title:
Normal Coordinates Describing Coupled Oscillations in the Gravitational
  Field

abstract:
  The motion of a local source inducing small oscillations in the gravitational
field is investigated and shown to exhibit pure rotational kinetic energy.
Should the net affect of these slow, revolving oscillations cause large-scale
rotations in spacetime it would certainly result in anomalous celestial
accelerations. When this angular rotational frequency of spacetime is applied
to the anomalous acceleration of the Pioneer 10/11 spacecrafts, the correlation
is promising.


title:
Equivalence principle and experimental tests of gravitational spin
  effects

abstract:
  We study the possibility of experimental testing the manifestations of
equivalence principle in spin-gravity interactions. We reconsider the earlier
experimental data and get the first experimental bound on anomalous
gravitomagnetic moment. The spin coupling to the Earth's rotation may also be
explored at the extensions of neutron EDM and g-2 experiments. The spin
coupling to the terrestrial gravity produces a considerable effect which may be
discovered at the planned deuteron EDM experiment. The Earth's rotation should
also be taken into account in optical experiments on a search for axionlike
particles.


title: Loop quantum cosmology of k=1 FRW models

abstract:
  The closed, k=1, FRW model coupled to a massless scalar field is investigated
in the framework of loop quantum cosmology using analytical and numerical
methods. As in the k=0 case, the scalar field can be again used as emergent
time to construct the physical Hilbert space and introduce Dirac observables.
The resulting framework is then used to address a major challenge of quantum
cosmology: resolving the big-bang singularity while retaining agreement with
general relativity at large scales. It is shown that the framework fulfills
this task. In particular, for states which are semi-classical at some late
time, the big-bang is replaced by a quantum bounce and a recollapse occurs at
the value of the scale factor predicted by classical general relativity. Thus,
the `difficulties' pointed out by Green and Unruh in the k=1 case do not arise
in a more systematic treatment. As in k=0 models, quantum dynamics is
deterministic across the deep Planck regime. However, because it also retains
the classical recollapse, in contrast to the k=0 case one is now led to a
cyclic model. Finally, we clarify some issues raised by Laguna's recent work
addressed to computational physicists.


title: The quintessence scalar field in the relativistic theory of gravity

abstract:
  The variant of the quintessence theory is proposed in order to get an
accelerated expansion of the Friedmannian Universe in the frameworks of
relativistic theory of gravitation. The substance of quintessence is built up
the scalar field of dark energy. It is shown, that function V(Phi), which
factorising scalar field Lagrangian (Phi is a scalar field) has no influence on
the evolution of the Universe. Some relations, allowing to find explicit
dependence Phi on time, were found, provided given function V(Phi).


title: The Vierbein Formalism and Energy-Momentum Tensor of Spinors

abstract:
  To study the coupling system of space-time and Fermions, we need the explicit
form of the energy-momentum tensor of spinors. The energy-momentum tensor is
closely related to the tetrad frames which cannot be uniquely determined by the
metric. This flexibility increases difficulties to derive the exact expression
and easily leads to ambiguous results. In this paper, we give a detailed
derivation for the energy-momentum tensor of Weyl and Dirac spinors. From the
results we find that, besides the usual kinetic energy momentum term, there are
three kinds of other additional terms. One is the nonlinear self-interactive
potential, which acts like negative pressure. The other reflects the
interaction of momentum $p^\mu$ with tetrad. The third is the spin-gravity
coupling term which is a higher order infinitesimal in weak field, but may be
important in a neutron star. This term is also closely related with magnetic
field of a celestial body. These results are based on the decomposition of
usual spin connection into geometrical part and dynamical part, which not only
makes calculation simpler, but also highlights their different physical
meanings. In addition, we get a new tensor $S^{\mu\nu}_{ab}$ in calculation of
tetrad formalism, which plays an important role in the interaction of spinor
with gravity.


title:
Search For Gravitational Waves Through the Electromagnetic Faraday
  Rotation

abstract:
  A method is given which renders indirect detection of strong gravitational
waves possible. This is based on the reflection (collision) of a linearly
polarized electromagnetic shock wave from (with) a cross polarized impulsive
and shock gravitational waves in accordance with the general theory of
relativity. This highly non-linear process induces a detectable Faraday
rotation in the polarization vector of the electromagnetic field.


title: Gravitational waves generated by second order effects during inflation

abstract:
  The generation of gravitational waves during inflation due to the non-linear
coupling of scalar and tensor modes is discussed. Two methods describing
gravitational wave perturbations are used and compared: a covariant and local
approach, as well as a metric-based analysis based on the Bardeen formalism. An
application to slow-roll inflation is also described.


title: On Newman-Penrose constants of stationary space-times

abstract:
  We consider the general asymptotic expression of stationary space-time. Using
Killing equation, we reduce the dynamical freedom of Einstein equation to the
in-going gravitational wave $\Psi_0$. The general form of this function can be
got. With the help of asymptotically algebraic special condition, we prove that
all Newman-Penrose constants vanish.


title: Space-time in light of Karolyhazy uncertainty relation

abstract:
  General relativity and quantum mechanics provide a natural explanation for
the existence of dark energy with its observed value and predict its dynamics.
Dark energy proves to be necessary for the existence of space-time itself and
determines the rate of its stability.


title: Some comments on the universal constant in DSR

abstract:
  Deformed Special Relativity is usually presented as a deformation of Special
Relativity accommodating a new universal constant, the Planck mass, while
respecting the relativity principle. In order to avoid some fundamental
problems (e.g. soccer ball problem), we argue that we should switch point of
view and consider instead the Newton constant $G$ as the universal constant.


title: Non-flat universe and interacting dark energy model

abstract:
  For non-flat universe of $k\not=0$, we investigate a model of the interacting
holographic dark energy with cold dark matter (CDM). There exists a mixture of
two components arisen from decaying of the holographic dark energy into CDM. In
this case we use the effective equations of state ($\omega^{\rm eff}_{\rm
\Lambda}, \omega^{\rm eff}_{\rm m}$) instead of the native equations of state
($\omega_{\rm \Lambda},\omega_{\rm m})$.
  Consequently, we show that interacting holographic energy models in non-flat
universe cannot accommodate a transition from the dark energy to the phantom
regime.


title: Field Theories found Geometrically from Embeddings in Flat Frame Bundles

abstract:
  We present two families of exterior differential systems (EDS) for
non-isometric embeddings of orthonormal frame bundles over Riemannian spaces of
dimension q = 2, 3, 4, 5.... into orthonormal frame bundles over flat spaces of
sufficiently higher dimension. We have calculated Cartan characters showing
that these EDS satisfy Cartan's test and are well-posed dynamical field
theories. The first family includes a constant-coefficient (cc) EDS for
classical Einstein vacuum relativity (q = 4). The second family is generated
only by cc 2-forms, so these are integrable (but nonlinear) systems of partial
differential equations. These calibrated field theories apparently are new,
although the simplest case q = 2 turns out to embed a ruled surface of
signature (1,1) in flat space of signature (2,1). Cartan forms are found to
give explicit variational principles for all these dynamical theories.


title: Fluctuations of CMBR in accelerating universe

abstract:
  The influence of the observed relict vacuum energy on the fluctuations of
CMBR going through cosmological matter condensations is studied in the
framework of the Einstein-Strauss-de Sitter vakuola model. It is shown that
refraction of light at the matching surface of the vakuola and the expanding
Friedman universe can be very important during accelerated expansion of the
universe, when the velocity of the matching surface relative to static
Schwarzchildian observers becomes relativistic. Relevance of the refraction
effect for the temperature fluctuations of CMBR is given in terms of the
redshift and the angular extension of the fluctuating region.


title: Gravitation theory in Riemann-Cartan space-time and regular cosmology

abstract:
  Principal ideas of gauge approach applying to gravitational interaction and
leading to gravitation theory in Riemann-Cartan space-time are discussed. The
principal relations of isotropic cosmology built in the framework of the
Poincare gauge theory of gravity and the most important their consequences are
presented.


title:
Homogeneous isotropic cosmological models with pseudoscalar torsion
  function in Poincare gauge theory of gravity and accelerating Universe

abstract:
  The "dark energy" problem is investigated in the framework of the Poincare
gauge theory of gravity in 4-dimensional Riemann-Cartan space-time. By using
general expression for gravitational Lagrangian homogeneous isotropic
cosmological models with pseudoscalar torsion function are built and
investigated. It is shown that by certain restrictions on indefinite parameters
of gravitational Lagrangian the cosmological equations at asymptotics contain
effective cosmological constant and can lead to observable acceleration of
cosmological expansion. This effect has geometrical nature and is connected
with space-time torsion.


title:
Binary black hole late inspiral: Simulations for gravitational wave
  observations

abstract:
  Coalescing binary black hole mergers are expected to be the strongest
gravitational wave sources for ground-based interferometers, such as the LIGO,
VIRGO, and GEO600, as well as the space-based interferometer LISA. Until
recently it has been impossible to reliably derive the predictions of General
Relativity for the final merger stage, which takes place in the strong-field
regime. Recent progress in numerical relativity simulations is, however,
revolutionizing our understanding of these systems. We examine here the
specific case of merging equal-mass Schwarzschild black holes in detail,
presenting new simulations in which the black holes start in the late inspiral
stage on orbits with very low eccentricity and evolve for ~1200M through ~7
orbits before merging. We study the accuracy and consistency of our simulations
and the resulting gravitational waveforms, which encompass ~14 cycles before
merger, and highlight the importance of using frequency (rather than time) to
set the physical reference when comparing models. Matching our results to PN
calculations for the earlier parts of the inspiral provides a combined waveform
with less than half a cycle of accumulated phase error through the entire
coalescence. Using this waveform, we calculate signal-to-noise ratios (SNRs)
for iLIGO, adLIGO, and LISA, highlighting the contributions from the
late-inspiral and merger-ringdown parts of the waveform which can now be
simulated numerically. Contour plots of SNR as a function of z and M show that
adLIGO can achieve SNR >~ 10 for some intermediate-mass binary black holes
(IMBBHs) out to z ~ 1, and that LISA can see massive binary black holes (MBBHs)
in the range 3x10^4 <~ M/M_Sun <~ 10^7 at SNR > 100 out to the earliest epochs
of structure formation at z > 15.


title:
Hamiltonian formulation of the 5-D Kaluza-Klein model and test-particle
  motion

abstract:
  We examine the ADM reformulation of the 5-D KK model: the dimensional
reduction is provided to commute with the ADM splitting and we show how the
time component of the gauge vector is given by combination of the Lagrangian
multipliers for the 5-D gravitational field. We consider 5D particles motion
and after dimensional reduction the definition of charge is recovered within
electrodynamic coupling. A time-varying fine structure constant is recognized
because an extra scalar field is present in the 4-D theory.


title: Charged Black Hole in a Canonical Ensemble

abstract:
  We consider the thermodynamics of a charged black hole enclosed in a cavity.
The charge in the cavity and the temperature at the walls are fixed so that we
have a canonical ensemble. We derive the phase structure and stability of black
hole equilibrium states. We compare our results to that of other work which
uses asymptotically anti-de Sitter boundary conditions to define the
thermodynamics. The thermodynamic properties have extensive similarities which
suggest that the idea of AdS holography is more dependent on the existence of
the boundary than on the exact details of asymptotically AdS metrics.


title: Reheating of the universe after inflation with f(phi)R gravity

abstract:
  We show that reheating of the universe occurs spontaneously in a broad class
of inflation models with f(phi)R gravity (phi is inflaton). The model does not
require explicit couplings between phi and bosonic or fermionic matter fields.
The couplings arise spontaneously when phi settles in the vacuum expectation
value (vev) and oscillates, with coupling constants given by derivatives of
f(phi) at the vev and the mass of resulting bosonic or fermionic fields. This
mechanism allows inflaton quanta to decay into any fields which are not
conformally invariant in f(phi)R gravity theories.


title:
A general variational principle for spherically symmetric perturbations
  in diffeomorphism covariant theories

abstract:
  We present a general method for the analysis of the stability of static,
spherically symmetric solutions to spherically symmetric perturbations in an
arbitrary diffeomorphism covariant Lagrangian field theory. Our method involves
fixing the gauge and solving the linearized gravitational field equations to
eliminate the metric perturbation variable in terms of the matter variables. In
a wide class of cases--which include f(R) gravity, the Einstein-aether theory
of Jacobson and Mattingly, and Bekenstein's TeVeS theory--the remaining
perturbation equations for the matter fields are second order in time. We show
how the symplectic current arising from the original Lagrangian gives rise to a
symmetric bilinear form on the variables of the reduced theory. If this
bilinear form is positive definite, it provides an inner product that puts the
equations of motion of the reduced theory into a self-adjoint form. A
variational principle can then be written down immediately, from which
stability can be tested readily. We illustrate our method in the case of
Einstein's equation with perfect fluid matter, thereby re-deriving, in a
systematic manner, Chandrasekhar's variational principle for radial
oscillations of spherically symmetric stars. In a subsequent paper, we will
apply our analysis to f(R) gravity, the Einstein-aether theory, and
Bekenstein's TeVeS theory.


title:
Numerical Spherically Symmetric Static Solution of the RTG Equations
  Outside the Matter

abstract:
  There was obtained a numerical external solution for the exact system of the
RTG equations with some natural boundary conditions in the static spherically
symmetric case. The properties of the solution are discussed.


title:
Gravitational waves from Extreme Mass Ratio Inspirals in non-pure Kerr
  spacetimes

abstract:
  To investigate the imprint on the gravitational-wave emission from extreme
mass-ratio inspirals in non-pure Kerr spacetimes, we have studied the
``kludge'' waveforms generated in highly-accurate, numerically-generated
spacetimes containing a black hole and a self-gravitating, homogeneous torus
with comparable mass and spin. In order to maximize their impact on the
produced waveforms, we have considered tori that are compact, massive and close
to the central black hole, investigating under what conditions the LISA
experiment could detect their presence. Our results show that for a large
portion of the space of parameters the waveforms produced by EMRIs in these
black hole-torus systems are indistinguishable from pure-Kerr waveforms. Hence,
a ``confusion problem'' will be present for observations carried out over a
timescale below or comparable to the dephasing time.


title: A virtual trip to the Schwarzschild-de Sitter black hole

abstract:
  We developed realistic fully general relativistic computer code for
simulation of optical projection in a strong, spherically symmetric
gravitational field. Standard theoretical analysis of optical projection for an
observer in the vicinity of a Schwarzschild black hole is extended to black
hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de
Sitter spacetimes. Influence of the cosmological constant is investigated for
static observers and observers radially free-falling from static radius.
Simulation includes effects of gravitational lensing, multiple images, Doppler
and gravitational frequency shift, as well as the amplification of intensity.
The code generates images of static observers sky and a movie simulations for
radially free-falling observers. Techniques of parallel programming are applied
to get high performance and fast run of the simulation code.


title: Faddeev-Jackiw quantization of spin-2 field

abstract:
  We apply the Faddeev-Jackiw method to the Hamiltonian analysis of the
massless spin-two field. As expected, the reduced Hamiltonian contains only the
traceless-transverse tensor, while some, but not all of the non-propagating
components are determined by the constraints of the theory. In particular, it
is concluded that no gauge choice can be imposed on the fields such that only
the propagating modes remain in the theory, meaning that for the spin-2 field
there is no direct analogue to the Coulomb gauge of electromagnetism.
Implications for General Relativity are discussed.


title: Bianchi -I Cosmology with Magnetic Field in Lyra Geometry

abstract:
  A new class of Bianchi - I cosmological model with magnetic field within the
frame work of Lyra geometry has been presented . Exact solutions to the field
equations for the model are obtained . The physical and kinematical behaviors
of the model have been discussed.


title:
Quantum Gravity Through Non-Perturbative Renormalization Group and
  Improved Black Hole

abstract:
  Usually, General Relativity (GR) is known to be unrenormalizable
perturbatively from the viewpoint of quantum field theory. But in the modern
sense of renormalizability, there still remains the possibility to investigate
whether GR is "nonpertubatively" renormalizable or not. Here I review the
basics and results in this topic based on the "Effective Average Action"
approach which was proposed by M.Reuter, and discuss its application to the
balck hole geometry.


title: A Strong Constraint on Ever-Present Lambda

abstract:
  We show that the causal set approach to creating an ever-present cosmological
'constant' in the expanding universe is strongly constrained by the isotropy of
the microwave background. Fluctuations generated by stochastic lambda
generation which are consistent with COBE and WMAP observations are far too
small to dominate the expansion dynamics at z<1000 and so cannot explain the
observed late-time acceleration of the universe. We also discuss other
observational constraints from the power spectrum of galaxy clustering and show
that the theoretical possibility of ever-present lambda arises only in 3+1
dimensional space-times.


title: Brane Lorentz Symmetry from Lorentz Breaking in the Bulk

abstract:
  We propose the mechanism of spontaneous symmetry breaking of a bulk vector
field as a way to generate the selection of bulk dimensions invisible to the
standard model confined to the brane. By assigning a non-vanishing vacuum value
to the vector field, a direction is singled out in the bulk vacuum, thus
breaking the bulk Lorentz symmetry. We present the condition for induced
Lorentz symmetry on the brane, as phenomenologically required.


title:
Displacement power spectrum measurement of a macroscopic optomechanical
  system at thermal equilibrium

abstract:
  The mirror relative motion of a suspended Fabry-Perot cavity is studied in
the frequency range 3-10 Hz. The experimental measurements presented in this
paper, have been performed at the Low Frequency Facility, a high finesse
optical cavity 1 cm long suspended to a mechanical seismic isolation system
identical to that one used in the VIRGO experiment. The measured relative
displacement power spectrum is compatible with a system at thermal equilibrium
within its environmental. In the frequency region above 3 Hz, where seismic
noise contamination is negligible, the measurement distribution is stationary
and Gaussian, as expected for a system at thermal equilibrium. Through a simple
mechanical model it is shown that: applying the fluctuation dissipation theorem
the measured power spectrum is reproduced below 90 Hz and noise induced by
external sources are below the measurement.


title: The relativistic glider

abstract:
  We present a purely relativistic effect according to which asymmetric
oscillations of a quasi-rigid body slow down or accelerate its fall in a
gravitational background.


title: Broken Scale Invariance and Quintessence (a quarter of a century ago)

abstract:
  The cosmological consequences of a simple scalar field model for the
generation of Newton's constant through the spontaneous breaking of scale
invariance in a curved space-time are again presented and discussed. Such a
model leads to a consistent description wherein the introduction of matter
introduces a small perturbation on a de Sitter universe and a time dependence
of the gravitational coupling.


title:
The evolution of tensor perturbations in scalar-tensor theories of
  gravity

abstract:
  The evolution equations for tensor perturbations in a generic scalar tensor
theory of gravity are presented. Exact solution are given for a specific class
of theories and Friedmann-Lema\^{i}tre-Robertson-Walker backgrounds. In these
cases it is shown that, although the evolution of tensor models depends on the
choice of parameters of the theory, no amplification is possible if the
gravitational interaction is attractive.


title: From Quantum Hydrodynamics to Quantum Gravity

abstract: We discuss some lessons from quantum hydrodynamics to quantum gravity.


title: Worse than a big rip?

abstract:
  We show that a generalised phantom Chaplygin gas can present a future
singularity in a finite future cosmic time. Unlike the big rip singularity,
this singularity happens for a finite scale factor, but like the big rip
singularity, it would also take place at a finite future cosmic time. In
addition, we define a dual of the generalised phantom Chaplygin gas which
satisfies the null energy condition. Then, in a Randall-Sundrum 1 brane-world
scenario, we show that the same kind of singularity at a finite scale factor
arises for a brane filled with a dual of the generalised phantom Chaplygin gas.


title:
A Simplified Mathematical Model for the Formation of Null Singularities
  Inside Black Holes I - Basic Formulation and a Conjecture

abstract:
  Einstein's equations are known to lead to the formation of black holes and
spacetime singularities. This appears to be a manifestation of the mathematical
phenomenon of finite-time blowup: a formation of singularities from regular
initial data. We present a simple hyperbolic system of two semi-linear
equations inspired by the Einstein equations. We explore a class of solutions
to this system which are analogous to static black-hole models. These solutions
exhibit a black-hole structure with a finite-time blowup on a characteristic
line mimicking the null inner horizon of spinning or charged black holes. We
conjecture that this behavior - namely black-hole formation with blow-up on a
characteristic line - is a generic feature of our semi-linear system. Our
simple system may provide insight into the formation of null singularities
inside spinning or charged black holes in the full system of Einstein
equations.


title: Invariants of Spin Networks Embedded in Three-Manifolds

abstract:
  We study the invariants of spin networks embedded in a three-dimensional
manifold which are based on the path integral for SU(2) BF-Theory. These
invariants appear naturally in Loop Quantum Gravity, and have been defined as
spin-foam state sums. By using the Chain-Mail technique, we give a more general
definition of these invariants, and show that the state-sum definition is a
special case. This provides a rigorous proof that the state-sum invariants of
spin networks are topological invariants. We derive various results about the
BF-Theory spin network invariants, and we find a relation with the
corresponding invariants defined from Chern-Simons Theory, i.e. the
Witten-Reshetikhin-Turaev invariants. We also prove that the BF-Theory spin
network invariants coincide with V. Turaev's definition of invariants of
coloured graphs embedded in 3-manifolds and thick surfaces, constructed by
using shadow-world evaluations. Our framework therefore provides a unified view
of these invariants.


title: Reduction of a Quantum Theory

abstract:
  This paper serves as a preparation of work that focuses on extracting
cosmological sectors from Loop Quantum Gravity. We start with studying the
extraction of subsystems from classical systems. A classical Hamiltonian system
can be reduced to a subsystem of ''relevant observables'' using the pull-back
under the Poisson-embedding of the ''relevant part of phase space'' into full
phase space. Since a quantum theory can be thought of as a noncommutative phase
space, one encounters the problem of embedding noncommutative spaces. We solve
this problem for a physically interesting set of quantum systems and embeddings
by constructing the noncommutative analogue of the construction of an embedding
as the projection to the base space of an embedding of fibre bundles over the
involved spaces. This paper focuses on the physical ideas that enter our
programme of reduction of quantum theories and tries to explain these on
examples rather than abstractly, which will be the focus of a forthcoming
paper.


title: Conservation of energy and Gauss Bonnet gravity

abstract:
  It is shown how can be made the classification of all tensors constructed
from the Riemann tensor that verify the conservation of gravitational energy
momentum. More precisely we explain that there exists a unique tensor of degree
n in the Riemann tensor and its contractions that verifies the conservation of
energy. We show that this tensor, only because it obeys this degree n structure
as well as energy conservation, two facts which are true in all dimensions,
verifies in dimension 2n this striking particularity of being Euler gravity. We
stick here to the case n=2 but explain briefly why the general case is similar.


title: A gravito-electromagnetic analogy based on tidal tensors

abstract:
  We propose a new approach to a physical analogy between General Relativity
and Electromagnetism, based on tidal tensors of both theories. Using this
approach we write a covariant form for the gravitational analogues of the
Maxwell equations. The following realisations of the analogy are given. The
first one matches linearised gravitational tidal tensors to exact
electromagnetic tidal tensors in Minkwoski spacetime. The second one matches
exact magnetic gravitational tidal tensors for ultra-stationary metrics to
exact magnetic tidal tensors of electromagnetism in curved spaces. In the third
we show that our approach leads to two-step exact derivation of the Papapetrou
force on a gyroscope. We then establish a new proof for a class of tensor
identities that define invariants of the type $\vec{E}^2-\vec{B}^2$ and
$\vec{E}\cdot\vec{B}$, and we exhibit the invariants built from tidal tensors
in both gravity and electromagnetism. We contrast our approach with the two
gravito-electromagnetic analogies commonly found in the literature, and argue
that it sheds light on the debate about the limit of validity of one of the
analogies, and clarifies issues concerning the physical interpretation of the
other.


title: Gauge and General Relativity

abstract:
  One of the main features of covariant theories, in particular general
relativity, is that the field equation possesses gauge freedom associated with
global diffeomorphisms of the underlying manifold. I shall explain here how the
hole argument is a reflection of this gauge freedom.
  Finally I shall point out some implications of the hole argument and extend
the hole argument to the case of permutable theories. As covariant theories
provides a general mathematical framework for classical physics, permutable
theories provide the language for quantum physics. Permutable theories are
defined functorially on the category of sets and permutations with values into
the category of fibered sets and fiber-preserving automorphisms, and rules of
selecting sections. The hole argument for permutable theories is intimately
related with the individuation problem of the base elements (e.g., elementary
particles). This is a consequence of the fact that the automorphisms of the
base space provides the gauge freedom of the fields.


title: Merger of black hole-neutron star binaries: nonspinning black hole case

abstract:
  We perform a simulation for merger of a black hole (BH)-neutron star (NS)
binary in full general relativity preparing a quasicircular state as initial
condition. The BH is modeled by a moving puncture with no spin and the NS by
the $\Gamma$-law equation of state with $\Gamma=2$. Corotating velocity field
is assumed for the NS. The mass of the BH and the rest-mass of the NS are
chosen to be $\approx 3.2 M_{\odot}$ and $\approx 1.4 M_{\odot}$ with
relatively large radius of the NS $\approx 14$ km. The NS is tidally disrupted
near the innermost stable orbit but $\sim 80%$ of the material is swallowed
into the BH with small disk mass $\sim 0.3M_{\odot}$ even for such small BH
mass $\sim 3M_{\odot}$. The result indicates that the system of a BH and a
massive disk of $\sim M_{\odot}$ is not formed from nonspinning BH-NS binaries,
although a disk of mass $\sim 0.1M_{\odot}$ is a possible outcome.


title: On the possibility of finite quantum Regge calculus

abstract:
  The arguments were given in a number of our papers that the discrete quantum
gravity based on the Regge calculus possesses nonzero vacuum expectation values
of the triangulation lengths of the order of Plank scale $10^{-33}cm$. These
results are considered paying attention to the form of the path integral
measure showing that probability distribution for these linklengths is
concentrated at certain nonzero finite values of the order of Plank scale. That
is, the theory resembles an ordinary lattice field theory with fixed spacings
for which correlators (Green functions) are finite, UV cut off being defined by
lattice spacings. The difference with an ordinary lattice theory is that now
lattice spacings (linklengths) are themselves dynamical variables, and are
concentrated around certain Plank scale values due to {\it dynamical} reasons.


title: Three Dimensional Loop Quantum Gravity: Particles and the Quantum Double

abstract:
  It is well known that the quantum double structure plays an important role in
three dimensional quantum gravity coupled to matter field. In this paper, we
show how this algebraic structure emerges in the context of three dimensional
Riemannian loop quantum gravity (LQG) coupled to a finite number of massive
spinless point particles. In LQG, physical states are usually constructed from
the notion of SU(2) cylindrical functions on a Riemann surface $\Sigma$ and the
Hilbert structure is defined by the Ashtekar-Lewandowski measure. In the case
where $\Sigma$ is the sphere $S^2$, we show that the physical Hilbert space is
in fact isomorphic to a tensor product of simple unitary representations of the
Drinfeld double DSU(2): the masses of the particles label the simple
representations, the physical states are tensor products of vectors of simple
representations and the physical scalar product is given by intertwining
coefficients between simple representations. This result is generalized to the
case of any Riemann surface $\Sigma$.


title:
Three dimensional Loop Quantum Gravity: towards a self-gravitating
  Quantum Field Theory

abstract:
  In a companion paper, we have emphasized the role of the Drinfeld double
DSU(2) in the context of three dimensional Riemannian Loop Quantum Gravity
coupled to massive spinless point particles. We make use of this result to
propose a model for a self-gravitating quantum field theory (massive spinless
non-causal scalar field) in three dimensional Riemannian space. We start by
constructing the Fock space of the free self-gravitating field: the vacuum is
the unique DSU(2) invariant state, one-particle states correspond to DSU(2)
unitary irreducible simple representations and any multi-particles states is
obtained as the symmetrized tensor product between simple representations. The
associated quantum field is defined by the usual requirement of covariance
under DSU(2). Then, we introduce a DSU(2)-invariant self-interacting potential
(the obtained model is a Group Field Theory) and compute explicitely the lowest
order terms (in the self-interaction coupling constant $\lambda$) of the
propagator and of the three-points function. Finally, we compute the lowest
order quantum gravity corrections (in the Newton constant G) to the propagator
and to the three-points function.


title: Cosmological perturbations on local systems

abstract:
  We study the effect of cosmological expansion on orbits--galactic, planetary,
or atomic--subject to an inverse-square force law. We obtain the laws of motion
for gravitational or electrical interactions from general relativity--in
particular, we find the gravitational field of a mass distribution in an
expanding universe by applying perturbation theory to the Robertson-Walker
metric. Cosmological expansion induces an ($\ddot a/a) \vec r$ force where
$a(t)$ is the cosmological scale factor. In a locally Newtonian framework, we
show that the $(\ddot a/a) \vec r$ term represents the effect of a continuous
distribution of cosmological material in Hubble flow, and that the total force
on an object, due to the cosmological material plus the matter perturbation,
can be represented as the negative gradient of a gravitational potential whose
source is the material actually present. We also consider the effect on local
dynamics of the cosmological constant. We calculate the perihelion precession
of elliptical orbits due to the cosmological constant induced force, and work
out a generalized virial relation applicable to gravitationally bound clusters.


title: Spectral Analysis of the Volume Operator in Loop Quantum Gravity

abstract:
  We describe preliminary results of a detailed numerical analysis of the
volume operator as formulated by Ashtekar and Lewandowski. Due to a simplified
explicit expression for its matrix elements, it is possible for the first time
to treat generic vertices of valence greater than four. It is found that the
vertex geometry characterizes the volume spectrum.


title: Back-reaction of Cosmological Fluctuations during Power-Law Inflation

abstract:
  We study the renormalized energy-momentum tensor of cosmological scalar
fluctuations during the slow-rollover regime for power-law inflation and find
that it is characterized by a negative energy density at the leading order,
with the same time behaviour as the background energy. The average expansion
rate appears decreased by the back-reaction of the effective energy of
cosmological fluctuations, but this value is comparable with the energy of
background only if inflation starts at a Planckian energy. We also find that,
for this particular model, the first and second order inflaton fluctuations are
decoupled and satisfy the same equation of motion. To conclude, the fourth
order adiabatic expansion for the inflaton scalar field is evaluated for a
general potential V(\phi).


title:
How far away is far enough for extracting numerical waveforms, and how
  much do they depend on the extraction method?

abstract:
  We present a method for extracting gravitational waves from numerical
spacetimes which generalizes and refines one of the standard methods based on
the Regge--Wheeler--Zerilli perturbation formalism. [abridged] We then present
fully nonlinear three-dimensional numerical evolutions of a distorted
Schwarzschild black hole in Kerr--Schild coordinates with an odd parity
perturbation and analyze the improvement we gain from our generalized wave
extraction, comparing our new method to the standard one. [abridged]
  We find that, even with observers as far out as $R=80 M$--which is larger
than what is commonly used in state-of-the-art simulations--the assumption in
the standard method that the background is close to having Schwarzschild-like
coordinates increases the error in the extracted waveforms considerably. Even
for our coarsest resolutions, our new method decreases the error by between one
and two orders of magnitudes. Furthermore, we explicitly see that the errors in
the extracted waveforms obtained by the standard method do not converge to zero
with increasing resolution. [abridged]
  In a general scenario, for example a collision of compact objects, there is
no precise definition of gravitational radiation at a finite distance, and
gravitational wave extraction methods at such distances are thus inherently
approximate. The results of this paper bring up the possibility that different
choices in the wave extraction procedure at a fixed and finite distance may
result in relative differences in the waveforms which are actually larger than
the numerical errors in the solution.


title: An explicit harmonic code for black-hole evolution using excision

abstract:
  We describe an explicit in time, finite-difference code designed to simulate
black holes by using the excision method. The code is based upon the harmonic
formulation of the Einstein equations and incorporates several features
regarding the well-posedness and numerical stability of the initial-boundary
problem for the quasilinear wave equation. After a discussion of the equations
solved and of the techniques employed, we present a series of testbeds carried
out to validate the code. Such tests range from the evolution of isolated black
holes to the head-on collision of two black holes and then to a binary black
hole inspiral and merger. Besides assessing the accuracy of the code, the
inspiral and merger test has revealed that individual apparent horizons can
touch and even intersect. This novel feature in the dynamics of the marginally
trapped surfaces is unexpected but consistent with theorems on the properties
of apparent horizons.


title: Binary black hole merger waveforms in the extreme mass ratio limit

abstract:
  We discuss the transition from quasi-circular inspiral to plunge of a system
of two nonrotating black holes of masses $m_1$ and $m_2$ in the extreme mass
ratio limit $m_1m_2\ll (m_1+m_2)^2$. In this limit, we compare the merger
waveforms obtained by two different methods: a {\it numerical}
(Regge-Wheeler-Zerilli) one, and an {\it analytical} (Effective One Body) one.
This is viewed as a contribution to the matching between analytical and
numerical methods.


title: LISA and LISA PathFinder, the endeavour to detect low frequency GWs

abstract:
  This is a review about LISA and its technology demonstrator, LISA PathFinder.
We first describe the conceptual problems which need to be overcome in order to
set up a working interferometric detector of low frequency Gravitational Waves
(GW), then summarise the solutions to them as currently conceived by the LISA
mission team. This will show that some of these solutions require new
technological abilities which are still under development, and which need
proper test before being fully implemented. LISA PathFinder (LPF) is the the
testbed for such technologies. The final part of the paper will address the
ideas and concepts behind the PathFinder as well as their impact on LISA.


title: In-flight Diagnostics in LISA Pathfinder

abstract:
  LISA PathFinder (LPF) will be flown with the objective to test in space key
technologies for LISA. However its sensitivity goals are, for good reason, one
order of magnitude less than those which LISA will have to meet, both in
drag-free and optical metrology requirements, and in the observation frequency
band. While the expected success of LPF will of course be of itself a major
step forward to LISA, one might not forget that a further improvement by an
order of magnitude in performance will still be needed. Clues for the last leap
are to be derived from proper disentanglement of the various sources of noise
which contribute to the total noise, as measured in flight during the
PathFinder mission. This paper describes the principles, workings and
requirements of one of the key tools to serve the above objective: the
diagnostics subsystem. This consists in sets of temperature, magnetic field,
and particle counter sensors, together with generators of controlled thermal
and magnetic perturbations. At least during the commissioning phase, the latter
will be used to identify feed-through coefficients between diagnostics sensor
readings and associated actual noise contributions. A brief progress report of
the current state of development of the diagnostics subsystem will be given as
well.


title: Does phantom energy produce black hole?

abstract:
  We have found an exact solution of spherically symmetrical Einstein equations
describing a black hole with a special type phantom energy source. It is
surprising to note that our solution is analogous to Reissner-Nordstr\"{o}m
black hole.


title: Galileo Symmetries in Polymer Particle Representation

abstract:
  To illustrate the conceptual problems for the low-energy symmetries in the
continuum of spacetime emerging from the discrete quantum geometry, Galileo
symmetries are investigated in the polymer particle representation of a
non-relativistic particle as a simple toy model. The complete Galileo
transformations (translation, rotation and Galileo boost) are naturally defined
in the polymer particle Hilbert space and Galileo symmetries are recovered with
highly suppressed deviations in the low-energy regime from the underlying
polymer particle description.


title: Is life a thermal horizon ?

abstract:
  This talk aims at questioning the vanishing of Unruh temperature for an
inertial observer in Minkovski spacetime with finite lifetime, arguing that in
the non eternal case the existence of a causal horizon is not linked to the
non-vanishing of the acceleration. This is illustrated by a previous result,
the diamonds temperature, that adapts the algebraic approach of Unruh effect to
the finite case.


title:
Friedmann Robertson-Walker model in generalised metric space-time with
  weak anisotropy

abstract:
  A generalized model of space-time is given, taking into consideration the
anisotropic structure of fields which are depended on the position and the
direction (velocity).In this framework a generalized FRW-metric the
Raychaudhouri and Friedmann equations are studied.A long range vector field of
cosmological origin is considered in relation to the physical geometry of
space-time in which Cartan connection has a fundamental role.The generalised
Friedmann equations are produced including anisotropic terms.The variation of
anisotropy $z_t$ is expressed in terms of the Cartan torsion tensor of the
Finslerian space-time.A possible estimation of the anisotropic parameter $z_t$
can be achieved with the aid of the de-Sitter model of the empty flat universe
with weak anisotropy. Finally a physical generalisation for the model of
inflation is also studied.


title:
Characteristics of Quantum Radiation of Slowly Varying Nonstationary
  Kerr-Newman Black Holes

abstract:
  Quantum radiative characteristics of slowly varying nonstationary Kerr-Newman
black holes are investigated by using the method of generalized tortoise
coordinate transformation. It is shown that the temperature and the shape of
the event horizon of this kind of black holes depend on the time and the angle.
Further, we reveal a relationship that is ignored before between thermal
radiation and non-thermal radiation, which is that the chemical potential in
thermal radiation spectrum is equal to the highest energy of the negative
energy state of particles in non-thermal radiation for slowly varying
nonstationary Kerr-Newman black holes. Also, we show that the deduced general
results can be degenerated to the known conclusion of stationary Kerr-Newman
black holes.


title: Is violation of Newton's second law possible?

abstract:
  Astrophysical observations (usually explained by dark matter) suggest that
classical mechanics could break down when the acceleration becomes extremely
small (the approach known as modified Newtonian dynamics, or MOND). I present
the first analysis of MOND manifestations in terrestrial (rather than
astrophysical) settings. A new effect is reported: around each equinox date, 2
spots emerge on the Earth where static bodies experience spontaneous
acceleration due to the possible violation of Newton's second law. Preliminary
estimates indicate that an experimental search for this effect can be feasible.


title: Testing DGP modified gravity in the Solar System

abstract:
  In this talk we review the perspectives of testing the multidimensional
Dvali-Gabadadze-Porrati (DGP) model of modified gravity in the Solar System.
The inner planets, contrary to the giant gaseous ones, yield the most promising
scenario for the near future.


title: Hyperboloidal foliations with scri-fixing in spherical symmetry

abstract:
  We study in spherical symmetry the conformal compactification for
hyperboloidal foliations with nonvanishing constant mean curvature. The
conformal factor and the coordinates are chosen such that null infinity is at a
fixed radial coordinate location.


title: Brane cosmology with R_(4) term in the bulk

abstract:
  We consider brane cosmology when the 4D Ricci scalar term is added to the 5D
Einstein-Hilbert action and discuss the role that the addition of this term has
on the brane-bulk system. The induced brane dynamics is shown to be the usual
Einstein dynamics coupled to a modified energy-momentum tensor which is well
defined once the 5D Einstein equations are solved in the bulk. The 5D Einstein
equations valid everywhere in the bulk, but not in the brane, are projected on
the brane. Then making use for the embedding of the brane in the bulk of the
Israel junction conditions, modified by a source term coming from the addition
of the intrinsic curvature scalar in the bulk action, it is possible to obtain
the effective 4D Einstein equations on the brane consistent with the bulk
geometry.


title: Is dark matter futile on the brane?

abstract:
  We investigate whether dark matter can be replaced by various source terms
appearing in the effective Einstein equation, valid on a brane embedded into a
higher dimensional space-time (the bulk). Such non-conventional source terms
include a quadratic (ordinary) matter source term, a geometric source term
originating in the Weyl curvature of the bulk, a source term arising from the
possible asymmetric embedding, and finally the pull-back to the brane of
possible non-standard model bulk fields.


title: Predictions in eternal inflation

abstract:
  In generic models of cosmological inflation, quantum fluctuations strongly
influence the spacetime metric and produce infinitely many regions where the
end of inflation (reheating) is delayed until arbitrarily late times. The
geometry of the resulting spacetime is highly inhomogeneous on scales of many
Hubble sizes. The recently developed string-theoretic picture of the
"landscape" presents a similar structure, where an infinite number of de
Sitter, flat, and anti-de Sitter universes are nucleated via quantum tunneling.
Since observers on the Earth have no information about their location within
the eternally inflating universe, the main question in this context is to
obtain statistical predictions for quantities observed at a random location. I
describe the problems arising within this statistical framework, such as the
need for a volume cutoff and the dependence of cutoff schemes on time slicing
and on the initial conditions. After reviewing different approaches and
mathematical techniques developed in the past two decades for studying these
issues, I discuss the existing proposals for extracting predictions and give
examples of their applications.


title: The structure of non-spacelike curves from a spacetime singularity

abstract:
  We investigate here the causal structure of spacetime in the vicinity of a
spacetime singularity. The particle and energy emission from such ultra-dense
regions forming in gravitational collapse of a massive matter cloud is governed
by the nature of non-spacelike paths near the same. These trajectories are
examined to show that if a null geodesic comes out from the singularity, then
there exist families of future-directed non-spacelike curves which also
necessarily escape from the naked singularity. The existence of such families
is crucial to the physical visibility of the singularity. We do not assume any
underlying symmetries for the spacetime, and earlier considerations on the
nature of causal trajectories emerging from a naked singularity are generalized
and clarified.


title: Backreaction Issues in Relativistic Cosmology and the Dark Energy Debate

abstract:
  The effective evolution of an inhomogeneous universe model in Einstein's
theory of gravitation may be described in terms of spatially averaged scalar
variables. This evolution can be modeled by solutions of a set of Friedmann
equations for an effective scale factor, with matter and backreaction source
terms, where the latter can be represented by a minimally coupled scalar field
(`morphon field'). We review the basic steps of a description of backreaction
effects in relativistic cosmology that lead to refurnishing the standard
cosmological equations, but also lay down a number of unresolved issues in
connection with their interpretation within observational cosmology.


title: Deformed Special Relativity in Position Space

abstract:
  We investigate how deformations of special relativity in momentum space can
be extended to position space in a consistent way, such that the dimensionless
contraction between wave-vector and coordinate-vector remains invariant. By
using a parametrization in terms of an energy dependent speed of light, and an
energy dependent Planck's constant, we are able to formulate simple
requirements that completely determine the active transformations in position
space. These deviate from the standard transformations for large velocities of
the observed object. Some examples are discussed, and it is shown how the
relativistic mass gain of a massive particle is affected. We finally study the
construction of passive Lorentz-transformations.


title: Fundamentals of Quantum Gravity

abstract:
  The outline of a recent approach to quantum gravity is presented. Novel
ingredients include: (1) Affine kinematical variables; (2) Affine coherent
states; (3) Projection operator approach toward quantum constraints; (4)
Continuous-time regularized functional integral representation without/with
constraints; and (5) Hard core picture of nonrenormalizability. The ``diagonal
representation'' for operator representations, introduced by Sudarshan into
quantum optics, arises naturally within this program.


title: Higher Dimensional Rotating Charged Black Holes

abstract:
  We discuss a new analytic solution to the Einstein-Maxwell field equations
that describes electrically charged black holes with a slow rotation and with a
single angular momentum in all higher dimensions. We also compute the
gyromagnetic ratio of these black holes.


title: The Ponzano-Regge model and Reidemeister torsion

abstract:
  The Ponzano-Regge model of three-dimensional quantum gravity is well-defined
when the observables satisfy a certain condition involving the twisted
cohomology. In this case, the partition function is defined in terms of the
Reidemeister torsion. Some consequences for the special cases of planar graphs
and knots are given.


title:
Williams et al. Reply (to the Comment by Dumin on "Progress in Lunar
  Laser Ranging Tests of Relativistic Gravity")

abstract:
  A decreasing gravitational constant, G, coupled with angular momentum
conservation is expected to increrase a planetary semimajor axis, a, as \dot
a/a=-\dot G/G. Analysis of lunar laser ranging data strongly limits such
temporal variations and constrains a local (~1 AU) scale expansion of the solar
system as \dot a/a=-\dot G/G =-(4\pm9)\times10^{-13} yr^{-1}, including that
due to cosmological effects.


title: Paths of Friedmann-Robertson-Walker brane models

abstract:
  Dynamics of brane-world models of dark energy is reviewed. We demonstrate
that simple dark energy brane models can be represented as 2-dimensional
dynamical systems of a Newtonian type. Hence a fictitious particle moving in a
potential well characterizes the model. We investigate the dynamics of the
brane models using methods of dynamical systems. The simple brane-world models
can be successfully unified within a single scheme -- an ensemble of brane dark
energy models. We characterize generic models of this ensemble as well as
exceptional ones using the notion of structural stability (instability). Then
due to the Peixoto theorem we can characterize the class of generic brane
models. We show that global dynamics of the generic brane models of dark energy
is topologically equivalent to the concordance $\Lambda$CDM model. We also
demonstrate that the bouncing models or models in which acceleration of the
universe is only transient phenomenon are non-generic (or exceptional cases) in
the ensemble. We argue that the adequate brane model of dark energy should be a
generic case in the ensemble of FRW dynamical systems on the plane.


title:
A Simplified Mathematical Model for the Formation of Null Singularities
  Inside Black Holes II

abstract:
  We study a simple system of two hyperbolic semi-linear equations, inspired by
the Einstein equations. The system, which was introduced in gr-qc/0612136, is a
model for singularity formation inside black holes. We show for a particular
case of the equations that the system demonstrates a finite time blowup. The
singularity that is formed is a null singularity. Then we show that in this
particular case the singularity has features that are analogous to known
features of models of black-hole interiors - which describe the inner-horizon
instability. Our simple system may provide insight into the formation of null
singularities inside spinning or charged black holes.


title: Quantum Radiation of General Nonstationary Black Holes

abstract:
  This paper has been withdrawn by the authors.
  Quantum radiative characteristics of 4D semi-classical nonstationary black
holes in the general case are investigated by using the method of generalized
tortoise coordinate transformation. It is generally shown that the temperature
and the shape of the event horizon of this kind of black holes depend on both
the time and different angles. Further, we discover that there is a certain
relationship that is ignored before between thermal radiation and non-thermal
radiation of black holes, which is that the chemical potential in thermal
radiation spectrum is equal to the highest energy of the negative energy state
of particles in non-thermal radiation for 4D semi-classical nonstationary black
holes. Also, we show that the deduced general results can be applied to
different concrete conditions.


title:
Quantum Radiation Properties of Dirac Particles in General Nonstationary
  Black Holes

abstract:
  Quantum radiation properties of Dirac particles in general nonstationary
black holes in the general case is investigated by both using the method of
generalized tortoise coordinate transformation and considering the asymptotic
behaviors of both the first and second order forms of Dirac equations near the
event horizon. It is generally shown that the temperature and shape of event
horizon of this kind of black holes depend on both the time and different
angles. Further, we give a general expression of the new extra coupling effect
in thermal radiation spectrum of Dirac particles which is missing in that of
scalar particles. Also, we reveal a relationship that is ignored before between
thermal radiation and non-thermal radiation in the case of scalar particles,
which is that the chemical potential in thermal radiation spectrum is equal to
the highest energy of the negative energy state of scalar particles in
non-thermal radiation for general nonstationary black holes.


title: Natural Coordinate System in Curved Space-time

abstract:
  In this paper we establish a generally and globally valid coordinate system
in curved space-time with the simultaneous hypersurface orthogonal to the time
coordinate. The time coordinate can be preseted according to practical evolving
process and keep synchronous with the evolution of the realistic world. In this
coordinate system, it is convenient to express the physical laws and to
calculate physical variables with clear geometrical meaning. We call it
"natural coordinate system". The constructing method for the natural coordinate
system is concretely provided, and its physical and geometrical meanings are
discussed in detail. In NCS we make classical approximation of spinor equation
to get Newtonian mechanics, and then make weak field approximation of
Einstein's equation and low speed approximation of particles moving in the
space-time. From the analysis and examples we find it is a nice coordinate
system to describe the realistic curved space-time, and is helpful to
understand the nature of space-time.


title: Impossibility of Unlimited Gravitational Collapse

abstract:
  It is shown that the gravitational field, as a physical field developing in
the Minkowsky space, does not lead to unlimited gravitational collapse of
massive bodies and, hence, excludes a possibility of the formation of the
``black holes''.


title: On quantum effects in the vicinity of would-be horizons

abstract:
  We present a method based on the so-called Quantum Energy Inequalities, which
allows to compare, and bound, the expectation values of energy-densities of
ground states of quantum fields in spacetimes possessing isometric regions. The
method supports the conclusion, that the Boulware energy density is universal
both: at modest (and far) distances from compact spherical objects, and close
to the would-be horizons of the gravastar/QBHO spacetimes. It also provides a
natural consistency check for concrete (approximate, numerical) calculations of
the expectation values of the energy-momentum tensors.


title: Self-Dual Fields on the space of a Kerr-Taub-bolt Instanton

abstract:
  We discuss a new exact solution for self-dual Abelian gauge fields living on
the space of the Kerr-Taub-bolt instanton, which is a generalized example of
asymptotically flat instantons with non-self-dual curvature.


title: Conditions for the cosmological viability of f(R) dark energy models

abstract:
  We derive the conditions under which dark energy models whose Lagrangian
densities f are written in terms of the Ricci scalar R are cosmologically
viable. We show that the cosmological behavior of f(R) models can be understood
by a geometrical approach consisting in studying the m(r) curve on the (r, m)
plane, where m=Rf_{,RR}/f_{,R} and r=-Rf_{,R}/f with f_{,R}=df/dR. This allows
us to classify the f(R) models into four general classes, depending on the
existence of a standard matter epoch and on the final accelerated stage. The
existence of a viable matter dominated epoch prior to a late-time acceleration
requires that the variable m satisfies the conditions m(r) approx+0 and
dm/dr>-1 at r approx-1. For the existence of a viable late-time acceleration we
require instead either (i) m=-r-1, (sqrt{3}-1)/2<m<1 and dm/dr<-1 or (ii) 0<m<1
at r=-2. These conditions identify two regions in the (r, m) space, one for the
matter era and the other for the acceleration. Only models with a m(r) curve
that connects these regions and satisfy the requirements above lead to an
acceptable cosmology. The models of the type f(R)=alpha R^{-n} and f=R+alpha
R^{-n} do not satisfy these conditions for any n>0 and n<-1 and are thus
cosmologically unacceptable. Similar conclusions can be reached for many other
examples discussed in the text. In most cases the standard matter era is
replaced by a cosmic expansion with scale factor a propto t^{1/2}. We also find
that f(R) models can have a strongly phantom attractor but in this case there
is no acceptable matter era.


title: Constraint Relaxation

abstract:
  Full relativistic simulations in three dimensions are known to develop
runaway modes that grow exponentially and are accompanied by violations of the
Hamiltonian and momentum constraints. We present here a method that controls
the violation of these constraints and is tested with simulations of binary
neutron stars in circular orbits. We show that this technique improves the
overall quality of the simulations.


title: On the causal properties of warped product spacetimes

abstract:
  It is shown that the warped product spacetime P=M *_f H, where H is a
complete Riemannian manifold, and the original spacetime M share necessarily
the same causality properties, the only exceptions being the properties of
causal continuity and causal simplicity which present some subtleties. For
instance, it is shown that if diamH=+\infty, the direct product spacetime P=M*H
is causally simple if and only if (M,g) is causally simple, the Lorentzian
distance on M is continuous and any two causally related events at finite
distance are connected by a maximizing geodesic. Similar conditions are found
for the causal continuity property. Some new results concerning the behavior of
the Lorentzian distance on distinguishing, causally continuous, and causally
simple spacetimes are obtained. Finally, a formula which gives the Lorentzian
distance on the direct product in terms of the distances on the two factors
(M,g) and (H,h) is obtained.


title: Shedding Some New Lights upon the Stellar Quasi-Normal Modes

abstract:
  In the current paper we present some new data on the issue of quasi-normal
modes (QNMs) of uniform, neutron and quark stars. These questions have already
been addressed in the literature before, but we have found some interesting
features that have not been discussed so far. We have increased the range of
frequency values for the scalar and axial perturbations of such stars and made
a comparison between such QNMs and those of the very well-known Schwarzschild
black holes. Also addressed in this work was the interesting feature of
competing modes, which appear not only for uniform stars, but for quark stars
as well.


title: General relativistic accretion with backreaction

abstract:
  The spherically symmetric steady accretion of polytropic perfect fluids onto
a black hole is the simplest flow model that can demonstrate the effects of
backreaction. Backreaction keeps intact most of the characteristics of the
sonic point. For any such system the mass accretion rate achieves maximal value
when the mass of the fluid is 1/3 of the total mass. Fixing the total mass of
the system, one observes the existence of two weakly accreting regimes, one
overabundant and the other poor in fluid content.


title: Bianchi Type V Universes with Bulk Viscosity in General Relativity

abstract:
  Bianchi type V bulk viscous fluid cosmological models are investigated. Using
a generation technique (Camci {\it et al.}, 2001), it is shown that the
Einstein's field equations are solvable for any arbitrary cosmic scale
function. The viscosity coefficient of bulk viscous fluid is assumed to be a
power function of mass density. Solutions for particular forms of cosmic scale
functions are also obtained. Some physical and geometric aspects of the models
are also discussed.


title: Aligned Electromagnetic Excitations of the Kerr-Schild Solutions

abstract:
  Aligned to the Kerr-Schild geometry electromagnetic excitations are
investigated, and asymptotically exact solutions are obtained for the
low-frequency limit.


title: Kerr's Gravity as a Quantum Gravity on the Compton Level

abstract:
  The Dirac theory of electron and QED neglect gravitational field, while the
corresponding to electron Kerr-Newman gravitational field has very strong
influence on the Compton distances. It polarizes space-time, deforms the
Coulomb field and changes topology. We argue that the Kerr geometry may be
hidden beyond the Quantum Theory, representing a complimentary space-time
description.


title:
The Kerr Theorem, Multisheeted Twistor Spaces and Multiparticle
  Kerr-Schild Solutions

abstract:
  Kerr-Schild formalism is generalized by incorporation of the Kerr Theorem
with polynomials of higher degrees in $Y\in CP^1.$ It leads to multisheeted
twistor spaces and multiparticle solutions.


title: Celestial mechanics of elastic bodies

abstract:
  We construct time independent configurations of two gravitating elastic
bodies. These configurations either correspond to the two bodies moving in a
circular orbit around their center of mass or strictly static configurations.


title:
Flat, radiation universes with quadratic corrections and asymptotic
  analysis

abstract:
  It was shown long ago by T. V. Ruzmaikina and A. A. Ruzmaikin that within the
framework of a homogeneous and isotropic cosmological model quadratic
corrections of the gravitational field cannot provide solutions that are both
regular initially and go over to Friedmann type at later times. We find here,
by applying a dynamical systems approach, the general form of the solution to
this class of models in the neighborhood of the initial singularity under the
above conditions.


title: Gradient expansion approach to nonlinear superhorizon perturbations

abstract:
  Using the gradient expansion approach, we formulate a nonlinear cosmological
perturbation theory on super-horizon scales valid to $O(\epsilon^2)$, where
$\epsilon$ is the expansion parameter associated with a spatial derivative. For
simplicity, we focus on the case of a single perfect fluid, but we take into
account not only scalar but also vector and tensor modes. We derive the general
solution under the uniform-Hubble time-slicing. In doing so, we identify the
scalar, vector and tensor degrees of freedom contained in the solution. We then
consider the coordinate transformation to the synchronous gauge in order to
compare our result with the previous result given in the literature. In
particular, we find that the tensor mode is invariant to $O(\epsilon^2)$ under
the coordinate transformation.


title: Fermat's principle in quantum gravitational optics

abstract:
  Interactions incorporating the vacuum polarization effects in curved
backgrounds modify the null cone structure in such a way that the photon
trajectories would not be the space-time geodesics anymore. The gravitational
birefringence introduced as a direct consequence of these effects, will allow
shifts in the photon velocities leading to polarization dependent superluminal
propagation. Taking these effects into account we study Fermat's principle in
the context of the 1+3 (threading) formulation of the space-time decomposition.
We find an expression for the modified spacetime refractive index and show it
is proportional to the light cone correction to the first order. Consequences
of this modification on polarization sum rules and spatial light paths are
considered.


title:
Gravitation, electromagnetism and the cosmological constant in purely
  affine gravity

abstract:
  The Eddington Lagrangian in the purely affine formulation of general
relativity generates the Einstein equations with the cosmological constant. The
Ferraris-Kijowski purely affine Lagrangian for the electromagnetic field, which
has the form of the Maxwell Lagrangian with the metric tensor replaced by the
symmetrized Ricci tensor, is dynamically equivalent to the Einstein-Maxwell
Lagrangian in the metric formulation. We show that the sum of the two affine
Lagrangians is dynamically inequivalent to the sum of the analogous Lagrangians
in the metric-affine/metric formulation. We also show that such a construction
is valid only for weak electromagnetic fields. Therefore the purely affine
formulation that combines gravitation, electromagnetism and the cosmological
constant cannot be a simple sum of terms corresponding to separate fields.
Consequently, this formulation of electromagnetism seems to be unphysical,
unlike the purely metric and metric-affine pictures, unless the electromagnetic
field couples to the cosmological constant.


title: Spectral Broadening of Radiation from Relativistic Collapsing Objects

abstract:
  We study light curves and the spectral broadening of the radiation emitted
during the finite interval of time by a surface of a collapsing object. We
study a simplified model of monochromatic radiations from a spherical surface
which is assumed to be falling freely. We discuss the possible way how to infer
the physical parameters, such as the mass and radii of emission, from the light
curves and spectral broadenings.


title:
Einstein's equations as a thermodynamic identity: The cases of
  stationary axisymmetric horizons and evolving spherically symmetric horizons

abstract:
  There is an intriguing analogy between the gravitational dynamics of the
horizons and thermodynamics. In case of general relativity, as well as for a
wider class of Lanczos-Lovelock theories of gravity, it is possible to
interpret the field equations near any spherically symmetric horizon as a
thermodynamic identity TdS = dE + PdV. We study this approach further and
generalize the results to two more generic cases within the context of general
relativity: (i) stationary axis-symmetric horizons and (ii) time dependent
evolving horizons. In both the cases, the near horizon structure of Einstein
equations can be expressed as a thermodynamic identity under the virtual
displacement of the horizon. This result demonstrates the fact that the
thermodynamic interpretation of gravitational dynamics is not restricted to
spherically symmetric or static horizons but is quite generic in nature and
indicates a deeper connection between gravity and thermodynamics.


title: Entropy of Null Surfaces and Dynamics of Spacetime

abstract:
  The null surfaces of a spacetime act as one-way membranes and can block
information for a corresponding family of observers (time-like curves). Since
lack of information can be related to entropy, this suggests the possibility of
assigning an entropy to the null surfaces of a spacetime. We motivate and
introduce such an entropy functional for any vector field in terms of a
fourth-rank divergence free tensor P_{ab}^{cd} with the symmetries of the
curvature tensor. Extremising this entropy for all the null surfaces then leads
to equations for the background metric of the spacetime. When P_{ab}^{cd} is
constructed from the metric alone, these equations are identical to Einstein's
equations with an undetermined cosmological constant (which arises as an
integration constant). More generally, if P_{ab}^{cd} is allowed to depend on
both metric and curvature in a polynomial form, one recovers the
Lanczos-Lovelock gravity. In all these cases: (a) We only need to extremise the
entropy associated with the null surfaces; the metric is not a dynamical
variable in this approach. (b) The extremal value of the entropy agrees with
standard results, when evaluated on-shell for a solution admitting a horizon.
The role of full quantum theory of gravity will be to provide the specific form
of P_{ab}^{cd} which should be used in the entropy functional. With such an
interpretation, it seems reasonable to interpret the Lanczos-Lovelock type
terms as quantum corrections to classical gravity.


title: Radiation reaction in curved space-time: local method

abstract:
  Although consensus seems to exist about the validity of equations accounting
for radiation reaction in curved space-time, their previous derivations were
criticized recently as not fully satisfactory: some ambiguities were noticed in
the procedure of integration of the field momentum over the tube surrounding
the world-line. To avoid these problems we suggest a purely local derivation
dealing with the field quantities defined only {\em on the world-line}. We
consider point particle interacting with scalar, vector (electromagnetic) and
linearized gravitational fields in the (generally non-vacuum) curved
space-time. To properly renormalize the self-action in the gravitational case,
we use a manifestly reparameterization-invariant formulation of the theory.
Scalar and vector divergences are shown to cancel for a certain ratio of the
corresponding charges. We also report on a modest progress in extending the
results for the gravitational radiation reaction to the case of non-vacuum
background.


title: Irreducible Killing Tensors from Third Rank Killing-Yano Tensors

abstract:
  We investigate higher rank Killing-Yano tensors showing that third rank
Killing-Yano tensors are not always trivial objects being possible to construct
irreducible Killing tensors from them. We give as an example the Kimura IIC
metric were from two rank Killing-Yano tensors we obtain a reducible Killing
tensor and from third rank Killing-Yano tensors we obtain three Killing
tensors, one reducible and two irreducible.


title: Quantum gravity and spacetime symmetries

abstract:
  Small violations of spacetime symmetries have recently been identified as
promising Planck-scale signals. This talk reviews how such violations can arise
in various approaches to quantum gravity, how the emergent low-energy effects
can be described within the framework of relativistic effective field theories,
how suitable tests can be identified, and what sensitivities can be expected in
current and near-future experiments.


title:
Perturbative stability and absorption cross section in string corrected
  black holes

abstract:
  We consider a d-dimensional spherically symmetric dilatonic R^2 string
corrected black hole solution. We study its stability under tensor type
gravitational perturbations and compute the absorption cross section for low
frequency gravitational waves.


title:
Detection of gravitational waves in Michelson interferometer by the use
  of second order correlation functions

abstract:
  The possibility of measuring the second order correlation function of the
gravitational waves detectors' currents or photonumbers, and the observation of
the gravitational signals by using a spectrum analyzer is discussed. The method
is based on complicated data processing and is expected to be efficient for
coherent periodic gravitational waves. It is suggested as an alternative method
to the conventional one which is used now in the gravitational waves
observatories.


title: Cosmological dynamics of Scalar--Tensor Gravity

abstract:
  We study the phase--space of FLRW models derived from Scalar--Tensor Gravity
where the non--minimal coupling is $F(\phi)=\xi\phi^2$ and the effective
potential is $V(\phi)=\lambda \phi^n$. Our analysis allows to unfold many
feature of the cosmology of this class of theories. For example, the evolution
mechanism towards states indistinguishable from GR is recovered and proved to
depend critically on the form of the potential $V(\phi)$. Also, transient
almost--Friedmann phases evolving towards accelerated expansion and unstable
inflationary phases evolving towards stable ones are found. Some of our results
are shown to hold also for the String-Dilaton action.


title: Explain cosmic acceleration? First, correct Einstein

abstract:
  In creating his gravitational field equations Einstein unjustifiedly assumed
that inertial mass, and its energy equivalent, is a source of gravity. Denying
this assumption allows modifying the field equations to a form in which a
positive cosmological constant appears as a uniform density of gravitationally
repulsive matter. This repulsive matter is identified as the back sides of the
'drainholes' (called by some 'traversable wormholes') introduced by the author
in 1973, which attract on the high, front sides and repel more strongly on the
low, back sides. The field equations with a scalar field added produce
cosmological models that 'bounce' off a positive minimum of the scale factor
and accelerate throughout history. The 'dark drainholes' that radiate nothing
visible are hypothesized to constitute the 'dark matter' inferred from
observation, their excess of negative active mass over positive active mass
driving the accelerating expansion. For a universe with spatial curvature zero,
and the ratio of scale factor now to scale factor at bounce equal to the Hubble
radius over the Planck length, the model gives an elapsed time since the bounce
of two trillion years. The solutions for negative spatial curvature exhibit
early stage inflation of great magnitude in short times. Cosmic voids,
filaments, and walls are attributed to separation of the back sides of the
drainholes from the front, driven by their mutual attractive-repulsive
interactions.


title:
Spacetime geometric structures and the Search for a Quantum Theory of
  Gravity

abstract:
  One of the biggest challenges to theoretical physics of our time is to find a
background-independent quantum theory of gravity.
  Today one encounters a profusion of different attempts at quantization, but
no fully accepted - or acceptable, theory of quantum gravity. Any such approach
requires a response to a question that lies at the heart of this problem. ``How
shall we resolve the tension between the background dependence of all
hitherto-successful quantum theories, both non-relativistic quantum mechanics
and special-relativistic quantum field theory, and the background independence
of classical general relativity?''
  The need for a background-independent quantization procedure forms the
starting point of my approach. In this paper I shall present a gauge-natural
formulation of general relativity, and provide some insights into the structure
of the space of geometries, which plays an important role in the construction
of a non-perturbative quantum gravity using a path integral approach, as well
as in string theory.


title:
Cosmology without Einstein's assumption that inertial mass produces
  gravity

abstract:
  Giving up Einstein's assumption, implicit in his 1916 field equations, that
inertial mass, even in its appearance as energy, is equivalent to active
gravitational mass and therefore is a source of gravity allows revising the
field equations to a form in which a positive cosmological constant is seen to
(mis)represent a uniform negative net mass density of gravitationally
attractive and gravitationally repulsive matter. Field equations with both
positive and negative active gravitational mass densities of both primordial
and continuously created matter incorporated, along with two scalar fields to
`relax the constraints' on the space-time geometry, yield cosmological
solutions that exhibit inflation, deceleration, coasting, acceleration, and a
`big bounce' instead of a `big bang', and provide good fits to a Hubble diagram
of type Ia supernovae data. The repulsive matter is identified as the back
sides of the `drainholes' introduced by the author in 1973 as solutions of
those same field equations. Drainholes (prototypical examples of `traversable
wormholes') are topological tunnels in space which gravitationally attract on
their front, entrance sides and repel more strongly on their back, exit sides.
The front sides serve both as the gravitating cores of the visible, baryonic
particles of primordial matter and as the continuously created, invisible
particles of the `dark matter' needed to hold together the large scale
structures seen in the universe; the back sides serve as the misnamed `dark
energy' driving the current acceleration of the expansion of the universe.
Formation of cosmic voids, walls, filaments, and nodes is attributed to
expulsion of drainhole entrances from regions populated by drainhole exits, and
accumulation of the entrances on boundaries separating those regions.


title: Varying Speed of Light, Modified Chaplygin Gas and Accelerating Universe

abstract:
  In this paper, we have considered a model of modified Chaplygin gas in VSL
theory with variable gravitational constant $G$. We have shown that the
evolution of the universe starts from radiation era to phantom model. The whole
evolution of the universe has been shown diagramatically by using statefinder
parameters.


title: Generalized Hawking-Page Phase Transition

abstract:
  The issue of radiant spherical black holes being in stable thermal
equilibrium with their radiation bath is reconsidered. Using a simple
equilibrium statistical mechanical analysis incorporating Gaussian thermal
fluctuations in a canonical ensemble of isolated horizons, the heat capacity is
shown to diverge at a critical value of the classical mass of the isolated
horizon, given (in Planckian units) by the {\it microcanonical} entropy
calculated using Loop Quantum Gravity. The analysis reproduces the Hawking-Page
phase transition discerned for anti-de Sitter black holes and generalizes it in
the sense that nowhere is any classical metric made use of.


title: The Bazanski Approach in Brane Worlds: A Brief Introduction

abstract:
  Paths of test particles, rotating and charged objects in brane-worlds using a
modified Bazanski Lagrangian are derived. We also discuss the transition to
their corresponding equations in four dimensions. We then make a comparison
between the given equations in brane-worlds (BW) and their analog in
space-time-matter (STM) theory.


title: Comparisons of binary black hole merger waveforms

abstract:
  This a particularly exciting time for gravitational wave physics.
Ground-based gravitational wave detectors are now operating at a sensitivity
such that gravitational radiation may soon be directly detected, and recently
several groups have independently made significant breakthroughs that have
finally enabled numerical relativists to solve the Einstein field equations for
coalescing black-hole binaries, a key source of gravitational radiation. The
numerical relativity community is now in the position to begin providing
simulated merger waveforms for use by the data analysis community, and it is
therefore very important that we provide ways to validate the results produced
by various numerical approaches. Here, we present a simple comparison of the
waveforms produced by two very different, but equally successful
approaches--the generalized harmonic gauge and the moving puncture methods. We
compare waveforms of equal-mass black hole mergers with minimal or vanishing
spins. The results show exceptional agreement for the final burst of radiation,
with some differences attributable to small spins on the black holes in one
case.


title:
Harmonic polynomials for expanding the fluctuations of the Cosmic
  Microwave Background: The Poincare and the 3-sphere model

abstract:
  Fluctuations of the Cosmic Microwave Background CMB are observed by the WMAP.
When expanded into the harmonic eigenmodes of the space part of a cosmological
model, they provide insight into the large-scale topology of space. All
harmonic polynomials on the multiply connected dodecahedral Poincare space are
constructed. Strong and specific selection rules are given by comparing the
polynomials to those on the 3-sphere, its simply connected cover.


title: A Rigorous Treatment of Energy Extraction from a Rotating Black Hole

abstract:
  The Cauchy problem is considered for the scalar wave equation in the Kerr
geometry. We prove that by choosing a suitable wave packet as initial data, one
can extract energy from the black hole, thereby putting supperradiance, the
wave analogue of the Penrose process, into a rigorous mathematical framework.
We quantify the maximal energy gain. We also compute the infinitesimal change
of mass and angular momentum of the black hole, in agreement with
Christodoulou's result for the Penrose process. The main mathematical tool is
our previously derived integral representation of the wave propagator.


title: Self sustained traversable wormholes and the equation of state

abstract:
  We compute the graviton one loop contribution to a classical energy in a
\textit{traversable} wormhole background. The form of the shape function
considered is obtained by the equation of state $p=\omega\rho$. We investigate
the size of the wormhole as a function of the parameter $\omega$. The
investigation 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 \textit{self-consistent} source for the
traversable wormhole.The case of the phantom region is briefly discussed.


title: Self sustained phantom wormholes in semi-classical gravity

abstract:
  A possible candidate for the late time accelerated expanding Universe is
phantom energy, which possesses rather bizarre properties, such as the
prediction of a Big Rip singularity and the violation of the null energy
condition. The latter is a fundamental ingredient of traversable wormholes, and
it has been shown that phantom energy may indeed sustain these exotic
geometries. Inspired by the evolving dark energy parameter crossing the phantom
divide, we consider in this work a varying equation of state parameter
dependent on the radial coordinate, i.e., $\omega(r)=p(r)/\rho(r)$. We shall
impose that phantom energy is concentrated in the neighborhood of the throat,
to ensure the flaring out condition, and several models are analyzed. We shall
also consider the possibility that these phantom wormholes be sustained by
their own quantum fluctuations. The energy density of the graviton one loop
contribution to a classical energy in a phantom wormhole background and the
finite one loop energy density are considered as a self-consistent source for
these wormhole geometries. The latter semi-classical approach prohibits
solutions with a constant equation of state parameter, which further motivates
the imposition of a radial dependent parameter, $\omega(r)$, and only permits
solutions with a steep positive slope proportional to the radial derivative of
the equation of state parameter, evaluated at the throat. The size of the
wormhole throat as a function of the relevant parameters is also explored.


title: Cosmology in the Solar System: Pioneer effect is not cosmological

abstract:
  Does the Solar System and, more generally, a gravitationally bound system
follow the cosmic expansion law ? Is there a cosmological influence on the
dynamics or optics in such systems ? The general relativity theory provides an
unique and unambiguous answer, as a solution of Einstein equations with a local
source in addition to the cosmic fluid, and obeying the correct (cosmological)
limiting conditions. This solution has no analytic expression. A Taylor
development of its metric allows a complete treatment of dynamics and optics in
gravitationally bound systems, up to the size of galaxy clusters, taking into
account both local and cosmological effects. In the solar System, this provides
an estimation of the (non zero) cosmological influence on the Pioneer probe: it
fails to account for the " Pioneer effect " by about 10 orders of magnitude. We
criticize contradictory claims on this topic.


title:
Orbital evolution for extreme mass-ratio binaries: conservative self
  forces

abstract:
  The conservative dephasing effects of gravitational self forces for extreme
mass-ratio inspirals are studied. Both secular and non-secular conservative
effects may have a significant effect on LISA waveforms that is independent of
the mass ratio of the system. Such effects need to be included in generated
waveforms to allow for accurate gravitational wave astronomy that requires
integration times as long as a year.


title:
Spontaneous excitation of an accelerated multilevel atom in dipole
  coupling to the derivative of a scalar field

abstract:
  We study the spontaneous excitation of an accelerated multilevel atom in
dipole coupling to the derivative of a massless quantum scalar field and
separately calculate the contributions of the vacuum fluctuation and radiation
reaction to the rate of change of the mean atomic energy of the atom. It is
found that, in contrast to the case where a monopole like interaction between
the atom and the field is assumed, there appear extra corrections proportional
to the acceleration squared, in addition to corrections which can be viewed as
a result of an ambient thermal bath at the Unruh temperature, as compared with
the inertial case, and the acceleration induced correction terms show
anisotropy with the contribution from longitudinal polarization being four
times that from the transverse polarization for isotropically polarized
accelerated atoms. Our results suggest that the effect of acceleration on the
rate of change of the mean atomic energy is dependent not only on the quantum
field to which the atom is coupled, but also on the type of the interaction
even if the same quantum scalar field is considered.


title:
Formation of closed timelike curves in a composite vacuum/dust
  asymptotically-flat spacetime

abstract:
  We present a new asymptotically-flat time-machine model made solely of vacuum
and dust. The spacetime evolves from a regular spacelike initial hypersurface S
and subsequently develops closed timelike curves. The initial hypersurface S is
asymptotically flat and topologically trivial. The chronology violation occurs
in a compact manner; namely the first closed causal curves form at the boundary
of the future domain of dependence of a compact region in S (the core). This
central core is empty, and so is the external asymptotically flat region. The
intermediate region surrounding the core (the envelope) is made of dust with
positive energy density. This model trivially satisfies the weak, dominant, and
strong energy conditions. Furthermore it is governed by a well-defined system
of field equations which possesses a well-posed initial-value problem.


title:
An Exact Cosmological Solution of the Coupled Einstein-Majorana
  Fermion-Scalar Field Equations

abstract:
  We couple a neutral scalar field and a Majorana fermion field to Einstein
gravity represented by the Robertson-Walker metric and find a class of exact
cosmological solutions.


title:
A comparison of methods for gravitational wave burst searches from LIGO
  and Virgo

abstract:
  The search procedure for burst gravitational waves has been studied using 24
hours of simulated data in a network of three interferometers (Hanford 4-km,
Livingston 4-km and Virgo 3-km are the example interferometers). Several
methods to detect burst events developed in the LIGO Scientific Collaboration
(LSC) and Virgo collaboration have been studied and compared. We have performed
coincidence analysis of the triggers obtained in the different interferometers
with and without simulated signals added to the data. The benefits of having
multiple interferometers of similar sensitivity are demonstrated by comparing
the detection performance of the joint coincidence analysis with LSC and Virgo
only burst searches. Adding Virgo to the LIGO detector network can increase by
50% the detection efficiency for this search. Another advantage of a joint
LIGO-Virgo network is the ability to reconstruct the source sky position. The
reconstruction accuracy depends on the timing measurement accuracy of the
events in each interferometer, and is displayed in this paper with a fixed
source position example.


title:
Detailed comparison of LIGO and Virgo Inspiral Pipelines in Preparation
  for a Joint Search

abstract:
  Presented in this paper is a detailed and direct comparison of the LIGO and
Virgo binary neutron star detection pipelines. In order to test the search
programs, numerous inspiral signals were added to 24 hours of simulated
detector data. The efficiencies of the different pipelines were tested, and
found to be comparable. Parameter estimation routines were also tested. We
demonstrate that there are definite benefits to be had if LIGO and Virgo
conduct a joint coincident analysis; these advantages include increased
detection efficiency and the providing of source sky location information.


title:
Optical reference geometry and inertial forces in Kerr-de Sitter
  spacetimes

abstract:
  Optical reference geometry and related concept of inertial forces are
investigated in Kerr-de Sitter spacetimes. Properties of the inertial forces
are summarized and their typical behaviour is illustrated. The intuitive
'Newtonian' application of the forces in the relativistic dynamics is
demonstrated in the case of the test particle circular motion, static
equilibrium positions and perfect fluid toroidal configurations. Features of
the optical geometry are illustrated by the embedding diagrams of its
equatorial plane. The embedding diagrams do not cover whole the stationary
regions of the spacetimes, therefore the limits of embeddability are
established. A shape of the embedding diagrams is related to the behaviour of
the centrifugal force and it is characterized by the number of turning points
of the diagrams. Discussion of the number of embeddable photon circular orbits
is also included and the typical embedding diagrams are constructed. The
Kerr-de Sitter spacetimes are classified according to the properties of the
inertial forces and embedding diagrams.


title: Dark energy as a massive vector field

abstract:
  We propose that the Universe is filled with a massive vector field,
non-minimally coupled to gravitation. The field equations of the model are
consistently derived and their application to cosmology is considered. The
Friedmann equations acquire an extra dark-energy component, which is
proportional to the mass of the vector particle. This leads to a late-time
accelerated de Sitter type expansion. The free parameters of the model
(gravitational coupling constants and initial value of the cosmological vector
field) can be estimated by using the PPN solar system constraints. The mass of
the cosmological massive vector particle, which may represent the main
component of the Universe, is of the order of 10^-63 g.


title:
Black hole evaporation in a heat bath as a nonequilibrium process and
  its final fate

abstract:
  When a black hole evaporates, there arises a net energy flow from black hole
into its outside environment (heat bath). The existence of energy flow means
that the thermodynamic state of the whole system, which consists of the black
hole and the heat bath, is in a nonequilibrium state. Therefore, in order to
study the detail of evaporation process, the nonequilibrium effects of the
energy flow should be taken into account. Using the nonequilibrium
thermodynamics which has been formulated recently, this paper shows the
following: (1) Time scale of black hole evaporation in a heat bath becomes
shorter than that of the evaporation in an empty space (a situation without
heat bath), because a nonequilibrium effect of temperature difference between
the black hole and heat bath appears as a strong energy extraction from the
black hole by the heat bath. (2) Consequently a huge energy burst (stronger
than that of the evaporation in an empty space) arises at the end of
semi-classical stage of evaporation. (3) It is suggested that a remnant of
Planck size remains after the quantum stage of evaporation in order to
guarantee the increase of total entropy of the whole system.


title:
Higher-Dimensional Bulk Wormholes and their Manifestations in Brane
  Worlds

abstract:
  There is nothing to prevent a higher-dimensional anti-de Sitter bulk
spacetime from containing various other branes in addition to hosting our
universe, presumed to be a positive-tension 3-brane. In particular, it could
contain closed, microscopic branes that form the boundary surfaces of void
bubbles and thus violate the null energy condition in the bulk. The possible
existence of such micro branes can be investigated by considering the
properties of the ground state of a pseudo-Wheeler-DeWitt equation describing
brane quantum dynamics in minisuperspace. If they exist, a concentration of
these micro branes could act as a fluid of exotic matter able to support
macroscopic wormholes connecting otherwise distant regions of the bulk. Were
the brane constituting our universe to expand into a region of the bulk
containing such higher-dimensional macroscopic wormholes, they would likely
manifest themselves in our brane as wormholes of normal dimensionality, whose
spontaneous appearance and general dynamics would seem inexplicably peculiar.
This encounter could also result in the formation of baby universes of a
particular type.


title: Wormholes with varying equation of state parameter

abstract:
  We propose wormholes solutions by assuming space dependent equation of state
parameter. Our models show that the existence of wormholes is supported by
arbitrary small quantities of averaged null energy condition (ANEC) violating
phantom energy characterized by variable equation state parameter.


title: Braneworld cosmological singularities

abstract:
  The purpose of this brief report is to present some results of our on-going
project on the asymptotic behaviour of braneworld-type solutions on approach to
their possible finite `time' singularities.