title: Resonant Spheres: Multifrequency Detectors of Gravitational Waves

abstract:
  We discuss the capabilities of spherical antenn\ae as single multifrequency
detectors of gravitational waves. A first order theory allows us to evaluate
the coupled spectrum and the resonators readouts when the first and the second
quadrupole bare sphere frequencies are simultaneously selected for layout
tuning. We stress the existence of non-tuning influences in the second mode
coupling causing draggs in the frequency splittings. These URF effects are
relevant to a correct physical description of resonant spheres, still more if
operating as multifrequency appliances like our PHCA proposal.


title: Accelerated Expansion as Predicted by an Ether Theory of Gravitation

abstract:
  Cosmology is investigated within a new, scalar theory of gravitation, which
is a preferred-frame bimetric theory with flat background metric. Before coming
to cosmology, the motivation for an " ether theory " is exposed at length; the
investigated concept of ether is presented: it is a compressible fluid, and
gravity is seen as Archimedes' thrust due to the pressure gradient in that
fluid. The construction of the theory is explained and the current status of
the experimental confrontation is analysed, both in some detail. An analytical
cosmological solution is obtained for a general form of the energy-momentum
tensor. According to that theory, expansion is necessarily accelerated, both by
vacuum and even by matter. In one case, the theory predicts expansion, the
density increasing without limit as time goes back to infinity. High density is
thus obtained in the past, without a big-bang singularity. In the other case,
the Universe follows a sequence of (non-identical) contraction-expansion
cycles, each with finite maximum energy density; the current expansion phase
will end by infinite dilution in some six billions of years. The density ratio
of the present cycle (ratio of the maximum to current densities) is not
determined by the current density and the current Hubble constant H0, unless a
special assumption is made. Since cosmological redshifts approaching z = 4 are
observed, the density ratio should be at least 100. From this and the estimate
of H0, the time spent since the maximum density is constrained to be larger
than several hundreds of billions of years. Yet if a high density ratio,
compatible with the standard explanation for the light elements and the 2.7 K
radiation, is assumed, then the age of the Universe is much larger still.


title:
Simulation of merging binary neutron stars in full general relativity:
  $\Gamma=2$ case

abstract:
  We have performed 3D numerical simulations for merger of equal mass binary
neutron stars in full general relativity. We adopt a $\Gamma$-law equation of
state in the form $P=(\Gamma-1)\rho\epsilon$ where P, $\rho$, $\varep$ and
$\Gamma$ are the pressure, rest mass density, specific internal energy, and the
adiabatic constant with $\Gamma=2$. As initial conditions, we adopt models of
corotational and irrotational binary neutron stars in a quasi-equilibrium state
which are obtained using the conformal flatness approximation for the three
geometry as well as an assumption that a helicoidal Killing vector exists. In
this paper, we pay particular attention to the final product of the
coalescence. We find that the final product depends sensitively on the initial
compactness parameter of the neutron stars : In a merger between sufficiently
compact neutron stars, a black hole is formed in a dynamical timescale. As the
compactness is decreased, the formation timescale becomes longer and longer. It
is also found that a differentially rotating massive neutron star is formed
instead of a black hole for less compact binary cases, in which the rest mass
of each star is less than 70-80% of the maximum allowed mass of a spherical
star. In the case of black hole formation, we roughly evaluate the mass of the
disk around the black hole. For the merger of corotational binaries, a disk of
mass $\sim 0.05-0.1M_*$ may be formed, where M_* is the total rest mass of the
system. On the other hand, for the merger of irrotational binaries, the disk
mass appears to be very small : < 0.01M_*.


title:
Locally Weyl invariant massless bosonic and fermionic spin-1/2 action in
  the $\bf (W_{n(4)},g)$ and $\bf (U_{4},g)$ space-times

abstract:
  We search for a real bosonic and fermionic action in four dimensions which
both remain invariant under local Weyl transformations in the presence of
non-metricity and contortion tensor. In the presence of the non-metricity
tensor the investigation is extended to Weyl $(W_n, g)$ space-time while when
the torsion is encountered we are restricted to the Riemann-Cartan $(U_4, g)$
space-time. Our results hold for a subgroup of the Weyl-Cartan $(Y_4, g)$
space-time and we also calculate extra contributions to the conformal gravity.


title: Quantum mechanical time contradicts the uncertainty principle

abstract:
  The a priori time in conventional quantum mechanics is shown to contradict
the uncertainty principle. A possible solution is given.


title:
Quantum reflection of massless neutrinos from a torsion-induced
  potential

abstract:
  In the context of the Einstein-Cartan-Dirac model, where the torsion of the
space-time couples to the axial currents of the fermions, we study the effects
of this quantum-gravitational interaction on a massless neutrino beam crossing
through a medium with high number density of fermions at rest. We calculate the
reflection amplitude and show that a specific fraction of the incident
neutrinos reflects from this potential if the polarization of the medium is
different from zero. We also discuss the order of magnitude of the fermionic
number density in which this phenomenon is observable, in other theoretical
contexts, for example the strong-gravity regime and the effective field theory
approach.


title: Analytical Description of Voids in Majumdar-Papapetrou Spacetimes

abstract:
  We discuss new Majumdar-Papapetrou solutions for the 3+1 Einstein-Maxwell
equations, with charged dust acting as the external source of the fields. The
solutions satisfy non-linear potential equations which are related to
well-known wave equations of 1+1 soliton physics. Although the matter
distributions are not localised, they present central structures which may be
identified with voids.


title:
Gravitational Radiation from a Naked Singularity. II - Even-Parity
  Perturbation -

abstract:
  A naked singularity occurs in the generic collapse of an inhomogeneous dust
ball. We study the even-parity mode of gravitational waves from a naked
singularity of the Lema\^{\i}tre-Tolman-Bondi spacetime. The wave equations for
gravitational waves are solved by numerical integration using the single null
coordinate. The result implies that the metric perturbation grows when it
approaches the Cauchy horizon and diverges there, although the naked
singularity is not a strong source of even-parity gravitational radiation.
Therefore, the Cauchy horizon in this spacetime should be unstable with respect
to linear even-parity perturbations.


title: Quintessence, scalar-tensor theories and non-Newtonian gravity

abstract:
  We discuss some of the issues which we encounter when we try to invoke the
scalar-tensor theories of gravitation as a theoretical basis of quintessence.
One of the advantages of appealing to these theories is that they allow us to
implement the scenario of a ``decaying cosmological constant,'' which offers a
reasonable understanding of why the observed upper bound of the cosmological
constant is smaller than the theoretically natural value by as much as 120
orders of magnitude. In this context, the scalar field can be a candidate of
quintessence in a broader sense. We find, however, a serious drawback in the
prototype Brans-Dicke model with $\Lambda$ added; a static universe in the
physical conformal frame which is chosen to have constant particle masses. We
propose a remedy by modifying the matter coupling of the scalar field taking
advantage of scale invariance and its breakdown through quantum anomaly. By
combining this with a conjecture on another cosmological constant problem
coming from the vacuum energy of matter fields, we expect a possible link
between quintessence and non-Newtonian gravity featuring violation of Weak
Equivalence Principle and intermediate force range, likely within the
experimental constraints. A new prediction is also offered on the
time-variability of the gravitational constant.


title: Black Hole Entropy in Induced Gravity and Information Loss

abstract:
  The basic assumption of the induced gravity approach is that Einstein theory
is an effective, low energy-form of a quantum theory of constituents. In this
approach the Bekenstein-Hawking entropy S^{BH} of a black hole can be
interpreted as a measure of the loss of information about constituents inside
the black hole horizon. To be more exact, S^{BH} is determined by quantum
correlations between "observable" and "non-observable" states with positive and
negative energy $\cal E$, respectively. It is important that for non-minimally
coupled constituents $\cal E$ differs from the canonical Hamiltonian $\cal H$.
This explains why previous definitions of the entanglement entropy in terms of
$\cal H$ failed to reproduce S^{BH}.


title: Separable Brane Cosmologies in Heterotic M-Theory

abstract:
  It is shown that any anisotropic and inhomogeneous cosmological solution to
the lowest-order, four-dimensional, dilaton-graviton string equations of motion
may be employed as a seed to derive a curved, three-brane cosmological solution
to five-dimensional heterotic M-theory compactified on a Calabi-Yau three-fold.
This correspondence formally relates a weakly coupled string cosmology directly
with a strongly coupled one. The asymptotic behaviour of a wide class of
spatially homogeneous braneworlds is deduced. Similar solutions may be derived
in toroidally compactified massive type IIA supergravity.


title:
A Mode of Unifying Gravitation and Strong Interactions Proposed by the
  Model of Expansive Nondecelerative Universe

abstract:
  The model of Expansive Nondecelerative Universe exploiting the Vaidya metrics
is used as a tool for unification of gravitation and strong interactions. The
proposed approach stems from the capability to localize the energy of
gravitational field and enables to reach a certain level in unifying the
general theory of relativity and quantum chromodynamics. A relationship between
the energy binding quarks and gravitational energy of virtual black holes is
rationalized.


title: Petrov types of slowly rotating fluid balls

abstract:
  Circularly rotating axisymmetric perfect fluid space-times are investigated
to second order in the small angular velocity. The conditions of various
special Petrov types are solved in a comoving tetrad formalism. A number of
theorems are stated on the possible Petrov types of various fluid models. It is
shown that Petrov type II solutions must reduce to the de Sitter spacetime in
the static limit. Two space-times with a physically satisfactory
energy-momentum tensor are investigated in detail. For the rotating
incompressible fluid, it is proven that the Petrov type cannot be D. The
equation of the rotation function $\omega $ can be solved for the Tolman type
IV fluid in terms of quadratures. It is also shown that the rotating version of
the Tolman IV space-time cannot be Petrov type D.


title: Uniqueness theorems for static black holes in metric-affine gravity

abstract:
  Using the equivalence theorem for the triplet ansatz sector of metric-affine
gravity (MAG) theories and the Einstein-Proca system, it is shown that the only
static black hole of the triplet sector of MAG is the Schwarzschild solution,
under the constraint (-4\beta_4 + k_1\beta_5/2k_0 + k_2\gamma_4/k_0)/\kappa z_4
\neq 0 on the coupling constants. For the special case (-4\beta_4 +
k_1\beta_5/2k_0 + k_2\gamma_4/k_0)/\kappa z_4 = 0, it follows that the only
static non-extremal black hole is the Reissner-Nordstr\"om one. The results can
be extended to exclude also the existence of soliton solutions of the triplet
sector of MAG.


title:
Violation of the cosmic no hair conjecture in Einstein-Maxwell-dilaton
  system

abstract:
  The cosmic no hair conjecture is tested in the spherically symmetric
Einstein-Maxwell-dilaton~(EMD) system with a positive cosmological constant
$\Lambda$. Firstly, we analytically show that once gravitational collapse
occurs in the massless dilaton case, the system of field equations breaks down
inevitably in outer communicating regions or at the boundary provided that a
future null infinity ${\cal I}^+$ exists. Next we find numerically the static
black hole solutions in the massive dilaton case and investigate their
properties for comparison with the massless case. It is shown that their
Abbott-Deser~(AD) mass are infinite, which implies that a spacetime with finite
AD mass does not approach a black hole solution after the gravitational
collapse. These results suggest that ${\cal I}^+$ cannot appear in the EMD
system once gravitational collapse occurs and hence the cosmic no hair
conjecture is violated in both the massless and the massive cases, in contrast
to general relativity.


title: Classical and Quantum Gravity on Conformal Superspace

abstract:
  The four-dimensional gauge group of general relativity corresponds to
arbitrary coordinate transformations on a four-manifold. Theories of gravity
with a dynamical structure remarkably like Einstein's theory can be obtained on
the basis of a four-dimensional gauge group of arbitrary coordinate and
conformal transformations of riemannian metrics defined on a three-manifold.
This new symmetry is more restrictive and hence more predictive. Many of the
difficulties that have plagued the canonical quantization of general relativity
seem to vanish.


title: Solving the horizon problem with a Delayed Big-Bang singularity

abstract:
  The hot Big-Bang standard model for the evolution of the universe, despite
strong successes, lets unresolved a number of problems. One of its main
drawbacks, known as the horizon problem, was until now thought to be only
solvable by an inflationary scenario. Here is proposed a class of inhomogeneous
models of universe, getting rid of some of the worst drawbacks of standard
cosmology. The horizon problem is solved by means of an initial singularity of
"delayed" type and without need for any inflationary phase. The flatness and
cosmological constant problems disappear.


title: Infinities in Quantum Gravities

abstract:
  We first present a review, intended for classical relativists, of the
ultraviolet difficulties faced by local quantum gravity theories in both the
usual Einstein versions and in their supergravity extensions, at least
perturbatively. These problems, present in arbitrary dimensions, are traceable
to the dimensionality of the Einstein constant. We then summarize very recent
results about supergravity at the highest allowed dimension, D=11, showing that
also this unique model suffers from infinities already at 2 loops, despite its
high degree of supersymmetry. The conclusion is that there is no viable
nonghost quantum field model that includes general relativity.


title: Dilatonic String through black holes

abstract:
  We study the gravi-dilaton field of a Schwarzschild black hole pierced by a
thin cosmic string in both massless and massive dilatonic gravity. We conclude
that in the thin vortex approximation the string's spacetime is asymptotically
flat with a conical deficit angle and that the inertial mass of the black hole
is different from the gravitational one. We generalize our results to charged
black holes.


title:
The Dynamics of Multi-Scalar Field Cosmological Models and Assisted
  Inflation

abstract:
  We investigate the dynamical properties of a class of spatially homogeneous
and isotropic cosmological models containing a barotropic perfect fluid and
multiple scalar fields with independent exponential potentials. We show that
the assisted inflationary scaling solution is the global late-time attractor
for the parameter values for which the model is inflationary, even when
curvature and barotropic matter are included. For all other parameter values
the multi-field curvature scaling solution is the global late-time attractor
(in these solutions asymptotically the curvature is not dynamically
negligible). Consequently, we find that in general all of the scalar fields in
multi-field models with exponential potentials are non-negligible in late-time
behaviour, contrary to what is commonly believed. The early-time and
intermediate behaviour of the models is also studied. In particular, n-scalar
field models are investigated and the structure of the saddle equilibrium
points corresponding to inflationary m-field scaling solutions and
non-inflationary m-field matter scaling solutions are also studied (where m<n),
leading to interesting transient dynamical behaviour with new physical
scenarios of potential importance.


title:
Algebraic Quantum Theory on Manifolds: A Haag-Kastler Setting for
  Quantum Geometry

abstract:
  Motivated by the invariance of current representations of quantum gravity
under diffeomorphisms much more general than isometries, the Haag-Kastler
setting is extended to manifolds without metric background structure. First,
the causal structure on a differentiable manifold M of arbitrary dimension
(d+1>2) can be defined in purely topological terms, via cones (C-causality).
Then, the general structure of a net of C*-algebras on a manifold M and its
causal properties required for an algebraic quantum field theory can be
described as an extension of the Haag-Kastler axiomatic framework.
  An important application is given with quantum geometry on a spatial slice
within the causally exterior region of a topological horizon H, resulting in a
net of Weyl algebras for states with an infinite number of intersection points
of edges and transversal (d-1)-faces within any neighbourhood of the spatial
boundary S^2.


title: On Kerr's corpuscle

abstract:
  Simple changes of the radial co-ordinate deprive Kerr's spinning corpuscle of
its marvellous properties.


title: Entropy of a Black Hole with Distinct Surface Gravities

abstract:
  In gravitational thermodynamics, the entropy of a black hole with distinct
surface gravities can be evaluated in a microcanonical ensemble. At the $WKB$
level, the entropy becomes the negative of the Euclidean action of the
constrained instanton, which is the seed for the black hole creation in the
no-boundary universe. Using the Gauss-Bonnet theorem, we prove the quite
universal formula in Euclidean quantum gravity that the entropy of a
nonrotating black hole is one quarter the sum of the products of the Euler
characteristics and the areas of the horizons. For Lovelock gravity, the
entropy and quantum creation of a black hole are also studied.


title:
Absorption rate of the Kerr-de Sitter black hole and the Kerr-Newman-de
  Sitter black hole

abstract:
  By using an analytic solution of the Teukolsky equation in the Kerr-de Sitter
and Kerr-Newman-de Sitter geometries, an analytic expression of the absorption
rate formulae for these black holes is calculated.


title:
Wormholes and Flux Tubes in the 7D Gravity on the Principal Bundle with
  SU(2) Gauge Group as the Extra Dimensions

abstract:
  Vacuum solutions for multidimensional gravity on the principal bundle with
the SU(2) structural group as the extra dimensions are found and discussed.
This generalizes the results of Ref. \cite{vds3} from U(1) to the SU(2) gauge
group. The spherically symmetric solution with the off-diagonal components of
the multidimensional metric is obtained. It is shown that two types of
solutions exist: the first has a wormhole-like 4D base, the second is a
gravitational flux tube with two color and electric charges. The solution
depends only on two parameters: the values of the electric and magnetic fields
at the origin. In the plane of these parameters there exists a curve separating
the regions with different types of solutions. An analogy with the 5D solutions
is discussed.


title:
On a possibility of scalar gravitational wave detection from the binary
  pulsar PSR 1913 +16

abstract:
  It is shown that detecting or setting an upper limit on the scalar
gravitational radiation is a good experimental test of relativistic gravity
theories. The relativistic tensor-field theory of gravitation is revised and it
is demonstrated that the scalar monopole gravitational radiation must be added
to the usual quadrupole radiation. In the case of the binary pulsar PSR 1913+16
it is predicted the existence 0.735 % excess of the gravitational radiation due
to the scalar gravitational waves.


title: Spin-spin effects in radiating compact binaries

abstract:
  The dynamics of a binary system with two spinning components on an eccentric
orbit is studied, with the inclusion of the spin-spin interaction terms
appearing at the second post-Newtonian order. A generalized true anomaly
parametrization properly describes the radial component of the motion. The
average over one radial period of the magnitude of the orbital angular momentum
$\bar{L}$ is found to have no nonradiative secular change. All spin-spin terms
in the secular radiative loss of the energy and magnitude of orbital angular
momentum are given in terms of $\bar{L}$ and other constants of the motion.
Among them, self-interaction spin effects are found, representing the second
post-Newtonian correction to the 3/2 post-Newtonian order Lense-Thirring
approximation.


title: Lorentz Covariant Theory of Precise Doppler Measurements

abstract:
  The Lorentz covariant theory of precise Doppler measurements (PDM) based on
the retarded Li\'{e}nard-Wiechert solution of the Einstein equations is
described. An exact solution of equations of light propagation in the field of
arbitrary moving bodies, which drastically extends the range of applicability
of the new theory of PDM, is obtained. An explicit formula for the
gravitational shift of frequency is given in analytic form. The limiting cases
of the Doppler observations in gravitational lensing and of the spacecraft's
Doppler tracking are described in more detail. We also present the
post-Newtonian theory of the PDM developed for searching relativistic effects
in close optical binaries and massive planetary systems.


title: Non-Singular Charged Black Hole Solution for Non-Linear Source

abstract:
  A non-singular exact black hole solution in General Relativity is presented.
The source is a non-linear electromagnetic field, which reduces to the Maxwell
theory for weak field. The solution corresponds to a charged black hole with
|q| \leq 2s_c m \approx 0.6 m, having metric, curvature invariants, and
electric field bounded everywhere.


title: Geometrical aspects of light propagation in nonlinear electrodynamics

abstract:
  We analyze the propagation of light in the context of nonlinear
electrodynamics, as it occurs in modified QED vacua. We show that the
corresponding characteristic equation can be described in terms of a
modification of the effective geometry of the underlying spacetime structure.
We present the general form for this effective geometry and exhibit some new
consequences that result from such approach.


title: On Holography in Brans-Dicke Cosmology

abstract:
  The holographic bound in Brans-Dicke $k=1$ matter dominated Cosmology is
discussed. In this talk, both the apparent horizon and the particle horizon are
taken for the holographic bound. The covariant entropy conjecture proposed by
Bousso is also discussed.


title: Eternal inflation and the present universe

abstract:
  Eternally inflating universes can contain thermalized regions with different
values of the cosmological parameters. In particular, the spectra of density
fluctuations should be different, because of the different realizations of
quantum fluctuations of the inflaton field. I discuss a general method for
calculating probability distributions for such variable parameters and analyse
the density fluctuation spectrum as a specific application.


title:
Quantized shells as a tool for studying semiclassical effects in general
  relativity

abstract:
  Thin shells in general relativity can be used both as models of collapsing
objects and as probes in the space-time outside compact sources. Therefore they
provide a useful tool for the analysis of the final fate of collapsing matter
and of the effects induced in the matter by strong gravitational fields. We
describe the radiating shell as a (second quantized) many-body system with one
collective degree of freedom, the (average) radius, by means of an effective
action which also entails a thermodynamic description. Then we study some of
the quantum effects that occur in the matter when the shell evolves from an
(essentially classical) large initial radius towards the singularity and
compute the corresponding backreaction on its trajectory.


title: Self-force approach for radiation reaction

abstract:
  We overview the recently proposed mode-sum regularization prescription (MSRP)
for the calculation of the local radiation-reaction forces, which are crucial
for the orbital evolution of binaries. We then describe some new results which
were obtained using MSRP, and discuss their importance for gravitational-wave
astronomy.


title:
Distance-redshift relation in an isotropic inhomogeneous universe II:
  Spherically symmetric dust-shell universe

abstract:
  The relation between the angular diameter distance and redshift in a
spherically symmetric dust-shell universe is studied. We have discovered that
the relation agrees with that of an appropriate Friedmann-Lemaitre (FL) model
if we set a ``homogeneous'' expansion law and a ``homogeneous'' averaged
density field. This will support the averaging hypothesis that a universe looks
like a FL model in spite of small-scale fluctuations of density field, if its
averaged density field is homogeneous on large scales. We also study the
connection of the proper mass of a shell with the mass of gravitationally bound
objects. Combining this with the results of the distance-redshift relation, we
discuss an impact of the local inhomogeneities on determination of the
cosmological parameters through the observation of the locally inhomogeneous
universe.


title: Entanglement entropy of the black hole horizon

abstract:
  We examine a possibility that, when a black hole is formed, the information
on the collapsed star is stored as the entanglement entropy between the outside
and the thin region (of the order of the Planck length) of the inside the
horizon. For this reason, we call this as the entanglement entropy of the black
hole ``horizon''. We construct two models, one is in the Minkowski spacetime
and the other is in the Rindler wedge. To calculate the entropy explicitly, we
assume that the thin regions of the order of the Planck length of the outside
and inside the horizon are completely entangled by quantum effects. We also use
a property of the entanglement entropy that it is symmetric under an
interchange of the observed and unobserved subsystems. Our setting and this
symmetric property substantially reduce the needed numerical calculation. As a
result of our analysis, we can explain the Bekenstein-Hawking entropy itself
(rather than its correction by matter fields) in the context of the
entanglement entropy.


title: The Origin of the Radiation Reaction Force

abstract:
  The emission of radiation from an accelerated charge is analyzed. It is found
that at zero velocity, the radiation emitted from the charge imparts no counter
momentum to the emitting charge, and no radiation reaction force is created by
the radiation. A reaction force is created by the stress force that exists in
the curved electric field of the charge, and the work done in overcoming this
force is the source of the energy carried by the radiation.


title: Slow-roll inflation without fine-tuning

abstract:
  The slow-roll approximation is the usual starting point to study the
constraints imposed on the inflaton potential parameters by the observational
data. We show that, for a potential exhibiting at least two extrema and giving
rise to a limited inflationary period, slow-roll does not have to be taken as
an additional hypothesis and is in fact forced by the constraints on the number
of e-foldings.


title: The Use of Quantum Algebras in Quantum Gravity

abstract:
  After a brief survey of the appearance of quantum algebras in diverse
contexts of quantum gravity, we demonstrate that the particular deformed
algebras, which arise within the approach of J.Nelson and T.Regge to 2+1
anti-de Sitter quantum gravity (for space surface of genus g) and which are
basic for generating the algebras of independent quantum observables, are in
fact isomorphic to the nonstandard q-deformed analogues U'_q(so_n) (introduced
in 1991) of Lie algebras of the orthogonal groups SO(n), with n linked to g as
n=2g+2.


title:
A General Definition of "Conserved Quantities" in General Relativity and
  Other Theories of Gravity

abstract:
  In general relativity, the notion of mass and other conserved quantities at
spatial infinity can be defined in a natural way via the Hamiltonian framework:
Each conserved quantity is associated with an asymptotic symmetry and the value
of the conserved quantity is defined to be the value of the Hamiltonian which
generates the canonical transformation on phase space corresponding to this
symmetry. However, such an approach cannot be employed to define `conserved
quantities' in a situation where symplectic current can be radiated away (such
as occurs at null infinity in general relativity) because there does not, in
general, exist a Hamiltonian which generates the given asymptotic symmetry.
(This fact is closely related to the fact that the desired `conserved
quantities' are not, in general, conserved!) In this paper we give a
prescription for defining `conserved quantities' by proposing a modification of
the equation that must be satisfied by a Hamiltonian. Our prescription is a
very general one, and is applicable to a very general class of asymptotic
conditions in arbitrary diffeomorphism covariant theories of gravity derivable
from a Lagrangian, although we have not investigated existence and uniqueness
issues in the most general contexts. In the case of general relativity with the
standard asymptotic conditions at null infinity, our prescription agrees with
the one proposed by Dray and Streubel from entirely different considerations.


title: Spacetime metric from linear electrodynamics II

abstract:
  Following Kottler, \'E.Cartan, and van Dantzig, we formulate the Maxwell
equations in a metric independent form in terms of the field strength $F=(E,B)$
and the excitation $H=({\cal D}, {\cal H})$. We assume a linear constitutive
law between $H$ and $F$. First we split off a pseudo-scalar (axion) field from
the constitutive tensor; its remaining 20 components can be used to define a
duality operator $^#$ for 2-forms. If we enforce the constraint $^{##}=-1$,
then we can derive of that the conformally invariant part of the {\em metric}
of spacetime.


title: Stable Inflationary Dissipative Cosmologies

abstract:
  The stability of the de Sitter era of cosmic expansion in spatially curved
homogeneous isotropic universes is studied. The source of the gravitational
field is an imperfect fluid such that the parameters that characterize it may
change with time. In this way we extend our previous analysis for
spatially-flat spaces as well as the work of Barrow.


title: Removing Instrumental Artifacts: Suspension Violin Modes

abstract:
  We describe the design of a Kalman filter that identifies suspension violin
modes in an interferometric gravitational wave detectors data channel. We
demonstrate the filter's effectiveness by applying it to data taken on the
LIGO~40M prototype.


title:
Backreaction to wormhole by classical scalar field: Will classical
  scalar field destroy wormhole?

abstract:
  There are two effects of extra matter fields on the Lorentzian traversable
wormhole. The ``primary effect'' says that the extra matter can afford to be a
part of source or whole source of the wormhole when the wormhole is being
formed. Thus the matter does not affect the stability of wormhole and the
wormhole is still safe. If the extra matter is extotic, it can be the whole
part of the source of the wormhole.
  The ``auxiliary effect'' is that the extra matter plays the role of the
additional matter to the stably-existed wormhole by the other exotic matter.
This additional matter will change the geometry of wormhole enough to prevent
from forming the wormhole by backreaction. In the minimally coupled massless
scalar field case, the self-consistent solution was found. The backreaction of
the scalar field can dominate the exotic matter part so that it will hinder the
formation of the wormhole.


title: Quantally fed steady-state domain distributions in Stochastic Inflation

abstract:
  Within the framework of stochastic inflationary cosmology we derive
steady-state distributions P_c(V) of domains in comoving coordinates, under the
assumption of slow-rolling and for two specific choices of the coarse-grained
inflaton potential $V(\Phi)$. We model the process as a Starobinsky-like
equation in V-space plus a time-independent source term P_w(V) which carries
(phenomenologically) quantum-mechanical information drawn from either of two
known solutions of the Wheeler-De Witt equation: Hartle-Hawking's and
Vilenkin's wave functions. The presence of the source term leads to the
existence of nontrivial steady-state distributions P^w_c(V). The relative
efficiencies of both mechanisms at different scales are compared for the
proposed potentials.


title:
Deriving the Regge-Wheeler and Zerilli equations in the general static
  spherically-symmetric case with Mathematica and MathTensor

abstract:
  An efficient approach to tensor perturbation calculations by proper use of
computer algebra methods is described, reaching the sufficient generality
required for a comprehensive analysis of the Schwarzschild and
Reissner-Nordstroem metric stability.


title:
Search for continuous gravitational wave signals from sources in binary
  systems

abstract:
  We analyze the computational costs of searches for continuous monochromatic
gravitational waves emitted by rotating neutron stars orbiting a companion
object. As a function of the relevant orbital parameters, we address the
computational load involved in targeted searches, where the position of the
source is known; the results are applied to known binary radio pulsars and
Sco-X1.


title: Bondi-type systems near space-like and null infinity

abstract:
  We discuss how asymptotic quantities, originally introduced on null infinity
in terms of Bondi-type gauge conditions, can be calculated near space-like
infinity to any desired precision.


title: Are pre-big-bang models falsifiable by gravitational wave experiments?

abstract:
  One of the most interesting predictions of string-inspired cosmological
models is the presence of a stochastic background of relic gravitational waves
in the frequency band accessible to Earth-based detectors. Here we consider a
``minimal'' class of string cosmology models and explore whether they are
falsifiable by gravitational wave observations. In particular, we show that,
the detectability of the signal depends crucially on the actual values of the
model parameters. This feature will enable laser interferometers -- starting
from the second generation of detectors -- to place stringent constraints on
the theory for a fairly large range of the free parameters of the model.


title:
Cosmic implications on thermodynamics and the explanation of the so
  called horizon problem

abstract:
  We show that there are implications on thermodynamics that come from the
existence of the initial cosmic singularity. At present time this is more a
conceptual change than an observable one. However at very early cosmic times
there is a big difference between the actual behavior of thermodynamic
quantities and the behavior assumed in the standard cosmological model. We
present the discussion of two systems: an ideal monatomic gas at present, and a
photon gas at the early Universe. We show the striking result that the entropy
density goes to zero as the cosmic time goes to zero. This in turn, provides an
explanation for the so called horizon problem.


title: The characteristic treatment of black holes

abstract:
  The characteristic initial value problem has been implemented as a robust
computational algorithm (the PITT NULL CODE), with direct application to binary
black holes. The event horizon can be analyzed by characteristic techniques as
a stand-alone object using an analytic conformal model which gives new insight
into the intrinsic geometry of binary black holes. When applied to a
non-axisymmetric horizon, the model reveals substantially new features.
Colliding black holes generically go through a toroidal phase before they
become spherical. The conformal structure of the horizon supplies part of the
data for a simulation of the exterior space-time and calculation of the
post-merger waveforms from a binary black hole inspiral.


title: Electrostatic solutions in Kaluza-Klein theory: geometry and stability

abstract:
  We investigate the family of electrostatic spherically symmetric solutions of
the five-dimensional Kaluza-Klein theory. Both charged and neutral cases are
considered. The analysis of the solutions, through their geometrical
properties, reveals the existence of black holes, wormholes and naked
singularities. A new class of regular solutions is identified. A monopole
perturbation study of all these solutions is carried out, enabling us to prove
analytically the stability of large classes of solutions. In particular, the
black hole solutions are stable, while for the regular solutions the stability
analysis leads to an eigenvalue problem.


title:
Vortex in a relativistic perfect isentropic fluid and Nambu Goto
  dynamics

abstract:
  By a weak deformation of the cylindrical symmetry of the potential vortex in
a relativistic perfect isentropic fluid, we study the possible dynamics of the
central line of this vortex. In "stiff" material the Nanbu-Goto equations are
obtained


title:
Perturbative evolution of nonlinear initial data for binary black holes:
  Zerilli vs. Teukolsky

abstract:
  We consider the problem of evolving nonlinear initial data in the close limit
regime. Metric and curvature perturbations of nonrotating black holes are
equivalent to first perturbative order, but Moncrief waveform in the former
case and Weyl scalar $\psi_4$ in the later differ when nonlinearities are
present. For exact Misner initial data (two equal mass black holes initially at
rest), metric perturbations evolved via the Zerilli equation suffer of a
premature break down (at proper separation of the holes $L/M\approx2.2$) while
the exact Weyl scalar $\psi_4$ evolved via the Teukolsky equation keeps a very
good agreement with full numerical results up to $L/M\approx3.5$. We argue that
this inequivalent behavior holds for a wider class of conformally flat initial
data than those studied here. We then discuss the relevance of these results
for second order perturbative computations and for perturbations to take over
full numerical evolutions of Einstein equations.


title: On the Birth of a Closed Hyperbolic Universe

abstract:
  We clarify and develop the results of a previous paper on the birth of a
closed universe of negative spatial curvature and multiply connected topology.
In particular we discuss the initial instanton and the second topology change
in more detail. This is followed by a short discussion of the results.


title: A Spacetime Map of the Universe

abstract:
  A geometric spacetime map of the universe is presented, addressing problems
inherent in deep space observations and cosmology. Implications for the
observer's perspective, the cosmological "horizon" and "flatness" problem,
"inflation", and the recently observed accelerating expansion of the Universe
are discussed.


title:
Flavor-oscillation clocks, continuous quantum measurements and a
  violation of Einstein equivalence principle

abstract:
  The relation between Einstein equivalence principle and a continuous quantum
measurement is analyzed in the context of the recently proposed
flavor-oscillation clocks, an idea pioneered by Ahluwalia and Burgard (Gen. Rel
Grav. Errata 29, 681 (1997)). We will calculate the measurement outputs if a
flavor-oscillation clock, which is immersed in a gravitational field, is
subject to a continuous quantum measurement. Afterwards, resorting to the weak
equivalence principle, we obtain the corresponding quantities in a freely
falling reference frame. Finally, comparing this last result with the
measurement outputs that would appear in a Minkowskian spacetime it will be
found that they do not coincide, in other words, we have a violation of
Einstein equivalence principle. This violation appears in two different forms,
namely: (i) the oscillation frequency in a freely falling reference frame does
not match with the case predicted by general relativity, a feature previously
obtained by Ahluwalia; (ii) the probability distribution of the measurement
outputs, obtained by an observer in a freely falling reference frame, does not
coincide with the results that would appear in the case of a Minkowskian
spacetime.


title: Relativistic perfect fluid models

abstract:
  The various schemes for studying rigidly rotating perfect fluids in general
relativity are reviewed. General conclusions one may draw from these are: (i)
There is a need to restrict the scope of the possible ansatze, and (ii) the
angular behaviour is a valuable commodity. This latter observation follows from
a large number of analytic models exhibiting a NUT-like behaviour. A method of
getting around problem (ii) is presented on a simple example. To alleviate
problem (i) for rigidly rotating perfect fluids, approximation schemes based on
a series expansion in the angular velocity are suggested. A pioneering work,
due to Hartle, explores the global properties of matched space-times to
quadratic order in the angular velocity.
  As a first example of the applications, it is shown that the rigidly rotating
incompressible fluid cannot be Petrov type D.


title: Gauge Theory of Oriented Media

abstract:
  The concept of wave field is introduced to represent oriented media. The wave
field is a tensor field of second rank, and directors are its eigenvectors.
This exhibition of directors defines a natural gauge group inherit in continua
and allows one to derive from variational principle general relativistic and
gauge invariant equations for the wave field in question. Thus, the
gauge-theoretical approach to continuum with internal degrees of freedom gives
unambiguous and minimally coupled theory.


title: Curvature blow up in Bianchi VIII and IX vacuum spacetimes

abstract:
  The maximal globally hyperbolic development of non-Taub-NUT Bianchi IX vacuum
initial data and of non-NUT Bianchi VIII vacuum initial data is C2
inextendible. Furthermore, a curvature invariant is unbounded in the incomplete
directions of inextendible causal geodesics.


title:
Friedmann Equation and Stability of Inflationary Higher Derivative
  Gravity

abstract:
  Stability analysis on the De Sitter universe in pure gravity theory is known
to be useful in many aspects. We first show how to complete the proof of an
earlier argument based on a redundant field equation. It is shown further that
the stability condition applies to $k \ne 0$ Friedmann-Robertson-Walker spaces
based on the non-redundant Friedmann equation derived from a simple effective
Lagrangian. We show how to derive this expression for the Friedmann equation of
pure gravity theory. This expression is also generalized to include scalar
field interactions.


title:
High-Frequency Gravitational Waves from Spinning Non-Abelian
  Cosmic-Strings

abstract:
  We investigated the SU(2) Einstein-Yang-Mills system on a time-dependent
non-diagonal cylindrical symmetric space-time. From the numerical
investigation, wave-like solutions are found, consistent with the familiar
string-like features. They possess an angle-deficit which depends on the
initial form of the magnetic component of the YM field, i.e., the number of
times it crosses the r-axis. The soliton-like behavior of the gravitational and
YM waves show significant differences from the ones found in the
Einstein-Maxwell system. The stability of the system is analyzed using the
multiple-scale method. To first order a consistent set of equations is
obtained.


title:
Dimensionally Reduced Gravity, Hermitian Symmetric Spaces and the
  Ashtekar Variables

abstract:
  Dimensional reductions of various higher dimensional (super)gravity theories
lead to effectively two-dimensional field theories described by gravity coupled
G/H nonlinear sigma-models. We show that a new set of complexified variables
can be introduced when G/H is a Hermitian symmetric space. This generalizes an
earlier construction that grew out of the Ashtekar formulation of two Killing
vector reduced pure 4d general relativity. Apart from giving some new insights
into dimensional reductions of higher dimensional (super)gravity theories,
these Ashtekar-type variables offer several technical advantages in the context
of the exact quantization of these models. As an application, an infinite set
of conserved charges is constructed. Our results might serve as a starting
point for probing the quantum equivalence of the Ashtekar and the metric
formalism within a non-trivial midi-superspace model of quantum gravity.


title: Semiclassical charged black holes with a quantized massive scalar field

abstract:
  Semiclassical perturbations to the Reissner-Nordstrom metric caused by the
presence of a quantized massive scalar field with arbitrary curvature coupling
are found to first order in \epsilon = \hbar/M^2. The DeWitt-Schwinger
approximation is used to determine the vacuum stress-energy tensor of the
massive scalar field. When the semiclassical perturbation are taken into
account, we find extreme black holes will have a charge-to-mass ratio that
exceeds unity, as measured at infinity. The effects of the perturbations on the
black hole temperature (surface gravity) are studied in detail, with particular
emphasis on near extreme ``bare'' states that might become precisely zero
temperature ``dressed'' semiclassical black hole states. We find that for
minimally or conformally coupled scalar fields there are no zero temperature
solutions among the perturbed black holes.


title: Experimental test for 5th dimension in Kaluza-Klein gravity

abstract:
  Several electric/magnetic charged solutions (dyons) to 5D Kaluza-Klein
gravity on the principal bundle are reviewed. Here we examine the possibility
that these solutions can act as quantum virtual wormholes in spacetime foam
models. By applying a sufficently large, external electric and/or magnetic
field it may be possible to ``inflate'' these solutions from a quantum to a
classical state. This effect could lead to a possible experimental signal for
higher dimensions in multidimensional gravity.


title: 2-Form Gravity of the Lorentzian Signature

abstract:
  We introduce a new spinorial, BF-like action for the Einstein gravity. This
is a first, up to our knowledge, 2-form action which describes the real,
Lorentzian gravity and uses only the self-dual connection. In the generic case,
the corresponding classical canonical theory is equivalent to the
Einstein-Ashtekar theory plus the reality conditions.


title: Cosmological models with one extra dimension

abstract:
  We consider cosmological models in which a homogeneous isotropic universe is
embedded as a 3+1 dimensional surface into a 4+1 dimensional manifold. The size
of the extra dimension depends on time. It is small compared to the size of the
universe only if the energy of gravitational self-interaction of the universe
through the compact extra dimension dominates over all other kinds of energy.
The self-interaction energy gives the main contribution into the Friedmann
equation, which governs the dynamics of the scale factor of the universe.


title:
Sustained resonance: a binary system perturbed by gravitational
  radiation

abstract:
  The general phenomena associated with sustained resonance are studied in this
paper in connection with relativistic binary pulsars. We represent such a
system by two point masses in a Keplerian binary system that evolves via
gravitational radiation damping as well as an external tidal perturbation. For
further simplification, we assume that the external tidal perturbation is
caused by a normally incident circularly polarized monochromatic gravitational
wave. In this case, the second-order partially averaged equations are studied
and a theorem of C. Robinson is employed to prove that for certain values of
the physical parameters resonance capture followed by sustained resonance is
possible in the averaged system. We conjecture that sustained resonance can
occur in the physical system when the perturbing influences nearly balance each
other.


title:
Anisotropic universes with isotropic cosmic microwave background
  radiation

abstract:
  We show the existence of spatially homogeneous but anisotropic cosmological
models whose cosmic microwave background temperature is exactly isotropic at
one instant of time but whose rate of expansion is highly anisotropic. The
existence of these models shows that the observation of a highly isotropic
cosmic microwave background temperature cannot alone be used to infer that the
universe is close to a Friedmann-Lemaitre model.


title: Brane-world cosmology

abstract:
  A simple model of the brane-world cosmology has been proposed, which is
characterized by four parameters, the bulk cosmological constant, the spatial
curvature of the universe, the radiation strength arising from bulk space-time
and the breaking parameter of $Z_2$-symmetry. The bulk space-time is assumed to
be locally static five-dimensional analogue of the Schwarzschild-anti-de Sitter
space-time, and then the location of three-brane is determined by metric
junction. The resulting Friedmann equation recovers standard cosmology, and a
new term arises if the assumption $Z_2$-symmetry is dropped, which behaves as
cosmological term in the early universe, next turns to negative curvature term,
and finally damps rapidly.


title: Field Theory of Gravitation: Desire and Reality

abstract:
  A retrospective analysis of the field theory of gravitation, describing
gravitational field in the same way as other fields of matter in the flat
space-time, is done. The field approach could be called "quantum gravidynamics"
to distinguish it from the "geometrodynamics" or general relativity. The basic
propositions and main conclusions of the field approach are discussed with
reference to classical works of Birkhoff, Moshinsky, Thirring, Kalman, Feynman,
Weinberg, Deser. In the case of weak fields both "gravidynamics" and
"geometrodynamics" give the same predictions for classical relativistic
effects. However, in the case of strong field, and taking into account quantum
nature of the gravitational interaction, they are profoundly different.
Contents of the paper: 1) Introduction; 2) Two ways in gravity theory:
2.1.Hypotheses of Poincar\'e and Einstein, 2.2. Gravity as a geometry of space,
2.3. Gravitation as a material field in flat space-time; 3) Classical theory of
tensor field: 3.1.Works of Birkhoff and Moshinsky, 3.2.Works of Thirring and
Kalman, 3.3.Thirring and Deser about identity of GR and FTG; 4) Quantum theory
of tensor field; 5) Modern problems in field theory of gravitation:
5.1.Multicomponent nature of tensor field, 5.2.Choice of energy-momentum tensor
of gravitational field, 5.3.Absence of black holes in FTG, 5.4.Astrophysical
tests of FTG; 6) Conclusions.


title:
An Efficient Method for Fully Relativistic Simulations of Coalescing
  Binary Neutron Stars

abstract:
  The merger of two neutron stars has been proposed as a source of gamma-ray
bursts, r-process elements, and detectable gravitational waves. Extracting
information from observations of these phenomena requires fully relativistic
simulations. Unfortunately, the only demonstrated method for stably evolving
neutron stars requires solving elliptic equations at each time step, adding
substantially to the computational resources required. In this paper we present
a simpler, more efficient method. The key insight is in how we apply numerical
diffusion. We perform a number of tests to validate the method and our
implementation. We also carry out a very rough simulation of coalescence and
extraction of the gravitational waves to show that the method is viable if
realistic initial data are provided.


title: A Solution to the Graceful Exit Problem in Pre-Big Bang Cosmology

abstract:
  We examine the string cosmology equations with a dilaton potential in the
context of the Pre-Big Bang Scenario with the desired scale factor duality, and
give a generic algorithm for obtaining solutions with appropriate evolutionary
properties. This enables us to find pre-big bang type solutions with suitable
dilaton behaviour that are regular at $t=0$, thereby solving the graceful exit
problem. However to avoid fine tuning of initial data, an `exotic' equation of
state is needed that relates the fluid properties to the dilaton field. We
discuss why such an equation of state should be required for reliable dilaton
behaviour at late times.


title:
Particle dynamics on hyperboloid and unitary representation of SO(1,N)
  group

abstract:
  We analyze particle dynamics on $N$ dimensional one-sheet hyperboloid
embedded in $N+1$ dimensional Minkowski space. The dynamical integrals
constructed by $SO_\uparrow (1,N)$ symmetry of spacetime are used for the
gauge-invariant Hamiltonian reduction. The physical phase-space parametrizes
the set of all classical trajectories on the hyperboloid. In quantum case the
operator ordering problem for the symmetry generators is solved by
transformation to asymptotic variables. Canonical quantization leads to unitary
irreducible representation of $SO_\uparrow (1,N)$ group on Hilbert space
$L^2(S^{N-1})$.


title: Quantum Features of Non-Symmetric Geometries

abstract:
  Paths in an appropriate geometry are usually used as trajectories of test
particles in geometric theories of gravity. It is shown that non-symmetric
geometries possess some interesting quantum features. Without carrying out any
quantization schemes, paths in such geometries are naturally quantized. Two
different non-symmetric geometries are examined for these features. It is
proved that, whatever the non-symmetric geometry is, we always get the same
quantum features. It is shown that these features appear only in the pure
torsion term (the anti-symmetric part of the affine connection) of the path
equations. The vanishing of the torsion leads to the disappearance of these
features, regardless of the symmetric part of the connection. It is suggested
that, in order to be consistent with the results of experiments and
observations, torsion term in path equations should be parametrized using an
appropriate parameter.


title: Dynamical properties of the conformally coupled flat FRW model

abstract:
  In this paper we study the dynamical behaviour of a simple cosmological model
defined by a spatially flat Robertson-Walker geometry, conformally coupled with
a massive scalar field. We determine a Lyapunov-like function for the
non-linear evolution equations. From this function we prove that all the
stationary solutions are unstable. We also show that all initial conditions,
different from the stationary points, originate an expanding universe in the
asymptotic regime, with a scale parameter $a(t)$ that goes to infinity and the
scalar field $\phi (t)$ that goes to zero in an oscillatory way . We also find
two asymptotic solutions, valid for sufficiently large values of time. These
solutions correspond to a radiation dominated phase and to a matter dominated
phase, respectively.


title: Numerical Relativity in 3+1 Dimensions

abstract:
  Numerical relativity is finally approaching a state where the evolution of
rather general (3+1)-dimensional data sets can be computed in order to solve
the Einstein equations. After a general introduction, three topics of current
interest are briefly reviewed: binary black hole mergers, the evolution of
strong gravitational waves, and shift conditions for neutron star binaries.


title:
Mode sum regularization approach for the self-force in black hole
  spacetime

abstract:
  We present a method for calculating the self-force (the ``radiation reaction
force'') acting on a charged particle moving in a strong field orbit in black
hole spacetime. In this approach, one first calculates the contribution to the
self-force due to each multipole mode of the particle's field. Then, the sum
over modes is evaluated, subject to a certain regularization procedure. Here we
develop this regularization procedure for a scalar charge on a Schwarzschild
background, and present the results of its implementation for radial
trajectories (not necessarily geodesic).


title: Is Loop Quantum Gravity a QFT ?

abstract:
  We investigate up to which extend the kinematic setting of loop quantum
gravity can be fit into a diffeomorphism invariant setting of algebraic QFT
generalizing the Haag-Kastler setting of Wightman type QFT. The net of local
(Weyl-)algebras resulting from a spin network state of quantum geometry
immediately accommodates isotony and diffeomorphism covariance, and formulation
of causality becomes possible via of diffeomorphism invariant foliations of the
underlying manifold by cones. On a spatial horizon, quantum geometry becomes
asymptotically a genuine QFT with infinitely many degrees of freedom, if the
cylinder functions' supporting graphs intersect the inner boundary spheres in
an infinite number of punctures.


title: Multidimensional Sigma-Model with Black Holes and p-Branes

abstract:
  The bosonic content of string theory in curved background of multidimensional
structure with p-branes has a systematic geometrical description as an
effective sigma-model of gravity in lower dimension (say 3+1) with additional
interacting dilatonic and p-brane fields. If the target-space is locally
symmetric, solutions with intersecting p-branes can be found. Some static
solutions are p-brane generalizations of black holes (including the standard
Reissner-Nordstr"om class), which allow the prediction of detectable features
of the higher-dimensional p-brane geometry via scaling properties of black hole
thermal properties. E.g. the Hawking temperature T_H depends critically on the
p-brane intersection topology.


title: Coframe teleparallel models of gravity. Exact solutions

abstract:
  The superstring and superbrane theories which include gravity as a necessary
and fundamental part renew an interest to alternative representations of
general relativity as well as the alternative models of gravity. We study the
coframe teleparallel theory of gravity with a most general quadratic
Lagrangian. The coframe field on a differentiable manifold is a basic dynamical
variable. A metric tensor as well as a metric compatible connection is
generated by a coframe in a unique manner. The Lagrangian is a general linear
combination of Weitzenb\"{o}ck's quadratic invariants with free dimensionless
parameters $\r_1,\r_2,\r_3$.
  Every independent term of the Lagrangian is a global SO(1,3)-invariant
4-form. For a special choice of parameters which confirms with the local
SO(1,3) invariance this theory gives an alternative description of Einsteinian
gravity - teleparallel equivalent of GR.
  We prove that the sign of the scalar curvature of a metric generated by a
static spherical-symmetric solution depends only on a relation between the free
parameters. The scalar curvature vanishes only for a subclass of models with
$\r_1=0$. This subclass includes the teleparallel equivalent of GR. We obtain
the explicit form of all spherically symmetric static solutions of the
``diagonal'' type to the field equations for an arbitrary choice of free
parameters. We prove that the unique asymptotic-flat solution with Newtonian
limit is the Schwarzschild solution that holds for a subclass of teleparallel
models with $\r_1=0$. Thus the Yang-Mills-type term of the general quadratic
coframe Lagrangian should be rejected.


title:
Probing the anisotropic velocity of light in a gravitational field:
  another test of general relativity

abstract:
  A corollary of general relativity that the average velocity of light between
two points in a gravitational field is anisotropic has been overlooked. It is
shown that this anisotropy can be probed by an experiment which constitutes
another test of general relativity.


title: Chaos in the Hill system

abstract:
  We define the general Hill system and briefly analyze its dynamical behavior.
A particular Hill system representing the interaction of a Keplerian binary
system with a normally incident circularly polarized gravitational wave is
discussed in detail. In this case, we compute the Poincar\'e-Melnikov function
explicitly and determine its zeros. Moreover, we provide numerical evidence in
favor of chaos in this system. The partially averaged equations for the Hill
system are used to predict the regular behavior of the Keplerian orbit at
resonance with the external radiation.


title: Quantum charged fields in Rindler space

abstract:
  We study, using Rindler coordinates, the quantization of a charged scalar
field interacting with a constant, external, electric field. First we establish
the expression of the Schwinger vacuum decay rate, using the operator
formalism. Then we rederive it in the framework of the Feynman path integral
method. Our analysis reinforces the conjecture which identifies the zero
winding sector of the Minkowski propagator with the Rindler propagator.
Moreover we compute the expression of the Unruh's modes that allow to make
connection between Minkowskian and Rindlerian quantization scheme by purely
algebraic relations. We use these modes to study the physics of a charged two
level detector moving in an electric field whose transitions are due to the
exchange of charged quanta. In the limit where the Schwinger pair production
mechanism of the exchanged quanta becomes negligible we recover the Boltzman
equilibrium ratio for the population of the levels of the detector. Finally we
explicitly show how the detector can be taken as the large mass and charge
limit of an interacting fields system.


title:
Pragmatic approach to gravitational radiation reaction in binary black
  holes

abstract:
  We study the relativistic orbit of binary black holes in systems with small
mass ratio. The trajectory of the smaller object (another black hole or a
neutron star), represented as a particle, is determined by the geodesic
equation on the perturbed massive black hole spacetime. The particle itself
generates the gravitational perturbations leading to a problem that needs
regularization. Here we study perturbations around a Schwarzschild black hole
using Moncrief's gauge invariant formalism. We decompose the perturbations into
$\ell-$multipoles to show that all $\ell-$metric coefficients are $C^0$ at the
location of the particle. Summing over $\ell$, to reconstruct the full metric,
gives a formally divergent result. We succeed in bringing this sum to a
generalized Riemann's $\zeta-$function regularization scheme and show that this
is tantamount to subtract the $\ell\to\infty$ piece to each multipole. We
explicitly carry out this regularization and numerically compute the first
order geodesics. Application of this method to general orbits around rotating
black holes would generate accurate templates for gravitational wave laser
interferometric detectors.


title: Nondifferentiable Dynamic: Two Examples

abstract:
  Some nondifferentiable quantities (for example, the metric signature) can be
the independent physical degrees of freedom. It is supposed that in quantum
gravity these degrees of freedom can fluctuate. Two examples of such quantum
fluctuation are considered: a quantum interchange of the sign of two components
of the 5D metric and a quantum fluctuation between Euclidean and Lorentzian
metrics. The first case leads to a spin-like structure on the throat of
composite wormhole and to a possible inner structure of the string. The second
case leads to a quantum birth of the non-singular Euclidean Universe with
frozen $5^{th}$ dimension. The probability for such quantum fluctuations is
connected with an algorithmical complexity of the Einstein equations.


title: Non-tilted Bianchi VII_0 models - the radiation fluid

abstract:
  We consider the late time behaviour of non-tilted perfect fluid Bianchi VII_0
models when the source is a radiation fluid, thereby completing the analysis of
the Bianchi VII_0 models initiated by Wainwright et al in a recent paper. The
models exhibit the phenomena of asymptotic self-similarity breaking and
Weyl-curvature dominance at late times. The late time dynamics of the VII_0
perfect fluid models, and in particular that of the radiation fluid, is a prime
example of the complexity inherent in the field equations of general
relativity.


title:
Stress-energy tensor of neutral massive fields in the Reissner-Nordstrom
  spacetime

abstract:
  The approximation of the renormalized stress-energy tensor of the quantized
massive scalar, spinor, and vector field in the Reissner- Nordstrom spacetime
is constructed. It is achieved by functional differentiation of the lowest
order of the Schwinger-DeWitt effective action involving coincidence limit of
the Hadamard-Minakshisundaram-DeWitt-Seely coefficient a_{3}, and restricting
thus obtained general formulas to spacetimes with vanishing curvature scalar.
For the massive scalar field with arbitrary curvature coupling our results
reproduce those obtained previously by Anderson, Hiscock, and Samuel by means
of 6-th order WKB approximation.


title: Approximate Symmetries in General Relativity

abstract:
  The problem of finding an appropriate geometrical/physical index for
measuring a degree of inhomogeneity for a given space-time manifold is posed.
Interrelations with the problem of understanding the
gravitational/informational entropy are pointed out. An approach based on the
notion of approximate symmetry is proposed. A number of related results on
definitions of approximate symmetries known from literature are briefly
reviewed with emphasis on their geometrical/physical content. A definition of a
Killing-like symmetry is given and a classification theorem for all possible
averaged space-times acquiring Killing-like symmetries upon averaging out a
space-time with a homothetic Killing symmetry is proved.


title: An Extension of Schwarzschild Space to r=0

abstract:
  A more rigorous treatment of the Schwarzschild metric by making use of the
energy-momentum tensor of a single point particle as source term shows that
  $g_{00}=-\{1-\frac{2GM}{c^2r}-\frac{8G^2 M^2}{c^4 r^2}(\theta (r)-1)\}\exp
[2(\theta (r)-1)]$
  $g_{rr}=\{1-\frac{2GM}{c^2r}-\frac{8G^2 M^2}{c^4 r^2}(\theta (r)-1)\}^{-1}$
  The existence of a discontinuity at r=0 leads to an infinite repulsive force
that will change the ultimate fate of a free fall test particle to a bouncing
state.


title: The cosmological gravitating $\sigma$ model: solitons and black holes

abstract:
  We derive and analyze exact static solutions to the gravitating O(3) $\sigma$
model with cosmological constant in (2+1) dimensions. Both signs of the
gravitational and cosmological constants are considered. Our solutions include
geodesically complete spacetimes, and two classes of black holes.


title: The Mathematics of the Spinning Particle Problem

abstract:
  We introduce an original approach to geometric calculus in which we define
derivatives and integrals on functions which depend on extended bodies in
space--that is, paths, surfaces, and volumes etc. Though this theory remains to
be fully completed, we present it at its current stage of development, and
discuss it's connection to physical research, in particular its application to
spinning particles in curved space.


title:
Dimensionally Democratic Calculus and Principles of Polydimensional
  Physics

abstract:
  A solution to the 50 year old problem of a spinning particle in curved space
has been recently derived using an extension of Clifford calculus in which each
geometric element has its own coordinate. This leads us to propose that all the
laws of physics should obey new polydimensional metaprinciples, for which
Clifford algebra is the natural language of expression, just as tensors were
for general relativity. Specifically, phenomena and physical laws should be
invariant under local automorphism transformations which reshuffle the physical
geometry. This leads to a new generalized unified basis for classical
mechanics, which includes string theory, membrane theory and the hypergravity
formulation of Crawford[J. Math. Phys., {\bf 35}, 2701-2718 (1994)]. Most
important is that the broad themes presented can be exploited by nearly
everyone in the field as a framework to generalize both the Clifford calculus
and multivector physics.


title:
Prospects for gravitational-wave observations of neutron-star tidal
  disruption in neutron-star/black-hole binaries

abstract:
  For an inspiraling neutron-star/black-hole binary (NS/BH), we estimate the
gravity-wave frequency f_td at the onset of NS tidal disruption. We model the
NS as a tidally distorted, homogeneous, Newtonian ellipsoid on a circular,
equatorial geodesic around a Kerr BH. We find that f_td depends strongly on the
NS radius R, and estimate that LIGO-II (ca. 2006-2008) might measure R to 15%
precision at 140 Mpc (about 1 event/yr under current estimates). This suggests
that LIGO-II might extract valuable information about the NS equation of state
from tidal-disruption waves.


title: Gravitomagnetism and the Clock Effect

abstract:
  The main theoretical aspects of gravitomagnetism are reviewed. It is shown
that the gravitomagnetic precession of a gyroscope is intimately connected with
the special temporal structure around a rotating mass that is revealed by the
gravitomagnetic clock effect. This remarkable effect, which involves the
difference in the proper periods of a standard clock in prograde and retrograde
circular geodesic orbits around a rotating mass, is discussed in detail. The
implications of this effect for the notion of ``inertial dragging'' in the
general theory of relativity are presented. The theory of the clock effect is
developed within the PPN framework and the possibility of measuring it via
spaceborne clocks is examined.


title:
The field equation from Newton's law of motion and absence of magnetic
  monopole

abstract:
  By requiring the linear differential operator in Newton's law of motion to be
self adjoint, we obtain the field equation for the linear theory, which is the
classical electrodynamics. In the process, we are also led to a fundamental
universal chiral relation between electric and magnetic monopoles which implies
that the two are related. Thus there could just exist only one kind of charge
which is conventionally called electric.


title:
An efficient Matched Filtering Algorithm for the Detection of Continuous
  Gravitational Wave Signals

abstract:
  We describe an efficient method of matched filtering over long (greater than
1 day) time baselines starting from Fourier transforms of short durations
(roughly 30 minutes) of the data stream. This method plays a crucial role in
the search algorithm developed by Schutz and Papa for the detection of
continuous gravitational waves from pulsars. Also, we discuss the computational
cost--saving approximations used in this method, and the resultant performance
of the search algorithm.


title: Cauchy boundaries in linearized gravitational theory

abstract:
  We investigate the numerical stability of Cauchy evolution of linearized
gravitational theory in a 3-dimensional bounded domain. Criteria of robust
stability are proposed, developed into a testbed and used to study various
evolution-boundary algorithms. We construct a standard explicit finite
difference code which solves the unconstrained linearized Einstein equations in
the 3+1 formulation and measure its stability properties under Dirichlet,
Neumann and Sommerfeld boundary conditions. We demonstrate the robust stability
of a specific evolution-boundary algorithm under random constraint violating
initial data and random boundary data.


title: Gravitational waves from inspiral into massive black holes

abstract:
  Space-based gravitational-wave interferometers such as LISA will be sensitive
to the inspiral of stellar mass compact objects into black holes with masses in
the range of roughly 10^5 solar masses to (a few) 10^7 solar masses. During the
last year of inspiral, the compact body spends several hundred thousand orbits
spiraling from several Schwarzschild radii to the last stable orbit. The
gravitational waves emitted from these orbits probe the strong-field region of
the black hole spacetime and can make possible high precision tests and
measurements of the black hole's properties. Measuring such waves will require
a good theoretical understanding of the waves' properties, which in turn
requires a good understanding of strong-field radiation reaction and of
properties of the black hole's astrophysical environment which could complicate
waveform generation. In these proceedings, I review estimates of the rate at
which such inspirals occur in the universe, and discuss what is being done and
what must be done further in order to calculate the inspiral waveform.


title: Mass of Colored Black Holes

abstract:
  New results pertaining to colored static black hole solutions to the
Einstein-Yang-Mills equations are obtained. The isolated horizons framework is
used to define the concept of Hamiltonian Horizon Mass of the black hole. An
unexpected relation between the ADM and Horizon masses of the black hole
solution with the ADM mass of the corresponding Bartnik-McKinnon soliton is
found. These results can be generalized to other non-linear theories and they
suggest a general testing bed for the instability of the corresponding hairy
black holes.


title: An Ermakov study of Q not zero EFRW minisuperspace oscillators

abstract:
  A previous work on the Ermakov approach for empty FRW minisuperspace
universes of Hartle-Hawking factor ordering parameter Q=0 is extended to the Q
not zero cases


title: On energy-momentum tensors of gravitational field

abstract:
  Several energy-momentum "tensors" of gravitational field are considered and
compared in the lowest approximation. Each of them together with
energy-momentum tensor of point-like particles satisfies the conservation laws
when equations of motion of particles are the same as in general relativity. It
is shown that in Newtonian approximation the considered tensors differ one from
the other in the way their energy density is distributed between energy density
of interaction (nonzero only at locations of particles) and energy density of
gravitational field. Starting from Lorentz invariance the Lagrangians for
spin-2, mass-0 field are considered. They differ only by divergences. From
these Lagrangians by Belinfante-Rosenfeld procedure the energy-momentum tensors
are build. Using each of these tensors in 3-graviton vertex we obtain the
corresponding metric of a Newtonian center in $G^2$ approximation. Only one of
these ''field-theretical''tensors (namely the half sum of Thirring tensor and
tensor obtained from Lagrangian given by Misner, Thorne and Wheeler) leads to
correct value of the perihelion shift. This tensor does not coincide with
Weinberg`s one (directly obtainable from Einstein equation) and gives metric of
a spherical body differing (in space part of metric in the first nonlinear
approximation) from Schwarzschild field in harmonic coordinates. As a result a
relativistic particle in such field must move note according general relativity
prescriptions. This approach puts the gravitational energy-momentum tensor on
the same footing as any other energy-momentum tensor.


title:
Upgraded VIRGO detector(s) and stochastic gravitational waves
  backgrounds

abstract:
  The sensitivity achievable by a pair of VIRGO detectors to stochastic and
isotropic gravitational wave backgrounds of cosmological origin is discussed in
view of the development of a second VIRGO interferometer. We describe a
semi-analytical technique allowing to compute the signal-to-noise ratio for
(monotonic or non-monotonic) logarithmic energy spectra of relic gravitons of
arbitrary slope. We apply our results to the case of two correlated and
coaligned VIRGO detectors and we compute their achievable sensitivities. The
maximization of the overlap reduction function is discussed. We focus our
attention on a class of models whose expected sensitivity is more promising,
namely the case of string cosmological gravitons. We perform our calculations
both for the case of minimal string cosmological scenario and in the case of a
non-minimal scenario where a long dilaton dominated phase is present prior to
the onset of the ordinary radiation dominated phase. In this framework, we
study possible improvements of the achievable sensitivities by selective
reduction of the thermal contributions (pendulum and pendulum's internal modes)
to the noise power spectra of the detectors. Since a reduction of the shot
noise does not increase significantly the expected sensitivity of a VIRGO pair
(in spite of the relative spatial location of the two detectors) our findings
support the experimental efforts directed towards a substantial reduction of
thermal noise.


title: The Scalar-Tensor Inflationary Cosmology

abstract:
  In this paper the scalar-tensor theory of gravity is assumed to describe the
evolution of the universe and the gravitational scalar $\phi$ is ascribed to
play the role of inflaton. The theory is characterized by the specified
coupling function $\omega(\phi)$ and the cosmological function $\lambda(\phi)$.
The function $\lambda(\phi)$ is nearly constant for $0<\phi<0.1$ and
$\lambda(1)=0$. The functions $\lambda(\phi)$ and $\omega(\phi)$ provide a
double-well potential for the motion of $\phi(t)$. Inflation commences and ends
naturally by the dynamics of the scalar field. The energy density of matter
increases steadily during inflation. When the constant $\Gamma$ in the action
is determined by the present matter density, the temperature at the end of
inflation is of the order of $10^{14} GeV$ in no need of reheating.
Furthermore, the gravitational scalar is just the cold dark matter that men
seek for.


title:
A quantum mechanical derivation of Gamow's relation for the time and
  temperature of the expanding Universe

abstract:
  The quantum mechanical approach developed by us recently for the evolution of
the universe is used to derive an alternative derivation connecting the
temperature of the cosmic background radiation and the age of the universe
which is found to be similar to the one obtained by Gamow long back. By
assuming the age of the universe to be $\approx$ 20 billion years, we reproduce
a value of $\approx$ 2.91 K for the cosmic back-ground radiation, agreeing well
with the recently measured experimental value of 2.728 K. Besides, this theory
enables us to calculate the photon density and entropy associated with the
background radiation and the ratio of the number of photons to the number of
nucleons, which quantitatively agree with the results obtained by others.


title:
A problem of hypothetical emerging of matter objects on horizon in the
  standard model of universe

abstract:
  In the standard model of universe the increase in mass of our observed
expansive Universe is explained by the assumption of emerging the matter
objects on the horizon (of the most remote visibility). However, the physical
analysis of the influence of this assumption on the velocity of matter objects
shows unambiguously that this hypothetical assumption contradicts the theory of
gravity.


title: Global solutions in gravity

abstract:
  The method of conformal blocks for construction of global solutions in
gravity for a two-dimensional metric having one Killing vector field is
described.


title: A Probe Particle in Kerr-Newman-deSitter Cosmos

abstract:
  We consider the force acting on a spinning charged test particle (probe
particle) with the mass m and the charge q in slow rotating the
Kerr-Newman-deSitter(KNdS) black hole with the mass M and the charge Q. We
consider the case which the spin vector of the probe particle is parallel to
the angular momentum vector of the KNdS space-time. We take account of the
gravitational spin-spin interaction under the slow rotating limit of the KNdS
space-time. When Q=M and q=m, we show that the force balance holds including
the spin-spin interaction and the motion is approximately same as that of a
particle in the deSitter space-time. This force cancellation suggests the
possibility of the existence of an exact solution of spinning multi-KNdS black
hole.


title:
Post-Newtonian Approximation of a Scalar Theory of Gravitation and
  Application to Light Rays

abstract:
  A scalar, preferred-frame theory of gravitation is summarized. Space-time is
endowed with both a flat metric and a curved, "physical" metric. Motion is
governed by a natural extension of Newton's second law, which implies geodesic
motion only for a static field. The theory predicts Schwarzschild's exterior
metric in the spherical static situation. It also predicts gravitation waves
with the velocity of light. The equations of motion are recast into the "flat
space - uniform time" form, and compared with the geodesic equations of motion.
The principles of the post-Newtonian approximation of this theory are given,
including the way to account for preferred-frame effects. This approximation is
then developed more particularly for photons. It is found that the
preferred-frame effects do not occur in this case, nor does the difference
between Newton's second law and geodesic assumption. Thus, the post-Newtonian
predictions of this theory for photons are indistinguishable from the standard
post-Newtonian predictions of general relativity.


title:
In Search of Local Degrees of Freedom in Quadratic Diff-invariant
  Lagrangians

abstract:
  We show that local diff-invariant free field theories in four spacetime
dimensions do not have local degrees of freedom.


title: Measuring the strength of dissipative inflation

abstract:
  We comment on recently proposed dissipative inflationary models. It is shown
that the strength of the inflationary expansion is related to a specific
combination of thermodynamic variables which is known to measure the
instability of self-gravitating dissipative systems.


title: Cosmological perturbations on a magnetised Bianchi I background

abstract:
  Motivated by the isotropy of the CMB spectrum, all existing studies of
magnetised cosmological perturbations employ FRW backgrounds. However, it is
important, to know the limits of this approximation and the effects one loses
by neglecting the anisotropy of the background magnetic field. We develop a new
treatment, which fully incorporates the anisotropic magnetic effects by
allowing for a Bianchi I background universe. The anisotropy of the unperturbed
model facilitates the closer study of the coupling between magnetism and
geometry. The latter leads to a curvature stress, which accelerates positively
curved perturbed regions and balances the effect of magnetic pressure gradients
on matter condensations. We argue that the tension carried along the magnetic
force-lines is the reason behind these magneto-curvature effects. For a
relatively weak field, we also compare to the results of the almost-FRW
approach. We find that some of the effects identified by the FRW treatment are
in fact direction dependent, where the key direction is that of the background
magnetic field vector. Nevertheless, the FRW-based approach to magnetised
cosmological perturbations remains an accurate approximation, particularly on
large scales, when one looks at the lowest order magnetic impact on
gravitational collapse. On small scales however, the accuracy of the perturbed
Friedmann framework may be compromised by extra shear effects.


title: An introduction to the Lorentz-Dirac equation

abstract:
  These notes provide two derivations of the Lorentz-Dirac equation. The first
is patterned after Landau and Lifshitz and is based on the observation that the
half-retarded minus half-advanced potential is entirely responsible for the
radiation-reaction force. The second is patterned after Dirac, and is based
upon considerations of energy-momentum conservation; it relies exclusively on
the retarded potential. The notes conclude with a discussion of the
difficulties associated with the interpretation of the Lorentz-Dirac equation
as an equation of motion for a point charge. The presentation is essentially
self-contained, but the reader is assumed to possess some elements of
differential geometry (necessary for the second derivation only).


title: Can Black Hole be Created at the Birth of the Universe?

abstract:
  We study the quantum creation of black hole pairs in the (anti-)de Sitter
space background. These black hole pairs in the Kerr-Newman family are created
from constrained instantons. At the $WKB$ level, for the chargeless and
nonrotating case, the relative creation probability is the exponential of (the
negative of) the entropy of the universe. Also for the remaining cases of the
family, the creation probability is the exponential of (the negative of) one
quarter of the sum of the inner and outer black hole horizon areas. In the
absence of a general no-boundary proposal for open universes, we treat the
creations of the closed and the open universes in the same way.


title: Bianchi V inflation in the Brans-Dicke theory?

abstract:
  It is shown some exact solutions in the Brans-Dicke (BD) theory for a Bianchi
V metric having the property of inflationary expansion, graceful exit, and
asymptotic evolution to a Friedmann-Robertson-Walker (FRW) open model. It is
remarkable that an inflationary behaviour can occur, even without a
cosmological potential or constant. However, the horizon and flatness problems
cannot be solve within the standard BD theory because the inflationary period
is severely restricted by the value of the BD parameter $\omega$.


title: Supersymmetric Quantum Mechanics for Bianchi Class A models

abstract:
  In this work we present cosmological quantum solutions for all Bianchi Class
A cosmological models obtained by means of supersymmetric quantum mechanics .
We are able to write one general expression for all bosonic components occuring
in the Grassmann expansion of the wave function of the Universe for this class
of models. These solutions are obtained by means of a more general ansatz for
the so-called master equations.


title: Recent developments in quantum string cosmology

abstract:
  In this talk we discuss the quantisation of a class of string cosmology
models characterised by scale factor duality invariance. The amplitudes for the
full set of classically allowed and forbidden transitions are computed by
applying the reduced phase space and path integral methods. In particular, the
path integral calculation clarifies the meaning of the instanton-like behaviour
of the transition amplitudes that has been first pointed out in previous
investigations.


title: Applications of Super-Energy Tensors

abstract:
  In this contribution I intend to give a summary of the new relevant results
obtained by using the general superenergy tensors. After a quick review of the
definition and properties of these tensors, several of their mathematical and
physical applications are presented. In particular, their interest and
usefulness is mentioned or explicitly analyzed in 1) the study of causal
propagation of general fields; 2) the existence of an infinite number of
conserved quantities in Ricci-flat spacetimes; 3) the different gravitational
theories, such as Einstein's General Relativity or, say, $n=11$ supergravity;
4) the appearance of some scalars possibly related to entropy or quality
factors; 5) the possibility of superenergy exchange between different physical
fields and the appearance of mixed conserved currents.


title: Does General Relativity Require a Metric

abstract:
  The nexus between the gravitational field and the space-time metric was an
essential element in Einstein's development of General Relativity and led him
to his discovery of the field equations for the gravitational field/metric. I
will argue here that the metric is in fact an inessential element of this
theory and can be dispensed with entirely. Its sole function in the theory was
to describe the space-time measurements made by ideal clocks and rods. However,
the behavior of model clocks and measuring rods can be derived directly from
the field equations of General Relativity using the Einstein-Infeld-Hoffmann
(EIH) approiximation procedure. Therefore one does not need to introduce these
ideal clocks and rods and hence has no need of a metric.


title: Integrable models, degenerate horizons and AdS_2 black holes

abstract:
  The near extremal Reissner-Nordstrom black holes in arbitrary dimensions ca
be modeled by the Jackiw-Teitelboim (JT) theory. The asymptotic Virasoro
symmetry of the corresponding JT model exactly reproduces, via Cardy's formula,
the deviation of the Bekenstein-Hawking entropy of the Reissner-Nordstrom black
holes from extremality. We also comment how can we extend this approach to
investigate the evaporation process.


title: Vacuumless cosmic strings in Brans-Dicke theory

abstract:
  The gravitational fields of vacuumless global and gauge strings have been
studied in Brans-Dicke theory under the weak field assumption of the field
equations. It has been shown that both global and gauge string can have
repulsive as well as attractive gravitational effect in Brans-Dicke theory
which is not so in General Relativity.


title: Analysis of relativistic hydrodynamics in conservation form

abstract:
  Formulations of Eulerian general relativistic ideal hydrodynamics in
conservation form are analyzed in some detail, with particular emphasis to
geometric source terms. Simple linear transformations of the equations are
introduced and the associated equivalence class is exploited for the
optimization of such sources. A significant reduction of their complexity is
readily possible in generic spacetimes. The local characteristic structure of
the standard member of the equivalence class is analyzed for a general equation
of state (EOS). This extends previous results restricted to the polytropic
case. The properties of all other members of the class, in particular
specialized forms employing Killing symmetries, are derivable from the standard
form. Special classes of EOS are identified for both spacelike and null
foliations, which lead to explicit inversion of the state vector and
computational savings. The entire approach is equally applicable to spacelike
or lightlike foliations and presents a complete proposal for numerical
relativistic hydrodynamics on stationary or dynamic geometries.


title: Gravitational fields of rotating disks and black holes

abstract:
  The two known exact solutions of Einstein's field equations describing
rotating objects of physical significance - a black hole and a rigidly rotating
disk of dust - are discussed using a single mathematical framework related to
Jacobi's inversion problem. Both solutions can be represented in such a form
that they differ in the choice of a complex parameter and a real solution of
the axisymmetric Laplace equation only. A recently found family of solutions
describing differentially rotating disks of dust fits into the same scheme.


title: Stationary and nonstationary scalar vacuum field noises

abstract:
  If stationary, the spectrum of vacuum field noise (VFN) is an important
ingredient to get information about the curvature invariants of classical
worldlines (relativistic classical trajectories). For scalar quantum field
vacua there are six stationary cases as shown by Letaw some time ago, these are
reviewed here. However, the non-stationary vacuum noises are not out of reach
and can be processed by a few mathematical methods which I briefly comment on.
Since the information about the kinematical curvature invariants of the
worldlines is of radiometric origin, hints are given on a more useful
application to radiation and beam radiometric standards at relativistic
energies


title:
Pendulum Mode Thermal Noise in Advanced Interferometers: A comparison of
  Fused Silica Fibers and Ribbons in the Presence of Surface Loss

abstract:
  The use of fused-silica ribbons as suspensions in gravitational wave
interferometers can result in significant improvements in pendulum mode thermal
noise. Surface loss sets a lower bound to the level of noise achievable, at
what level depends on the dissipation depth and other physical parameters. For
LIGO II, the high breaking strength of pristine fused silica filaments, the
correct choice of ribbon aspect ratio (to minimize thermoelastic damping), and
low dissipation depth combined with the other achievable parameters can reduce
the pendulum mode thermal noise in a ribbon suspension well below the radiation
pressure noise. Despite producing higher levels of pendulum mode thermal noise,
cylindrical fiber suspensions provide an acceptable alternative for LIGO II,
should unforeseen problems with ribbon suspensions arise.


title: Energy-Momentum (Quasi-)Localization for Gravitating Systems

abstract:
  Traditional approaches to energy-momentum localization led to reference frame
dependent pseudotensors. The more modern idea is quasilocal energy-momentum. We
take a Hamiltonian approach. The Hamiltonian boundary term gives not only the
quasilocal values but also boundary conditions via the Hamiltonian variation
boundary principle. Selecting a Hamiltonian boundary term involves several
choices. We found that superpotentials can serve as Hamiltonian boundary terms,
consequently pseudotensors are actually quasilocal and legitimate. Various
Hamiltonian boundary term quasilocal expressions are considered including some
famous pseudotensors, M{\o}ller's tetrad-teleparallel ``tensor'', Chen's
covariant expressions, the expressions of Katz & coworkers, the expression of
Brown & York, and some spinor expressions. We emphasize the need for
identifying criteria for a good choice.


title:
(Quantum) Space-Time as a Statistical Geometry of Lumps in Random
  Networks

abstract:
  In the following we undertake to describe how macroscopic space-time (or
rather, a microscopic protoform of it) is supposed to emerge as a
superstructure of a web of lumps in a stochastic discrete network structure. As
in preceding work (mentioned below), our analysis is based on the working
philosophy that both physics and the corresponding mathematics have to be
genuinely discrete on the primordial (Planck scale) level. This strategy is
concretely implemented in the form of \tit{cellular networks} and \tit{random
graphs}. One of our main themes is the development of the concept of
\tit{physical (proto)points} or \tit{lumps} as densely entangled subcomplexes
of the network and their respective web, establishing something like
\tit{(proto)causality}. It may perhaps be said that certain parts of our
programme are realisations of some early ideas of Menger and more recent ones
sketched by Smolin a couple of years ago. We briefly indicate how this
\tit{two-story-concept} of \tit{quantum} space-time can be used to encode the
(at least in our view) existing non-local aspects of quantum theory without
violating macroscopic space-time causality.


title:
Review of some classical gravitational superenergy tensors using
  computational techniques

abstract:
  We use computational algorithms recently developed by us to study completely
four index divergence free quadratic in Riemann tensor polynomials in GR. Some
results are new and some other reproduce and/or correct known ones. The
algorithms are part of a Mathematica package called Tools of Tensor Calculus
(TTC)[web address: http://baldufa.upc.es/ttc]


title:
The case for cosmic acceleration: Inhomogeneity versus cosmological
  constant

abstract:
  In this work, I develop an alternative explanation for the acceleration of
the cosmic expansion, which seems to be a result of recent high redshift
Supernova data. In the current interpretation, this cosmic acceleration is
explained by including a positive cosmological constant term (or vacuum
energy), in the standard Friedmann models. Instead, I will consider a Locally
Rotationally Symmetric (LRS) and spherically symmetric (SS), but inhomogeneous
spacetime, with a barotropic perfect fluid equation of state for the cosmic
matter. The congruence of matter has acceleration, shear and expansion. Within
this framework the kinematical acceleration of the cosmic fluid or,
equivalently, the inhomogeneity of matter, is just the responsible of the SNe
Ia measured cosmic acceleration. Although in our model the Cosmological
Principle is relaxed, it maintains almost isotropy about our worldline in
agreement with CBR observations.


title: Nondimensional Simplification of Tensor Polynomials with Indices

abstract:
  We are presenting an algorithm capable of simplifying tensor polynomials with
indices when the building tensors have index symmetry properties. These
properties include simple symmetry, cyclicity and those due to the presence of
covariant derivatives. The algorithm is part of a Mathematica package called
Tools of Tensor Calculus (TTC) [web address: http://baldufa.upc.es/ttc]


title:
Quantum Radiation from Black Holes and Naked Singularities in Spherical
  Dust Collapse

abstract:
  A sufficiently massive collapsing star will end its life as a spacetime
singularity. The nature of the Hawking radiation emitted during collapse
depends critically on whether the star's boundary conditions are such as would
lead to the eventual formation of a black hole or, alternatively, to the
formation of a naked singularity. This latter possibility is not excluded by
the singularity theorems. We discuss the nature of the Hawking radiation
emitted in each case. We justify the use of Bogoliubov transforms in the
presence of a Cauchy horizon and show that if spacetime is assumed to terminate
at the Cauchy horizon, the resulting spectrum is thermal, but with a
temperature different from the Hawking temperature.