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<title>gr-qc updates on arXiv.org</title>
<link>http://arxiv.org/</link>
<description rdf:parseType="Literal">General Relativity and Quantum Cosmology (gr-qc) updates on the arXiv.org e-print archive</description>
<dc:language>en-us</dc:language>
<dc:date>2012-08-08T20:30:00-05:00</dc:date>
<dc:publisher>www-admin@arxiv.org</dc:publisher>
<dc:subject>General Relativity and Quantum Cosmology</dc:subject>
<syn:updateBase>1901-01-01T00:00+00:00</syn:updateBase>
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  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1515" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1523" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1548" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1572" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1606" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1660" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1666" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1673" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1702" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1002.2593" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1203.6478" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1205.1253" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1207.6243" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.0877" />
  <rdf:li rdf:resource="http://arxiv.org/abs/1208.1335" />
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<image rdf:about="http://arxiv.org/icons/sfx.gif">
<title>arXiv.org</title>
<url>http://arxiv.org/icons/sfx.gif</url>
<link>http://arxiv.org/</link>
</image>
<item rdf:about="http://arxiv.org/abs/1208.1515">
<title>On Consistent Theories of Massive Spin-2 Fields Coupled to Gravity. (arXiv:1208.1515v1 [hep-th])</title>
<link>http://arxiv.org/abs/1208.1515</link>
<description rdf:parseType="Literal">&lt;p&gt;We consider the issues that arise out of interpreting the ghost-free bimetric
theory as a theory of a spin-2 field coupled to gravity. This requires
identifying a gravitational metric and parameterizing deviations of the
resulting theory from general relativity. To this end, we first consider the
most general bimetric backgrounds for which a massless and a massive spin-2
fluctuation with Fierz-Pauli mass exist. These backgrounds coincide with
solutions in general relativity. Based on this, we obtain nonlinear extensions
of the massive and massless spin-2 fields. The background value of the
nonlinear massive field parameterizes generic deviations of the bimetric theory
from GR. It is also shown that the nonlinear massless field does not have
standard ghost-free matter couplings, and hence cannot represent the
gravitational metric. However, an appropriate gravitational metric can still be
identified in the weak gravity limit. Hence in the presence of other neutral
spin-2 fields, the weak gravity limit is crucial for compatibility with general
relativity. We also write down the action in terms of the nonlinear massive
spin-2 field and obtain its ghost-free couplings to matter. The discussion is
then generalized to multimetric theories.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Hassan_S/0/1/0/all/0/1&quot;&gt;S. F. Hassan&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Schmidt_May_A/0/1/0/all/0/1&quot;&gt;Angnis Schmidt-May&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Strauss_M/0/1/0/all/0/1&quot;&gt;Mikael von Strauss&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1523">
<title>Local cosmological effects of order H in the orbital motion of a binary system?. (arXiv:1208.1523v1 [gr-qc])</title>
<link>http://arxiv.org/abs/1208.1523</link>
<description rdf:parseType="Literal">&lt;p&gt;A two-body system hypothetically affected by an additional radial
acceleration H v_r, where v_r is the radial velocity of the binary&apos;s proper
orbital motion, would experience long-term temporal changes of both its
semimajor axis a and the eccentricity e qualitatively different from any other
standard competing effect for them. Contrary to what one might reasonably
expect, the analytical expressions of such rates do not vanish in the limit
M--&amp;gt; 0, where M is the mass of the primary, being independent of it. This is a
general requirement that any potentially viable physical mechanism able to
provide such a putative acceleration should meet. Nonetheless, if H had the
same value H_0 of the Hubble parameter at present epoch, such rates of change
would have magnitude close to the present-day level of accuracy in determining
planetary orbital motions in our Solar System. A tension with recent
observations may even be present for Mercury and Mars. However, general
relativity, applied to a localized gravitationally bound binary system immersed
in an expanding Friedmann-Lemaitre-Robertson-Walker, does not predict the
existence of such a putative radial acceleration at Newtonian level. Instead,
it was recently shown in literature that an acceleration of order H and
directed along the velocity v of the test particle occurs at post-Newtonian
level. We worked out its orbital effects finding well-behaved secular rates of
change for both a and e proportional to the Schwarzschild radius r_s of the
primary. Their magnitude is quite small: the rate of change of a amounts to
just 20 microns per century in our Solar System. Finally, we discussed certain
basic criteria of viability that modified models of gravity should generally
meet when their observable effects are calculated.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Iorio_L/0/1/0/all/0/1&quot;&gt;Lorenzo Iorio&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1548">
<title>Evolution of a universe filled with a causal viscous fluid. (arXiv:1208.1548v1 [gr-qc])</title>
<link>http://arxiv.org/abs/1208.1548</link>
<description rdf:parseType="Literal">&lt;p&gt;The behaviour of solutions to the Einstein equations with a causal viscous
fluid source is investigated. In this model we consider a spatially flat
Robertson-Walker metric, the bulk viscosity coefficient is related to the
energy density as $\zeta = \alpha \rho^{m}$, and the relaxation time is given
by $\zeta/\rho$. In the case $m = 1/2$ we find the exact solutions and we
verify whether they satisfy the energy conditions. Besides, we study
analytically the asymptotic stability of several families of solutions for
arbitrary $m$. We find that the qualitative asymptotic behaviour in the far
future is not altered by relaxation processes, but they change the behaviour in
the past, introducing singular instead of deflationary evolutions or making the
Universe bounce due to the violation of the energy conditions.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Chimento_L/0/1/0/all/0/1&quot;&gt;Luis P. Chimento&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Jakubi_A/0/1/0/all/0/1&quot;&gt;Alejandro S. Jakubi&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1572">
<title>Accretion of non-minimally coupled generalized Chaplygin gas into black holes. (arXiv:1208.1572v1 [gr-qc])</title>
<link>http://arxiv.org/abs/1208.1572</link>
<description rdf:parseType="Literal">&lt;p&gt;The mass evolution of Schwarzschild black holes by the absorption of scalar
fields is investigated in the scenario of the generalized Chaplygin gas (GCG).
The GCG works as a unification picture of dark matter plus dark energy that
naturally accelerates the expansion of the Universe. Through elements of the
quasi-stationary approach, we consider the mass evolution of Schwarzschild
black holes accreted by non-minimally coupled cosmological scalar fields
reproducing the dynamics of the GCG. As a scalar field non-minimally coupled to
the metrics, such an exotic content has been interconnected with accreting
black holes. The black hole increasing masses by the absorption of the gas
reflects some consistence of the accretion mechanism with the hypothesis of the
primordial origin of supermassive black holes. Our results effectively show
that the non-minimal coupling with the GCG dark sector accelerates the
increasing of black hole masses. Meanwhile some exotic features can also be
depicted for specific ranges of the non-minimal coupling in which the GCG
dynamics is substantially modified.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Rodrigues_M/0/1/0/all/0/1&quot;&gt;Manuela G. Rodrigues&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Bernardini_A/0/1/0/all/0/1&quot;&gt;Alex E. Bernardini&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1606">
<title>Light deflection in binary stars. (arXiv:1208.1606v1 [astro-ph.SR])</title>
<link>http://arxiv.org/abs/1208.1606</link>
<description rdf:parseType="Literal">&lt;p&gt;The light deflection of one component of a binary system due to the
gravitational field of the other component is investigated. While this
relativistic effect has not been observed thus far, the question arises that
whether this effect becomes detectable in view of todays high-precision
astrometry which soon will reach the microarcsecond level of accuracy. The
effect is studied and its observability is investigated. It turns out, that in
total there are about 1000 binaries having orbital parameters such that the
light deflection amounts to be at least 1 microarcsecond. Two stringent
criteria for the orbital parameters are presented, by means of which one can
easily determine the maximal value of light deflection effect for a given
binary system. It is found, that for relevant binaries their orbital parameters
must take rather extreme values in order to have a light deflection of the
order of a few microarcseconds. Only in a very few and rather extreme binary
systems the light deflection effect might be detectable by todays astrometry,
but their existence is highly improbable. Thus, the detection of this subtle
effect of relativity still remains a challenge for future astrometric missions.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/astro-ph/1/au:+Zschocke_S/0/1/0/all/0/1&quot;&gt;Sven Zschocke&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1660">
<title>Generalized Uncertainty Principle and the Ramsauer-Townsend Effect. (arXiv:1208.1660v1 [gr-qc])</title>
<link>http://arxiv.org/abs/1208.1660</link>
<description rdf:parseType="Literal">&lt;p&gt;The scattering cross section of electrons in noble gas atoms exhibits a
minimum value at electron energies of approximately 1eV. This is the
Ramsauer-Townsend effect. In this letter, we study the Ramsauer-Townsend effect
in the framework of the Generalized Uncertainty Principle.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Vahedi_J/0/1/0/all/0/1&quot;&gt;J. Vahedi&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Nozari_K/0/1/0/all/0/1&quot;&gt;Kourosh Nozari&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Pedram_P/0/1/0/all/0/1&quot;&gt;P. Pedram&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1666">
<title>Stability analysis of the cosmological solutions with induced gravity and scalar field on the brane. (arXiv:1208.1666v1 [gr-qc])</title>
<link>http://arxiv.org/abs/1208.1666</link>
<description rdf:parseType="Literal">&lt;p&gt;We study cosmological dynamics and phase space of a scalar field localized on
the DGP brane. We consider both the minimally and nonminimally coupled scalar
quintessence and phantom fields on the brane. In the nonminimal case, the
scalar field couples with induced gravity on the brane. We present a detailed
analysis of the critical points, their stability and late-time cosmological
viability of the solutions in the phase space of the model.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Nozari_K/0/1/0/all/0/1&quot;&gt;Kourosh Nozari&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Rajabi_F/0/1/0/all/0/1&quot;&gt;F. Rajabi&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Asadi_K/0/1/0/all/0/1&quot;&gt;K. Asadi&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1673">
<title>Covariant kinematics and gravitational bounce in Finsler space-times. (arXiv:1208.1673v1 [gr-qc])</title>
<link>http://arxiv.org/abs/1208.1673</link>
<description rdf:parseType="Literal">&lt;p&gt;The similarity between Finsler and Riemann geometry is an intriguing starting
point to extend general relativity. The lack of quadratic restriction over the
line element (color) naturally generalize the Riemannian case and breaks the
local and global symmetries of general relativity. We investigate the covariant
kinematics of a medium formed by a time-like congruence. After a brief view in
the general case we impose particular geometric restrictions to get some
analytic insight. Central role to our analysis plays the Lie derivative where
even in case of irrotational Killing vectors the bundle still deforms. We
demonstrate an example of an isotropic and exponentially expanding
cross-section that finally deflates or forms a caustic. Furthermore, using the
1+3 covariant formalism we investigate the expansion dynamics of the
congruence. For certain geometric restrictions we retrieve the Raychaudhuri
equation where a color-curvature coupling is revealed. The condition to prevent
the focusing of neighboring particles is given and is more likely to fulfilled
in highly curved regions. Then, we introduce the Levi-Civita connection for the
osculating Riemannian metric and develop a (spatially) isotropic and
homogeneous dust-like model with a non-singular bounce.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Kouretsis_A/0/1/0/all/0/1&quot;&gt;A.P.Kouretsis&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Stathakopoulos_M/0/1/0/all/0/1&quot;&gt;M.Stathakopoulos&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Stavrinos_P/0/1/0/all/0/1&quot;&gt;P.C.Stavrinos&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1702">
<title>Extracting Energy from an External Magnetic Field. (arXiv:1208.1702v1 [math-ph])</title>
<link>http://arxiv.org/abs/1208.1702</link>
<description rdf:parseType="Literal">&lt;p&gt;In this paper we describe the theory of a device that is able to extract
energy from an external magnetic field. The device is a cylindrical magnetic
insulator that once put in rotation makes electromagnetic angular momentum to
be stored in the electromagnetic field in contrary direction to the mechanical
angular momentum of the device. As a consequence due to total angular momentum
conservation the device increases its angular velocity (when {\epsilon}{\mu}&amp;gt;1)
Natural units are used in the paper and all conservation laws are rigorously
satisfied. The voltage generated by the device is found solving explicitly
Maxwell equations for rotating magnetic insulators in external fields, a
subject that have provoked lots of polemics in the literature and which we hope
to be here clarified due to our pedagogical presentation.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/math-ph/1/au:+Rodrigues_W/0/1/0/all/0/1&quot;&gt;Waldyr A. Rodrigues Jr.&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/math-ph/1/au:+Oliveira_E/0/1/0/all/0/1&quot;&gt;Edmundo Capelas de Oliveira&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1002.2593">
<title>Probabilistic time. (arXiv:1002.2593v3 [hep-th] UPDATED)</title>
<link>http://arxiv.org/abs/1002.2593</link>
<description rdf:parseType="Literal">&lt;p&gt;The concept of time emerges as an ordering structure in a classical
statistical ensemble. Probability distributions $p_\tau(t)$ at a given time $t$
obtain by integrating out the past and future. We discuss all-time probability
distributions that realize a unitary time evolution as described by rotations
of the real wave function $q_\tau(t)=\pm \sqrt{p_\tau(t)}$. We establish a map
to quantum physics and the Schr\&quot;odinger equation. Suitable classical
observables are mapped to quantum operators. The non-commutativity of the
operator product is traced back to the incomplete statistics of the local-time
subsystem. Our investigation of classical statistics is based on two-level
observables that take the values one or zero. Then the wave functions can be
mapped to elements of a Grassmann algebra. Quantum field theories for fermions
arise naturally from our formulation of probabilistic time.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Wetterich_C/0/1/0/all/0/1&quot;&gt;C. Wetterich&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1203.6478">
<title>An exact quantification of backreaction in relativistic cosmology. (arXiv:1203.6478v2 [gr-qc] UPDATED)</title>
<link>http://arxiv.org/abs/1203.6478</link>
<description rdf:parseType="Literal">&lt;p&gt;An important open question in cosmology is the degree to which the
Friedmann-Lemaitre-Robertson-Walker (FLRW) solutions of Einstein&apos;s equations
are able to model the large-scale behaviour of the locally inhomogeneous
observable universe. We investigate this problem by considering a range of
exact n-body solutions of Einstein&apos;s constraint equations. These solutions
contain discrete masses, and so allow arbitrarily large density contrasts to be
modelled. We restrict our study to regularly arranged distributions of masses
in topological 3-spheres. This has the benefit of allowing straightforward
comparisons to be made with FLRW solutions, as both spacetimes admit a discrete
group of symmetries. It also provides a time-symmetric hypersurface at the
moment of maximum expansion that allows the constraint equations to be solved
exactly. We find that when all the mass in the universe is condensed into a
small number of objects (&amp;lt;10) then the amount of backreaction in dust models
can be large, with O(1) deviations from the predictions of the corresponding
FLRW solutions. When the number of masses is large (&amp;gt;100), however, then our
measures of backreaction become small (&amp;lt;1%). This result does not rely on any
averaging procedures, which are notoriously hard to define uniquely in general
relativity, and so provides (to the best of our knowledge) the first exact and
unambiguous demonstration of backreaction in general relativistic cosmological
modelling. Discrete models such as these can therefore be used as laboratories
to test ideas about backreaction that could be applied in more complicated and
realistic settings.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Clifton_T/0/1/0/all/0/1&quot;&gt;Timothy Clifton&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Rosquist_K/0/1/0/all/0/1&quot;&gt;Kjell Rosquist&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Tavakol_R/0/1/0/all/0/1&quot;&gt;Reza Tavakol&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1205.1253">
<title>Testing Chern-Simons Modified Gravity with Gravitational-Wave Detections of Extreme-Mass-Ratio Binaries. (arXiv:1205.1253v2 [gr-qc] UPDATED)</title>
<link>http://arxiv.org/abs/1205.1253</link>
<description rdf:parseType="Literal">&lt;p&gt;[abridged] The detection of gravitational waves from extreme-mass-ratio
(EMRI) binaries, comprising a stellar-mass compact object orbiting around a
massive black hole, is one of the main targets for low-frequency
gravitational-wave detectors in space, like the Laser Interferometer Space
Antenna (LISA or eLISA/NGO). The long-duration gravitational-waveforms emitted
by such systems encode the structure of the strong field region of the massive
black hole, in which the inspiral occurs. The detection and analysis of EMRIs
will therefore allow us to study the geometry of massive black holes and
determine whether their nature is as predicted by General Relativity and even
to test whether General Relativity is the correct theory to describe the
dynamics of these systems. To achieve this, EMRI modeling in alternative
theories of gravity is required to describe the generation of gravitational
waves. In this paper, we explore to what extent EMRI observations with LISA or
eLISA/NGO might be able to distinguish between General Relativity and a
particular modification of it, known as Dynamical Chern-Simons Modified
Gravity. Our analysis is based on a parameter estimation study that uses
approximate gravitational waveforms obtained via a radiative-adiabatic method
and is restricted to a five-dimensional subspace of the EMRI configuration
space. This includes a Chern-Simons parameter that controls the strength of
gravitational deviations from General Relativity. We find that, if Dynamical
Chern-Simons Modified Gravity is the correct theory, an observatory like LISA
or even eLISA/NGO should be able to measure the Chern-Simons parameter with
fractional errors below 5%. If General Relativity is the true theory, these
observatories should put bounds on this parameter at the level xi^(1/4) &amp;lt; 10^4
km, which is four orders of magnitude better than current Solar System bounds.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Canizares_P/0/1/0/all/0/1&quot;&gt;Priscilla Canizares&lt;/a&gt; (1,2), &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Gair_J/0/1/0/all/0/1&quot;&gt;Jonathan R. Gair&lt;/a&gt; (1), &lt;a href=&quot;http://arxiv.org/find/gr-qc/1/au:+Sopuerta_C/0/1/0/all/0/1&quot;&gt;Carlos F. Sopuerta&lt;/a&gt; (2) ((1) IoA, Cambridge, (2) ICE, CSIC-IEEC)</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1207.6243">
<title>Complementarity, not Firewalls. (arXiv:1207.6243v2 [hep-th] UPDATED)</title>
<link>http://arxiv.org/abs/1207.6243</link>
<description rdf:parseType="Literal">&lt;p&gt;In this note I argue that a version of complementarity is possible which
evades the need for the &quot;firewalls&quot; recently proposed by Almheiri, Marolf,
Polchinski, and Sully to burn up observers falling into black hole horizons. In
particular I claim that it is consistent for an infalling observer to fall
through an &quot;old&quot; black hole horizon without burning up, without this observer
or any other seeing information loss or a violation of low energy effective
field theory in an unexpected place. The reason that AMPS find the opposite
conclusion is because they attempt to use low energy physics to translate
between the quantum mechanics of different observers rather than to describe
the experiments of only a single observer; I argue that this translation is
polluted by short-distance physics related to stretched horizons.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Harlow_D/0/1/0/all/0/1&quot;&gt;Daniel Harlow&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.0877">
<title>One-Loop Divergences in 6D Conformal Gravity. (arXiv:1208.0877v1 [hep-th] CROSS LISTED)</title>
<link>http://arxiv.org/abs/1208.0877</link>
<description rdf:parseType="Literal">&lt;p&gt;Using Exact Renormalization Group Equation approach and background field
method, we investigate the one-loop problem in a six-dimensional conformal
gravity theory whose Lagrangian takes the same form as holographic Weyl anomaly
of multiple coincident M5-branes. We choose the backgrounds to be the symmetric
Einstein spaces including S6, CP3, S2 \times S4, S2 \times CP2, S3 \times S3
and S2 \times S2 \times S2. Evaluating the functional sums gives power-law and
logarithmic divergences. We extract from the specific values of logarithmic
divergence on above backgrounds, the coefficient in front of Euler density and
two linear equations constraining the coefficients in front of three type-B
conformal invariants. As a test of the effectiveness of Exact Renormalization
Group Equation approach to quantum conformal gravity, we reexaminethe one-loop
problem in four-dimensional conformal gravity and confirm the logarithmic
divergence derived from generalized Schwinger-DeWitt method.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Pang_Y/0/1/0/all/0/1&quot;&gt;Yi Pang&lt;/a&gt;</dc:creator>
</item>
<item rdf:about="http://arxiv.org/abs/1208.1335">
<title>Observer dependence of bubble nucleation and Schwinger pair production. (arXiv:1208.1335v1 [hep-th] CROSS LISTED)</title>
<link>http://arxiv.org/abs/1208.1335</link>
<description rdf:parseType="Literal">&lt;p&gt;Pair production in a constant electric field is closely analogous to bubble
nucleation in a false vacuum. The classical trajectories of the pairs are
Lorentz invariant, but it appears that this invariance should be broken by the
nucleation process. Here, we use a model detector, consisting of other
particles interacting with the pairs, to investigate how pair production is
seen by different Lorentzian observers. We focus on the idealized situation
where a constant external electric field is present for an infinitely long
time, and we consider the in-vacuum state for a charged scalar field that
describes the nucleating pairs. The in-vacuum is defined in terms of modes
which are positive frequency in the remote past. Even though the construction
uses a particular reference frame and a gauge where the vector potential is
time dependent, we show explicitly that the resulting quantum state is Lorentz
invariant. We then introduce a &quot;detector&quot; particle which interacts with the
nucleated pairs, and show that all Lorentzian observers will see the particles
and antiparticles nucleating at rest in the detector&apos;s rest frame. Similar
conclusions are expected to apply to bubble nucleation in a sufficiently long
lived vacuum. We also comment on certain unphysical aspects of the Lorentz
invariant in-vacuum, associated with the fact that it contains an infinite
density of particles. This can be easily remedied by considering Lorentz
breaking initial conditions.
&lt;/p&gt;
</description>
<dc:creator> &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Garriga_J/0/1/0/all/0/1&quot;&gt;Jaume Garriga&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Kanno_S/0/1/0/all/0/1&quot;&gt;Sugumi Kanno&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Sasaki_M/0/1/0/all/0/1&quot;&gt;Misao Sasaki&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Soda_J/0/1/0/all/0/1&quot;&gt;Jiro Soda&lt;/a&gt;, &lt;a href=&quot;http://arxiv.org/find/hep-th/1/au:+Vilenkin_A/0/1/0/all/0/1&quot;&gt;Alexander Vilenkin&lt;/a&gt;</dc:creator>
</item>
</rdf:RDF>