id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0101014 | Janna Levin | John D. Barrow and Janna Levin | The twin paradox in compact spaces | to be published in PRA, 3 pages | Phys.Rev. A63 (2001) 044104 | 10.1103/PhysRevA.63.044104 | null | gr-qc astro-ph math-ph math.MP | null | Twins travelling at constant relative velocity will each see the other's time
dilate leading to the apparent paradox that each twin believes the other ages
more slowly. In a finite space, the twins can both be on inertial, periodic
orbits so that they have the opportunity to compare their ages when their paths
cross. As we show, they will agree on their respective ages and avoid the
paradox. The resolution relies on the selection of a preferred frame singled
out by the topology of the space.
| [
{
"created": "Tue, 2 Jan 2001 18:58:10 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Barrow",
"John D.",
""
],
[
"Levin",
"Janna",
""
]
] | Twins travelling at constant relative velocity will each see the other's time dilate leading to the apparent paradox that each twin believes the other ages more slowly. In a finite space, the twins can both be on inertial, periodic orbits so that they have the opportunity to compare their ages when their paths cross. As we show, they will agree on their respective ages and avoid the paradox. The resolution relies on the selection of a preferred frame singled out by the topology of the space. |
1010.5122 | Hajime Ishimori | Hajime Isimori | Renormalizable Quantum Gravity in Low Energy without Violating Unitarity | 19 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce new techniques that can preserve unitarity of the system
including ghost particles. Negative norms of the particles can be involved in
zero-norm states by constraints of the physical space. These are useful to
apply the higher-derivative propagator for quantum gravity to suppress
divergences of vacuum energy and graviton mass correction. The quantum effects
are mainly depending on the ghost mass scale. As the scale can be chosen in any
order, the observed cosmological constant is realized. Further, applying ghost
partners for the standard model particles, quantum gravity with matter fields
becomes renormalizable with power counting arguments.
| [
{
"created": "Mon, 25 Oct 2010 13:44:15 GMT",
"version": "v1"
}
] | 2010-10-26 | [
[
"Isimori",
"Hajime",
""
]
] | We introduce new techniques that can preserve unitarity of the system including ghost particles. Negative norms of the particles can be involved in zero-norm states by constraints of the physical space. These are useful to apply the higher-derivative propagator for quantum gravity to suppress divergences of vacuum energy and graviton mass correction. The quantum effects are mainly depending on the ghost mass scale. As the scale can be chosen in any order, the observed cosmological constant is realized. Further, applying ghost partners for the standard model particles, quantum gravity with matter fields becomes renormalizable with power counting arguments. |
1809.02663 | David Delphenich | D. H. Delphenich | Singular teleparallelism | 19 pages, 6 figures | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the geometry of parallelizable manifolds can be extended to
non-parallelizable ones by extending the connection that a global frame field
would define on a parallelizable manifold to a connection that a singular frame
field would define on a non-parallelizable one. The resulting connection would
typically have non-vanishing curvature in the neighborhood of the singular
points of the frame field. The example of a 2-sphere is discussed as a
motivating example and later extended to more general suspensions of
parallelizable manifolds.
| [
{
"created": "Fri, 7 Sep 2018 20:26:00 GMT",
"version": "v1"
}
] | 2018-09-11 | [
[
"Delphenich",
"D. H.",
""
]
] | It is shown that the geometry of parallelizable manifolds can be extended to non-parallelizable ones by extending the connection that a global frame field would define on a parallelizable manifold to a connection that a singular frame field would define on a non-parallelizable one. The resulting connection would typically have non-vanishing curvature in the neighborhood of the singular points of the frame field. The example of a 2-sphere is discussed as a motivating example and later extended to more general suspensions of parallelizable manifolds. |
1410.8503 | Ryan Lynch | Ryan Lynch, Salvatore Vitale, Lisa Barsotti, Matthew Evans, Sheila
Dwyer | Effect of squeezing on parameter estimation of gravitational waves
emitted by compact binary systems | null | Physical Review D 91, 044032 (2015) | 10.1103/PhysRevD.91.044032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LIGO gravitational wave (GW) detectors will begin collecting data in
2015, with Virgo following shortly after. The use of squeezing has been
proposed as a way to reduce the quantum noise without increasing the laser
power, and has been successfully tested at one of the LIGO sites and at GEO in
Germany. When used in Advanced LIGO without a filter cavity, the squeezer
improves the performances of detectors above about 100 Hz, at the cost of a
higher noise floor in the low frequency regime. Frequency-dependent squeezing,
on the other hand, will lower the noise floor throughout the entire band.
Squeezing technology will have a twofold impact: it will change the number of
expected detections and it will impact the quality of parameter estimation for
the detected signals. In this work we consider three different GW detector
networks, each utilizing a different type of squeezer, all corresponding to
plausible implementations. Using LALInference, a powerful Monte Carlo parameter
estimation algorithm, we study how each of these networks estimates the
parameters of GW signals emitted by compact binary systems, and compare the
results with a baseline advanced LIGO-Virgo network. We find that, even in its
simplest implementation, squeezing has a large positive impact: the sky error
area of detected signals will shrink by about 30% on average, increasing the
chances of finding an electromagnetic counterpart to the GW detection.
Similarly, we find that the measurability of tidal deformability parameters for
neutron stars in binaries increases by about 30%, which could aid in
determining the equation of state of neutron stars. The degradation in the
measurement of the chirp mass, as a result of the higher low-frequency noise,
is shown to be negligible when compared to systematic errors.
| [
{
"created": "Thu, 30 Oct 2014 19:24:38 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Nov 2014 22:12:29 GMT",
"version": "v2"
}
] | 2015-02-24 | [
[
"Lynch",
"Ryan",
""
],
[
"Vitale",
"Salvatore",
""
],
[
"Barsotti",
"Lisa",
""
],
[
"Evans",
"Matthew",
""
],
[
"Dwyer",
"Sheila",
""
]
] | The LIGO gravitational wave (GW) detectors will begin collecting data in 2015, with Virgo following shortly after. The use of squeezing has been proposed as a way to reduce the quantum noise without increasing the laser power, and has been successfully tested at one of the LIGO sites and at GEO in Germany. When used in Advanced LIGO without a filter cavity, the squeezer improves the performances of detectors above about 100 Hz, at the cost of a higher noise floor in the low frequency regime. Frequency-dependent squeezing, on the other hand, will lower the noise floor throughout the entire band. Squeezing technology will have a twofold impact: it will change the number of expected detections and it will impact the quality of parameter estimation for the detected signals. In this work we consider three different GW detector networks, each utilizing a different type of squeezer, all corresponding to plausible implementations. Using LALInference, a powerful Monte Carlo parameter estimation algorithm, we study how each of these networks estimates the parameters of GW signals emitted by compact binary systems, and compare the results with a baseline advanced LIGO-Virgo network. We find that, even in its simplest implementation, squeezing has a large positive impact: the sky error area of detected signals will shrink by about 30% on average, increasing the chances of finding an electromagnetic counterpart to the GW detection. Similarly, we find that the measurability of tidal deformability parameters for neutron stars in binaries increases by about 30%, which could aid in determining the equation of state of neutron stars. The degradation in the measurement of the chirp mass, as a result of the higher low-frequency noise, is shown to be negligible when compared to systematic errors. |
0906.2557 | Guillermo A. Gonzalez | Antonio C. Guti\'errez-Pi\~neres, Guillermo A. Gonz\'alez and Viviana
M. Vi\~na-Cervantes | A family of relativistic charged thin disks with an inner edge | 11 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new family of exact solutions of the Einstein-Maxwell equations for static
axially symmetric spacetimes is presented. The metric functions of the
solutions are explicitely computed and are simply written in terms of the
oblate spheroidal coordinates. The solutions, obtained by applying the Ernst
method of complex potentials, describe an infinite family of static charged
dust disks with an inner edge. The energy density, pressure and charge density
of all the disks of the family are everywhere well behaved, in such a way that
the energy-momentum tensor fully agrees with all the energy conditions.
| [
{
"created": "Sun, 14 Jun 2009 16:24:05 GMT",
"version": "v1"
}
] | 2009-06-16 | [
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"González",
"Guillermo A.",
""
],
[
"Viña-Cervantes",
"Viviana M.",
""
]
] | A new family of exact solutions of the Einstein-Maxwell equations for static axially symmetric spacetimes is presented. The metric functions of the solutions are explicitely computed and are simply written in terms of the oblate spheroidal coordinates. The solutions, obtained by applying the Ernst method of complex potentials, describe an infinite family of static charged dust disks with an inner edge. The energy density, pressure and charge density of all the disks of the family are everywhere well behaved, in such a way that the energy-momentum tensor fully agrees with all the energy conditions. |
2405.10574 | Samuel Shuman | Samuel Shuman | Partial Derivatives on Causal Sets | 8 pages, 9 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We will discuss two approaches to estimating partial derivatives and the
metric components; one utilizing past work describing a causal set $\Box$
operator, and one using a construction from linear algebra called the
Moore-Penrose inverse. After running numerical tests on a causal diamond in
$\mathbb{M}^2$, we find that the approach using the Moore-Penrose inverse is
significantly more accurate. Despite the large variances in the method using
the $\Box$ operator, there is reason to believe both approaches should become
more accurate at higher densities.
| [
{
"created": "Fri, 17 May 2024 06:57:42 GMT",
"version": "v1"
}
] | 2024-05-20 | [
[
"Shuman",
"Samuel",
""
]
] | We will discuss two approaches to estimating partial derivatives and the metric components; one utilizing past work describing a causal set $\Box$ operator, and one using a construction from linear algebra called the Moore-Penrose inverse. After running numerical tests on a causal diamond in $\mathbb{M}^2$, we find that the approach using the Moore-Penrose inverse is significantly more accurate. Despite the large variances in the method using the $\Box$ operator, there is reason to believe both approaches should become more accurate at higher densities. |
1008.0171 | Vincenzo Vitagliano | Vincenzo Vitagliano, Thomas P. Sotiriou, Stefano Liberati | The dynamics of metric-affine gravity | 26 pages. v2: some footnotes, references and minor changes added to
match the published version. v3: some equations corrected to account for a
term that had been missed, results unaffected | Annals Phys.326:1259-1273,2011 | 10.1016/j.aop.2011.02.008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Metric-affine theories of gravity provide an interesting alternative to
General Relativity: in such an approach, the metric and the affine (not
necessarily symmetric) connection are independent quantities. Furthermore, the
action should include covariant derivatives of the matter fields, with the
covariant derivative naturally defined using the independent connection. As a
result, in metric-affine theories a direct coupling involving matter and
connection is also present. The role and the dynamics of the connection in such
theories is explored. We employ power counting in order to construct the action
and search for the minimal requirements it should satisfy for the connection to
be dynamical. We find that for the most general action containing lower order
invariants of the curvature and the torsion the independent connection does not
carry any dynamics. It actually reduces to the role of an auxiliary field and
can be completely eliminated algebraically in favour of the metric and the
matter field, introducing extra interactions with respect to general
relativity. However, we also show that including higher order terms in the
action radically changes this picture and excites new degrees of freedom in the
connection, making it (or parts of it) dynamical. Constructing actions that
constitute exceptions to this rule requires significant fine tuned and/or extra
a priori constraints on the connection. We also consider f(R) actions as a
particular example in order to show that they constitute a distinct class of
metric-affine theories with special properties, and as such they cannot be used
as representative toy theories to study the properties of metric-affine
gravity.
| [
{
"created": "Sun, 1 Aug 2010 13:07:57 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2011 12:32:50 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Nov 2012 14:32:16 GMT",
"version": "v3"
}
] | 2012-11-08 | [
[
"Vitagliano",
"Vincenzo",
""
],
[
"Sotiriou",
"Thomas P.",
""
],
[
"Liberati",
"Stefano",
""
]
] | Metric-affine theories of gravity provide an interesting alternative to General Relativity: in such an approach, the metric and the affine (not necessarily symmetric) connection are independent quantities. Furthermore, the action should include covariant derivatives of the matter fields, with the covariant derivative naturally defined using the independent connection. As a result, in metric-affine theories a direct coupling involving matter and connection is also present. The role and the dynamics of the connection in such theories is explored. We employ power counting in order to construct the action and search for the minimal requirements it should satisfy for the connection to be dynamical. We find that for the most general action containing lower order invariants of the curvature and the torsion the independent connection does not carry any dynamics. It actually reduces to the role of an auxiliary field and can be completely eliminated algebraically in favour of the metric and the matter field, introducing extra interactions with respect to general relativity. However, we also show that including higher order terms in the action radically changes this picture and excites new degrees of freedom in the connection, making it (or parts of it) dynamical. Constructing actions that constitute exceptions to this rule requires significant fine tuned and/or extra a priori constraints on the connection. We also consider f(R) actions as a particular example in order to show that they constitute a distinct class of metric-affine theories with special properties, and as such they cannot be used as representative toy theories to study the properties of metric-affine gravity. |
1611.06902 | Arshdeep Singh Bhatia | Arshdeep Singh Bhatia and Sourav Sur | Phase Plane Analysis of Metric-Scalar Torsion Model for Interacting Dark
Energy | 21 pages, 14 figures, 4 tables | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the phase space dynamics of the non-minimally coupled
Metric-Scalar-Torsion model in both Jordan and Einstein frames. We specifically
check for the existence of critical points which yield stable solutions
representing the current state of accelerated expansion of the universe fuelled
by the Dark Energy. It is found that such solutions do indeed exist, subject to
constraints on the free model parameter. In fact the evolution of the universe
at these stable critical points exactly matches the evolution given by the
cosmological solutions we found analytically in our previous work on the
subject.
| [
{
"created": "Mon, 21 Nov 2016 17:02:29 GMT",
"version": "v1"
}
] | 2016-11-22 | [
[
"Bhatia",
"Arshdeep Singh",
""
],
[
"Sur",
"Sourav",
""
]
] | We study the phase space dynamics of the non-minimally coupled Metric-Scalar-Torsion model in both Jordan and Einstein frames. We specifically check for the existence of critical points which yield stable solutions representing the current state of accelerated expansion of the universe fuelled by the Dark Energy. It is found that such solutions do indeed exist, subject to constraints on the free model parameter. In fact the evolution of the universe at these stable critical points exactly matches the evolution given by the cosmological solutions we found analytically in our previous work on the subject. |
1109.2189 | Ali Shojai | Fatimah Shojai and Ali Shojai | Non-minimal Quintessence: Dynamics and coincidence problem | To appear in Pramana Journal of Physics, 2011 | null | 10.1007/s12043-011-0146-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Brans--Dicke scalar--tensor theory provides a conformally coupling of the
scalar field with gravity in Einstein's frame. This model is equivalent to an
interacting quintessence in which dark matter is coupled to dark energy. This
provides a natural mechanism to alleviate the coincidence problem. We
investigate the dynamics of this model and show that it leads to comparable
dark energy and dark matter densities today.
| [
{
"created": "Sat, 10 Sep 2011 03:41:38 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Shojai",
"Fatimah",
""
],
[
"Shojai",
"Ali",
""
]
] | Brans--Dicke scalar--tensor theory provides a conformally coupling of the scalar field with gravity in Einstein's frame. This model is equivalent to an interacting quintessence in which dark matter is coupled to dark energy. This provides a natural mechanism to alleviate the coincidence problem. We investigate the dynamics of this model and show that it leads to comparable dark energy and dark matter densities today. |
2406.10482 | Susobhan Mandal | Susobhan Mandal | Ward identities under the frame transformations in curved spacetime | 14 pages, Accepted in Communications in Theoretical Physics | null | 10.1088/1572-9494/ad582b | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor theories of gravity are considered to be competitors to
Einstein's theory of general relativity for the description of classical
gravity, as they are used to build feasible models for cosmic inflation. These
theories can be formulated both in the Jordan and Einstein frame, which are
related by a Weyl transformation with a field transformation, known together as
a frame transformation. These theories formulated in the above two frames are
often considered to be equivalent from the point of view of classical theory.
However, this is no longer true from the quantum field theoretical perspective.
In the present article, we show that the Ward identities derived in the above
two frames are not connected through the frame transformation. This shows that
the quantum field theories formulated in these two frames are not equivalent to
each other. Moreover, this inequivalence is also shown by comparing the
effective actions derived in these two frames.
| [
{
"created": "Sat, 15 Jun 2024 03:23:49 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Mandal",
"Susobhan",
""
]
] | Scalar-tensor theories of gravity are considered to be competitors to Einstein's theory of general relativity for the description of classical gravity, as they are used to build feasible models for cosmic inflation. These theories can be formulated both in the Jordan and Einstein frame, which are related by a Weyl transformation with a field transformation, known together as a frame transformation. These theories formulated in the above two frames are often considered to be equivalent from the point of view of classical theory. However, this is no longer true from the quantum field theoretical perspective. In the present article, we show that the Ward identities derived in the above two frames are not connected through the frame transformation. This shows that the quantum field theories formulated in these two frames are not equivalent to each other. Moreover, this inequivalence is also shown by comparing the effective actions derived in these two frames. |
2403.06819 | Orlando Luongo | Rocco D'Agostino, Orlando Luongo, Stefano Mancini | Geometric and topological corrections to Schwarzschild black hole | 9 pages, 4 figures, minor changes, typos corrected, physical results
unaltered | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we compute departures in the black hole thermodynamics induced
by either geometric or topological corrections to general relativity.
Specifically, we analyze the spherically symmetric spacetime solutions of two
modified gravity scenarios with Lagrangians $\mathcal{L}\sim R^{1+\epsilon}$
and $\mathcal{L}\sim R+\epsilon\, \mathcal{G}^2$, where $\mathcal{G}$ is the
Euler density in four dimensions, while $ 0<\epsilon\ll 1$ measures the
perturbation around the Hilbert-Einstein action. Accordingly, we find the
expressions of the Bekenstein-Hawking entropy by the Penrose formula, and the
black hole temperature and horizon of the obtained solutions. We then
investigate the heat capacities in terms of the free parameters of the theories
under study. In doing so, we show that healing the problem of negative heat
capacities can be possible under particular choices of the free constants,
albeit with limitations on the masses allowed for the black hole solutions.
| [
{
"created": "Mon, 11 Mar 2024 15:38:11 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Mar 2024 11:49:44 GMT",
"version": "v2"
}
] | 2024-03-18 | [
[
"D'Agostino",
"Rocco",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Mancini",
"Stefano",
""
]
] | In this paper, we compute departures in the black hole thermodynamics induced by either geometric or topological corrections to general relativity. Specifically, we analyze the spherically symmetric spacetime solutions of two modified gravity scenarios with Lagrangians $\mathcal{L}\sim R^{1+\epsilon}$ and $\mathcal{L}\sim R+\epsilon\, \mathcal{G}^2$, where $\mathcal{G}$ is the Euler density in four dimensions, while $ 0<\epsilon\ll 1$ measures the perturbation around the Hilbert-Einstein action. Accordingly, we find the expressions of the Bekenstein-Hawking entropy by the Penrose formula, and the black hole temperature and horizon of the obtained solutions. We then investigate the heat capacities in terms of the free parameters of the theories under study. In doing so, we show that healing the problem of negative heat capacities can be possible under particular choices of the free constants, albeit with limitations on the masses allowed for the black hole solutions. |
gr-qc/0405038 | Yihuan Wei | Yi-Huan Wei, Yu Tian | SO(1,1) dark energy model and the universe transition | 12 pages. submitted to CQG | Class.Quant.Grav. 21 (2004) 5347-5353 | 10.1088/0264-9381/21/23/004 | null | gr-qc | null | We suggest a scalar model of dark energy with the SO(1,1) symmetry. The model
may be reformulated in terms of a real scalar field $\Phi$ and the scale factor
$a$ so that the Lagrangian may be decomposed as that of the real quintessence
model plus the negative coupling energy term of $\Phi$ to $a$. The existence of
the coupling term $L^c$ leads to a wider range of $w_{\Phi}$ and overcomes the
problem of negative kinetic energy in the phantom universe model. We propose a
power-law expansion model of univese with time-dependent power, which can
describe the phantom universe and the universe transition from ordinary
acceleration to super acceleration.
| [
{
"created": "Fri, 7 May 2004 08:57:56 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jul 2004 11:24:34 GMT",
"version": "v2"
},
{
"created": "Sat, 18 Sep 2004 13:14:53 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Wei",
"Yi-Huan",
""
],
[
"Tian",
"Yu",
""
]
] | We suggest a scalar model of dark energy with the SO(1,1) symmetry. The model may be reformulated in terms of a real scalar field $\Phi$ and the scale factor $a$ so that the Lagrangian may be decomposed as that of the real quintessence model plus the negative coupling energy term of $\Phi$ to $a$. The existence of the coupling term $L^c$ leads to a wider range of $w_{\Phi}$ and overcomes the problem of negative kinetic energy in the phantom universe model. We propose a power-law expansion model of univese with time-dependent power, which can describe the phantom universe and the universe transition from ordinary acceleration to super acceleration. |
2005.12306 | Shi Pi | Shi Pi and Misao Sasaki | Gravitational Waves Induced by Scalar Perturbations with a Lognormal
Peak | 15 pages, 3 figures. Some figures redrawn. References added and
reorganized. Accepted for JCAP | null | 10.1088/1475-7516/2020/09/037 | YITP-20-75, IPMU20-0054 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stochastic gravitational wave (GW) background induced by the
primordial scalar perturbation with the spectrum having a lognormal peak of
width $\Delta$ at $k=k_*$. We derive an analytical formula for the GW spectrum
$\Omega_\text{GW}$ for both narrow ($\Delta\ll1$) and broad ($\Delta\gtrsim1$)
peaks. In the narrow-peak case, the spectrum has a double peak feature with the
sharper peak at $k= 2k_*/\sqrt{3}$. On the infrared (IR) side of the spectrum,
we find power-law behavior with a break at $k=k_b$ in the power-law index where
it chages from $k^3$ on the far IR side to $k^2$ on the near IR side. We find
the ratio of the break frequency to the peak frequency is determined by
$\Delta$ as $f_b/f_p\approx\sqrt{3}\Delta$, where $f_b$ and $f_p$ are the break
and peak frequencies, respectively. In the broad-peak case, we find the GW
spectrum also has a lognormal peak at $k=k_*$ but with a smaller width of
$\Delta/\sqrt2$. Using these derived analytic formulae, we also present
expressions for the maximum values of $\Omega_\text{GW}$ for both narrow and
broad cases. Our results will provide a useful tool in searching for the
induced GW signals in the coming decades.
| [
{
"created": "Mon, 25 May 2020 18:00:30 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Aug 2020 15:14:44 GMT",
"version": "v2"
}
] | 2020-09-30 | [
[
"Pi",
"Shi",
""
],
[
"Sasaki",
"Misao",
""
]
] | We study the stochastic gravitational wave (GW) background induced by the primordial scalar perturbation with the spectrum having a lognormal peak of width $\Delta$ at $k=k_*$. We derive an analytical formula for the GW spectrum $\Omega_\text{GW}$ for both narrow ($\Delta\ll1$) and broad ($\Delta\gtrsim1$) peaks. In the narrow-peak case, the spectrum has a double peak feature with the sharper peak at $k= 2k_*/\sqrt{3}$. On the infrared (IR) side of the spectrum, we find power-law behavior with a break at $k=k_b$ in the power-law index where it chages from $k^3$ on the far IR side to $k^2$ on the near IR side. We find the ratio of the break frequency to the peak frequency is determined by $\Delta$ as $f_b/f_p\approx\sqrt{3}\Delta$, where $f_b$ and $f_p$ are the break and peak frequencies, respectively. In the broad-peak case, we find the GW spectrum also has a lognormal peak at $k=k_*$ but with a smaller width of $\Delta/\sqrt2$. Using these derived analytic formulae, we also present expressions for the maximum values of $\Omega_\text{GW}$ for both narrow and broad cases. Our results will provide a useful tool in searching for the induced GW signals in the coming decades. |
2104.12633 | Alesandro Santos | A. F. Santos, S. C. Ulhoa, T. F. Furtado and Faqir C. Khanna | On the Temperature of Gravitation in the de Sitter Space-Time | 15 pages, 1 figure, accepted for publication in EPJC | null | 10.1140/epjc/s10052-021-09189-3 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The temperature associated with gravitation as presented in the Unruh effect
and Hawking temperature serves to link different areas of physics, such as
gravity, statistical mechanics, and quantum physics. In this paper,
teleparallel gravity is considered to study temperature effects on the de
Sitter space-time. The effects of temperature are introduced using the Thermo
Field Dynamics (TFD) formalism. The gravitational Stefan-Boltzmann law is
obtained. Then the temperature of gravitation in the de Sitter space-time is
calculated. Here an Unruh-type effect is discussed. This effect relates the
temperature and the acceleration of a particle in the de Sitter space-time. The
gravitational Casimir effect is calculated. The result shows that there is a
transition between an attractive and a repulsive Casimir effect.
| [
{
"created": "Mon, 26 Apr 2021 14:59:28 GMT",
"version": "v1"
}
] | 2021-05-19 | [
[
"Santos",
"A. F.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"Furtado",
"T. F.",
""
],
[
"Khanna",
"Faqir C.",
""
]
] | The temperature associated with gravitation as presented in the Unruh effect and Hawking temperature serves to link different areas of physics, such as gravity, statistical mechanics, and quantum physics. In this paper, teleparallel gravity is considered to study temperature effects on the de Sitter space-time. The effects of temperature are introduced using the Thermo Field Dynamics (TFD) formalism. The gravitational Stefan-Boltzmann law is obtained. Then the temperature of gravitation in the de Sitter space-time is calculated. Here an Unruh-type effect is discussed. This effect relates the temperature and the acceleration of a particle in the de Sitter space-time. The gravitational Casimir effect is calculated. The result shows that there is a transition between an attractive and a repulsive Casimir effect. |
2204.00119 | R. R. Cuzinatto | Rodrigo R. Cuzinatto, Rajendra P. Gupta, and Pedro J. Pompeia | Dynamical analysis of the covarying coupling constants in scalar-tensor
gravity | 15 pages, 4 figures. v2: 19 pages, 6 figures; stability analysis
expanded and generalized; discussion improved. v3: 27 pages, 6 figures;
appendix added; abstract edited due to arXiv's policy; content matches the
published version | Symmetry 15, 709 (2023) | 10.3390/sym15030709 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A scalar-tensor theory of gravity is considered wherein the gravitational
coupling $G$ and the speed of light $c$ are admitted as space-time functions
and combine to form the definition of the scalar field $\phi$. The varying $c$
participates in the definition of the variation of the matter part of the
action; it is related to the effective stress-energy tensor which is a result
of the requirement of symmetry under general coordinate transformations. The
effect of the cosmological coupling $\Lambda$ is accommodated within a possible
behaviour of $\phi$. We analyze the dynamics of $\phi$ in the phase space,
thereby showing the existence of an attractor point for reasonable hypotheses
on the potential $V(\phi)$ and no particular assumption on the Hubble function.
The phase space analysis is performed both with the linear stability theory and
via the more general Lyapunov's method. Either method lead to the conclusion
that the condition $\dot{G}/G=\sigma\left(\dot{c}/c\right)$ where $\sigma=3$
must hold for the rest of cosmic evolution after the system gets to the
globally asymptotically stable fixed point and the dynamics of $\phi$ ceases.
This result provides a physical foundation for the phenomenological model
admitting $\left(G/G_{0}\right)=\left(c/c_{0}\right)^{3}$ used recently to
interpret cosmological and astrophysical data. The thus co-varying couplings
$G$ and $c$ impact the cosmic evolution after the dynamical system settles to
equilibrium. This impact is investigated by constructing the generalized
continuity equation in our scalar-tensor model and considering two possible
regimes for the varying speed of light -- decreasing $c(a)$ and increasing
$c(a)$ -- while solving our modified Friedmann equations. The solutions to the
latter equations make room for radiation- and matter-dominated eras that
progress to a dark-energy-type of accelerated expansion.
| [
{
"created": "Thu, 31 Mar 2022 22:00:22 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Oct 2022 22:10:37 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Apr 2023 22:21:25 GMT",
"version": "v3"
}
] | 2023-04-05 | [
[
"Cuzinatto",
"Rodrigo R.",
""
],
[
"Gupta",
"Rajendra P.",
""
],
[
"Pompeia",
"Pedro J.",
""
]
] | A scalar-tensor theory of gravity is considered wherein the gravitational coupling $G$ and the speed of light $c$ are admitted as space-time functions and combine to form the definition of the scalar field $\phi$. The varying $c$ participates in the definition of the variation of the matter part of the action; it is related to the effective stress-energy tensor which is a result of the requirement of symmetry under general coordinate transformations. The effect of the cosmological coupling $\Lambda$ is accommodated within a possible behaviour of $\phi$. We analyze the dynamics of $\phi$ in the phase space, thereby showing the existence of an attractor point for reasonable hypotheses on the potential $V(\phi)$ and no particular assumption on the Hubble function. The phase space analysis is performed both with the linear stability theory and via the more general Lyapunov's method. Either method lead to the conclusion that the condition $\dot{G}/G=\sigma\left(\dot{c}/c\right)$ where $\sigma=3$ must hold for the rest of cosmic evolution after the system gets to the globally asymptotically stable fixed point and the dynamics of $\phi$ ceases. This result provides a physical foundation for the phenomenological model admitting $\left(G/G_{0}\right)=\left(c/c_{0}\right)^{3}$ used recently to interpret cosmological and astrophysical data. The thus co-varying couplings $G$ and $c$ impact the cosmic evolution after the dynamical system settles to equilibrium. This impact is investigated by constructing the generalized continuity equation in our scalar-tensor model and considering two possible regimes for the varying speed of light -- decreasing $c(a)$ and increasing $c(a)$ -- while solving our modified Friedmann equations. The solutions to the latter equations make room for radiation- and matter-dominated eras that progress to a dark-energy-type of accelerated expansion. |
2310.09839 | Keisuke Nakashi | Keisuke Nakashi, Masashi Kimura, Hayato Motohashi, Kazufumi Takahashi | Black hole ringdown from physically sensible initial value problem in
higher-order scalar-tensor theories | 36 pages, 11 figures | Phys. Rev. D109, no.2, 024034 (2024) | 10.1103/PhysRevD.109.024034 | RUP-23-19, YITP-23-118 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study odd-parity perturbations about static and spherically symmetric
black hole solutions with a linearly time-dependent scalar field in
higher-order scalar-tensor theories. In particular, we consider stealth
Schwarzschild and stealth Schwarzschild-de Sitter solutions, where the
deviation from the general relativity case is controlled by a single parameter.
We find that complex frequencies of quasinormal modes (QNMs) are given by a
simple scaling of those in general relativity. We also show that there is a
degeneracy between the parameter characterizing the modification from general
relativity and the black hole mass. We then consider a physically sensible
initial value problem by taking into account the fact that the effective metric
for the odd-parity perturbations is in general different from the background
metric. We confirm that damped oscillations appearing at late times are indeed
dominated by the QNMs. Our analysis includes the case where the perturbations
are superluminal, and we demonstrate in this case that the perturbations can
escape from the region inside the horizon for the background metric.
| [
{
"created": "Sun, 15 Oct 2023 13:59:11 GMT",
"version": "v1"
}
] | 2024-03-01 | [
[
"Nakashi",
"Keisuke",
""
],
[
"Kimura",
"Masashi",
""
],
[
"Motohashi",
"Hayato",
""
],
[
"Takahashi",
"Kazufumi",
""
]
] | We study odd-parity perturbations about static and spherically symmetric black hole solutions with a linearly time-dependent scalar field in higher-order scalar-tensor theories. In particular, we consider stealth Schwarzschild and stealth Schwarzschild-de Sitter solutions, where the deviation from the general relativity case is controlled by a single parameter. We find that complex frequencies of quasinormal modes (QNMs) are given by a simple scaling of those in general relativity. We also show that there is a degeneracy between the parameter characterizing the modification from general relativity and the black hole mass. We then consider a physically sensible initial value problem by taking into account the fact that the effective metric for the odd-parity perturbations is in general different from the background metric. We confirm that damped oscillations appearing at late times are indeed dominated by the QNMs. Our analysis includes the case where the perturbations are superluminal, and we demonstrate in this case that the perturbations can escape from the region inside the horizon for the background metric. |
2103.15437 | Diego Rubiera-Garcia | David Benisty, Gonzalo J. Olmo, Diego Rubiera-Garcia | Singularity-free and cosmologically viable Born-Infeld gravity with
scalar matter | 26 pages, 15 figures. v2: bounds on EiBI parameter significantly
improved. Version accepted for publication | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The early Cosmology driven by a single scalar field, both massless and
massive, in the context of Eddington-inspired Born-Infeld gravity, is explored.
We show the existence of nonsingular solutions of bouncing and loitering type
(depending on the sign of the gravitational theory's parameter, $\epsilon$)
replacing the Big Bang singularity, and discuss their properties. In addition,
in the massive case we find some new features of the cosmological evolution
depending on the value of the mass parameter, including asymmetries in the
expansion/contraction phases, or a continuous transition between a contracting
phase to an expanding one via an intermediate loitering phase. We also provide
a combined analysis of cosmic chronometers, standard candles, BAO, and CMB data
to constrain the model, finding that for roughly $\vert \epsilon \vert \lesssim
5\cdot 10^{-8} \text{ m}^2$ the model is compatible with the latest
observations while successfully removing the Big Bang singularity. This bound
is several orders of magnitude stronger than the most stringent constraints
currently available in the literature
| [
{
"created": "Mon, 29 Mar 2021 09:08:43 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Nov 2021 08:33:45 GMT",
"version": "v2"
}
] | 2021-11-15 | [
[
"Benisty",
"David",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
]
] | The early Cosmology driven by a single scalar field, both massless and massive, in the context of Eddington-inspired Born-Infeld gravity, is explored. We show the existence of nonsingular solutions of bouncing and loitering type (depending on the sign of the gravitational theory's parameter, $\epsilon$) replacing the Big Bang singularity, and discuss their properties. In addition, in the massive case we find some new features of the cosmological evolution depending on the value of the mass parameter, including asymmetries in the expansion/contraction phases, or a continuous transition between a contracting phase to an expanding one via an intermediate loitering phase. We also provide a combined analysis of cosmic chronometers, standard candles, BAO, and CMB data to constrain the model, finding that for roughly $\vert \epsilon \vert \lesssim 5\cdot 10^{-8} \text{ m}^2$ the model is compatible with the latest observations while successfully removing the Big Bang singularity. This bound is several orders of magnitude stronger than the most stringent constraints currently available in the literature |
1809.02045 | Edward Anderson | Edward Anderson | Specific PDEs for Preserved Quantities in Geometry. I. Similarities and
Subgroups | 30 pages, including 6 figures. References updated, minor typos
removed, and notational changes | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide specific PDEs for preserved quantities $Q$ in Geometry, as well as
a bridge between this and specific PDEs for observables $O$ in Physics. We
furthermore prove versions of four other theorems either side of this bridge:
the below enumerated sentences. For the generic geometry - in the sense of it
possessing no generalized Killing vectors, i.e.\ continuous geometrical
automorphisms - the $P$ form a smooth space of free functions over said
geometry. If a geometry possesses the corresponding type of Killing vectors,
the $P$ must Lie-brackets commute with `sums-over-points of the automorphism
generators', $S$. The observables counterpart of this is that in the presence
of first-class constraints $F$, the $O$ must Poisson-brackets commute with
these. Then 1) defining $Q$, $O$ requires closed subalgebras of $S$, $F$. 2)
The $Q$, and the $O$, themselves form closed algebras. 3) The subalgebras of
$Q$, $O$ form bounded lattices dual to those of $S$, $F$ respectively. Both
$S$, $Q$ and $F$, $O$ commutations can moreover be reformulated as first-order
linear PDEs, treated free-characteristically. The secondmost generic case has
just one $S$ or $F$, and so just one PDE, which standardly reduces to an ODE
system. The more highly nongeneric case of multiple $S$ or $F$, however,
returns an over-determined PDE system. 4) We prove that nonetheless these are
always integrable. This is significant by being mostly-opposite to how the more
familiar generalized Killing equations themselves behave. We finally solve for
the preserved quantities of similarity geometry and its subgroups; companion
papers extend this program to affine, projective and conformal geometries.
| [
{
"created": "Thu, 6 Sep 2018 15:30:23 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Sep 2018 16:11:39 GMT",
"version": "v2"
}
] | 2018-09-25 | [
[
"Anderson",
"Edward",
""
]
] | We provide specific PDEs for preserved quantities $Q$ in Geometry, as well as a bridge between this and specific PDEs for observables $O$ in Physics. We furthermore prove versions of four other theorems either side of this bridge: the below enumerated sentences. For the generic geometry - in the sense of it possessing no generalized Killing vectors, i.e.\ continuous geometrical automorphisms - the $P$ form a smooth space of free functions over said geometry. If a geometry possesses the corresponding type of Killing vectors, the $P$ must Lie-brackets commute with `sums-over-points of the automorphism generators', $S$. The observables counterpart of this is that in the presence of first-class constraints $F$, the $O$ must Poisson-brackets commute with these. Then 1) defining $Q$, $O$ requires closed subalgebras of $S$, $F$. 2) The $Q$, and the $O$, themselves form closed algebras. 3) The subalgebras of $Q$, $O$ form bounded lattices dual to those of $S$, $F$ respectively. Both $S$, $Q$ and $F$, $O$ commutations can moreover be reformulated as first-order linear PDEs, treated free-characteristically. The secondmost generic case has just one $S$ or $F$, and so just one PDE, which standardly reduces to an ODE system. The more highly nongeneric case of multiple $S$ or $F$, however, returns an over-determined PDE system. 4) We prove that nonetheless these are always integrable. This is significant by being mostly-opposite to how the more familiar generalized Killing equations themselves behave. We finally solve for the preserved quantities of similarity geometry and its subgroups; companion papers extend this program to affine, projective and conformal geometries. |
1311.5798 | Andrew Steane | Andrew M. Steane | The non-existence of the self-accelerating dipole, and related questions | 10 pages, 4 figures; improved discussion of pressure; added remarks
on simultaneity and Rindler frame | Phys. Rev. D 89, 125006 (2014) | 10.1103/PhysRevD.89.125006 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the self-force of a constantly accelerating electric dipole,
showing, in particular, that classical electromagnetism does not predict that
an electric dipole could self-accelerate, nor could it levitate in a
gravitational field. We also resolve a paradox concerning the inertial mass of
a longitudinally accelerating dipole, showing that the combined system of
dipole plus field can be assigned a well-defined energy-momentum four-vector,
so that the Principle of Relativity is satisfied. We then present some general
features of electromagnetic phenomena in a gravitational field described by the
Rindler metric, showing in particular that an observer fixed in a gravitational
field described by the Rindler metric will find any charged object supported in
the gravitational field to possess an electromagnetic self-force equal to that
observed by an inertial observer relative to which the body undergoes rigid
hyperbolic motion. It follows that the Principle of Equivalence is satisfied by
these systems.
| [
{
"created": "Fri, 22 Nov 2013 16:29:02 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Dec 2013 17:37:43 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Mar 2014 13:40:01 GMT",
"version": "v3"
}
] | 2015-10-13 | [
[
"Steane",
"Andrew M.",
""
]
] | We calculate the self-force of a constantly accelerating electric dipole, showing, in particular, that classical electromagnetism does not predict that an electric dipole could self-accelerate, nor could it levitate in a gravitational field. We also resolve a paradox concerning the inertial mass of a longitudinally accelerating dipole, showing that the combined system of dipole plus field can be assigned a well-defined energy-momentum four-vector, so that the Principle of Relativity is satisfied. We then present some general features of electromagnetic phenomena in a gravitational field described by the Rindler metric, showing in particular that an observer fixed in a gravitational field described by the Rindler metric will find any charged object supported in the gravitational field to possess an electromagnetic self-force equal to that observed by an inertial observer relative to which the body undergoes rigid hyperbolic motion. It follows that the Principle of Equivalence is satisfied by these systems. |
2310.15180 | Saumya Ghosh | Saumya Ghosh, Arnab Acharya, Sunandan Gangopadhyay and Prasanta K.
Panigrahi | Lorentzian path integral in Kantowski-Sachs anisotropic cosmology | 9 pages, 4 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Motivated by the recent development in quantum cosmology, we revisit the
anisotropic Kantowski-Sachs model in the light of a Lorentzian path integral
formalism. Studies so far have considered the Euclidean method where the choice
of the lapse integration contour is constrained by certain physical
considerations rather than mathematical justification. In this paper, we have
studied the Hartle-Hawking no-boundary proposal along with the use of
Picard-Lefschetz theory in performing the lapse integration. In an isotropic
limit, we show our results agree with the studies made in FLRW cosmology. We
also observe that in the large scale structure the no-boundary proposal tends
towards a conical singularity at the beginning of time. We have also performed
a massless scalar perturbation analysis with no back reaction. This reveals
that if there were any perturbation present at the beginning of the universe
then that would flare up at the final boundary.
| [
{
"created": "Thu, 19 Oct 2023 18:11:57 GMT",
"version": "v1"
}
] | 2023-10-25 | [
[
"Ghosh",
"Saumya",
""
],
[
"Acharya",
"Arnab",
""
],
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Panigrahi",
"Prasanta K.",
""
]
] | Motivated by the recent development in quantum cosmology, we revisit the anisotropic Kantowski-Sachs model in the light of a Lorentzian path integral formalism. Studies so far have considered the Euclidean method where the choice of the lapse integration contour is constrained by certain physical considerations rather than mathematical justification. In this paper, we have studied the Hartle-Hawking no-boundary proposal along with the use of Picard-Lefschetz theory in performing the lapse integration. In an isotropic limit, we show our results agree with the studies made in FLRW cosmology. We also observe that in the large scale structure the no-boundary proposal tends towards a conical singularity at the beginning of time. We have also performed a massless scalar perturbation analysis with no back reaction. This reveals that if there were any perturbation present at the beginning of the universe then that would flare up at the final boundary. |
1908.08739 | Albert Huber | Albert Huber | Null Foliations of Spacetime and the Geometry of Black Hole Horizons | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, a method for constructing null foliations of spacetime is
presented. This method is used to specify equivalence classes of null
generators, whose representatives can be associated lightlike co-normals that
are locally affine geodesic and thus locally orthogonal to embedded null
hypersurfaces of spacetime. The main benefit of the proposed procedure is the
fact that it is less geometrically restrictive than the traditional dual-null
approaches to general relativity, but nevertheless allows for the conclusion
that spacetimes can be foliated by suitable pairs of normalized null geodesic
vector fields. This is demonstrated by the example of different black hole
spacetimes, that is, by members of the Kerr-Newman family, according to which a
said foliation and an associated equivalence class of null generators are
explicitly constructed.
| [
{
"created": "Fri, 23 Aug 2019 09:48:39 GMT",
"version": "v1"
}
] | 2019-08-26 | [
[
"Huber",
"Albert",
""
]
] | In this work, a method for constructing null foliations of spacetime is presented. This method is used to specify equivalence classes of null generators, whose representatives can be associated lightlike co-normals that are locally affine geodesic and thus locally orthogonal to embedded null hypersurfaces of spacetime. The main benefit of the proposed procedure is the fact that it is less geometrically restrictive than the traditional dual-null approaches to general relativity, but nevertheless allows for the conclusion that spacetimes can be foliated by suitable pairs of normalized null geodesic vector fields. This is demonstrated by the example of different black hole spacetimes, that is, by members of the Kerr-Newman family, according to which a said foliation and an associated equivalence class of null generators are explicitly constructed. |
1703.10057 | Sunandan Gangopadhyay | Biplab Paik, Sunandan Gangopadhyay | Accretion onto a noncommutative inspired Schwarzschild black hole | 16 pages Latex, submitted in journal, comments are welcome | Int.J.Mod.Phys. A 33 (2018) 1850084 | 10.1142/S0217751X18500847 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the problem of ordinary baryonic matter
accretion onto the noncommutative geometry inspired Schwarzschild black hole.
The fundamental equations governing the spherically symmetric steady state
matter accretion are deduced. These equations are seen to be modified due to
the presence of noncommutativity. The matter accretion rate is computed and is
found to increase rapidly with the increase in strength of the noncommutative
parameter. The sonic radius reduces while the sound speed at the sonic point
increases with the increase in the strength of noncommutativity. The profile of
the thermal environment is finally investigated below the sonic radius and at
the event horizon and is found to be affected by noncommutativity.
| [
{
"created": "Tue, 28 Mar 2017 14:29:34 GMT",
"version": "v1"
}
] | 2018-05-18 | [
[
"Paik",
"Biplab",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | In this paper we investigate the problem of ordinary baryonic matter accretion onto the noncommutative geometry inspired Schwarzschild black hole. The fundamental equations governing the spherically symmetric steady state matter accretion are deduced. These equations are seen to be modified due to the presence of noncommutativity. The matter accretion rate is computed and is found to increase rapidly with the increase in strength of the noncommutative parameter. The sonic radius reduces while the sound speed at the sonic point increases with the increase in the strength of noncommutativity. The profile of the thermal environment is finally investigated below the sonic radius and at the event horizon and is found to be affected by noncommutativity. |
1512.04580 | Marek Szydlowski | Marek Szydlowski, Aleksander Stachowski, Andrzej Borowiec, Aneta
Wojnar | Do sewn singularities falsify the Palatini cosmology? | 26 pages, 15 figures, v3: change of title, more discussion on
singularities | Eur. Phys. J. C76, 567 (2016) | 10.1140/epjc/s10052-016-4426-9 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate further (cf. arXiv:1512.01199, JCAP01 (2016) 040) Starobinsky
cosmological model $R+\gamma R^2$ in the Palatini formalism with Chaplygin gas
and baryonic matter as a source. For this aim we use dynamical system theory.
The dynamics is reduced to the 2D sewn dynamical system of a Newtonian type (a
piecewise-smooth dynamical system). We classify all evolutional paths in the
model as well as trajectories in the phase space. We demonstrate the presence
of a degenerate freeze singularity (glued freeze type singularities) for the
positive $\gamma$. In this case it is a generic feature of early evolution of
the universe. We point out that a degenerate type III of singularity can be
considered as an endogenous model of inflation between the matter dominating
epoch and the dark energy phase. We also investigate cosmological models with
negative $\gamma$. It is demonstrated that $\gamma$ equal zero is a bifurcation
parameter and dynamics qualitatively changes in comparison to positive
$\gamma$. Instead of the big bang the sudden bounce singularity of a finite
scale factor appears and there is a generic class of bouncing solutions sewn
along the line $a=a_{\text{sing}}$. And we argue that the presence of sudden
singularities in an evolutional scenario of the Universe falsifies the negative
$\gamma$ in the Palatini cosmology. Only very small values of $\Omega_{\gamma}$
parameter are admissible if we requires that agreements physics with the
$\Lambda$CDM model. From the statistical analysis of astronomical observations,
we deduce that the case of negative values of $\Omega_\gamma$ can be rejected
even if it may fit better to the data.
| [
{
"created": "Thu, 10 Dec 2015 16:22:59 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2015 18:06:00 GMT",
"version": "v2"
},
{
"created": "Sun, 20 Mar 2016 13:17:05 GMT",
"version": "v3"
}
] | 2017-09-29 | [
[
"Szydlowski",
"Marek",
""
],
[
"Stachowski",
"Aleksander",
""
],
[
"Borowiec",
"Andrzej",
""
],
[
"Wojnar",
"Aneta",
""
]
] | We investigate further (cf. arXiv:1512.01199, JCAP01 (2016) 040) Starobinsky cosmological model $R+\gamma R^2$ in the Palatini formalism with Chaplygin gas and baryonic matter as a source. For this aim we use dynamical system theory. The dynamics is reduced to the 2D sewn dynamical system of a Newtonian type (a piecewise-smooth dynamical system). We classify all evolutional paths in the model as well as trajectories in the phase space. We demonstrate the presence of a degenerate freeze singularity (glued freeze type singularities) for the positive $\gamma$. In this case it is a generic feature of early evolution of the universe. We point out that a degenerate type III of singularity can be considered as an endogenous model of inflation between the matter dominating epoch and the dark energy phase. We also investigate cosmological models with negative $\gamma$. It is demonstrated that $\gamma$ equal zero is a bifurcation parameter and dynamics qualitatively changes in comparison to positive $\gamma$. Instead of the big bang the sudden bounce singularity of a finite scale factor appears and there is a generic class of bouncing solutions sewn along the line $a=a_{\text{sing}}$. And we argue that the presence of sudden singularities in an evolutional scenario of the Universe falsifies the negative $\gamma$ in the Palatini cosmology. Only very small values of $\Omega_{\gamma}$ parameter are admissible if we requires that agreements physics with the $\Lambda$CDM model. From the statistical analysis of astronomical observations, we deduce that the case of negative values of $\Omega_\gamma$ can be rejected even if it may fit better to the data. |
2107.14115 | Tuan Do | Duy H. Nguyen, Tuyen M. Pham, Tuan Q. Do | Anisotropic constant-roll inflation for the Dirac-Born-Infeld model | 14 pages, 14 figures. Matches the published version. All results are
not changed. Comments are welcome | Eur. Phys. J. C 81, 839 (2021) | 10.1140/epjc/s10052-021-09652-1 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study a non-canonical extension of a supergravity-motivated
model acting as a vivid counterexample to the cosmic no-hair conjecture due to
its unusual coupling between scalar and electromagnetic fields. In particular,
a canonical scalar field is replaced by the string-inspired Dirac-Born-Infeld
one in this extension. As a result, exact anisotropic inflationary solutions
for this Dirac-Born-Infeld model are figured out under a constant-roll
condition. Furthermore, numerical calculations are performed to verify that
these anisotropic constant-roll solutions are indeed attractive during their
inflationary phase.
| [
{
"created": "Thu, 29 Jul 2021 15:38:25 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Aug 2021 11:13:32 GMT",
"version": "v2"
},
{
"created": "Wed, 22 Sep 2021 09:31:50 GMT",
"version": "v3"
}
] | 2021-09-23 | [
[
"Nguyen",
"Duy H.",
""
],
[
"Pham",
"Tuyen M.",
""
],
[
"Do",
"Tuan Q.",
""
]
] | In this paper, we study a non-canonical extension of a supergravity-motivated model acting as a vivid counterexample to the cosmic no-hair conjecture due to its unusual coupling between scalar and electromagnetic fields. In particular, a canonical scalar field is replaced by the string-inspired Dirac-Born-Infeld one in this extension. As a result, exact anisotropic inflationary solutions for this Dirac-Born-Infeld model are figured out under a constant-roll condition. Furthermore, numerical calculations are performed to verify that these anisotropic constant-roll solutions are indeed attractive during their inflationary phase. |
1505.07080 | Roberto Ivan Cabrera Munguia Dr. | I. Cabrera-Munguia | Binary system of unequal counterrotating Kerr-Newman sources | 11 pages, 7 figures, 1 table, typos corrected | Phys. Rev. D 91: 044005 (2015) | 10.1103/PhysRevD.91.044005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Stationary axisymmetric binary systems of unequal counterrotating Kerr-Newman
sources with a massless strut in between are studied. By means of the choice of
a suitable parametrization, the axis conditions and the absence of individual
magnetic charges are fulfilled; thus, the entire metric reduces to a
6-parametric asymptotically flat exact solution. Later on, with the purpose to
describe interacting black holes, the analytic functional form of the horizon
half-length parameter $\sigma_{k}$ is obtained explicitly in terms of physical
Komar parameters: mass $M_{k}$, electric charge $Q_{k}$, angular momentum
$J_{k}$, and coordinate distance $R$, where the seven physical parameters
satisfy a simple algebraic relation. Finally, in the limit of extreme black
holes, the full metric is derived in a closed analytical form, and a study on
the absence or appearance of naked singularities off the axis is presented.
| [
{
"created": "Tue, 26 May 2015 19:07:21 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jun 2017 09:13:56 GMT",
"version": "v2"
}
] | 2017-07-03 | [
[
"Cabrera-Munguia",
"I.",
""
]
] | Stationary axisymmetric binary systems of unequal counterrotating Kerr-Newman sources with a massless strut in between are studied. By means of the choice of a suitable parametrization, the axis conditions and the absence of individual magnetic charges are fulfilled; thus, the entire metric reduces to a 6-parametric asymptotically flat exact solution. Later on, with the purpose to describe interacting black holes, the analytic functional form of the horizon half-length parameter $\sigma_{k}$ is obtained explicitly in terms of physical Komar parameters: mass $M_{k}$, electric charge $Q_{k}$, angular momentum $J_{k}$, and coordinate distance $R$, where the seven physical parameters satisfy a simple algebraic relation. Finally, in the limit of extreme black holes, the full metric is derived in a closed analytical form, and a study on the absence or appearance of naked singularities off the axis is presented. |
gr-qc/0111069 | Yuan-Zhong Zhang | J. Luo, Y.X. Nie, Y.Z. Zhang, Z.B. Zhou | Null Result for the Violation of Equivalence Principle with Free-Fall
Rotating Gyroscopes | REVTeX 3.0, 7 pages with 4 Postscript figures | Phys.Rev. D65 (2002) 042005 | 10.1103/PhysRevD.65.042005 | null | gr-qc | null | The differential acceleration between a rotating mechanical gyroscope and a
non-rotating one is directly measured by using a double free-fall
interferometer, and no apparent differential acceleration has been observed at
the relative level of 2x10{-6}. It means that the equivalence principle is
still valid for rotating extended bodies, i.e., the spin-gravity interaction
between the extended bodies has not been observed at this level. Also, to the
limit of our experimental sensitivity, there is no observed asymmetrical effect
or anti-gravity of the rotating gyroscopes as reported by hayasaka et al.
| [
{
"created": "Wed, 21 Nov 2001 04:43:38 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Luo",
"J.",
""
],
[
"Nie",
"Y. X.",
""
],
[
"Zhang",
"Y. Z.",
""
],
[
"Zhou",
"Z. B.",
""
]
] | The differential acceleration between a rotating mechanical gyroscope and a non-rotating one is directly measured by using a double free-fall interferometer, and no apparent differential acceleration has been observed at the relative level of 2x10{-6}. It means that the equivalence principle is still valid for rotating extended bodies, i.e., the spin-gravity interaction between the extended bodies has not been observed at this level. Also, to the limit of our experimental sensitivity, there is no observed asymmetrical effect or anti-gravity of the rotating gyroscopes as reported by hayasaka et al. |
2007.12686 | Christian Salas | Christian P. H. Salas | Proving the Relativistic Rotation Paradox | 5 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An apparent paradox in Einstein's Special Theory of Relativity, known as a
Thomas precession rotation in atomic physics, has been verified experimentally
in a number of ways. However, somewhat surprisingly, it has not yet been
demonstrated algebraically in a straightforward manner using
Lorentz-matrix-algebra. Authors in the past have resorted instead to computer
verifications, or to overly-complicated derivations, leaving undergraduate
students in particular with the impression that this is a mysterious and
mathematically inaccessible phenomenon. This is surprising because, as shown in
the present note, it is possible to use a basic property of orthogonal Lorentz
matrices and a judicious choice for the configuration of the relevant inertial
frames to give a very transparent algebraic proof. It is pedagogically useful
for physics students particularly at undergraduate level to explore this. It
not only clarifies the nature of the paradox at an accessible mathematical
level and sheds additional light on some mathematical properties of Lorentz
matrices and relatively-moving frames. It also illustrates the satisfaction
that a clear mathematical understanding of a physics problem can bring,
compared to uninspired computations or tortured derivations.
| [
{
"created": "Fri, 24 Jul 2020 05:49:45 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jul 2020 18:06:57 GMT",
"version": "v2"
}
] | 2020-07-30 | [
[
"Salas",
"Christian P. H.",
""
]
] | An apparent paradox in Einstein's Special Theory of Relativity, known as a Thomas precession rotation in atomic physics, has been verified experimentally in a number of ways. However, somewhat surprisingly, it has not yet been demonstrated algebraically in a straightforward manner using Lorentz-matrix-algebra. Authors in the past have resorted instead to computer verifications, or to overly-complicated derivations, leaving undergraduate students in particular with the impression that this is a mysterious and mathematically inaccessible phenomenon. This is surprising because, as shown in the present note, it is possible to use a basic property of orthogonal Lorentz matrices and a judicious choice for the configuration of the relevant inertial frames to give a very transparent algebraic proof. It is pedagogically useful for physics students particularly at undergraduate level to explore this. It not only clarifies the nature of the paradox at an accessible mathematical level and sheds additional light on some mathematical properties of Lorentz matrices and relatively-moving frames. It also illustrates the satisfaction that a clear mathematical understanding of a physics problem can bring, compared to uninspired computations or tortured derivations. |
1208.5869 | Francesco Pannarale | Francesco Pannarale | The Black Hole Remnant of Black Hole-Neutron Star Coalescing Binaries | 16 pages, 11 figures, 5 tables; matches published version | Phys. Rev. D 88, 104025 (2013) | 10.1103/PhysRevD.88.104025 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a model for determining the dimensionless spin parameter and mass
of the black hole remnant of black hole-neutron star mergers with parallel
orbital angular momentum and initial black hole spin. This approach is based on
the Buonanno, Kidder, and Lehner method for binary black holes, and it is
successfully tested against the results of numerical-relativity simulations:
the dimensionless spin parameter is predicted with absolute error $\lesssim
0.02$, whereas the relative error on the final mass is $\lesssim 2$%, its
distribution in the tests being pronouncedly peaked at $1$%. Our approach and
the fit to the torus remnant mass reported in Foucart (2012) thus constitute an
easy-to-use analytical model that accurately describes the remnant of black
hole-neutron star mergers. The space of parameters consisting of the binary
mass ratio, the initial black hole spin, and the neutron star mass and equation
of state is investigated. We provide indirect support to the cosmic censorship
conjecture for black hole remnants of black hole-neutron star mergers. We show
that the presence of a neutron star affects the quasinormal mode frequency of
the black hole remnant, thus suggesting that the ringdown epoch of the
gravitational wave signal may virtually be used to (1) distinguish black
hole-black hole from black hole-neutron star mergers and to (2) constrain the
neutron star equation of state.
| [
{
"created": "Wed, 29 Aug 2012 09:27:59 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Nov 2013 23:07:19 GMT",
"version": "v2"
}
] | 2013-11-26 | [
[
"Pannarale",
"Francesco",
""
]
] | We present a model for determining the dimensionless spin parameter and mass of the black hole remnant of black hole-neutron star mergers with parallel orbital angular momentum and initial black hole spin. This approach is based on the Buonanno, Kidder, and Lehner method for binary black holes, and it is successfully tested against the results of numerical-relativity simulations: the dimensionless spin parameter is predicted with absolute error $\lesssim 0.02$, whereas the relative error on the final mass is $\lesssim 2$%, its distribution in the tests being pronouncedly peaked at $1$%. Our approach and the fit to the torus remnant mass reported in Foucart (2012) thus constitute an easy-to-use analytical model that accurately describes the remnant of black hole-neutron star mergers. The space of parameters consisting of the binary mass ratio, the initial black hole spin, and the neutron star mass and equation of state is investigated. We provide indirect support to the cosmic censorship conjecture for black hole remnants of black hole-neutron star mergers. We show that the presence of a neutron star affects the quasinormal mode frequency of the black hole remnant, thus suggesting that the ringdown epoch of the gravitational wave signal may virtually be used to (1) distinguish black hole-black hole from black hole-neutron star mergers and to (2) constrain the neutron star equation of state. |
2012.14720 | Massimo Giovannini | Massimo Giovannini | Inflationary magnetogenesis in the perturbative regime | 41 pages; 10 figures | Class.Quant.Grav. 38 (2021) 13, 135018 | 10.1088/1361-6382/abf899 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | While during inflation a phase of increasing gauge coupling allows for a
scale-invariant hyperelectric spectrum, when the coupling decreases a flat
hypermagnetic spectrum can be generated for typical wavelengths larger than the
effective horizon. After the gauge coupling flattens out the late-time
hypermagnetic power spectra outside the horizon in the radiation epoch are
determined by the hyperelectric fields at the end of inflation whereas the
opposite is true in the case of decreasing coupling. Instead of imposing an
abrupt freeze after inflation, we consider a smooth evolution of the mode
functions by positing that the gauge couplings and their conformal time
derivatives are always continuous together with the background extrinsic
curvature. The amplified gauge power spectra are classified according to their
transformation properties under the duality symmetry. After clarifying the role
of the comoving and of the physical spectra in the formulation of the relevant
magnetogenesis constraints, the parameter space of the scenario is scrutinized.
It turns out that a slightly blue hyperelectric spectrum during inflation may
lead to a quasi-flat hypermagnetic spectrum prior to matter radiation equality
and before the relevant wavelengths reenter the effective horizon. In this
framework the gauge coupling is always perturbative but the induced large-scale
magnetic fields can be of the order of a few hundredths of a nG and over
typical length scales between a fraction of the Mpc and $100$ Mpc prior to the
gravitational collapse of the protogalaxy.
| [
{
"created": "Tue, 29 Dec 2020 12:03:33 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Jun 2021 20:54:43 GMT",
"version": "v2"
}
] | 2021-06-08 | [
[
"Giovannini",
"Massimo",
""
]
] | While during inflation a phase of increasing gauge coupling allows for a scale-invariant hyperelectric spectrum, when the coupling decreases a flat hypermagnetic spectrum can be generated for typical wavelengths larger than the effective horizon. After the gauge coupling flattens out the late-time hypermagnetic power spectra outside the horizon in the radiation epoch are determined by the hyperelectric fields at the end of inflation whereas the opposite is true in the case of decreasing coupling. Instead of imposing an abrupt freeze after inflation, we consider a smooth evolution of the mode functions by positing that the gauge couplings and their conformal time derivatives are always continuous together with the background extrinsic curvature. The amplified gauge power spectra are classified according to their transformation properties under the duality symmetry. After clarifying the role of the comoving and of the physical spectra in the formulation of the relevant magnetogenesis constraints, the parameter space of the scenario is scrutinized. It turns out that a slightly blue hyperelectric spectrum during inflation may lead to a quasi-flat hypermagnetic spectrum prior to matter radiation equality and before the relevant wavelengths reenter the effective horizon. In this framework the gauge coupling is always perturbative but the induced large-scale magnetic fields can be of the order of a few hundredths of a nG and over typical length scales between a fraction of the Mpc and $100$ Mpc prior to the gravitational collapse of the protogalaxy. |
2308.12368 | Petr Jizba | Petr Jizba, Gaetano Lambiase, Giuseppe Gaetano Luciano and Luciano
Petruzziello | Coherent states for generalized uncertainty relations as Tsallis
probability amplitudes: new route to non-extensive thermostatistics | 25 pages, 4 figures, accepted to Physical Review D | Phys. Rev. D 108, 064024 (2023) | 10.1103/PhysRevD.108.064024 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We study coherent states associated to a generalized uncertainty principle
(GUP). We separately analyze the cases of positive and negative deformation
parameter $\beta$, showing that the ensuing probability distribution is a
Tsallis distribution whose non-extensivity parameter $q$ is monotonically
related to $\beta$. Moreover, for $\beta <0$ (corresponding to $q<1$), we
reformulate the GUP in terms of a one-parameter class of Tsallis entropy-power
based uncertainty relations, which are again saturated by the GUP coherent
states. We argue that this combination of coherent states with Tsallis entropy
offers a natural conceptual framework allowing to study quasi-classical regime
of GUP in terms of non-extensive thermodynamics. We substantiate our claim by
discussing generalization of Verlinde's entropic force and ensuing implications
in the late-inflation epoch. Corresponding dependence of the $\beta$ parameter
on cosmological time is derived for the reheating epoch. The obtained $\beta$
is consistent with values predicted by both string-theory models and the
naturalness principle. Further salient issues, including derivation of new
$\beta$-dependent expressions for the lowest possible value of the spin and
Immirzi parameter in Loop Quantum Gravity, and connection of our proposal with
the Magueijo--Smolin doubly special relativity are also discussed. This article
provides a more extended and comprehensive treatment of our recent letter
[Phys. Rev. D 105, L121501 (2022)].
| [
{
"created": "Wed, 23 Aug 2023 18:16:15 GMT",
"version": "v1"
}
] | 2023-09-13 | [
[
"Jizba",
"Petr",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Luciano",
"Giuseppe Gaetano",
""
],
[
"Petruzziello",
"Luciano",
""
]
] | We study coherent states associated to a generalized uncertainty principle (GUP). We separately analyze the cases of positive and negative deformation parameter $\beta$, showing that the ensuing probability distribution is a Tsallis distribution whose non-extensivity parameter $q$ is monotonically related to $\beta$. Moreover, for $\beta <0$ (corresponding to $q<1$), we reformulate the GUP in terms of a one-parameter class of Tsallis entropy-power based uncertainty relations, which are again saturated by the GUP coherent states. We argue that this combination of coherent states with Tsallis entropy offers a natural conceptual framework allowing to study quasi-classical regime of GUP in terms of non-extensive thermodynamics. We substantiate our claim by discussing generalization of Verlinde's entropic force and ensuing implications in the late-inflation epoch. Corresponding dependence of the $\beta$ parameter on cosmological time is derived for the reheating epoch. The obtained $\beta$ is consistent with values predicted by both string-theory models and the naturalness principle. Further salient issues, including derivation of new $\beta$-dependent expressions for the lowest possible value of the spin and Immirzi parameter in Loop Quantum Gravity, and connection of our proposal with the Magueijo--Smolin doubly special relativity are also discussed. This article provides a more extended and comprehensive treatment of our recent letter [Phys. Rev. D 105, L121501 (2022)]. |
gr-qc/0503022 | Steven Carlip | S. Carlip | Conformal Field Theory, (2+1)-Dimensional Gravity, and the BTZ Black
Hole | 50 pages, LaTeX; draft of review article -- comments, corrections,
additions, complaints welcomed; v2: more and better references, minor
additions; v3: more references; v4: minor typos corrected to match published
version | Class.Quant.Grav.22:R85-R124,2005 | 10.1088/0264-9381/22/12/R01 | UCD-05-02 | gr-qc hep-th | null | In three spacetime dimensions, general relativity becomes a topological field
theory, whose dynamics can be largely described holographically by a
two-dimensional conformal field theory at the ``boundary'' of spacetime. I
review what is known about this reduction--mainly within the context of pure
(2+1)-dimensional gravity--and discuss its implications for our understanding
of the statistical mechanics and quantum mechanics of black holes.
| [
{
"created": "Fri, 4 Mar 2005 22:56:40 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Mar 2005 01:04:28 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Mar 2005 18:59:47 GMT",
"version": "v3"
},
{
"created": "Mon, 6 Jun 2005 20:59:34 GMT",
"version": "v4"
}
] | 2010-04-28 | [
[
"Carlip",
"S.",
""
]
] | In three spacetime dimensions, general relativity becomes a topological field theory, whose dynamics can be largely described holographically by a two-dimensional conformal field theory at the ``boundary'' of spacetime. I review what is known about this reduction--mainly within the context of pure (2+1)-dimensional gravity--and discuss its implications for our understanding of the statistical mechanics and quantum mechanics of black holes. |
1211.5957 | Harvey S. Reall | Harvey S. Reall, Alexander A. H. Graham and Carl P. Turner | On algebraically special vacuum spacetimes in five dimensions | 25 pages. v2: typos corrected | null | 10.1088/0264-9381/30/5/055004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Vacuum solutions admitting a hypersurface-orthogonal repeated principal null
direction are an important class of 4d algebraically special spacetimes. We
investigate the 5d analogues of such solutions: vacuum spacetimes admitting a
hypersurface-orthogonal multiple Weyl aligned null direction (WAND). Such
spacetimes fall into 4 families determined by the rank of the 3X3 matrix that
defines the expansion and shear of the multiple WAND. The rank 3 and rank 0
cases have been studied previously. We investigate the 2 remaining families. We
show how to define coordinates which lead to a considerable simplification of
the Einstein equation with cosmological constant. The rank 2 case gives warped
product and Kaluza-Klein versions of the 4d Robinson-Trautman solutions as well
as some new solutions. The rank 1 case gives product, or analytically continued
Schwarzschild, spacetimes.
| [
{
"created": "Mon, 26 Nov 2012 14:10:23 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jan 2013 11:02:16 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Reall",
"Harvey S.",
""
],
[
"Graham",
"Alexander A. H.",
""
],
[
"Turner",
"Carl P.",
""
]
] | Vacuum solutions admitting a hypersurface-orthogonal repeated principal null direction are an important class of 4d algebraically special spacetimes. We investigate the 5d analogues of such solutions: vacuum spacetimes admitting a hypersurface-orthogonal multiple Weyl aligned null direction (WAND). Such spacetimes fall into 4 families determined by the rank of the 3X3 matrix that defines the expansion and shear of the multiple WAND. The rank 3 and rank 0 cases have been studied previously. We investigate the 2 remaining families. We show how to define coordinates which lead to a considerable simplification of the Einstein equation with cosmological constant. The rank 2 case gives warped product and Kaluza-Klein versions of the 4d Robinson-Trautman solutions as well as some new solutions. The rank 1 case gives product, or analytically continued Schwarzschild, spacetimes. |
1702.01593 | Andronikos Paliathanasis | Andronikos Paliathanasis and P.G.L. Leach | Symmetries and Singularities of the Szekeres System | 6 pages, to be published in Phys. Lett. A | Phys. Lett. A 381, 1277 (2017) | 10.1016/j.physleta.2017.02.009 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Szekeres system is studied with two methods for the determination of
conservation laws. Specifically we apply the theory of group invariant
transformations and the method of singularity analysis. We show that the
Szekeres system admits a Lagrangian and the conservation laws that we find can
be derived by the application of Noether's theorem. The stability for the
special solutions of the Szekeres system is studied and it is related with the
with the Left or Right Painlev\'e Series which describes the expansions.
| [
{
"created": "Mon, 6 Feb 2017 12:32:19 GMT",
"version": "v1"
}
] | 2017-03-09 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Leach",
"P. G. L.",
""
]
] | The Szekeres system is studied with two methods for the determination of conservation laws. Specifically we apply the theory of group invariant transformations and the method of singularity analysis. We show that the Szekeres system admits a Lagrangian and the conservation laws that we find can be derived by the application of Noether's theorem. The stability for the special solutions of the Szekeres system is studied and it is related with the with the Left or Right Painlev\'e Series which describes the expansions. |
2312.16804 | Daniel R Terno | Pravin K. Dahal, Swayamsiddha Maharana, Fil Simovic, Ioannis
Soranidis, and Daniel R. Terno | Models of cosmological black holes | 8 pages, 2 figures. Comments welcome! | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study various aspects of modeling astrophysical black holes using the
recently introduced semiclassical formalism of physical black holes (PBHs).
This approach is based on the minimal requirements of observability and
regularity of the horizons. We demonstrate that PBHs do not directly couple to
the cosmological background in the current epoch, and their equation of state
renders them unsuitable for describing dark energy. Utilizing their properties
for analysis of more exotic models, we present a consistent semiclassical
scenario for a black-to-white hole bounce and identify obstacles to the
transformation from a black hole horizon to a wormhole mouth.
| [
{
"created": "Thu, 28 Dec 2023 03:18:54 GMT",
"version": "v1"
}
] | 2023-12-29 | [
[
"Dahal",
"Pravin K.",
""
],
[
"Maharana",
"Swayamsiddha",
""
],
[
"Simovic",
"Fil",
""
],
[
"Soranidis",
"Ioannis",
""
],
[
"Terno",
"Daniel R.",
""
]
] | We study various aspects of modeling astrophysical black holes using the recently introduced semiclassical formalism of physical black holes (PBHs). This approach is based on the minimal requirements of observability and regularity of the horizons. We demonstrate that PBHs do not directly couple to the cosmological background in the current epoch, and their equation of state renders them unsuitable for describing dark energy. Utilizing their properties for analysis of more exotic models, we present a consistent semiclassical scenario for a black-to-white hole bounce and identify obstacles to the transformation from a black hole horizon to a wormhole mouth. |
2107.02386 | Mohammad Ali Gorji | Jibril Ben Achour, Antonio De Felice, Mohammad Ali Gorji, Shinji
Mukohyama, Masroor C. Pookkillath | Disformal map and Petrov classification in modified gravity | 26+11 pages, 2 tables, matches the published version | null | 10.1088/1475-7516/2021/10/067 | YITP-21-72, IPMU21-0046 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Disformal transformation provides a map relating different scalar-tensor and
vector-tensor theories and gives access to a powerful solution-generating
method in modified gravity. In view of the vast family of new solutions one can
achieve, it is crucial to design suitable tools to guide their construction. In
this work, we address this question by revisiting the Petrov classification of
disformally constructed solutions in modified gravity theories. We provide
close formulas which relate the principal nulls directions as well as the Weyl
scalars before and after the disformal transformation. These formulas allow one
to capture if and how the Petrov type of a given seed geometry changes under a
disformal transformation. Finally, we apply our general setup to three relevant
disformally constructed solutions for which the seeds are respectively
homogeneous and isotropic, static spherically symmetric and stationary
axisymmetric. For the first two cases, we show that the Petrov type O and
Petrov type D remain unchanged after a disformal transformation while we show
that disformed Kerr black hole is no longer of type D but of general Petrov
type I. The results presented in this work should serve as a new toolkit when
constructing and comparing new disformal solutions in modified gravity.
| [
{
"created": "Tue, 6 Jul 2021 04:52:08 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Feb 2022 00:58:23 GMT",
"version": "v2"
}
] | 2022-02-09 | [
[
"Achour",
"Jibril Ben",
""
],
[
"De Felice",
"Antonio",
""
],
[
"Gorji",
"Mohammad Ali",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Pookkillath",
"Masroor C.",
""
]
] | Disformal transformation provides a map relating different scalar-tensor and vector-tensor theories and gives access to a powerful solution-generating method in modified gravity. In view of the vast family of new solutions one can achieve, it is crucial to design suitable tools to guide their construction. In this work, we address this question by revisiting the Petrov classification of disformally constructed solutions in modified gravity theories. We provide close formulas which relate the principal nulls directions as well as the Weyl scalars before and after the disformal transformation. These formulas allow one to capture if and how the Petrov type of a given seed geometry changes under a disformal transformation. Finally, we apply our general setup to three relevant disformally constructed solutions for which the seeds are respectively homogeneous and isotropic, static spherically symmetric and stationary axisymmetric. For the first two cases, we show that the Petrov type O and Petrov type D remain unchanged after a disformal transformation while we show that disformed Kerr black hole is no longer of type D but of general Petrov type I. The results presented in this work should serve as a new toolkit when constructing and comparing new disformal solutions in modified gravity. |
1611.05326 | Julio Cesar Fabris | J\'ulio C. Fabris, Tays Miranda, Oliver F. Piattella | An exponential correction to Starobinsky's inflationary model | Latex file, 6 pages, 2 figures. For the Proceedings of the
International Conference on Particle Physics and Astrophysics, ICPPA 2016,
October 10-14 2016, Moscow, Russia | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse $f(R)$ theories of gravity from a dynamical system perspective,
showing how the $R^2$ correction in Starobinsky's model plays a crucial role
from the viewpoint of the inflationary paradigm. Then, we propose a
modification of Starobinsky's model by adding an exponential term in the $f(R)$
Lagrangian. We show how this modification could allow to test the robustness of
the model by means of the predictions on the scalar spectral index $n_s$.
| [
{
"created": "Tue, 15 Nov 2016 13:08:29 GMT",
"version": "v1"
}
] | 2016-11-17 | [
[
"Fabris",
"Júlio C.",
""
],
[
"Miranda",
"Tays",
""
],
[
"Piattella",
"Oliver F.",
""
]
] | We analyse $f(R)$ theories of gravity from a dynamical system perspective, showing how the $R^2$ correction in Starobinsky's model plays a crucial role from the viewpoint of the inflationary paradigm. Then, we propose a modification of Starobinsky's model by adding an exponential term in the $f(R)$ Lagrangian. We show how this modification could allow to test the robustness of the model by means of the predictions on the scalar spectral index $n_s$. |
2205.10566 | Luciano Petruzziello | Luciano Petruzziello | Equivalence principle violation from large scale structure | null | null | 10.1016/j.physletb.2022.137293 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We explore the interplay between the equivalence principle and a
generalization of the Heisenberg uncertainty relations known as extended
uncertainty principle, that comprises the effects of spacetime curvature at
large distances. Specifically, we observe that, when the modified uncertainty
relations hold, the weak formulation of the equivalence principle is violated,
since the inertial mass of quantum systems becomes position-dependent whilst
the gravitational mass is left untouched. To obtain the above result, spinor
and scalar fields are separately analyzed by considering the non-relativistic
limit of the Dirac and the Klein-Gordon equations in the presence of the
extended uncertainty principle. In both scenarios, it is found that the ratio
between the inertial and the gravitational mass is the same.
| [
{
"created": "Sat, 21 May 2022 11:17:15 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Petruzziello",
"Luciano",
""
]
] | We explore the interplay between the equivalence principle and a generalization of the Heisenberg uncertainty relations known as extended uncertainty principle, that comprises the effects of spacetime curvature at large distances. Specifically, we observe that, when the modified uncertainty relations hold, the weak formulation of the equivalence principle is violated, since the inertial mass of quantum systems becomes position-dependent whilst the gravitational mass is left untouched. To obtain the above result, spinor and scalar fields are separately analyzed by considering the non-relativistic limit of the Dirac and the Klein-Gordon equations in the presence of the extended uncertainty principle. In both scenarios, it is found that the ratio between the inertial and the gravitational mass is the same. |
1004.5435 | Kiyoshi Shiraishi | Teruki Hanada, Koichiro Kobayashi, Kazuhiko Shinoda and Kiyoshi
Shiraishi (Yamaguchi University) | Classical and Quantum Cosmology of Multigravity | 17 pages, 15 figures, RevTeX4.1, revised version | Class.Quant.Grav.27:225010,2010 | 10.1088/0264-9381/27/22/225010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a multigraviton theory on a simple closed circuit graph
corresponding to the discretization of $S^1$ compactification of the
Kaluza-Klein (KK) theory has been considered. In the present paper, we extend
this theory to that on a general graph and study what modes of particles are
included. Furthermore, we generalize it in a possible nonlinear theory based on
the vierbein formalism and study classical and quantum cosmological solutions
in the theory. We found that scale factors in a solution for this theory repeat
acceleration and deceleration.
| [
{
"created": "Fri, 30 Apr 2010 02:27:44 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Aug 2010 10:32:01 GMT",
"version": "v2"
}
] | 2011-01-27 | [
[
"Hanada",
"Teruki",
"",
"Yamaguchi University"
],
[
"Kobayashi",
"Koichiro",
"",
"Yamaguchi University"
],
[
"Shinoda",
"Kazuhiko",
"",
"Yamaguchi University"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi University"
]
] | Recently, a multigraviton theory on a simple closed circuit graph corresponding to the discretization of $S^1$ compactification of the Kaluza-Klein (KK) theory has been considered. In the present paper, we extend this theory to that on a general graph and study what modes of particles are included. Furthermore, we generalize it in a possible nonlinear theory based on the vierbein formalism and study classical and quantum cosmological solutions in the theory. We found that scale factors in a solution for this theory repeat acceleration and deceleration. |
2312.06618 | Sergey L Cherkas | Sergey L. Cherkas and Vladimir L. Kalashnikov | Scalar Product for a Version of Minisuperspace Model with Grassmann
Variables | 20 pages, 3 figures | Universe 2023, 9(12), 508 | 10.3390/universe9120508 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Grassmann variables are used to formally transform a system with constraints
into an unconstrained system. As a result, the Schr\"{o}dinger equation arises
instead of the Wheeler-DeWitt one. The Schr\"{o}dinger equation describes a
system's evolution, but a definition of the scalar product is needed to
calculate the mean values of the operators. We suggest an explicit formula for
the scalar product related to the Klein-Gordon scalar product. The calculation
of the mean values is compared with an etalon method in which a redundant
degree of freedom is excluded. Nevertheless, we note that a complete
correspondence with the etalon picture is not found. Apparently, the picture
with Grassmann variables requires a further understanding of the underlying
Hilbert space.
| [
{
"created": "Fri, 8 Dec 2023 11:35:08 GMT",
"version": "v1"
}
] | 2023-12-12 | [
[
"Cherkas",
"Sergey L.",
""
],
[
"Kalashnikov",
"Vladimir L.",
""
]
] | Grassmann variables are used to formally transform a system with constraints into an unconstrained system. As a result, the Schr\"{o}dinger equation arises instead of the Wheeler-DeWitt one. The Schr\"{o}dinger equation describes a system's evolution, but a definition of the scalar product is needed to calculate the mean values of the operators. We suggest an explicit formula for the scalar product related to the Klein-Gordon scalar product. The calculation of the mean values is compared with an etalon method in which a redundant degree of freedom is excluded. Nevertheless, we note that a complete correspondence with the etalon picture is not found. Apparently, the picture with Grassmann variables requires a further understanding of the underlying Hilbert space. |
2202.04323 | Luisa Jaime | Luisa G. Jaime and Gustavo Arciniega | A unified geometric description of the Universe: from inflation to
late-time acceleration without an inflaton nor a cosmological constant | Accepted in Physics Letters B. 13 pages, 4 figures | null | 10.1016/j.physletb.2022.136939 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a cosmological model arising from a gravitational theory with an
infinite tower of higher-order curvature invariants that can reproduce the
entire evolution of the Universe: from inflation to late-time acceleration,
without invoking an inflaton nor a cosmological constant. The theory is
Einsteinian-like. The field equations for a
Friedmann-Lema\^{i}tre-Robertson-Walker metric are of second-order and can
reproduce a late-time evolution that is consistent with the acceleration
provided by the cosmological constant at low redshift. Our results force us to
reinterpret the nature of dark energy, becoming a mechanism that is inherited
solely from the geometry of spacetime.
| [
{
"created": "Wed, 9 Feb 2022 08:07:49 GMT",
"version": "v1"
}
] | 2022-02-10 | [
[
"Jaime",
"Luisa G.",
""
],
[
"Arciniega",
"Gustavo",
""
]
] | We present a cosmological model arising from a gravitational theory with an infinite tower of higher-order curvature invariants that can reproduce the entire evolution of the Universe: from inflation to late-time acceleration, without invoking an inflaton nor a cosmological constant. The theory is Einsteinian-like. The field equations for a Friedmann-Lema\^{i}tre-Robertson-Walker metric are of second-order and can reproduce a late-time evolution that is consistent with the acceleration provided by the cosmological constant at low redshift. Our results force us to reinterpret the nature of dark energy, becoming a mechanism that is inherited solely from the geometry of spacetime. |
2206.07066 | Gianluca Calcagni | Gianluca Calcagni, Leonardo Modesto | Testing quantum gravity with primordial gravitational waves | 1+33 pages, 2 figures. v2: nature of beta coefficients clarified. v3:
expanded version, new introduction and summary of setting, derivation of
cosmological spectra moved from companion paper arXiv:2206.06384 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a testable alternative to inflation directly built in a very
general class of ultraviolet complete theories of quantum gravity enjoying Weyl
conformal invariance. After the latter is spontaneously broken, logarithmic
quantum corrections to the action make both the primordial tensor spectrum
(from graviton fluctuations) and the scalar spectrum (from thermal
fluctuations) quasi scale invariant. We predict a scalar spectral index $n_{\rm
s}$ which only depends on two parameters and is consistent with observations, a
tensor index $n_{\rm t} =1-n_{\rm s}>0$, a tensor-to-scalar ratio
$r_{0.05}\approx 0.01$ detectable by BICEP Array and LiteBIRD in the immediate
or near future, respectively, and a blue-tilted stochastic gravitational-wave
background observable by DECIGO in the further future.
| [
{
"created": "Tue, 14 Jun 2022 18:00:03 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jul 2022 02:43:23 GMT",
"version": "v2"
},
{
"created": "Wed, 29 May 2024 11:02:21 GMT",
"version": "v3"
}
] | 2024-05-30 | [
[
"Calcagni",
"Gianluca",
""
],
[
"Modesto",
"Leonardo",
""
]
] | We propose a testable alternative to inflation directly built in a very general class of ultraviolet complete theories of quantum gravity enjoying Weyl conformal invariance. After the latter is spontaneously broken, logarithmic quantum corrections to the action make both the primordial tensor spectrum (from graviton fluctuations) and the scalar spectrum (from thermal fluctuations) quasi scale invariant. We predict a scalar spectral index $n_{\rm s}$ which only depends on two parameters and is consistent with observations, a tensor index $n_{\rm t} =1-n_{\rm s}>0$, a tensor-to-scalar ratio $r_{0.05}\approx 0.01$ detectable by BICEP Array and LiteBIRD in the immediate or near future, respectively, and a blue-tilted stochastic gravitational-wave background observable by DECIGO in the further future. |
1010.0878 | Sasa Ilijic | Dubravko Horvat, Sasa Ilijic, Anja Marunovic | Radial pulsations and stability of anisotropic stars with quasi-local
equation of state | 15 pages, 3 figures, v2: very minor changes, matches published
version | Class.Quant.Grav.28:025009,2011 | 10.1088/0264-9381/28/2/025009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasi-local variables, i.e. quantities whose values can be derived from
physics accessible within an arbitrarily small neighborhood of a spacetime
point, are used to construct the equation of state (EoS) for the anisotropic
fluid in the spherical symmetry. One parameter families of equilibrium
solutions are obtained making it possible to assess stability properties by
means of the standard M(R) method. Normal modes of radial pulsation are
computed as well and are found to confirm the onset of instability as predicted
by the M(R) method. As an example, a stable configuration with outwardly
increasing energy density in the core is obtained with a simple quasi-local
extension of the polytropic EoS. It is also found that the loss of stability
occurs at higher surface compactness when the anisotropy of pressures is
present.
| [
{
"created": "Tue, 5 Oct 2010 13:30:10 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jan 2011 08:03:05 GMT",
"version": "v2"
}
] | 2011-01-20 | [
[
"Horvat",
"Dubravko",
""
],
[
"Ilijic",
"Sasa",
""
],
[
"Marunovic",
"Anja",
""
]
] | Quasi-local variables, i.e. quantities whose values can be derived from physics accessible within an arbitrarily small neighborhood of a spacetime point, are used to construct the equation of state (EoS) for the anisotropic fluid in the spherical symmetry. One parameter families of equilibrium solutions are obtained making it possible to assess stability properties by means of the standard M(R) method. Normal modes of radial pulsation are computed as well and are found to confirm the onset of instability as predicted by the M(R) method. As an example, a stable configuration with outwardly increasing energy density in the core is obtained with a simple quasi-local extension of the polytropic EoS. It is also found that the loss of stability occurs at higher surface compactness when the anisotropy of pressures is present. |
gr-qc/0408093 | Yuri Shtanov | Dmytro Iakubovskyi and Yuri Shtanov | Braneworld cosmological solutions and their stability | 23 pages, 2 figures, sections 3 and 4 revised, matches the version to
be published | Class.Quant.Grav. 22 (2005) 2415-2432 | 10.1088/0264-9381/22/12/008 | null | gr-qc | null | We consider cosmological solutions and their stability with respect to
homogeneous and isotropic perturbations in the braneworld model with the
scalar-curvature term in the action for the brane. Part of the results are
similar to those obtained by Campos and Sopuerta for the Randall-Sundrum
braneworld model. Specifically, the expanding de Sitter solution is an
attractor, while the expanding Friedmann solution is a repeller. In the
braneworld theory with the scalar-curvature term in the action for the brane,
static solutions with matter satisfying the strong energy condition exist not
only with closed spatial geometry but also with open and flat ones even in the
case where the dark-radiation contribution is absent. In a certain range of
parameters, static solutions are stable with respect to homogeneous and
isotropic perturbations.
| [
{
"created": "Mon, 30 Aug 2004 14:10:46 GMT",
"version": "v1"
},
{
"created": "Sat, 7 May 2005 15:57:18 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Iakubovskyi",
"Dmytro",
""
],
[
"Shtanov",
"Yuri",
""
]
] | We consider cosmological solutions and their stability with respect to homogeneous and isotropic perturbations in the braneworld model with the scalar-curvature term in the action for the brane. Part of the results are similar to those obtained by Campos and Sopuerta for the Randall-Sundrum braneworld model. Specifically, the expanding de Sitter solution is an attractor, while the expanding Friedmann solution is a repeller. In the braneworld theory with the scalar-curvature term in the action for the brane, static solutions with matter satisfying the strong energy condition exist not only with closed spatial geometry but also with open and flat ones even in the case where the dark-radiation contribution is absent. In a certain range of parameters, static solutions are stable with respect to homogeneous and isotropic perturbations. |
1106.1448 | Seth A. Major | Franz Hinterleitner and Seth Major | Towards Loop Quantization of Plane Gravitational Waves | 14 pages | null | 10.1088/0264-9381/29/6/065019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The polarized Gowdy model in terms of Ashtekar-Barbero variables is further
reduced by including the Killing equations for plane-fronted parallel
gravitational waves with parallel rays. The resulting constraint algebra,
including one constraint derived from the Killing equations in addition to the
standard ones of General Relativity, are shown to form a set of first-class
constraints. Using earlier work by Banerjee and Date the constraints are
expressed in terms of classical quantities that have an operator equivalent in
Loop Quantum Gravity, making space-times with pp-waves accessible to loop
quantization techniques.
| [
{
"created": "Tue, 7 Jun 2011 20:22:25 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Hinterleitner",
"Franz",
""
],
[
"Major",
"Seth",
""
]
] | The polarized Gowdy model in terms of Ashtekar-Barbero variables is further reduced by including the Killing equations for plane-fronted parallel gravitational waves with parallel rays. The resulting constraint algebra, including one constraint derived from the Killing equations in addition to the standard ones of General Relativity, are shown to form a set of first-class constraints. Using earlier work by Banerjee and Date the constraints are expressed in terms of classical quantities that have an operator equivalent in Loop Quantum Gravity, making space-times with pp-waves accessible to loop quantization techniques. |
2403.17457 | Shunsuke Fujii | Akio Hosoya, Shunsuke Fujii | Energy-momentum Tensor: Noether vs Hilbert | After further confirmation of other published papers, we found that
our paper is not new. Thus we are going to withdraw our paper from arXiv | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the old problem of the energy-momentum tensor in general
relativistic field theories. On the basis of the general covariance we derive a
simple equation for the Hilbert and Noether energy-momentum tensors for the
scalar and electromagnetic field theories. We see that the two definitions of
energy-momentum tensors coincide and identify the Noether current if the
space-time has the Killing vector. Relation to the Wald entropy is also briefly
discussed.
| [
{
"created": "Tue, 26 Mar 2024 07:46:26 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2024 05:57:23 GMT",
"version": "v2"
}
] | 2024-05-01 | [
[
"Hosoya",
"Akio",
""
],
[
"Fujii",
"Shunsuke",
""
]
] | We revisit the old problem of the energy-momentum tensor in general relativistic field theories. On the basis of the general covariance we derive a simple equation for the Hilbert and Noether energy-momentum tensors for the scalar and electromagnetic field theories. We see that the two definitions of energy-momentum tensors coincide and identify the Noether current if the space-time has the Killing vector. Relation to the Wald entropy is also briefly discussed. |
1906.11311 | Jorge Ernesto Horvath | L. S. Rocha (IAG - USP, Brazil), A. Bernardo (IAG - USP, Brazil), M.
G. B. de Avellar (UNIFESP - Diadema and ITA - S\~ao Jos\'e dos Campos,
Brazil), J. E. Horvath (IAG - USP, Brazil) | Exact solutions for compact stars with CFL quark matter | Submitted to IJMPD on January 2020, 13 pages, 6 figures, anisotropy
discussion enlarged and clarified | null | 10.1142/S0218271820500443 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The search for the true ground state of the dense matter remains open since
Bodmer, Terazawa and other raised the possibility of stable quarks, boosted by
Witten's $strange$ $matter$ hypothesis in 1984. Within this proposal, the
strange matter is assumed to be composed of $strange$ quarks in addition to the
usual $up$s and $down$s, having an energy per baryon lower than the strangeless
counterpart, and even lower than that of nuclear matter. In this sense, neutron
stars should actually be strange stars. Later work showed that a paired,
symmetric in flavor, color-flavor locked (CFL) state would be preferred to the
one without any pairing for a wide range of the parameters (gap $\Delta$,
strange quark mass $m_s$, and bag constant B). We use an approximate, yet very
accurate, CFL equation of state (EoS) that generalizes the MIT bag model to
obtain two families of exact solutions for the static Einstein field equations
constructing families anisotropic compact relativistic objects. In this
fashion, we provide exact useful solutions directly connected with
microphysics.
| [
{
"created": "Wed, 26 Jun 2019 19:38:30 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2019 03:42:19 GMT",
"version": "v2"
},
{
"created": "Sat, 9 Nov 2019 16:07:19 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Jan 2020 15:34:17 GMT",
"version": "v4"
}
] | 2020-07-15 | [
[
"Rocha",
"L. S.",
"",
"IAG - USP, Brazil"
],
[
"Bernardo",
"A.",
"",
"IAG - USP, Brazil"
],
[
"de Avellar",
"M. G. B.",
"",
"UNIFESP - Diadema and ITA - São José dos Campos,\n Brazil"
],
[
"Horvath",
"J. E.",
"",
"IAG - USP, Brazil"
]
] | The search for the true ground state of the dense matter remains open since Bodmer, Terazawa and other raised the possibility of stable quarks, boosted by Witten's $strange$ $matter$ hypothesis in 1984. Within this proposal, the strange matter is assumed to be composed of $strange$ quarks in addition to the usual $up$s and $down$s, having an energy per baryon lower than the strangeless counterpart, and even lower than that of nuclear matter. In this sense, neutron stars should actually be strange stars. Later work showed that a paired, symmetric in flavor, color-flavor locked (CFL) state would be preferred to the one without any pairing for a wide range of the parameters (gap $\Delta$, strange quark mass $m_s$, and bag constant B). We use an approximate, yet very accurate, CFL equation of state (EoS) that generalizes the MIT bag model to obtain two families of exact solutions for the static Einstein field equations constructing families anisotropic compact relativistic objects. In this fashion, we provide exact useful solutions directly connected with microphysics. |
1009.3427 | Thomas M\"uller | Sebastian Boblest, Thomas M\"uller, G\"unter Wunner | Twin Paradox in de Sitter Spacetime | 15 pages, 19 figures, 5 tables | Eur.J.Phys.32:1117-1142,2011 | 10.1088/0143-0807/32/5/001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The "twin paradox" of special relativity offers the possibility to make
interstellar flights within a lifetime. For very long journeys with velocities
close to the speed of light, however, we have to take into account the
expansion of the universe. Inspired by the work of Rindler on hyperbolic motion
in curved spacetime, we study the worldline of a uniformly accelerated observer
in de Sitter spacetime and the communication between the traveling observer and
an observer at rest.
| [
{
"created": "Wed, 1 Sep 2010 17:05:16 GMT",
"version": "v1"
}
] | 2011-07-28 | [
[
"Boblest",
"Sebastian",
""
],
[
"Müller",
"Thomas",
""
],
[
"Wunner",
"Günter",
""
]
] | The "twin paradox" of special relativity offers the possibility to make interstellar flights within a lifetime. For very long journeys with velocities close to the speed of light, however, we have to take into account the expansion of the universe. Inspired by the work of Rindler on hyperbolic motion in curved spacetime, we study the worldline of a uniformly accelerated observer in de Sitter spacetime and the communication between the traveling observer and an observer at rest. |
gr-qc/0408025 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Consistent discretizations and quantum gravity | 7 pages, to appear in the proceedings of The II International
Conference on > Fundamental Interactions, O. Piguet (editor), Editora UNESP,
Sao Paulo | null | null | LSU-REL-080904 | gr-qc | null | We review a recent proposal for the construction of a quantum theory of the
gravitational field. The proposal is based on approximating the continuum
theory by a discrete theory that has several attractive properties, among them,
the fact that in its canonical formulation it is free of constraints. This
allows to bypass many of the hard conceptual problems of traditional canonical
quantum gravity. In particular the resulting theory implies a fundamental
mechanism for decoherence and bypasses the black hole information paradox.
| [
{
"created": "Mon, 9 Aug 2004 21:52:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We review a recent proposal for the construction of a quantum theory of the gravitational field. The proposal is based on approximating the continuum theory by a discrete theory that has several attractive properties, among them, the fact that in its canonical formulation it is free of constraints. This allows to bypass many of the hard conceptual problems of traditional canonical quantum gravity. In particular the resulting theory implies a fundamental mechanism for decoherence and bypasses the black hole information paradox. |
1608.03489 | Adrian Melissinos | Adrian Melissinos | Use of the gravitational-wave interferometers to test Lorentz invariance
violation | Presented at the Seventh Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 20-24, 2016 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Currently operating gravitational-wave interferometers are Michelson
interferometers with effective arm length L ~ 4x10e5 m. While the
interferometer remains in lock, data at the fsr sideband frequency encode
information on slow phase changes in the f ~ 10e-5 Hz range, with a fringe
sensitivity ~ 10e-10. Preliminary LIGO data presented in 2009 show no Lorentz
violating signal at the second harmonic of the Earth's sidereal frequency. This
sets a limit on a possible change in refractine index, dn/n < 2x10e-22, an
improvement of more than three orders of magnitude over existing limits.
| [
{
"created": "Wed, 10 Aug 2016 19:27:23 GMT",
"version": "v1"
}
] | 2016-08-12 | [
[
"Melissinos",
"Adrian",
""
]
] | Currently operating gravitational-wave interferometers are Michelson interferometers with effective arm length L ~ 4x10e5 m. While the interferometer remains in lock, data at the fsr sideband frequency encode information on slow phase changes in the f ~ 10e-5 Hz range, with a fringe sensitivity ~ 10e-10. Preliminary LIGO data presented in 2009 show no Lorentz violating signal at the second harmonic of the Earth's sidereal frequency. This sets a limit on a possible change in refractine index, dn/n < 2x10e-22, an improvement of more than three orders of magnitude over existing limits. |
1105.4434 | Carlos A. R. Herdeiro | P.P. Avelino, A.J.S. Hamilton, C.A.R. Herdeiro and M. Zilhao | Mass inflation in a D dimensional Reissner-Nordstrom black hole: a
hierarchy of particle accelerators ? | 8 pages, 6 figures | Phys.Rev.D84:024019,2011 | 10.1103/PhysRevD.84.024019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geometry inside the event horizon of perturbed D dimensional
Reissner-Nordstrom-(A)dS type black holes showing that, similarly to the four
dimensional case, mass inflation also occurs for D>4. First, using the
homogeneous approximation, we show that an increase of the number of spatial
dimensions contributes to a steeper variation of the metric coefficients with
the areal radius and that the phenomenon is insensitive to the cosmological
constant in leading order. Then, using the code reported in arXiv:0904.2669
[gr-qc] adapted to D dimensions, we perform fully non-linear numerical
simulations. We perturb the black hole with a compact pulse adapting the pulse
amplitude such that the relative variation of the black hole mass is the same
in all dimensions, and determine how the black hole interior evolves under the
perturbation. We qualitatively confirm that the phenomenon is similar to four
dimensions as well as the behaviour observed in the homogeneous approximation.
We speculate about the formation of black holes inside black holes triggered by
mass inflation, and about possible consequences of this scenario.
| [
{
"created": "Mon, 23 May 2011 08:41:30 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Avelino",
"P. P.",
""
],
[
"Hamilton",
"A. J. S.",
""
],
[
"Herdeiro",
"C. A. R.",
""
],
[
"Zilhao",
"M.",
""
]
] | We study the geometry inside the event horizon of perturbed D dimensional Reissner-Nordstrom-(A)dS type black holes showing that, similarly to the four dimensional case, mass inflation also occurs for D>4. First, using the homogeneous approximation, we show that an increase of the number of spatial dimensions contributes to a steeper variation of the metric coefficients with the areal radius and that the phenomenon is insensitive to the cosmological constant in leading order. Then, using the code reported in arXiv:0904.2669 [gr-qc] adapted to D dimensions, we perform fully non-linear numerical simulations. We perturb the black hole with a compact pulse adapting the pulse amplitude such that the relative variation of the black hole mass is the same in all dimensions, and determine how the black hole interior evolves under the perturbation. We qualitatively confirm that the phenomenon is similar to four dimensions as well as the behaviour observed in the homogeneous approximation. We speculate about the formation of black holes inside black holes triggered by mass inflation, and about possible consequences of this scenario. |
1803.01204 | Rafael Bernar | Rafael P. Bernar, Lu\'is C. B. Crispino, Atsushi Higuchi | The Gibbons-Hawking radiation of gravitons in the Poincar\'e and static
patches of de Sitter spacetime | 10 pages, no figures. Accepted for publication in Physical Review D | Phys. Rev. D 97, 085005 (2018) | 10.1103/PhysRevD.97.085005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the quantization of linearized gravity in the background de Sitter
spacetime using a gauge-invariant formalism to write the perturbed
gravitational field in the static patch. This field is quantized after fixing
the gauge completely. The response rate of this field to monochromatic
multipole sources is then computed in the thermal equilibrium state with the
well known Gibbons-Hawking temperature. We compare this response rate with the
one obtained in the Bunch-Davies-like vacuum state defined in the Poincar\'e
patch. These response rates are found to be the same as expected. This
agreement serves as a verification of the infrared finite graviton two-point
function in the static patch of de Sitter spacetime found previously.
| [
{
"created": "Sat, 3 Mar 2018 17:21:27 GMT",
"version": "v1"
}
] | 2018-04-11 | [
[
"Bernar",
"Rafael P.",
""
],
[
"Crispino",
"Luís C. B.",
""
],
[
"Higuchi",
"Atsushi",
""
]
] | We discuss the quantization of linearized gravity in the background de Sitter spacetime using a gauge-invariant formalism to write the perturbed gravitational field in the static patch. This field is quantized after fixing the gauge completely. The response rate of this field to monochromatic multipole sources is then computed in the thermal equilibrium state with the well known Gibbons-Hawking temperature. We compare this response rate with the one obtained in the Bunch-Davies-like vacuum state defined in the Poincar\'e patch. These response rates are found to be the same as expected. This agreement serves as a verification of the infrared finite graviton two-point function in the static patch of de Sitter spacetime found previously. |
2112.11676 | Rubab Manzoor | Rubab Manzoor and Wasee Shahid | Evolution of Cluster of Stars in f(R) Gravity | null | Physics of the Dark Universe: Volume 33, September 2021, 100844 | 10.1016/j.dark.2021.100844 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper explores the dynamics of evolving cluster of stars in the
presences of exotic matter. The $f(R)$ theory is used to presume exotic terms
for evolution scenario. We use structure scalars as evolution parameters to
explore dynamics of spherically symmetric distribution of evolving cluster of
stars. We consider Starobinsky model, $f(R)=R+\epsilon R^2$ and study different
evolution modes having features like isotropic pressure, density homogeneity,
homologous and geodesic behavior. It is concluded that dynamics of these modes
of evolution depends upon the behavior of dark matter. The presences of dark
matter directly affects the features of cluster like anisotropic pressure,
dissipation, expansion, shear as well as density homogeneity. The evolution
having homogeneous density and isotropic pressure depends upon conformally flat
and non-dissipative behavior of baryonic as well as non baryonic matter. The
dissipation factor induces density inhomogeneity in the expanding clusters
having shear effects. The non dissipative homologous evolution also be
discussed in the presence and absence of shear effects. It is found that high
curvature geometry in the presence of shear supports homologous evolution.
Expanding clusters are also explored in the presences of dissipation of dark
matter and shear effects. By using quasi-homologous conditions the geodesic
evolution is studied. It is theoretically showed that geodesic and homologous
conditions depends upon each other. Finally we investigate behavior of
Starobinsky model for a stellar structure $4U 1820-30$ toward center. It is
found that for increasing values of $\epsilon$ the DM behavior is dominant as
compare to baryonic matter.
| [
{
"created": "Wed, 22 Dec 2021 05:55:56 GMT",
"version": "v1"
}
] | 2021-12-23 | [
[
"Manzoor",
"Rubab",
""
],
[
"Shahid",
"Wasee",
""
]
] | This paper explores the dynamics of evolving cluster of stars in the presences of exotic matter. The $f(R)$ theory is used to presume exotic terms for evolution scenario. We use structure scalars as evolution parameters to explore dynamics of spherically symmetric distribution of evolving cluster of stars. We consider Starobinsky model, $f(R)=R+\epsilon R^2$ and study different evolution modes having features like isotropic pressure, density homogeneity, homologous and geodesic behavior. It is concluded that dynamics of these modes of evolution depends upon the behavior of dark matter. The presences of dark matter directly affects the features of cluster like anisotropic pressure, dissipation, expansion, shear as well as density homogeneity. The evolution having homogeneous density and isotropic pressure depends upon conformally flat and non-dissipative behavior of baryonic as well as non baryonic matter. The dissipation factor induces density inhomogeneity in the expanding clusters having shear effects. The non dissipative homologous evolution also be discussed in the presence and absence of shear effects. It is found that high curvature geometry in the presence of shear supports homologous evolution. Expanding clusters are also explored in the presences of dissipation of dark matter and shear effects. By using quasi-homologous conditions the geodesic evolution is studied. It is theoretically showed that geodesic and homologous conditions depends upon each other. Finally we investigate behavior of Starobinsky model for a stellar structure $4U 1820-30$ toward center. It is found that for increasing values of $\epsilon$ the DM behavior is dominant as compare to baryonic matter. |
1907.09902 | Hossein Mohseni Sadjadi | H. Mohseni Sadjadi and M. Khodaei | Regular scalar field around reflecting stars and black holes, and
reflecting star polarization | 14 pages, references updated | J. Cosmol. Astropart. Phys. 12 , 005 (2019) | 10.1088/1475-7516/2019/12/005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of a regular non-trivial scalar field in the background of an
asymptotically flat static reflecting star is discussed. The scalar field is
assumed to be conformally coupled to the outside matter. The induced scalar
charge is determined and the required conditions to have regular field are
obtained. The results are compared with the case of a black hole. Conditions to
have regular non-trivial scalar field out of the black hole horizon are
investigated. We show that in the presence of a scalar source, in contrast to
the black holes, the reflecting star becomes polarized.
| [
{
"created": "Mon, 15 Jul 2019 12:20:25 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Aug 2019 08:10:09 GMT",
"version": "v2"
},
{
"created": "Tue, 3 Dec 2019 14:20:58 GMT",
"version": "v3"
},
{
"created": "Sat, 7 Dec 2019 19:39:01 GMT",
"version": "v4"
}
] | 2020-10-02 | [
[
"Sadjadi",
"H. Mohseni",
""
],
[
"Khodaei",
"M.",
""
]
] | The existence of a regular non-trivial scalar field in the background of an asymptotically flat static reflecting star is discussed. The scalar field is assumed to be conformally coupled to the outside matter. The induced scalar charge is determined and the required conditions to have regular field are obtained. The results are compared with the case of a black hole. Conditions to have regular non-trivial scalar field out of the black hole horizon are investigated. We show that in the presence of a scalar source, in contrast to the black holes, the reflecting star becomes polarized. |
1007.1662 | Pierre-Philippe Dechant | Pierre-Philippe Dechant and Anthony N. Lasenby and Michael P. Hobson | Cracking the Taub-NUT | 39 pages, 15 figures, accepted by Classical and Quantum Gravity | Class.Quant.Grav.27:185010,2010 | 10.1088/0264-9381/27/18/185010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present further analysis of an anisotropic, non-singular early universe
model that leads to the viable cosmology presented in Dechant et al
(arXiv:0809.4335). Although this model (the DLH model) contains scalar field
matter, it is reminiscent of the Taub-NUT vacuum solution in that it has
biaxial Bianchi IX geometry and its evolution exhibits a dimensionality
reduction at a quasi-regular singularity that one can identify with the
big-bang. We show that the DLH and Taub-NUT metrics are related by a coordinate
transformation, in which the DLH time coordinate plays the role of conformal
time for Taub-NUT. Since both models continue through the big-bang, the
coordinate transformation can become multivalued. In particular, in mapping
from DLH to Taub-NUT, the Taub-NUT time can take only positive values. We
present explicit maps between the DLH and Taub-NUT models, with and without a
scalar field. In the vacuum DLH model, we find a periodic solution expressible
in terms of elliptic integrals. Mapping the vacuum solution over to Taub-NUT
coordinates, recovers the standard (non-periodic) Taub-NUT solution in the Taub
region, where Taub-NUT time takes positive values, but does not exhibit the two
NUT regions known in the standard Taub-NUT solution. Conversely, mapping the
complete Taub-NUT solution to the DLH case reveals that the NUT regions
correspond to imaginary time and space in DLH coordinates. We show that many of
the well-known `pathologies' of the Taub-NUT solution arise because the
traditional coordinates are connected by a multivalued transformation to the
physically more meaningful DLH coordinates. In particular, the
`open-to-closed-to-open' transition and the Taub and NUT regions of the
(Lorentzian) Taub-NUT model are replaced by a closed pancaking universe with
spacelike homogeneous sections at all times.
| [
{
"created": "Fri, 9 Jul 2010 20:04:55 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Dechant",
"Pierre-Philippe",
""
],
[
"Lasenby",
"Anthony N.",
""
],
[
"Hobson",
"Michael P.",
""
]
] | We present further analysis of an anisotropic, non-singular early universe model that leads to the viable cosmology presented in Dechant et al (arXiv:0809.4335). Although this model (the DLH model) contains scalar field matter, it is reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasi-regular singularity that one can identify with the big-bang. We show that the DLH and Taub-NUT metrics are related by a coordinate transformation, in which the DLH time coordinate plays the role of conformal time for Taub-NUT. Since both models continue through the big-bang, the coordinate transformation can become multivalued. In particular, in mapping from DLH to Taub-NUT, the Taub-NUT time can take only positive values. We present explicit maps between the DLH and Taub-NUT models, with and without a scalar field. In the vacuum DLH model, we find a periodic solution expressible in terms of elliptic integrals. Mapping the vacuum solution over to Taub-NUT coordinates, recovers the standard (non-periodic) Taub-NUT solution in the Taub region, where Taub-NUT time takes positive values, but does not exhibit the two NUT regions known in the standard Taub-NUT solution. Conversely, mapping the complete Taub-NUT solution to the DLH case reveals that the NUT regions correspond to imaginary time and space in DLH coordinates. We show that many of the well-known `pathologies' of the Taub-NUT solution arise because the traditional coordinates are connected by a multivalued transformation to the physically more meaningful DLH coordinates. In particular, the `open-to-closed-to-open' transition and the Taub and NUT regions of the (Lorentzian) Taub-NUT model are replaced by a closed pancaking universe with spacelike homogeneous sections at all times. |
0911.5051 | Christian R\"over | Christian R\"over | Random template placement and prior information | Proceedings of the 8th Edoardo Amaldi Conference on Gravitational
Waves. 7 pages, 4 figures | J.Phys.Conf.Ser.228:012008,2010 | 10.1088/1742-6596/228/1/012008 | AEI-2009-115 | gr-qc physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In signal detection problems, one is usually faced with the task of searching
a parameter space for peaks in the likelihood function which indicate the
presence of a signal. Random searches have proven to be very efficient as well
as easy to implement, compared e.g. to searches along regular grids in
parameter space. Knowledge of the parameterised shape of the signal searched
for adds structure to the parameter space, i.e., there are usually regions
requiring to be densely searched while in other regions a coarser search is
sufficient. On the other hand, prior information identifies the regions in
which a search will actually be promising or may likely be in vain. Defining
specific figures of merit allows one to combine both template metric and prior
distribution and devise optimal sampling schemes over the parameter space. We
show an example related to the gravitational wave signal from a binary inspiral
event. Here the template metric and prior information are particularly
contradictory, since signals from low-mass systems tolerate the least mismatch
in parameter space while high-mass systems are far more likely, as they imply a
greater signal-to-noise ratio (SNR) and hence are detectable to greater
distances. The derived sampling strategy is implemented in a Markov chain Monte
Carlo (MCMC) algorithm where it improves convergence.
| [
{
"created": "Thu, 26 Nov 2009 10:46:07 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Dec 2009 19:29:23 GMT",
"version": "v2"
}
] | 2010-10-08 | [
[
"Röver",
"Christian",
""
]
] | In signal detection problems, one is usually faced with the task of searching a parameter space for peaks in the likelihood function which indicate the presence of a signal. Random searches have proven to be very efficient as well as easy to implement, compared e.g. to searches along regular grids in parameter space. Knowledge of the parameterised shape of the signal searched for adds structure to the parameter space, i.e., there are usually regions requiring to be densely searched while in other regions a coarser search is sufficient. On the other hand, prior information identifies the regions in which a search will actually be promising or may likely be in vain. Defining specific figures of merit allows one to combine both template metric and prior distribution and devise optimal sampling schemes over the parameter space. We show an example related to the gravitational wave signal from a binary inspiral event. Here the template metric and prior information are particularly contradictory, since signals from low-mass systems tolerate the least mismatch in parameter space while high-mass systems are far more likely, as they imply a greater signal-to-noise ratio (SNR) and hence are detectable to greater distances. The derived sampling strategy is implemented in a Markov chain Monte Carlo (MCMC) algorithm where it improves convergence. |
0808.1083 | Robert T. Jantzen | Donato Bini, Robert T. Jantzen, Luigi Stella | The general relativistic Poynting-Robertson effect | 19 pages iop style, 8 eps figure files for 5 figures | Class.Quant.Grav.26:055009,2009 | 10.1088/0264-9381/26/5/055009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general relativistic version is developed for Robertson's discussion of
the Poynting-Robertson effect that he based on special relativity and Newtonian
gravity for point radiation sources like stars. The general relativistic model
uses a test radiation field of photons in outward radial motion with zero
angular momentum in the equatorial plane of the exterior Schwarzschild or Kerr
spacetime.
| [
{
"created": "Thu, 7 Aug 2008 18:00:36 GMT",
"version": "v1"
}
] | 2009-02-20 | [
[
"Bini",
"Donato",
""
],
[
"Jantzen",
"Robert T.",
""
],
[
"Stella",
"Luigi",
""
]
] | The general relativistic version is developed for Robertson's discussion of the Poynting-Robertson effect that he based on special relativity and Newtonian gravity for point radiation sources like stars. The general relativistic model uses a test radiation field of photons in outward radial motion with zero angular momentum in the equatorial plane of the exterior Schwarzschild or Kerr spacetime. |
1403.7559 | Marcello Ortaggio | Marcello Ortaggio and Alena Pravdov\'a | Asymptotic behaviour of the Weyl tensor in higher dimensions | 32 pages. v2: added refs., corrected ref. [2] and a few typos (but
equations unchanged), added 2 summarizing tables, minor changes to match the
published version | Phys. Rev. D. 90, 104011 (2014) | 10.1103/PhysRevD.90.104011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the leading order fall-off behaviour of the Weyl tensor in
higher dimensional Einstein spacetimes (with and without a cosmological
constant) as one approaches infinity along a congruence of null geodesics. The
null congruence is assumed to "expand" in all directions near infinity (but it
is otherwise generic), which includes in particular asymptotically flat
spacetimes. In contrast to the well-known four-dimensional peeling property,
the fall-off rate of various Weyl components depends substantially on the
chosen boundary conditions, and is also influenced by the presence of a
cosmological constant. The leading component is always algebraically special,
but in various cases it can be of type N, III or II.
| [
{
"created": "Fri, 28 Mar 2014 22:26:26 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Nov 2014 10:35:12 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Ortaggio",
"Marcello",
""
],
[
"Pravdová",
"Alena",
""
]
] | We determine the leading order fall-off behaviour of the Weyl tensor in higher dimensional Einstein spacetimes (with and without a cosmological constant) as one approaches infinity along a congruence of null geodesics. The null congruence is assumed to "expand" in all directions near infinity (but it is otherwise generic), which includes in particular asymptotically flat spacetimes. In contrast to the well-known four-dimensional peeling property, the fall-off rate of various Weyl components depends substantially on the chosen boundary conditions, and is also influenced by the presence of a cosmological constant. The leading component is always algebraically special, but in various cases it can be of type N, III or II. |
1008.3670 | Joshua C. Long | D. Bennett, V. Skavysh, and J. Long | Search for Lorentz Violation in a Short-Range Gravity Experiment | Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 2010 | null | 10.1142/9789814327688_0051 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An experimental test of the Newtonian inverse square law at short range has
been used to set limits on Lorentz violation in the pure gravity sector of the
Standard-Model Extension. On account of the planar test mass geometry,
nominally null with respect to inverse square forces, the limits derived for
the SME coefficients of Lorentz violation are on the order s ~ 10000.
| [
{
"created": "Sun, 22 Aug 2010 00:01:52 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Bennett",
"D.",
""
],
[
"Skavysh",
"V.",
""
],
[
"Long",
"J.",
""
]
] | An experimental test of the Newtonian inverse square law at short range has been used to set limits on Lorentz violation in the pure gravity sector of the Standard-Model Extension. On account of the planar test mass geometry, nominally null with respect to inverse square forces, the limits derived for the SME coefficients of Lorentz violation are on the order s ~ 10000. |
2406.11564 | Carlos O. Lousto | Alessandro Ciarfella, James Healy, Carlos O. Lousto and Hiroyuki
Nakano | Quasicircular Orbital Parameters for Numerical Relativity Revisited | 13 pages, 4 figures, 3 tables | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the post-Newtonian (PN) expansion, we extend the determination of
quasicircular orbital parameters to be used by subsequent full numerical
simulations to the 3.5PN order, and find that this leads to lower
eccentricities, $e$, than with our previous method that used up to 3PN order.
We also supplement the computation of the radial infall due to radiation
reaction and the location of the center of mass to 3.5PN order, providing
explicit formulas. In addition, we consider the small mass ratio limit by
explicitly including the Schwarzschild and Kerr limits, the later in
quasi-isotropic as well as in our standard use of ADMTT coordinates. We evolve
binaries with a $q=1/16$ mass ratio by using 3PN, 3.5PN, 3.5PN+Schwarzschild,
3.5PN+KerrQISO and 3.5PN+KerrADMTT quasicircular data for three different
configurations where the larger hole intrinsic spins are $\chi^z=-0.8$, $-0.4$
and $+0.8$. Using different measures of eccentricity from the black hole
trajectories and from the waveform amplitudes and phases, we determine a
systematic reduction of eccentricities with respect to the 3PN initial values
by factors of up to an order of magnitude, and reaching the desired
$e\sim10^{-3}$ threshold.
| [
{
"created": "Mon, 17 Jun 2024 14:02:00 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Ciarfella",
"Alessandro",
""
],
[
"Healy",
"James",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Nakano",
"Hiroyuki",
""
]
] | In the post-Newtonian (PN) expansion, we extend the determination of quasicircular orbital parameters to be used by subsequent full numerical simulations to the 3.5PN order, and find that this leads to lower eccentricities, $e$, than with our previous method that used up to 3PN order. We also supplement the computation of the radial infall due to radiation reaction and the location of the center of mass to 3.5PN order, providing explicit formulas. In addition, we consider the small mass ratio limit by explicitly including the Schwarzschild and Kerr limits, the later in quasi-isotropic as well as in our standard use of ADMTT coordinates. We evolve binaries with a $q=1/16$ mass ratio by using 3PN, 3.5PN, 3.5PN+Schwarzschild, 3.5PN+KerrQISO and 3.5PN+KerrADMTT quasicircular data for three different configurations where the larger hole intrinsic spins are $\chi^z=-0.8$, $-0.4$ and $+0.8$. Using different measures of eccentricity from the black hole trajectories and from the waveform amplitudes and phases, we determine a systematic reduction of eccentricities with respect to the 3PN initial values by factors of up to an order of magnitude, and reaching the desired $e\sim10^{-3}$ threshold. |
0906.1551 | Yu-Huei Wu | Yu-Huei Wu and Chih-Hung Wang | Gravitational radiations of generic isolated horizons and non-rotating
dynamical horizons from asymptotic expansions | PRD, 15 pages | Phys.Rev.D80:063002,2009 | 10.1103/PhysRevD.80.063002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Instead of using a three dimensional analysis on quasi-local horizons, we
adopt a four dimensional asymptotic expansion analysis to study the next order
contributions from the nonlinearity of general relativity. From the similarity
between null infinity and horizons, the proper reference frames are chosen from
the compatible constant spinors for an observer to measure the energy-momentum
and flux near quasi-local horizons. In particular, we focus on the similarity
of Bondi-Sachs gravitational radiation for the quasi-local horizons and compare
our results to Ashtekar-Kirshnan flux formular. The quasi-local energy momentum
and flux of generic isolated horizons and non-rotating dynamical horizons are
discussed in this paper.
| [
{
"created": "Mon, 8 Jun 2009 18:07:46 GMT",
"version": "v1"
}
] | 2009-10-02 | [
[
"Wu",
"Yu-Huei",
""
],
[
"Wang",
"Chih-Hung",
""
]
] | Instead of using a three dimensional analysis on quasi-local horizons, we adopt a four dimensional asymptotic expansion analysis to study the next order contributions from the nonlinearity of general relativity. From the similarity between null infinity and horizons, the proper reference frames are chosen from the compatible constant spinors for an observer to measure the energy-momentum and flux near quasi-local horizons. In particular, we focus on the similarity of Bondi-Sachs gravitational radiation for the quasi-local horizons and compare our results to Ashtekar-Kirshnan flux formular. The quasi-local energy momentum and flux of generic isolated horizons and non-rotating dynamical horizons are discussed in this paper. |
1912.12359 | Riccardo Sturani | Luc Blanchet, Stefano Foffa, Fran\c{c}ois Larrouturou, Riccardo
Sturani | Logarithmic tail contributions to the energy function of circular
compact binaries | 17 pages, 1 figure. 2 paragraphs added to sec. IV A in v2 | Phys. Rev. D 101, 084045 (2020) | 10.1103/PhysRevD.101.084045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We combine different techniques to extract information about the logarithmic
contributions to the two-body conservative dynamics within the post-Newtonian
(PN) approximation of General Relativity. The logarithms come from the
conservative part of non linear gravitational-wave tails and their iterations.
Explicit, original expressions are found for conservative dynamics logarithmic
tail terms up to 6PN order by adopting both traditional PN calculations and
effective field theory (EFT) methods. We also determine all logarithmic terms
at 7PN order, fixing a sub-leading logarithm from a tail-of-tail-of-tail
process by comparison with self-force (SF) results. Moreover, we use
renormalization group techniques to obtain the leading logarithmic terms to
generic power $n$, appearing at $(3n+1)$PN order, and we resum the infinite
series in a closed form. Half-integer PN orders enter the conservative dynamics
starting at 5.5PN, but they do not generate logarithmic contributions up to
next-to-next-to-leading order included. We nevertheless present their
contribution at leading order in the small mass ratio limit.
| [
{
"created": "Fri, 27 Dec 2019 22:53:39 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jul 2020 02:57:33 GMT",
"version": "v2"
}
] | 2020-07-09 | [
[
"Blanchet",
"Luc",
""
],
[
"Foffa",
"Stefano",
""
],
[
"Larrouturou",
"François",
""
],
[
"Sturani",
"Riccardo",
""
]
] | We combine different techniques to extract information about the logarithmic contributions to the two-body conservative dynamics within the post-Newtonian (PN) approximation of General Relativity. The logarithms come from the conservative part of non linear gravitational-wave tails and their iterations. Explicit, original expressions are found for conservative dynamics logarithmic tail terms up to 6PN order by adopting both traditional PN calculations and effective field theory (EFT) methods. We also determine all logarithmic terms at 7PN order, fixing a sub-leading logarithm from a tail-of-tail-of-tail process by comparison with self-force (SF) results. Moreover, we use renormalization group techniques to obtain the leading logarithmic terms to generic power $n$, appearing at $(3n+1)$PN order, and we resum the infinite series in a closed form. Half-integer PN orders enter the conservative dynamics starting at 5.5PN, but they do not generate logarithmic contributions up to next-to-next-to-leading order included. We nevertheless present their contribution at leading order in the small mass ratio limit. |
2310.06492 | Anisur Rahaman | Sohan Kumar Jha, Anisur Rahaman | Study of quasinormal modes, greybody bounds, and sparsity of Hawking
radiation within the metric-affine bumblebee gravity framework | 14 pages latex with 10 figures, few new amendment | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a static and spherically symmetric black hole metric that emerges
from the vacuum solution of the traceless metric-affine bumblebee model. Our
study focuses on the possible implications of the modifications induced by the
model on various astrophysical observables that include quasinormal modes,
ringdown waveforms, Hawking radiation spectrum, sparsity of that radiation, and
the lifetime of a black hole. We explore the impact of the Lorentz
symmetry-breaking parameter $\alpha$ on the quasinormal modes with the help of
the $6th$-order WKB method. Our inquisition reveals that the emission frequency
and decay rate initially decrease with $\alpha$ and then grow up. As a result,
the LSB becomes critically important for maintaining the stability of the
system after being exposed to perturbation. The convergence of the WKB method
for various orders is also studied here. We then analyze the Hawking
temperature, radiation spectrum, and sparsity in this modified gravity
framework that provides valuable insights into the thermal radiation emitted by
black holes. It points out that the Hawking temperature, the peak of the power
spectrum, and the total power emitted initially decreases and then increases
with $\alpha$. However, The variation of the sparsity with $\alpha$ follows a
reverse trend. Finally, we obtain the analytical expression of the 'lifetime'
of black holes and scrutinize the effect of $\alpha$ on it.
| [
{
"created": "Tue, 10 Oct 2023 10:02:19 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Feb 2024 17:28:23 GMT",
"version": "v2"
}
] | 2024-02-05 | [
[
"Jha",
"Sohan Kumar",
""
],
[
"Rahaman",
"Anisur",
""
]
] | We consider a static and spherically symmetric black hole metric that emerges from the vacuum solution of the traceless metric-affine bumblebee model. Our study focuses on the possible implications of the modifications induced by the model on various astrophysical observables that include quasinormal modes, ringdown waveforms, Hawking radiation spectrum, sparsity of that radiation, and the lifetime of a black hole. We explore the impact of the Lorentz symmetry-breaking parameter $\alpha$ on the quasinormal modes with the help of the $6th$-order WKB method. Our inquisition reveals that the emission frequency and decay rate initially decrease with $\alpha$ and then grow up. As a result, the LSB becomes critically important for maintaining the stability of the system after being exposed to perturbation. The convergence of the WKB method for various orders is also studied here. We then analyze the Hawking temperature, radiation spectrum, and sparsity in this modified gravity framework that provides valuable insights into the thermal radiation emitted by black holes. It points out that the Hawking temperature, the peak of the power spectrum, and the total power emitted initially decreases and then increases with $\alpha$. However, The variation of the sparsity with $\alpha$ follows a reverse trend. Finally, we obtain the analytical expression of the 'lifetime' of black holes and scrutinize the effect of $\alpha$ on it. |
2310.00884 | Ryuya Kudo | Kaisei Takahashi, Ryuya Kudo, Keita Takizawa, Hideki Asada | Equivalence between definitions of the gravitational deflection angle of
light for a stationary spacetime | 4 pages, 1 figure, text improved, accepted for PRD | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Gibbons-Werner-Ono-Ishihara-Asada method for gravitational lensing in a
stationary spacetime has been recently reexamined [Huang and Cao,
arXiv:2306.04145], in which the gravitational deflection angle of light based
on the Gauss-Bonnet theorem can be rewritten as a line integral of two
functions $H$ and $T$. The present paper proves that the Huang-Cao line
integral definition and the Ono-Ishihara-Asada one [Phys. Rev. D 96, 104037
(2017)] are equivalent to each other, whatever asymptotic regions are. A remark
is also made concerning the direction of a light ray in a practical use of
these definitions.
| [
{
"created": "Mon, 2 Oct 2023 04:00:27 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Nov 2023 06:03:25 GMT",
"version": "v2"
}
] | 2023-11-20 | [
[
"Takahashi",
"Kaisei",
""
],
[
"Kudo",
"Ryuya",
""
],
[
"Takizawa",
"Keita",
""
],
[
"Asada",
"Hideki",
""
]
] | The Gibbons-Werner-Ono-Ishihara-Asada method for gravitational lensing in a stationary spacetime has been recently reexamined [Huang and Cao, arXiv:2306.04145], in which the gravitational deflection angle of light based on the Gauss-Bonnet theorem can be rewritten as a line integral of two functions $H$ and $T$. The present paper proves that the Huang-Cao line integral definition and the Ono-Ishihara-Asada one [Phys. Rev. D 96, 104037 (2017)] are equivalent to each other, whatever asymptotic regions are. A remark is also made concerning the direction of a light ray in a practical use of these definitions. |
1103.1597 | Muxin Han | You Ding, Muxin Han | On the Asymptotics of Quantum Group Spinfoam Model | 25 pages, 1 figure | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently a quantum group deformation of EPRL spinfoam model was proposed in
arXiv:1012.4216 by one of the authors, and in arXiv:1012.4784 by Fairbairn and
Meusburger. It is interesting to study the high spin asymptotics of the quantum
group spinfoam model, to see if it gives the discrete Einstein gravity with
cosmological constant as its semiclassical limit. In this article we propose a
new technique, which can simplify the analysis of the high spin asymptotics for
quantum group spinfoam vertex amplitude. This technique can generalize the
spinfoam asymptotic analysis developed by Barrett, et al to quantum group
spinfoam. As a preparation of asymptotic analysis, we define and analyze the
coherent states and coherent intertwiners for quantum group, which has certain
"factorization properties". We show that in the high spin limit of quantum
group spinfoam, many q-deformed noncommutative ingredients become classical and
commutative. In particular, the squared norm of coherent intertwiner and the
(Euclidean) vertex amplitude become integrals on classical group, while there
are some additional terms (written in terms of classical group variables) make
quantum group corrections to the usual (classical group) coherent intertwiner
and vertex amplitude. These quantum group correction terms turn out to be
proportional to the deformation parameter, which hopefully gives the
cosmological term as its semiclassical limit.
| [
{
"created": "Tue, 8 Mar 2011 18:40:39 GMT",
"version": "v1"
}
] | 2011-03-09 | [
[
"Ding",
"You",
""
],
[
"Han",
"Muxin",
""
]
] | Recently a quantum group deformation of EPRL spinfoam model was proposed in arXiv:1012.4216 by one of the authors, and in arXiv:1012.4784 by Fairbairn and Meusburger. It is interesting to study the high spin asymptotics of the quantum group spinfoam model, to see if it gives the discrete Einstein gravity with cosmological constant as its semiclassical limit. In this article we propose a new technique, which can simplify the analysis of the high spin asymptotics for quantum group spinfoam vertex amplitude. This technique can generalize the spinfoam asymptotic analysis developed by Barrett, et al to quantum group spinfoam. As a preparation of asymptotic analysis, we define and analyze the coherent states and coherent intertwiners for quantum group, which has certain "factorization properties". We show that in the high spin limit of quantum group spinfoam, many q-deformed noncommutative ingredients become classical and commutative. In particular, the squared norm of coherent intertwiner and the (Euclidean) vertex amplitude become integrals on classical group, while there are some additional terms (written in terms of classical group variables) make quantum group corrections to the usual (classical group) coherent intertwiner and vertex amplitude. These quantum group correction terms turn out to be proportional to the deformation parameter, which hopefully gives the cosmological term as its semiclassical limit. |
1810.10657 | Mohammad Bagher Jahani Poshteh | Mohammad Bagher Jahani Poshteh, Robert B. Mann | Gravitational Lensing by Black Holes in Einsteinian Cubic Gravity | This is the final version that appeared in Phys. Rev. D | Phys. Rev. D 99, 024035 (2019) | 10.1103/PhysRevD.99.024035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the predictions of Einsteinian Cubic Gravity (ECG) for the
lensing effects due to supermassive black holes at the center of Milky Way and
other galaxies. Working in the context of spherical symmetry, we obtain the
metric function from a continued fraction method and find that both time delays
and the angular positions of images considerably deviate from general
relativity, as large as milliarcseconds. This suggests that observational tests
of ECG are indeed feasible.
| [
{
"created": "Thu, 25 Oct 2018 00:03:43 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jan 2019 15:54:11 GMT",
"version": "v2"
}
] | 2019-02-01 | [
[
"Poshteh",
"Mohammad Bagher Jahani",
""
],
[
"Mann",
"Robert B.",
""
]
] | We investigate the predictions of Einsteinian Cubic Gravity (ECG) for the lensing effects due to supermassive black holes at the center of Milky Way and other galaxies. Working in the context of spherical symmetry, we obtain the metric function from a continued fraction method and find that both time delays and the angular positions of images considerably deviate from general relativity, as large as milliarcseconds. This suggests that observational tests of ECG are indeed feasible. |
1809.00259 | Shammi Tahura | Sharaban Tahura and Kent Yagi | Parameterized Post-Einsteinian Gravitational Waveforms in Various
Modified Theories of Gravity | 20 pages, 2 tables; v2: matches published version, updated abstract,
updated references; v3: PPE parameters in dCS gravity corrected | Phys. Rev. D 98, 084042 (2018) | 10.1103/PhysRevD.98.084042 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite the tremendous success of general relativity so far, modified
theories of gravity have received increased attention lately, motivated from
both theoretical and observational aspects. Gravitational wave observations
opened new possibilities for testing the viability of such theories in the
strong-field regime. One could test each theory against observed data one at a
time, though a more efficient approach would be to first probe gravity in a
theory-agnostic way and map such information to that on specific theories
afterward. One example of such model-independent tests with gravitational waves
is the parameterized post-Einsteinian formalism, where one introduces generic
parameters in the amplitude and phase that capture non-Einsteinian effects. In
this paper, we derive gravitational waveforms from inspiraling compact binaries
in various modified theories of gravity that violate at least one fundamental
pillar in general relativity. We achieve this by deriving relations between
corrections to the waveform amplitude/phase and those to the frequency
evolution and Kepler's third law, since the latter two have already been (or
can easily be) derived in many theories. Such an analysis allows us to derive
corrections to the waveform amplitude, which extends many of previous works
that focused on phase corrections only. Moreover, we derive gravitational
waveforms in theories with varying gravitational constant. We extend the
previous work by introducing two gravitational constants (the conservative one
entering in the binding energy and the dissipative one entering in the
gravitational wave luminosity) and allowing masses of binary constituents to
vary with time. We also correct some errors in previous literature. Our results
can be used to improve current analyses of testing general relativity as well
as to achieve new projected constraints on many modified theories of gravity.
| [
{
"created": "Sat, 1 Sep 2018 22:15:25 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 04:56:41 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Dec 2019 22:32:11 GMT",
"version": "v3"
}
] | 2020-01-01 | [
[
"Tahura",
"Sharaban",
""
],
[
"Yagi",
"Kent",
""
]
] | Despite the tremendous success of general relativity so far, modified theories of gravity have received increased attention lately, motivated from both theoretical and observational aspects. Gravitational wave observations opened new possibilities for testing the viability of such theories in the strong-field regime. One could test each theory against observed data one at a time, though a more efficient approach would be to first probe gravity in a theory-agnostic way and map such information to that on specific theories afterward. One example of such model-independent tests with gravitational waves is the parameterized post-Einsteinian formalism, where one introduces generic parameters in the amplitude and phase that capture non-Einsteinian effects. In this paper, we derive gravitational waveforms from inspiraling compact binaries in various modified theories of gravity that violate at least one fundamental pillar in general relativity. We achieve this by deriving relations between corrections to the waveform amplitude/phase and those to the frequency evolution and Kepler's third law, since the latter two have already been (or can easily be) derived in many theories. Such an analysis allows us to derive corrections to the waveform amplitude, which extends many of previous works that focused on phase corrections only. Moreover, we derive gravitational waveforms in theories with varying gravitational constant. We extend the previous work by introducing two gravitational constants (the conservative one entering in the binding energy and the dissipative one entering in the gravitational wave luminosity) and allowing masses of binary constituents to vary with time. We also correct some errors in previous literature. Our results can be used to improve current analyses of testing general relativity as well as to achieve new projected constraints on many modified theories of gravity. |
1707.08414 | Akira Matsumura | Akira Matsumura, Yasusada Nambu | Large scale quantum entanglement in de Sitter spacetime | 20 pages, 11 figures | Phys. Rev. D 98, 025004 (2018) | 10.1103/PhysRevD.98.025004 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate quantum entanglement between two symmetric spatialregions in
de Sitter space with the Bunch-Davies vacuum. As a discretized model of the
scalar field for numerical simulation, we consider a harmonic chain model.
Using the coarse-grained variables for the scalar field, it is shown that the
multipartite entanglement on the superhorizon scale exists by checking the
monogamy relation for the negativity which quantifies the entanglement between
the two regions. Further, we consider the continuous limit of this model
without coarse-graining and find that non-zero values of the logarithmic
negativity exist even if the distance between two spatial regions is larger
than the Hubble horizon scale.
| [
{
"created": "Wed, 26 Jul 2017 12:55:22 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jul 2018 17:01:42 GMT",
"version": "v2"
}
] | 2018-07-12 | [
[
"Matsumura",
"Akira",
""
],
[
"Nambu",
"Yasusada",
""
]
] | We investigate quantum entanglement between two symmetric spatialregions in de Sitter space with the Bunch-Davies vacuum. As a discretized model of the scalar field for numerical simulation, we consider a harmonic chain model. Using the coarse-grained variables for the scalar field, it is shown that the multipartite entanglement on the superhorizon scale exists by checking the monogamy relation for the negativity which quantifies the entanglement between the two regions. Further, we consider the continuous limit of this model without coarse-graining and find that non-zero values of the logarithmic negativity exist even if the distance between two spatial regions is larger than the Hubble horizon scale. |
1902.09643 | Damianos Iosifidis | Damianos Iosifidis | Metric-Affine Gravity and Cosmology/Aspects of Torsion and non-Metricity
in Gravity Theories | PhD Thesis, 270 pages, 1 figure | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This Thesis is devoted to the study of Metric-Affine Theories of Gravity and
Applications to Cosmology. The thesis is organized as follows. In the first
Chapter we define the various geometrical quantities that characterize a
non-Riemannian geometry. In the second Chapter we explore the MAG model
building. In Chapter 3 we use a well known procedure to excite torsional
degrees of freedom by coupling surface terms to scalars. Then, in Chapter 4
which seems to be the most important Chapter of the thesis, at least with
regards to its use in applications, we present a step by step way to solve for
the affine connection in non-Riemannian geometries, for the first time in the
literature. A peculiar f(R) case is studied in Chapter 5. This is the
conformally (as well as projective invariant) invariant theory f(R)=a R^{2}
which contains an undetermined scalar degree of freedom. We then turn our
attention to Cosmology with torsion and non-metricity (Chapter 6). In Chapter
7, we formulate the necessary setup for the $1+3$ splitting of the generalized
spacetime. Having clarified the subtle points (that generally stem from
non-metricity) in the aforementioned formulation we carefully derive the
generalized Raychaudhuri equation in the presence of both torsion and
non-metricity (along with curvature). This, as it stands, is the most general
form of the Raychaudhuri equation that exists in the literature. We close this
Thesis by considering three possible scale transformations that one can
consider in Metric-Affine Geometry.
| [
{
"created": "Mon, 25 Feb 2019 22:26:53 GMT",
"version": "v1"
}
] | 2019-02-27 | [
[
"Iosifidis",
"Damianos",
""
]
] | This Thesis is devoted to the study of Metric-Affine Theories of Gravity and Applications to Cosmology. The thesis is organized as follows. In the first Chapter we define the various geometrical quantities that characterize a non-Riemannian geometry. In the second Chapter we explore the MAG model building. In Chapter 3 we use a well known procedure to excite torsional degrees of freedom by coupling surface terms to scalars. Then, in Chapter 4 which seems to be the most important Chapter of the thesis, at least with regards to its use in applications, we present a step by step way to solve for the affine connection in non-Riemannian geometries, for the first time in the literature. A peculiar f(R) case is studied in Chapter 5. This is the conformally (as well as projective invariant) invariant theory f(R)=a R^{2} which contains an undetermined scalar degree of freedom. We then turn our attention to Cosmology with torsion and non-metricity (Chapter 6). In Chapter 7, we formulate the necessary setup for the $1+3$ splitting of the generalized spacetime. Having clarified the subtle points (that generally stem from non-metricity) in the aforementioned formulation we carefully derive the generalized Raychaudhuri equation in the presence of both torsion and non-metricity (along with curvature). This, as it stands, is the most general form of the Raychaudhuri equation that exists in the literature. We close this Thesis by considering three possible scale transformations that one can consider in Metric-Affine Geometry. |
0904.4184 | Thomas M\"uller | Thomas Mueller, Frank Grave | Catalogue of Spacetimes | several new metrics added, introduction enhanced, Euler-Lagrangian
calculations added for some metrics | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Catalogue of Spacetimes is a collection of four-dimensional Lorentzian
spacetimes in the context of the General Theory of Relativity (GR). The aim of
the catalogue is to give a quick reference for students who need some basic
facts of the most well-known spacetimes in GR.
| [
{
"created": "Mon, 27 Apr 2009 15:40:14 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Nov 2009 16:43:32 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Nov 2010 15:19:57 GMT",
"version": "v3"
}
] | 2010-11-13 | [
[
"Mueller",
"Thomas",
""
],
[
"Grave",
"Frank",
""
]
] | The Catalogue of Spacetimes is a collection of four-dimensional Lorentzian spacetimes in the context of the General Theory of Relativity (GR). The aim of the catalogue is to give a quick reference for students who need some basic facts of the most well-known spacetimes in GR. |
2207.10096 | Johannes Noller | Ian Harry, Johannes Noller | Probing the speed of gravity with LVK, LISA, and joint observations | 12 pages + appendices and references, 5 figures; v3: minor
clarifications added, matches published version | GRG 54, 133 (2022) | 10.1007/s10714-022-03016-0 | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Theories of dark energy that affect the speed of gravitational waves $c_{\rm
GW}$ on cosmological scales naturally lead to a frequency-dependent transition
of that speed close to the LIGO/Virgo/KAGRA (LVK) band. While observations such
as GW170817 assure us that $c_{\rm GW}$ is extremely close to the speed of
light in the LVK band, a frequency-dependent transition below the LVK band is a
smoking-gun signal for large classes of dynamical dark energy theories. Here we
discuss 1) how the remnants of such a transition can be constrained with
observations in the LVK band, 2) what signatures are associated with such a
transition in the LISA band, and 3) how joint observations in the LVK and LISA
bands allow us to place tight constraints on this transition and the underlying
theories. We find that deviations of $c_{\rm GW}$ can be constrained down to a
level of $\sim 10^{-17}$ in the LVK ${\textit and}$ LISA bands even for mild
frequency-dependence, much stronger than existing bounds for
frequency-independent $c_{\rm GW} \neq c$. We use the strain data from GW170817
to bound the deviation of $c_{\rm GW}$ to be less than $10^{-17}$ at 100 Hz and
less than $10^{-18}$ at 500 Hz. We also identify a particularly interesting
type of transition in between the LVK and LISA bands and show how multi-band
observations can constrain this further. Finally, we discuss what these current
and forecasted constraints imply for the underlying dark energy theories.
| [
{
"created": "Wed, 20 Jul 2022 18:00:02 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2022 15:33:08 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Oct 2022 16:41:23 GMT",
"version": "v3"
}
] | 2022-10-27 | [
[
"Harry",
"Ian",
""
],
[
"Noller",
"Johannes",
""
]
] | Theories of dark energy that affect the speed of gravitational waves $c_{\rm GW}$ on cosmological scales naturally lead to a frequency-dependent transition of that speed close to the LIGO/Virgo/KAGRA (LVK) band. While observations such as GW170817 assure us that $c_{\rm GW}$ is extremely close to the speed of light in the LVK band, a frequency-dependent transition below the LVK band is a smoking-gun signal for large classes of dynamical dark energy theories. Here we discuss 1) how the remnants of such a transition can be constrained with observations in the LVK band, 2) what signatures are associated with such a transition in the LISA band, and 3) how joint observations in the LVK and LISA bands allow us to place tight constraints on this transition and the underlying theories. We find that deviations of $c_{\rm GW}$ can be constrained down to a level of $\sim 10^{-17}$ in the LVK ${\textit and}$ LISA bands even for mild frequency-dependence, much stronger than existing bounds for frequency-independent $c_{\rm GW} \neq c$. We use the strain data from GW170817 to bound the deviation of $c_{\rm GW}$ to be less than $10^{-17}$ at 100 Hz and less than $10^{-18}$ at 500 Hz. We also identify a particularly interesting type of transition in between the LVK and LISA bands and show how multi-band observations can constrain this further. Finally, we discuss what these current and forecasted constraints imply for the underlying dark energy theories. |
2102.10483 | Subham Roy Mr. | Avijit Mukherjee, Subham B Roy | Birkhoffs Theorem and Lie Symmetry Analysis | null | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Three dimensional space is said to be spherically symmetric if it admits
SO(3) as the group of isometries. Under this symmetry condition, the Einsteins
Field equations for vacuum, yields the Schwarzschild Metric as the unique
solution, which essentially is the statement of the well known Birkhoffs
Theorem. Geometrically speaking this theorem claims that the pseudo-Riemanian
space-times provide more isometries than expected from the original metric
holonomy/ansatz. In this paper we use the method of Lie Symmetry Analysis to
analyze the Einsteins Vacuum Field Equations so as to obtain the Symmetry
Generators of the corresponding Differential Equation. Additionally, applying
the Noether Point Symmetry method we have obtained the conserved quantities
corresponding to the generators of the Schwarzschild Lagrangian and paving way
to reformulate the Birkhoffs Theorem from a different approach.
| [
{
"created": "Sun, 21 Feb 2021 00:47:22 GMT",
"version": "v1"
}
] | 2021-02-23 | [
[
"Mukherjee",
"Avijit",
""
],
[
"Roy",
"Subham B",
""
]
] | Three dimensional space is said to be spherically symmetric if it admits SO(3) as the group of isometries. Under this symmetry condition, the Einsteins Field equations for vacuum, yields the Schwarzschild Metric as the unique solution, which essentially is the statement of the well known Birkhoffs Theorem. Geometrically speaking this theorem claims that the pseudo-Riemanian space-times provide more isometries than expected from the original metric holonomy/ansatz. In this paper we use the method of Lie Symmetry Analysis to analyze the Einsteins Vacuum Field Equations so as to obtain the Symmetry Generators of the corresponding Differential Equation. Additionally, applying the Noether Point Symmetry method we have obtained the conserved quantities corresponding to the generators of the Schwarzschild Lagrangian and paving way to reformulate the Birkhoffs Theorem from a different approach. |
gr-qc/0508082 | Fabrizio Canfora | F. Canfora | A note on Tachyon dynamics | 11 pages, no figures, to be published on Physics Letters B | Phys.Lett. B625 (2005) 277-284 | 10.1016/j.physletb.2005.08.063 | null | gr-qc hep-th | null | A suitable splitting of tachyon field equation is able to disclose non
trivial properties of Born-Infeld (some known, some unexpected) and Polyakov
actions; the tachyon equation also can be analyzed in some detail. The analysis
displays an intriguing connection between sine-Gordon theory and some crucial
issues such as the emergence of perturbative string states when a D-Brane and
an anti-D-Brane annihilate and the confinement of charged D-Branes.
| [
{
"created": "Sat, 20 Aug 2005 06:32:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Canfora",
"F.",
""
]
] | A suitable splitting of tachyon field equation is able to disclose non trivial properties of Born-Infeld (some known, some unexpected) and Polyakov actions; the tachyon equation also can be analyzed in some detail. The analysis displays an intriguing connection between sine-Gordon theory and some crucial issues such as the emergence of perturbative string states when a D-Brane and an anti-D-Brane annihilate and the confinement of charged D-Branes. |
1705.09047 | Chongoh Lee | Chong Oh Lee | Configurational entropy of charged AdS black holes | 6 pages, 4 figures, typos corrected, version to appear in PLB | null | 10.1016/j.physletb.2017.07.013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When we consider charged AdS black holes in higher dimensional spacetime and
a molecule number density along coexistence curves is numerically extended to
higher dimensional cases. It is found that a number density difference of a
small and large black holes decrease as a total dimension grows up. In
particular, we find that a configurational entropy is a concave function of a
reduced temperature and reaches a maximum value at a critical (second-order
phase transition) point. Furthermore, the bigger a total dimension becomes, the
more concave function in a configurational entropy while the more convex
function in a reduced pressure.
| [
{
"created": "Thu, 25 May 2017 05:05:10 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Jul 2017 07:29:21 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Lee",
"Chong Oh",
""
]
] | When we consider charged AdS black holes in higher dimensional spacetime and a molecule number density along coexistence curves is numerically extended to higher dimensional cases. It is found that a number density difference of a small and large black holes decrease as a total dimension grows up. In particular, we find that a configurational entropy is a concave function of a reduced temperature and reaches a maximum value at a critical (second-order phase transition) point. Furthermore, the bigger a total dimension becomes, the more concave function in a configurational entropy while the more convex function in a reduced pressure. |
gr-qc/9910005 | Chris Isham | C.J. Isham and J.Butterfield | Some Possible Roles for Topos Theory in Quantum Theory and Quantum
Gravity | Submitted to {\em Foundations of Physics} for an issue in honour of
Marisa Dalla Chiara.} Based on a lecture given by CJI at the conference {\em
Towards a New Understanding of Space, Time and Matter}, University of British
Columbia, Canada (1999) | Found.Phys.30:1707-1735,2000 | 10.1023/A:1026406502316 | Imperial/TP/98-99/76 | gr-qc quant-ph | null | We discuss some ways in which topos theory (a branch of category theory) can
be applied to interpretative problems in quantum theory and quantum gravity. In
Section 1, we introduce these problems. In Section 2, we introduce topos
theory, especially the idea of a topos of presheaves. In Section 3, we discuss
several possible applications of topos theory to the problems in Section 1. In
Section 4, we draw some conclusions.
| [
{
"created": "Sat, 2 Oct 1999 13:39:57 GMT",
"version": "v1"
}
] | 2011-04-20 | [
[
"Isham",
"C. J.",
""
],
[
"Butterfield",
"J.",
""
]
] | We discuss some ways in which topos theory (a branch of category theory) can be applied to interpretative problems in quantum theory and quantum gravity. In Section 1, we introduce these problems. In Section 2, we introduce topos theory, especially the idea of a topos of presheaves. In Section 3, we discuss several possible applications of topos theory to the problems in Section 1. In Section 4, we draw some conclusions. |
gr-qc/9304026 | John D. Brown | David Brown | Action functionals for relativistic perfect fluids | 40 pages, plain TeX | Class.Quant.Grav.10:1579-1606,1993 | 10.1088/0264-9381/10/8/017 | null | gr-qc | null | Action functionals describing relativistic perfect fluids are presented. Two
of these actions apply to fluids whose equations of state are specified by
giving the fluid energy density as a function of particle number density and
entropy per particle. Other actions apply to fluids whose equations of state
are specified in terms of other choices of dependent and independent fluid
variables. Particular cases include actions for isentropic fluids and
pressureless dust. The canonical Hamiltonian forms of these actions are
derived, symmetries and conserved charges are identified, and the boundary
value and initial value problems are discussed. As in previous works on perfect
fluid actions, the action functionals considered here depend on certain
Lagrange multipliers and Lagrangian coordinate fields. Particular attention is
paid to the interpretations of these variables and to their relationships to
the physical properties of the fluid.
| [
{
"created": "Mon, 19 Apr 1993 19:44:44 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Brown",
"David",
""
]
] | Action functionals describing relativistic perfect fluids are presented. Two of these actions apply to fluids whose equations of state are specified by giving the fluid energy density as a function of particle number density and entropy per particle. Other actions apply to fluids whose equations of state are specified in terms of other choices of dependent and independent fluid variables. Particular cases include actions for isentropic fluids and pressureless dust. The canonical Hamiltonian forms of these actions are derived, symmetries and conserved charges are identified, and the boundary value and initial value problems are discussed. As in previous works on perfect fluid actions, the action functionals considered here depend on certain Lagrange multipliers and Lagrangian coordinate fields. Particular attention is paid to the interpretations of these variables and to their relationships to the physical properties of the fluid. |
1108.2009 | Yosef Zlochower | Carlos O. Lousto, Yosef Zlochower | Hangup Kicks: Still Larger Recoils by Partial Spin/Orbit Alignment of
Black-Hole Binaries | 4 pages, 3 figures, revtex 4, references fixed. To appear in PRL | Phys. Rev. Lett. 107, 231102 (2011) | 10.1103/PhysRevLett.107.231102 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the scenario of the gravitational radiation recoil acquired by the
final remnant of a black-hole-binary merger by studying a set of configurations
that have components of the spin both aligned with the orbital angular momentum
and in the orbital plane. We perform a series of 42 new full numerical
simulations for equal-mass and equal-spin-magnitude binaries. We extend
previous recoil fitting formulas to include nonlinear terms in the spins and
successfully include both the new and known results. The new predicted maximum
velocity approaches 5000km/s for spins partially aligned with the orbital
angular momentum, which leads to an important increase of the probabilities of
large recoils in generic astrophysical mergers. We find non-negligible
probabilities for recoils of several thousand km/s from accretion-aligned
binaries.
| [
{
"created": "Tue, 9 Aug 2011 18:51:41 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Sep 2011 17:58:43 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Sep 2011 22:28:20 GMT",
"version": "v3"
},
{
"created": "Fri, 18 Nov 2011 12:45:53 GMT",
"version": "v4"
}
] | 2011-12-13 | [
[
"Lousto",
"Carlos O.",
""
],
[
"Zlochower",
"Yosef",
""
]
] | We revisit the scenario of the gravitational radiation recoil acquired by the final remnant of a black-hole-binary merger by studying a set of configurations that have components of the spin both aligned with the orbital angular momentum and in the orbital plane. We perform a series of 42 new full numerical simulations for equal-mass and equal-spin-magnitude binaries. We extend previous recoil fitting formulas to include nonlinear terms in the spins and successfully include both the new and known results. The new predicted maximum velocity approaches 5000km/s for spins partially aligned with the orbital angular momentum, which leads to an important increase of the probabilities of large recoils in generic astrophysical mergers. We find non-negligible probabilities for recoils of several thousand km/s from accretion-aligned binaries. |
2003.10331 | Grigory Volovik | G.E. Volovik | Varying Newton constant and black hole to white hole quantum tunneling | 5 pages, no figures, revised after referee report, new section is
added | Universe 6, 133 (2020) | 10.3390/universe6090133 | null | gr-qc cond-mat.other hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamics of black holes is discussed for the case, when the Newton
constant $G$ is not a constant, but is the thermodynamic variable. This gives
for the first law of the Schwarzschild black hole thermodynamics:
$dS_\text{BH}= -AdK + \frac{dM}{T_\text{BH}}$, where the gravitational coupling
$K=1/4G$, $M$ is the black hole mass, $A$ is the area of horizon, and
$T_\text{BH}$ is Hawking temperature. From this first law it follows that the
dimensionless quantity $M^2/K$ is the adiabatic invariant, which in principle
can be quantized if to follow the Bekenstein conjecture. From the Euclidean
action for the black hole it follows that $K$ and $A$ serve as dynamically
conjugate variables. This allows us to calculate the quantum tunneling from the
black hole to the white hole, and determine the temperature and entropy of the
white hole.
| [
{
"created": "Mon, 23 Mar 2020 15:29:02 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Mar 2020 19:02:20 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Apr 2020 07:40:35 GMT",
"version": "v3"
},
{
"created": "Sat, 25 Apr 2020 10:38:18 GMT",
"version": "v4"
},
{
"created": "Sat, 2 May 2020 10:14:27 GMT",
"version": "v5"
},
{
"created": "Sun, 17 May 2020 13:45:43 GMT",
"version": "v6"
},
{
"created": "Wed, 3 Jun 2020 17:28:24 GMT",
"version": "v7"
},
{
"created": "Mon, 8 Jun 2020 09:06:26 GMT",
"version": "v8"
},
{
"created": "Sun, 26 Jul 2020 11:24:38 GMT",
"version": "v9"
}
] | 2020-09-02 | [
[
"Volovik",
"G. E.",
""
]
] | The thermodynamics of black holes is discussed for the case, when the Newton constant $G$ is not a constant, but is the thermodynamic variable. This gives for the first law of the Schwarzschild black hole thermodynamics: $dS_\text{BH}= -AdK + \frac{dM}{T_\text{BH}}$, where the gravitational coupling $K=1/4G$, $M$ is the black hole mass, $A$ is the area of horizon, and $T_\text{BH}$ is Hawking temperature. From this first law it follows that the dimensionless quantity $M^2/K$ is the adiabatic invariant, which in principle can be quantized if to follow the Bekenstein conjecture. From the Euclidean action for the black hole it follows that $K$ and $A$ serve as dynamically conjugate variables. This allows us to calculate the quantum tunneling from the black hole to the white hole, and determine the temperature and entropy of the white hole. |
1109.3177 | Orlando Luongo | Alejandro Aviles, Luca Bonanno, Orlando Luongo, Hernando Quevedo | Holographic dark matter and dark energy with second order invariants | 12 figures, revtex style | Phys. Rev. D 84, 103520, (2011) | 10.1103/PhysRevD.84.103520 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the main goals of modern cosmology remains to summon up a self
consistent policy, able to explain, in the framework of the Einstein's theory,
the cosmic speed up and the presence of Dark Matter in the Universe.
Accordingly to the Holographic principle, which postulates the existence of a
minimal size of a physical region, we argue, in this paper, that if this size
exists for the Universe and it is accrued from the independent geometrical
second order invariants, it would be possible to ensure a surprising source for
Dark Matter and a viable candidate for explaining the late acceleration of the
Universe. Along the work, we develop low redshift tests, such as Supernovae Ia
and kinematical analysis complied by the use of Cosmography and we compare the
outcomes with higher redshift tests, such as CMB peak and anisotropy of the
cosmic power spectrum. All the results indicate that the models presented here
can be interpreted as unified models that are capable to describe both the dark
matter and the dark energy.
| [
{
"created": "Wed, 14 Sep 2011 19:38:03 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Nov 2011 18:06:50 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Aviles",
"Alejandro",
""
],
[
"Bonanno",
"Luca",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Quevedo",
"Hernando",
""
]
] | One of the main goals of modern cosmology remains to summon up a self consistent policy, able to explain, in the framework of the Einstein's theory, the cosmic speed up and the presence of Dark Matter in the Universe. Accordingly to the Holographic principle, which postulates the existence of a minimal size of a physical region, we argue, in this paper, that if this size exists for the Universe and it is accrued from the independent geometrical second order invariants, it would be possible to ensure a surprising source for Dark Matter and a viable candidate for explaining the late acceleration of the Universe. Along the work, we develop low redshift tests, such as Supernovae Ia and kinematical analysis complied by the use of Cosmography and we compare the outcomes with higher redshift tests, such as CMB peak and anisotropy of the cosmic power spectrum. All the results indicate that the models presented here can be interpreted as unified models that are capable to describe both the dark matter and the dark energy. |
1408.3111 | Sajid Ali | Ibrar Hussain, Sajid Ali | Effect of quintessence on the energy of the Reissner-Nordstrom black
hole | 12 pages, 2 figures | General Relativity and Gravitation March 2015, 47:34 | 10.1007/s10714-015-1883-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The energy content of the Reissner-Nordstrom black hole surrounded by
quintessence is investigated using approximate Lie symmetry methods. It is
mainly done by assuming mass and charge of the black hole as small quantities
($\epsilon$), and by retaining its second power in the perturbed geodesic
equations for such black hole while neglecting its higher powers. Due to the
presence of trivial second-order approximate Lie symmetries of these perturbed
geodesic equations, a rescaling of the geodetic parameter gives a rescaling of
the energy in this black hole. Interestingly we obtain an explicit relation of
the rescaling factor that depends on the square of the charge to mass ratio of
the black hole, the normalization factor $\alpha$, which is related to the
state parameter of the quintessence matter, and the coordinate $r$. A
comparison of this rescaling factor with that of the Reissner-Nordstrom black
hole (Hussain et. al SIGMA, 2007), without quintessence is given. It is
observed that the presence of the quintessence field reduces the energy in this
black hole spacetime. Further it is found that there exists a point outside the
event horizon of this black hole where the effect of quintessence balances the
energy content in this black hole without quintessence, and where the total
energy of the underlying spacetime becomes zero.
| [
{
"created": "Wed, 13 Aug 2014 07:10:04 GMT",
"version": "v1"
}
] | 2015-03-23 | [
[
"Hussain",
"Ibrar",
""
],
[
"Ali",
"Sajid",
""
]
] | The energy content of the Reissner-Nordstrom black hole surrounded by quintessence is investigated using approximate Lie symmetry methods. It is mainly done by assuming mass and charge of the black hole as small quantities ($\epsilon$), and by retaining its second power in the perturbed geodesic equations for such black hole while neglecting its higher powers. Due to the presence of trivial second-order approximate Lie symmetries of these perturbed geodesic equations, a rescaling of the geodetic parameter gives a rescaling of the energy in this black hole. Interestingly we obtain an explicit relation of the rescaling factor that depends on the square of the charge to mass ratio of the black hole, the normalization factor $\alpha$, which is related to the state parameter of the quintessence matter, and the coordinate $r$. A comparison of this rescaling factor with that of the Reissner-Nordstrom black hole (Hussain et. al SIGMA, 2007), without quintessence is given. It is observed that the presence of the quintessence field reduces the energy in this black hole spacetime. Further it is found that there exists a point outside the event horizon of this black hole where the effect of quintessence balances the energy content in this black hole without quintessence, and where the total energy of the underlying spacetime becomes zero. |
2302.07250 | Cillian Rew | C.Rew and W.E.V. Barker | The effective inflationary potential of constant-torsion emergent
gravity | 15 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Constant-torsion emergent gravity (CTEG) has a Lagrangian quadratic in
curvature and torsion, but without any Einstein--Hilbert term. CTEG is
motivated by a unitary, power-counting renormalisable particle spectrum. The
timelike axial torsion adopts a vacuum expectation value, and the Friedmann
cosmology emerges dynamically on this torsion condensate. We show that this
mechanism -- and the whole background cosmology of CTEG -- may be understood
through the effective potential of a canonical single scalar field model. The
effective potential allows for hilltop inflation in the early Universe. In the
late Universe, the Hubble friction overdamps the final quadratic approach to
the effective minimum at the condensate, where the value of the potential
becomes the cosmological constant. We do not consider particle production
through spin-torsion coupling, or running of Lagrangian parameters. The model
must be completed if reheating and a separation of inflationary and dark energy
scales are to be understood. It is suggested that the divergence of the
potential at large values of the scalar is inconsistent with the linearised
propagator analysis of CTEG around zero-torsion Minkowski spacetime. This
background may therefore be a strongly coupled surface in CTEG.
| [
{
"created": "Tue, 14 Feb 2023 18:46:01 GMT",
"version": "v1"
}
] | 2023-02-15 | [
[
"Rew",
"C.",
""
],
[
"Barker",
"W. E. V.",
""
]
] | Constant-torsion emergent gravity (CTEG) has a Lagrangian quadratic in curvature and torsion, but without any Einstein--Hilbert term. CTEG is motivated by a unitary, power-counting renormalisable particle spectrum. The timelike axial torsion adopts a vacuum expectation value, and the Friedmann cosmology emerges dynamically on this torsion condensate. We show that this mechanism -- and the whole background cosmology of CTEG -- may be understood through the effective potential of a canonical single scalar field model. The effective potential allows for hilltop inflation in the early Universe. In the late Universe, the Hubble friction overdamps the final quadratic approach to the effective minimum at the condensate, where the value of the potential becomes the cosmological constant. We do not consider particle production through spin-torsion coupling, or running of Lagrangian parameters. The model must be completed if reheating and a separation of inflationary and dark energy scales are to be understood. It is suggested that the divergence of the potential at large values of the scalar is inconsistent with the linearised propagator analysis of CTEG around zero-torsion Minkowski spacetime. This background may therefore be a strongly coupled surface in CTEG. |
gr-qc/9611005 | Marco `BRONI` Bruni | M. Bruni, H. van Elst, C. Uggla | Singularities in Silent Universes: State of the Art | 6 papes, Proceedings of the 12th Italian Conference of General
Relativity and Gravitational Physics, style included | null | null | IC/96/223, SISSA--160/96/A | gr-qc astro-ph | null | After a brief overview of the so-called silent models and their present
status, we consider the subclass of Bianchi Type--I models with a magnetic
field source. Due to the presence of the magnetic field, the initial
singularity shows ``oscillatory'' features reminiscent of the Bianchi Type--IX
case. The Bianchi Type--I models with a magnetic field are therefore a
counterexample to the folklore that matter fields can be neglected in the
vicinity of the singularity.
| [
{
"created": "Mon, 4 Nov 1996 17:11:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bruni",
"M.",
""
],
[
"van Elst",
"H.",
""
],
[
"Uggla",
"C.",
""
]
] | After a brief overview of the so-called silent models and their present status, we consider the subclass of Bianchi Type--I models with a magnetic field source. Due to the presence of the magnetic field, the initial singularity shows ``oscillatory'' features reminiscent of the Bianchi Type--IX case. The Bianchi Type--I models with a magnetic field are therefore a counterexample to the folklore that matter fields can be neglected in the vicinity of the singularity. |
2012.02548 | Valeriy Obukhov | V. V. Obukhov | Separation of variables in Hamilton-Jacobi and Klein-Gordon-Fock
equations for a charged test particle in the Stackel spaces of type (1.1) | The article will be published in IJGMMP | null | 10.1142/S0219887821500365 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All equivalence classes for electromagnetic potentials and space-time metrics
of Stackel spaces, provided that Hamilton-Jacobi equation and Klein-Gordon-Fock
equation for a charged test particle can be integrated by the method of
complete separation of variables are found. The separation is carried out using
the complete sets of mutually-commuting integrals of motion of type (1.1).
Whereby in a privileged coordinate system the given equations turn into
parabolic type equations. Hence, these metrics can be used as models for
describing plane gravitational waves.
| [
{
"created": "Fri, 4 Dec 2020 12:07:53 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Dec 2020 10:14:15 GMT",
"version": "v2"
}
] | 2021-03-31 | [
[
"Obukhov",
"V. V.",
""
]
] | All equivalence classes for electromagnetic potentials and space-time metrics of Stackel spaces, provided that Hamilton-Jacobi equation and Klein-Gordon-Fock equation for a charged test particle can be integrated by the method of complete separation of variables are found. The separation is carried out using the complete sets of mutually-commuting integrals of motion of type (1.1). Whereby in a privileged coordinate system the given equations turn into parabolic type equations. Hence, these metrics can be used as models for describing plane gravitational waves. |
1908.05707 | Stephen Fairhurst | Stephen Fairhurst, Rhys Green, Charlie Hoy, Mark Hannam, Alistair Muir | Two-harmonic approximation for gravitational waveforms from precessing
binaries | 23 pages, 9 figures. Accepted for publication in PRD | Phys. Rev. D 102, 024055 (2020) | 10.1103/PhysRevD.102.024055 | LIGO-P1900225 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary-black-hole orbits precess when the black-hole spins are mis-aligned
with the binary's orbital angular momentum. The apparently complicated dynamics
can in most cases be described as simple precession of the orbital angular
momentum about an approximately fixed total angular momentum. However, the
imprint of the precession on the observed gravitational-wave signal is yet more
complicated, with a non-trivial time-varying dependence on black-hole dynamics,
the binary's orientation and the detector polarization. As a result, it is
difficult to predict under which conditions precession effects are measurable
in gravitational-wave observations, and their impact on both signal detection
and source characterization. We show that the observed waveform can be
simplified by decomposing it as a power series in a new precession parameter $b
= \tan(\beta/2)$, where $\beta$ is the opening angle between the orbital and
total angular momenta. The power series is made up of five harmonics, with
frequencies that differ by the binary's precession frequency, and individually
do not exhibit amplitude and phase modulations. In many cases, the waveform can
be well approximated by the two leading harmonics. In this approximation we are
able to obtain a simple picture of precession as caused by the beating of two
waveforms of similar frequency. This enables us to identify regions of the
parameter space where precession is likely to have an observable effect on the
waveform, and to propose a new approach to searching for signals from
precessing binaries, based upon the two-harmonic approximation.
| [
{
"created": "Thu, 15 Aug 2019 18:54:37 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 2020 09:46:17 GMT",
"version": "v2"
}
] | 2020-07-22 | [
[
"Fairhurst",
"Stephen",
""
],
[
"Green",
"Rhys",
""
],
[
"Hoy",
"Charlie",
""
],
[
"Hannam",
"Mark",
""
],
[
"Muir",
"Alistair",
""
]
] | Binary-black-hole orbits precess when the black-hole spins are mis-aligned with the binary's orbital angular momentum. The apparently complicated dynamics can in most cases be described as simple precession of the orbital angular momentum about an approximately fixed total angular momentum. However, the imprint of the precession on the observed gravitational-wave signal is yet more complicated, with a non-trivial time-varying dependence on black-hole dynamics, the binary's orientation and the detector polarization. As a result, it is difficult to predict under which conditions precession effects are measurable in gravitational-wave observations, and their impact on both signal detection and source characterization. We show that the observed waveform can be simplified by decomposing it as a power series in a new precession parameter $b = \tan(\beta/2)$, where $\beta$ is the opening angle between the orbital and total angular momenta. The power series is made up of five harmonics, with frequencies that differ by the binary's precession frequency, and individually do not exhibit amplitude and phase modulations. In many cases, the waveform can be well approximated by the two leading harmonics. In this approximation we are able to obtain a simple picture of precession as caused by the beating of two waveforms of similar frequency. This enables us to identify regions of the parameter space where precession is likely to have an observable effect on the waveform, and to propose a new approach to searching for signals from precessing binaries, based upon the two-harmonic approximation. |
gr-qc/0506029 | Matt Visser | Matt Visser (Victoria University of Wellington) and Silke Weinfurtner
(Victoria University of Wellington) | Massive Klein--Gordon equation from a BEC-based analogue spacetime | V1: 10 pages; uses revtex4; V2: two references and brief comments
added | Phys.Rev. D72 (2005) 044020 | 10.1103/PhysRevD.72.044020 | null | gr-qc | null | We extend the "analogue spacetime" programme by investigating a
condensed-matter system that is in principle capable of simulating the massive
Klein--Gordon equation in curved spacetime. Since many elementary particles
have mass, this is an essential step in building realistic analogue models, and
a first step towards simulating quantum gravity phenomenology. Specifically, we
consider the class of two-component BECs subject to laser-induced transitions
between the components. This system exhibits a complicated spectrum of normal
mode excitations, which can be viewed as two interacting phonon modes that
exhibit the phenomenon of "refringence". We study the conditions required to
make these two phonon modes decouple. Once decoupled, the two distinct phonons
generically couple to distinct effective spacetimes, representing a bi-metric
model, with one of the modes acquiring a mass. In the eikonal limit the massive
mode exhibits the dispersion relation of a massive relativistic particle: omega
= sqrt[omega_0^2 + c^2 k^2], plus curved-space modifications. Furthermore, it
is possible to tune the system so that both modes can be arranged to travel at
the same speed, in which case the two phonon excitations couple to the same
effective metric. From the analogue spacetime perspective this situation
corresponds to the Einstein equivalence principle being satisfied.
| [
{
"created": "Mon, 6 Jun 2005 07:28:13 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2005 08:48:39 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
],
[
"Weinfurtner",
"Silke",
"",
"Victoria University of Wellington"
]
] | We extend the "analogue spacetime" programme by investigating a condensed-matter system that is in principle capable of simulating the massive Klein--Gordon equation in curved spacetime. Since many elementary particles have mass, this is an essential step in building realistic analogue models, and a first step towards simulating quantum gravity phenomenology. Specifically, we consider the class of two-component BECs subject to laser-induced transitions between the components. This system exhibits a complicated spectrum of normal mode excitations, which can be viewed as two interacting phonon modes that exhibit the phenomenon of "refringence". We study the conditions required to make these two phonon modes decouple. Once decoupled, the two distinct phonons generically couple to distinct effective spacetimes, representing a bi-metric model, with one of the modes acquiring a mass. In the eikonal limit the massive mode exhibits the dispersion relation of a massive relativistic particle: omega = sqrt[omega_0^2 + c^2 k^2], plus curved-space modifications. Furthermore, it is possible to tune the system so that both modes can be arranged to travel at the same speed, in which case the two phonon excitations couple to the same effective metric. From the analogue spacetime perspective this situation corresponds to the Einstein equivalence principle being satisfied. |
0811.2524 | Hernando Quevedo | Hernando Quevedo and Alberto Sanchez | Geometric description of BTZ black holes thermodynamics | null | Phys.Rev.D79:024012,2009 | 10.1103/PhysRevD.79.024012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the properties of the space of thermodynamic equilibrium states of
the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole in (2+1)-gravity. We use the
formalism of geometrothermodynamics to introduce in the space of equilibrium
states a $2-$dimensional thermodynamic metric whose curvature is non-vanishing,
indicating the presence of thermodynamic interaction, and free of
singularities, indicating the absence of phase transitions. Similar results are
obtained for generalizations of the BTZ black hole which include a Chern-Simons
term and a dilatonic field. Small logarithmic corrections of the entropy turn
out to be represented by small corrections of the thermodynamic curvature,
reinforcing the idea that thermodynamic curvature is a measure of thermodynamic
interaction.
| [
{
"created": "Sat, 15 Nov 2008 20:08:03 GMT",
"version": "v1"
}
] | 2009-01-21 | [
[
"Quevedo",
"Hernando",
""
],
[
"Sanchez",
"Alberto",
""
]
] | We study the properties of the space of thermodynamic equilibrium states of the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole in (2+1)-gravity. We use the formalism of geometrothermodynamics to introduce in the space of equilibrium states a $2-$dimensional thermodynamic metric whose curvature is non-vanishing, indicating the presence of thermodynamic interaction, and free of singularities, indicating the absence of phase transitions. Similar results are obtained for generalizations of the BTZ black hole which include a Chern-Simons term and a dilatonic field. Small logarithmic corrections of the entropy turn out to be represented by small corrections of the thermodynamic curvature, reinforcing the idea that thermodynamic curvature is a measure of thermodynamic interaction. |
1004.4549 | Yi Xie | Xin Wu (Nanchang University) and Yi Xie (Nanjing University) | Symplectic structure of post-Newtonian Hamiltonian for spinning compact
binaries | 7 pages, no fig. | Phys.Rev.D81:084045,2010 | 10.1103/PhysRevD.81.084045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phase space of a Hamiltonian system is symplectic. However, the
post-Newtonian Hamiltonian formulation of spinning compact binaries in existing
publications does not have this property, when position, momentum and spin
variables $[X, P, S_1, S_2]$ compose its phase space. This may give a
convenient application of perturbation theory to the derivation of the
post-Newtonian formulation, but also makes classic theories of a symplectic
Hamiltonian system be a serious obstacle in application, especially in
diagnosing integrability and nonintegrability from a dynamical system theory
perspective. To completely understand the dynamical characteristic of the
integrability or nonintegrability for the binary system, we construct a set of
conjugate spin variables and reexpress the spin Hamiltonian part so as to make
the complete Hamiltonian formulation symplectic. As a result, it is directly
shown with the least number of independent isolating integrals that a
conservative Hamiltonian compact binary system with both one spin and the pure
orbital part to any post-Newtonian order is typically integrable and not
chaotic. And conservative binary system consisting of two spins restricted to
the leading order spin-orbit interaction and the pure orbital part at all
post-Newtonian orders is also integrable, independently on the mass ratio. For
all other various spinning cases, the onset of chaos is possible.
| [
{
"created": "Mon, 26 Apr 2010 15:14:42 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Wu",
"Xin",
"",
"Nanchang University"
],
[
"Xie",
"Yi",
"",
"Nanjing University"
]
] | The phase space of a Hamiltonian system is symplectic. However, the post-Newtonian Hamiltonian formulation of spinning compact binaries in existing publications does not have this property, when position, momentum and spin variables $[X, P, S_1, S_2]$ compose its phase space. This may give a convenient application of perturbation theory to the derivation of the post-Newtonian formulation, but also makes classic theories of a symplectic Hamiltonian system be a serious obstacle in application, especially in diagnosing integrability and nonintegrability from a dynamical system theory perspective. To completely understand the dynamical characteristic of the integrability or nonintegrability for the binary system, we construct a set of conjugate spin variables and reexpress the spin Hamiltonian part so as to make the complete Hamiltonian formulation symplectic. As a result, it is directly shown with the least number of independent isolating integrals that a conservative Hamiltonian compact binary system with both one spin and the pure orbital part to any post-Newtonian order is typically integrable and not chaotic. And conservative binary system consisting of two spins restricted to the leading order spin-orbit interaction and the pure orbital part at all post-Newtonian orders is also integrable, independently on the mass ratio. For all other various spinning cases, the onset of chaos is possible. |
1501.01749 | Taeyoon Moon | Yun Soo Myung and Taeyoon Moon | Scale-invariant tensor spectrum from conformal gravity | 1+9 pages, no figure, version to appear in Mod. Phys. Lett. A | null | 10.1142/S0217732315501722 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmological tensor perturbations generated during de Sitter
inflation in the conformal gravity with mass parameter $m^2=2H^2$. It turns out
that tensor power spectrum is scale-invariant.
| [
{
"created": "Thu, 8 Jan 2015 07:30:13 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jul 2015 08:45:05 GMT",
"version": "v2"
}
] | 2015-10-21 | [
[
"Myung",
"Yun Soo",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We study cosmological tensor perturbations generated during de Sitter inflation in the conformal gravity with mass parameter $m^2=2H^2$. It turns out that tensor power spectrum is scale-invariant. |
2105.00965 | Vittorio De Falco Dr | Vittorio De Falco, William Borrelli | Timescales of the chaos onset in the general relativistic
Poynting-Robertson effect | 11 pages; 4 figures; 3 tables; accepted for publication on PRD | null | 10.1103/PhysRevD.103.124012 | null | gr-qc astro-ph.HE hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | It has been proved that the general relativistic Poynting-Robertson effect in
the equatorial plane of Kerr metric shows a chaotic behavior for a suitable
range of parameters. As a further step, we calculate the timescale for the
onset of chaos through the Lyapunov exponents, estimating how this trend
impacts on the observational dynamics. We conclude our analyses with a
discussion on the possibility to observe this phenomenon in neutron star and
black hole astrophysical sources.
| [
{
"created": "Mon, 3 May 2021 16:01:22 GMT",
"version": "v1"
}
] | 2021-06-16 | [
[
"De Falco",
"Vittorio",
""
],
[
"Borrelli",
"William",
""
]
] | It has been proved that the general relativistic Poynting-Robertson effect in the equatorial plane of Kerr metric shows a chaotic behavior for a suitable range of parameters. As a further step, we calculate the timescale for the onset of chaos through the Lyapunov exponents, estimating how this trend impacts on the observational dynamics. We conclude our analyses with a discussion on the possibility to observe this phenomenon in neutron star and black hole astrophysical sources. |
1109.4377 | Jorma Louko | Lee Hodgkinson, Jorma Louko | How often does the Unruh-DeWitt detector click beyond four dimensions? | 30 pages. v3: presentational improvement. Published version | J. Math. Phys. 53, 082301 (2012) | 10.1063/1.4739453 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the response of an arbitrarily-accelerated Unruh-DeWitt detector
coupled to a massless scalar field in Minkowski spacetimes of dimensions up to
six, working within first-order perturbation theory and assuming a smooth
switch-on and switch-off. We express the total transition probability as a
manifestly finite and regulator-free integral formula. In the sharp switching
limit, the transition probability diverges in dimensions greater than three but
the transition rate remains finite up to dimension five. In dimension six, the
transition rate remains finite in the sharp switching limit for trajectories of
constant scalar proper acceleration, including all stationary trajectories, but
it diverges for generic trajectories. The divergence of the transition rate in
six dimensions suggests that global embedding spacetime (GEMS) methods for
investigating detector response in curved spacetime may have limited validity
for generic trajectories when the embedding spacetime has dimension higher than
five.
| [
{
"created": "Tue, 20 Sep 2011 17:42:30 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Oct 2011 17:42:56 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Aug 2012 15:57:22 GMT",
"version": "v3"
}
] | 2012-08-07 | [
[
"Hodgkinson",
"Lee",
""
],
[
"Louko",
"Jorma",
""
]
] | We analyse the response of an arbitrarily-accelerated Unruh-DeWitt detector coupled to a massless scalar field in Minkowski spacetimes of dimensions up to six, working within first-order perturbation theory and assuming a smooth switch-on and switch-off. We express the total transition probability as a manifestly finite and regulator-free integral formula. In the sharp switching limit, the transition probability diverges in dimensions greater than three but the transition rate remains finite up to dimension five. In dimension six, the transition rate remains finite in the sharp switching limit for trajectories of constant scalar proper acceleration, including all stationary trajectories, but it diverges for generic trajectories. The divergence of the transition rate in six dimensions suggests that global embedding spacetime (GEMS) methods for investigating detector response in curved spacetime may have limited validity for generic trajectories when the embedding spacetime has dimension higher than five. |
gr-qc/9605001 | Euejin Jeong | Eue Jin Jeong | Extracting Gravitational Energy From The Homogeneous Isotropic Universe | Latex, 6 pages | null | null | null | gr-qc | null | The kinetic energy of a local system of objects placed in a curved spacetime
is gained by the subsequent acceleration of the object following the more
contracted region of spacetime. Normally this happens near massive gravitating
stars. However, the gravitational dipole moment has been shown to be capable of
self creating asymmetrically distorted spacetime in its vicinity, therby,
capable of being accelerated indefinitely following the successive self created
loophole of the spacetime. Localization of this kinetic energy may be possible
by designing a system that uses the artificially created gavitational dipole
moments to rotate the main axis. A mechanical constraint is derived for the
extraction of unlimited gravitational energy from such system.
| [
{
"created": "Wed, 1 May 1996 09:10:46 GMT",
"version": "v1"
},
{
"created": "Sat, 4 May 1996 08:38:33 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Jeong",
"Eue Jin",
""
]
] | The kinetic energy of a local system of objects placed in a curved spacetime is gained by the subsequent acceleration of the object following the more contracted region of spacetime. Normally this happens near massive gravitating stars. However, the gravitational dipole moment has been shown to be capable of self creating asymmetrically distorted spacetime in its vicinity, therby, capable of being accelerated indefinitely following the successive self created loophole of the spacetime. Localization of this kinetic energy may be possible by designing a system that uses the artificially created gavitational dipole moments to rotate the main axis. A mechanical constraint is derived for the extraction of unlimited gravitational energy from such system. |
2307.13255 | Omar Mustafa | Omar. Mustafa, Faizuddin Ahmed | A note on "The Klein-Gordon oscillator in (1+2)-dimensions G\"urses
space-time backgrounds (Ann. Phys. (N. Y.) 404 (2019) 1)" | 4 pages | Ann. Phys. 457 (2023) 169424 | 10.1016/j.aop.2023.169424 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We revisit and discuss the KG-oscillator in the $(1+2)$-dimensional
G\"{u}rses space-time studied in (F. Ahmed, Ann. Phys. (N. Y.) 404 (2019) 1).
The modified oscillator frequency {\it i.e.,}
$\tilde{\omega}^{2}=(\Omega^{2}\,E^{2}+\eta^{2})$ appeared in the eigenvalue
equation is an energy-dependent parameter, and consequently, the results are
accurately reported here. Moreover, we show some interesting spectroscopic
features indulged within the very nature of G\"{u}rses space-time for the
KG-G\"{u}rses oscillators.
| [
{
"created": "Tue, 25 Jul 2023 04:53:44 GMT",
"version": "v1"
}
] | 2023-07-26 | [
[
"Mustafa",
"Omar.",
""
],
[
"Ahmed",
"Faizuddin",
""
]
] | We revisit and discuss the KG-oscillator in the $(1+2)$-dimensional G\"{u}rses space-time studied in (F. Ahmed, Ann. Phys. (N. Y.) 404 (2019) 1). The modified oscillator frequency {\it i.e.,} $\tilde{\omega}^{2}=(\Omega^{2}\,E^{2}+\eta^{2})$ appeared in the eigenvalue equation is an energy-dependent parameter, and consequently, the results are accurately reported here. Moreover, we show some interesting spectroscopic features indulged within the very nature of G\"{u}rses space-time for the KG-G\"{u}rses oscillators. |
2003.10969 | David Kofro\v{n} | David Kofro\v{n} | Point particles and Appell's solutions on the axis of Kerr black hole
for arbitrary spin in terms of the Debye potentials | 11 pages | Search Results Web results Phys. Rev. D 101, 064027 (2020) | 10.1103/PhysRevD.101.064027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Teukolsky master equation -- a fundamental equation for test fields of
any spin, or perturbations, in type D spacetimes -- is classically treated in
its separated form. Then the solutions representing even the simplest sources
-- point particles -- are expressed in terms of series. The only known
exception is a static particle (charge or mass) in the vicinity of
Schwarzschild black hole. Here, we present a generalization of this result to a
static point particle of arbitrary spin at the axis of Kerr black hole. A
simple algebraic formula for the Debye potential from which all the NP
components of the field under consideration can be generated is written down
explicitly. Later, we focus on the electromagnetic field and employ the classic
Appell's trick (moving the source into a complex space) to get so called
electromagnetic magic field on the Kerr background. Thus the field of
nontrivial extended yet spatially bounded source is obtained. We also show that
a static electric point charge above the Kerr black hole induces, except an
expected electric monopole, also a magnetic monopole charge on the black hole
itself. This contribution has to be compensated. On a general level we discuss
Teukolsky-Starobinsky identities in terms of the Debye potentials.
| [
{
"created": "Tue, 24 Mar 2020 16:54:52 GMT",
"version": "v1"
}
] | 2020-04-01 | [
[
"Kofroň",
"David",
""
]
] | The Teukolsky master equation -- a fundamental equation for test fields of any spin, or perturbations, in type D spacetimes -- is classically treated in its separated form. Then the solutions representing even the simplest sources -- point particles -- are expressed in terms of series. The only known exception is a static particle (charge or mass) in the vicinity of Schwarzschild black hole. Here, we present a generalization of this result to a static point particle of arbitrary spin at the axis of Kerr black hole. A simple algebraic formula for the Debye potential from which all the NP components of the field under consideration can be generated is written down explicitly. Later, we focus on the electromagnetic field and employ the classic Appell's trick (moving the source into a complex space) to get so called electromagnetic magic field on the Kerr background. Thus the field of nontrivial extended yet spatially bounded source is obtained. We also show that a static electric point charge above the Kerr black hole induces, except an expected electric monopole, also a magnetic monopole charge on the black hole itself. This contribution has to be compensated. On a general level we discuss Teukolsky-Starobinsky identities in terms of the Debye potentials. |
gr-qc/0504012 | Edward Porter | Neil J. Cornish and Edward K. Porter | Detecting Galactic Binaries with LISA | 7 pages-2 figures. One figure added and typos corrected. Accepted for
the proceedings of GWDAW 9, special edition of Classical and Quantum Gravity | Class.Quant.Grav. 22 (2005) S927-S934 | 10.1088/0264-9381/22/18/S06 | null | gr-qc | null | One of the main sources of gravitational waves for the LISA space-borne
interferometer are galactic binary systems. The waveforms for these sources are
represented by eight parameters, of which four are extrinsic, and four are
intrinsic to the system. Geometrically, these signals exist in an 8-d parameter
space. By calculating the metric tensor on this space, we calculate the number
of templates needed to search for such sources. We show in this study that
below a particular monochromatic frequency, we can ignore one of the intrinsic
parameters and search over a 7-d space. Beyond this frequency, we have a sudden
change in dimensionality of the parameter space from 7 to 8 dimensions, which
results in a change in the scaling of the growth of template number as a
function of monochromatic frequency.
| [
{
"created": "Mon, 4 Apr 2005 18:41:16 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Aug 2005 21:07:22 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Cornish",
"Neil J.",
""
],
[
"Porter",
"Edward K.",
""
]
] | One of the main sources of gravitational waves for the LISA space-borne interferometer are galactic binary systems. The waveforms for these sources are represented by eight parameters, of which four are extrinsic, and four are intrinsic to the system. Geometrically, these signals exist in an 8-d parameter space. By calculating the metric tensor on this space, we calculate the number of templates needed to search for such sources. We show in this study that below a particular monochromatic frequency, we can ignore one of the intrinsic parameters and search over a 7-d space. Beyond this frequency, we have a sudden change in dimensionality of the parameter space from 7 to 8 dimensions, which results in a change in the scaling of the growth of template number as a function of monochromatic frequency. |
1911.12329 | Michael Coughlin | M. Coughlin, J. Harms, D.C. Bowden, P. Meyers, V.C. Tsai, V. Mandic,
G. Pavlis, and T. Prestegard | Coherence-based approaches for estimating the composition of the seismic
wavefield | null | Journal of Geophysical Research: Solid Earth, 124, 2941-2956, 2019 | 10.1029/2018JB016608 | null | gr-qc physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As new techniques exploiting the Earth's ambient seismic noise field are
developed and applied, such as for the observation of temporal changes in
seismic velocity structure, it is crucial to quantify the precision with which
wave-type measurements can be made. This work uses array data at the Homestake
mine in Lead, South Dakota and an array at Sweetwater, Texas to consider two
aspects that control this precision: the types of seismic wave contributing to
the ambient noise field at microseism frequencies and the effect of array
geometry. Both are quantified using measurements of wavefield coherence between
stations in combination with Wiener filters. We find a strong seasonal change
between body-wave and surface-wave content. Regarding the inclusion of
underground stations, we quantify the lower limit to which the ambient noise
field can be characterized and reproduced; the applications of the Wiener
filters are about 4 times more successful in reproducing ambient noise
waveforms when underground stations are included in the array, resulting in
predictions of seismic timeseries with less than a 1\% residual, and are
ultimately limited by the geometry and aperture of the array, as well as by
temporal variations in the seismic field. We discuss the implications of these
results for the geophysics community performing ambient seismic noise studies,
as well as for the cancellation of seismic Newtonian gravity noise in
ground-based, sub-Hz, gravitational-wave detectors.
| [
{
"created": "Wed, 27 Nov 2019 18:15:05 GMT",
"version": "v1"
}
] | 2019-11-28 | [
[
"Coughlin",
"M.",
""
],
[
"Harms",
"J.",
""
],
[
"Bowden",
"D. C.",
""
],
[
"Meyers",
"P.",
""
],
[
"Tsai",
"V. C.",
""
],
[
"Mandic",
"V.",
""
],
[
"Pavlis",
"G.",
""
],
[
"Prestegard",
"T.",
""
]
] | As new techniques exploiting the Earth's ambient seismic noise field are developed and applied, such as for the observation of temporal changes in seismic velocity structure, it is crucial to quantify the precision with which wave-type measurements can be made. This work uses array data at the Homestake mine in Lead, South Dakota and an array at Sweetwater, Texas to consider two aspects that control this precision: the types of seismic wave contributing to the ambient noise field at microseism frequencies and the effect of array geometry. Both are quantified using measurements of wavefield coherence between stations in combination with Wiener filters. We find a strong seasonal change between body-wave and surface-wave content. Regarding the inclusion of underground stations, we quantify the lower limit to which the ambient noise field can be characterized and reproduced; the applications of the Wiener filters are about 4 times more successful in reproducing ambient noise waveforms when underground stations are included in the array, resulting in predictions of seismic timeseries with less than a 1\% residual, and are ultimately limited by the geometry and aperture of the array, as well as by temporal variations in the seismic field. We discuss the implications of these results for the geophysics community performing ambient seismic noise studies, as well as for the cancellation of seismic Newtonian gravity noise in ground-based, sub-Hz, gravitational-wave detectors. |
gr-qc/0302034 | Nikolaos Stergioulas | Nikolaos Stergioulas | Rotating Stars in Relativity | 101 pages, 18 figures. The full online-readable version of this
article, including several animations, will be published in Living Reviews in
Relativity at http://www.livingreviews.org/ | LivingRev.Rel.6:3,2003 | 10.12942/lrr-2003-3 | AUTH-LR2003 | gr-qc astro-ph | null | Rotating relativistic stars have been studied extensively in recent years,
both theoretically and observationally, because of the information one could
obtain about the equation of state of matter at extremely high densities and
because they are considered to be promising sources of gravitational waves. The
latest theoretical understanding of rotating stars in relativity is reviewed in
this updated article. The sections on the equilibrium properties and on the
nonaxisymmetric instabilities in f-modes and r-modes have been updated and
several new sections have been added on analytic solutions for the exterior
spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating
stars in numerical relativity.
| [
{
"created": "Mon, 10 Feb 2003 16:14:57 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Stergioulas",
"Nikolaos",
""
]
] | Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information one could obtain about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on the equilibrium properties and on the nonaxisymmetric instabilities in f-modes and r-modes have been updated and several new sections have been added on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity. |
1204.3421 | Stefan Hollands | Stefan Hollands | Black hole uniqueness theorems and new thermodynamic identities in
eleven dimensional supergravity | 50pp, 3 figures, v2: references added, correction in appendix B,
conclusions added, v3: reference section edited, typos removed, minor changes
in appendix D | null | 10.1088/0264-9381/29/20/205009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider stationary, non-extremal black holes in 11-dimensional
supergravity having isometry group $\mathbb{R} \times U(1)^8$. We prove that
such a black hole is uniquely specified by its angular momenta, its electric
charges associated with the various 7-cycles in the manifold, together with
certain moduli and vector valued winding numbers characterizing the topological
nature of the spacetime and group action. We furthermore establish interesting,
non-trivial, relations between the thermodynamic quantities associated with the
black hole. These relations are shown to be a consequence of the hidden
$E_{8(+8)}$ symmetry in this sector of the solution space, and are distinct
from the usual "Smarr-type" formulas that can be derived from the first law of
black hole mechanics. We also derive the "physical process" version of this
first law applicable to a general stationary black hole spacetime without any
symmetry assumptions other than stationarity, allowing in particular arbitrary
horizon topologies. The work terms in the first law exhibit the topology of the
horizon via the intersection numbers between cycles of various dimensions.
| [
{
"created": "Mon, 16 Apr 2012 09:37:31 GMT",
"version": "v1"
},
{
"created": "Thu, 24 May 2012 09:48:19 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Aug 2012 11:59:23 GMT",
"version": "v3"
}
] | 2015-06-04 | [
[
"Hollands",
"Stefan",
""
]
] | We consider stationary, non-extremal black holes in 11-dimensional supergravity having isometry group $\mathbb{R} \times U(1)^8$. We prove that such a black hole is uniquely specified by its angular momenta, its electric charges associated with the various 7-cycles in the manifold, together with certain moduli and vector valued winding numbers characterizing the topological nature of the spacetime and group action. We furthermore establish interesting, non-trivial, relations between the thermodynamic quantities associated with the black hole. These relations are shown to be a consequence of the hidden $E_{8(+8)}$ symmetry in this sector of the solution space, and are distinct from the usual "Smarr-type" formulas that can be derived from the first law of black hole mechanics. We also derive the "physical process" version of this first law applicable to a general stationary black hole spacetime without any symmetry assumptions other than stationarity, allowing in particular arbitrary horizon topologies. The work terms in the first law exhibit the topology of the horizon via the intersection numbers between cycles of various dimensions. |
2308.05197 | Juan M. Z\'arate Pretel | Juan M. Z. Pretel, Takol Tangphati and Ayan Banerjee | Relativistic structure of charged quark stars in energy-momentum squared
gravity | 15 pages, 6 figures, 2 tables. Version accepted in Annals of Physics | Ann. Phys. 458 (2023) 169440 | 10.1016/j.aop.2023.169440 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the context of energy-momentum squared gravity (EMSG), where
non-linear matter contributions appear in the gravitational action, we derive
the modified TOV equations describing the hydrostatic equilibrium of charged
compact stars. We adopt two different choices for the matter Lagrangian density
($\mathcal{L}_m= p$ versus $\mathcal{L}_m= -\rho$) and investigate the impact
of each one on stellar structure. Furthermore, considering a charge profile
where the electric charge density $\rho_{\rm ch}$ is proportional to the
standard energy density $\rho$, we solve numerically the stellar structure
equations in order to obtain the mass-radius diagrams for the MIT bag model
equation of state (EoS). For $\mathcal{L}_m= p$ and given a specific value of
$\beta$ (including the uncharged case when $\beta= 0$), the maximum-mass values
increase (decrease) substantially as the gravity model parameter $\alpha$
becomes more negative (positive). However, for uncharged configurations and
considering $\mathcal{L}_m= -\rho$, our numerical results reveal that when we
increase $\alpha$ (from a negative value) the maximum mass first increases and
after reaching a maximum value it starts to decrease. Remarkably, this makes it
a less trivial behavior than that caused by the first choice when we take into
account the presence of electric charge ($\beta \neq 0$).
| [
{
"created": "Wed, 9 Aug 2023 19:34:41 GMT",
"version": "v1"
}
] | 2023-08-21 | [
[
"Pretel",
"Juan M. Z.",
""
],
[
"Tangphati",
"Takol",
""
],
[
"Banerjee",
"Ayan",
""
]
] | Within the context of energy-momentum squared gravity (EMSG), where non-linear matter contributions appear in the gravitational action, we derive the modified TOV equations describing the hydrostatic equilibrium of charged compact stars. We adopt two different choices for the matter Lagrangian density ($\mathcal{L}_m= p$ versus $\mathcal{L}_m= -\rho$) and investigate the impact of each one on stellar structure. Furthermore, considering a charge profile where the electric charge density $\rho_{\rm ch}$ is proportional to the standard energy density $\rho$, we solve numerically the stellar structure equations in order to obtain the mass-radius diagrams for the MIT bag model equation of state (EoS). For $\mathcal{L}_m= p$ and given a specific value of $\beta$ (including the uncharged case when $\beta= 0$), the maximum-mass values increase (decrease) substantially as the gravity model parameter $\alpha$ becomes more negative (positive). However, for uncharged configurations and considering $\mathcal{L}_m= -\rho$, our numerical results reveal that when we increase $\alpha$ (from a negative value) the maximum mass first increases and after reaching a maximum value it starts to decrease. Remarkably, this makes it a less trivial behavior than that caused by the first choice when we take into account the presence of electric charge ($\beta \neq 0$). |
gr-qc/9906045 | Arbab I. Arbab | Arbab I. Arbab | FRW-Type Universe With Vacuum Energy Density | A revised version, 8 pages Latex, submitted to Gravitation and
Cosmology | Grav.Cosmol. 8 (2002) 227-231 | null | null | gr-qc | null | We have considered a cosmological model with a cosmological constant of the
form $\Lambda=3\alpha\frac{\dot R^2}{R^2}+\bt\frac{\ddot R}{R} \alpha, \bt=\rm
const.$ The cosmological constant is found to decrease as $t^{-2}$ and the rate
of particle creation is smaller than the Steady State value. We have found that
this behavior gives $\frac{\Lambda_{Pl}}{\Lambda_p}=10^{120}$ where
$\Lambda_{Pl}$ is the value of $\Lambda$ at Planck time. Solutions with
$\bt=3\alpha$ in the radiation dominated era and $\bt=6\alpha$ in the matter
dominated era are equivalent to the FRW results. We have found an inflationary
solution of the de-Sitter type with $\bt=3-3\alpha$. Some problems of the
Standard Model may be resolved with the presence of the above cosmological
constant in the Einstein's equation. Since observations suggest a contribution
of the vacuum energy density in the range $0.40<\Omega^\Lambda<0.76$, one gets
$4<\beta<12$. If $\alpha=0$ the minimum age of the universe is found to be
$H_p^{-1}$ ($H_p$ is the present Hubble constant) with $\beta=\infty$.
| [
{
"created": "Mon, 14 Jun 1999 22:06:05 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jun 1999 16:03:32 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Oct 1999 13:01:34 GMT",
"version": "v3"
},
{
"created": "Thu, 24 May 2001 13:39:30 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Arbab",
"Arbab I.",
""
]
] | We have considered a cosmological model with a cosmological constant of the form $\Lambda=3\alpha\frac{\dot R^2}{R^2}+\bt\frac{\ddot R}{R} \alpha, \bt=\rm const.$ The cosmological constant is found to decrease as $t^{-2}$ and the rate of particle creation is smaller than the Steady State value. We have found that this behavior gives $\frac{\Lambda_{Pl}}{\Lambda_p}=10^{120}$ where $\Lambda_{Pl}$ is the value of $\Lambda$ at Planck time. Solutions with $\bt=3\alpha$ in the radiation dominated era and $\bt=6\alpha$ in the matter dominated era are equivalent to the FRW results. We have found an inflationary solution of the de-Sitter type with $\bt=3-3\alpha$. Some problems of the Standard Model may be resolved with the presence of the above cosmological constant in the Einstein's equation. Since observations suggest a contribution of the vacuum energy density in the range $0.40<\Omega^\Lambda<0.76$, one gets $4<\beta<12$. If $\alpha=0$ the minimum age of the universe is found to be $H_p^{-1}$ ($H_p$ is the present Hubble constant) with $\beta=\infty$. |
1812.00435 | Tosaporn Angsachon | T.Angsachon, P.Cheewaphutthisakun, R.Dhanawittayapol, S.N.Manida | The Killing vectors and symmetry in $R$-spacetime | Latex, 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the Killing vector will be constructed for the $R$-spacetime
metric. The symmetry transformations corresponding to this vectors are obtained
explicitly. Their coincidence with the transformations of the Poincar\'e group
in a small neighborhood of the world point is shown.
| [
{
"created": "Sun, 2 Dec 2018 17:56:08 GMT",
"version": "v1"
}
] | 2018-12-04 | [
[
"Angsachon",
"T.",
""
],
[
"Cheewaphutthisakun",
"P.",
""
],
[
"Dhanawittayapol",
"R.",
""
],
[
"Manida",
"S. N.",
""
]
] | In this paper, the Killing vector will be constructed for the $R$-spacetime metric. The symmetry transformations corresponding to this vectors are obtained explicitly. Their coincidence with the transformations of the Poincar\'e group in a small neighborhood of the world point is shown. |
1603.07360 | Hyerim Noh | Jai-chan Hwang, Hyerim Noh, J'ulio Fabris, Oliver F. Piattella,
Winfried Zimdahl | Newtonian hydrodynamic equations with relativistic pressure and velocity | 4 pages, no figure | null | 10.1088/1475-7516/2016/07/046 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new approximation to include fully general relativistic pressure
and velocity in Newtonian hydrodynamics. The energy conservation, momentum
conservation and two Poisson's equations are consistently derived from
Einstein's gravity in the zero-shear gauge assuming weak gravity and
action-at-a-distance limit. The equations show proper special relativity limit
in the absence of gravity. Our approximation is complementary to the
post-Newtonian approximation and the equations are valid in fully nonlinear
situations.
| [
{
"created": "Wed, 16 Mar 2016 08:44:03 GMT",
"version": "v1"
}
] | 2016-08-03 | [
[
"Hwang",
"Jai-chan",
""
],
[
"Noh",
"Hyerim",
""
],
[
"Fabris",
"J'ulio",
""
],
[
"Piattella",
"Oliver F.",
""
],
[
"Zimdahl",
"Winfried",
""
]
] | We present a new approximation to include fully general relativistic pressure and velocity in Newtonian hydrodynamics. The energy conservation, momentum conservation and two Poisson's equations are consistently derived from Einstein's gravity in the zero-shear gauge assuming weak gravity and action-at-a-distance limit. The equations show proper special relativity limit in the absence of gravity. Our approximation is complementary to the post-Newtonian approximation and the equations are valid in fully nonlinear situations. |
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