Unnamed: 0 int64 0 41k | title stringlengths 4 274 | category stringlengths 5 18 | summary stringlengths 22 3.66k | theme stringclasses 8
values |
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7,100 | Non-Minimally Coupled Scalar Field and Ashtekar Variables | gr-qc | The non-minimal coupling of a scalar field is considered in the framework of
Ashtekar's new variables formulation of gravity. A first order action
functional for this system is derived in which the field variables are a tetrad
field, and an SL(2,C) connection, together with the scalar field. The tetrad
field and the SL... | physics |
7,101 | Remarks on Pure Spin Connection Formulations of Gravity | gr-qc | In the derivation of a pure spin connection action functional for gravity two
methods have been proposed. The first starts from a first order lagrangian
formulation, the second from a hamiltonian formulation. In this note we show
that they lead to identical results for the specific cases of pure gravity with
or without... | physics |
7,102 | Nonsymmetric Gravity Theories: Inconsistencies and a Cure | gr-qc | Motivated by the apparent dependence of string $\sigma$--models on the sum of
spacetime metric and antisymmetric tensor fields, we reconsider gravity
theories constructed from a nonsymmetric metric. We first show that all such
"geometrical" theories homogeneous in second derivatives violate standard
physical requiremen... | physics |
7,103 | Degenerate Extensions of General Relativity | gr-qc | General relativity has previously been extended to incorporate degenerate
metrics using Ashtekar's hamiltonian formulation of the theory. In this letter,
we show that a natural alternative choice for the form of the hamiltonian
constraints leads to a theory which agrees with GR for non-degenerate metrics,
but differs i... | physics |
7,104 | The Spin Holonomy Group In General Relativity | gr-qc | It has recently been shown by Goldberg et al that the holonomy group of the
chiral spin-connection is preserved under time evolution in vacuum general
relativity. Here, the underlying reason for the time-independence of the
holonomy group is traced to the self-duality of the curvature 2-form for an
Einstein space. This... | physics |
7,105 | The No-Hair Theorem for the Abelian Higgs Model | gr-qc | We consider the general procedure for proving no-hair theorems for static,
spherically symmetric black holes. We apply this method to the abelian Higgs
model and find a proof of the no-hair conjecture that circumvents the
objections raised against the original proof due to Adler and Pearson. | physics |
7,106 | Gravitational Waves from an Axi-symmetric Source in the Nonsymmetric Grav. Theory | gr-qc | We examine gravitational waves in an isolated axi--symmetric reflexion
symmetric NGT system. The structure of the vacuum field equations is analyzed
and the exact solutions for the field variables in the metric tensor are found
in the form of expansions in powers of a radial coordinate. We find that in the
NGT axially ... | physics |
7,107 | The Dirac Equation Is Separable On The Dyon Black Hole Metric | gr-qc | Using the tetrad formalism, we carry out the separation of variables for the
massive complex Dirac equation in the gravitational and electromagnetic field
of a four-parameter (mass, angular momentum, electric and magnetic charges)
black hole. | physics |
7,108 | Centrifugal force in Kerr geometry | gr-qc | We have obtained the correct expression for the centrifugal force acting on a
particle at the equatorial circumference of a rotating body in the locally
non-rotating frame of the Kerr geometry. Using this expression for the
equilibrium of an element on the surface of a slowly rotating Maclaurin
spheroid, we obtain the ... | physics |
7,109 | Nonlinear Noise in Cosmology | gr-qc | This paper derives and analyzes exact, nonlocal Langevin equations
appropriate in a cosmological setting to describe the interaction of some
collective degree of freedom with a surrounding ``environment.'' Formally,
these equations are much more general, involving as they do a more or less
arbitrary ``system,'' charact... | physics |
7,110 | Stochastic Inflation:The Quantum Phase Space Approach | gr-qc | In this paper a quantum mechanical phase space picture is constructed for
coarse-grained free quantum fields in an inflationary Universe. The appropriate
stochastic quantum Liouville equation is derived. Explicit solutions for the
phase space quantum distribution function are found for the cases of power law
and expone... | physics |
7,111 | Quantum Gravity, the Origin of Time and Time's Arrow | gr-qc | The local Lorentz and diffeomorphism symmetries of Einstein's gravitational
theory are spontaneously broken by a Higgs mechanism by invoking a phase
transition in the early Universe, at a critical temperature $T_c$ below which
the symmetry is restored. The spontaneous breakdown of the vacuum state
generates an external... | physics |
7,112 | Results on exact solutions of low energy string theory | gr-qc | A family of solutions to low energy string theory is found. These solutions
represent waves traveling along "extremal black strings" | physics |
7,113 | Asymptotic Behavior of the $T^3 \times R$ Gowdy Spacetimes | gr-qc | We present new evidence in support of the Penrose's strong cosmic censorship
conjecture in the class of Gowdy spacetimes with $T^3$ spatial topology.
Solving Einstein's equations perturbatively to all orders we show that
asymptotically close to the boundary of the maximal Cauchy development the
dominant term in the exp... | physics |
7,114 | Semiclassical Effects and the Onset of Inflation | gr-qc | We present a class of exact solutions to the constraint equations of General
Relativity coupled to a Klein - Gordon field, these solutions being isotropic
but not homogeneous. We analyze the subsequent evolution of the consistent
Cauchy data represented by those solutions, showing that only certain special
initial cond... | physics |
7,115 | Euclidean Maxwell-Einstein Theory | gr-qc | After reviewing the context in which Euclidean propagation is useful we
compare and contrast Euclidean and Lorentzian Maxwell-Einstein theory and give
some examples of Euclidean solutions. | physics |
7,116 | Poincaré Gauge Theories for Lineal Garvity | gr-qc | We have shown that two of the most studied models of lineal gravities -
Liouville gravity and a ``string-inspired'' model exhibiting the main
characteristic features of a black-hole solution - can be formulated as gauge
invariant theories of the Poincar\'e group. The gauge invariant couplings to
matter (particles, scal... | physics |
7,117 | Clifford Algebra of Two-Forms, Conformal Structures and Field Equations | gr-qc | I review the equivalence between duality operators on two-forms and conformal
structures in four dimensions, from a Clifford algebra point of view (due to
Urbantke and Harnett). I also review an application, which leads to a set of
"neighbours" of Einstein's equations. An attempt to formulate reality
conditions for the... | physics |
7,118 | The Nordtvedt effect in the Trojan asteroids | gr-qc | Bounds to the Nordtvedt parameter are obtained from the motion of the first
twelve Trojan asteroids in the period 1906-1990. From the analysis performed,
we derive a value for the inverse of the Saturn mass 3497.80 \pm 0.81 and the
Nordtvedt parameter -0.56 \pm 0.48, from a simultaneous solution for all
asteroids. | physics |
7,119 | Canonical Quantum Gravity and the Problem of Time | gr-qc | This is the write-up of my lectures at the NATO Summer School held in
Salamanca in June 1992. The paper deals with the problem of time in quantum
gravity. All the major schemes are reviewed. Please note that the paper is in
two parts for ease of email transmission; this is part 1. The mailer from gr-qc
may further subd... | physics |
7,120 | Quantum Effects in Black Hole Interiors | gr-qc | The Weyl curvature inside a black hole formed in a generic collapse grows,
classically without bound, near to the inner horizon, due to partial absorption
and blueshifting of the radiative tail of the collapse. Using a spherical
model, we examine how this growth is modified by quantum effects of conformally
coupled mas... | physics |
7,121 | Cosmological Models in Two Spacetime Dimensions | gr-qc | Various physical properties of cosmological models in (1+1) dimensions are
investigated. We demonstrate how a hot big bang and a hot big crunch can arise
in some models. In particular, we examine why particle horizons do not occur in
matter and radiation models. We also discuss under what circumstances
exponential infl... | physics |
7,122 | Towards a Singularity-Proof Scheme in Numerical Relativity | gr-qc | Progress in numerical relativity has been hindered for 30 years because of
the difficulties of avoiding spacetime singularities in numerical evolution. We
propose a scheme which excises a region inside an apparent horizon containing
the singularity. Two major ingredients of the scheme are the use of a
horizon-locking c... | physics |
7,123 | Is Quantum Spacetime Foam Unstable? | gr-qc | A very simple wormhole geometry is considered as a model of a mode of
topological fluctutation in Planck-scale spacetime foam. Quantum dynamics of
the hole reduces to quantum mechanics of one variable, throat radius, and
admits a WKB analysis. The hole is quantum-mechanically unstable: It has no
bound states. Wormhole ... | physics |
7,124 | Self-Consistence of Semi-Classical Gravity | gr-qc | Simon argued that the semi-classical theory of gravity, unless with some of
its solutions excluded, is unacceptable for reasons of both self-consistency
and experiment, and that it has to be replaced by a constrained semi-classical
theory. We examined whether the evidence is conclusive. | physics |
7,125 | Path integration in relativistic quantum mechanics | gr-qc | The simple physics of a free particle reveals important features of the
path-integral formulation of relativistic quantum theories. The exact
quantum-mechanical propagator is calculated here for a particle described by
the simple relativistic action proportional to its proper time. This propagator
is nonvanishing outsi... | physics |
7,126 | SO(4) Invariant States in Quantum Cosmology | gr-qc | The phenomenon of linearisation instability is identified in models of
quantum cosmology that are perturbations of mini-superspace models. In
particular, constraints that are second order in the perturbations must be
imposed on wave functions calculated in such models. It is shown explicitly
that in the case of a model... | physics |
7,127 | Chern--Simons Gravity from 3+1 Dimensional Gravity | gr-qc | In the context of a Poincar\'e gauge theoretical formulation, pure gravity in
3+1-dimensions is dimensionally reduced to gravity in 2+1-dimensions with or
without cosmological constant $\Lambda$. The dimensional reductions are
consistent with the gauge symmetries, mapping ISO(3, 1) gauge transformations
into ISO(2,1) o... | physics |
7,128 | Einstein Equation with Quantum Corrections Reduced to Second Order | gr-qc | We consider the Einstein equation with first order (semiclassical) quantum
corrections. Although the quantum corrections contain up to fourth order
derivatives of the metric, the solutions which are physically relevant satisfy
a reduced equations which contain derivatives no higher than second order. We
obtain the redu... | physics |
7,129 | Mößbauer null redshift experiment II | gr-qc | Accurate limits for the violation of the Principle of Equivalence have been
found from the comparison of the redshifts of two identical nuclear species in
different chemical environments. | physics |
7,130 | D=3: Singularities in Gravitational Scattering of Scalar Waves | gr-qc | Family of exact spacetimes of D=3 Einstein gravity interacting with massless
scalar field is obtained by suitable dimensional reduction of a class of D=4
plane-symmetric Einstein vacua. These D=3 spacetimes describe collisions of
line-fronted asymptotically null excitations and are generically singular to
the future. T... | physics |
7,131 | Positivity of Entropy in the Semi-Classical Theory of Black Holes and Radiation | gr-qc | Quantum stress-energy tensors of fields renormalized on a Schwarzschild
background violate the classical energy conditions near the black hole.
Nevertheless, the associated equilibrium thermodynamical entropy $\Delta S$ by
which such fields augment the usual black hole entropy is found to be positive.
More precisely, t... | physics |
7,132 | Gauge (In)variance, Mass and Parity in D=3 Revisited | gr-qc | We analyze the degree of equivalence between abelian topologically massive,
gauge-invariant, vector or tensor parity doublets and their explicitly massive,
non-gauge, counterparts. We establish equivalence of field equations by
exploiting a generalized Stueckelberg invariance of the gauge systems. Although
the respecti... | physics |
7,133 | Weak-Field Gravity of Circular Cosmic Strings | gr-qc | A weak-field solution of Einstein's equations is constructed. It is generated
by a circular cosmic string externally supported against collapse. The solution
exhibits a conical singularity, and the corresponding deficit angle is the same
as for a straight string of the same linear energy density. This confirms the
defi... | physics |
7,134 | Inflating Lorentzian Wormholes | gr-qc | It has been speculated that Lorentzian wormholes of the Morris- Thorne type
might be allowed by the laws of physics at submicroscopic, e.g. Planck, scales
and that a sufficiently advanced civilization might be able to enlarge them to
classical size. The purpose of this paper is to explore the possibility that
inflation... | physics |
7,135 | Vacuum Polarisation and the Black Hole Singularity | gr-qc | In order to investigate the effects of vacuum polarisation on mass inflation
singularities, we study a simple toy model of a charged black hole with cross
flowing radial null dust which is homogeneous in the black hole interior. In
the region $r^2 \ll e^2$ we find an approximate analytic solution to the
classical field... | physics |
7,136 | What can we learn from the study of non-perturbative quantum general relativity? | gr-qc | I attempt to answer the question of the title by giving an annotated list of
the major results achieved, over the last six years, in the program to
construct quantum general relativity using the Ashtekar variables and the loop
representation. A summary of the key open problems is also included. Also
included are exposi... | physics |
7,137 | Quantum Gravity by the Complex Canonical Formulation | gr-qc | The basic features of the complex canonical formulation of general relativity
and the recent developments in the quantum gravity program based on it are
reviewed. The exposition is intended to be complementary to the review articles
available already and some original arguments are included. In particular the
conventio... | physics |
7,138 | Gravitational Waves in the Nonsymmetric Gravitational Theory | gr-qc | We prove that the flux of gravitational radiation from an isolated source in
the Nonsymmetric Gravitational Theory is identical to that found in Einstein's
General Theory of Relativity. | physics |
7,139 | Tunneling in Anisotropic Cosmological Models | gr-qc | Tunneling rate is investigated in homogenous and anisotropic cosmologies. The
calculations is done by two methods: Euclidean and Hamiltonian approaches. It
is found that the probability decreases exponentialy as anisotropy is
increased. | physics |
7,140 | Spin effects in the inspiral of coalescing compact binaries | gr-qc | We derive the contributions of spin-orbit and spin-spin coupling to the
gravitational radiation from coalescing binary systems of spinning compact
objects. We calculate spin effects in the symmetric, trace-free radiative
multipoles that determine the gravitational waveform, and the rate of energy
loss. Assuming a balan... | physics |
7,141 | Chaotic Friedmann-Robertson-Walker Cosmology | gr-qc | We show that the dynamics of a spatially closed Friedmann - Robertson -
Walker Universe conformally coupled to a real, free, massive scalar field, is
chaotic, for large enough field amplitudes. We do so by proving that this
system is integrable under the adiabatic approximation, but that the
corresponding KAM tori brea... | physics |
7,142 | Cosmic Censorship in 2-Dimensional Dilaton Gravity | gr-qc | The global structure of 2-dimensional dilaton gravity is studied, attending
in particular to black holes and singularities. A gravitational energy is
defined and shown to be positive at spatial singularities and negative at
temporal singularities. Trapped points are defined, and it is shown that
spatial singularities a... | physics |
7,143 | Galilean Theories of Gravitation | gr-qc | A generalization of Newtonian gravitation theory is obtained by a suitable
limiting procedure from the ADM action of general relativity coupled to a
mass-point. Three particular theories are discussed and it is found that two of
them are invariant under an extended Galilei gauge group. | physics |
7,144 | Exotic Differentiable Structures and General Relativity | gr-qc | We review recent developments in differential topology with special concern
for their possible significance to physical theories, especially general
relativity. In particular we are concerned here with the discovery of the
existence of non-standard (``fake'' or ``exotic'') differentiable structures on
topologically sim... | physics |
7,145 | Quantum Vacuum Instability Near Rotating Stars | gr-qc | We discuss the Starobinskii-Unruh process for the Kerr black hole. We show
how this effect is related to the theory of squeezed states. We then consider a
simple model for a highly relativistic rotating star and show that the
Starobinskii-Unruh effect is absent. | physics |
7,146 | Dark Matter and Non-Newtonian Gravity From General Relativity on a Stringy Background | gr-qc | An exact solution of Einstein's field equations for a static spherically
symmetric medium with a radially boost invariant energy-momentum tensor is
presented. In the limit of an equation of state corresponding to a distribution
of radially directed strings there is a $1/r$ correction to Newton's force law.
At large dis... | physics |
7,147 | On Cosmological Isotropy, Quantum Cosmology and the Weyl Curvature Hypothesis | gr-qc | The increasing entropy, large-scale isotropy and approximate flatness of the
universe are considered in the context of signature change, which is a
classical model of quantum tunnelling in quantum cosmology. The signature
change hypothesis implies an initial inflationary epoch, the magnetic half of
the Weyl curvature h... | physics |
7,148 | Weak-Field Gravity of Revolving Circular Cosmic Strings | gr-qc | A weak-field solution of Einstein's equations is constructed. It is generated
by a circular cosmic string revolving in its plane about the centre of the
circle. (The revolution is introduced to prevent the string from collapsing.)
This solution exhibits a conical singularity, and the corresponding deficit
angle is the ... | physics |
7,149 | A Nonlinear Model of a Quantum Minisuperspace System with Back Reaction | gr-qc | We consider the quantum evolution of the space-independent mode of a $\lambda
{\phi}^4$ theory as a minisuperspace in the space of all $\phi$. The motion of
the wave packet in the minisuperspace is then compared to the motion of a wave
packet in a larger minisuperspace consisting of the original minisuperspace
plus one... | physics |
7,150 | Collisions of Einstein-Conformal Scalar Waves | gr-qc | A large class of solutions of the Einstein-conformal scalar equations in
D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic
conformal scalar waves and are generated from Einstein-minimally coupled scalar
spacetimes via a (generalized) Bekenstein transformation. Particular emphasis
is given to the... | physics |
7,151 | Inhomogeneous and anisotropic cosmologies | gr-qc | This is a review of cosmological models prepared for the Pont d'Oye workshop
on the origin of structure in the universe. The classes of models are discussed
in turn, and then some of their uses are considered. | physics |
7,152 | Anisotropic and inhomogeneous cosmologies | gr-qc | This review was given at the 65th birthday meeting of D.W. Sciama, The
Renaissance of General Relativity and Cosmology, to be published by Cambridge
University Press. It presents progress in the understanding of non-standard
relativistic cosmologies during Sciama's career, organized by the areas of
application rather t... | physics |
7,153 | (1+1)-Dimensional Methods for General Relativity | gr-qc | This is an article contributed to the Brill Festschrift, in honor of the 60th
birthday of Prof. D.R. Brill, which will appear in the Vol.2 of the Proceedings
of the International Symposia on Directions in General Relativity. In this
article we present the (1+1)-dimensional method for studying general relativity
of 4-di... | physics |
7,154 | Bianchi Cosmological Models and Gauge Symmetries | gr-qc | We analyze carefully the problem of gauge symmetries for Bianchi models, from
both the geometrical and dynamical points of view. Some of the geometrical
definitions of gauge symmetries (=``homogeneity preserving diffeomorphisms'')
given in the literature do not incorporate the crucial feature that local gauge
transform... | physics |
7,155 | Event horizons and apparent horizons in spherically symmetric geometries | gr-qc | Spherical configurations that are very massive must be surrounded by apparent
horizons. These in turn, when placed outside a collapsing body, must propagate
outward with a velocity equal to the velocity of radially outgoing photons.
That proves, within the framework of (1+3) formalism and without resorting to
the Birkh... | physics |
7,156 | Time Symmetric Quantum Cosmology and Our Universe | gr-qc | We investigate the time neutral formulation of quantum cosmology of Gell-Mann
and Hartle. In particular we study the proposal discussed by them that our
Universe corresponds to the time symmetric decoherence functional with initial
and final density matrix of low entropy. We show that our Universe does not
correspond t... | physics |
7,157 | Decoherence Functional and Probability Interpretation | gr-qc | We confirm that the diagonal elements of the Gell-Mann and Hartle's
decoherence decoherence functional are equal to the relative frequencies of the
results of many identical experiments, when a set of alternative histories
decoheres. We consider both cases of the pure and mixed initial states. | physics |
7,158 | Cosmology, Oscillating Physics and Oscilllating Biology | gr-qc | According to recent reports there is an excess correlation and an apparent
regularity in the galaxy one-dimensional polar distribution with a
characteristic scale of 128 $h^{-1}$ Mpc. This aparent spatial periodicity can
be naturally explained by a time oscillation of the gravitational constant $G$.
On the other hand, ... | physics |
7,159 | Comments on Closed Bianchi Models | gr-qc | We show several kinematical properties that are intrinsic to the Bianchi
models with compact spatial sections. Especially, with spacelike hypersurfaces
being closed, (A) no anisotropic expansion is allowed for Bianchi type V and
VII(A\not=0), and (B) type IV and VI(A\not=0,1) does not exist. In order to
show them, we p... | physics |
7,160 | On the configuration space topology in general relativity | gr-qc | The configuration-space topology in canonical General Relativity depends on
the choice of the initial data 3-manifold. If the latter is represented as a
connected sum of prime 3-manifolds, the topology receives contributions from
all configuration spaces associated to each individual prime factor. There are
by now stro... | physics |
7,161 | An Anisotropic Wormhole:TUNNELLING in Time and Space | gr-qc | We discuss the structure of a gravitational euclidean instanton obtained
through coupling of gravity to electromagnetism. Its topology at fixed $t$ is
$S^1\times S^2$. This euclidean solution can be interpreted as a tunnelling to
a hyperbolic space (baby universe) at $t=0$ or alternatively as a static
wormhole that joi... | physics |
7,162 | Singularity Free Inhomogeneous Cosmological Stiff Fluid Models | gr-qc | We present a singularity free class of inhomogeneous cylindrical universes
filled with stiff perfect fluid $(\rho = p)$. Its matter free $ (\rho = 0)$
limit yield two distinct vacuum spacetimes which can be considered as analogues
of Kasner solution for inhomogeneous singularity free spacetime. | physics |
7,163 | Complex Numbers, Quantum Mechanics and the Beginning of Time | gr-qc | A basic problem in quantizing a field in curved space is the decomposition of
the classical modes in positive and negative frequency. The decomposition is
equivalent to a choice of a complex structure in the space of classical
solutions. In our construction the real tunneling geometries provide the link
between the thi... | physics |
7,164 | Two-loop effective potential in quantum field theory in curved space-time | gr-qc | The method of the calculation of effective potential (in linear curvature
approximation and at any loop) in massless gauge theory in curved space- time
by the direct solution of RG equation is given.The closed expression for
two-loop effective potential is obtained.Two-loop effective potential in scalar
self-interactin... | physics |
7,165 | The renormalization group for non-renormalizable theories: Einstein gravity with a scalar field | gr-qc | We develop a renormalization-group formalism for non-renormalizable theories
and apply it to Einstein gravity theory coupled to a scalar field with the
Lagrangian $L=\sqrt{g} [R U(\phi)-{1/2} G(\phi) g^{\mu\nu} \partial_{\mu}\phi
\partial_{\nu}\phi- V(\phi)]$, where $U(\phi), G(\phi)$ and $V(\phi)$ are
arbitrary functi... | physics |
7,166 | The Structure of Naked Singularity in Self-similar Gravitational Collapse II | gr-qc | Generalizing the results of Joshi and Dwivedi in Commun.Math.Phys. 146, p.333
(1992), it is pointed out that strong curvature naked singularities could occur
in the self-similar gravitational collapse of any form of matter satisfying the
weak energy condition for the positivity of mass-energy density. | physics |
7,167 | Cosmology with Nonminimal Derivative Couplings | gr-qc | We study a theory which generalizes the nonminimal coupling of matter to
gravity by including derivative couplings. This leads to several interesting
new dynamical phenomena in cosmology. In particular, the range of parameters in
which inflationary attractors exist is greatly expanded. We also numerically
integrate the... | physics |
7,168 | Geometry of the 2+1 Black Hole | gr-qc | The geometry of the spinning black holes of standard Einstein theory in 2+1
dimensions, with a negative cosmological constant and without couplings to
matter, is analyzed in detail. It is shown that the black hole arises from
identifications of points of anti-de Sitter space by a discrete subgroup of
$SO(2,2)$. The gen... | physics |
7,169 | Decoherence of Correlation Histories | gr-qc | We use a $\lambda\Phi^4$ scalar quantum field theory to illustrate a new
approach to the study of quantum to classical transition. In this approach, the
decoherence functional is employed to assign probabilities to consistent
histories defined in terms of correlations among the fields at separate points,
rather than th... | physics |
7,170 | The quantum behavior of general time dependent quadratic systems linearly coupled to a bath | gr-qc | In this paper we solve for the quantum propagator of a general time dependent
system quadratic in both position and momentum, linearly coupled to an infinite
bath of harmonic oscillators. We work in the regime where the quantum optical
master equation is valid. We map this master equation to a Schroedinger
equation on ... | physics |
7,171 | Quantum Cosmology | gr-qc | An elementary review of quantum cosmology. (Talk given at Texas/Pascos 1992
at Berkeley) | physics |
7,172 | Proof of the Generalized Second Law for Quasistationary Semiclassical Black Holes | gr-qc | A simple direct explicit proof of the generalized second law of black hole
thermodynamics is given for a quasistationary semiclassical black hole. | physics |
7,173 | The Initial Value Problem in Light of Ashtekar's Variables | gr-qc | The form of the initial value constraints in Ashtekar's hamiltonian
formulation of general relativity is recalled, and the problem of solving them
is compared with that in the traditional metric variables. It is shown how the
general solution of the four diffeomorphism constraints can be obtained
algebraically provided... | physics |
7,174 | Fluctuation, Dissipation and Irreversibility in Cosmology | gr-qc | We discuss the appearance of time-asymmetric behavior in physical processes
in cosmology and in the dynamics of the Universe itself. We begin with an
analysis of the nature and origin of irreversibility in well-known physical
processes such as dispersion, diffusion, dissipation and mixing, and make the
distinction betw... | physics |
7,175 | Symmetric solutions of Einstein-Yang-Mills equations | gr-qc | Symmetric gauge fields and invariant metrics in homogeneous spaces are found.
Their use for finding exact solutions of the Einstein-Yang-Mills (EYM)
equations is discussed. | physics |
7,176 | Brill Waves | gr-qc | Brill waves are the simplest (non-trivial) solutions to the vacuum
constraints of general relativity. They are also rich enough in structure to
allow us believe that they capture, at least in part, the generic properties of
solutions of the Einstein equations. As such, they deserve the closest
attention. This article i... | physics |
7,177 | Minisuperspace as a Quantum Open System | gr-qc | We trace the development of ideas on dissipative processes in chaotic
cosmology and on minisuperspace quantum cosmology from the time Misner proposed
them to current research. We show 1) how the effect of quantum processes like
particle creation in the early universe can address the issues of the isotropy
and homogenei... | physics |
7,178 | Minisuperspaces: Symmetries and Quantization | gr-qc | In several of the class A Bianchi models, minisuperspaces admit symmetries.
It is pointed out that they can be used effectively to complete the Dirac
quantization program. The resulting quantum theory provides a useful platform
to investigate a number of conceptual and technical problems of quantum
gravity. | physics |
7,179 | Minisuperspaces: Observables and Quantization | gr-qc | A canonical transformation is performed on the phase space of a number of
homogeneous cosmologies to simplify the form of the scalar (or, Hamiltonian)
constraint. Using the new canonical coordinates, it is then easy to obtain
explicit expressions of Dirac observables, i.e.\ phase space functions which
commute weakly wi... | physics |
7,180 | Karolyhazy's quantum space-time generates neutron star density in vacuum | gr-qc | By simple arguments, we have shown that Karolyhazy's model overestimates the
quantum uncertainty of the space-time geometry and leads to absurd physical
consequences. The given model can thus not account for gradual violation of
quantum coherence and can not predict tiny experimental effects either. | physics |
7,181 | Quantum and Thermal Fluctuations, Uncertainty Principle, Decoherence and Classicality* | gr-qc | We scrutize the commonly used criteria for classicality and examine their
underlying issues. The two major issues we address here are that of decoherence
and fluctuations. We borrow the insights gained in the study of the
semiclassical limit of quantum cosmology to discuss the three criteria of
classicality for a quant... | physics |
7,182 | Critical Dynamics in the Early Universe | gr-qc | Methods and concepts for the study of phase transitions mediated by a
time-dependent order-parameter field in curved spacetimes are discussed. A
practical example is the derivation of an effective (quasi-)potential for the
description of `slow-roll' inflation in the early universe. We first summarize
our early results ... | physics |
7,183 | Quantum Statistical Processes in the Early Universe | gr-qc | We show how the concept of quantum open system and the methods in
non-equilibrium statistical mechanics can be usefully applied to studies of
quantum statistical processes in the early universe. We first sketch how noise,
fluctuation, dissipation and decoherence processes arise in a wide range of
cosmological problems.... | physics |
7,184 | Do Black Holes Exist? | gr-qc | The problem of information loss in black hole formation and the associated
violations of basic laws of physics, such as conservation of energy, causality
and unitarity, are avoided in the nonsymmetric gravitational theory, if the NGT
charge of a black hole and its mass satisfy an inequality that does not violate
any kn... | physics |
7,185 | Symmetries of the Einstein Equations | gr-qc | Generalized symmetries of the Einstein equations are infinitesimal
transformations of the spacetime metric that formally map solutions of the
Einstein equations to other solutions. The infinitesimal generators of these
symmetries are assumed to be local, \ie at a given spacetime point they are
functions of the metric a... | physics |
7,186 | On the Cosmology of Massive Vector Fields with SO(3) Global Symmetry | gr-qc | A relevant reference ([14]) has been added. | physics |
7,187 | Quantum Effects In Cosmology | gr-qc | Contents:
Introduction. The Present State of the Universe.
What Can We Expect From a Complete Cosmological Theory?
An Overview of Quantum Effects in Cosmology.
Parametric (Superadiabatic) Amplification of Classical Waves.
Graviton Creation in the Inflationary Universe.
Quantum States of a Harmonic Oscillato... | physics |
7,188 | Motion and Trajectories of Particles Around Three-Dimensional Black Holes | gr-qc | The motion of relativistic particles around three dimensional black holes
following the Hamilton-Jacobi formalism is studied. It follows that the
Hamilton-Jacobi equation can be separated and reduced to quadratures in analogy
with the four dimensional case. It is shown that: a) particles are trapped by
the black hole i... | physics |
7,189 | General Laws of Black-Hole Dynamics | gr-qc | A general definition of a black hole is given, and general `laws of
black-hole dynamics' derived. The definition involves something similar to an
apparent horizon, a trapping horizon, defined as a hypersurface foliated by
marginal surfaces of one of four non-degenerate types, described as future or
past, and outer or i... | physics |
7,190 | No Superluminal Expansion of the Universe | gr-qc | The apparent superluminal growth in the size of a sufficiently large part of
the universe can be ascribed to the special relativistic effect of time
dilation. | physics |
7,191 | Conformal Fourth-Rank Gravity | gr-qc | We consider the consequences of describing the metric properties of space-
time through a quartic line element $ds^4=G_{\mu\nu\lambda\rho}dx^\mu dx^\nu
dx^\lambda dx^\rho$. The associated "metric" is a fourth-rank tensor
$G_{\mu\nu\lambda\rho}$. We construct a theory for the gravitational field
based on the fourth-rank... | physics |
7,192 | The Extended Loop Group: An Infinite Dimensional Manifold Associated with the Loop Space | gr-qc | A set of coordinates in the non parametric loop-space is introduced. We show
that these coordinates transform under infinite dimensional linear
representations of the diffeomorphism group. An extension of the group of loops
in terms of these objects is proposed. The enlarged group behaves locally as an
infinite dimensi... | physics |
7,193 | The Construction of Sorkin Triangulations | gr-qc | Some time ago, Sorkin (1975) reported investigations of the time evolution
and initial value problems in Regge calculus, for one triangulation each of the
manifolds $R*S^3$ and $R^4$. Here we display the simple, local characteristic
of those triangulations which underlies the structure found by Sorkin, and
emphasise it... | physics |
7,194 | Torsion and Nonmetricity in Scalar-Tensor Theories of Gravity | gr-qc | We show that the gravitational field equations derived from an action
composed of i) an arbitrary function of the scalar curvature and other scalar
fields plus ii) connection-independent kinetic and source terms, are identical
whether one chooses nonmetricity to vanish and have non-zero torsion or vice
versa. | physics |
7,195 | Maxwell Fields in Spacetimes Admitting Non-Null Killing Vectors | gr-qc | We consider source-free electromagnetic fields in spacetimes possessing a
non-null Killing vector field, $\xi^a$. We assume further that the
electromagnetic field tensor, $F_{ab}$, is invariant under the action of the
isometry group induced by $\xi^a$. It is proved that whenever the two
potentials associated with the e... | physics |
7,196 | The Isaacson expansion in quantum cosmology | gr-qc | This paper is an application of the ideas of the Born-Oppenheimer (or
slow/fast) approximation in molecular physics and of the Isaacson (or
short-wave) approximation in classical gravity to the canonical quantization of
a perturbed minisuperspace model of the kind examined by Halliwell and Hawking.
Its aim is the clari... | physics |
7,197 | Topologica Defects and Corrections to the Nambu Action | gr-qc | The effective action of a (1+2)-dimensional defect is obtained as an
expansion in powers of the thickness.Considering non-straight solutions as the
zero order term, the corrections to the Nambu action are found to depend on the
curvature scalar and on the gaussian curvature . | physics |
7,198 | Wave Functions of the Induced 2D-Gravity | gr-qc | We consider the induced $2$d-gravity in the minisuperspace approach. The
general solution to the Wheeler-DeWitt equation is given in terms of different
kind of Bessel functions of purely real or imaginary orders. We study the
properties of the corresponding probability distribution finding a kind of
phase transition at... | physics |
7,199 | Clock Time and Entropy | gr-qc | Testable conditional probabilities appear to be restricted to single
hypersurfaces (marvelous moments) and depend only on stationary observables.
Observable evolution, such as a change of entropy, should be expressed as a
dependence upon clock time, not upon inaccessible coordinate time. | physics |
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