title:
Regularization of second-order scalar perturbation produced by a
  point-particle with a nonlinear coupling

abstract:
  Accurate calculation of the motion of a compact object in a background
spacetime induced by a supermassive black hole is required for the future
detection of such binary systems by the gravitational-wave detector LISA.
Reaching the desired accuracy requires calculation of the second-order
gravitational perturbations produced by the compact object. At the point
particle limit the second-order gravitational perturbation equations turn out
to have highly singular source terms, for which the standard retarded solutions
diverge. Here we study a simplified scalar toy-model in which a point particle
induces a nonlinear scalar field in a given curved spacetime. The corresponding
second-order scalar perturbation equation in this model is found to have a
similar singular source term, and therefore its standard retarded solutions
diverge. We develop a regularization method for constructing well-defined
causal solutions for this equation. Notably these solutions differ from the
standard retarded solutions, which are ill-defined in this case.


title: The Cosmological Perturbation of Braneworld with An Anisotropic Bulk

abstract:
  The braneworld cosmological model was constructed by embedding a 3-brane into
a higher dimensional bulk background geometry and the usual matter of our
universe was assumed to be confined in the brane while the gravity can
propagate in the bulk. By considering that the bulk geometry is anisotropic,
after reviewed the separable solution for the bulk metric and the result that
the anisotropic property of the bulk can support the perfect fluid kind of the
matter in the brane, we develop a formalism of the cosmological perturbation
for this kind of anisotropic braneworld model. As in isotropic case, we can
also decompose the perturbation into scalar, vector and tensor modes, we find
that the formalism for the anisotropic braneworld cosmological perturbation are
very different from the isotropic case. The anisotropic effect can be reflected
in the tensor modes which dominated the cosmological gravitation waves.
Finally, we also discussed the perturbed Einstein equations governed the
dynamics of the bulk geometry and the brane with the junction conditions.


title:
Lorentz invariance violation and charge (non--)conservation: A general
  theoretical frame for extensions of the Maxwell equations

abstract:
  All quantum gravity approaches lead to small modifications in the standard
laws of physics which lead to violations of Lorentz invariance. One particular
example is the extended standard model (SME). Here, a general phenomenological
approach for extensions of the Maxwell equations is presented which turns out
to be more general than the SME and which covers charge non--conservation
(CNC), too. The new Lorentz invariance violating terms cannot be probed by
optical experiments but need, instead, the exploration of the electromagnetic
field created by a point charge or a magnetic dipole. Some scalar--tensor
theories and higher dimensional brane theories predict CNC in four dimensions
and some models violating Special Relativity have been shown to be connected
with CNC and its relation to the Einstein Equivalence Principle has been
discussed. Due to this upcoming interest, the experimental status of electric
charge conservation is reviewed. Up to now there seem to exist no unique tests
of charge conservation. CNC is related to the precession of polarization, to a
modification of the $1/r$--Coulomb potential, and to a time-dependence of the
fine structure constant. This gives the opportunity to describe a dedicated
search for CNC.


title:
Casimir effect for the massless Dirac field in two-dimensional
  Reissner-Nordstr\"{o}m spacetime

abstract:
  In this paper, the two-dimensional Reissner-Nordstr\"{o}m black hole is
considered as a system of the Casimir type. In this background the Casimir
effect for the massless Dirac field is discussed. The massless Dirac field is
confined between two ``parallel plates'' separated by a distance $L$ and there
is no particle current drilling through the boundaries. The vacuum expectation
values of the stress tensor of the massless Dirac field at infinity are
calculated separately in the Boulware state, the Hartle-Hawking state and the
Unruh state.


title: A teleparallel effective geometry for Einstein's unified field theory

abstract:
  Riemannian and teleparallel geometrical approaches to the investigation of
Maxwell electrodynamics shown that a unified field theory of gravitation and
electromagnetism a la Einstein can be obtained from a stationary metric. This
idea contrasts with the recently proposed pre-metric electrodynamics by Hehl
and Obukhov. In the teleparallel case the definition of the electric field is
obtained straightforward from the spacetime metric and the orthonormal basis
frame of teleparallelism. In this case the only nonvanishing component of
Cartan torsion is defined as the effective electric field. In this approach the
gravitational potentials or metric coefficients are expressed in terms of the
effective or analogous electric and magnetic potentials. Thefore the Maxwell
equations in vacuum can be obtained by derivation of this electric field
definition as usual. In the Riemannian case we consider an electrostatic
spacetime where the Einstein equations in vacuum in the approximation of linear
fields. The constraint of Einstein equations in vacuum are shown to lead or to
the Coulomb equation or to a singular behaviour on the metric which would
represent a kind of effective electrodynamic black hole event horizon.


title: Godel Type Metrics in Randall Sundrum Model

abstract:
  Anisotropic cosmological models such as the G\"{o}del universe and its
extensions - G\"{o}del type solutions, are embedded on a visible 3-brane in the
Randall-Sundrum 1 model. The size of the extra dimension is stabilized by
tuning the rotation parameter to a very small value so that hierarchy problem
can be solved. A limiting case also yields the Randall-Sundrum 2 model. The
rotation parameter on the visible brane turns out to be of order $10^{-32}$,
which implies that visible brane essentially lacks rotation.


title:
Future complete spacetimes with spacelike isometry group and field
  sources

abstract:
  We extend to the Einstein Maxwell Higgs system results first obtained
previously in collaboration with V. Moncrief for Einstein equations in vacuum.


title: The Search for Quantum Gravity Signals

abstract:
  We give an overview of ongoing searches for effects motivated by the study of
the quantum-gravity problem. We describe in greater detail approaches which
have not been covered in recent ``Quantum Gravity Phenomenology'' reviews. In
particular, we outline a new framework for describing Lorentz invariance
violation in the Maxwell sector. We also discuss the general strategy on the
experimental side as well as on the theoretical side for a search for quantum
gravity effects. The role of test theories, kinematical and dymamical, in this
general context is emphasized. The present status of controlled laboratory
experiments is described, and we also summarize some key results obtained on
the basis of astrophysical observations.


title:
Excision methods for high resolution shock capturing schemes applied to
  general relativistic hydrodynamics

abstract:
  We present a simple method for applying excision boundary conditions for the
relativistic Euler equations. This method depends on the use of
Reconstruction-Evolution methods, a standard class of HRSC methods. We test
three different reconstruction schemes, namely TVD, PPM and ENO. The method
does not require that the coordinate system is adapted to the excision
boundary. We demonstrate the effectiveness of our method using tests containing
discontinuites, static test-fluid solutions with black holes, and full
dynamical collapse of a neutron star to a black hole. A modified PPM scheme is
introduced because of problems arisen when matching excision with the original
PPM reconstruction scheme.


title: Spacelike slices from globally well-behaved simultaneity connections

abstract:
  As shown by the development of Special Relativity the simultaneity concept
should be related to that of reference frame. Poincare' proposed to define the
simultaneity of two events by means of light signals following what is nowadays
known as the Einstein simultaneity convention. The need of a simultaneity
definition is present also in general relativity and in curved spacetimes in
order to provide the observers with a coordinate time.
  It is recognized that the old Einstein simultaneity convention is nothing but
a connection on a suitable trivial bundle that defines the reference frame.
Unfortunately, it has a non vanishing holonomy in curved and even in flat
spacetimes a fact that makes it almost useless. We point out the advantage of
local simultaneity conventions showing that they are represented by local
simultaneity connections. Among them there is one, uniquely determined by the
reference frame, which is particularly well-behaved globally.


title:
Dynamic quantum theory of large additional dimensions for non-massive
  particles

abstract:
  Brane model of universe is considered for zero-mass particle. Equation of
Wheeler - de Witt type is obtained using variation principle from the
well-known conservation laws inside the brane. This equation includes term
accounting the variation of brane topology. Solutions are obtained analytically
at some simplifications and the dispersion relations are derived for frequency
of wave associated with the particle.


title: Einstein-Cartan Algebroids and Black Holes in Solitonic Backgrounds

abstract:
  We construct a new class of exact solutions describing spacetimes possessing
Lie algebroid symmetry. They are described by generic off-diagaonal 5D metrics
embedded in bosonic string gravity and possess nontrivial limits to the
Einstein gravity. While we focus on nonholonomic vielbein transforms of the
Schwarzschild metrics to 5D ansatz with solitonic backgrounds, much of the
analysis continues to hold for more general configurations with nontrivial Lie
algebroid structure and nonlinear connections. We carefully investigate some
examples when the anchor structure is related to 3D solitonic interactions. The
approach defines a general geometric method of constructing exact solutions
with various type of symmetries and new developments and applications of the
Lie aglebroid theory.


title: Noncommutative scalar field minimally coupled to gravity

abstract:
  A model for noncommutative scalar fields coupled to gravity based on the
generalization of the Moyal product is proposed. Solutions compatible with
homogeneous and isotropic flat Robertson-Walker spaces to first non-trivial
order in the perturbation of the star-product are presented. It is shown that
in the context of a typical chaotic inflationary scenario, at least in the
slow-roll regime, noncommutativity yields no observable effect.


title: On the time delay in binary systems

abstract:
  The aim of this paper is to study the time delay on electromagnetic signals
propagating across a binary stellar system. We focus on the antisymmetric
gravitomagnetic contribution due to the angular momentum of one of the stars of
the pair. Considering a pulsar as the source of the signals, the effect would
be manifest both in the arrival times of the pulses and in the frequency shift
of their Fourier spectra. We derive the appropriate formulas and we discuss the
influence of different configurations on the observability of gravitomagnetic
effects. We argue that the recently discovered PSR J0737-3039 binary system
does not permit the detection of the effects because of the large size of the
eclipsed region.


title: Potentials between D-Branes in a Supersymmetric Model of Space-Time Foam

abstract:
  We study a supersymmetric model of space-time foam with two stacks each of
eight D8-branes with equal string tensions, separated by a single bulk
dimension containing D0-brane particles that represent quantum fluctuations.
The ground-state configuration with static D-branes has zero vacuum energy,
but, when they move, the interactions among the D-branes and D-particles due to
the exchanges of strings result in a non-trivial, positive vacuum energy. We
calculate its explicit form in the limits of small velocities and large or
small separations between the D-branes and/or the D-particles. This non-trivial
vacuum energy appears as a central charge deficit in the non-critical stringy
$\sigma$ model describing perturbative string excitations on a moving D-brane.
These calculations enable us to characterise the ground state of the
D-brane/D-particle system, and provide a framework for discussing brany
inflation and the possibility of residual Dark Energy in the present-day
Universe.


title: The nearly flat universe

abstract:
  We study here what it means for the Universe to be nearly flat, as opposed to
exactly flat. We give three definitions of nearly flat, based on density,
geometry and dynamics; all three definitions are equivalent and depend on a
single constant flatness parameter epsilon that quantifies the notion of nearly
flat. Observations can only place an upper limit on epsilon, and always allow
the possibility that the Universe is infinite with k=-1 or finite with k=1. We
use current observational data to obtain a numerical upper limit on the
flatness parameter and discuss its implications, in particular the
"naturalness" of the nearly flat Universe.


title:
Global existence and future asymptotic behaviour for solutions of the
  Einstein-Vlasov-scalar field system with surface symmetry

abstract:
  We prove in the cases of plane and hyperbolic symmetries a global in time
existence result in the future for comological solutions of the
Einstein-Vlasov-scalar field system, with the sources generated by a
distribution function and a scalar field, subject to the Vlasov and wave
equations respectively. The spacetime is future geodesically complete in the
special case of plane symmetry with only a scalar field. Causal geodesics are
also shown to be future complete for homogeneous solutions of the
Einstein-Vlasov-scalar field system with plane and hyperbolic symmetry.


title:
Similarity Solutions of the Einstein-Maxwell equations with 1 Killing
  Vector

abstract:
  New similarity variables are introduced for the Einstein - Maxwell equations
with one Killing vector that reduce the non-linear partial differential
equations in three independent variables to ordinary differential equations.
These similarity variables are the extensions of those previously found for the
Einstein-Maxwell equations with two Killing vectors. The resulting equations
are then solved, providing new solutions of the Einstein - Maxwell equations
with one Killing Vector.


title:
Cosmological Singularities, Einstein Billiards and Lorentzian Kac-Moody
  Algebras

abstract:
  The structure of the general, inhomogeneous solution of (bosonic)
Einstein-matter systems in the vicinity of a cosmological singularity is
considered. We review the proof (based on ideas of
Belinskii-Khalatnikov-Lifshitz and technically simplified by the use of the
Arnowitt-Deser-Misner Hamiltonian formalism) that the asymptotic behaviour, as
one approaches the singularity, of the general solution is describable, at each
(generic) spatial point, as a billiard motion in an auxiliary Lorentzian space.
For certain Einstein-matter systems, notably for pure Einstein gravity in any
spacetime dimension D and for the particular Einstein-matter systems arising in
String theory, the billiard tables describing asymptotic cosmological behaviour
are found to be identical to the Weyl chambers of some Lorentzian Kac-Moody
algebras. In the case of the bosonic sector of supergravity in 11 dimensional
spacetime the underlying Lorentzian algebra is that of the hyperbolic Kac-Moody
group E(10), and there exists some evidence of a correspondence between the
general solution of the Einstein-three-form system and a null geodesic in the
infinite dimensional coset space E(10)/K (E(10)), where K (E(10)) is the
maximal compact subgroup of E(10).


title: Hamilton-Jacobi equation and the breaking of the WKB approximation

abstract:
  A simple method to deal with four dimensional Hamilton-Jacobi equation for
null hypersurfaces is introduced. This method allows to find simple geometrical
conditions which give rise to the failure of the WKB approximation on curved
spacetimes. The relation between such failure, extreme blackholes and the
Cosmic Censor hypothesis is briefly discussed.


title:
Computational Relativistic Astrophysics With Adaptive Mesh Refinement:
  Testbeds

abstract:
  We have carried out numerical simulations of strongly gravitating systems
based on the Einstein equations coupled to the relativistic hydrodynamic
equations using adaptive mesh refinement (AMR) techniques. We show AMR
simulations of NS binary inspiral and coalescence carried out on a workstation
having an accuracy equivalent to that of a $1025^3$ regular unigrid simulation,
which is, to the best of our knowledge, larger than all previous simulations of
similar NS systems on supercomputers. We believe the capability opens new
possibilities in general relativistic simulations.


title:
Anisotropic cosmological models with perfect fluid and dark energy
  revisited

abstract:
  We consider a self-consistent system of Bianchi type-I (BI) gravitational
field and a binary mixture of perfect fluid and dark energy. The perfect fluid
is taken to be the one obeying the usual equation of state, i.e., $p = \zeta
\ve$, with $\zeta \in [0, 1]$ whereas, the dark energy is considered to be
obeying a quintessence-like equation of state. Exact solutions to the
corresponding Einstein equations are obtained. The model in consideration gives
rise to a Universe which is spatially finite. Depending on the choice of
problem parameters the Universe is either close with a space-time singularity,
or an open one which is oscillatory, regular and infinite in time.


title:
A Search for Gravitational Waves Associated with the Gamma Ray Burst
  GRB030329 Using the LIGO Detectors

abstract:
  We have performed a search for bursts of gravitational waves associated with
the very bright Gamma Ray Burst GRB030329, using the two detectors at the LIGO
Hanford Observatory. Our search covered the most sensitive frequency range of
the LIGO detectors (approximately 80-2048 Hz), and we specifically targeted
signals shorter than 150 ms. Our search algorithm looks for excess correlated
power between the two interferometers and thus makes minimal assumptions about
the gravitational waveform. We observed no candidates with gravitational wave
signal strength larger than a pre-determined threshold. We report frequency
dependent upper limits on the strength of the gravitational waves associated
with GRB030329. Near the most sensitive frequency region, around 250 Hz, our
root-sum-square (RSS) gravitational wave strain sensitivity for optimally
polarized bursts was better than h_RSS = 6E-21 Hz^{-1/2}. Our result is
comparable to the best published results searching for association between
gravitational waves and GRBs.


title: Causal structures and causal boundaries

abstract:
  We give an up-to-date perspective with a general overview of the theory of
causal properties, the derived causal structures, their classification and
applications, and the definition and construction of causal boundaries and of
causal symmetries, mostly for Lorentzian manifolds but also in more abstract
settings.


title: Relativistic velocity space, Wigner rotation and Thomas precession

abstract:
  We develop a relativistic velocity space called \emph{rapidity space} from
the single assumption of Lorentz invariance, and use it to visualize and
calculate effects resulting from the successive application of non-colinear
Lorentz boosts. In particular, we show how rapidity space provides a geometric
approach to Wigner rotation and Thomas precession in the same way that
spacetime provides a geometrical approach to kinematic effects in special
relativity.


title:
Motion and gravitational radiation of a binary system consisting of an
  oscillating and rotating coplanar dusty disk and a point-like object

abstract:
  A binary system composed of an oscillating and rotating coplanar dusty disk
and a point mass is considered. The conservative dynamics is treated on the
Newtonian level. The effects of gravitational radiation reaction and wave
emission are studied to leading quadrupole order. The related waveforms are
given. The dynamical evolution of the system is determined semi-analytically
exploiting the Hamiltonian equations of motion which comprise the effects both
of the Newtonian tidal interaction and the radiation reaction on the motion of
the binary system in elliptic orbits. Tidal resonance effects between orbital
and oscillatory motions are considered in the presence of radiation damping.


title: Intermediate inflation and the slow-roll approximation

abstract:
  It is shown that spatially homogeneous solutions of the Einstein equations
coupled to a nonlinear scalar field and other matter exhibit accelerated
expansion at late times for a wide variety of potentials $V$. These potentials
are strictly positive but tend to zero at infinity. They satisfy restrictions
on $V'/V$ and $V''/V'$ related to the slow-roll approximation. These results
generalize Wald's theorem for spacetimes with positive cosmological constant to
those with accelerated expansion driven by potentials belonging to a large
class.


title:
Unconstrained degrees of freedom for gravitational waves,
  $\beta$--foliations and spherically symmetric initial data

abstract:
  A new parameterization of unconstrained degrees of freedom for gravitational
field, used in Classical and Quantum Gravity {\bf 11}, 1055-1068 (1994), has
been generalized to one-parameter family of such parameterizations, depending
on a real parameter $\beta \in [0,2]$. The description introduced in CQG 11,
1055 corresponds to the special choice $\beta=0$. The method is closely related
to the proof of the positivity of the energy presented in Phys. Rev. D {\bf
36}, 1041-1044 (1987) where $\beta$-foliations have been introduced (see also
applications to black holes dynamics in Classical and Quantum Gravity {\bf 6},
1535-1539 (1989) and Acta Physica Polonica B {\bf 25}, 1413-17 (1994)).
Spherically symmetric initial data corresponding to trivial degrees of freedom
is analyzed along these lines. In particular, the quasi-local energy content of
the Schwarzschild initial data is analyzed for different choices of the
$\beta$-gauge.


title:
On global models for finite rotating objects in equilibrium in
  cosmological backgrounds

abstract:
  The studies in general relativity of rotating finite objects in equilibrium
have usually focused on the case when they are truly isolated, this is, the
models to describe finite objects are embedded in an asymptotically flat
exterior vacuum. Known results ensure the uniqueness of the vacuum exterior
field by using the boundary data for the exterior field given at the surface of
the object plus the decay of the exterior field at infinity. The final aim of
the present work is to study the consequences on the interior models by
changing the boundary condition at infinity to one accounting for the embedding
of the object in a cosmological background. Considering first the FLRW standard
cosmological backgrounds, we are studying the general matching of FLRW with
stationary axisymmetric spacetimes in order to find the new boundary condition
for the vacuum region. Here we present the first results.


title:
Reconstructing Quantum Geometry from Quantum Information: Spin Networks
  as Harmonic Oscillators

abstract:
  Loop Quantum Gravity defines the quantum states of space geometry as spin
networks and describes their evolution in time. We reformulate spin networks in
terms of harmonic oscillators and show how the holographic degrees of freedom
of the theory are described as matrix models. This allow us to make a link with
non-commutative geometry and to look at the issue of the semi-classical limit
of LQG from a new perspective. This work is thought as part of a bigger project
of describing quantum geometry in quantum information terms.


title: Some Remarks on the Semi-Classical Limit of Quantum Gravity

abstract:
  One of the most important issues in quantum gravity is to identify its
semi-classical regime. First the issue is to define for we mean by a
semi-classical theory of quantum gravity, then we would like to use it to
extract physical predictions. Writing an effective theory on a flat background
is a way to address this problem and I explain how the non-commutative
spacetime of deformed special relativity is the natural arena for such
considerations. On the other hand, I discuss how the definition of the
semi-classical regime can be formulated in a background independent fashion in
terms of quantum information and renormalisation of geometry.


title: Exact solutions of the Dirac equation in Robertson-Walker space-time

abstract:
  The covariant Dirac equation in Robertson-Walker space-time is studied under
the comoving coordinates. The exact forms of the spatial factor of wave
function are respectively acquired in closed, spatially flat, and open
universes.


title:
The Running of the Cosmological and the Newton Constant controlled by
  the Cosmological Event Horizon

abstract:
  We study the renormalisation group running of the cosmological and the Newton
constant, where the renormalisation scale is given by the inverse of the radius
of the cosmological event horizon. In this framework, we discuss the future
evolution of the universe, where we find stable de Sitter solutions, but also
"big crunch"-like and "big rip"-like events, depending on the choice of the
parameters in the model.


title: A note on DSR-like approach to space-time

abstract:
  In this note we discuss the possibility to define a space-time with a DSR
based approach. We show that the strategy of defining a non linear realization
of the Lorentz symmetry with a consistent vector composition law cannot be
reconciled with the extra request of an invariant length (time) scale. The
latter request forces to abandon the group structure of the translations and
leaves a space-time structure where points with relative distances smaller or
equal to the invariant scale can not be unambiguously defined.


title: Black hole formation through fragmentation of toroidal polytropes

abstract:
  We investigate new paths to black hole formation by considering the general
relativistic evolution of a differentially rotating polytrope with toroidal
shape. We find that this polytrope is unstable to nonaxisymmetric modes, which
leads to a fragmentation into self-gravitating, collapsing components. In the
case of one such fragment, we apply a simplified adaptive mesh refinement
technique to follow the evolution to the formation of an apparent horizon
centered on the fragment. This is the first study of the one-armed instability
in full general relativity.


title: Stochastic Spacetime and Brownian Motion of Test Particles

abstract:
  The operational meaning of spacetime fluctuations is discussed. Classical
spacetime geometry can be viewed as encoding the relations between the motions
of test particles in the geometry. By analogy, quantum fluctuations of
spacetime geometry can be interpreted in terms of the fluctuations of these
motions. Thus one can give meaning to spacetime fluctuations in terms of
observables which describe the Brownian motion of test particles. We will first
discuss some electromagnetic analogies, where quantum fluctuations of the
electromagnetic field induce Brownian motion of test particles. We next discuss
several explicit examples of Brownian motion caused by a fluctuating
gravitational field. These examples include lightcone fluctuations, variations
in the flight times of photons through the fluctuating geometry, and
fluctuations in the expansion parameter given by a Langevin version of the
Raychaudhuri equation. The fluctuations in this parameter lead to variations in
the luminosity of sources. Other phenomena which can be linked to spacetime
fluctuations are spectral line broadening and angular blurring of distant
sources.


title:
Discrete Gravity as a Local Theory of the Poincar\'e Group in the First
  Order Formalism

abstract:
  A discrete theory of gravity locally invariant under the Poincar\'e group is
considered as in a companion paper. We define a first order theory, in the
sense of Palatini, on the metric-dual Voronoi complex of a simplicial complex.
We follow the same spirit of the continuum theory of General Relativity in the
Cartan formalism. The field equations are carefully derived taking in account
the constraints of the theory. They look very similar to first order Einstein
equations in the Cartan formalism. It is shown that in the limit of {\it small
deficit angles} these equations have Regge Calculus, locally, as the only
solution. A quantum measure is easly defined which does not suffer the
ambiguities of Regge Calculus, and a coupling with fermionic matter is easily
introduced


title:
A gluing construction for non-vacuum solutions of the Einstein
  constraint equations

abstract:
  We extend the conformal gluing construction of Isenberg-Mazzeo-Pollack [18]
by establishing an analogous gluing result for field theories obtained by
minimally coupling Einstein's gravitational theory with matter fields. We treat
classical fields such as perfect fluids and the Yang-Mills equations as well as
the Einstein-Vlasov system, which is an important example coming from kinetic
theory. In carrying out these extensions, we extend the conformal gluing
technique to higher dimensions and codify it in such a way as to make more
transparent where it can, and can not, be applied. In particular, we show
exactly what criteria need to be met in order to apply the construction, in its
present form, to any other non-vacuum field theory.


title: Black hole tidal problem in the Fermi normal coordinates

abstract:
  We derive a tidal potential for a self-gravitating fluid star orbiting Kerr
black hole along a timelike geodesic extending previous works by Fishbone and
Marck. In this paper, the tidal potential is calculated up to the third and
fourth-order terms in $R/r$, where $R$ is the stellar radius and $r$ the
orbital separation, in the Fermi-normal coordinate system following the
framework developed by Manasse and Misner. The new formulation is applied for
determining the tidal disruption limit (Roche limit) of corotating Newtonian
stars in circular orbits moving on the equatorial plane of Kerr black holes. It
is demonstrated that the third and fourth-order terms quantitatively play an
important role in the Roche limit for close orbits with $R/r \agt 0.1$. It is
also indicated that the Roche limit of neutron stars orbiting a stellar-mass
black hole near the innermost stable circular orbit may depend sensitively on
the equation of state of the neutron star.


title:
Lightlike simultaneity, comoving observers and distances in general
  relativity

abstract:
  We state a condition for an observer to be comoving with another observer in
general relativity, based on the concept of lightlike simultaneity. Taking into
account this condition, we study relative velocities, Doppler effect and light
aberration. We obtain that comoving observers observe the same light ray with
the same frequency and direction, and so gravitational redshift effect is a
particular case of Doppler effect. We also define a distance between an
observer and the events that it observes, that coincides with the known affine
distance. We show that affine distance is a particular case of radar distance
in the Minkowski space-time and generalizes the proper radial distance in the
Schwarzschild space-time. Finally, we show that affine distance gives us a new
concept of distance in Robertson-Walker space-times, according to Hubble law.


title: Kaluza-Klein gravitons are negative energy dust in brane cosmology

abstract:
  We discuss the effect of Kaluza-Klein (KK) modes of bulk metric perturbations
on the second Randall-Sundrum (RS II) type brane cosmology, taking the possible
backreaction in the bulk and on the brane into account. KK gravitons may be
produced via quantum fluctuations during a de Sitter (dS) inflating phase of
our brane universe. In an effective 4-dimensional theory in which one
integrates out the extra-dimensional dependence in the action, KK gravitons are
equivalent to massive gravitons on the brane with masses $m>3H/2$, where $H$
represents the expansion rate of a dS brane. Thus production of even a tiny
amount of KK gravitons may eventually have a significant impact on the
late-time brane cosmology. As a first step to quantify the effect of KK
gravitons on the brane, we calculate the effective energy density and pressure
for a single KK mode. Surprisingly, we find that a KK mode behaves as cosmic
dust with a negative energy density on the brane. We note that the bulk energy
density of a KK mode is positive definite and there occurs no singular
phenomenon in the bulk.


title: Global properties of dilatonic Gauss-Bonnet black holes

abstract:
  We study the phase space of the spherically symmetric solutions of Einstein
Gauss-Bonnet system nonminimally coupled to a scalar field and show that in
four dimensions the only regular black hole solutions are asymptotically flat


title:
Reconstruction of Black Hole Metric Perturbations from Weyl Curvature
  II: The Regge-Wheeler gauge

abstract:
  Perturbation theory of rotating black holes is described in terms of the Weyl
scalars $\psi_4$ and $\psi_0$; each satisfying the Teukolsky's complex master
wave equation with spin $s=\mp2$, and respectively representing outgoing and
ingoing radiation. We explicitly construct the metric perturbations out of
these Weyl scalars in the Regge-Wheeler gauge in the nonrotating limit. We
propose a generalization of the Regge-Wheeler gauge for Kerr background in the
Newman-Penrose language, and discuss the approach for building up the perturbed
spacetime of a rotating black hole. We also provide both-way relationships
between waveforms defined in the metric and curvature approaches in the time
domain, also known as the (inverse-) Chandrasekhar transformations, generalized
to include matter.


title:
Measurement of a Stochastic Gravitational Wave Background with a Single
  Laser Interferometer

abstract:
  Laser interferometer gravitational wave detectors can be operated at their
free spectral range frequency. We show that in this case and when the
interferometer is well understood one could detect a stochastic background
using a single detector.


title:
Generalized Radar 4-Coordinates and Equal-Time Cauchy Surfaces for
  Arbitrary Accelerated Observers

abstract:
  All existing 4-coordinate systems centered on the world-line of an
accelerated observer are only locally defined like it happens for Fermi
coordinates both in special and general relativity. As a consequence, it is not
known how non-inertial observers can build {\it equal-time surfaces} which a)
correspond to a conventional observer-dependent definition of synchronization
of distant clocks; b) are good Cauchy surfaces for Maxwell equations. Another
type of coordinate singularities are those connected to the relativistic
rotating coordinate systems (the rotating disk).We show that the use of
Hamiltonian methods based on 3+1 splittings of space-time allows to define as
many observer-dependent globally defined radar 4-coordinate systems as nice
foliations of space-time with space-like hyper-surfaces admissible according to
M$\o$ller (for instance only differentially rotating relativistic coordinate
system are allowed). All these conventional notions of an {\it instantaneous
3-space} for an arbitrary observer can be empirically defined by introducing
generalizations of Einstein ${1\over 2}$ convention for clock synchronization
in inertial frames. Each admissible 3+1 splitting corresponds to a non-rigid
non-inertial frame centered on the observer. When there is a Lagrangian
description of an isolated relativistic system, its reformulation as a
parametrized Minkowski theory allows to show that all the admissible
synchronization conventions are {\it gauge equivalent}, as it also happens in
canonical metric and tetrad gravity, where, however, the chrono-geometrical
structure of space-time is dynamically determined.


title: New Spin Foam Models of Quantum Gravity

abstract:
  We give a brief and a critical review of the Barret-Crane spin foam models of
quantum gravity. Then we describe two new spin foam models which are obtained
by direct quantization of General Relativity and do not have some of the
drawbacks of the Barret-Crane models. These are the model of spin foam
invariants for the embedded spin networks in loop quantum gravity and the spin
foam model based on the integration of the tetrads in the path integral for the
Palatini action.


title:
Conformal invariance and the conformal-traceless decomposition of the
  gravitational field

abstract:
  Einstein's theory of general relativity is written in terms of the variables
obtained from a conformal--traceless decomposition of the spatial metric and
extrinsic curvature. The determinant of the conformal metric is not restricted,
so the action functional and equations of motion are invariant under conformal
transformations. With this approach the conformal--traceless variables remain
free of density weights. The conformal invariance of the equations of motion
can be broken by imposing an evolution equation for the determinant of the
conformal metric g. Two conditions are considered, one in which g is constant
in time and one in which g is constant along the unit normal to the spacelike
hypersurfaces. This approach is used to write the
Baumgarte--Shapiro--Shibata--Nakamura system of evolution equations in
conformally invariant form. The presentation includes a discussion of the
conformal thin sandwich construction of gravitational initial data, and the
conformal flatness condition as an approximation to the evolution equations.


title: Timelike surfaces in Lorentz covariant loop gravity and spin foam models

abstract:
  We construct a canonical formulation of general relativity for the case of a
timelike foliation of spacetime. The formulation possesses explicit covariance
with respect to Lorentz transformations in the tangent space. Applying the loop
approach to quantize the theory we derive the spectrum of the area operator of
a two-dimensional surface. Its different branches are naturally associated to
spacelike and timelike surfaces. The results are compared with the predictions
of Lorentzian spin foam models. A restriction of the representations labeling
spin networks leads to perfect agreement between the states as well as the area
spectra in the two approaches.


title: Emergent phenomenology from deterministic Cartan-Randers systems

abstract:
  We consider specific deterministic quantum models of Cartan-Randers type and
show how a dualized abelian gauge symmetry, diffeomorphism invariance, the
Principle of Inertia, reversibility of phenomenological dynamics, maximal
acceleration and maximal propagation speed for matter arise from such models in
an phenomenological description. Two particular predictions are highlighted:
the first is the value of maximal acceleration is universal and has the value
of order 10^{52} m/s^2. The second prediction is that gauge symmetries in
phenomenological models must come dualized and containing an abelian sector.


title:
Light deflection in the post-linear gravitational field of bounded
  point-like masses

abstract:
  Light deflection in the post-linear gravitational field of two bounded
point-like masses is treated. Both the light source and the observer are
assumed to be located at infinity in an asymptotically flat space. The
equations of light propagation are explicitly integrated to the second order in
$G/c^2$. Some of the integrals are evaluated by making use of an expansion in
powers of the ratio of the relative separation distance to the impact parameter
$(r_{12}/\xi)$. A discussion of which orders must be retained to be consistent
with the expansion in terms of $G/c^2$ is given. It is shown that the
expression obtained in this paper for the angle of light deflection is fully
equivalent to the expression obtained by Kopeikin and Sch\"afer up to the order
given there. The deflection angle takes a particularly simple form for a light
ray originally propagating orthogonal to the orbital plane of a binary with
equal masses. Application of the formulae for the deflection angle to the
double pulsar PSR J0737-3039 for an impact parameter five times greater than
the relative separation distance of the binary's components shows that the
corrections to the Epstein-Shapiro light deflection angle of about $10^{-6}$
arcsec lie between $10^{-7}$ and $10^{-8}$ arcsec.


title: Dressing a black hole with non-minimally coupled scalar field hair

abstract:
  We investigate the possibility of dressing a four-dimensional black hole with
classical scalar field hair which is non-minimally coupled to the space-time
curvature. Our model includes a cosmological constant but no self-interaction
potential for the scalar field. We are able to rule out black hole hair except
when the cosmological constant is negative and the constant governing the
coupling to the Ricci scalar curvature is positive. In this case, non-trivial
hairy black hole solutions exist, at least some of which are linearly stable.
However, when the coupling constant becomes too large, the black hole hair
becomes unstable.


title: Analog of Superradiance effect in BEC

abstract:
  We investigate the scattering of phase oscillation of Bose-Einstein
Condensate by a 'draining of bathtub' type fluid motion. We derive a relation
between the reflection and transmission coefficients which exhibits existence
of analog of 'Superradiance effect' in BEC vortex with sink.


title:
Quasinormal modes in Schwarschild black holes due to arbitrary spin
  fields

abstract:
  The Newman-Penrose formalism is used to deal with the massless scalar,
neutrino, electromagnetic, gravitino and gravitational quasinormal modes (QNMs)
in Schwarzschild black holes in a united form. The quasinormal mode frequencies
evaluated by using the 3rd-order WKB potential approximation show that the
boson perturbations and the fermion perturbations behave in a contrary way for
the variation of the oscillation frequencies with spin, while this is no longer
true for the damping's, which variate with $s$ in a same way both for boson and
fermion perturbations.


title: Stability between foliations in general relativity

abstract:
  The aim of this paper is to study foliations that remain invariant by
parallel transports along the integral curves of vector fields of another
foliations. According to this idea, we define a new concept of stability
between foliations. A particular case of stability (called regular stability)
is studied, giving a useful characterization in terms of the Riemann curvature
tensor. This characterization allows us to prove that there are no regularly
self-stable foliations of dimension greater than 1 in Schwarzschild and
Robertson-Walker space-times. Finally, we study the existence of regularly
self-stable foliations in other space-times, like $pp$-wave space-times.


title:
Geometric description of lightlike foliations by an observer in general
  relativity

abstract:
  We introduce new concepts and properties of lightlike distributions and
foliations (of dimension and co-dimension 1) in a space-time manifold of
dimension $n$, from a purely geometric point of view. Given an observer and a
lightlike distribution $\Omega $ of dimension or co-dimension 1, its lightlike
direction is broken down into two vector fields: a timelike vector field $U$
representing the observer and a spacelike vector field $S$ representing the
relative direction of propagation of $\Omega $ for this observer. A new
distribution $\Omega_U^-$ is defined, with the opposite relative direction of
propagation for the observer $U$. If both distributions $\Omega $ and $\Omega
_U^-$ are integrable, the pair \Omega ,\Omega_U^- $ represents the wave fronts
of a stationary wave for the observer $U$. However, we show in an example that
the integrability of $\Omega $ does not imply the integrability of
$\Omega_U^-$.


title: Relativistic hydrodynamics with sources for cosmological K-fluids

abstract:
  We consider hydrodynamics with non conserved number of particles and show
that it can be modeled with effective fluid Lagrangians which explicitly depend
on the velocity potentials. For such theories, the {}``shift symetry''
$\phi\to\phi+$const. leading to the conserved number of fluid particles in
conventional hydrodynamics is globaly broken and, as a result, the non
conservation of particle number appears as a source term in the continuity
equation. The particle number non-conservation is balanced by the entropy
change, with both the entropy and the source term expresed in terms of the
fluid velocity potential. Equations of hydrodynamics are derived using a
modified version of Schutz's variational principle method. Examples of fluids
described by such Lagrangians (tachyon condensate, k-essence) in spatially flat
isotropic universe are briefly discussed.


title:
Discreteness Corrections to the Effective Hamiltonian of Isotropic Loop
  Quantum Cosmology

abstract:
  One of the qualitatively distinct and robust implication of Loop Quantum
Gravity (LQG) is the underlying discrete structure. In the cosmological context
elucidated by Loop Quantum Cosmology (LQC), this is manifested by the
Hamiltonian constraint equation being a (partial) difference equation. One
obtains an effective Hamiltonian framework by making the continuum
approximation followed by a WKB approximation. In the large volume regime,
these lead to the usual classical Einstein equation which is independent of
both the Barbero-Immirzi parameter $\gamma$ as well as $\hbar$. In this work we
present an alternative derivation of the effective Hamiltonian by-passing the
continuum approximation step. As a result, the effective Hamiltonian is
obtained as a close form expression in $\gamma$. These corrections to the
Einstein equation can be thought of as corrections due to the underlying
discrete (spatial) geometry with $\gamma$ controlling the size of these
corrections. These corrections imply a bound on the rate of change of the
volume of the isotropic universe. In most cases these are perturbative in
nature but for cosmological constant dominated isotropic universe, there are
significant deviations.


title: New Models of General Relativistic Static Thick Disks

abstract:
  New families of exact general relativistic thick disks are constructed using
the ``displace, cut, fill and reflect'' method. A class of functions used to
``fill'' the disks is derived imposing conditions on the first and second
derivatives to generate physically acceptable disks. The analysis of the
function's curvature further restrict the ranges of the free parameters that
allow phisically acceptable disks. Then this class of functions together with
the Schwarzschild metric is employed to construct thick disks in isotropic,
Weyl and Schwarzschild canonical coordinates. In these last coordinates an
additional function must be added to one of the metric coefficients to generate
exact disks. Disks in isotropic and Weyl coordinates satisfy all energy
conditions, but those in Schwarzschild canonical coordinates do not satisfy the
dominant energy condition.


title: Modern Approaches to Cosmological Singularities

abstract:
  We review recent work and present new examples about the character of
singularities in globally and regularly hyperbolic, isotropic universes. These
include recent singular relativistic models, tachyonic and phantom universes as
well as inflationary cosmologies.


title: Self Sustained Traversable Wormholes?

abstract:
  We compute the graviton one loop contribution to a classical energy in a
traversable wormhole background. Such a contribution is evaluated by means of a
variational approach with Gaussian trial wave functionals. A zeta function
regularization is involved to handle with divergences. A renormalization
procedure is introduced and the finite one loop energy is considered as a
self-consistent source for the traversable wormhole.


title: Neutral perfect fluids of Majumdar-type in general relativity

abstract:
  We consider the extension of the Majumdar-type class of static solutions for
the Einstein-Maxwell equations, proposed by Ida to include charged perfect
fluid sources. We impose the equation of state $\rho+3p=0$ and discuss
spherically symmetric solutions for the linear potential equation satisfied by
the metric. In this particular case the fluid charge density vanishes and we
locate the arising neutral perfect fluid in the intermediate region defined by
two thin shells with respective charges $Q$ and $-Q$. With its innermost flat
and external (Schwarzschild) asymptotically flat spacetime regions, the
resultant condenser-like geometries resemble solutions discussed by Cohen and
Cohen in a different context. We explore this relationship and point out an
exotic gravitational property of our neutral perfect fluid. We mention possible
continuations of this study to embrace non-spherically symmetric situations and
higher dimensional spacetimes.


title: Radiating Levi-Civita Spacetime

abstract:
  This paper has been withdrawn by the author, See J.Krishna Rao, J. Phys. A:
Gen. Phys., 4, 17 (1971) for radiating Levi-Civita metric.


title: A Mass Dependent String-Quintessence Model at the Planck Scale

abstract:
  This paper was withdrawn by arXiv admin due to authors' misrepresentation of
identity/affiliation.


title:
Signal based vetoes for the detection of gravitational waves from
  inspiralling compact binaries

abstract:
  The matched filtering technique is used to search for gravitational wave
signals of a known form in the data taken by ground-based detectors. However,
the analyzed data contains a number of artifacts arising from various
broad-band transients (glitches) of instrumental or environmental origin which
can appear with high signal-to-noise ratio on the matched filtering output.
This paper describes several techniques to discriminate genuine events from the
false ones, based on our knowledge of the signals we look for. Starting with
the $\chi^2$ discriminator, we show how it may be optimized for free
parameters. We then introduce several alternative vetoing statistics and
discuss their performance using data from the GEO600 detector.


title: Homogeneous cosmologies from the quasi-Maxwell formalism

abstract:
  We show how to use the quasi-Maxwell formalism to obtain solutions of
Einstein's field equations corresponding to homogeneous cosmologies - namely
Einstein's universe, Godel's universe and the Ozsvath-Farnsworth-Kerr class I
solutions - written in frames for which the associated observers are
stationary.


title: A Background Independent Description of Physical Processes

abstract:
  A mathematical structure is presented that allows one to define a physical
process independent of any background. That is, it is possible, for a set of
objects, to choose an object from that set through a choice process that is
defined solely in terms of the objects in the set itself. It is conjectured
that this background free structure is a necessary ingredient for a
self-consistent description of physical processes and that these same physical
processes are determined by the absence of any background. The properties of
the mathematical structure, denoted Q, are equivalent to the three-dimensional
topological manifold 2T^3 + 3(S^1 x S^2), two three-tori plus three handles,
embedded in four dimensions. The topology of Q reproduces the basic properties
of QED and Einstein gravity.


title: The Higgs sector of gravitational gauge theories

abstract:
  Gravitational gauge theories with de Sitter, Poincare and affine symmetry
group are investigated under the aspect of the breakdown of the initial
symmetry group down to the Lorentz subgroup. We review the theory of
spontaneously broken de Sitter gravity by Stelle and West and apply a similar
approach to the case of the Poincare and affine groups. Especially, we find
that the groundstate of the metric affine theory leads to the determination of
the Lorentzian signature of the metric in the groundstate. We show that the
Higgs field remains in its groundstate, i.e., that the metric will have
Lorentzian signature, unless we introduce matter fields that explicitely couple
to the symmetric part of the connection. We also show that some features, like
the necessity of the introduction of a dilaton field, that seem artificial in
the context of the affine theory, appear most natural if the gauge group is
taken to be the special linear group in five dimensions. Finally, we present an
alternative model which is based on the spinor representation of the Lorentz
group and is especially adopted to the description of spinor fields in a
general linear covariant way, without the use of the infinite dimensional
representations which are usually considered to be unavoidable.


title: D/antiD Dark Energy in String Warped Compactification

abstract:
  We study the evolution of relic D3-branes after the D3/\bd-brane inflation in
string warped compactification. The motion of D3-branes can be frozen under
certain condition during the radiation/matter domination. These D3-branes can
not be released until the D3/\bd-branes potential energy becomes dominated at
late time. Subsequently they will move towards to \bd-branes, which play the
role of uplifting AdS minimum to dS minimum, near the apex of throats. The
annihilation of D3/\bd-branes leads to the disappearance of dS vacua. This
process may be regarded as a rapid decay channel of present dS vacua. We
discuss the parameter spaces required by this process and calculate the decay
time.


title: Post-Einsteinian tests of linearized gravitation

abstract:
  The general relativistic treatment of gravitation can be extended by
preserving the geometrical nature of the theory but modifying the form of the
coupling between curvature and stress tensors. The gravitation constant is thus
replaced by two running coupling constants which depend on scale and differ in
the sectors of traceless and traced tensors. When calculated in the solar
system in a linearized approximation, the metric is described by two
gravitation potentials. This extends the parametrized post-Newtonian (PPN)
phenomenological framework while allowing one to preserve compatibility with
gravity tests performed in the solar system. Consequences of this extension are
drawn here for phenomena correctly treated in the linear approximation. We
obtain a Pioneer-like anomaly for probes with an eccentric motion as well as a
range dependence of Eddington parameter $\gamma$ to be seen in light deflection
experiments.


title: Slice Energy and Theories of Gravitation

abstract:
  We review recent work on the use of the slice energy concept in generalized
theories of gravitation. We focus on two special features in these theories,
namely, the energy exchange between the matter component and the scalar field
generated by the conformal transformation to the Einstein frame of such
theories and the issue of the physical equivalence of different conformal frame
representations. We show that all such conformally-related, generalized
theories of gravitation allow for the slice energy to be invariably defined and
its fundamental properties be insensitive to conformal transformations.


title: Cylindrical Collapse and Gravitational Waves

abstract:
  We study the matching conditions for a collapsing anisotropic cylindrical
perfect fluid, and we show that its radial pressure is non zero on the surface
of the cylinder and proportional to the time dependent part of the field
produced by the collapsing fluid. This result resembles the one that arises for
the radiation - though non-gravitational - in the spherically symmetric
collapsing dissipative fluid, in the diffusion approximation.


title:
Quasinormal modes of Dirac field perturbation in Schwarzschild-anti-de
  Sitter black hole

abstract:
  The quasinormal modes (QNMs) associated with the decay of Dirac field
perturbation around a Schwarzschild-anti-de Sitter (SAdS) black hole is
investigated by using Horowitz-Hubeny approach. We find that both the real and
the imaginary parts of the fundamental quasinormal frequencies for large black
holes are linear functions of the Hawking temperature, and the real part of the
fundamental quasinormal frequencies for intermediate and small black holes
approximates a temperature curve and the corresponding imaginary part is almost
a linear function of the black hole radius. The angular quantum number has the
surprising effect of increasing the damping time scale and decreasing the
oscillation time scale for intermediate and small black holes. We also find
that the rates between quasinormal frequencies and black hole radii for large,
intermediate and small black holes are linear functions of the overtone number,
i. e., all the modes are evenly spaced.


title:
Dirac quasinormal frequencies of Reissner-Nordstr\"om black hole in
  Anti-de Sitter spacetime

abstract:
  The quasinormal modes (QNMs) of Dirac field perturbations of a
Reissner-Nordstr\"om black hole in an asymptotically Anti-de Sitter spacetime
are investigated. We find that both the real and imaginary parts of the
fundamental quasinormal frequencies for large black holes are the linear
functions of the Hawking temperature, and the slope of the lines for the real
parts decreases while that for the magnitude of the imaginary parts increases
as the black hole charge increases. According to the Anti-de Sitter/Conformal
Field Theory (AdS/CFT) correspondence, the fact shows that different charge
presents different time scale in three-dimensional CFT. Another interesting
result is that the quasinormal frequencies become evenly spaced for high
overtone number, and in the spacing expressions the real part decreases while
the magnitude of the imaginary part increases as the charge increases. We also
study the relation between quasinormal frequencies and angular quantum number
and find that the real part increases while the magnitude of the imaginary part
decreases as the angular quantum number increases.


title: Static axisymmetric space-times with prescribed multipole moments

abstract:
  In this article we develop a method of finding the static axisymmetric
space-time corresponding to any given set of multipole moments. In addition to
an implicit algebraic form for the general solution, we also give a power
series expression for all finite sets of multipole moments. As conjectured by
Geroch we prove in the special case of axisymmetry, that there is a static
space-time for any given set of multipole moments subject to a (specified)
convergence criterion. We also use this method to confirm a conjecture of
Hernandez-Pastora and Martin concerning the monopole-quadropole solution.


title: Taub, Rindler, and the static plate

abstract:
  An infinite 3D plate of homogeneous incompressible fluid is considered, with
finite thickness, together with a 2D infinite homogeneous mass in its centre.
Einstein equations are exactly solved, in the interior of the 3D mass. The
solution is joined to the exterior vacuum metric of Taub. Every value for the
2D mass, positive or negative, allows a perfect junction. Also the joining to a
vacuum metric of Rindler is shown; if an imperfect joining is allowed, then
again every value of the 2D mass is possible. Some of our results contradict
assertions foun in the literature. The text is also available in English by
e-mail, ask the author.
  --
  Estu nefinhava 3D-a plato de unuforma nepremebla fluido, kun finhava diko,
kune kun nefinhava 2D-a plano de unuforma maso en /gia mezo. Ekvacioj de
Einstein estas ekzakte solvataj, ene la 3D-a maso. La solvo estas kunigata al
la malena metriko de vakuo, de Taub. /Ciu valoro por la 2D-a maso, pozitiva a/u
negativa, permesas perfektan kunigon. Anka/u la kunigo al la metriko de vakuo
de Rindler estas montrata; se neperfekta kunigo estas akceptata, denove /ciu
valoro de la 2D-a maso estas ebla. Kelke da niaj rezultoj kontra/udiras
asertojn findatajn en la literaturo.


title: The Letelier-Gal'tsov spacetime revisited

abstract:
  Contrary to a recent claim by Anderson ["The Mathematical Theory of Cosmic
Strings", I.O.P. Publishing, Bristol 2003], we show that the Letelier-Gal'tsov
metric does represent a system of crossed straight infinite cosmic strings
moving with arbitrary constant velocities.


title: Phase space geometry in scalar-tensor cosmology

abstract:
  We study the phase space of spatially homogeneous and isotropic cosmology in
general scalar-tensor theories. A reduction to a two-dimensional phase space is
performed when possible-in these situations the phase space is usually a
two-dimensional curved surface embedded in a three-dimensional space and
composed of two sheets attached to each other, possibly with complicated
topology. The results obtained are independent of the choice of the coupling
function of the theory and, in certain situations, also of the potential.


title: Quantum Cosmology and the Arrow of Time

abstract:
  Although most fundamental laws are invariant under time reversal, experience
exhibits the presence of irreversible phenomena -- the arrows of time. Their
origin lies in cosmology, and I argue that only quantum cosmology can provide
the appropriate formal framework. After briefly reviewing the formalism, I
discuss how a simple and natural boundary condition can lead to the observed
arrows of time. This yields at the same time interesting consequences for black
holes.


title: Gravitational Radiation from Cylindrical Naked Singularity

abstract:
  We construct an approximate solution which describes the gravitational
emission from a naked singularity formed by the gravitational collapse of a
cylindrical thick shell composed of dust. The assumed situation is that the
collapsing speed of the dust is very large. In this situation, the metric
variables are obtained approximately by a kind of linear perturbation analysis
in the background Morgan solution which describes the motion of cylindrical
null dust. The most important problem in this study is what boundary conditions
for metric and matter variables should be imposed at the naked singularity. We
find a boundary condition that all the metric and matter variables are
everywhere finite at least up to the first order approximation. This implies
that the spacetime singularity formed by this high-speed dust collapse is very
similar to that formed by the null dust and thus the gravitational emission
from a naked singularity formed by the cylindrical dust collapse can be gentle.


title: Dark energy and quantum entanglement

abstract:
  Entangled states in the universe may change interpretation of observations
and even revise the concept of dark energy.


title: Abelian Gauge Theory in de Sitter Space

abstract:
  Quantization of spinor and vector free fields in 4-dimensional de Sitter
space-time, in the ambient space notation, has been studied in the previous
works. Various two-points functions for the above fields are presented in this
paper. The interaction between the spinor field and the vector field is then
studied by the abelian gauge theory. The U(1) gauge invariant spinor field
equation is obtained in a coordinate independent way notation and their
corresponding conserved currents are computed. The solution of the field
equation is obtained by use of the perturbation method in terms of the Green's
function. The null curvature limit is discussed in the final stage.


title:
On the possibility of measuring the post-Newtonian gravitoelectric
  correction to the orbital period of a test body in a Solar System scenario

abstract:
  The possibility of measuring the post-Newtonian gravitoelectric correction to
the orbital period of a test particle freely orbiting a spherically symmetric
mass in the Solar System is analyzed. It should be possible, in principle, to
detect it for Mercury at a precision level of 10^-4. This level is mainly set
by the unavoidable systematic errors due to the mismodelling in the Keplerian
period which could not be reduced by accumulating a large number of orbital
revolutions. Future missions like Messenger and BepiColombo should allow to
improve it by increasing our knowledge of the Mercury's orbital parameters. The
observational accuracy is estimated to be 10^-4 from the knowledge of the
International Celestial Reference Frame (ICRF) axes. It could be improved by
observing as many planetary transits as possible. It is not possible to measure
such an effect in the gravitational field of the Earth by analyzing the motion
of artificial satellites or the Moon because of the unavoidable systematic
errors related to the uncertainties in the Keplerian periods. In the case of
some recently discovered exoplanets the problems come from the observational
errors which are larger than the relativistic effect.


title: Poincare Connections in Flat Spacetime

abstract:
  In flat spacetime, as a simple 4-vector, a particle's 4-velocity cannot be
changed by translation. Parallel translation then produces constant velocity,
motion without force. Here we consider a richer, but less well-known,
representation of the Poincare group of symmetries of flat spacetime in which
translation adds a non-linear connection term to the 4-vector. Then 4-vectors
can be meaningfully parallel translated, curved geodesics can be developed, and
the curvature for the connection can be found. By adding an assumption, that
the arc length is calculated with a position dependent metric, it is shown that
a geodesic has a 4-acceleration which is the sum of a Christoffel connection
term and a term that is the scalar product of 4-velocity and an antisymmetric
tensor. This is just like the force law obeyed by a charged, massive particle
in general relativity. Thus the dynamical laws of electrodynamics and general
relativity can be deduced as geodesic equations from the way particle proper
time depends on position and the way 4-vectors can change upon translation in
flat spacetime.


title: Discrete Symmetries for Spinor Field in de Sitter Space

abstract:
  Discrete symmetries, parity, time reversal, antipodal, and charge conjugation
transformations for spinor field in de Sitter space, are presented in the
ambient space notation, i.e. in a coordinate independent way. The PT and PCT
transformations are also discussed in this notation. The five-current density
is studied and their transformation under the discrete symmetries is discussed.


title: Dirac Quasinormal modes of Schwarzschild black hole

abstract:
  The quasinormal modes (QNMs) associated with the decay of Dirac field
perturbation around a Schwarzschild black hole is investigated by using
continued fraction and Hill-determinant approaches. It is shown that the
fundamental quasinormal frequencies become evenly spaced for large angular
quantum number and the spacing is given by $\omega_{\lambda+1}-
\omega_{\lambda}=0.38490-0.00000i$. The angular quantum number has the
surprising effect of increasing real part of the quasinormal frequencies, but
it almost does not affect imaginary part, especially for low overtones. In
addition, the quasinormal frequencies also become evenly spaced for large
overtone number and the spacing for imaginary part is
$Im(\omega_{n+1})-Im(\omega_n)\approx -i/4M$ which is same as that of the
scalar, electromagnetic, and gravitational perturbations.


title:
Non-asymptotically flat, non-dS/AdS dyonic black holes in dilaton
  gravity

abstract:
  We present exact spherically symmetric dyonic black hole solutions in
four-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type
potentials for the dilaton field. These solutions have unusual
asymptotics--they are neither asymptotically flat nor asymptotically (anti-) de
Sitter. The solutions have one or two horizons hiding a curvature singularity
at the origin. A class of topological dyonic black holes with topology of a
torus is also presented. Some basic properties of the black holes are
discussed.


title: Holographic Cosmology and Uncertainty Relation

abstract:
  It is believed that a primary principle of the theory of quantum gravity is
the Holographic Principle according to which a physical system can be described
only by degrees of freedom living on its boundary. The generalized covariant
formulation of the principle considers the entropy content on truncated
light-sheets: light-like hypersurfaces of non-positive expansion orthogonally
generated from a boundary. When we construct the truncated light-sheets for
cosmological observers we find a general expression for the minimum cosmic time
interval from the apparent horizon to verify the holographic prescription; this
minimum time is related to quantum effects involved in the entropy computation.
Finally, we arrive to the uncertainty relation from the Holographic Principle,
which suggests a deep connection between general covariance, entropy bounds and
quantum mechanics.


title: Manybody treatment of white dwarf and neutron stars on the brane

abstract:
  Brane-World models suggest modification of Newton's law of gravity on the
3-brane at submillimeter scales. The brane-world induced corrections are in
higher powers of inverse distance and appear as additional terms with the
Newtonian potential. The average inter-particle distance in white dwarf and
neutron stars are $10^{-10} cms$ and $10^{-13} cms$ respectively, and
therefore, the effect of submillimeter corrections needs to be investigated. We
show, by carrying out simple manybody calculations, that the mass and
mass-radius relationship of the white dwarf and neutron stars are not effected
by submillimeter corrections. However, our analysis shows that the correction
terms in the effective theory give rise to force akin to surface tension in
normal liquids.


title:
Expansion of the universe from a 5D vacuum within a nonperturbative
  scalar field formalism

abstract:
  We study the dynamics of the quantum scalar field responsible for inflation
in different epochs of the evolution of the universe by using a recently
introduced nonperturbative formalism from a 5D apparent vacuum.


title:
Gravitational perturbations of the Schwarzschild spacetime: A practical
  covariant and gauge-invariant formalism

abstract:
  We present a formalism to study the metric perturbations of the Schwarzschild
spacetime. The formalism is gauge invariant, and it is also covariant under
two-dimensional coordinate transformations that leave the angular coordinates
unchanged. The formalism is applied to the typical problem of calculating the
gravitational waves produced by material sources moving in the Schwarzschild
spacetime. We examine the radiation escaping to future null infinity as well as
the radiation crossing the event horizon. The waveforms, the energy radiated,
and the angular-momentum radiated can all be expressed in terms of two
gauge-invariant scalar functions that satisfy one-dimensional wave equations.
The first is the Zerilli-Moncrief function, which satisfies the Zerilli
equation, and which represents the even-parity sector of the perturbation. The
second is the Cunningham-Price-Moncrief function, which satisfies the
Regge-Wheeler equation, and which represents the odd-parity sector of the
perturbation. The covariant forms of these wave equations are presented here,
complete with covariant source terms that are derived from the stress-energy
tensor of the matter responsible for the perturbation. Our presentation of the
formalism is concluded with a separate examination of the monopole and dipole
components of the metric perturbation.


title: Comment on Phys. Rev. D 60 084017 "Classical self-force" by F. Rohrlich

abstract:
  F. Rohrlich has recently published two papers, including the paper under
review, advocating a particular delay-differential equation as an approximate
equation of motion for classical charged particles, which he characterizes as
providing a "fully acceptable classical electrodynamics". This Comment notes
some mathematical and physical problems with this equation. It points out that
most of the claims of these papers are unproved, while some appear to be false
as stated.


title: A note on dilaton gravity with non-smooth potentials

abstract:
  Recent interest in brane world models motivates the investigation of generic
first order dilaton gravity actions, with potentials having some
non-smoothness. We consider two different types of \delta-like contributions in
the action and analyse their effects on the solutions. Furthermore a second
source of non-smoothness arises due to the remaining ambiguities in the
solutions in the separated smooth patches, after fixing all other constants by
matching and asymptotic conditions. If moreover staticity is assumed, we
explicitly construct exact solutions.
  With the methods described, for example models with point like sources or
brane world models (where the second source of non-smoothness becomes crucial),
can now be treated as non-smooth dilaton gravity theories.


title: Inhomogeneous space-times and their energy distributions

abstract:
  This paper also has excessove overlap with the following papers also written
by the authors or their collaborators: gr-qc/0502060, gr-qc/0606028,
gr-qc/0511095, gr-qc/0505078, gr-qc/0603044, gr-qc/0608014, gr-qc/0510123,
gr-qc/0607109, gr-qc/0602012, and others.


title: The Dynamics of Photon in the Shuwer: A Class of Solutions

abstract:
  This paper has excessive overlap with the following papers also written by
the authors or their collaborators: gr-qc/0502059, gr-qc/0502061,
gr-qc/0510037, gr-qc/0510038, gr-qc/0207026, and others.


title: Variables separation in gravity

abstract:
  To solve the problem of exact integration of the field equations or equations
of motion of matter in curved spacetimes one can use a class of Riemannian
metrics for which the simplest equations of motion can be integrated by the
complete separation of variables method. Here, we consider the particular case
of the class of Stackel metrics. These metrics admit integration of the
Hamilton-Jacobi equation for test particle by the complete separation of
variables method. It appears that the other important equations of motion
(Klein-Gordon-Fock, Dirac, Weyl) in curved spacetimes can be integrated by
complete separation of variables method only for the metrics, belonging to the
class of Stackel spaces.


title:
The periodic standing-wave approximation: nonlinear scalar fields,
  adapted coordinates, and the eigenspectral method

abstract:
  The periodic standing wave (PSW) method for the binary inspiral of black
holes and neutron stars computes exact numerical solutions for periodic
standing wave spacetimes and then extracts approximate solutions of the
physical problem, with outgoing waves. The method requires solution of a
boundary value problem with a mixed (hyperbolic and elliptic) character.
  We present here a new numerical method for such problems, based on three
innovations: (i) a coordinate system adapted to the geometry of the problem,
(ii) an expansion in multipole moments of these coordinates and a filtering out
of higher moments, and (iii) the replacement of the continuum multipole moments
with their analogs for a discrete grid. We illustrate the efficiency and
accuracy of this method with nonlinear scalar model problems. Finally, we take
advantage of the ability of this method to handle highly nonlinear models to
demonstrate that the outgoing approximations extracted from the standing wave
solutions are highly accurate even in the presence of strong nonlinearities.


title: Accelerated Levi-Civita-Bertotti-Robinson Metric in D-Dimensions

abstract:
  A conformally flat accelerated charge metric is found in an arbitrary
dimension $D$. It is a solution of the Einstein-Maxwell-null fluid with a
cosmological constant in $D \ge 4$ dimensions. When the acceleration is zero
our solution reduces to the Levi-Civita-Bertotti-Robinson metric. We show that
the charge loses its energy, for all dimensions, due to the acceleration.


title: Particle scattering in loop quantum gravity

abstract:
  We devise a technique for defining and computing n-point functions in the
context of a background-independent gravitational quantum field theory. We
construct a tentative implementation of this technique in a
perturbatively-finite loop/spinfoam model.


title:
A strongly hyperbolic and regular reduction of Einstein's equations for
  axisymmetric spacetimes

abstract:
  This paper is concerned exclusively with axisymmetric spacetimes. We want to
develop reductions of Einstein's equations which are suitable for numerical
evolutions. We first make a Kaluza-Klein type dimensional reduction followed by
an ADM reduction on the Lorentzian 3-space, the (2+1)+1 formalism. We include
also the Z4 extension of Einstein's equations adapted to this formalism. Our
gauge choice is based on a generalized harmonic gauge condition. We consider
vacuum and perfect fluid sources.
  We use these ingredients to construct a strongly hyperbolic first-order
evolution system and exhibit its characteristic structure. This enables us to
construct constraint-preserving stable outer boundary conditions. We use
cylindrical polar coordinates and so we provide a careful discussion of the
coordinate singularity on axis. By choosing our dependent variables
appropriately we are able to produce an evolution system in which each and
every term is manifestly regular on axis.


title:
Denseness of Ashtekar-Lewandowski states and a generalized cut-off in
  loop quantum gravity

abstract:
  We show that the set of states of the Ashtekar-Isham-Lewandowski holonomy
algebra defined by elements of the Ashtekar-Lewandowski Hilbert space is dense
in the space of all states. We consider weak convergence properties of a
modified version of the cut-off procedure currently in use in loop quantum
gravity. This version is adapted to vector states rather than to general
distributions.


title:
Post-Newtonian gravitational radiation and equations of motion via
  direct integration of the relaxed Einstein equations. III. Radiation reaction
  for binary systems with spinning bodies

abstract:
  Using post-Newtonian equations of motion for fluid bodies that include
radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5]
and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for
binary systems with spinning bodies. In particular we determine the effects of
radiation-reaction coupled to spin-orbit effects on the two-body equations of
motion, and on the evolution of the spins. For a suitable definition of spin,
we reproduce the standard equations of motion and spin-precession at the first
post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced
reaction effects on the orbital motion, but we find that radiation damping has
no effect on either the magnitude or the direction of the spins. Using the
equations of motion, we find that the loss of total energy and total angular
momentum induced by spin-orbit effects precisely balances the radiative flux of
those quantities calculated by Kidder et al. The equations of motion may be
useful for evolving inspiraling orbits of compact spinning binaries.


title: Simple Analytic Models of Gravitational Collapse

abstract:
  Most general relativity textbooks devote considerable space to the simplest
example of a black hole containing a singularity, the Schwarzschild geometry.
However only a few discuss the dynamical process of gravitational collapse, by
which black holes and singularities form. We present here two types of analytic
models for this process, which we believe are the simplest available; the first
involves collapsing spherical shells of light, analyzed mainly in
Eddington-Finkelstein coordinates; the second involves collapsing spheres
filled with a perfect fluid, analyzed mainly in Painleve-Gullstrand
coordinates. Our main goal is pedagogical simplicity and algebraic
completeness, but we also present some results that we believe are new, such as
the collapse of a light shell in Kruskal-Szekeres coordinates.


title: Stationary Black Holes

abstract:
  We review the theory of stationary black hole solutions of vacuum Einstein
equations.


title:
Relative Energy-Momentum of the Bianchi-I Type Universes in Teleparallel
  Gravity

abstract:
  This paper has been removed by arXiv administrators because it plagiarizes
gr-qc/0011027, gr-qc/0205028, and gr-qc/0303034.


title:
The Momentum 4-Vector Imparted by Gravitational Waves in Bianchi-type
  Metrics

abstract:
  This paper has been removed by arXiv administrators because it plagiarizes
gr-qc/0008034, "The Energy Distribution of the Bianchi Type I Universe," by I.
Radinschi; Phys. Rev. D 41, 1086 (1990), "Energy associated with a Kerr-Newman
black hole," by K.S. Virbhadra; and Braz. J. Phys. 30, 181 (2000), "On The
Localization Of The Gravitational Energy," by N.P. Neto and P.I. Trajtenberg.


title:
Quantum evolution of the Universe from $\tau=0$ in the constrained
  quasi-Heisenberg picture

abstract:
  The Heisenberg picture of the minisuperspace model is considered. The
suggested quantization scheme interprets all the observables including the
Universe scale factor as the (quasi)Heisenberg operators. The operators arise
as a result of the re-quantization of the Heisenberg operators that is required
to obtain the hermitian theory. It is shown that the DeWitt constraint H=0 on
the physical states of the Universe does not prevent a time-evolution of the
(quasi)Heisenberg operators and their mean values. Mean value of an observable,
which is singular in a classical theory, is also singular in a quantum case.
The (quasi)Heisenberg operator equations are solved in an analytical form in a
first order on the interaction constant for the quadratic inflationary
potential. Operator solutions are used to evaluate the observables mean values
and dispersions. A late stage of the inflation is considered numerically in the
framework of the Wigner-Weyl phase-space formalism. It is found that the
dispersions of the observables do not vanish at the inflation end.


title: Elementary Model of Constraint Quantization with an Anomaly

abstract:
  Quantum gravity is made more difficult in part by its constraint structure.
The constraints are classically first-class; however, upon quantization they
become partially second-class. To study such behavior, we focus on a simple
problem with finitely many degrees of freedom and demonstrate how the
projection operator formalism for dealing with quantum constraints is well
suited to this type of example.


title: Gravitational quasinormal modes for Kerr Anti-de Sitter black holes

abstract:
  We investigate the quasinormal modes for gravitational perturbations of
rotating black holes in four dimensional Anti-de Sitter (AdS) spacetime. The
study of the quasinormal frequencies related to these modes is relevant to the
AdS/CFT correspondence. Although results have been obtained for Schwarzschild
and Reissner-Nordstrom AdS black holes, quasinormal frequencies of Kerr-AdS
black holes are computed for the first time. We solve the Teukolsky equations
in AdS spacetime, providing a second order and a Pade approximation for the
angular eigenvalues associated to the Teukolsky angular equation. The
transformation theory and the Regge-Wheeler-Zerilli equations for Kerr-AdS are
obtained.


title: On the gravitational field induced by static electromagnetic sources

abstract:
  It is argued that static electromagnetic sources induce
Weyl-Majumdar-Papapetrou solutions for the spacetime metric. The acceleration
in such fields has a term many orders of magnitude stronger than usual
perturbative terms. Two electrostatic and two magnetostatic examples are given.


title: Feynman diagams coupled to three-dimensional quantum gravity

abstract:
  A framework for quantum field theory coupled to three-dimensional quantum
gravity is proposed. The coupling with quantum gravity regulates the Feynman
diagrams. One recovers the usual Feynman amplitudes in the limit as the
cosmological constant tends to zero.


title: Electrovac $pp$-waves

abstract:
  New exact solutions of the Einstein-Maxwell field equations that describe
$pp$-waves are presented.


title: Topological gravity on plumbed V-cobordisms

abstract:
  An ensemble of cosmological models based on generalized BF-theory is
constructed where the role of vacuum (zero-level) coupling constants is played
by topologically invariant rational intersection forms (cosmological-constant
matrices) of 4-dimensional plumbed V-cobordisms which are interpreted as
Euclidean spacetime regions. For these regions describing topology changes, the
rational and integer intersection matrices are calculated. A relation is found
between the hierarchy of certain elements of these matrices and the hierarchy
of coupling constants of the universal (low-energy) interactions.
  PACS numbers: 0420G, 0240, 0460


title:
Integrating the geodesic equations in the Schwarzschild and Kerr
  space-times using Beltrami's "geometrical" method

abstract:
  We revisit a little known theorem due to Beltrami, through which the
integration of the geodesic equations of a curved manifold is accomplished by a
method which, even if inspired by the Hamilton-Jacobi method, is purely
geometric. The application of this theorem to the Schwarzschild and Kerr
metrics leads straightforwardly to the general solution of their geodesic
equations. This way of dealing with the problem is, in our opinion, very much
in keeping with the geometric spirit of general relativity. In fact, thanks to
this theorem we can integrate the geodesic equations by a geometrical method
and then verify that the classical conservation laws follow from these
equations.


title: Confusion Noise from Extreme-Mass-Ratio Inspirals

abstract:
  Captures of compact objects (COs) by massive black holes in galactic nuclei
(aka ``extreme-mass-ratio inspirals'') will be an important source for LISA.
However, a large fraction of captures will not be individually resolvable, and
so will constitute a source of ``confusion noise,'' obscuring other types of
sources. Here we estimate the shape and overall magnitude of the spectrum of
confusion noise from CO captures. The overall magnitude depends on the capture
rates, which are rather uncertain, so we present results for a plausible range
of rates. We show that the impact of capture confusion noise on the total LISA
noise curve ranges from insignificant to modest, depending on these rates.
Capture rates at the high end of estimated ranges would raise LISA's overall
(effective) noise level by at most a factor $\sim 2$. While this would somewhat
decrease LISA's sensitivity to other classes of sources, it would be a pleasant
problem for LISA to have, overall, as it would also imply that detection rates
for CO captures were at nearly their maximum possible levels (given LISA's
baseline design).


title: Nutty dyons

abstract:
  We argue that the Einstein-Yang-Mills-Higgs theory presents nontrivial
solutions with a NUT charge. These solutions approach asymptotically the
Taub-NUT spacetime and generalize the known dyon black hole configurations. The
main properties of the solutions and the differences with respect to the
asymptotically flat case are discussed. We find that a nonabelian magnetic
monopole placed in the field of gravitational dyon necessarily acquires an
electric field, while the magnetic charge may take arbitrary values.


title: Microwave apparatus for gravitational waves observation

abstract:
  In this report the theoretical and experimental activities for the
development of superconducting microwave cavities for the detection of
gravitational waves are presented.


title: Readings of the Lichnerowicz-York equation

abstract:
  James York, in a major extension of Andr\'e Lichnerowicz's work, showed how
to construct solutions to the constraint equations of general relativity. The
York method consists of choosing a 3-metric on a given manifold; a
divergence-free, tracefree (TT) symmetric 2-tensor wrt this metric; and a
single number, the trace of the extrinsic curvature. One then obtains a
quasi-linear elliptic equation for a scalar function, the Lichnerowicz-York
(L-Y) equation. The solution of this equation is used as a conformal factor to
transform the data into a set that satisfies the constraints. If the manifold
is compact and without boundary, one quantity that emerges is the volume of the
physical space. This article reinterprets the L-Y equation as an eigenvalue
equation so as to get a set of data with a preset physical volume. One chooses
the conformal metric, the TT tensor, and the physical volume, while regarding
the trace of the extrinsic curvature as a free parameter. The resulting
equation has extremely nice uniqueness and existence properties. A even more
radical approach would be to fix the base (conformal) metric, the physical
volume, and the trace. One also selects a TT tensor, but one is free to
multiply it by a constant(unspecified). One then solves the L-Y equation as an
eigenvalue equation for this constant. A third choice would be to fix the TT
tensor and and multiply the base metric by a constant. Each of these three
formulations has good uniqueness and existence properties.


title: Threshold of Singularity Formation in the Semilinear Wave Equation

abstract:
  Solutions of the semilinear wave equation are found numerically in three
spatial dimensions with no assumed symmetry using distributed adaptive mesh
refinement. The threshold of singularity formation is studied for the two cases
in which the exponent of the nonlinear term is either $p=5$ or $p=7$. Near the
threshold of singularity formation, numerical solutions suggest an approach to
self-similarity for the $p=7$ case and an approach to a scale evolving static
solution for $p=5$.


title:
On the Energy-Momentum Densities of the Cylindrically Symmetric
  Gravitational Waves

abstract:
  In this study, using Moller and Tolman prescriptions we calculate energy and
momentum densities for the general cylindrically symmetric spacetime metric. We
find that results are finite and well defined in these complexes. We also give
the results for some cylindrically symmetric spacetime models.


title: Energy Distribution in LTB Space-time

abstract:
  This paper has been removed by arXiv administrators because it overlaps
hep-th/0308070, and others.
  This paper also has excessive overlap with the following paper also written
by the authors or their collaborators: gr-qc/0506061.


title:
On the Equivalence of the Massless DKP equation and the Maxwell
  Equations in the Shuwer

abstract:
  This paper has been removed by arXiv administrators because it plagiarizes
P.K. Jena, P.C. Naik and T. Pradhan, "Photon As The Zero Mass Limit Of Dkp
Field," J. Phys. A 13, 2975 (1980) [not cited within submission]. In addition,
the following submissions by the authors and their collaborators all contain a
great deal of overlap: gr-qc/0502059, gr-qc/0502061, gr-qc/0207026,
hep-th/0110228, and hep-th/0207088.


title:
Energy-Momentum in viscous Kasner-type Universe in Bergmann-Thomson
  Formulations

abstract:
  This paper has been removed by arXiv administrators because it plagiarizes
gr-qc/0303034, "The energy of the universe in teleparallel gravity," by T.
Vargas; and gr-qc/0011027, "Viscous cosmologies in scalar-tensor theories for
Kasner type metrics," by M. Cataldo, S. del Campo and P. Salgado.


title: The Massless Spin-1 Particles in the Rotating Space-times

abstract:
  This paper has been removed by arXiv administrators because it plagiarizes
P.K. Jena, P.C. Naik and T. Pradhan, "Photon As The Zero Mass Limit Of Dkp
Field," J. Phys. A {\bf 13}, 2975 (1980) [not cited within submission]. In
addition, the following submissions by the authors and their collaborators all
contain a great deal of overlap: gr-qc/0502059, gr-qc/0502061, gr-qc/0207026,
hep-th/0110228, and hep-th/0207088.


title: Periastron shift in Weyl class spacetimes

abstract:
  The periastron position advance for geodesic motion in axially symmetric
solutions of the Einstein field equations belonging to the Weyl class of vacuum
solutions is investigated. Explicit examples corresponding to either static
solutions (single Chazy-Curzon, Schwarzschild and a pair of them), or
stationary solution (single rotating Chazy-Curzon and Kerr black hole) are
discussed. The results are then applied to the case of S2-SgrA$^*$ binary
system of which the periastron position advance will be soon measured with a
great accuracy.


title:
Second order perturbations of rotating bodies in equilibrium; the
  exterior vacuum problem

abstract:
  We study the exterior vacuum problem for first and second order stationary
and axially symmetric perturbations of static bodies. The boundary conditions
and their compatibility for the existence of an asymptotically flat exterior
solution are discussed.


title:
Gauge-invariant Non-spherical Metric Perturbations of Schwarzschild
  Black-Hole Spacetimes

abstract:
  The theory of gauge-invariant non-spherical metric perturbations of
Schwarzschild black hole spacetimes is now well established. Yet, as different
notations and conventions have been used throughout the years, the literature
on the subject is often confusing and sometimes confused. The purpose of this
paper is to review and collect the relevant expressions related to the
Regge-Wheeler and Zerilli equations for the odd and even-parity perturbations
of a Schwarzschild spacetime. Special attention is paid to the form they assume
in the presence of matter-sources and, for the two most popular conventions in
the literature, to the asymptotic expressions and gravitational-wave
amplitudes. Besides pointing out some inconsistencies in the literature, the
expressions collected here could serve as a quick reference for the calculation
of the perturbations of Schwarzschild black hole spacetimes driven by generic
sources and for those approaches in which gravitational waves are extracted
from numerically generated spacetimes.


title:
Quasinormal modes of Kerr-Newman black holes: coupling of
  electromagnetic and gravitational perturbations

abstract:
  We compute numerically the quasinormal modes of Kerr-Newman black holes in
the scalar case, for which the perturbation equations are separable. Then we
study different approximations to decouple electromagnetic and gravitational
perturbations of the Kerr-Newman metric, computing the corresponding
quasinormal modes. Our results suggest that the Teukolsky-like equation derived
by Dudley and Finley gives a good approximation to the dynamics of a rotating
charged black hole for Q<M/2. Though insufficient to deal with Kerr-Newman
based models of elementary particles, the Dudley-Finley equation should be
adequate for astrophysical applications.


title: Metric Redefinitions in Einstein-Aether Theory

abstract:
  `Einstein-Aether' theory, in which gravity couples to a dynamical, time-like,
unit-norm vector field, provides a means for studying Lorentz violation in a
generally covariant setting. Demonstrated here is the effect of a redefinition
of the metric and vector field in terms of the original fields and two free
parameters. The net effect is a change of the coupling constants appearing in
the action. Using such a redefinition, one of the coupling constants can be set
to zero, simplifying studies of solutions of the theory.


title: Conformal thin-sandwich puncture initial data for boosted black holes

abstract:
  We apply the puncture approach to conformal thin-sandwich black-hole initial
data. We solve numerically the conformal thin-sandwich puncture (CTSP)
equations for a single black hole with non-zero linear momentum. We show that
conformally flat solutions for a boosted black hole have the same maximum
gravitational radiation content as the corresponding Bowen-York solution in the
conformal transverse-traceless decomposition. We find that the physical
properties of these data are independent of the free slicing parameter.


title:
The impact of the new Earth gravity models on the measurement of the
  Lense-Thirring effect with a new satellite

abstract:
  In this paper we investigate the opportunities offered by the new Earth
gravity models from the dedicated CHAMP and, especially, GRACE missions to the
project of measuring the general relativistic Lense-Thirring effect with a new
Earth's artificial satellite. It turns out that it would be possible to abandon
the stringent, and expensive, requirements on the orbital geometry of the
originally prosed LARES mission (same semimajor axis a=12270 km of the existing
LAGEOS and inclination i=70 deg) by inserting the new spacecraft in a
relatively low, and cheaper, orbit (a=7500-8000 km, i\sim 70 deg) and suitably
combining its node Omega with those of LAGEOS and LAGEOS II in order to cancel
out the first even zonal harmonic coefficients of the multipolar expansion of
the terrestrial gravitational potential J_2, J_4 along with their temporal
variations. The total systematic error due to the mismodelling in the remaining
even zonal harmonics would amount to \sim 1% and would be insensitive to
departures of the inclination from the originally proposed value of many
degrees. No semisecular long-period perturbations would be introduced because
the period of the node, which is also the period of the solar K_1 tidal
perturbation, would amount to \sim 10^2 days. Since the coefficient of the node
of the new satellite would be smaller than 0.1 for such low altitudes, the
impact of the non-gravitational perturbations of it on the proposed combination
would be negligible. Then, a particular financial and technological effort for
suitably building the satellite in order to minimize the non-conservative
accelerations would be unnecessary.


title: Hoffmann-Infeld Black Hole Solutions in Lovelock Gravity

abstract:
  Five-dimensional black holes are studied in Lovelock gravity coupled to
Hoffmann-Infeld non-linear electrodynamics. It is shown that some of these
solutions present a double peak behavior of the temperature as a function of
the horizon radius. This feature implies that the evaporation process, though
drastic for a period, leads to an eternal black hole remnant. Moreover, the
form of the caloric curve corresponds to the existence of a plateau in the
evaporation rate, which implies that black holes of intermediate scales turn
out to be unstable. The geometrical aspects, such as the absence of conical
singularity, the structure of horizons, etc. are also discussed. In particular,
solutions that are asymptotically AdS arise for special choices of the
parameters, corresponding to charged solutions of five-dimensional Chern-Simons
gravity.