 pages, no figure. v2, title changed, new author added, revised
version | General Relativity and Gravitation 54: 113 (2022) | 10.1007/s10714-022-02985-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work investigates whether an extended test body obeying the
Mathisson-Papapetrou- Dixon equations under the Ohashi-Kyrian-Semerak spin
supplementary condition can follow geodesic trajectories in curved spacetimes.
In particular, we explore what are the requirements under which pole-dipole and
pole-dipole-quadrupole approximated bodies moving in the Schwarzschild or Kerr
spacetimes can follow equatorial geodesic trajectories. We do this exploration
thoroughly in the pole-dipole case, while we focus just on particular
trajectories in the pole-dipole-quadrupole case. Using the
Ohashi-Kyrian-Semerak spin supplementary condition to fix the center of the
mass of a pole-dipole body has the advantage that the hidden momentum is
eliminated. This allows the four-velocity to be parallel to the four-momentum,
which provides a convenient framework for our investigation. We discuss how
this feature can be recovered at a pole-dipole-quadrupole approximation and
what are the consequences.
| [
{
"created": "Fri, 12 Jul 2019 10:19:27 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jun 2022 18:02:15 GMT",
"version": "v2"
}
] | 2022-10-05 | [
[
"Mukherjee",
"Sajal",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Nayak",
"Rajesh Kumble",
""
]
] | This work investigates whether an extended test body obeying the Mathisson-Papapetrou- Dixon equations under the Ohashi-Kyrian-Semerak spin supplementary condition can follow geodesic trajectories in curved spacetimes. In particular, we explore what are the requirements under which pole-dipole and pole-dipole-quadrupole approximated bodies moving in the Schwarzschild or Kerr spacetimes can follow equatorial geodesic trajectories. We do this exploration thoroughly in the pole-dipole case, while we focus just on particular trajectories in the pole-dipole-quadrupole case. Using the Ohashi-Kyrian-Semerak spin supplementary condition to fix the center of the mass of a pole-dipole body has the advantage that the hidden momentum is eliminated. This allows the four-velocity to be parallel to the four-momentum, which provides a convenient framework for our investigation. We discuss how this feature can be recovered at a pole-dipole-quadrupole approximation and what are the consequences. |
1907.12595 | Michael Seifert | Michael D Seifert | Lorentz-violating gravity and the bootstrap procedure | 24 pages | null | 10.1088/1361-6382/ab53ef | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In conventional gravitational physics, the so-called "bootstrap procedure"
can be used to extrapolate from a linear model of a rank-2 tensor to a full
non-linear theory of gravity (i.e., general relativity) via a coupling to the
stress-energy of the model. In this work, I extend this procedure to a
"Lorentz-violating" gravitational model, in which the linear tensor field and
the matter fields "see" different metrics due to a coupling between the tensor
field and a background vector field. The resulting model can be thought of as a
generalized Proca theory with a non-minimal coupling to conventional matter. It
has a similar linearized limit to the better-known "bumblebee model", but
differs at higher orders in perturbation theory. Its effects are unobservable
in FRW spacetimes, but are expected to be important in anisotropic cosmological
spacetimes.
| [
{
"created": "Mon, 29 Jul 2019 18:39:11 GMT",
"version": "v1"
}
] | 2020-04-08 | [
[
"Seifert",
"Michael D",
""
]
] | In conventional gravitational physics, the so-called "bootstrap procedure" can be used to extrapolate from a linear model of a rank-2 tensor to a full non-linear theory of gravity (i.e., general relativity) via a coupling to the stress-energy of the model. In this work, I extend this procedure to a "Lorentz-violating" gravitational model, in which the linear tensor field and the matter fields "see" different metrics due to a coupling between the tensor field and a background vector field. The resulting model can be thought of as a generalized Proca theory with a non-minimal coupling to conventional matter. It has a similar linearized limit to the better-known "bumblebee model", but differs at higher orders in perturbation theory. Its effects are unobservable in FRW spacetimes, but are expected to be important in anisotropic cosmological spacetimes. |
2208.10197 | Naoki Tsukamoto | Naoki Tsukamoto | Affine perturbation series of the deflection angle of a ray near the
photon sphere of a Reissner-Nordstr\"{o}m black hole | 8 pages, 4 figures, minor changes, accepted for publication in
Physical Review D | Phys. Rev. D 106, 084025 (2022) | 10.1103/PhysRevD.106.084025 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the affine perturbation series of the deflection angle of a
ray near the photon sphere of an extreme Reissner-Nordstr\"{o}m black hole. We
compare the 0th and 1st orders of the affine perturbation series with the
deflection angle in a strong deflection limit. We conclude that the 0th order
of the affine perturbation series is more accurate than the deflection angle in
the strong deflection limit and that we should improve a
strong-deflection-limit analysis by using the 0th order of the affine
perturbation series.
| [
{
"created": "Mon, 22 Aug 2022 10:39:24 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Oct 2022 03:54:31 GMT",
"version": "v2"
}
] | 2022-10-25 | [
[
"Tsukamoto",
"Naoki",
""
]
] | We investigate the affine perturbation series of the deflection angle of a ray near the photon sphere of an extreme Reissner-Nordstr\"{o}m black hole. We compare the 0th and 1st orders of the affine perturbation series with the deflection angle in a strong deflection limit. We conclude that the 0th order of the affine perturbation series is more accurate than the deflection angle in the strong deflection limit and that we should improve a strong-deflection-limit analysis by using the 0th order of the affine perturbation series. |
2105.02054 | Massimo Tinto | Massimo Tinto, Sanjeev Dhurandhar, Prasanna Joshi | Matrix Representation of Time-Delay Interferometry | 11 pages, 2 figures. Accepted for publication in Physical Review D | Phys. Rev. D 104, 044033 (2021) | 10.1103/PhysRevD.104.044033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time-Delay Interferometry (TDI) is the data processing technique that cancels
the large laser phase fluctuations affecting the one-way Doppler measurements
made by unequal-arm space-based gravitational wave interferometers. By taking
finite linear combinations of properly time-shifted Doppler measurements, laser
phase fluctuations are removed at any time $t$ and gravitational wave signals
can be studied at a requisite level of precision. In this article we show the
delay operators used in TDI can be represented as matrices acting on arrays
associated with the laser noises and Doppler measurements. The matrix
formulation is nothing but the group theoretic representation (ring
homomorphism) of the earlier approach involving time-delay operators and so in
principle is the same. It is shown that the homomorphism is valid generally and
we cover all situations of interest. To understand the potential advantages the
matrix representation brings, care must be taken by the data analyst to account
for the light travel times when linearly relating the one-way Doppler
measurements to the laser noises. This is especially important in view of the
future gravitational wave projects envisaged. We show that the matrix
formulation of TDI results in the cancellation of the laser noises at an
arbitrary time $t$ by only linearly combining a finite number of samples of the
one-way Doppler data measured at and around time $t$.
| [
{
"created": "Wed, 5 May 2021 13:46:14 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Jul 2021 15:26:07 GMT",
"version": "v2"
}
] | 2021-08-25 | [
[
"Tinto",
"Massimo",
""
],
[
"Dhurandhar",
"Sanjeev",
""
],
[
"Joshi",
"Prasanna",
""
]
] | Time-Delay Interferometry (TDI) is the data processing technique that cancels the large laser phase fluctuations affecting the one-way Doppler measurements made by unequal-arm space-based gravitational wave interferometers. By taking finite linear combinations of properly time-shifted Doppler measurements, laser phase fluctuations are removed at any time $t$ and gravitational wave signals can be studied at a requisite level of precision. In this article we show the delay operators used in TDI can be represented as matrices acting on arrays associated with the laser noises and Doppler measurements. The matrix formulation is nothing but the group theoretic representation (ring homomorphism) of the earlier approach involving time-delay operators and so in principle is the same. It is shown that the homomorphism is valid generally and we cover all situations of interest. To understand the potential advantages the matrix representation brings, care must be taken by the data analyst to account for the light travel times when linearly relating the one-way Doppler measurements to the laser noises. This is especially important in view of the future gravitational wave projects envisaged. We show that the matrix formulation of TDI results in the cancellation of the laser noises at an arbitrary time $t$ by only linearly combining a finite number of samples of the one-way Doppler data measured at and around time $t$. |
1807.08704 | Suprit Singh | Viqar Husain and Suprit Singh | Does quantum gravity relate the constants of nature? | It does. See the surfaces in Figure 2. The article has 9 pages, and 3
figures of which one is a table | null | 10.1142/S0218271819500159 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The central equation of quantum gravity is the Wheeler-DeWitt equation. We
give an argument suggesting that exact solutions of this equation give a
surface in the space of coupling constants. This provides a mechanism for
determining the cosmological constant as a function of the gravitational and
other interaction constants. We demonstrate the idea by computing one such
surface in a cosmological model.
| [
{
"created": "Mon, 23 Jul 2018 16:31:30 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Jul 2018 15:33:36 GMT",
"version": "v2"
}
] | 2018-11-02 | [
[
"Husain",
"Viqar",
""
],
[
"Singh",
"Suprit",
""
]
] | The central equation of quantum gravity is the Wheeler-DeWitt equation. We give an argument suggesting that exact solutions of this equation give a surface in the space of coupling constants. This provides a mechanism for determining the cosmological constant as a function of the gravitational and other interaction constants. We demonstrate the idea by computing one such surface in a cosmological model. |
0809.4143 | Kamal Nandi | K.K. Nandi, Y.Z. Zhang, R.G. Cai and A. Panchenko | Energetics in Condensate Star and Wormholes | 16 pages, 1 figure, references added, To appear in PRD | Phys.Rev.D79:024011,2009 | 10.1103/PhysRevD.79.024011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the total gravitational energy in localized sources having
static spherical symmetry and satisfying energy conditions is negative
(attractive gravity). A natural query is how the gravitational energy behaves
under circumstances where energy conditions are violated. To answer this, the
known expression for the gravitational energy is suitably modified to account
for situations like the ones occurring in wormhole spacetime. It is then
exemplified that in many cases the modified expression yields desirable
answers. The implications are discussed.
| [
{
"created": "Wed, 24 Sep 2008 09:58:26 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Dec 2008 12:39:28 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Dec 2008 09:49:01 GMT",
"version": "v3"
}
] | 2009-01-21 | [
[
"Nandi",
"K. K.",
""
],
[
"Zhang",
"Y. Z.",
""
],
[
"Cai",
"R. G.",
""
],
[
"Panchenko",
"A.",
""
]
] | It is known that the total gravitational energy in localized sources having static spherical symmetry and satisfying energy conditions is negative (attractive gravity). A natural query is how the gravitational energy behaves under circumstances where energy conditions are violated. To answer this, the known expression for the gravitational energy is suitably modified to account for situations like the ones occurring in wormhole spacetime. It is then exemplified that in many cases the modified expression yields desirable answers. The implications are discussed. |
1508.02592 | Jean-Philippe Nicolas | Jean-Philippe Nicolas | The conformal approach to asymptotic analysis | 32 pages, 6 figures | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This essay was written as an extended version of a talk given at a conference
in Strasbourg on "Riemann, Einstein and geometry", organized by Athanase
Papadopoulos in September 2014. Its aim is to present Roger Penrose's approach
to asymptotic analysis in general relativity, which is based on conformal
geometric techniques, focusing on historical and recent aspects of two
specialized topics~: conformal scattering and peeling.
| [
{
"created": "Tue, 11 Aug 2015 13:47:42 GMT",
"version": "v1"
}
] | 2015-08-12 | [
[
"Nicolas",
"Jean-Philippe",
""
]
] | This essay was written as an extended version of a talk given at a conference in Strasbourg on "Riemann, Einstein and geometry", organized by Athanase Papadopoulos in September 2014. Its aim is to present Roger Penrose's approach to asymptotic analysis in general relativity, which is based on conformal geometric techniques, focusing on historical and recent aspects of two specialized topics~: conformal scattering and peeling. |
gr-qc/0505062 | Anzhong Wang | A.Y. Miguelote, N. A. Tomimura and Anzhong Wang | Gravitational Collapse of Circularly Symmetric Stiff Fluid with
Self-Similarity in 2+1 Gravity | latex file, 1 figure; last version to appear in Prog. Theor. Phys | null | 10.1143/PTP.114.895 | null | gr-qc | null | Linear perturbations of homothetic self-similar stiff fluid solutions,
$S[n]$, with circular symmetry in 2+1 gravity are studied. It is found that,
except for those with $n = 1$ and $n = 3$, none of them is stable and all have
more than one unstable mode. Hence, {\em none of these solutions can be
critical}.
| [
{
"created": "Thu, 12 May 2005 20:02:06 GMT",
"version": "v1"
},
{
"created": "Wed, 25 May 2005 17:25:52 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Oct 2005 21:05:27 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Miguelote",
"A. Y.",
""
],
[
"Tomimura",
"N. A.",
""
],
[
"Wang",
"Anzhong",
""
]
] | Linear perturbations of homothetic self-similar stiff fluid solutions, $S[n]$, with circular symmetry in 2+1 gravity are studied. It is found that, except for those with $n = 1$ and $n = 3$, none of them is stable and all have more than one unstable mode. Hence, {\em none of these solutions can be critical}. |
1501.05841 | Shahram Panahiyan | S. H. Hendi, S. Panahiyan and H. Mohammadpour | Third order Lovelock black branes in the presence of a nonlinear
electromagnetic field | 6 pages, 3 figures | Eur. Phys. J. C 72 (2012)2184 | 10.1140/epjc/s10052-012-2184-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider third order Lovelock gravity coupled to an U(1) gauge field for
which its Lagrangian is given by a power of Maxwell invariant. In this paper,
we present a class of horizon flat rotating black branes and investigate their
geometrical properties and the effect of nonlinearity on the solutions. We use
some known formulas and methods to calculate thermodynamic and conserved
quantities. Finally, we check the satisfaction of the first law of
thermodynamics.
| [
{
"created": "Thu, 22 Jan 2015 13:12:42 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Hendi",
"S. H.",
""
],
[
"Panahiyan",
"S.",
""
],
[
"Mohammadpour",
"H.",
""
]
] | We consider third order Lovelock gravity coupled to an U(1) gauge field for which its Lagrangian is given by a power of Maxwell invariant. In this paper, we present a class of horizon flat rotating black branes and investigate their geometrical properties and the effect of nonlinearity on the solutions. We use some known formulas and methods to calculate thermodynamic and conserved quantities. Finally, we check the satisfaction of the first law of thermodynamics. |
1106.5283 | Roh-Suan Tung | Kerson Huang, Hwee-Boon Low, Roh-Suan Tung | Scalar Field Cosmology II: Superfluidity, Quantum Turbulence, and
Inflation | 29 pages, 7 figures, published version | International Journal of Modern Physics A 27 (2012) 1250154 | 10.1142/S0217751X12501540 | IASa003 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize the big-bang model in a previous paper by extending the real
vacuum scalar field to a complex vacuum scalar field, within the FLRW
framework. The phase dynamics of the scalar field, which makes the universe a
superfluid, is described in terms of a density of quantized vortex lines, and a
tangle of vortex lines gives rise to quantum turbulence. We propose that all
the matter in the universe was created in the turbulence, through reconnection
of vortex lines, a process necessary for the maintenance of the vortex tangle.
The vortex tangle grows and decays, and its lifetime is the era of inflation.
These ideas are implemented in a set of closed cosmological equations that
describe the cosmic expansion driven by the scalar field on the one hand, and
the vortex-matter dynamics on the other. We show how these two aspects decouple
from each other, due to a vast difference in energy scales. The model is not
valid beyond the inflation era, but the universe remains a superfluid
afterwards. This gives rise to observable effects in the present universe,
including dark matter, galactic voids, non-thermal filaments, and cosmic jets.
| [
{
"created": "Sun, 26 Jun 2011 23:39:29 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jun 2011 16:32:54 GMT",
"version": "v2"
},
{
"created": "Thu, 15 Sep 2011 09:12:18 GMT",
"version": "v3"
},
{
"created": "Wed, 10 Oct 2012 09:17:30 GMT",
"version": "v4"
}
] | 2012-10-11 | [
[
"Huang",
"Kerson",
""
],
[
"Low",
"Hwee-Boon",
""
],
[
"Tung",
"Roh-Suan",
""
]
] | We generalize the big-bang model in a previous paper by extending the real vacuum scalar field to a complex vacuum scalar field, within the FLRW framework. The phase dynamics of the scalar field, which makes the universe a superfluid, is described in terms of a density of quantized vortex lines, and a tangle of vortex lines gives rise to quantum turbulence. We propose that all the matter in the universe was created in the turbulence, through reconnection of vortex lines, a process necessary for the maintenance of the vortex tangle. The vortex tangle grows and decays, and its lifetime is the era of inflation. These ideas are implemented in a set of closed cosmological equations that describe the cosmic expansion driven by the scalar field on the one hand, and the vortex-matter dynamics on the other. We show how these two aspects decouple from each other, due to a vast difference in energy scales. The model is not valid beyond the inflation era, but the universe remains a superfluid afterwards. This gives rise to observable effects in the present universe, including dark matter, galactic voids, non-thermal filaments, and cosmic jets. |
2107.13483 | Roldao da Rocha | Roldao da Rocha | Gravitational decoupling and superfluid stars | 17 pages, 31 figures, improved, published version | Eur. Phys. J C 81 (2021) 845 | 10.1140/epjc/s10052-021-09647-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational decoupling is applied to studying minimal geometric
deformed (MGD) compact superfluid stars, in covariant logarithmic scalar
gravity on fluid branes. The brane finite tension is shown to provide more
realistic values for the asymptotic value of the mass function of MGD
superfluid stars, besides constraining the range of the self-interacting scalar
field, minimally coupled to gravity. Several other physical features of MGD
superfluid stars, regulated by the finite brane tension and a decoupling
parameter, are derived and discussed, with important corrections to the
general-relativistic limit that corroborate to current observational data.
| [
{
"created": "Wed, 28 Jul 2021 16:47:09 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Sep 2021 12:07:18 GMT",
"version": "v2"
}
] | 2021-09-24 | [
[
"da Rocha",
"Roldao",
""
]
] | The gravitational decoupling is applied to studying minimal geometric deformed (MGD) compact superfluid stars, in covariant logarithmic scalar gravity on fluid branes. The brane finite tension is shown to provide more realistic values for the asymptotic value of the mass function of MGD superfluid stars, besides constraining the range of the self-interacting scalar field, minimally coupled to gravity. Several other physical features of MGD superfluid stars, regulated by the finite brane tension and a decoupling parameter, are derived and discussed, with important corrections to the general-relativistic limit that corroborate to current observational data. |
1102.1521 | Antonio De Felice | Antonio De Felice, Teruaki Suyama, Takahiro Tanaka | Stability of Schwarzschild-like solutions in f(R,G) gravity models | 15 pages, uses RevTeX4-1 | Phys.Rev.D83:104035,2011 | 10.1103/PhysRevD.83.104035 | YITP-11-17 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear metric perturbations around a spherically symmetric static
spacetime for general f(R,G) theories, where R is the Ricci scalar and G is the
Gauss-Bonnet term. We find that unless the determinant of the Hessian of f(R,G)
is zero, even-type perturbations have a ghost for any multi-pole mode. In order
for these theories to be plausible alternatives to General Relativity, the
theory should satisfy the condition that the ghost is massive enough to
effectively decouple from the other fields. We study the requirement on the
form of f(R,G) which satisfies this condition. We also classify the number of
propagating modes both for the odd-type and the even-type perturbations and
derive the propagation speeds for each mode.
| [
{
"created": "Tue, 8 Feb 2011 07:24:28 GMT",
"version": "v1"
}
] | 2011-06-02 | [
[
"De Felice",
"Antonio",
""
],
[
"Suyama",
"Teruaki",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We study linear metric perturbations around a spherically symmetric static spacetime for general f(R,G) theories, where R is the Ricci scalar and G is the Gauss-Bonnet term. We find that unless the determinant of the Hessian of f(R,G) is zero, even-type perturbations have a ghost for any multi-pole mode. In order for these theories to be plausible alternatives to General Relativity, the theory should satisfy the condition that the ghost is massive enough to effectively decouple from the other fields. We study the requirement on the form of f(R,G) which satisfies this condition. We also classify the number of propagating modes both for the odd-type and the even-type perturbations and derive the propagation speeds for each mode. |
1903.12486 | Junji Jia | Yaoguang Wang, Xionghui Liu, Nan Yang, Jiawei Liu and Junji Jia | Escape, bound and capture geodesics in local static coordinates in
Schwarzschild spacetime | 26 pages, 10 figures | null | 10.1007/s10714-020-2666-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The classical geodesics of timelike particles in Schwarzschild spacetime is
analyzed according to the particle starting radius $r$, velocity $v$ and angle
$\alpha$ against the radial outward direction in the reference system of an
local static observer. The region of escape, bound and capture orbits in the
parameter space of $(r,~v,~\alpha)$ are solved using the three cases of the
effective potential. It is found that generally for radius smaller than $4M$ or
velocity larger than $c/\sqrt{2}$ there will be no bound orbits. While for
fixed radius larger than $4M$ (or velocity smaller than $c/\sqrt{2}$), as
velocity (or radius) increase from zero (or $2M$), the particle is always
captured until a critical value $v_{\mathrm{crit1}}$ (or $r_{\mathrm{crit1}}$)
when the bound orbit start to appear around $\alpha=\pi/2$ between a
double-napped cone structure. As the velocity (or radius) increases to another
critical value $v_{\mathrm{crit2}}$ (or $r_{\mathrm{crit2}}$) then the bound
directions and escape directions in the outward cone become escape directions,
leaving only the inward cone separating the capture and bound directions. The
angle of this cone will increase to its asymptotic value as velocity (or
radius) increases to its asymptotic value. The implication of these results in
shadow of black holes formed by massive particles, in black hole accretion and
in spacecraft navigation is briefly discussed.
| [
{
"created": "Fri, 29 Mar 2019 12:48:18 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jul 2019 05:39:41 GMT",
"version": "v2"
}
] | 2020-03-11 | [
[
"Wang",
"Yaoguang",
""
],
[
"Liu",
"Xionghui",
""
],
[
"Yang",
"Nan",
""
],
[
"Liu",
"Jiawei",
""
],
[
"Jia",
"Junji",
""
]
] | The classical geodesics of timelike particles in Schwarzschild spacetime is analyzed according to the particle starting radius $r$, velocity $v$ and angle $\alpha$ against the radial outward direction in the reference system of an local static observer. The region of escape, bound and capture orbits in the parameter space of $(r,~v,~\alpha)$ are solved using the three cases of the effective potential. It is found that generally for radius smaller than $4M$ or velocity larger than $c/\sqrt{2}$ there will be no bound orbits. While for fixed radius larger than $4M$ (or velocity smaller than $c/\sqrt{2}$), as velocity (or radius) increase from zero (or $2M$), the particle is always captured until a critical value $v_{\mathrm{crit1}}$ (or $r_{\mathrm{crit1}}$) when the bound orbit start to appear around $\alpha=\pi/2$ between a double-napped cone structure. As the velocity (or radius) increases to another critical value $v_{\mathrm{crit2}}$ (or $r_{\mathrm{crit2}}$) then the bound directions and escape directions in the outward cone become escape directions, leaving only the inward cone separating the capture and bound directions. The angle of this cone will increase to its asymptotic value as velocity (or radius) increases to its asymptotic value. The implication of these results in shadow of black holes formed by massive particles, in black hole accretion and in spacecraft navigation is briefly discussed. |
1308.4063 | Muxin Han | Muxin Han | Covariant Loop Quantum Gravity, Low Energy Perturbation Theory, and
Einstein Gravity with High Curvature UV Corrections | 5 pages, 1 figure, presentation improved, references added | Phys. Rev. D 89, 124001 (2014) | 10.1103/PhysRevD.89.124001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A low-energy perturbation theory is developed from the nonperturbative
framework of covariant Loop Quantum Gravity (LQG) by employing the background
field method. The resulting perturbation theory is a 2-parameter expansion in
the semiclassical and low-energy regime. The two expansion parameters are the
large spin and small curvature. The leading order effective action coincides
with the Einstein-Hilbert action. The subleading corrections organized by the
two expansion parameters give the modifications of Einstein gravity in quantum
and high-energy regime from LQG. The perturbation theory developed here shows
for the first time that covariant LQG produces the high curvature corrections
to Einstein gravity. This result means that LQG is not a naive quantization of
Einstein gravity, but rather provides the UV modification. The result of the
paper may be viewed as the first step toward understanding the UV completeness
of LQG.
| [
{
"created": "Mon, 19 Aug 2013 15:45:03 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Aug 2013 17:03:23 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Feb 2014 12:48:47 GMT",
"version": "v3"
}
] | 2014-06-17 | [
[
"Han",
"Muxin",
""
]
] | A low-energy perturbation theory is developed from the nonperturbative framework of covariant Loop Quantum Gravity (LQG) by employing the background field method. The resulting perturbation theory is a 2-parameter expansion in the semiclassical and low-energy regime. The two expansion parameters are the large spin and small curvature. The leading order effective action coincides with the Einstein-Hilbert action. The subleading corrections organized by the two expansion parameters give the modifications of Einstein gravity in quantum and high-energy regime from LQG. The perturbation theory developed here shows for the first time that covariant LQG produces the high curvature corrections to Einstein gravity. This result means that LQG is not a naive quantization of Einstein gravity, but rather provides the UV modification. The result of the paper may be viewed as the first step toward understanding the UV completeness of LQG. |
1101.2722 | Hernando Quevedo | M. Akbar, H. Quevedo, K. Saifullah, A. Sanchez, and S. Taj | Thermodynamic Geometry Of Charged Rotating BTZ Black Holes | null | Phys.Rev.D83:084031,2011 | 10.1103/PhysRevD.83.084031 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamics and the thermodynamic geometries of charged
rotating BTZ (CR-BTZ) black holes in (2+1)-gravity. We investigate the
thermodynamics of these systems within the context of the Weinhold and
Ruppeiner thermodynamic geometries and the recently developed formalism of
geometrothermodynamics (GTD). Considering the behavior of the heat capacity and
the Hawking temperature, we show that Weinhold and Ruppeiner geometries cannot
describe completely the thermodynamics of these black holes and of their
limiting case of vanishing electric charge. In contrast, the Legendre
invariance imposed on the metric in GTD allows one to describe the CR-BTZ black
holes and their limiting cases in a consistent and invariant manner.
| [
{
"created": "Fri, 14 Jan 2011 06:30:41 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"Akbar",
"M.",
""
],
[
"Quevedo",
"H.",
""
],
[
"Saifullah",
"K.",
""
],
[
"Sanchez",
"A.",
""
],
[
"Taj",
"S.",
""
]
] | We study the thermodynamics and the thermodynamic geometries of charged rotating BTZ (CR-BTZ) black holes in (2+1)-gravity. We investigate the thermodynamics of these systems within the context of the Weinhold and Ruppeiner thermodynamic geometries and the recently developed formalism of geometrothermodynamics (GTD). Considering the behavior of the heat capacity and the Hawking temperature, we show that Weinhold and Ruppeiner geometries cannot describe completely the thermodynamics of these black holes and of their limiting case of vanishing electric charge. In contrast, the Legendre invariance imposed on the metric in GTD allows one to describe the CR-BTZ black holes and their limiting cases in a consistent and invariant manner. |
2004.12421 | Hai-Tian Wang | Hai-Tian Wang, Peng-Cheng Li, Jin-Liang Jiang, Guan-Wen Yuan, Yi-Ming
Hu and Yi-Zhong Fan | Constrains on the electric charges of the binary black holes with GWTC-1
events | 9 pages, 3 figures | Eur. Phys. J. C (2021) 81:769 | 10.1140/epjc/s10052-021-09555-1 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Testing black hole's charged property is a fascinating topic in modified
gravity and black hole astrophysics. In the first Gravitational-Wave Transient
Catalog (GWTC-1), ten binary black hole merger events have been formally
reported, and these gravitational wave signals have significantly enhanced our
understanding of the black hole. In this paper, we try to constrain the amount
of electric charge with the parameterized post-Einsteinian framework by
treating the electric charge as a small perturbation in a Bayesian way. We find
that the current limits in our work are consistent with the result of Fisher
information matrix method in previous works. We also develop a waveform model
considering a leading order charge effect for binary black hole inspiral.
| [
{
"created": "Sun, 26 Apr 2020 15:53:41 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Nov 2020 08:01:15 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Aug 2021 01:56:35 GMT",
"version": "v3"
}
] | 2021-08-30 | [
[
"Wang",
"Hai-Tian",
""
],
[
"Li",
"Peng-Cheng",
""
],
[
"Jiang",
"Jin-Liang",
""
],
[
"Yuan",
"Guan-Wen",
""
],
[
"Hu",
"Yi-Ming",
""
],
[
"Fan",
"Yi-Zhong",
""
]
] | Testing black hole's charged property is a fascinating topic in modified gravity and black hole astrophysics. In the first Gravitational-Wave Transient Catalog (GWTC-1), ten binary black hole merger events have been formally reported, and these gravitational wave signals have significantly enhanced our understanding of the black hole. In this paper, we try to constrain the amount of electric charge with the parameterized post-Einsteinian framework by treating the electric charge as a small perturbation in a Bayesian way. We find that the current limits in our work are consistent with the result of Fisher information matrix method in previous works. We also develop a waveform model considering a leading order charge effect for binary black hole inspiral. |
2005.14653 | Jaume Haro | Jaume Haro and Llibert Arest\'e Sal\'o | Note on the reheating temperature in Starobinsky-type potentials | Version accepted for publication in GERG | null | 10.1007/s10714-020-02770-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relation between the reheating temperature, the number of e-folds and the
spectral index is shown for the Starobinsky model and some of its descendants
through a very detailed calculation of these three quantities. The conclusion
is that for viable temperatures between $1$ MeV and $10^9$ GeV the
corresponding values of the spectral index enter perfectly in its $2sigma$
C.L., which shows the viability of this kind of models.
| [
{
"created": "Fri, 29 May 2020 16:31:53 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2020 15:23:52 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Nov 2020 09:53:51 GMT",
"version": "v3"
}
] | 2021-04-14 | [
[
"Haro",
"Jaume",
""
],
[
"Saló",
"Llibert Aresté",
""
]
] | The relation between the reheating temperature, the number of e-folds and the spectral index is shown for the Starobinsky model and some of its descendants through a very detailed calculation of these three quantities. The conclusion is that for viable temperatures between $1$ MeV and $10^9$ GeV the corresponding values of the spectral index enter perfectly in its $2sigma$ C.L., which shows the viability of this kind of models. |
1902.08180 | Baoyi Chen | Baoyi Chen, Yanbei Chen, Yiqiu Ma, Ka-Lok R. Lo, and Ling Sun | Instability of exotic compact objects and its implications for
gravitational-wave echoes | 5 pages, 4 figures | null | null | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Exotic compact objects (ECOs) have recently become an exciting research
subject, since they are speculated to have a special response to the incident
gravitational waves (GWs) that leads to GW echoes. We show that energy carried
by GWs can easily cause the event horizon to form out of a static ECO ---
leaving no echo signals towards spatial infinity. To show this, we use the
ingoing Vaidya spacetime and take into account the back reaction due to
incoming GWs. Demanding that an ECO does not collapse into a black hole puts an
upper bound on the compactness of the ECO, at the cost of less distinct echo
signals for smaller compactness. The trade-off between echoes' detectability
and distinguishability leads to a fine tuning of ECO parameters for LIGO to
find distinct echoes. We also show that an extremely compact ECO that can
survive the gravitational collapse and give rise to GW echoes might have to
expand its surface in a non-causal way.
| [
{
"created": "Thu, 21 Feb 2019 18:45:24 GMT",
"version": "v1"
}
] | 2019-02-22 | [
[
"Chen",
"Baoyi",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Ma",
"Yiqiu",
""
],
[
"Lo",
"Ka-Lok R.",
""
],
[
"Sun",
"Ling",
""
]
] | Exotic compact objects (ECOs) have recently become an exciting research subject, since they are speculated to have a special response to the incident gravitational waves (GWs) that leads to GW echoes. We show that energy carried by GWs can easily cause the event horizon to form out of a static ECO --- leaving no echo signals towards spatial infinity. To show this, we use the ingoing Vaidya spacetime and take into account the back reaction due to incoming GWs. Demanding that an ECO does not collapse into a black hole puts an upper bound on the compactness of the ECO, at the cost of less distinct echo signals for smaller compactness. The trade-off between echoes' detectability and distinguishability leads to a fine tuning of ECO parameters for LIGO to find distinct echoes. We also show that an extremely compact ECO that can survive the gravitational collapse and give rise to GW echoes might have to expand its surface in a non-causal way. |
2404.03607 | Anuj Kankani | Anuj Kankani and Sean T. McWilliams | Testing the Boundary-to-Bound Correspondence with Numerical Relativity | null | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Boundary-to-Bound (B2B) correspondence, which connects orbital and
radiative observables between bound and unbound orbits, has recently been
introduced and demonstrated in the perturbative regime. We produce a large
number of numerical relativity simulations of bound and unbound encounters
between two nonspinning equal mass black holes in order to test this
correspondence in the non-perturbative regime. We focus on testing the radiated
energy and angular momentum, as well as orbital parameters such as the period
and periastron advance. We find that, across a wide range of eccentricities,
the B2B relationships do not hold in the non-perturbative regime, thereby
placing a clear limit on the applicability of these relationships. We also
approximate the separatrix between bound and unbound relativistic encounters as
a function of their initial energies and angular momenta.
| [
{
"created": "Thu, 4 Apr 2024 17:28:43 GMT",
"version": "v1"
}
] | 2024-04-05 | [
[
"Kankani",
"Anuj",
""
],
[
"McWilliams",
"Sean T.",
""
]
] | The Boundary-to-Bound (B2B) correspondence, which connects orbital and radiative observables between bound and unbound orbits, has recently been introduced and demonstrated in the perturbative regime. We produce a large number of numerical relativity simulations of bound and unbound encounters between two nonspinning equal mass black holes in order to test this correspondence in the non-perturbative regime. We focus on testing the radiated energy and angular momentum, as well as orbital parameters such as the period and periastron advance. We find that, across a wide range of eccentricities, the B2B relationships do not hold in the non-perturbative regime, thereby placing a clear limit on the applicability of these relationships. We also approximate the separatrix between bound and unbound relativistic encounters as a function of their initial energies and angular momenta. |
1301.5543 | Christian Friedrich Steinwachs | Christian F. Steinwachs and Alexander Yu. Kamenshchik | Non-minimal Higgs Inflation and Frame Dependence in Cosmology | 4 pages, 3 figures. To appear in the proceedings of the Multiverse
and Fundamental Cosmology Conference (Multicosmofun 2012), Szczecin, Poland | null | 10.1063/1.4791748 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a very general class of cosmological models with scalar fields
non-minimally coupled to gravity. A particular representative in this class is
given by the non-minimal Higgs inflation model in which the Standard Model
Higgs boson and the inflaton are described by one and the same scalar particle.
While the predictions of the non-minimal Higgs inflation scenario come
numerically remarkably close to the recently discovered mass of the Higgs
boson, there remains a conceptual problem in this model that is associated with
the choice of the cosmological frame. While the classical theory is independent
of this choice, we find by an explicit calculation that already the first
quantum corrections induce a frame dependence. We give a geometrical
explanation of this frame dependence by embedding it into a more general field
theoretical context. From this analysis, some conceptional points in the long
lasting cosmological debate: "Jordan frame vs. Einstein frame" become more
transparent and in principle can be resolved in a natural way.
| [
{
"created": "Wed, 23 Jan 2013 15:51:38 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Steinwachs",
"Christian F.",
""
],
[
"Kamenshchik",
"Alexander Yu.",
""
]
] | We investigate a very general class of cosmological models with scalar fields non-minimally coupled to gravity. A particular representative in this class is given by the non-minimal Higgs inflation model in which the Standard Model Higgs boson and the inflaton are described by one and the same scalar particle. While the predictions of the non-minimal Higgs inflation scenario come numerically remarkably close to the recently discovered mass of the Higgs boson, there remains a conceptual problem in this model that is associated with the choice of the cosmological frame. While the classical theory is independent of this choice, we find by an explicit calculation that already the first quantum corrections induce a frame dependence. We give a geometrical explanation of this frame dependence by embedding it into a more general field theoretical context. From this analysis, some conceptional points in the long lasting cosmological debate: "Jordan frame vs. Einstein frame" become more transparent and in principle can be resolved in a natural way. |
1007.2429 | Nicolas Yunes | David Garfinkle, Frans Pretorius and Nicolas Yunes | Linear Stability Analysis and the Speed of Gravitational Waves in
Dynamical Chern-Simons Modified Gravity | 4 pages, no figures, accepted for publication in Phys. Rev. D, Rapid
Communications. Corrected a typo in the printed version in Eq. (12) | Phys.Rev.D82:041501,2010 | 10.1103/PhysRevD.82.041501 | null | gr-qc astro-ph.CO astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a linear stability analysis of dynamical Chern-Simons modified
gravity in the geometric optics approximation and find that it is linearly
stable on the backgrounds considered. Our analysis also reveals that
gravitational waves in the modified theory travel at the speed of light in
Minkowski spacetime. However, on a Schwarzschild background the characteristic
speed of propagation along a given direction splits into two modes, one
subluminal and one superluminal. The width of the splitting depends on the
azimuthal components of the propagation vector, is linearly proportional to the
mass of the black hole, and decreases with the third inverse power of the
distance from the black hole. Radial propagation is unaffected, implying that
as probed by gravitational waves the location of the event horizon of the
spacetime is unaltered. The analysis further reveals that when a high
frequency, pure gravitational wave is scattered from a black hole, a scalar
wave of comparable amplitude is excited, and vice-versa.
| [
{
"created": "Wed, 14 Jul 2010 20:38:06 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Oct 2013 15:36:14 GMT",
"version": "v2"
}
] | 2013-10-09 | [
[
"Garfinkle",
"David",
""
],
[
"Pretorius",
"Frans",
""
],
[
"Yunes",
"Nicolas",
""
]
] | We perform a linear stability analysis of dynamical Chern-Simons modified gravity in the geometric optics approximation and find that it is linearly stable on the backgrounds considered. Our analysis also reveals that gravitational waves in the modified theory travel at the speed of light in Minkowski spacetime. However, on a Schwarzschild background the characteristic speed of propagation along a given direction splits into two modes, one subluminal and one superluminal. The width of the splitting depends on the azimuthal components of the propagation vector, is linearly proportional to the mass of the black hole, and decreases with the third inverse power of the distance from the black hole. Radial propagation is unaffected, implying that as probed by gravitational waves the location of the event horizon of the spacetime is unaltered. The analysis further reveals that when a high frequency, pure gravitational wave is scattered from a black hole, a scalar wave of comparable amplitude is excited, and vice-versa. |
2111.02894 | Bivudutta Mishra Dr. | A.S. Agrawal, Francisco Tello-Ortiz, B.Mishra, S.K. Tripathy | Bouncing cosmology in extended gravity and its reconstruction as dark
energy model | 13 pages, 18 figures, Accepted version, Fortschritte der Physik | Fortschritte der Physik, 70, 2100065, 2022 | 10.1002/prop.202100065 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have presented a bouncing cosmological model of the
Universe in an extended theory of gravity. The dynamical behaviour of the model
obtained from the flat FLRW space-time along with the violation of null energy
condition have been shown. The geometrical parameters show singularity
behaviour at the bouncing epoch. The parameters involved in the scale factor
play a major role in the bouncing behaviour. In addition, the coupling
parameter that resulted in the minimal matter-geometry coupling in the extended
gravity has significant role to avoid the singularity of equation of state
parameter at the bouncing epoch. Using a linear homogeneous perturbation
calculation, we show the stability of the model.
| [
{
"created": "Tue, 2 Nov 2021 14:18:06 GMT",
"version": "v1"
}
] | 2022-04-22 | [
[
"Agrawal",
"A. S.",
""
],
[
"Tello-Ortiz",
"Francisco",
""
],
[
"Mishra",
"B.",
""
],
[
"Tripathy",
"S. K.",
""
]
] | In this paper, we have presented a bouncing cosmological model of the Universe in an extended theory of gravity. The dynamical behaviour of the model obtained from the flat FLRW space-time along with the violation of null energy condition have been shown. The geometrical parameters show singularity behaviour at the bouncing epoch. The parameters involved in the scale factor play a major role in the bouncing behaviour. In addition, the coupling parameter that resulted in the minimal matter-geometry coupling in the extended gravity has significant role to avoid the singularity of equation of state parameter at the bouncing epoch. Using a linear homogeneous perturbation calculation, we show the stability of the model. |
2401.14849 | Henri Inchausp\'e Dr. | Lavinia Heisenberg, Henri Inchausp\'e, David Maibach | Observing Kinematic Anisotropies of the Stochastic Background with LISA | 18 pages, 11 figures | null | null | null | gr-qc astro-ph.CO astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a diagnostic tool for future analyses of stochastic gravitational
wave background signals of extra-galactic origin in LISA data. Next-generation
gravitational wave detectors hold the capability to track unresolved
gravitational waves bundled into a stochastic background. This composite
background contains cosmological and astrophysical contributions, the
exploration of which offers promising avenues for groundbreaking new insights
into very early universe cosmology as well as late-time structure formation. In
this article, we develop a full end-to-end pipeline for the extraction of
extra-galactic signals, based on kinematic anisotropies arising from the
galactic motion, via full-time-domain simulations of LISA's response to the
gravitational wave anisotropic sky. Employing a Markov-Chain-Monte-Carlo
map-making scheme, multipoles up to $\ell=2$ are recovered for scale-free
spectra that support an interpretation as signals originating from cosmic
strings in the case of a high signal-to-noise ratio. We demonstrate that our
analysis is consistently beating cosmic variance and is robust against
statistical and systematic errors. The impact of instrumental noise on the
extraction of kinematic anisotropies is investigated, and we establish a
detection threshold of $\Omega_{GW}\gtrsim 5\times 10^{-8}$ in the presence of
instrument-induced noise. Potential avenues for improvement in our methodology
are highlighted.
| [
{
"created": "Fri, 26 Jan 2024 13:30:50 GMT",
"version": "v1"
}
] | 2024-01-29 | [
[
"Heisenberg",
"Lavinia",
""
],
[
"Inchauspé",
"Henri",
""
],
[
"Maibach",
"David",
""
]
] | We propose a diagnostic tool for future analyses of stochastic gravitational wave background signals of extra-galactic origin in LISA data. Next-generation gravitational wave detectors hold the capability to track unresolved gravitational waves bundled into a stochastic background. This composite background contains cosmological and astrophysical contributions, the exploration of which offers promising avenues for groundbreaking new insights into very early universe cosmology as well as late-time structure formation. In this article, we develop a full end-to-end pipeline for the extraction of extra-galactic signals, based on kinematic anisotropies arising from the galactic motion, via full-time-domain simulations of LISA's response to the gravitational wave anisotropic sky. Employing a Markov-Chain-Monte-Carlo map-making scheme, multipoles up to $\ell=2$ are recovered for scale-free spectra that support an interpretation as signals originating from cosmic strings in the case of a high signal-to-noise ratio. We demonstrate that our analysis is consistently beating cosmic variance and is robust against statistical and systematic errors. The impact of instrumental noise on the extraction of kinematic anisotropies is investigated, and we establish a detection threshold of $\Omega_{GW}\gtrsim 5\times 10^{-8}$ in the presence of instrument-induced noise. Potential avenues for improvement in our methodology are highlighted. |
gr-qc/0612066 | J. Mark Heinzle | Robert Beig, J. Mark Heinzle, Bernd G. Schmidt | Helically symmetric N-particle solutions in scalar gravity | 5 pages, 1 figure; minor corrections and changes; accepted for
publication in Physical Review Letters | Phys.Rev.Lett.98:121102,2007 | 10.1103/PhysRevLett.98.121102 | null | gr-qc | null | Within a scalar model theory of gravity, where the interaction between
particles is given by the half-retarded + half-advanced solution of the scalar
wave equation, we consider an N-body problem: we investigate configurations of
N particles which form an equilateral N-angle and are in helical motion about
their common center. We prove that there exists a unique equilibrium
configuration and compute the equilibrium radius explicitly in a post-Newtonian
expansion.
| [
{
"created": "Mon, 11 Dec 2006 18:06:20 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Mar 2007 13:49:08 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Beig",
"Robert",
""
],
[
"Heinzle",
"J. Mark",
""
],
[
"Schmidt",
"Bernd G.",
""
]
] | Within a scalar model theory of gravity, where the interaction between particles is given by the half-retarded + half-advanced solution of the scalar wave equation, we consider an N-body problem: we investigate configurations of N particles which form an equilateral N-angle and are in helical motion about their common center. We prove that there exists a unique equilibrium configuration and compute the equilibrium radius explicitly in a post-Newtonian expansion. |
0810.0153 | Yurij Baryshev | Yu. V. Baryshev (Astron.Inst.St.-Petersburg Univ.) | Expanding Space: The Root of Conceptual Problems of the Cosmological
Physics | 11 pages, proceedings of the International conference "Problems of
Practical Cosmology", 23-27 June 2008, St.-Petersburg, Russia, see
http://ppc08.astro.spbu.ru/text_proc.html | in "Practical Cosmology", v.2, pp.20-30, 2008 | null | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The space expansion physics contains several paradoxes which were clearly
demonstrated by Edward Harrison (1981, 1995, 2000), who emphasized that the
cooling of homogeneous hot gas (including photon gas of CBR) in the standard
cosmological model based on the violation of energy conservation by the
expanding space. In modern version of SCM the term "space expansion" actually
means continuous creation of vacuum, something that leads to conceptual
problems. Recent discussion by Francis, Barnes, James, and Lewis (2007) on the
physical sense of the increasing distance to a receding galaxy without motion
of the galaxy is just a particular consequence of the arising paradoxes. Here
we present an analysis of the following conceptual problems of the SCM: the
violation of energy conservation for local comoving volumes, the exact
Newtonian form of the Friedmann equation, the absence of an upper limit on the
receding velocity of galaxies which can be greater than the speed of light, and
the presence of the linear Hubble law deeply inside inhomogeneous galaxy
distribution. The common cause of these paradoxes is the geometrical
description of gravity, where there is no a well defined concept of the
energy-momentum tensor for the gravitational field, no energy quanta -
gravitons, and no energy-momentum conservation for matter plus gravity because
gravity is not a material field.
| [
{
"created": "Wed, 1 Oct 2008 12:57:20 GMT",
"version": "v1"
}
] | 2008-10-02 | [
[
"Baryshev",
"Yu. V.",
"",
"Astron.Inst.St.-Petersburg Univ."
]
] | The space expansion physics contains several paradoxes which were clearly demonstrated by Edward Harrison (1981, 1995, 2000), who emphasized that the cooling of homogeneous hot gas (including photon gas of CBR) in the standard cosmological model based on the violation of energy conservation by the expanding space. In modern version of SCM the term "space expansion" actually means continuous creation of vacuum, something that leads to conceptual problems. Recent discussion by Francis, Barnes, James, and Lewis (2007) on the physical sense of the increasing distance to a receding galaxy without motion of the galaxy is just a particular consequence of the arising paradoxes. Here we present an analysis of the following conceptual problems of the SCM: the violation of energy conservation for local comoving volumes, the exact Newtonian form of the Friedmann equation, the absence of an upper limit on the receding velocity of galaxies which can be greater than the speed of light, and the presence of the linear Hubble law deeply inside inhomogeneous galaxy distribution. The common cause of these paradoxes is the geometrical description of gravity, where there is no a well defined concept of the energy-momentum tensor for the gravitational field, no energy quanta - gravitons, and no energy-momentum conservation for matter plus gravity because gravity is not a material field. |
gr-qc/0508067 | Yanbei Chen | Alessandra Buonanno, Yanbei Chen and Thibault Damour | Transition from inspiral to plunge in precessing binaries of spinning
black holes | 31 pages, 7 tables, and 13 figures | Phys.Rev.D74:104005,2006 | 10.1103/PhysRevD.74.104005 | null | gr-qc | null | We investigate the non-adiabatic dynamics of spinning black hole binaries by
using an analytical Hamiltonian completed with a radiation-reaction force,
containing spin couplings, which matches the known rates of energy and angular
momentum losses on quasi-circular orbits. We consider both a straightforward
post-Newtonian-expanded Hamiltonian (including spin-dependent terms), and a
version of the resummed post-Newtonian Hamiltonian defined by the Effective
One-Body approach. We focus on the influence of spin terms onto the dynamics
and waveforms. We evaluate the energy and angular momentum released during the
final stage of inspiral and plunge. For an equal-mass binary the energy
released between 40Hz and the frequency beyond which our analytical treatment
becomes unreliable is found to be, when using the more reliable Effective
One-Body dynamics: 0.6% M for anti-aligned maximally spinning black holes, 5% M
for aligned maximally spinning black hole, and 1.8% M for non-spinning
configurations. In confirmation of previous results, we find that, for all
binaries considered, the dimensionless rotation parameter J/E^2 is always
smaller than unity at the end of the inspiral, so that a Kerr black hole can
form right after the inspiral phase. By matching a quasi-normal mode ringdown
to the last reliable stages of the plunge, we construct complete waveforms
approximately describing the gravitational wave signal emitted by the entire
process of coalescence of precessing binaries of spinning black holes.
| [
{
"created": "Tue, 16 Aug 2005 21:49:04 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Buonanno",
"Alessandra",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Damour",
"Thibault",
""
]
] | We investigate the non-adiabatic dynamics of spinning black hole binaries by using an analytical Hamiltonian completed with a radiation-reaction force, containing spin couplings, which matches the known rates of energy and angular momentum losses on quasi-circular orbits. We consider both a straightforward post-Newtonian-expanded Hamiltonian (including spin-dependent terms), and a version of the resummed post-Newtonian Hamiltonian defined by the Effective One-Body approach. We focus on the influence of spin terms onto the dynamics and waveforms. We evaluate the energy and angular momentum released during the final stage of inspiral and plunge. For an equal-mass binary the energy released between 40Hz and the frequency beyond which our analytical treatment becomes unreliable is found to be, when using the more reliable Effective One-Body dynamics: 0.6% M for anti-aligned maximally spinning black holes, 5% M for aligned maximally spinning black hole, and 1.8% M for non-spinning configurations. In confirmation of previous results, we find that, for all binaries considered, the dimensionless rotation parameter J/E^2 is always smaller than unity at the end of the inspiral, so that a Kerr black hole can form right after the inspiral phase. By matching a quasi-normal mode ringdown to the last reliable stages of the plunge, we construct complete waveforms approximately describing the gravitational wave signal emitted by the entire process of coalescence of precessing binaries of spinning black holes. |
gr-qc/0209052 | Mihalis Dafermos | Mihalis Dafermos | Stability and Instability of the Reissner-Nordstrom Cauchy Horizon and
the Problem of Uniqueness in General Relativity | 18 pages, 13 figures Talk given at Rutgers in "Conference on
Non-compact Variational Problems and General Relativity" in honor of Haim
Brezis and Felix Browder | Contemp. Math. 350 (2004), 99--113 | null | null | gr-qc | null | This talk describes some recent results [16] regarding the problem of
uniqueness in the large (also known as strong cosmic censorship) for the
initial value problem in general relativity. In order to isolate the essential
analytic features of the problem from the complicated setting of gravitational
collapse in which it arises, some familiarity with conformal properties of
certain celebrated special solutions of the theory of relativity will have to
be developed. This talk is an attempt to present precisely these features to an
audience of non-specialists, in a way which will hopefully fully motivate a
certain characteristic initial value problem for the spherically-symmetric
Einstein-Maxwell-Scalar Field system. The considerations outlined here leading
to this particular initial value problem are well known in the physics
relativity community, where the problem of uniqueness has been studied
heuristically [1, 22] and numerically [2, 3]. In [16], the global behavior of
solutions to this IVP, in particular, the issue of uniqueness, is
mathematically completely understood. A statement of the relevant Theorems is
included in Section 9. Only a sketch of the ideas of the proof is provided
here, but the readers may refer to [16] for details.
| [
{
"created": "Tue, 17 Sep 2002 14:13:54 GMT",
"version": "v1"
}
] | 2011-10-13 | [
[
"Dafermos",
"Mihalis",
""
]
] | This talk describes some recent results [16] regarding the problem of uniqueness in the large (also known as strong cosmic censorship) for the initial value problem in general relativity. In order to isolate the essential analytic features of the problem from the complicated setting of gravitational collapse in which it arises, some familiarity with conformal properties of certain celebrated special solutions of the theory of relativity will have to be developed. This talk is an attempt to present precisely these features to an audience of non-specialists, in a way which will hopefully fully motivate a certain characteristic initial value problem for the spherically-symmetric Einstein-Maxwell-Scalar Field system. The considerations outlined here leading to this particular initial value problem are well known in the physics relativity community, where the problem of uniqueness has been studied heuristically [1, 22] and numerically [2, 3]. In [16], the global behavior of solutions to this IVP, in particular, the issue of uniqueness, is mathematically completely understood. A statement of the relevant Theorems is included in Section 9. Only a sketch of the ideas of the proof is provided here, but the readers may refer to [16] for details. |
1706.08846 | Riaz Ahmed | G. Abbas, Riaz Ahmed | Models of Collapsing and Expanding Anisotropic Gravitating Source in
$f(R,T)$ Theory of Gravity | 18 Pages, 8 Figures, Accepted for Publication in European Physical
Journal C | null | 10.1140/epjc/s10052-017-5025-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have formulated the exact solutions of the non-static
anisotropic gravitating source in $f(R,T)$ gravity which may lead to expansion
and collapse. By assuming the no thermal conduction in gravitating source, we
have determine parametric solutions in $f(R,T)$ gravity with non-static
spherical geometry filled with anisotropic fluid. We have examined the range of
parameter for which expansion scalar become negative and positive leading to
collapse and expansion, respectively. Further, using the definition of mass
function the condition for the trapped surface have been explored and it has
been investigated there exists a single horizon in this case. The impact of
coupling parameter $\lambda$ has been discussed in detail in both cases. For
the various values of coupling parameter $\lambda$, we have plotted energy
density, anisotropic pressure and anisotropic parameter in case of collapse and
expansion. The physical significance of the graphs has been explained in
detail.
| [
{
"created": "Sat, 24 Jun 2017 08:15:28 GMT",
"version": "v1"
}
] | 2017-08-02 | [
[
"Abbas",
"G.",
""
],
[
"Ahmed",
"Riaz",
""
]
] | In this paper, we have formulated the exact solutions of the non-static anisotropic gravitating source in $f(R,T)$ gravity which may lead to expansion and collapse. By assuming the no thermal conduction in gravitating source, we have determine parametric solutions in $f(R,T)$ gravity with non-static spherical geometry filled with anisotropic fluid. We have examined the range of parameter for which expansion scalar become negative and positive leading to collapse and expansion, respectively. Further, using the definition of mass function the condition for the trapped surface have been explored and it has been investigated there exists a single horizon in this case. The impact of coupling parameter $\lambda$ has been discussed in detail in both cases. For the various values of coupling parameter $\lambda$, we have plotted energy density, anisotropic pressure and anisotropic parameter in case of collapse and expansion. The physical significance of the graphs has been explained in detail. |
2105.00881 | Cosimo Bambi | Cosimo Bambi, Dejan Stojkovic | Astrophysical Wormholes | 13 pages, 9 figures. Invited contribution to the special issue of
Universe "Recent Advances in Wormhole Physics" (Eds. K.A. Bronnikov and S.
Sushkov). Partially based on e-Print 2010.03947 [gr-qc], e-Print 2007.12184
[gr-qc], e-Print 1910.00429 [gr-qc], e-Print 1810.03432 [hep-th]. v2: added
some references | Universe (2021) 7:136 | 10.3390/universe7050136 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wormholes are hypothetical topologically-non-trivial structures of the
spacetime. From the theoretical point of view, the possibility of their
existence is challenging but cannot be ruled out. This article is a compact and
non-exhaustive review of past and current efforts to search for astrophysical
wormholes in the Universe.
| [
{
"created": "Mon, 3 May 2021 14:05:17 GMT",
"version": "v1"
},
{
"created": "Sat, 8 May 2021 09:52:12 GMT",
"version": "v2"
}
] | 2021-05-11 | [
[
"Bambi",
"Cosimo",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | Wormholes are hypothetical topologically-non-trivial structures of the spacetime. From the theoretical point of view, the possibility of their existence is challenging but cannot be ruled out. This article is a compact and non-exhaustive review of past and current efforts to search for astrophysical wormholes in the Universe. |
2109.05481 | Luca Visinelli | Luca Visinelli | Boson Stars and Oscillatons: A Review | 48 pages, 4 figures, 2 tables. Matches the version accepted for
publication on IJMPD | Int. J. Mod. Phys. D Vol. 30, Issue 15, No. 2130006 (2021) | 10.1142/S0218271821300068 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Compact objects occupy a pivotal role in the exploration of Nature. The
interest spans from the role of compact objects in astrophysics to their
detection through various methods (gravitational waves interferometry,
microlensing, imaging). While the existence of compact objects made of fermions
(neutron stars and white dwarfs) has been assessed, a parallel search for
localized solitons made of bosons is ongoing, stemming from Wheeler's original
proposal of electromagnetic "geons". Boson fields can clump up and form compact
objects such as boson stars (for complex scalar fields), oscillons and
oscillatons (for real scalar fields), or Proca stars (for massive vector
fields), which can show up in searches as black hole mimickers, dark matter
sources, and a variety of other phenomena. I review some crucial properties of
these bosonic systems, including recent progress in the field.
| [
{
"created": "Sun, 12 Sep 2021 10:23:13 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Oct 2021 09:25:40 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Jan 2023 05:47:33 GMT",
"version": "v3"
}
] | 2023-01-13 | [
[
"Visinelli",
"Luca",
""
]
] | Compact objects occupy a pivotal role in the exploration of Nature. The interest spans from the role of compact objects in astrophysics to their detection through various methods (gravitational waves interferometry, microlensing, imaging). While the existence of compact objects made of fermions (neutron stars and white dwarfs) has been assessed, a parallel search for localized solitons made of bosons is ongoing, stemming from Wheeler's original proposal of electromagnetic "geons". Boson fields can clump up and form compact objects such as boson stars (for complex scalar fields), oscillons and oscillatons (for real scalar fields), or Proca stars (for massive vector fields), which can show up in searches as black hole mimickers, dark matter sources, and a variety of other phenomena. I review some crucial properties of these bosonic systems, including recent progress in the field. |
1303.1762 | Jason Bates | Jason D. Bates | Stochastic Force Due to a Quantum Scalar Field in Minkowski Spacetime | 14 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method is presented for computing approximate expressions for the
stochastic force term $\xi_{ab}$ which appears in the Einstein-Langevin
equation of stochastic gravity. Within this framework, $\xi_{ab}$ is a
stochastic tensor field whose probability distribution mimics the probability
distribution of the fluctuations of the quantum stress tensor operator; it is
defined to be a random tensor field of zero mean whose correlation function is
given by the expectation value of the symmetrized two point function of the
stress energy fluctuation operator, called the noise kernel. Approximate
expressions are obtained by means of a truncated Karhunen-Loeve transform
defined on a random lattice of spacetime points. Due to the singular nature of
the noise kernel, a coarse graining procedure is used to regulate divergences;
as a result, the expressions obtained for $\xi_{ab}$ approximate values which
might be seen by a probe measuring fluctuations in the stress energy using a
sampling profile of finite width. Two realizations of $\xi_{ab}$ in Minkowski
spacetime for the conformally invariant quantum scalar field in the Minkowski
vacuum state are presented.
| [
{
"created": "Thu, 7 Mar 2013 17:39:53 GMT",
"version": "v1"
}
] | 2013-03-08 | [
[
"Bates",
"Jason D.",
""
]
] | A method is presented for computing approximate expressions for the stochastic force term $\xi_{ab}$ which appears in the Einstein-Langevin equation of stochastic gravity. Within this framework, $\xi_{ab}$ is a stochastic tensor field whose probability distribution mimics the probability distribution of the fluctuations of the quantum stress tensor operator; it is defined to be a random tensor field of zero mean whose correlation function is given by the expectation value of the symmetrized two point function of the stress energy fluctuation operator, called the noise kernel. Approximate expressions are obtained by means of a truncated Karhunen-Loeve transform defined on a random lattice of spacetime points. Due to the singular nature of the noise kernel, a coarse graining procedure is used to regulate divergences; as a result, the expressions obtained for $\xi_{ab}$ approximate values which might be seen by a probe measuring fluctuations in the stress energy using a sampling profile of finite width. Two realizations of $\xi_{ab}$ in Minkowski spacetime for the conformally invariant quantum scalar field in the Minkowski vacuum state are presented. |
1603.00362 | William G. Cook | William G. Cook, Pau Figueras, Markus Kunesch, Ulrich Sperhake, Saran
Tunyasuvunakool | Dimensional reduction in numerical relativity: Modified cartoon
formalism and regularization | 25 pages, 2 figures, Special Issue on Selected Papers of the III
Amazonian Symposium on Physics | null | 10.1142/S0218271816410133 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present in detail the Einstein equations in the
Baumgarte-Shapiro-Shibata-Nakamura formulation for the case of $D$ dimensional
spacetimes with $SO(D-d)$ isometry based on a method originally introduced in
Ref.1. Regularized expressions are given for a numerical implementation of this
method on a vertex centered grid including the origin of the quasi-radial
coordinate that covers the extra dimensions with rotational symmetry.
Axisymmetry, corresponding to the value $d=D-2$, represents a special case with
fewer constraints on the vanishing of tensor components and is conveniently
implemented in a variation of the general method. The robustness of the scheme
is demonstrated for the case of a black-hole head-on collision in $D=7$
spacetime dimensions with $SO(4)$ symmetry.
| [
{
"created": "Tue, 1 Mar 2016 17:11:10 GMT",
"version": "v1"
}
] | 2016-08-17 | [
[
"Cook",
"William G.",
""
],
[
"Figueras",
"Pau",
""
],
[
"Kunesch",
"Markus",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Tunyasuvunakool",
"Saran",
""
]
] | We present in detail the Einstein equations in the Baumgarte-Shapiro-Shibata-Nakamura formulation for the case of $D$ dimensional spacetimes with $SO(D-d)$ isometry based on a method originally introduced in Ref.1. Regularized expressions are given for a numerical implementation of this method on a vertex centered grid including the origin of the quasi-radial coordinate that covers the extra dimensions with rotational symmetry. Axisymmetry, corresponding to the value $d=D-2$, represents a special case with fewer constraints on the vanishing of tensor components and is conveniently implemented in a variation of the general method. The robustness of the scheme is demonstrated for the case of a black-hole head-on collision in $D=7$ spacetime dimensions with $SO(4)$ symmetry. |
2107.12430 | Vasilis Oikonomou | V.K. Oikonomou | Universal Inflationary Attractors Implications on Static Neutron Stars | CQG Accepted | null | 10.1088/1361-6382/ac161c | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study static neutron stars in the context of a class of non-minimally
coupled inflationary potentials, the universal attractors. Universal attractors
are known to generate a viable inflationary era, and they fall into the same
category of inflationary phenomenology as the $R^2$ model and other well-known
cosmological attractors. We present the essential features of universal
attractors in both the Einstein and Jordan frame, and we extract the
Tolman-Oppenheimer-Volkoff equations in the Einstein frame using the usual
notation of theoretical astrophysics. We use a python 3 based double shooting
numerical code for our numerical analysis and we construct the $M-R$ graphs for
the universal attractor potential, using piecewise polytropic equation of state
the small density part of which is the WFF1 or the APR or the SLy equation of
state. As we show, all the studied cases predict larger maximum masses for the
neutron stars, and all the results are compatible with the GW170817 constraints
imposed on the radii of the neutron stars.
| [
{
"created": "Mon, 26 Jul 2021 18:46:00 GMT",
"version": "v1"
}
] | 2021-09-01 | [
[
"Oikonomou",
"V. K.",
""
]
] | We study static neutron stars in the context of a class of non-minimally coupled inflationary potentials, the universal attractors. Universal attractors are known to generate a viable inflationary era, and they fall into the same category of inflationary phenomenology as the $R^2$ model and other well-known cosmological attractors. We present the essential features of universal attractors in both the Einstein and Jordan frame, and we extract the Tolman-Oppenheimer-Volkoff equations in the Einstein frame using the usual notation of theoretical astrophysics. We use a python 3 based double shooting numerical code for our numerical analysis and we construct the $M-R$ graphs for the universal attractor potential, using piecewise polytropic equation of state the small density part of which is the WFF1 or the APR or the SLy equation of state. As we show, all the studied cases predict larger maximum masses for the neutron stars, and all the results are compatible with the GW170817 constraints imposed on the radii of the neutron stars. |
1902.01386 | Jonathan Engle | Jonathan Engle and Ilya Vilensky | Uniqueness of minimal loop quantum cosmology dynamics | 6 pages; references added, minor revisions of phrasing | Phys. Rev. D 100, 121901 (2019) | 10.1103/PhysRevD.100.121901 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the standard Hamiltonian of isotropic loop quantum cosmology is
selected by physical criteria plus one choice: that it have a `minimal' number
of terms. We also show the freedom, and boundedness of energy density, even
when this choice is relaxed. A criterion used is covariance under dilations,
the continuous diffeomorphisms remaining in this context, which are not
canonical but conformally canonical transformations. We propose how to
implement conformally canonical transformations in quantum theory. Removal of
the infrared regulator yields independence of ordering ambiguities.
| [
{
"created": "Mon, 4 Feb 2019 18:53:25 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Feb 2019 19:10:40 GMT",
"version": "v2"
}
] | 2019-12-25 | [
[
"Engle",
"Jonathan",
""
],
[
"Vilensky",
"Ilya",
""
]
] | We show that the standard Hamiltonian of isotropic loop quantum cosmology is selected by physical criteria plus one choice: that it have a `minimal' number of terms. We also show the freedom, and boundedness of energy density, even when this choice is relaxed. A criterion used is covariance under dilations, the continuous diffeomorphisms remaining in this context, which are not canonical but conformally canonical transformations. We propose how to implement conformally canonical transformations in quantum theory. Removal of the infrared regulator yields independence of ordering ambiguities. |
1007.2499 | Mehrdad Farhoudi Dr. | Behrooz Malekolkalami and Mehrdad Farhoudi | Noncommutative Double Scalar Fields in FRW Cosmology as Cosmical
Oscillators | 21 pages, 5 figures | Class.Quant.Grav.27:245009,2010 | 10.1088/0264-9381/27/24/245009 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate effects of noncommutativity of phase space generated by two
scalar fields conformally coupled to curvature in FRW cosmology. We restrict
deformation of minisuperspace to noncommutativity between scalar fields and
between their canonical conjugate momenta. The investigation is carried out by
means of comparative analysis of mathematical properties of time evolution of
variables in classical model and wave function of universe in quantum level. We
find that impose of noncommutativity causes more ability in tuning time
solutions of scalar fields and hence, has important implications in evolution
of universe. We get that noncommutative parameter in momenta sector is the only
responsible parameter for noncommutative effects in flat universes. A
distinguishing feature of noncommutative solutions of scalar fields is that
they can be simulated with well known harmonic oscillators, depend on values of
spatial curvature. Namely free, forced and damped harmonic oscillators
corresponding to flat, closed and open universes. In this respect, we call them
cosmical oscillators. In closed universes, when noncommutative parameters are
small, cosmical oscillators have analogous effect with familiar beating effect
in sound phenomenon. The existence of non-zero constant potential does not
change solutions of scalar fields, but modifies scale factor. An interesting
feature of well behaved solutions of wave functions is that functional form of
its radial part is the same as commutative ones provided that given replacement
of constants, caused by noncommutative parameters, is performed. Further,
Noether theorem has been employed to explore effects of noncommutativity on
underlying symmetries in commutative frame. Two of six Noether symmetries of
flat universes, in general, are retained in noncommutative case, and one out of
three ones in non flat universes.
| [
{
"created": "Thu, 15 Jul 2010 08:06:15 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Nov 2010 16:57:20 GMT",
"version": "v2"
}
] | 2010-11-30 | [
[
"Malekolkalami",
"Behrooz",
""
],
[
"Farhoudi",
"Mehrdad",
""
]
] | We investigate effects of noncommutativity of phase space generated by two scalar fields conformally coupled to curvature in FRW cosmology. We restrict deformation of minisuperspace to noncommutativity between scalar fields and between their canonical conjugate momenta. The investigation is carried out by means of comparative analysis of mathematical properties of time evolution of variables in classical model and wave function of universe in quantum level. We find that impose of noncommutativity causes more ability in tuning time solutions of scalar fields and hence, has important implications in evolution of universe. We get that noncommutative parameter in momenta sector is the only responsible parameter for noncommutative effects in flat universes. A distinguishing feature of noncommutative solutions of scalar fields is that they can be simulated with well known harmonic oscillators, depend on values of spatial curvature. Namely free, forced and damped harmonic oscillators corresponding to flat, closed and open universes. In this respect, we call them cosmical oscillators. In closed universes, when noncommutative parameters are small, cosmical oscillators have analogous effect with familiar beating effect in sound phenomenon. The existence of non-zero constant potential does not change solutions of scalar fields, but modifies scale factor. An interesting feature of well behaved solutions of wave functions is that functional form of its radial part is the same as commutative ones provided that given replacement of constants, caused by noncommutative parameters, is performed. Further, Noether theorem has been employed to explore effects of noncommutativity on underlying symmetries in commutative frame. Two of six Noether symmetries of flat universes, in general, are retained in noncommutative case, and one out of three ones in non flat universes. |
1311.2379 | Salvador Robles-Perez | Salvador J. Robles-P\'erez | Creation of entangled universes avoids the big bang singularity | 11 pages, 5 figures | Journal of Gravity (2014), 382675 | 10.1155/2014/382675 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The creation of universes in entangled pairs may avoid the initial
singularity and it would have observable consequences in a large macroscopic
universe like ours, at least in principle. In this paper we describe the
creation of an entangled pair of universes from a double instanton, which
avoids the initial singularity, in the case of a homogeneous and isotropic
universe with a conformally coupled massless scalar field. The thermodynamical
properties of inter-universal entanglement might have observable consequences
on the properties of our single universe provided that the thermodynamics of
entanglement is eventually related to the classical formulation of
thermodynamics.
| [
{
"created": "Mon, 11 Nov 2013 08:34:22 GMT",
"version": "v1"
}
] | 2017-08-04 | [
[
"Robles-Pérez",
"Salvador J.",
""
]
] | The creation of universes in entangled pairs may avoid the initial singularity and it would have observable consequences in a large macroscopic universe like ours, at least in principle. In this paper we describe the creation of an entangled pair of universes from a double instanton, which avoids the initial singularity, in the case of a homogeneous and isotropic universe with a conformally coupled massless scalar field. The thermodynamical properties of inter-universal entanglement might have observable consequences on the properties of our single universe provided that the thermodynamics of entanglement is eventually related to the classical formulation of thermodynamics. |
1310.5115 | Theodore A. Jacobson | Ted Jacobson | Undoing the twist: the Ho\v{r}ava limit of Einstein-aether | 5 pages; v2: added discussion of inferences from the general form of
the action, changed normalization of expansion coupling coefficient to
simplify formulas, nearly coincides with PRD version | null | 10.1103/PhysRevD.89.081501 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Ho\v{r}ava gravity can be obtained from Einstein-aether theory
in the limit that the twist coupling constant goes to infinity, while holding
fixed the expansion, shear and acceleration couplings. This limit helps to
clarify the relation between the two theories, and allows Ho\v{r}ava results to
be obtained from Einstein-aether ones. The limit is illustrated with several
examples, including rotating black hole equations, PPN parameters, and
radiation rates from binary systems.
| [
{
"created": "Fri, 18 Oct 2013 18:10:42 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Mar 2014 19:50:28 GMT",
"version": "v2"
}
] | 2015-06-17 | [
[
"Jacobson",
"Ted",
""
]
] | We show that Ho\v{r}ava gravity can be obtained from Einstein-aether theory in the limit that the twist coupling constant goes to infinity, while holding fixed the expansion, shear and acceleration couplings. This limit helps to clarify the relation between the two theories, and allows Ho\v{r}ava results to be obtained from Einstein-aether ones. The limit is illustrated with several examples, including rotating black hole equations, PPN parameters, and radiation rates from binary systems. |
1508.06986 | Nicholas Tacik | Nick Tacik, Francois Foucart, Harald P. Pfeiffer, Roland Haas, Serguei
Ossokine, Jeff Kaplan, Curran Muhlberger, Matt D. Duez, Lawrence E. Kidder,
Mark A. Scheel, B\'ela Szil\'agyi | Binary Neutron Stars with Arbitrary Spins in Numerical Relativity | 20 pages, 22 figures | Phys. Rev. D 92, 124012 (2015) | 10.1103/PhysRevD.92.124012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a code to construct initial data for binary neutron star systems
in which the stars are rotating. Our code, based on a formalism developed by
Tichy, allows for arbitrary rotation axes of the neutron stars and is able to
achieve rotation rates near rotational breakup. We compute the neutron star
angular momentum through quasi-local angular momentum integrals. When
constructing irrotational binary neutron stars, we find a very small residual
dimensionless spin of $\sim 2\times 10^{-4}$. Evolutions of rotating neutron
star binaries show that the magnitude of the stars' angular momentum is
conserved, and that the spin- and orbit-precession of the stars is well
described by post-Newtonian approximation. We demonstrate that orbital
eccentricity of the binary neutron stars can be controlled to $\sim 0.1\%$. The
neutron stars show quasi-normal mode oscillations at an amplitude which
increases with the rotation rate of the stars.
| [
{
"created": "Thu, 27 Aug 2015 19:56:36 GMT",
"version": "v1"
}
] | 2016-08-08 | [
[
"Tacik",
"Nick",
""
],
[
"Foucart",
"Francois",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Haas",
"Roland",
""
],
[
"Ossokine",
"Serguei",
""
],
[
"Kaplan",
"Jeff",
""
],
[
"Muhlberger",
"Curran",
""
],
... | We present a code to construct initial data for binary neutron star systems in which the stars are rotating. Our code, based on a formalism developed by Tichy, allows for arbitrary rotation axes of the neutron stars and is able to achieve rotation rates near rotational breakup. We compute the neutron star angular momentum through quasi-local angular momentum integrals. When constructing irrotational binary neutron stars, we find a very small residual dimensionless spin of $\sim 2\times 10^{-4}$. Evolutions of rotating neutron star binaries show that the magnitude of the stars' angular momentum is conserved, and that the spin- and orbit-precession of the stars is well described by post-Newtonian approximation. We demonstrate that orbital eccentricity of the binary neutron stars can be controlled to $\sim 0.1\%$. The neutron stars show quasi-normal mode oscillations at an amplitude which increases with the rotation rate of the stars. |
gr-qc/9907039 | Brandon Carter | Brandon Carter | Vortex Dynamics in Superfluids | 39 pages, Latex; contrib. to `Topological defects and non-equilibrium
dynamics of phase transitions' ed Y. Bunkov, H. Godfrin, Les Houches Winter
School, February 1999 | null | null | null | gr-qc | null | Superfluid condensates are known to occur in contexts ranging from laboratory
liquid helium to neutron stars, and are also likely to occur in cosmological
phenomena such as axion fields. In the zero temperature limit, such condensates
are describable at a mesoscopic level by irrotational configurations of simple
relativistic perfect fluid models. The general mechanical properties of such
models are presented here in an introductory review giving special attention to
the dynamics of vorticity flux 2-surfaces and the action principles governing
both individual flow trajetories and the evolution of the system as a whole.
Macroscopic rotation of such a condensate requires the presence of a lattice of
quantised vortex defects, whose averaged tension violates perfect fluid
isotropy. It is shown that for any equation of state (relating the mass density
$\rho$ to the pressure $P$) the mesoscopic perfect fluid model can be extended
in a uniquely simple and natural manner to a corresponding macroscopic model
(in a conformally covariant category) that represents the effects of the vortex
fibration anisotropy. The limiting case of an individual vortex defect is shown
to be describable by a (``global'') string type model with a variable tension
${\cal T}$ (obtained as a function of the background fluid density) whose
``vorton'' (i.e. closed loop equilibrium) states are derived as an exercise.
| [
{
"created": "Fri, 9 Jul 1999 14:08:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Carter",
"Brandon",
""
]
] | Superfluid condensates are known to occur in contexts ranging from laboratory liquid helium to neutron stars, and are also likely to occur in cosmological phenomena such as axion fields. In the zero temperature limit, such condensates are describable at a mesoscopic level by irrotational configurations of simple relativistic perfect fluid models. The general mechanical properties of such models are presented here in an introductory review giving special attention to the dynamics of vorticity flux 2-surfaces and the action principles governing both individual flow trajetories and the evolution of the system as a whole. Macroscopic rotation of such a condensate requires the presence of a lattice of quantised vortex defects, whose averaged tension violates perfect fluid isotropy. It is shown that for any equation of state (relating the mass density $\rho$ to the pressure $P$) the mesoscopic perfect fluid model can be extended in a uniquely simple and natural manner to a corresponding macroscopic model (in a conformally covariant category) that represents the effects of the vortex fibration anisotropy. The limiting case of an individual vortex defect is shown to be describable by a (``global'') string type model with a variable tension ${\cal T}$ (obtained as a function of the background fluid density) whose ``vorton'' (i.e. closed loop equilibrium) states are derived as an exercise. |
0910.4073 | Christian L\"ubbe | C. L\"ubbe, J.A. Valiente Kroon | A stability result for purely radiative spacetimes | 25 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An existence and stability result for a class of purely radiative vacuum
spacetimes arising from hyperboloidal data is given. This result generalises
semiglobal existence results for Minkowski-like spacetimes to the case where
the reference solution contains gravitational radiation. The analysis makes use
of the extended conformal field equations and a gauge based on conformal
geodesics so that the location and structure of the conformal boundary of the
perturbed solutions is known a priori.
| [
{
"created": "Wed, 21 Oct 2009 12:37:26 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Lübbe",
"C.",
""
],
[
"Kroon",
"J. A. Valiente",
""
]
] | An existence and stability result for a class of purely radiative vacuum spacetimes arising from hyperboloidal data is given. This result generalises semiglobal existence results for Minkowski-like spacetimes to the case where the reference solution contains gravitational radiation. The analysis makes use of the extended conformal field equations and a gauge based on conformal geodesics so that the location and structure of the conformal boundary of the perturbed solutions is known a priori. |
gr-qc/0611030 | Stefano Vitale | Ludovico Carbone, Giacomo Ciani, Rita Dolesi, Mauro Hueller, David
Tombolato, Stefano Vitale, and William Joseph Weber (Department of Physics,
University of Trento and INFN, Gruppo Collegato di Trento, Italy) Antonella
Cavalleri (Istituto di Fotonica e Nanotecnologie CNR-ITC and INFN Gruppo
Collegato di Trento, Italy) | Upper limits to surface force disturbances on LISA proof masses and the
possibility of observing galactic binaries | 3 Figures. Submitted to Physical Review Letters | Phys.Rev.D75:042001,2007 | 10.1103/PhysRevD.75.042001 | null | gr-qc | null | We report on the measurement of parasitic surface force noise on a hollow
replica of a LISA (Laser Interferometer Space Antenna for the observation of
gravitational waves) proof mass surrounded by a faithful representation of its
in flight surroundings, namely the capacitive sensor used to detect proof-mass
motion. Parasitic forces are detected through the corresponding torque exerted
on the proof mass and measured with a torsion pendulum in the frequency range
0.1 30 mHz. The sensor electrodes, electrode housing and associated readout
electronics have the same nominal design as for the flight hardware, including
4 mm gaps around the proof mass along the sensitive laser interferometry axis.
We show that the measured upper limit for surface forces would allow detection
of a number of galactic binaries signals with signal to noise ratio up to
approximately 40 for 1 year integration. We also discuss how the flight test
under development, LISA Pathfinder, will substantially improve this limit,
approaching the performance required for LISA.
| [
{
"created": "Sun, 5 Nov 2006 09:15:18 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Nov 2006 09:23:59 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Carbone",
"Ludovico",
"",
"Department of Physics,\n University of Trento and INFN, Gruppo Collegato di Trento, Italy"
],
[
"Ciani",
"Giacomo",
"",
"Department of Physics,\n University of Trento and INFN, Gruppo Collegato di Trento, Italy"
],
[
"Dolesi",
"Rita",
... | We report on the measurement of parasitic surface force noise on a hollow replica of a LISA (Laser Interferometer Space Antenna for the observation of gravitational waves) proof mass surrounded by a faithful representation of its in flight surroundings, namely the capacitive sensor used to detect proof-mass motion. Parasitic forces are detected through the corresponding torque exerted on the proof mass and measured with a torsion pendulum in the frequency range 0.1 30 mHz. The sensor electrodes, electrode housing and associated readout electronics have the same nominal design as for the flight hardware, including 4 mm gaps around the proof mass along the sensitive laser interferometry axis. We show that the measured upper limit for surface forces would allow detection of a number of galactic binaries signals with signal to noise ratio up to approximately 40 for 1 year integration. We also discuss how the flight test under development, LISA Pathfinder, will substantially improve this limit, approaching the performance required for LISA. |
1704.03340 | Pavel Friedrich | Tomislav Prokopec and Pavel Friedrich | Scalar field dark matter in hybrid approach | This version matches the one accepted for publication in Physical
Review D. There are some minor changes with respect to the previous version | Phys. Rev. D 96, 083504 (2017) | 10.1103/PhysRevD.96.083504 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a hybrid formalism suitable for modeling scalar field dark matter,
in which the phase-space distribution associated to the real scalar field is
modeled by statistical equal-time two-point functions and gravity is treated by
two stochastic gravitational fields in the longitudinal gauge (in this work we
neglect vector and tensor gravitational perturbations). Inspired by the
commonly used Newtonian Vlasov-Poisson system, we firstly identify a suitable
combination of equal-time two-point functions that defines the phase-space
distribution associated to the scalar field and then derive both a kinetic
equation that contains relativistic scalar matter corrections as well as linear
gravitational scalar field equations whose sources can be expressed in terms of
a momentum integral over the phase-space distribution function. Our treatment
generalizes the commonly used classical scalar field formalism, in that it
allows for modeling of (dynamically generated) vorticity and perturbations in
anisotropic stresses of the scalar field. It also allows for a systematic
inclusion of relativistic and higher order corrections that may be used to
distinguish different dark matter scenarios. We also provide initial conditions
for the statistical equal-time two-point functions of the matter scalar field
in terms of gravitational potentials and the scale factor.
| [
{
"created": "Mon, 10 Apr 2017 14:54:27 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Sep 2017 12:00:55 GMT",
"version": "v2"
}
] | 2017-10-04 | [
[
"Prokopec",
"Tomislav",
""
],
[
"Friedrich",
"Pavel",
""
]
] | We develop a hybrid formalism suitable for modeling scalar field dark matter, in which the phase-space distribution associated to the real scalar field is modeled by statistical equal-time two-point functions and gravity is treated by two stochastic gravitational fields in the longitudinal gauge (in this work we neglect vector and tensor gravitational perturbations). Inspired by the commonly used Newtonian Vlasov-Poisson system, we firstly identify a suitable combination of equal-time two-point functions that defines the phase-space distribution associated to the scalar field and then derive both a kinetic equation that contains relativistic scalar matter corrections as well as linear gravitational scalar field equations whose sources can be expressed in terms of a momentum integral over the phase-space distribution function. Our treatment generalizes the commonly used classical scalar field formalism, in that it allows for modeling of (dynamically generated) vorticity and perturbations in anisotropic stresses of the scalar field. It also allows for a systematic inclusion of relativistic and higher order corrections that may be used to distinguish different dark matter scenarios. We also provide initial conditions for the statistical equal-time two-point functions of the matter scalar field in terms of gravitational potentials and the scale factor. |
2302.03704 | Conor Dyson | Conor Dyson, Maarten van de Meent | Kerr-fully Diving into the Abyss: Analytic Solutions to Plunging
Geodesics in Kerr | 22 pages, 7 Figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present closed-form solutions for plunging geodesics in the extended Kerr
spacetime using Boyer-Lindquist coordinates. Our solutions directly solve for
the dynamics of generic timelike plunges, we also specialise to the case of
test particles plunging from a precessing innermost stable circular orbit
(ISSO). We find these solutions in the form of elementary and Jacobi elliptic
functions parameterized by Mino time. In particular, we demonstrate that
solutions for the ISSO case can be determined almost entirely in terms of
elementary functions, depending only on the spin parameter of the black hole
and the radius of the ISSO. This extends recent work on the case of equatorial
plunges from the innermost stable circular orbit. Furthermore, we introduce a
new equation that characterizes the radial inflow from the ISSO to the horizon,
taking into account the inclination. For ease of application, our results have
been implemented in the KerrGeodesics package in the Black Hole Perturbation
Toolkit.
| [
{
"created": "Tue, 7 Feb 2023 19:00:12 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Aug 2023 17:39:29 GMT",
"version": "v2"
}
] | 2023-08-15 | [
[
"Dyson",
"Conor",
""
],
[
"van de Meent",
"Maarten",
""
]
] | We present closed-form solutions for plunging geodesics in the extended Kerr spacetime using Boyer-Lindquist coordinates. Our solutions directly solve for the dynamics of generic timelike plunges, we also specialise to the case of test particles plunging from a precessing innermost stable circular orbit (ISSO). We find these solutions in the form of elementary and Jacobi elliptic functions parameterized by Mino time. In particular, we demonstrate that solutions for the ISSO case can be determined almost entirely in terms of elementary functions, depending only on the spin parameter of the black hole and the radius of the ISSO. This extends recent work on the case of equatorial plunges from the innermost stable circular orbit. Furthermore, we introduce a new equation that characterizes the radial inflow from the ISSO to the horizon, taking into account the inclination. For ease of application, our results have been implemented in the KerrGeodesics package in the Black Hole Perturbation Toolkit. |
1101.3591 | Ryan Lang | Ryan N. Lang, Scott A. Hughes, Neil J. Cornish | Measuring parameters of massive black hole binaries with partially
aligned spins | 18 pages, 16 figures, version accepted by PRD (with improved
distributions of partially aligned spins) | Phys.Rev.D84:022002,2011 | 10.1103/PhysRevD.84.022002 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The future space-based gravitational wave detector LISA will be able to
measure parameters of coalescing massive black hole binaries, often to
extremely high accuracy. Previous work has demonstrated that the black hole
spins can have a strong impact on the accuracy of parameter measurement.
Relativistic spin-induced precession modulates the waveform in a manner which
can break degeneracies between parameters, in principle significantly improving
how well they are measured. Recent studies have indicated, however, that spin
precession may be weak for an important subset of astrophysical binary black
holes: those in which the spins are aligned due to interactions with gas. In
this paper, we examine how well a binary's parameters can be measured when its
spins are partially aligned and compare results using waveforms that include
higher post-Newtonian harmonics to those that are truncated at leading
quadrupole order. We find that the weakened precession can substantially
degrade parameter estimation. This degradation is particularly devastating for
the extrinsic parameters sky position and distance. Absent higher harmonics,
LISA typically localizes the sky position of a nearly aligned binary a factor
of $\sim 6$ less accurately than for one in which the spin orientations are
random. Our knowledge of a source's sky position will thus be worst for the
gas-rich systems which are most likely to produce electromagnetic counterparts.
Fortunately, higher harmonics of the waveform can make up for this degradation.
By including harmonics beyond the quadrupole in our waveform model, we find
that the accuracy with which most of the binary's parameters are measured can
be substantially improved. In some cases, parameters can be measured as well in
partially aligned binaries as they can be when the binary spins are random.
| [
{
"created": "Wed, 19 Jan 2011 00:29:17 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Aug 2011 02:36:26 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Lang",
"Ryan N.",
""
],
[
"Hughes",
"Scott A.",
""
],
[
"Cornish",
"Neil J.",
""
]
] | The future space-based gravitational wave detector LISA will be able to measure parameters of coalescing massive black hole binaries, often to extremely high accuracy. Previous work has demonstrated that the black hole spins can have a strong impact on the accuracy of parameter measurement. Relativistic spin-induced precession modulates the waveform in a manner which can break degeneracies between parameters, in principle significantly improving how well they are measured. Recent studies have indicated, however, that spin precession may be weak for an important subset of astrophysical binary black holes: those in which the spins are aligned due to interactions with gas. In this paper, we examine how well a binary's parameters can be measured when its spins are partially aligned and compare results using waveforms that include higher post-Newtonian harmonics to those that are truncated at leading quadrupole order. We find that the weakened precession can substantially degrade parameter estimation. This degradation is particularly devastating for the extrinsic parameters sky position and distance. Absent higher harmonics, LISA typically localizes the sky position of a nearly aligned binary a factor of $\sim 6$ less accurately than for one in which the spin orientations are random. Our knowledge of a source's sky position will thus be worst for the gas-rich systems which are most likely to produce electromagnetic counterparts. Fortunately, higher harmonics of the waveform can make up for this degradation. By including harmonics beyond the quadrupole in our waveform model, we find that the accuracy with which most of the binary's parameters are measured can be substantially improved. In some cases, parameters can be measured as well in partially aligned binaries as they can be when the binary spins are random. |
gr-qc/0605084 | Young-Jai Park | Wontae Kim, Yong-Wan Kim, and Young-Jai Park | Entropy of the Randall-Sundrum brane world with the generalized
uncertainty principle | 12 pages. The improved version published in Phys. Rev. D | Phys.Rev. D74 (2006) 104001 | 10.1103/PhysRevD.74.104001 | SOGANG-HEP 317/06 | gr-qc | null | By introducing the generalized uncertainty principle, we calculate the
entropy of the bulk scalar field on the Randall-Sundrum brane background
without any cutoff. We obtain the entropy of the massive scalar field
proportional to the horizon area. Here, we observe that the mass contribution
to the entropy exists in contrast to all previous results, which is independent
of the mass of the scalar field, of the usual black hole cases with the
generalized uncertainty principle.
| [
{
"created": "Mon, 15 May 2006 06:24:54 GMT",
"version": "v1"
},
{
"created": "Sun, 21 May 2006 10:15:12 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Nov 2006 02:39:28 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Kim",
"Wontae",
""
],
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
]
] | By introducing the generalized uncertainty principle, we calculate the entropy of the bulk scalar field on the Randall-Sundrum brane background without any cutoff. We obtain the entropy of the massive scalar field proportional to the horizon area. Here, we observe that the mass contribution to the entropy exists in contrast to all previous results, which is independent of the mass of the scalar field, of the usual black hole cases with the generalized uncertainty principle. |
2101.04152 | Peter Hess O | Peter Otto Hess | Observable consequences of pseudo-complex General Relativity | 32 pages, 10 figures, spscial issue: Classical Extensions and
Alternative Theories of Gravity, HINDAWI | null | null | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | A review of the pseudo-complex General Relativity (pc-GR) is presented, with
the emphasis on observational consequences. First it is argued why to use an
algebraic extension and why the pseudo-complex is a viable one. Afterward, the
pc-GR is formulated. Posterior, several observational consequences are
discussed, as the perihelion shift of Mercury, Quasi Periodic Objects, the
emission profile of accretion discs, the pc-Robertson-Walker model of the
universe, neutron stars and gravitational ring-down modes of a black hole.
| [
{
"created": "Mon, 11 Jan 2021 19:28:18 GMT",
"version": "v1"
}
] | 2021-01-13 | [
[
"Hess",
"Peter Otto",
""
]
] | A review of the pseudo-complex General Relativity (pc-GR) is presented, with the emphasis on observational consequences. First it is argued why to use an algebraic extension and why the pseudo-complex is a viable one. Afterward, the pc-GR is formulated. Posterior, several observational consequences are discussed, as the perihelion shift of Mercury, Quasi Periodic Objects, the emission profile of accretion discs, the pc-Robertson-Walker model of the universe, neutron stars and gravitational ring-down modes of a black hole. |
1912.00591 | Rituparno Goswami | Rituparno Goswami, George F. R. Ellis | Tidal forces are gravitational waves | 16 pages, revtex4 | null | null | null | gr-qc astro-ph.EP astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we show in a covariant and gauge invariant way that in general
relativity, tidal forces are actually a hidden form of gravitational waves.
This must be so because gravitational effects cannot occur faster than the
speed of light. Any two body gravitating system, where the bodies are orbiting
around each other, may generate negligible gravitational waves, but it is via
these waves that non-negligible tidal forces (causing shape distortions) act on
these bodies. Although the tidal forces are caused by the electric part of the
Weyl tensor, we transparently show that some small time varying magnetic part
of the Weyl tensor with non zero curl must be present in the system that
mediates the tidal forces via gravitational wave type effects. The outcome is a
new test of whether gravitational effects propagate at the speed of light.
| [
{
"created": "Mon, 2 Dec 2019 06:34:14 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Sep 2020 08:56:01 GMT",
"version": "v2"
}
] | 2020-09-15 | [
[
"Goswami",
"Rituparno",
""
],
[
"Ellis",
"George F. R.",
""
]
] | In this paper we show in a covariant and gauge invariant way that in general relativity, tidal forces are actually a hidden form of gravitational waves. This must be so because gravitational effects cannot occur faster than the speed of light. Any two body gravitating system, where the bodies are orbiting around each other, may generate negligible gravitational waves, but it is via these waves that non-negligible tidal forces (causing shape distortions) act on these bodies. Although the tidal forces are caused by the electric part of the Weyl tensor, we transparently show that some small time varying magnetic part of the Weyl tensor with non zero curl must be present in the system that mediates the tidal forces via gravitational wave type effects. The outcome is a new test of whether gravitational effects propagate at the speed of light. |
1306.2055 | Behnam Pourhassan | J. Sadeghi, B. Pourhassan, and Z. Abbaspour Moghaddam | Interacting Entropy-Corrected Holographic Dark Energy and IR Cut-Off
Length | 13 pages, 2 figures added in revised version. References added | International Journal of Theoretical Physics 53 (2014) 125-135 | 10.1007/s10773-013-1790-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider holographic dark energy model with corrected
holographic energy density and show that this model may be equivalent to the
modified Chaplygin gas model. Then we obtain relation between entropy corrected
holographic dark energy model and scalar field models. We do these works by
using choices of IR cut-off length proportional to the Hubble radius, the event
horizon radius, the Ricci length, and the Granda-Oliveros length.
| [
{
"created": "Sun, 9 Jun 2013 19:26:42 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2013 09:36:03 GMT",
"version": "v2"
}
] | 2014-01-13 | [
[
"Sadeghi",
"J.",
""
],
[
"Pourhassan",
"B.",
""
],
[
"Moghaddam",
"Z. Abbaspour",
""
]
] | In this paper we consider holographic dark energy model with corrected holographic energy density and show that this model may be equivalent to the modified Chaplygin gas model. Then we obtain relation between entropy corrected holographic dark energy model and scalar field models. We do these works by using choices of IR cut-off length proportional to the Hubble radius, the event horizon radius, the Ricci length, and the Granda-Oliveros length. |
gr-qc/0209058 | Soon-Tae Hong | Soon-Tae Hong, Jaedong Choi and Young-Jai Park | (2+1) dimensional black holes in warped product scheme | 13 pages | null | null | SOGANG-HEP 300/02 | gr-qc | null | Exploiting a multiply warped product manifold scheme, we study the interior
solutions of the Banados-Teitelboim-Zanelli black holes and the exterior
solutions of the de Sitter black holes in the (2+1) dimensions.
| [
{
"created": "Wed, 18 Sep 2002 10:11:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hong",
"Soon-Tae",
""
],
[
"Choi",
"Jaedong",
""
],
[
"Park",
"Young-Jai",
""
]
] | Exploiting a multiply warped product manifold scheme, we study the interior solutions of the Banados-Teitelboim-Zanelli black holes and the exterior solutions of the de Sitter black holes in the (2+1) dimensions. |
1103.3201 | Frank Reifler | Mayeul Arminjon and Frank Reifler | Equivalent forms of Dirac equations in curved spacetimes and generalized
de Broglie relations | PDF, 32 pages in referee format. Added significant material on
canonical forms of Dirac equations. Simplified Theorem 1 for normal Dirac
equations. Added section on Gordon decomposition of the probability current.
Encapsulated main results in the statement of Theorem 2 | Brazilian Journal of Physics 43, No. 1-2, 64-77 (2013) | 10.1007/s13538-012-0111-0 | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One may ask whether the relations between energy and frequency and between
momentum and wave vector, introduced for matter waves by de Broglie, are
rigorously valid in the presence of gravity. In this paper, we show this to be
true for Dirac equations in a background of gravitational and electromagnetic
fields. We first transform any Dirac equation into an equivalent canonical
form, sometimes used in particular cases to solve Dirac equations in a curved
spacetime. This canonical form is needed to apply the Whitham Lagrangian
method. The latter method, unlike the WKB method, places no restriction on the
magnitude of Planck's constant to obtain wave packets, and furthermore
preserves the symmetries of the Dirac Lagrangian. We show using canonical Dirac
fields in a curved spacetime, that the probability current has a Gordon
decomposition into a convection current and a spin current, and that the spin
current vanishes in the Whitham approximation, which explains the negligible
effect of spin on wave packet solutions, independent of the size of Planck's
constant. We further discuss the classical-quantum correspondence in a curved
spacetime based on both Lagrangian and Hamiltonian formulations of the Whitham
equations. We show that the generalized de Broglie relations in a curved
spacetime are a direct consequence of Whitham's Lagrangian method, and not just
a physical hypothesis as introduced by Einstein and de Broglie, and by many
quantum mechanics textbooks.
| [
{
"created": "Wed, 16 Mar 2011 15:33:48 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Nov 2011 19:18:42 GMT",
"version": "v2"
},
{
"created": "Fri, 20 Jan 2012 17:37:12 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Jan 2013 18:57:29 GMT",
"version": "v4"
}
] | 2013-11-22 | [
[
"Arminjon",
"Mayeul",
""
],
[
"Reifler",
"Frank",
""
]
] | One may ask whether the relations between energy and frequency and between momentum and wave vector, introduced for matter waves by de Broglie, are rigorously valid in the presence of gravity. In this paper, we show this to be true for Dirac equations in a background of gravitational and electromagnetic fields. We first transform any Dirac equation into an equivalent canonical form, sometimes used in particular cases to solve Dirac equations in a curved spacetime. This canonical form is needed to apply the Whitham Lagrangian method. The latter method, unlike the WKB method, places no restriction on the magnitude of Planck's constant to obtain wave packets, and furthermore preserves the symmetries of the Dirac Lagrangian. We show using canonical Dirac fields in a curved spacetime, that the probability current has a Gordon decomposition into a convection current and a spin current, and that the spin current vanishes in the Whitham approximation, which explains the negligible effect of spin on wave packet solutions, independent of the size of Planck's constant. We further discuss the classical-quantum correspondence in a curved spacetime based on both Lagrangian and Hamiltonian formulations of the Whitham equations. We show that the generalized de Broglie relations in a curved spacetime are a direct consequence of Whitham's Lagrangian method, and not just a physical hypothesis as introduced by Einstein and de Broglie, and by many quantum mechanics textbooks. |
gr-qc/0407025 | Sergey G. Klimenko | S Klimenko, I Yakushin, M Rakhmanov and G Mitselmakher | Performance of the WaveBurst algorithm on LIGO data | proceedings of GWDAW, 2003 conference, 13 pages, 6 figures | Class.Quant.Grav.21:S1685-S1694,2004 | 10.1088/0264-9381/21/20/011 | LIGO-P040012-00-Z | gr-qc | null | In this paper we describe the performance of the WaveBurst algorithm which
was designed for detection of gravitational wave bursts in interferometric
data. The performance of the algorithm was evaluated on the test data set
collected during the second LIGO Scientific run. We have measured the false
alarm rate of the algorithm as a function of the threshold and estimated its
detection efficiency for simulated burst waveforms.
| [
{
"created": "Tue, 6 Jul 2004 21:57:32 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Klimenko",
"S",
""
],
[
"Yakushin",
"I",
""
],
[
"Rakhmanov",
"M",
""
],
[
"Mitselmakher",
"G",
""
]
] | In this paper we describe the performance of the WaveBurst algorithm which was designed for detection of gravitational wave bursts in interferometric data. The performance of the algorithm was evaluated on the test data set collected during the second LIGO Scientific run. We have measured the false alarm rate of the algorithm as a function of the threshold and estimated its detection efficiency for simulated burst waveforms. |
0901.2861 | Emilio Elizalde | Jaume Haro, Emilio Elizalde | Effective gravity formulation that avoids singularities in quantum FRW
cosmologies | 11 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Assuming that time exists, a new, effective formulation of gravity is
introduced, which lies in between the Wheeler-DeWitt approach and ordinary QFT.
Remarkably, the Penrose-Hawking singularity of usual Friedman-Robertson-Walker
cosmologies is naturally avoided there. The theory is made explicit via
specific examples, and compared with loop quantum cosmology. It is argued that
it is the regularization of the classical Hamiltonian performed in this last
theory what avoid the singularity, rather than quantum effects as in our case.
| [
{
"created": "Mon, 19 Jan 2009 14:23:09 GMT",
"version": "v1"
}
] | 2009-01-20 | [
[
"Haro",
"Jaume",
""
],
[
"Elizalde",
"Emilio",
""
]
] | Assuming that time exists, a new, effective formulation of gravity is introduced, which lies in between the Wheeler-DeWitt approach and ordinary QFT. Remarkably, the Penrose-Hawking singularity of usual Friedman-Robertson-Walker cosmologies is naturally avoided there. The theory is made explicit via specific examples, and compared with loop quantum cosmology. It is argued that it is the regularization of the classical Hamiltonian performed in this last theory what avoid the singularity, rather than quantum effects as in our case. |
1302.0375 | Silke Weinfurtner | Silke Weinfurtner, Edmund W. Tedford, Matthew C.J. Penrice, William G.
Unruh, and Gregory A. Lawrence | Classical aspects of Hawking radiation verified in analogue gravity
experiment | 17 pages, 10 figures; draft of a chapter submitted to the proceedings
of the IX'th SIGRAV graduate school: Analogue Gravity, Lake Como, Italy, May
2011 | null | 10.1007/978-3-319-00266-8_8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is an analogy between the propagation of fields on a curved spacetime
and shallow water waves in an open channel flow. By placing a streamlined
obstacle into an open channel flow we create a region of high velocity over the
obstacle that can include wave horizons. Long (shallow water) waves propagating
upstream towards this region are blocked and converted into short (deep water)
waves. This is the analogue of the stimulated Hawking emission by a white hole
(the time inverse of a black hole). The measurements of amplitudes of the
converted waves demonstrate that they appear in pairs and are classically
correlated; the spectra of the conversion process is described by a
Boltzmann-distribution; and the Boltzmann-distribution is determined by the
determined by the change in flow across the white hole horizon.
| [
{
"created": "Sat, 2 Feb 2013 13:24:09 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Weinfurtner",
"Silke",
""
],
[
"Tedford",
"Edmund W.",
""
],
[
"Penrice",
"Matthew C. J.",
""
],
[
"Unruh",
"William G.",
""
],
[
"Lawrence",
"Gregory A.",
""
]
] | There is an analogy between the propagation of fields on a curved spacetime and shallow water waves in an open channel flow. By placing a streamlined obstacle into an open channel flow we create a region of high velocity over the obstacle that can include wave horizons. Long (shallow water) waves propagating upstream towards this region are blocked and converted into short (deep water) waves. This is the analogue of the stimulated Hawking emission by a white hole (the time inverse of a black hole). The measurements of amplitudes of the converted waves demonstrate that they appear in pairs and are classically correlated; the spectra of the conversion process is described by a Boltzmann-distribution; and the Boltzmann-distribution is determined by the determined by the change in flow across the white hole horizon. |
1912.06494 | Saibal Ray | Rikpratik Sengupta, Prasenjit Paul, Bikash Chandra Paul and Saibal Ray | Inflation in anisotropic brane universe using tachyon field | 15 pages, 5 figures, Accepted in IJMPD | International Journal of Modern Physics D Vol. 28, No. 13, 1941010
(2019) | 10.1142/S0218271819410104 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological solution to the gravitational field equations in the generalized
Randall-Sundrum model for an anisotropic brane with Bianchi I geometry and
perfect fluid as matter sources has been considered. The matter on the brane is
described by a tachyonic field. The solution admits inflationary era and at a
later epoch the anisotropy of the universe washes out. We obtain two classes of
cosmological scenario, in the first case universe evolves from singularity and
in the second case universe expands without singularity.
| [
{
"created": "Thu, 12 Dec 2019 07:22:11 GMT",
"version": "v1"
}
] | 2019-12-16 | [
[
"Sengupta",
"Rikpratik",
""
],
[
"Paul",
"Prasenjit",
""
],
[
"Paul",
"Bikash Chandra",
""
],
[
"Ray",
"Saibal",
""
]
] | Cosmological solution to the gravitational field equations in the generalized Randall-Sundrum model for an anisotropic brane with Bianchi I geometry and perfect fluid as matter sources has been considered. The matter on the brane is described by a tachyonic field. The solution admits inflationary era and at a later epoch the anisotropy of the universe washes out. We obtain two classes of cosmological scenario, in the first case universe evolves from singularity and in the second case universe expands without singularity. |
2209.11374 | Hyeong-Chan Kim | Hyeong-Chan Kim | Particle creations in a variational formulation of relativistic
thermodynamics with dissipation | 6 pages, No figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In modeling relativistic thermodynamics, we frequently regard the particle
number as a conserved quantity. The number conservation law, which comes from
the requirement that the pull-back construction from fluid-matter 3-space has
the same degrees of freedom as the number of independent components of the
four-dimensional Lagrangian variations, supports the assumption. On the other
hand, Andersson and Comer[1] argue that their variational model is compatible
with non-vanishing particle creation rates. We support the result and prove
that a proper variational formula considering the effect of the creation rate
enables us to treat the non-vanishing creation rate without any additional
requirement.
| [
{
"created": "Fri, 23 Sep 2022 02:27:01 GMT",
"version": "v1"
}
] | 2022-09-26 | [
[
"Kim",
"Hyeong-Chan",
""
]
] | In modeling relativistic thermodynamics, we frequently regard the particle number as a conserved quantity. The number conservation law, which comes from the requirement that the pull-back construction from fluid-matter 3-space has the same degrees of freedom as the number of independent components of the four-dimensional Lagrangian variations, supports the assumption. On the other hand, Andersson and Comer[1] argue that their variational model is compatible with non-vanishing particle creation rates. We support the result and prove that a proper variational formula considering the effect of the creation rate enables us to treat the non-vanishing creation rate without any additional requirement. |
2303.07349 | Gamal G.L. Nashed | G. G. L. Nashed and Shin'ichi Nojiri | Slow-rotating charged black hole solution in dynamical Chern-Simons
modified gravity | 20 pages 3 figures, will appear in Phys. Rev. D | null | 10.1103/PhysRevD.107.064069 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The Chern-Simons (CS) gravity is a modified theory of Einstein's general
relativity (GR). The CS theory arises from the low energy limit of string
theory which involves anomaly correction to the Einstein-Hilbert action. The CS
term is given by the product of the Pontryagin density with a scalar field. In
this study, we derive a charged slowly rotating black hole (BH) solution. The
main incentives of this BH solution are axisymmetric and stationary and form
distortion of the Kerr-Newman BH solution with a dipole scalar field.
Additionally, we investigate the asymptotic correction of the metric with the
inverse seventh power of the radial distance to the BH solution, This indicates
that it will escape any meaningful constraints from weak-field experiments. To
find this kind of BHs by observations, we investigate the propagation of the
photon near the BH and we show that the difference between the left-rotated
polarization and the right-handed one could be observed as stronger than the
case of the Kerr-Newman BH. Finally, we derived the stability condition using
the geodesic deviations.
| [
{
"created": "Sat, 11 Mar 2023 06:55:27 GMT",
"version": "v1"
}
] | 2023-04-12 | [
[
"Nashed",
"G. G. L.",
""
],
[
"Nojiri",
"Shin'ichi",
""
]
] | The Chern-Simons (CS) gravity is a modified theory of Einstein's general relativity (GR). The CS theory arises from the low energy limit of string theory which involves anomaly correction to the Einstein-Hilbert action. The CS term is given by the product of the Pontryagin density with a scalar field. In this study, we derive a charged slowly rotating black hole (BH) solution. The main incentives of this BH solution are axisymmetric and stationary and form distortion of the Kerr-Newman BH solution with a dipole scalar field. Additionally, we investigate the asymptotic correction of the metric with the inverse seventh power of the radial distance to the BH solution, This indicates that it will escape any meaningful constraints from weak-field experiments. To find this kind of BHs by observations, we investigate the propagation of the photon near the BH and we show that the difference between the left-rotated polarization and the right-handed one could be observed as stronger than the case of the Kerr-Newman BH. Finally, we derived the stability condition using the geodesic deviations. |
0906.3278 | Miguel Angel Garcia Aspeitia | Miguel Angel Garcia Aspeitia and Tonatiuh Matos | The Universe Dynamics from Topological Considerations | 8 pages, 1 figure, Third report new version | Gen.Rel.Grav.43:315-329,2011 | 10.1007/s10714-010-1093-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the possibility that the dynamics of the universe can be
reproduced choosing appropriately the initial global topology of the Universe.
In this work we start with two concentric spherical three-dimensional branes
S^3, with radius a_1<a_2 immersed in a five-dimensional space-time. The novel
feature of this model is that in the interior brane there exist only spin-zero
fundamental fields (scalar fields), while in the exterior one there exist only
spin-one fundamental interactions. As usual, the bulk of the universe is
dominated by gravitational interactions. In this model, like in the Ekpyrotic
one, the Big Bang is consequence of the collision of the branes and causes the
existence of the particles predicted by the standard model in the exterior
brane (our universe). The scalar fields on the interior brane interact with the
spin-one fields on the exterior one only through gravitation, they induce the
effect of Scalar Field Dark Matter with an ultra-light mass on the exterior
one. We discuss two different regimes where the energy density and the brane
tension are compared, with the aim to obtain the observed dynamics of the
universe after the collision of the branes.
| [
{
"created": "Wed, 17 Jun 2009 19:03:22 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2009 16:59:19 GMT",
"version": "v2"
},
{
"created": "Sun, 30 May 2010 13:26:40 GMT",
"version": "v3"
}
] | 2011-02-07 | [
[
"Aspeitia",
"Miguel Angel Garcia",
""
],
[
"Matos",
"Tonatiuh",
""
]
] | We explore the possibility that the dynamics of the universe can be reproduced choosing appropriately the initial global topology of the Universe. In this work we start with two concentric spherical three-dimensional branes S^3, with radius a_1<a_2 immersed in a five-dimensional space-time. The novel feature of this model is that in the interior brane there exist only spin-zero fundamental fields (scalar fields), while in the exterior one there exist only spin-one fundamental interactions. As usual, the bulk of the universe is dominated by gravitational interactions. In this model, like in the Ekpyrotic one, the Big Bang is consequence of the collision of the branes and causes the existence of the particles predicted by the standard model in the exterior brane (our universe). The scalar fields on the interior brane interact with the spin-one fields on the exterior one only through gravitation, they induce the effect of Scalar Field Dark Matter with an ultra-light mass on the exterior one. We discuss two different regimes where the energy density and the brane tension are compared, with the aim to obtain the observed dynamics of the universe after the collision of the branes. |
gr-qc/0505068 | Daniel R. Terno | Daniel R. Terno | From qubits to black holes: entropy, entanglement and all that | Honorable Mention in the 2005 Gravity Research Foundation Essay
Competition | Int.J.Mod.Phys. D14 (2005) 2307-2314 | 10.1142/S0218271805007802 | null | gr-qc hep-th quant-ph | null | Entropy plays a crucial role in characterization of information and
entanglement, but it is not a scalar quantity and for many systems it is
different for different relativistic observers. Loop quantum gravity predicts
the Bekenstein-Hawking term for black hole entropy and logarithmic correction
to it. The latter originates in the entanglement between the pieces of spin
networks that describe black hole horizon. Entanglement between gravity and
matter may restore the unitarity in the black hole evaporation process. If the
collapsing matter is assumed to be initially in a pure state, then entropy of
the Hawking radiation is exactly the created entanglement between matter and
gravity.
| [
{
"created": "Fri, 13 May 2005 14:19:20 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Terno",
"Daniel R.",
""
]
] | Entropy plays a crucial role in characterization of information and entanglement, but it is not a scalar quantity and for many systems it is different for different relativistic observers. Loop quantum gravity predicts the Bekenstein-Hawking term for black hole entropy and logarithmic correction to it. The latter originates in the entanglement between the pieces of spin networks that describe black hole horizon. Entanglement between gravity and matter may restore the unitarity in the black hole evaporation process. If the collapsing matter is assumed to be initially in a pure state, then entropy of the Hawking radiation is exactly the created entanglement between matter and gravity. |
1906.02231 | Martin Bojowald | Martin Bojowald | Non-bouncing solutions in loop quantum cosmology | 24 pages | JCAP 07 (2020) 029 | 10.1088/1475-7516/2020/07/029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to the Belinskii-Khalatnikov-Lifshitz scenario, a collapsing
universe approaching a spacelike singularity can be approximated by homogeneous
cosmological dynamics, but only if asymptotically small spatial regions are
considered. It is shown here that the relevant small-volume behavior in
solvable models of loop quantum cosmology is crucially different from the
large-volume behavior exclusively studied so far. While bouncing solutions
exist and may even be generic within a given quantum representation, they are
not generic if quantization ambiguities such as choices of representations are
taken into account. The analysis reveals an interesting interplay between
sl(2,R)-representation theory and canonical effective theory.
| [
{
"created": "Wed, 5 Jun 2019 18:15:18 GMT",
"version": "v1"
}
] | 2020-07-16 | [
[
"Bojowald",
"Martin",
""
]
] | According to the Belinskii-Khalatnikov-Lifshitz scenario, a collapsing universe approaching a spacelike singularity can be approximated by homogeneous cosmological dynamics, but only if asymptotically small spatial regions are considered. It is shown here that the relevant small-volume behavior in solvable models of loop quantum cosmology is crucially different from the large-volume behavior exclusively studied so far. While bouncing solutions exist and may even be generic within a given quantum representation, they are not generic if quantization ambiguities such as choices of representations are taken into account. The analysis reveals an interesting interplay between sl(2,R)-representation theory and canonical effective theory. |
1907.13604 | Eleni-Alexandra Kontou | Christopher J. Fewster and Eleni-Alexandra Kontou | A new derivation of singularity theorems with weakened energy hypotheses | 27 pages | null | 10.1088/1361-6382/ab685b | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The original singularity theorems of Penrose and Hawking were proved for
matter obeying the Null Energy Condition or Strong Energy Condition
respectively. Various authors have proved versions of these results under
weakened hypotheses, by considering the Riccati inequality obtained from
Raychaudhuri's equation. Here, we give a different derivation that avoids the
Raychaudhuri equation but instead makes use of index form methods. We show how
our results improve over existing methods and how they can be applied to
hypotheses inspired by Quantum Energy Inequalities. In this last case, we make
quantitative estimates of the initial conditions required for our singularity
theorems to apply.
| [
{
"created": "Wed, 31 Jul 2019 17:07:32 GMT",
"version": "v1"
}
] | 2020-04-08 | [
[
"Fewster",
"Christopher J.",
""
],
[
"Kontou",
"Eleni-Alexandra",
""
]
] | The original singularity theorems of Penrose and Hawking were proved for matter obeying the Null Energy Condition or Strong Energy Condition respectively. Various authors have proved versions of these results under weakened hypotheses, by considering the Riccati inequality obtained from Raychaudhuri's equation. Here, we give a different derivation that avoids the Raychaudhuri equation but instead makes use of index form methods. We show how our results improve over existing methods and how they can be applied to hypotheses inspired by Quantum Energy Inequalities. In this last case, we make quantitative estimates of the initial conditions required for our singularity theorems to apply. |
2105.05653 | Iver Brevik | I. Brevik and A. V. Timoshkin | Holographic cosmology with two coupled fluids in the presence of
viscosity | 10 pages, no figures. To appear in Int. J. Geom. Meth. Mod. Phys | Int. J. Geom. Meth. Mod. Phys. 18, 2150149 (2021) | 10.1142/S0219887821501498 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We explore the cosmological models of the late-time universe based on the
holographic principle, taking into account the properties of the viscosity of
the dark fluid. We use the mathematical formalism of generalized infrared
cutoff holographic dark energy, as presented by Nojiri and Odintsov (2017). We
consider the Little Rip, the Pseudo Rip, and a bounce exponential model, with
two interacting fluids, namely dark energy and dark matter in a spatially-flat
Friedmann-Robertson-Walker universe. Within these models, analytical
expressions are obtained for infrared cutoffs in terms of the particle
horizons. The law of conservation of energy is presented, from a holographic
point of view.
| [
{
"created": "Wed, 12 May 2021 13:41:38 GMT",
"version": "v1"
}
] | 2021-08-11 | [
[
"Brevik",
"I.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] | We explore the cosmological models of the late-time universe based on the holographic principle, taking into account the properties of the viscosity of the dark fluid. We use the mathematical formalism of generalized infrared cutoff holographic dark energy, as presented by Nojiri and Odintsov (2017). We consider the Little Rip, the Pseudo Rip, and a bounce exponential model, with two interacting fluids, namely dark energy and dark matter in a spatially-flat Friedmann-Robertson-Walker universe. Within these models, analytical expressions are obtained for infrared cutoffs in terms of the particle horizons. The law of conservation of energy is presented, from a holographic point of view. |
2202.04360 | Pietro Dona | Pietro Dona and Pietropaolo Frisoni | How-To compute EPRL spin foam amplitudes | 28 pages with many colored figures. Paper published in the special
issue "Probing the Quantum Space-Time" of Universe. v-2 Added introductory
section. Matching published version. [QISS] | Universe 2022, 8(4), 208 | 10.3390/universe8040208 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin foam theory is a concrete framework for quantum gravity where numerical
calculations of transition amplitudes are possible. Recently, the field became
very active, but the entry barrier is steep, mainly because of its unusual
language and notions scattered around the literature. This paper is a
pedagogical guide to spin foam transition amplitude calculations. We show how
to write an EPRL-FK transition amplitude, from the definition of the 2-complex
to its numerical implementation using \texttt{sl2cfoam-next}. We guide the
reader using an explicit example balancing mathematical rigor with a practical
approach. We discuss the advantages and disadvantages of this approach and
provide a novel look at a recently proposed approximation scheme.
| [
{
"created": "Wed, 9 Feb 2022 09:45:08 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2022 11:34:51 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Sep 2022 13:19:22 GMT",
"version": "v3"
}
] | 2022-09-19 | [
[
"Dona",
"Pietro",
""
],
[
"Frisoni",
"Pietropaolo",
""
]
] | Spin foam theory is a concrete framework for quantum gravity where numerical calculations of transition amplitudes are possible. Recently, the field became very active, but the entry barrier is steep, mainly because of its unusual language and notions scattered around the literature. This paper is a pedagogical guide to spin foam transition amplitude calculations. We show how to write an EPRL-FK transition amplitude, from the definition of the 2-complex to its numerical implementation using \texttt{sl2cfoam-next}. We guide the reader using an explicit example balancing mathematical rigor with a practical approach. We discuss the advantages and disadvantages of this approach and provide a novel look at a recently proposed approximation scheme. |
1011.0623 | Hyeyoun Chung | Hyeyoun Chung | Dynamics of Diffeomorphism Degrees of Freedom at a Horizon | 12 pages. Final version accepted for publication in Physical Review D | Phys.Rev.D83:084017,2011 | 10.1103/PhysRevD.83.084017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We define a set of boundary conditions that ensure the presence of a null
hypersurface with the essential characteristics of a horizon, using the
formalism of weakly isolated horizons as a guide. We then determine the
diffeomorphisms that preserve these boundary conditions, and derive a dynamical
action for these diffeomorphisms in a neighbourhood of the horizon. The action
is similar to that of Liouville theory, and the equation of motion of the
gravitational degrees of freedom approaches that of a free two-dimensional
conformal field theory in the near-horizon region.
| [
{
"created": "Tue, 2 Nov 2010 14:14:28 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Nov 2010 19:14:56 GMT",
"version": "v2"
},
{
"created": "Sat, 19 Mar 2011 12:42:15 GMT",
"version": "v3"
}
] | 2011-04-22 | [
[
"Chung",
"Hyeyoun",
""
]
] | We define a set of boundary conditions that ensure the presence of a null hypersurface with the essential characteristics of a horizon, using the formalism of weakly isolated horizons as a guide. We then determine the diffeomorphisms that preserve these boundary conditions, and derive a dynamical action for these diffeomorphisms in a neighbourhood of the horizon. The action is similar to that of Liouville theory, and the equation of motion of the gravitational degrees of freedom approaches that of a free two-dimensional conformal field theory in the near-horizon region. |
1908.10022 | Rafael Sorkin | Rafael D. Sorkin | Lorentzian angles and trigonometry including lightlike vectors | Version 2 has figures in final form. 39 pages, 12 figures. Most
current version will be available at
http://www.perimeterinstitute.ca/personal/rsorkin/some.papers/ (or wherever
my home-page may be) | null | null | null | gr-qc hep-lat hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We define a concept of Lorentzian angle that works even when one or both of
the directions involved is null (lightlike). Such angles play a role in
Regge-Calculus, in the boundary- and corner- terms for the gravitational
action, and in the Lorentzian Gauss-Bonnet theorem (for which we provide a
proof).
| [
{
"created": "Tue, 27 Aug 2019 04:36:26 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Feb 2020 04:58:42 GMT",
"version": "v2"
}
] | 2020-02-07 | [
[
"Sorkin",
"Rafael D.",
""
]
] | We define a concept of Lorentzian angle that works even when one or both of the directions involved is null (lightlike). Such angles play a role in Regge-Calculus, in the boundary- and corner- terms for the gravitational action, and in the Lorentzian Gauss-Bonnet theorem (for which we provide a proof). |
1904.13252 | Christian Corda Prof. | Christian Corda | Mossbauer rotor experiment as new proof of general relativity: Rigorous
computation of the additional effect of clock synchronization | 17 pages, 1 figure.This final version matches the one published in
Int. Jour. Mod. Phys D. This paper is a rebuttal to the various versions of
arXiv:1610.04219. Some issues in arXiv:1602.04212 and arXiv:1502.04911 have
been partially reviewed | Int. Jour. Mod. Phys. D 28 (10), 1950131 (2019) | 10.1142/S0218271819501311 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We received an Honorable Mention at the Gravity Research Foundation 2018
Awards for Essays on Gravitation by showing that a correct general relativistic
interpretation of the Mossbauer rotor experiment represents a new, strong and
independent, proof of Einstein's general theory relativity (GTR). Here we
correct a mistake which was present in our previous computations on this
important issue by deriving a rigorous computation of the additional effect of
clock synchronization. Finally, we show that some recent criticisms on our
general relativistic approach to the Mossbauer rotor experiment are incorrect,
by ultimately confirming our important result.
| [
{
"created": "Mon, 29 Apr 2019 15:33:07 GMT",
"version": "v1"
},
{
"created": "Mon, 20 May 2019 08:04:34 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Jun 2019 08:25:38 GMT",
"version": "v3"
},
{
"created": "Wed, 19 Jun 2019 09:47:39 GMT",
"version": "v4"
}
] | 2019-07-29 | [
[
"Corda",
"Christian",
""
]
] | We received an Honorable Mention at the Gravity Research Foundation 2018 Awards for Essays on Gravitation by showing that a correct general relativistic interpretation of the Mossbauer rotor experiment represents a new, strong and independent, proof of Einstein's general theory relativity (GTR). Here we correct a mistake which was present in our previous computations on this important issue by deriving a rigorous computation of the additional effect of clock synchronization. Finally, we show that some recent criticisms on our general relativistic approach to the Mossbauer rotor experiment are incorrect, by ultimately confirming our important result. |
2304.10318 | Leonardo Modesto | Zhe Zhao and Leonardo Modesto | Quantum avoidance of G\"{o}del's closed timelike curves | 13 pages | null | 10.1140/epjc/s10052-023-11694-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a large class of nonlocal as well as local higher derivative theories
minimally coupled to the matter sector, we investigate the exactness of two
different classes of homogeneous G\"{o}del-type solutions, which may or may not
allow closed time-like curves (CTC). Our analysis is limited to spacetimes
solving the Einstein's EoM, thus we can not exclude the presence of other
G\"{o}del-type solutions solving the EoM of local and nonlocal higher
derivative theories but not the Einstein's EoM.It turns out that the
homogeneous G\"{o}del spacetimes without CTC are basically exact solutions for
all theories, while the metrics with CTC are not exact solutions of
(super-)renormalizable local or nonlocal gravitational theories. Hence, the
quantum renormalizability property excludes theories suffering of the
G\"{o}del's causality violation. We also comment about nonlocal gravity
non-minimally coupled to matter. In this class of theories, all the G\"{o}del's
spacetimes, with or without CTC, are exact solutions at classical level.
However, the quantum corrections, although perturbative, very likely spoil the
exactness of such solutions. Therefore, we can state that the G\"{o}del's
Universes with CTC and the super-renormalizability are mutually exclusive.
| [
{
"created": "Thu, 20 Apr 2023 13:51:08 GMT",
"version": "v1"
}
] | 2023-07-05 | [
[
"Zhao",
"Zhe",
""
],
[
"Modesto",
"Leonardo",
""
]
] | In a large class of nonlocal as well as local higher derivative theories minimally coupled to the matter sector, we investigate the exactness of two different classes of homogeneous G\"{o}del-type solutions, which may or may not allow closed time-like curves (CTC). Our analysis is limited to spacetimes solving the Einstein's EoM, thus we can not exclude the presence of other G\"{o}del-type solutions solving the EoM of local and nonlocal higher derivative theories but not the Einstein's EoM.It turns out that the homogeneous G\"{o}del spacetimes without CTC are basically exact solutions for all theories, while the metrics with CTC are not exact solutions of (super-)renormalizable local or nonlocal gravitational theories. Hence, the quantum renormalizability property excludes theories suffering of the G\"{o}del's causality violation. We also comment about nonlocal gravity non-minimally coupled to matter. In this class of theories, all the G\"{o}del's spacetimes, with or without CTC, are exact solutions at classical level. However, the quantum corrections, although perturbative, very likely spoil the exactness of such solutions. Therefore, we can state that the G\"{o}del's Universes with CTC and the super-renormalizability are mutually exclusive. |
0705.0881 | Vladimir Ivashchuk | V. D. Ivashchuk | S-brane solutions with orthogonal intersection rules | 10 pages, Latex, invited paper to a fest of A. Garsia; typo in eq.
(3.4) is eliminated | Gen.Rel.Grav.37:751-758,2005 | 10.1007/s10714-005-0070-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A family of generalized composite intersecting S-brane solutions with
orthogonal intersection rules is described.
| [
{
"created": "Mon, 7 May 2007 11:00:36 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Oct 2011 16:29:45 GMT",
"version": "v2"
}
] | 2011-11-01 | [
[
"Ivashchuk",
"V. D.",
""
]
] | A family of generalized composite intersecting S-brane solutions with orthogonal intersection rules is described. |
2404.05597 | Iver Brevik | I. Brevik and A. V. Timoshkin | Little Rip and Pseudo Rip cosmological models with coupled dark energy
based on a new generalized entropy | 8 pages latex, no figures, to appear in Int. J. Geom. Meth. Mod. Phys | Int. J. Geom. Meth. Mod. Phys. (2024) 2450181 (12 pages) | 10.1142/S0219887824501810 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study Little Rip (LR) and Pseudo Rip (PR) cosmological models containing
two coupled fluids: dark energy and dark matter. We assume a spatially flat
Friedmann-Robertson-Walker (FRW) universe. The interaction between the dark
energy and the dark matter fluid components is described in terms of the
parameters in the generalized equation of state (EoS) in presence of the bulk
viscosity. We consider entropic cosmology and use a description based on a new
generalized entropy function, which was proposed by Nojiri-Odintsov-Faraoni
[1]. Conditions for the appearance of the (LR) and the (PR) in terms of the
parameters of the (EoS) are obtained. Introducing an energy density $\rho_g$
corresponding to a specified entropy function $S_g$, together with an
interaction term $Q$ in the gravitational equations of motion, we derive
modified forms of the EoS parameters. We discuss the corrections of the
thermodynamic parameters associated with the generalized entropy function.
Properties of the late universe as well as in the early universe in this
formalism are pointed out.
| [
{
"created": "Mon, 8 Apr 2024 15:17:37 GMT",
"version": "v1"
}
] | 2024-05-07 | [
[
"Brevik",
"I.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] | We study Little Rip (LR) and Pseudo Rip (PR) cosmological models containing two coupled fluids: dark energy and dark matter. We assume a spatially flat Friedmann-Robertson-Walker (FRW) universe. The interaction between the dark energy and the dark matter fluid components is described in terms of the parameters in the generalized equation of state (EoS) in presence of the bulk viscosity. We consider entropic cosmology and use a description based on a new generalized entropy function, which was proposed by Nojiri-Odintsov-Faraoni [1]. Conditions for the appearance of the (LR) and the (PR) in terms of the parameters of the (EoS) are obtained. Introducing an energy density $\rho_g$ corresponding to a specified entropy function $S_g$, together with an interaction term $Q$ in the gravitational equations of motion, we derive modified forms of the EoS parameters. We discuss the corrections of the thermodynamic parameters associated with the generalized entropy function. Properties of the late universe as well as in the early universe in this formalism are pointed out. |
1901.09599 | Michele Arzano | Michele Arzano, Lennart Brocki, Jerzy Kowalski-Glikman, Marco Letizia,
Josua Unger | Quantum ergosphere and brick wall entropy | 10 pages, no figures | null | 10.1016/j.physletb.2019.134887 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the "brick wall" model for black hole entropy taking into account
back-reaction effects on the horizon structure. We do so by adopting an
evaporating metric in the quasi-static approximation in which departures from
the standard Schwarzschild metric are governed by a small luminosity factor.
One of the effects of the back-reaction is to create an ergosphere-like region
which naturally tames the usual divergence in the calculation of the partition
function of the field. The black hole luminosity sets the width of such
"quantum ergosphere". We find a finite horizon contribution to the entropy
which, for the luminosity associated to the Hawking flux, agrees remarkably
well with the Bekenstein-Hawking relation.
| [
{
"created": "Mon, 28 Jan 2019 11:06:52 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Arzano",
"Michele",
""
],
[
"Brocki",
"Lennart",
""
],
[
"Kowalski-Glikman",
"Jerzy",
""
],
[
"Letizia",
"Marco",
""
],
[
"Unger",
"Josua",
""
]
] | We revisit the "brick wall" model for black hole entropy taking into account back-reaction effects on the horizon structure. We do so by adopting an evaporating metric in the quasi-static approximation in which departures from the standard Schwarzschild metric are governed by a small luminosity factor. One of the effects of the back-reaction is to create an ergosphere-like region which naturally tames the usual divergence in the calculation of the partition function of the field. The black hole luminosity sets the width of such "quantum ergosphere". We find a finite horizon contribution to the entropy which, for the luminosity associated to the Hawking flux, agrees remarkably well with the Bekenstein-Hawking relation. |
2407.20779 | Saeed Noori Gashti | Jafar Sadeghi, Mohammad Ali S. Afshar, Mohammad Reza Alipour, Saeed
Noori Gashti | Phase Transition Dynamics of Black Holes Influenced by Kaniadakis and
Barrow Statistics | 20 pages, 9 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this study, we investigate the dynamics and frame-by-frame phase
transition of the first order in black hole thermodynamics. For our analysis,
we will utilize the Kramers escape rate. Our focus is on charged anti-de Sitter
(AdS) black holes influenced by Kaniadakis and Barrow statistics. The selection
of these black holes aims to examine the effects of entropy variation on the
dynamics of phase transition and to demonstrate that the Kramers escape rate,
as an efficient tool, can effectively represent the dynamic transition from a
small to a large black hole within the domain of first-order phase transitions.
It is noteworthy that while the transition from small to large black holes
should ostensibly dominate the entire process, our results indicate that the
escape rate undergoes changes as it passes through the midpoint of the phase
transition, leading to a reverse escape phenomenon. The findings suggest that
the dynamic phase transition in charged AdS black holes affected by entropy
change bears a significant resemblance to the outcomes of models influenced by
Bekenstein-Hawking entropy\cite{23}. This similarity in results could serve as
an additional motivation to further explore the potential capabilities of
Kaniadakis and Barrow statistics in related cosmological fields. These
capabilities could enhance our understanding of other cosmological properties
| [
{
"created": "Tue, 30 Jul 2024 12:33:04 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Sadeghi",
"Jafar",
""
],
[
"Afshar",
"Mohammad Ali S.",
""
],
[
"Alipour",
"Mohammad Reza",
""
],
[
"Gashti",
"Saeed Noori",
""
]
] | In this study, we investigate the dynamics and frame-by-frame phase transition of the first order in black hole thermodynamics. For our analysis, we will utilize the Kramers escape rate. Our focus is on charged anti-de Sitter (AdS) black holes influenced by Kaniadakis and Barrow statistics. The selection of these black holes aims to examine the effects of entropy variation on the dynamics of phase transition and to demonstrate that the Kramers escape rate, as an efficient tool, can effectively represent the dynamic transition from a small to a large black hole within the domain of first-order phase transitions. It is noteworthy that while the transition from small to large black holes should ostensibly dominate the entire process, our results indicate that the escape rate undergoes changes as it passes through the midpoint of the phase transition, leading to a reverse escape phenomenon. The findings suggest that the dynamic phase transition in charged AdS black holes affected by entropy change bears a significant resemblance to the outcomes of models influenced by Bekenstein-Hawking entropy\cite{23}. This similarity in results could serve as an additional motivation to further explore the potential capabilities of Kaniadakis and Barrow statistics in related cosmological fields. These capabilities could enhance our understanding of other cosmological properties |
2309.05439 | Alesandro Santos | J. C. R. de Souza and A. F. Santos | An axially symmetric spacetime with causality violation in Ricci-inverse
gravity | 11 pages, accepted for publication in EPJC | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, Ricci-inverse gravity is investigated. It is an alternative
theory of gravity that introduces into the Einstein-Hilbert action an
anti-curvature scalar that is obtained from the anti-curvature tensor which is
the inverse of the Ricci tensor. An axially symmetric spacetime with causality
violation is studied. Two classes of the model are discussed. Different sources
of matter are considered. Then a direct relation between the content of matter
and causality violation is shown. Our results confirm that Ricci-inverse
gravity allows the existence of Closed Time-like Curves (CTCs) that lead to the
violation of causality. Furthermore, a comparison is made between the results
of general relativity and Ricci-inverse gravity. Other spacetimes, such as
G\"{o}del and G\"{o}del-type universes, which are exact solutions of general
relativity and allow for causality violations, are also explored in
Ricci-inverse gravity framework.
| [
{
"created": "Mon, 11 Sep 2023 13:25:22 GMT",
"version": "v1"
}
] | 2023-09-12 | [
[
"de Souza",
"J. C. R.",
""
],
[
"Santos",
"A. F.",
""
]
] | In this paper, Ricci-inverse gravity is investigated. It is an alternative theory of gravity that introduces into the Einstein-Hilbert action an anti-curvature scalar that is obtained from the anti-curvature tensor which is the inverse of the Ricci tensor. An axially symmetric spacetime with causality violation is studied. Two classes of the model are discussed. Different sources of matter are considered. Then a direct relation between the content of matter and causality violation is shown. Our results confirm that Ricci-inverse gravity allows the existence of Closed Time-like Curves (CTCs) that lead to the violation of causality. Furthermore, a comparison is made between the results of general relativity and Ricci-inverse gravity. Other spacetimes, such as G\"{o}del and G\"{o}del-type universes, which are exact solutions of general relativity and allow for causality violations, are also explored in Ricci-inverse gravity framework. |
2211.08032 | Tuan Do | Duy H. Nguyen, Tuyen M. Pham, Thien D. Le, Tuan Q. Do | Anisotropic constant-roll k-inflation model | 15 pages, 11 figures. To appear in Communications in Physics (2023),
a well-established physics journal of Vietnam. Comments are welcome | Communications in Physics 33, 15 (2023) | 10.15625/0868-3166/17360 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we would like to figure out whether a k-inflation model admits
the Bianchi type I metric as its inflationary solution under a constant-roll
condition in the presence of the supergravity motivated coupling between scalar
and vector fields, $f^2(\phi)F_{\mu\nu}F^{\mu\nu}$. As a result, some novel
anisotropic inflationary solutions are shown to appear along with a power-law
one in this scenario. Furthermore, these solutions are numerically confirmed to
be attractive, in contrast to the prediction of the Hawking's cosmic no-hair
conjecture.
| [
{
"created": "Tue, 15 Nov 2022 10:33:47 GMT",
"version": "v1"
}
] | 2023-04-03 | [
[
"Nguyen",
"Duy H.",
""
],
[
"Pham",
"Tuyen M.",
""
],
[
"Le",
"Thien D.",
""
],
[
"Do",
"Tuan Q.",
""
]
] | In this paper, we would like to figure out whether a k-inflation model admits the Bianchi type I metric as its inflationary solution under a constant-roll condition in the presence of the supergravity motivated coupling between scalar and vector fields, $f^2(\phi)F_{\mu\nu}F^{\mu\nu}$. As a result, some novel anisotropic inflationary solutions are shown to appear along with a power-law one in this scenario. Furthermore, these solutions are numerically confirmed to be attractive, in contrast to the prediction of the Hawking's cosmic no-hair conjecture. |
2004.00039 | Javier Rubio | Javier Rubio | Scale symmetry, the Higgs and the Cosmos | 14 pages, 5 figures. Invited talk in Corfu Summer Institute 2019
"School and Workshops on Elementary Particle Physics and Gravity"
(CORFU2019), based on 1712.04956 [astro-ph.CO] and 1811.05984 [astro-ph.CO] | null | null | HIP-2020-8/TH | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review the Higgs-Dilaton model: a scale-invariant extension of the Standard
Model and gravity able to support inflation and dark energy with just an
additional degree of freedom on top of the Standard Model content. Potential
extensions of the simplest realization on the basis of transverse
diffeomorphisms are also discussed.
| [
{
"created": "Tue, 31 Mar 2020 18:12:04 GMT",
"version": "v1"
}
] | 2020-04-03 | [
[
"Rubio",
"Javier",
""
]
] | I review the Higgs-Dilaton model: a scale-invariant extension of the Standard Model and gravity able to support inflation and dark energy with just an additional degree of freedom on top of the Standard Model content. Potential extensions of the simplest realization on the basis of transverse diffeomorphisms are also discussed. |
gr-qc/0102071 | Gabriel Nagy | Robert Geroch, Gabriel Nagy, Oscar Reula | Relativistic Lagrange Formulation | 34 pages, no figures, accepted in J. Math. Phys | J.Math.Phys.42:3789-3808,2001 | 10.1063/1.1364502 | null | gr-qc | null | It is well-known that the equations for a simple fluid can be cast into what
is called their Lagrange formulation. We introduce a notion of a generalized
Lagrange formulation, which is applicable to a wide variety of systems of
partial differential equations. These include numerous systems of physical
interest, in particular, those for various material media in general
relativity. There is proved a key theorem, to the effect that, if the original
(Euler) system admits an initial-value formulation, then so does its
generalized Lagrange formulation.
| [
{
"created": "Wed, 14 Feb 2001 22:55:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Geroch",
"Robert",
""
],
[
"Nagy",
"Gabriel",
""
],
[
"Reula",
"Oscar",
""
]
] | It is well-known that the equations for a simple fluid can be cast into what is called their Lagrange formulation. We introduce a notion of a generalized Lagrange formulation, which is applicable to a wide variety of systems of partial differential equations. These include numerous systems of physical interest, in particular, those for various material media in general relativity. There is proved a key theorem, to the effect that, if the original (Euler) system admits an initial-value formulation, then so does its generalized Lagrange formulation. |
0803.4006 | Sandro Costa | Sandro Silva e Costa | An entirely analytical cosmological model | 4 pages (revtex4), 4 figures | Mod.Phys.Lett.A24:531-540,2009 | 10.1142/S021773230902845X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of the present study is to show that in a particular cosmological
model, with an affine equation of state, one can obtain, besides the background
given by the scale factor, Hubble and deceleration parameters, a representation
in terms of scalar fields and, more important, explicit mathematical
expressions for the density contrast and the power spectrum. Although the model
so obtained is not realistic, it reproduces features observed in some previous
numerical studies and, therefore, it may be useful in the testing of numerical
codes and as a pedagogical tool.
| [
{
"created": "Fri, 28 Mar 2008 17:43:47 GMT",
"version": "v1"
}
] | 2009-04-17 | [
[
"Costa",
"Sandro Silva e",
""
]
] | The purpose of the present study is to show that in a particular cosmological model, with an affine equation of state, one can obtain, besides the background given by the scale factor, Hubble and deceleration parameters, a representation in terms of scalar fields and, more important, explicit mathematical expressions for the density contrast and the power spectrum. Although the model so obtained is not realistic, it reproduces features observed in some previous numerical studies and, therefore, it may be useful in the testing of numerical codes and as a pedagogical tool. |
1411.5613 | Georgios K. Karananas Mr. | Georgios K. Karananas | The particle spectrum of parity-violating Poincar\'e gravitational
theory | v3: erratum discussing contradiction in ghost-free conditions
appended | 2015 Class. Quantum Grav. 32 055012 | 10.1088/0264-9381/32/5/055012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the physical spectrum of the gravitational
theory based on the Poincar\'e group with terms which are at most quadratic in
tetrad and spin connection, allowing for the presence of parity-even as well as
parity-odd invariants. We determine restrictions on the parameters of the
action so that all degrees of freedom propagate and are neither ghosts nor
tachyons. We show that the addition of parity non-conserving invariants extends
the healthy parameter space of the theory. To accomplish our goal, we apply the
weak field approximation around flat spacetime and in order to facilitate the
analysis, we separate the bilinear action for the excitations into completely
independent spin sectors. For this purpose, we employ the spin-projection
operator formalism and extend the original basis built previously, to be able
to handle the parity-odd pieces.
| [
{
"created": "Thu, 20 Nov 2014 17:28:58 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Feb 2015 10:11:45 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Feb 2015 08:37:45 GMT",
"version": "v3"
}
] | 2015-02-19 | [
[
"Karananas",
"Georgios K.",
""
]
] | In this paper we investigate the physical spectrum of the gravitational theory based on the Poincar\'e group with terms which are at most quadratic in tetrad and spin connection, allowing for the presence of parity-even as well as parity-odd invariants. We determine restrictions on the parameters of the action so that all degrees of freedom propagate and are neither ghosts nor tachyons. We show that the addition of parity non-conserving invariants extends the healthy parameter space of the theory. To accomplish our goal, we apply the weak field approximation around flat spacetime and in order to facilitate the analysis, we separate the bilinear action for the excitations into completely independent spin sectors. For this purpose, we employ the spin-projection operator formalism and extend the original basis built previously, to be able to handle the parity-odd pieces. |
2406.13132 | W. S. Hipolito-Ricaldi | J.A.S.Fortunato, W.S. Hipolito-Ricaldi, N. Videla, and J.R. Villanueva | Cosmic slowing down of acceleration with the Chaplygin-Jacobi gas as a
dark fluid | 16 pages, 5 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-nd/4.0/ | A particular generalization of the Chaplygin inflationary model, using the
formalism of Hamilton-Jacobi and elliptic functions, results in a more general
non-linear Chaplygin-type equation of state (Chaplygin-Jacobi model). We
investigate the implementation of this model as a dark energy (DE) fluid to
explain the recent acceleration of the universe. Unlike $\Lambda$CDM and other
Chaplygin-like fluids, where the final fate of the universe is an eternal de
Sitter (dS) phase, the dynamics of this model allow for the possibility of a
decelerating phase in the future, following the current accelerating phase. In
other words, a transient acceleration arises, accounting for the recently
claimed slowing down phenomenon. This Chaplygin-Jacobi model shows important
differences compared to the standard and generalized Chaplygin gas models.
Additionally, we perform a Markov Chain Monte Carlo (MCMC) analysis using
several datasets, including Type Ia Supernovae (SnIa), Cosmic Chronometers
(CC), and Fast Radio Bursts (FRBs), to examine the observational viability of
the model. Our results indicate that a transient phase of accelerated expansion
is not excluded by current observations.
| [
{
"created": "Wed, 19 Jun 2024 00:52:42 GMT",
"version": "v1"
}
] | 2024-06-21 | [
[
"Fortunato",
"J. A. S.",
""
],
[
"Hipolito-Ricaldi",
"W. S.",
""
],
[
"Videla",
"N.",
""
],
[
"Villanueva",
"J. R.",
""
]
] | A particular generalization of the Chaplygin inflationary model, using the formalism of Hamilton-Jacobi and elliptic functions, results in a more general non-linear Chaplygin-type equation of state (Chaplygin-Jacobi model). We investigate the implementation of this model as a dark energy (DE) fluid to explain the recent acceleration of the universe. Unlike $\Lambda$CDM and other Chaplygin-like fluids, where the final fate of the universe is an eternal de Sitter (dS) phase, the dynamics of this model allow for the possibility of a decelerating phase in the future, following the current accelerating phase. In other words, a transient acceleration arises, accounting for the recently claimed slowing down phenomenon. This Chaplygin-Jacobi model shows important differences compared to the standard and generalized Chaplygin gas models. Additionally, we perform a Markov Chain Monte Carlo (MCMC) analysis using several datasets, including Type Ia Supernovae (SnIa), Cosmic Chronometers (CC), and Fast Radio Bursts (FRBs), to examine the observational viability of the model. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations. |
2010.07609 | Alessandro Casalino | Alessandro Casalino, Bruno Sanna, Lorenzo Sebastiani, Sergio Zerbini | Bounce Models within Teleparallel modified gravity | 13 pages, version accepted for publication on PRD | Phys. Rev. D 103, 023514 (2021) | 10.1103/PhysRevD.103.023514 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, working in a Friedman-Lemaitre-Robertson-Walker (FLRW), first,
in the flat case, we recover the generalized Friedman equation of Quantum Loop
cosmology, and therefore the cosmological bounce, in the framework of modified
teleparallel gravity $f(T)$-model, $T$ being the torsion scalar introduced in
teleparallel gravity approach, without invoking unconventional exotic matter.
Furthermore we study the associated perturbations again in a flat FLRW
space-time. Then, we generalize the results to the curved FLRW space-time,
where some issues related to the choice of tetrad exist, by using an
appropriate formulation. In this context, the results of Born-Infeld model are
also investigated.
| [
{
"created": "Thu, 15 Oct 2020 09:11:46 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2021 09:49:57 GMT",
"version": "v2"
}
] | 2021-01-20 | [
[
"Casalino",
"Alessandro",
""
],
[
"Sanna",
"Bruno",
""
],
[
"Sebastiani",
"Lorenzo",
""
],
[
"Zerbini",
"Sergio",
""
]
] | In this paper, working in a Friedman-Lemaitre-Robertson-Walker (FLRW), first, in the flat case, we recover the generalized Friedman equation of Quantum Loop cosmology, and therefore the cosmological bounce, in the framework of modified teleparallel gravity $f(T)$-model, $T$ being the torsion scalar introduced in teleparallel gravity approach, without invoking unconventional exotic matter. Furthermore we study the associated perturbations again in a flat FLRW space-time. Then, we generalize the results to the curved FLRW space-time, where some issues related to the choice of tetrad exist, by using an appropriate formulation. In this context, the results of Born-Infeld model are also investigated. |
1710.00839 | Markus B. Fr\"ob | Markus B. Fr\"ob | Gauge-invariant quantum gravitational corrections to correlation
functions | 34 pages, 1 figure, matches published version | Class. Quant. Grav. 35 (2018) 055006 | 10.1088/1361-6382/aaa74c | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent proposal for gauge-invariant observables in inflation [R. Brunetti
et al., JHEP 1608 (2016) 032] is examined. We give a generalisation of their
construction to general background spacetimes. In flat space, we calculate
one-loop graviton corrections to a scalar two-point function in a general gauge
for the graviton. We explicitely show how the gauge-dependent terms cancel
between the usual self-energy contributions and the additional corrections
inherent in these observables. The one-loop corrections have the expected
functional form, contrary to another recently studied proposal for
gauge-invariant observables [M. B. Fr\"ob, Class. Quant. Grav. 35 (2018)
035005] where this is not the case. Furthermore, we determine the one-loop
graviton corrections to the four-point coupling of the gauge-invariant scalar
field, and the corresponding running of the coupling constant induced by
graviton loops. Interestingly, the $\beta$ function is negative for all values
of the non-minimal coupling of the scalar field to curvature.
| [
{
"created": "Mon, 2 Oct 2017 18:00:19 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Feb 2018 14:01:51 GMT",
"version": "v2"
}
] | 2018-02-02 | [
[
"Fröb",
"Markus B.",
""
]
] | A recent proposal for gauge-invariant observables in inflation [R. Brunetti et al., JHEP 1608 (2016) 032] is examined. We give a generalisation of their construction to general background spacetimes. In flat space, we calculate one-loop graviton corrections to a scalar two-point function in a general gauge for the graviton. We explicitely show how the gauge-dependent terms cancel between the usual self-energy contributions and the additional corrections inherent in these observables. The one-loop corrections have the expected functional form, contrary to another recently studied proposal for gauge-invariant observables [M. B. Fr\"ob, Class. Quant. Grav. 35 (2018) 035005] where this is not the case. Furthermore, we determine the one-loop graviton corrections to the four-point coupling of the gauge-invariant scalar field, and the corresponding running of the coupling constant induced by graviton loops. Interestingly, the $\beta$ function is negative for all values of the non-minimal coupling of the scalar field to curvature. |
0911.1187 | Tomohiro Harada | Tomohiro Harada, Umpei Miyamoto, Naoki Tsukamoto | Uniqueness of static spherically symmetric vacuum solutions in the IR
limit of Ho\v{r}ava-Lifshitz gravity | 10 pages, accepted for publication in International Journal of Modern
Physics D | Int.J.Mod.Phys.D20:111-118,2011 | 10.1142/S0218271811018652 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate static spherically symmetric vacuum solutions in the IR limit
of projectable nonrelativistic quantum gravity, including the renormalisable
quantum gravity recently proposed by Ho\v{r}ava. It is found that the
projectability condition plays an important role. Without the cosmological
constant, the spacetime is uniquely given by the Schwarzschild solution. With
the cosmological constant, the spacetime is uniquely given by the Kottler
(Schwarzschild-(anti) de Sitter) solution for the entirely vacuum spacetime.
However, in addition to the Kottler solution, the static spherical and
hyperbolic universes are uniquely admissible for the locally empty region, for
the positive and negative cosmological constants, respectively, if its
nonvanishing contribution to the global Hamiltonian constraint can be
compensated by that from the nonempty or nonstatic region. This implies that
static spherically symmetric entirely vacuum solutions would not admit the
freedom to reproduce the observed flat rotation curves of galaxies. On the
other hand, the result for locally empty regions implies that the IR limit of
nonrelativistic quantum gravity theories does not simply recover general
relativity but includes it.
| [
{
"created": "Fri, 6 Nov 2009 07:32:12 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 2010 08:11:22 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Oct 2010 02:28:38 GMT",
"version": "v3"
}
] | 2011-03-04 | [
[
"Harada",
"Tomohiro",
""
],
[
"Miyamoto",
"Umpei",
""
],
[
"Tsukamoto",
"Naoki",
""
]
] | We investigate static spherically symmetric vacuum solutions in the IR limit of projectable nonrelativistic quantum gravity, including the renormalisable quantum gravity recently proposed by Ho\v{r}ava. It is found that the projectability condition plays an important role. Without the cosmological constant, the spacetime is uniquely given by the Schwarzschild solution. With the cosmological constant, the spacetime is uniquely given by the Kottler (Schwarzschild-(anti) de Sitter) solution for the entirely vacuum spacetime. However, in addition to the Kottler solution, the static spherical and hyperbolic universes are uniquely admissible for the locally empty region, for the positive and negative cosmological constants, respectively, if its nonvanishing contribution to the global Hamiltonian constraint can be compensated by that from the nonempty or nonstatic region. This implies that static spherically symmetric entirely vacuum solutions would not admit the freedom to reproduce the observed flat rotation curves of galaxies. On the other hand, the result for locally empty regions implies that the IR limit of nonrelativistic quantum gravity theories does not simply recover general relativity but includes it. |
2006.05287 | Nikolay Fimin N | Victor Vedenyapin, Nikolay Fimin and Valery Chechetkin | The properties of Vlasov-Maxwell-Einstein equations and its applications
to cosmological models | null | European Physical Journal Plus (2020) 135: 400 | 10.1140/epjp/s13360-020-00412-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The method of obtaining of Vlasov-type equations for systems of interacting
massive charged particles from the general relativistic Einstein-Hilbert action
is considered. An effective approach to synchronizing the proper times of
various particles of a many-particle system is proposed. Based on the resulting
expressions for the relativistic actions, an analysis of composite structure of
cosmological term in Einstein's equations is performed.
| [
{
"created": "Tue, 9 Jun 2020 14:30:17 GMT",
"version": "v1"
}
] | 2020-06-11 | [
[
"Vedenyapin",
"Victor",
""
],
[
"Fimin",
"Nikolay",
""
],
[
"Chechetkin",
"Valery",
""
]
] | The method of obtaining of Vlasov-type equations for systems of interacting massive charged particles from the general relativistic Einstein-Hilbert action is considered. An effective approach to synchronizing the proper times of various particles of a many-particle system is proposed. Based on the resulting expressions for the relativistic actions, an analysis of composite structure of cosmological term in Einstein's equations is performed. |
1407.8167 | Steffen Gielen | Steffen Gielen, Daniele Oriti | Quantum cosmology from quantum gravity condensates: cosmological
variables and lattice-refined dynamics | 7 pages, APS style, revtex; v2: small changes in presentation,
results unchanged, matches journal version | New J. Phys. 16 (2014) 123004 | 10.1088/1367-2630/16/12/123004 | AEI-2014-032 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of group field theory condensate cosmology, we clarify the
extraction of cosmological variables from the microscopic quantum gravity
degrees of freedom. We show that an important implication of the second
quantized formalism is the dependence of cosmological variables and equations
on the quantum gravitational atomic number N (number of spin network
vertices/elementary simplices). We clarify the relation of the effective
cosmological equations with loop quantum cosmology, understood as an effective
(hydrodynamic-like) approximation of a more fundamental quantum gravity theory.
By doing so, we provide a fundamental basis to the idea of lattice refinement,
showing the dependence of the effective cosmological connection on N, and hence
indirectly on the scale factor. Our results open a new arena for exploring
effective cosmological dynamics, as this depends crucially on the new
observable N, which is entirely of quantum gravitational origin.
| [
{
"created": "Wed, 30 Jul 2014 19:36:29 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Nov 2014 00:31:14 GMT",
"version": "v2"
}
] | 2014-12-03 | [
[
"Gielen",
"Steffen",
""
],
[
"Oriti",
"Daniele",
""
]
] | In the context of group field theory condensate cosmology, we clarify the extraction of cosmological variables from the microscopic quantum gravity degrees of freedom. We show that an important implication of the second quantized formalism is the dependence of cosmological variables and equations on the quantum gravitational atomic number N (number of spin network vertices/elementary simplices). We clarify the relation of the effective cosmological equations with loop quantum cosmology, understood as an effective (hydrodynamic-like) approximation of a more fundamental quantum gravity theory. By doing so, we provide a fundamental basis to the idea of lattice refinement, showing the dependence of the effective cosmological connection on N, and hence indirectly on the scale factor. Our results open a new arena for exploring effective cosmological dynamics, as this depends crucially on the new observable N, which is entirely of quantum gravitational origin. |
gr-qc/9601010 | Steve Brandt | Steven R. Brandt, Edward Seidel (National Center for Supercomputing
Applications, Department of Physics, Univ. of Illinois at Urbana-Champaign) | The Evolution of Distorted Rotating Black Holes III: Initial Data | 16 pages | Phys.Rev. D54 (1996) 1403-1416 | 10.1103/PhysRevD.54.1403 | null | gr-qc | null | In this paper we study a new family of black hole initial data sets
corresponding to distorted ``Kerr'' black holes with moderate rotation
parameters, and distorted Schwarzschild black holes with even- and odd-parity
radiation. These data sets build on the earlier rotating black holes of Bowen
and York and the distorted Brill wave plus black hole data sets. We describe
the construction of this large family of rotating black holes. We present a
systematic study of important properties of these data sets, such as the size
and shape of their apparent horizons, and the maximum amount of radiation that
can leave the system during evolution. These data sets should be a very useful
starting point for studying the evolution of highly dynamical black holes and
can easily be extended to 3D.
| [
{
"created": "Tue, 9 Jan 1996 17:03:33 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Brandt",
"Steven R.",
"",
"National Center for Supercomputing\n Applications, Department of Physics, Univ. of Illinois at Urbana-Champaign"
],
[
"Seidel",
"Edward",
"",
"National Center for Supercomputing\n Applications, Department of Physics, Univ. of Illinois at Urbana-Cha... | In this paper we study a new family of black hole initial data sets corresponding to distorted ``Kerr'' black holes with moderate rotation parameters, and distorted Schwarzschild black holes with even- and odd-parity radiation. These data sets build on the earlier rotating black holes of Bowen and York and the distorted Brill wave plus black hole data sets. We describe the construction of this large family of rotating black holes. We present a systematic study of important properties of these data sets, such as the size and shape of their apparent horizons, and the maximum amount of radiation that can leave the system during evolution. These data sets should be a very useful starting point for studying the evolution of highly dynamical black holes and can easily be extended to 3D. |
1505.08084 | Neil J. Cornish | Neil J. Cornish and Joseph D. Romano | When is a gravitational-wave signal stochastic? | 14 pages, 10 figures | Phys. Rev. D 92, 042001 (2015) | 10.1103/PhysRevD.92.042001 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the detection of gravitational-wave backgrounds in the context of
Bayesian inference and suggest a practical definition of what it means for a
signal to be considered stochastic---namely, that the Bayesian evidence favors
a stochastic signal model over a deterministic signal model. A signal can
further be classified as Gaussian-stochastic if a Gaussian signal model is
favored. In our analysis we use Bayesian model selection to choose between
several signal and noise models for simulated data consisting of uncorrelated
Gaussian detector noise plus a superposition of sinusoidal signals from an
astrophysical population of gravitational-wave sources. For simplicity, we
consider co-located and co-aligned detectors with white detector noise, but the
method can be extended to more realistic detector configurations and power
spectra. The general trend we observe is that a deterministic model is favored
for small source numbers, a non-Gaussian stochastic model is preferred for
intermediate source numbers, and a Gaussian stochastic model is preferred for
large source numbers. However, there is very large variation between individual
signal realizations, leading to fuzzy boundaries between the three regimes. We
find that a hybrid, trans-dimensional model comprised of a deterministic signal
model for individual bright sources and a Gaussian-stochastic signal model for
the remaining confusion background outperforms all other models in most
instances.
| [
{
"created": "Fri, 29 May 2015 15:14:22 GMT",
"version": "v1"
}
] | 2015-08-12 | [
[
"Cornish",
"Neil J.",
""
],
[
"Romano",
"Joseph D.",
""
]
] | We discuss the detection of gravitational-wave backgrounds in the context of Bayesian inference and suggest a practical definition of what it means for a signal to be considered stochastic---namely, that the Bayesian evidence favors a stochastic signal model over a deterministic signal model. A signal can further be classified as Gaussian-stochastic if a Gaussian signal model is favored. In our analysis we use Bayesian model selection to choose between several signal and noise models for simulated data consisting of uncorrelated Gaussian detector noise plus a superposition of sinusoidal signals from an astrophysical population of gravitational-wave sources. For simplicity, we consider co-located and co-aligned detectors with white detector noise, but the method can be extended to more realistic detector configurations and power spectra. The general trend we observe is that a deterministic model is favored for small source numbers, a non-Gaussian stochastic model is preferred for intermediate source numbers, and a Gaussian stochastic model is preferred for large source numbers. However, there is very large variation between individual signal realizations, leading to fuzzy boundaries between the three regimes. We find that a hybrid, trans-dimensional model comprised of a deterministic signal model for individual bright sources and a Gaussian-stochastic signal model for the remaining confusion background outperforms all other models in most instances. |
1403.5434 | Maciej Maliborski | Maciej Maliborski and Andrzej Rostworowski | What drives AdS unstable? | 7 pages, 4 figures; v2: minor corrections in the text | Phys. Rev. D 89, 124006 (2014) | 10.1103/PhysRevD.89.124006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the spectrum of linear perturbations of standing wave solutions
discussed in [Phys. Rev. D 87, 123006 (2013)], as the first step to investigate
the stability of globally regular, asymptotically AdS, time-periodic solutions
discovered in [Phys. Rev. Lett. 111 051102 (2013)]. We show that while this
spectrum is only asymptotically nondispersive (as contrasted with the pure AdS
case), putting a small standing wave solution on the top of AdS solution indeed
prevents the turbulent instability. Thus we support the idea advocated in
previous works that nondispersive character of the spectrum of linear
perturbations of AdS space is crucial for the conjectured turbulent
instability.
| [
{
"created": "Fri, 21 Mar 2014 12:10:25 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Apr 2014 10:05:08 GMT",
"version": "v2"
}
] | 2014-06-11 | [
[
"Maliborski",
"Maciej",
""
],
[
"Rostworowski",
"Andrzej",
""
]
] | We calculate the spectrum of linear perturbations of standing wave solutions discussed in [Phys. Rev. D 87, 123006 (2013)], as the first step to investigate the stability of globally regular, asymptotically AdS, time-periodic solutions discovered in [Phys. Rev. Lett. 111 051102 (2013)]. We show that while this spectrum is only asymptotically nondispersive (as contrasted with the pure AdS case), putting a small standing wave solution on the top of AdS solution indeed prevents the turbulent instability. Thus we support the idea advocated in previous works that nondispersive character of the spectrum of linear perturbations of AdS space is crucial for the conjectured turbulent instability. |
gr-qc/0411136 | S. Mignemi | M. Melis and S. Mignemi | Two-dimensional static black holes with pointlike sources | 11 pages, 2 figures, LaTeX. v.2: an error in the sign of the
energy-momentum tensor has been corrected; the solutions are slightly
modified | Gen.Rel.Grav. 37 (2005) 1313-1322 | 10.1007/s10714-005-0114-z | null | gr-qc | null | We study the static black hole solutions of generalized two-dimensional
dilaton-gravity theories generated by pointlike mass sources, in the hypothesis
that the matter is conformally coupled. We also discuss the motion of test
particles. Due to conformal coupling, these follow the geodesics of a metric
obtained by rescaling the canonical metric with the dilaton.
| [
{
"created": "Mon, 29 Nov 2004 11:04:40 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Mar 2005 10:09:28 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Melis",
"M.",
""
],
[
"Mignemi",
"S.",
""
]
] | We study the static black hole solutions of generalized two-dimensional dilaton-gravity theories generated by pointlike mass sources, in the hypothesis that the matter is conformally coupled. We also discuss the motion of test particles. Due to conformal coupling, these follow the geodesics of a metric obtained by rescaling the canonical metric with the dilaton. |
2407.14851 | Ramon Torres | Ramon Torres | Observational and theoretical aspects of Superspinars | 30 pages, 15 figures | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | This article delves into the observational signatures and theoretical
underpinnings of rotating astrophysical objects, with a particular focus on
superspinars -exotic objects characterized by preventing the formation of event
horizons due to their high angular momentum.
While solutions within General Relativity (Kerr superspinars) predict such
objects, their classical forms harbor naked singularities, violate causality,
and exhibit problematic repulsive gravitational effects. These characteristics
render classical superspinars theoretically objectionable, leading to the
consideration of them as physically implausible. On the other hand, the
incompatibility between General Relativity and Quantum Mechanics suggests the
exploration of alternative models, particularly those in which Quantum Gravity
dominates the core, yielding regular superspinars.
This work demonstrates that regular superspinars avoid all the complications
associated with Kerr superspinars. From a phenomenological standpoint, it is
shown that the silhouettes of regular superspinars are markedly distinct from
those of black holes and classical Kerr superspinars. To substantiate these
differences, we perform a comprehensive analysis of inner null geodesics and
investigate the structure of the Planckian region within regular superspinars.
Our study reveals that only regular superspinars provide the potential for
distant observers to directly observe the extremely high curvature regions
within their interiors.
| [
{
"created": "Sat, 20 Jul 2024 11:36:26 GMT",
"version": "v1"
}
] | 2024-07-23 | [
[
"Torres",
"Ramon",
""
]
] | This article delves into the observational signatures and theoretical underpinnings of rotating astrophysical objects, with a particular focus on superspinars -exotic objects characterized by preventing the formation of event horizons due to their high angular momentum. While solutions within General Relativity (Kerr superspinars) predict such objects, their classical forms harbor naked singularities, violate causality, and exhibit problematic repulsive gravitational effects. These characteristics render classical superspinars theoretically objectionable, leading to the consideration of them as physically implausible. On the other hand, the incompatibility between General Relativity and Quantum Mechanics suggests the exploration of alternative models, particularly those in which Quantum Gravity dominates the core, yielding regular superspinars. This work demonstrates that regular superspinars avoid all the complications associated with Kerr superspinars. From a phenomenological standpoint, it is shown that the silhouettes of regular superspinars are markedly distinct from those of black holes and classical Kerr superspinars. To substantiate these differences, we perform a comprehensive analysis of inner null geodesics and investigate the structure of the Planckian region within regular superspinars. Our study reveals that only regular superspinars provide the potential for distant observers to directly observe the extremely high curvature regions within their interiors. |
0905.1785 | Antoine Petiteau | Antoine Petiteau, Yu Shang, Stanislav Babak | The search for black hole binaries using a genetic algorithm | 11 pages, 4 figures, proceeding for GWDAW13 (Puerto Rico) | null | 10.1088/0264-9381/26/20/204011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we use genetic algorithm to search for the gravitational wave
signal from the inspiralling massive Black Hole binaries in the simulated LISA
data. We consider a single signal in the Gaussian instrumental noise. This is a
first step in preparation for analysis of the third round of the mock LISA data
challenge. We have extended a genetic algorithm utilizing the properties of the
signal and the detector response function. The performance of this method is
comparable, if not better, to already existing algorithms.
| [
{
"created": "Tue, 12 May 2009 08:21:11 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Aug 2009 08:42:37 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Petiteau",
"Antoine",
""
],
[
"Shang",
"Yu",
""
],
[
"Babak",
"Stanislav",
""
]
] | In this work we use genetic algorithm to search for the gravitational wave signal from the inspiralling massive Black Hole binaries in the simulated LISA data. We consider a single signal in the Gaussian instrumental noise. This is a first step in preparation for analysis of the third round of the mock LISA data challenge. We have extended a genetic algorithm utilizing the properties of the signal and the detector response function. The performance of this method is comparable, if not better, to already existing algorithms. |
2006.00855 | Daniele Gregoris | Daniele Gregoris, Kjell Rosquist | Observational backreaction in discrete black holes lattice cosmological
models | Matches published version | The European Physical Journal Plus 136:45 (2021) | 10.1140/epjp/s13360-020-00998-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Applying the Sachs formalism, the optical properties encoded in the distance
modulus are studied along curves exhibiting local rotational symmetry for some
closed inhomogeneous cosmological models whose mass content is discretized by
Schwarzschild-like sources. These models may challenge the concordance model in
its use of the distance modulus data of type Ia supernovae, because they do not
violate any energy condition. This result relies only on the symmetry
properties considered, and not on the way in which the mass is discretized. The
models with different number of sources are then compared among themselves and
with a Friedmann-Lemaitre-Robertson-Walker model with the same total mass
content by introducing a compactness parameter. The analysis shows that
observational backreaction occurs because increasing the number of sources the
features of a universe with a continuous matter distribution are not recovered.
Our models are shown to exhibit a non-trivial relationship between kinematical,
dynamical and observational backreactions, the kinematical one being
asymptotically decreasing while the latter two are present. Furthermore, the
electric part of the Weyl tensor contributes to the luminosity distance by
affecting the evolution of the scale factor, while the magnetic part has an
indirect role by affecting only the evolution of the former
| [
{
"created": "Mon, 1 Jun 2020 11:21:15 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Jan 2021 18:25:21 GMT",
"version": "v2"
}
] | 2021-01-19 | [
[
"Gregoris",
"Daniele",
""
],
[
"Rosquist",
"Kjell",
""
]
] | Applying the Sachs formalism, the optical properties encoded in the distance modulus are studied along curves exhibiting local rotational symmetry for some closed inhomogeneous cosmological models whose mass content is discretized by Schwarzschild-like sources. These models may challenge the concordance model in its use of the distance modulus data of type Ia supernovae, because they do not violate any energy condition. This result relies only on the symmetry properties considered, and not on the way in which the mass is discretized. The models with different number of sources are then compared among themselves and with a Friedmann-Lemaitre-Robertson-Walker model with the same total mass content by introducing a compactness parameter. The analysis shows that observational backreaction occurs because increasing the number of sources the features of a universe with a continuous matter distribution are not recovered. Our models are shown to exhibit a non-trivial relationship between kinematical, dynamical and observational backreactions, the kinematical one being asymptotically decreasing while the latter two are present. Furthermore, the electric part of the Weyl tensor contributes to the luminosity distance by affecting the evolution of the scale factor, while the magnetic part has an indirect role by affecting only the evolution of the former |
2109.14706 | Nima Laal | Zaven Arzoumanian, Paul T. Baker, Harsha Blumer, Bence Becsy, Adam
Brazier, Paul R. Brook, Sarah Burke-Spolaor, Maria Charisi, Shami Chatterjee,
Siyuan Chen, James M. Cordes, Neil J. Cornish, Fronefield Crawford, H.
Thankful Cromartie, Megan E. DeCesar, Dallas M. DeGan, Paul B. Demorest,
Timothy Dolch, Brendan Drachler, Justin A. Ellis, Elizabeth C. Ferrara,
William Fiore, Emmanuel Fonseca, Nathan Garver-Daniels, Peter A. Gentile,
Deborah C. Good, Jeffrey S. Hazboun, A. Miguel Holgado, Kristina Islo, Ross
J. Jennings, Megan L. Jones, Andrew R. Kaiser, David L. Kaplan, Luke Zoltan
Kelley, Joey Shapiro Key, Nima Laal, Michael T. Lam, T. Joseph W. Lazio,
Duncan R. Lorimer, Tingting Liu, Jing Luo, Ryan S. Lynch, Dustin R. Madison,
Alexander McEwen, Maura A. McLaughlin, Chiara M. F. Mingarelli, Cherry Ng,
David J. Nice, Ken D. Olum, Timothy T. Pennucci, Nihan S. Pol, Scott M.
Ransom, Paul S. Ray, Joseph D. Romano, Shashwat C. Sardesai, Brent J.
Shapiro-Albert, Xavier Siemens, Joseph Simon, Magdalena S. Siwek, Renee
Spiewak, Ingrid H. Stairs, Daniel R. Stinebring, Kevin Stovall, Jerry P. Sun,
Joseph K. Swiggum, Stephen R. Taylor, Jacob E. Turner, Michele Vallisneri,
Sarah J. Vigeland, Haley M. Wahl, Caitlin A. Witt (for the NANOGrav
Collaboration) | The NANOGrav 12.5-year data set: Search for Non-Einsteinian Polarization
Modes in theGravitational-Wave Background | 24 pages, 18 figures, 3 appendices. Please send any
comments/questions to Nima Laal (laaln@oregonstate.edu) | The Astrophysical Journal Letters, vol. 923, no. 2, p. L22, Dec.
2021 | 10.3847/2041-8213/ac401c | null | gr-qc astro-ph.GA astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We search NANOGrav's 12.5-year data set for evidence of a gravitational wave
background (GWB) with all the spatial correlations allowed by general metric
theories of gravity. We find no substantial evidence in favor of the existence
of such correlations in our data. We find that scalar-transverse (ST)
correlations yield signal-to-noise ratios and Bayes factors that are higher
than quadrupolar (tensor transverse, TT) correlations. Specifically, we find ST
correlations with a signal-to-noise ratio of 2.8 that are preferred over TT
correlations (Hellings and Downs correlations) with Bayesian odds of about
20:1. However, the significance of ST correlations is reduced dramatically when
we include modeling of the Solar System ephemeris systematics and/or remove
pulsar J0030$+$0451 entirely from consideration. Even taking the nominal
signal-to-noise ratios at face value, analyses of simulated data sets show that
such values are not extremely unlikely to be observed in cases where only the
usual TT modes are present in the GWB. In the absence of a detection of any
polarization mode of gravity, we place upper limits on their amplitudes for a
spectral index of $\gamma = 5$ and a reference frequency of $f_\text{yr} = 1
\text{yr}^{-1}$. Among the upper limits for eight general families of metric
theories of gravity, we find the values of $A^{95\%}_{TT} = (9.7 \pm 0.4)\times
10^{-16}$ and $A^{95\%}_{ST} = (1.4 \pm 0.03)\times 10^{-15}$ for the family of
metric spacetime theories that contain both TT and ST modes.
| [
{
"created": "Wed, 29 Sep 2021 20:30:19 GMT",
"version": "v1"
}
] | 2021-12-20 | [
[
"Arzoumanian",
"Zaven",
"",
"for the NANOGrav\n Collaboration"
],
[
"Baker",
"Paul T.",
"",
"for the NANOGrav\n Collaboration"
],
[
"Blumer",
"Harsha",
"",
"for the NANOGrav\n Collaboration"
],
[
"Becsy",
"Bence",
"",
"for the NANOGrav... | We search NANOGrav's 12.5-year data set for evidence of a gravitational wave background (GWB) with all the spatial correlations allowed by general metric theories of gravity. We find no substantial evidence in favor of the existence of such correlations in our data. We find that scalar-transverse (ST) correlations yield signal-to-noise ratios and Bayes factors that are higher than quadrupolar (tensor transverse, TT) correlations. Specifically, we find ST correlations with a signal-to-noise ratio of 2.8 that are preferred over TT correlations (Hellings and Downs correlations) with Bayesian odds of about 20:1. However, the significance of ST correlations is reduced dramatically when we include modeling of the Solar System ephemeris systematics and/or remove pulsar J0030$+$0451 entirely from consideration. Even taking the nominal signal-to-noise ratios at face value, analyses of simulated data sets show that such values are not extremely unlikely to be observed in cases where only the usual TT modes are present in the GWB. In the absence of a detection of any polarization mode of gravity, we place upper limits on their amplitudes for a spectral index of $\gamma = 5$ and a reference frequency of $f_\text{yr} = 1 \text{yr}^{-1}$. Among the upper limits for eight general families of metric theories of gravity, we find the values of $A^{95\%}_{TT} = (9.7 \pm 0.4)\times 10^{-16}$ and $A^{95\%}_{ST} = (1.4 \pm 0.03)\times 10^{-15}$ for the family of metric spacetime theories that contain both TT and ST modes. |
2002.06573 | Pardyumn Kumar Sahoo | I. Radinschi, P.K. Sahoo, Th. Grammenos, S. Chattopadhyay and M. M.
Cazacu | Localization of Energy and Momentum in an Asymptotically
Reissner-Nordstr\"om Non-singular Black Hole Space-time Geometry | To appear in Universe | Universe, 6(5) (2020) 69 | 10.3390/universe6050069 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The space-time geometry exterior to a new four-dimensional, spherically
symmetric and charged black hole solution that, through a coupling of general
relativity with a non-linear electrodynamics, is everywhere non-singular, for
small $r$ it behaves as a de Sitter metric, and asymptotically it behaves as
the Reissner-Nordstr\"{o}m metric, is considered in order to study the
energy-momentum localization. For the calculation of the energy and momentum
distributions, the Einstein, Landau-Lifshitz, Weinberg and M\o ller
energy-momentum complexes have been applied. The results obtained show that in
all prescriptions the energy depends on the mass $M$ of the black hole, the
charge $q$, two parameters $% a\in \mathbb{Z}^+$ and $\gamma\in \mathbb{R}^+$,
and on the radial coordinate $r$. The calculations performed in each
prescription show that all the momenta vanish. Additionally, some limiting and
particular cases for $r$ and $q$ are studied, and a possible connection with
strong gravitational lensing and micro lensing is attempted.
| [
{
"created": "Sun, 16 Feb 2020 13:11:18 GMT",
"version": "v1"
},
{
"created": "Thu, 21 May 2020 06:13:44 GMT",
"version": "v2"
}
] | 2020-05-26 | [
[
"Radinschi",
"I.",
""
],
[
"Sahoo",
"P. K.",
""
],
[
"Grammenos",
"Th.",
""
],
[
"Chattopadhyay",
"S.",
""
],
[
"Cazacu",
"M. M.",
""
]
] | The space-time geometry exterior to a new four-dimensional, spherically symmetric and charged black hole solution that, through a coupling of general relativity with a non-linear electrodynamics, is everywhere non-singular, for small $r$ it behaves as a de Sitter metric, and asymptotically it behaves as the Reissner-Nordstr\"{o}m metric, is considered in order to study the energy-momentum localization. For the calculation of the energy and momentum distributions, the Einstein, Landau-Lifshitz, Weinberg and M\o ller energy-momentum complexes have been applied. The results obtained show that in all prescriptions the energy depends on the mass $M$ of the black hole, the charge $q$, two parameters $% a\in \mathbb{Z}^+$ and $\gamma\in \mathbb{R}^+$, and on the radial coordinate $r$. The calculations performed in each prescription show that all the momenta vanish. Additionally, some limiting and particular cases for $r$ and $q$ are studied, and a possible connection with strong gravitational lensing and micro lensing is attempted. |
0705.1743 | Zhen-Hua Zhao | Zhen-Hua Zhao, Yu-Xiao Liu, Xi-Guo Li | Gravitational Corrections to the Energy-Levels of a Hydrogen Atom | 7 pages | Commun.Theor.Phys.47:658-662,2007 | 10.1088/0253-6102/47/4/018 | null | gr-qc | null | The first order perturbations of the energy levels of a hydrogen atom in
central internal gravitational field are investigated. The internal
gravitational field is produced by the mass of the atomic nucleus. The energy
shifts are calculated for the relativistic 1S, 2S, 2P, 3S, 3P, 3D, 4S and 4P
levels with Schwarzschild metric. The calculated results show that the
gravitational corrections are sensitive to the total angular momentum quantum
number.
| [
{
"created": "Sat, 12 May 2007 00:47:33 GMT",
"version": "v1"
}
] | 2009-03-19 | [
[
"Zhao",
"Zhen-Hua",
""
],
[
"Liu",
"Yu-Xiao",
""
],
[
"Li",
"Xi-Guo",
""
]
] | The first order perturbations of the energy levels of a hydrogen atom in central internal gravitational field are investigated. The internal gravitational field is produced by the mass of the atomic nucleus. The energy shifts are calculated for the relativistic 1S, 2S, 2P, 3S, 3P, 3D, 4S and 4P levels with Schwarzschild metric. The calculated results show that the gravitational corrections are sensitive to the total angular momentum quantum number. |
gr-qc/0205129 | Roberto Casadio | Roberto Casadio, Lorenzo Mazzacurati | Bulk shape of brane-world black holes | 10 pages, MPLA style, 5 figures, accepted for publication in MPLA | Mod.Phys.Lett.A18:651-660,2003 | 10.1142/S0217732303009794 | null | gr-qc astro-ph hep-ph hep-th | null | We propose a method to extend into the bulk asymptotically flat static
spherically symmetric brane-world metrics. We employ the multipole (1/r)
expansion in order to allow exact integration of the relevant equations along
the (fifth) extra coordinate and make contact with the parameterized
post-Newtonian formalism. We apply our method to three families of solutions
previously appeared as candidates of black holes in the brane world and show
that the shape of the horizon is very likely a flat ``pancake'' for
astrophysical sources.
| [
{
"created": "Thu, 30 May 2002 12:53:22 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Feb 2003 08:58:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Casadio",
"Roberto",
""
],
[
"Mazzacurati",
"Lorenzo",
""
]
] | We propose a method to extend into the bulk asymptotically flat static spherically symmetric brane-world metrics. We employ the multipole (1/r) expansion in order to allow exact integration of the relevant equations along the (fifth) extra coordinate and make contact with the parameterized post-Newtonian formalism. We apply our method to three families of solutions previously appeared as candidates of black holes in the brane world and show that the shape of the horizon is very likely a flat ``pancake'' for astrophysical sources. |
gr-qc/9710080 | Bernard F. Schutz | B. F. Schutz | Introduction to the Analysis of Low-Frequency Gravitational Wave Data | 20 pages | null | null | AEI-044(B) | gr-qc | null | The space-based gravitational wave detector LISA will observe in the
low-frequency gravitational-wave band (0.1 mHz up to 1 Hz). LISA will search
for a variety of expected signals, and when it detects a signal it will have to
determine a number of parameters, such as the location of the source on the sky
and the signal's polarisation. This requires pattern-matching, called matched
filtering, which uses the best available theoretical predictions about the
characteristics of waveforms. All the estimates of the sensitivity of LISA to
various sources assume that the data analysis is done in the optimum way.
Because these techniques are unfamiliar to many young physicists, I use the
first part of this lecture to give a very basic introduction to time-series
data analysis, including matched filtering. The second part of the lecture
applies these techniques to LISA, showing how estimates of LISA's sensitivity
can be made, and briefly commenting on aspects of the signal-analysis problem
that are special to LISA.
| [
{
"created": "Wed, 15 Oct 1997 09:34:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schutz",
"B. F.",
""
]
] | The space-based gravitational wave detector LISA will observe in the low-frequency gravitational-wave band (0.1 mHz up to 1 Hz). LISA will search for a variety of expected signals, and when it detects a signal it will have to determine a number of parameters, such as the location of the source on the sky and the signal's polarisation. This requires pattern-matching, called matched filtering, which uses the best available theoretical predictions about the characteristics of waveforms. All the estimates of the sensitivity of LISA to various sources assume that the data analysis is done in the optimum way. Because these techniques are unfamiliar to many young physicists, I use the first part of this lecture to give a very basic introduction to time-series data analysis, including matched filtering. The second part of the lecture applies these techniques to LISA, showing how estimates of LISA's sensitivity can be made, and briefly commenting on aspects of the signal-analysis problem that are special to LISA. |
1801.03031 | Medine Ildes | Metin Arik, Medine Ildes, Mikhail B. Sheftel | Inflation and Linear Expansion in the Radiation Dominated era in
Jordan-Brans-Dicke Cosmology | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present several features of a cosmological model based on the
Brans-Dicke-Jordan-Thirry action which is scale invariant with a quartic
potential for the Jordan scalar field. We show that the radiation dominated era
starts with a closed universe which expands exponentially and the late
radiation dominated era expands linearly. We find that there may be a
scale-invariant phase with stiff matter between these two radiation dominated
eras. The introduction of matter in the linearly expanding universe causes
deceleration.
| [
{
"created": "Tue, 9 Jan 2018 16:53:45 GMT",
"version": "v1"
}
] | 2018-01-10 | [
[
"Arik",
"Metin",
""
],
[
"Ildes",
"Medine",
""
],
[
"Sheftel",
"Mikhail B.",
""
]
] | We present several features of a cosmological model based on the Brans-Dicke-Jordan-Thirry action which is scale invariant with a quartic potential for the Jordan scalar field. We show that the radiation dominated era starts with a closed universe which expands exponentially and the late radiation dominated era expands linearly. We find that there may be a scale-invariant phase with stiff matter between these two radiation dominated eras. The introduction of matter in the linearly expanding universe causes deceleration. |
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