title: Radiation flux and spectrum in the Vaidya collapse model

abstract:
  We consider the quantization of a massless scalar field, using the geometric
optics approximation, in the background spacetime of a collapsing spherical
self-similar Vaidya star, which forms a black hole or a naked singularity. We
show that the outgoing radiation flux of the quantized scalar field diverges on
the Cauchy horizon. The spectrum of the produced scalar partcles is non-thermal
when the background develops a naked singularity. These results are analogous
to those obtained for the scalar quantization on a self-similar dust cloud.


title: Nonthermal nature of incipient extremal black holes

abstract:
  We examine particle production from spherical bodies collapsing into extremal
Reissner-Nordstr\"om black holes. Kruskal coordinates become ill-defined in the
extremal case, but we are able to find a simple generalization of them that is
good in this limit. The extension allows us to calculate the late-time
worldline of the center of the collapsing star, thus establishing a
correspondence with a uniformly accelerated mirror in Minkowski spacetime. The
spectrum of created particles associated with such uniform acceleration is
nonthermal, indicating that a temperature is not defined. Moreover, the
spectrum contains a constant that depends on the history of the collapsing
object. At first sight this points to a violation of the no-hair theorems;
however, the expectation value of the stress-energy-momentum tensor is zero and
its variance vanishes as a power law at late times. Hence, both the no-hair
theorems and the cosmic censorship conjecture are preserved. The power-law
decay of the variance is in distinction to the exponential fall-off of a
nonextremal black hole. Therefore, although the vanishing of the stress
tensor's expectation value is consistent with a thermal state at zero
temperature, the incipient black hole does not behave as a thermal object at
any time and cannot be regarded as the thermodynamic limit of a nonextremal
black hole, regardless of the fact that the final product of collapse is
quiescent.


title:
Vacuum polarization of scalar fields near Reissner-Nordstr\"{o}m black
  holes and the resonance behavior in field-mass dependence

abstract:
  We study vacuum polarization of quantized massive scalar fields $\phi$ in
equilibrium at black-hole temperature in Reissner-Nordstr\"{o}m background. By
means of the Euclidean space Green's function we analytically derive the
renormalized expression $<\phi^{2}>_{H}$ at the event horizon with the area
$4\pi r_{+}^{2}$. It is confirmed that the polarization amplitude
$<\phi^{2}>_{H}$ is free from any divergence due to the infinite red-shift
effect. Our main purpose is to clarify the dependence of $<\phi^{2}>_{H}$ on
field mass $m$ in relation to the excitation mechanism. It is shown for
small-mass fields with $mr_{+}\ll1$ how the excitation of $<\phi^{2}>_{H}$
caused by finite black-hole temperature is suppressed as $m$ increases, and it
is verified for very massive fields with $mr_{+}\gg1$ that $<\phi^{2}>_{H}$
decreases in proportion to $m^{-2}$ with the amplitude equal to the
DeWitt-Schwinger approximation. In particular, we find a resonance behavior
with a peak amplitude at $mr_{+}\simeq 0.38$ in the field-mass dependence of
vacuum polarization around nearly extreme (low-temperature) black holes. The
difference between Scwarzschild and nearly extreme black holes is discussed in
terms of the mass spectrum of quantum fields dominant near the event horizon.


title: General Relativistic Stars: Linear Equations of State

abstract:
  In this paper Einstein's field equations, for static spherically symmetric
perfect fluid models with a linear barotropic equation of state, are recast
into a 3-dimensional regular system of ordinary differential equations on a
compact state space. The system is analyzed qualitatively, using the theory of
dynamical systems, and numerically. It is shown that certain special solutions
play important roles as building blocks for the solution structure in general.
In particular, these special solutions determine many of the features exhibited
by solutions with a regular center and large central pressure. It is also shown
that the present approach can be applied to more general classes of barotropic
equations of state.


title: General Relativistic Stars : Polytropic Equations of State

abstract:
  In this paper, the gravitational field equations for static spherically
symmetric perfect fluid models with a polytropic equation of state,
$p=k\rho^{1+1/n}$, are recast into two complementary 3-dimensional {\it
regular} systems of ordinary differential equations on compact state spaces.
The systems are analyzed numerically and qualitatively, using the theory of
dynamical systems. Certain key solutions are shown to form building blocks
which, to a large extent, determine the remaining solution structure. In one
formulation, there exists a monotone function that forces the general
relativistic solutions towards a part of the boundary of the state space that
corresponds to the low pressure limit. The solutions on this boundary describe
Newtonian models and thus the relationship to the Newtonian solution space is
clearly displayed. It is numerically demonstrated that general relativistic
models have finite radii when the polytropic index $n$ satisfies $0\leq n
\lesssim 3.339$ and infinite radii when $n\geq 5$. When $3.339\lesssim n<5$,
there exists a 1-parameter set of models with finite radii and a finite number,
depending on $n$, with infinite radii.


title:
Relational evolution of the degrees of freedom of generally covariant
  quantum theories

abstract:
  We study the classical and quantum dynamics of generally covariant theories
with vanishing a Hamiltonian and with a finite number of degrees of freedom. In
particular, the geometric meaning of the full solution of the relational
evolution of the degrees of freedom is displayed, which means the determination
of the total number of evolving constants of motion required. Also a method to
find evolving constants is proposed. The generalized Heinsenberg picture needs
M time variables, as opposed to the Heisenberg picture of standard quantum
mechanics where one time variable t is enough. As an application, we study the
parameterized harmonic oscillator and the SL(2,R) model with one physical
degree of freedom that mimics the constraint structure of general relativity
where a Schrodinger equation emerges in its quantum dynamics.


title:
Statistical mechanics of generally covariant quantum theories: A
  Boltzmann-like approach

abstract:
  We study the possibility of applying statistical mechanics to generally
covariant quantum theories with a vanishing Hamiltonian. We show that (under
certain appropiate conditions) this makes sense, in spite of the absence of a
notion of energy and external time. We consider a composite system formed by a
large number of identical components, and apply Boltzmann's ideas and the
fundamental postulates of ordinary statistical physics. The thermodynamical
parameters are determined by the properties of the thermalizing interaction. We
apply these ideas to a simple example, in which the component system has one
physical degree of freedom and mimics the constraint algebra of general
relativity.


title: Exact plane gravitational waves and electromagnetic fields

abstract:
  The behaviour of a "test" electromagnetic field in the background of an exact
gravitational plane wave is investigated in the framework of Einstein's general
relativity. We have expressed the general solution to the de Rham equations as
a Fourier-like integral. In the general case we have reduced the problem to a
set of ordinary differential equations and have explicitly written the solution
in the case of linear polarization of the gravitational wave. We have expressed
our results by means of Fermi Normal Coordinates (FNC), which define the proper
reference frame of the laboratory. Moreover we have provided some "gedanken
experiments", showing that an external gravitational wave induces measurable
effects of non tidal nature via electromagnetic interaction. Consequently it is
not possible to eliminate gravitational effects on electromagnetic field, even
in an arbitrarily small spatial region around an observer freely falling in the
field of a gravitational wave. This is opposite to the case of mechanical
interaction involving measurements of geodesic deviation effects. This
behaviour is not in contrast with the principle of equivalence, which applies
to arbitrarily small region of both space and time.


title: Some integrals ocurring in a topology change problem

abstract:
  In a paper presented a few years ago, De Lorenci et al. showed, in the
context of canonical quantum cosmology, a model which allowed space topology
changes (Phys. Rev. D 56, 3329 (1997)). The purpose of this present work is to
go a step further in that model, by performing some calculations only estimated
there for several compact manifolds of constant negative curvature, such as the
Weeks and Thurston spaces and the icosahedral hyperbolic space (Best space).


title:
Matters of Gravity, the newsletter of the APS Topical Group on
  Gravitation

abstract:
  News:
  TGG session in the April meeting, by Cliff Will NRC report, by Beverly Berger
MG9 Travel Grant for US researchers, by Jim Isenberg Research Briefs:
  How many coalescing binaries are there?, by Vicky Kalogera Recent
developments in black critical phenomena, by Pat Brady Optical black holes?, by
Matt Visser ``Branification:'' an alternative to compactification, by Steve
Giddings Searches for non-Newtonian Gravity at Sub-mm Distances, by Riley
Newman Quiescent cosmological singularities by Bernd Schmidt The debut of LIGO
II, by David Shoemaker Is the universe still accelerating?, by Sean Carroll
Conference reports:
  Journ\' ees Relativistes Weimar 1999, by Volker Perlick The 9th Midwest
Relativity Meeting, by Thomas Baumgarte


title:
On 4-dimensional cosmological models locally embedded in a 5-dimensional
  Ricci-flat space

abstract:
  We employ a theorem due to Campbell to build some simple 4-dimensional
cosmological models which originate from solutions describing waves propagating
along the extra-dimension of a 5-dimensional Ricci-flat space. The dimensional
reduction is performed in the Jordan frame according to the induced-matter
theory of Wesson.


title: Evolution of the Quantum Friedmann Universe Featuring Radiation

abstract:
  The classical and quantum models of the Friedmann universe originally filled
with a scalar field and radiation have been studied. The radiation has been
used to specify a reference frame that makes it possible to remove ambiguities
in choosing the time coordinate. Solutions to the Einstein and Schroedinger
equations have been studied under the assumption that the rate of scalar-field
variation is much less than the rate of universe expansion (contraction). It
has been shown that, under certain conditions, the quantum universe can be in
quasistationary states. The probability that the universe goes over to states
with large quantum numbers owing to the interaction of the scalar and
gravitational fields is nonzero. It has been shown that, in the lowest state,
the scale factor is on order of the Planck length. The matter- and
radiation-energy densities in the Planck era have been computed. The possible
scenarios of Universe evolution are discussed.


title: Highly Excited Friedmann Universe

abstract:
  A highly excited Friedmann universe filled with a scalar field and radiation
has been considered. On the basis of a direct solution to the
quantum-mechanical problem with a well-defined time variable, it has been shown
that such a universe can have features (energy density, scale factor, Hubble
constant, density parameter, matter mass, equivalent number of baryons, age,
dimensions of large-scale fluctuations, amplitude of fluctuations of cosmic
microwave background radiation temperature) identical to those of the currently
observed Universe.


title: SU(2) Cosmological Solitons

abstract:
  We present a class of numerical solutions to the SU(2) nonlinear
$\sigma$-model coupled to the Einstein equations with cosmological constant
$\Lambda\geq 0$ in spherical symmetry. These solutions are characterized by the
presence of a regular static region which includes a center of symmetry. They
are parameterized by a dimensionless ``coupling constant'' $\beta$, the sign of
the cosmological constant, and an integer ``excitation number'' $n$. The
phenomenology we find is compared to the corresponding solutions found for the
Einstein-Yang-Mills (EYM) equations with positive $\Lambda$ (EYM$\Lambda$). If
we choose $\Lambda$ positive and fix $n$, we find a family of static spacetimes
with a Killing horizon for $0 \leq \beta < \beta_{max}$. As a limiting solution
for $\beta = \beta_{max}$ we find a {\em globally} static spacetime with
$\Lambda=0$, the lowest excitation being the Einstein static universe. To
interpret the physical significance of the Killing horizon in the cosmological
context, we apply the concept of a trapping horizon as formulated by Hayward.
For small values of $\beta$ an asymptotically de Sitter dynamic region contains
the static region within a Killing horizon of cosmological type. For strong
coupling the static region contains an ``eternal cosmological black hole''.


title: Small-eccentricity binary pulsars and relativistic gravity

abstract:
  Small-eccentricity binary pulsars with white dwarf companions provide
excellent test laboratories for various effects predicted by alternative
theories of gravity, in particular tests for the emission of gravitational
dipole radiation and the existence of gravitational Stark effects. We will
present new limits to these effects. The statistical analysis presented here,
for the first time, takes appropriately care of selection effects.


title: A Theory of Quantum Gravity from First Principles

abstract:
  When quantum fields are studied on manifolds with boundary, the corresponding
one-loop quantum theory for bosonic gauge fields with linear covariant gauges
needs the assignment of suitable boundary conditions for elliptic differential
operators of Laplace type. There are however deep reasons to modify such a
scheme and allow for pseudo-differential boundary-value problems. When the
boundary operator is allowed to be pseudo-differential while remaining a
projector, the conditions on its kernel leading to strong ellipticity of the
boundary-value problem are studied in detail. This makes it possible to develop
a theory of one-loop quantum gravity from first principles only, i.e. the
physical principle of invariance under infinitesimal diffeomorphisms and the
mathematical requirement of a strongly elliptic theory.


title: On existence of mini-boson stars

abstract:
  We prove the existence of a countable family of globally regular solutions of
spherically symmetric Einstein-Klein-Gordon equations. These solutions, known
as mini-boson stars, were discovered numerically many years ago.


title: Relic Gravitational Waves and Their Detection

abstract:
  The range of expected amplitudes and spectral slopes of relic (squeezed)
gravitational waves, predicted by theory and partially supported by
observations, is within the reach of sensitive gravity-wave detectors. In the
most favorable case, the detection of relic gravitational waves can be achieved
by the cross-correlation of outputs of the initial laser interferometers in
LIGO, VIRGO, GEO600. In the more realistic case, the sensitivity of advanced
ground-based and space-based laser interferometers will be needed. The specific
statistical signature of relic gravitational waves, associated with the
phenomenon of squeezing, is a potential reserve for further improvement of the
signal to noise ratio.


title: Electromagnetic waves in a wormhole geometry

abstract:
  We investigate the propagation of electromagnetic waves through a static
wormhole. It is shown that the problem can be reduced to a one-dimensional
Schr\"odinger-like equation with a barrier-type potential. Using numerical
methods, we calculate the transmission coefficient as a function of the energy.
We also discuss the polarization of the outgoing radiation due to this
gravitational scattering.


title: On Schwarzschild-Like Solutions in Curvature-Quadratic Gravity

abstract:
  Partial results are obtained for Schwarzschild- like solutions in a gravity
theory with action density (-g)^(1/2)[Rik^2+bR^2]. A seven parameter family of
implicit solutions is found. A number of explicit solutions are also exhibited.


title: Weinberg's energy-momentum pseudotensor for Schwarzschild field

abstract:
  Weinberg's energy-momentum pseudotensor is obtained for Schwarzschild metric
in harmonic coordinates. On the horizon it possesses unintegrable
singularities. For this reason the total energy of a collapsar can't be
obtained by integrating energy density over the system's volume. The
implication for gravity theories is noted. A thought on how to choose unique
energy-momentum tensor is given.


title:
Warm inflation with coupled thermal quantum fluctuations: a new
  semiclassical approach

abstract:
  I consider a new semiclassical expansion for the inflaton field in the
framework of warm inflation scenario. The fluctuations of the matter field are
considered as thermally coupled with the particles of the thermal bath. This
coupling parameter depends on the temperature of the bath. The power spectrum
remains invariant under this new semiclassical expansion for the inflaton.
However, I find that the thermal component of the amplitude for the primordial
field fluctuations should be very small at the end of inflation.


title: Logarithmic correction to the Bekenstein-Hawking entropy

abstract:
  The exact formula derived by us earlier for the entropy of a four dimensional
non-rotating black hole within the quantum geometry formulation of the event
horizon in terms of boundary states of a three dimensional Chern-Simons theory,
is reexamined for large horizon areas. In addition to the {\it semiclassical}
Bekenstein-Hawking contribution to the area obtained earlier, we find a
contribution proportional to the logarithm of the area together with subleading
corrections that constitute a series in inverse powers of the area.


title: A new singularity theorem in relativistic cosmology

abstract:
  It is shown that if the timelike eigenvector of the Ricci tensor be
hypersurface orthogonal so that the space time allows a foliation into space
sections then the space average of each of the scalar that appear in the
Raychaudhuri equation vanishes provided the strong energy condition holds good.
This result is presented in the form of a singularity theorem.


title: Are Simple Real Pole Solutions Physical?

abstract:
  We consider exact solutions generated by the inverse scattering technique,
also known as the soliton transformation. In particular, we study the class of
simple real pole solutions. For quite some time, those solutions have been
considered interesting as models of cosmological shock waves. A coordinate
singularity on the wave fronts was removed by a transformation which induces a
null fluid with negative energy density on the wave front. This null fluid is
usually seen as another coordinate artifact, since there seems to be a general
belief that that this kind of solution can be seen as the real pole limit of
the smooth solution generated with a pair of complex conjugate poles in the
transformation. We perform this limit explicitly, and find that the belief is
unfounded: two coalescing complex conjugate poles cannot yield a solution with
one real pole. Instead, the two complex conjugate poles go to a different
limit, what we call a ``pole on a pole''. The limiting procedure is not unique;
it is sensitive to how quickly some parameters approach zero. We also show that
there exists no improved coordinate transformation which would remove the
negative energy density. We conclude that negative energy is an intrinsic part
of this class of solutions.


title:
Computing radiation from Kerr black holes: Generalization of the
  Sasaki-Nakamura equation

abstract:
  As shown by Teukolsky, the master equation governing the propagation of weak
radiation in a black hole spacetime can be separated into four ordinary
differential equations, one for each spacetime coordinate. (``Weak'' means the
radiation's amplitude is small enough that its own gravitation may be
neglected.) Unfortunately, it is difficult to accurately compute solutions to
the separated radial equation (the Teukolsky equation), particularly in a
numerical implementation. The fundamental reason for this is that the Teukolsky
equation's potentials are long ranged. For non-spinning black holes, one can
get around this difficulty by applying transformations which relate the
Teukolsky solution to solutions of the Regge-Wheeler equation, which has a
short-ranged potential. A particularly attractive generalization of this
approach to spinning black holes for gravitational radiation (spin weight s =
-2) was given by Sasaki and Nakamura. In this paper, I generalize Sasaki and
Nakamura's results to encompass radiation fields of arbitrary integer spin
weight, and give results directly applicable to scalar (s = 0) and
electromagnetic (s = -1) radiation. These results may be of interest for
studies of astrophysical radiation processes near black holes, and of programs
to compute radiation reaction forces in curved spacetime.


title: Gravitational Collapse of Dust with a Cosmological Constant

abstract:
  The recent analysis of Markovic and Shapiro on the effect of a cosmological
constant on the evolution of a spherically symmetric homogeneous dust ball is
extended to include the inhomogeneous and degenerate cases. The histories are
shown by way of effective potential and Penrose-Carter diagrams.


title: Compact stellar objects with multiple neck optical geometries

abstract:
  Ultra compact stellar models with a two-zone uniform density equation of
state are considered. They are shown to provide neat examples of optical
geometries exhibiting double necks, implying that the gravitational wave
potential has a double well structure.


title: Inertia in the Structure of Four-dimensional Space

abstract:
  1. Following Rimman, Minkowski and Einstein, for the first time equations of
the inert filed in the covariant form are found geometrically. 2.In the
approximation of a weak field for the first time the Law of Inertia in a
material space (as opposed to the absolute space) is received. A consequence is
the formulation of Mach's principle. 3. Analogous to Einstein's expression for
the gravitational field, Compton's formula is received for the inert field. 4.
For the first time transcendental equations are received, one of the solutions
of which corresponds to the value of the magnetic charge by Dirack, or to the
constant of fine structure.


title: Peeling properties of lightlike signals in General Relativity

abstract:
  The peeling properties of a lightlike signal propagating through a general
Bondi-Sachs vacuum spacetime and leaving behind another Bondi-Sachs vacuum
space-time are studied. We demonstrate that in general the peeling behavior is
the conventional one which is associated with a radiating isolated system and
that it becomes unconventional if the asymptotically flat space-times on either
side of the history of the light-like signal tend to flatness at future null
infinity faster than the general Bondi-Sachs space-time. This latter situation
occurs if, for example, the space-times in question are static Bondi-Sachs
space- times.


title: Colliding Plane Impulsive Gravitational Waves

abstract:
  When two non-interacting plane impulsive gravitational waves undergo a
head-on collision, the vacuum interaction region between the waves after the
collision contains backscattered gravitational radiation from both waves. The
two systems of backscattered waves have each got a family of rays (null
geodesics) associated with them. We demonstrate that if it is assumed that a
parameter exists along each of these families of rays such that the modulus of
the complex shear of each is equal then Einstein's vacuum field equations, with
the appropriate boundary conditions, can be integrated systematically to reveal
the well-known solutions in the interaction region. In so doing the mystery
behind the origin of such solutions is removed. With the use of the field
equations it is suggested that the assumption leading to their integration may
be interpreted physically as implying that the energy densities of the two
backscattered radiation fields are equal. With the use of different boundary
conditions this approach can lead to new collision solutions.


title:
Proof of a generalized Geroch conjecture for the hyperbolic Ernst
  equation

abstract:
  We enunciate and prove here a generalization of Geroch's famous conjecture
concerning analytic solutions of the elliptic Ernst equation. Our
generalization is stated for solutions of the hyperbolic Ernst equation that
are not necessarily analytic, although it can be formulated also for solutions
of the elliptic Ernst equation that are nowhere axis-accessible.


title: Acoustics of early universe. I. Flat versus open universe models

abstract:
  A simple perturbation description unique for all signs of curvature, and
based on the gauge-invariant formalisms is proposed to demonstrate that:
  (1) The density perturbations propagate in the flat radiation-dominated
universe in exactly the same way as electromagnetic or gravitational waves
propagate in the epoch of the matter domination.
  (2) In the open universe, sounds are dispersed by curvature. The space
curvature defines the minimal frequency $\omega_{\rm c}$ below which the
propagation of perturbations is forbidden.
  Gaussian acoustic fields are considered and the curvature imprint in the
perturbations spectrum is discussed.


title: Acoustics of early universe. II. Lifshitz vs. gauge-invariant theories

abstract:
  Appealing to classical methods of order reduction, we reduce the Lifshitz
system to a second order differential equation. We demonstrate its equivalence
to well known gauge-invariant results. For a radiation dominated universe we
express the metric and density corrections in their exact forms and discuss
their acoustic character.


title:
The gauge factor increase and the hypothetical emerging of the matter
  objects on the horizon in the standard model of universe

abstract:
  In the standard model of universe the increase in mass of our observed
expansive and isotropic relativistic Universe is explained by the hypothetical
assumption of matter objects emerging on the horizon (of the most remote
visibility). However, the mathematical-physical analysis of the increase of
Universe gauge factor shows that this hypothetical assumption is non-compatible
with the variants of the standard model of universe by which - according to the
standard model of universe - can be described the expansive evolution of the
Universe.


title:
Statistical Lorentzian geometry and the closeness of Lorentzian
  manifolds

abstract:
  I introduce a family of closeness functions between causal Lorentzian
geometries of finite volume and arbitrary underlying topology. When points are
randomly scattered in a Lorentzian manifold, with uniform density according to
the volume element, some information on the topology and metric is encoded in
the partial order that the causal structure induces among those points; one can
then define closeness between Lorentzian geometries by comparing the sets of
probabilities they give for obtaining the same posets. If the density of points
is finite, one gets a pseudo-distance, which only compares the manifolds down
to a finite volume scale, as illustrated here by a fully worked out example of
two 2-dimensional manifolds of different topology; if the density is allowed to
become infinite, a true distance can be defined on the space of all Lorentzian
geometries. The introductory and concluding sections include some remarks on
the motivation for this definition and its applications to quantum gravity.


title: Current-Carrying Cosmic Strings in Scalar-Tensor Gravities

abstract:
  We study the modifications on the metric of an isolated self-gravitating
bosonic superconducting cosmic string in a scalar-tensor gravity in the
weak-field approximation. These modifications are induced by an arbitrary
coupling of a massless scalar field to the usual tensorial field in the
gravitational Lagrangian. The metric is derived by means of a matching at the
string radius with a most general static and cylindrically symmetric solution
of the Einstein-Maxwell-scalar field equations. We show that this metric
depends on five parameters which are related to the string's internal structure
and to the solution of the scalar field. We compare our results with those
obtained in the framework of General Relativity.


title:
Thermoelastic Noise and Homogeneous Thermal Noise in Finite Sized
  Gravitational-Wave Test Masses

abstract:
  An analysis is given of thermoelastic noise (thermal noise due to
thermoelastic dissipation) in finite sized test masses of laser interferometer
gravitational-wave detectors. Finite-size effects increase the thermoelastic
noise by a modest amount; for example, for the sapphire test masses tentatively
planned for LIGO-II and plausible beam-spot radii, the increase is less than or
of order 10 per cent. As a side issue, errors are pointed out in the currently
used formulas for conventional, homogeneous thermal noise (noise associated
with dissipation which is homogeneous and described by an imaginary part of the
Young's modulus) in finite sized test masses. Correction of these errors
increases the homogeneous thermal noise by less than or of order 5 per cent for
LIGO-II-type configurations.


title: Large quantum gravity effects: Cylindrical waves in four dimensions

abstract:
  Linearly polarized cylindrical waves in four-dimensional vacuum gravity are
mathematically equivalent to rotationally symmetric gravity coupled to a
Maxwell (or Klein-Gordon) field in three dimensions. The quantization of this
latter system was performed by Ashtekar and Pierri in a recent work. Employing
that quantization, we obtain here a complete quantum theory which describes the
four-dimensional geometry of the Einstein-Rosen waves. In particular, we
construct regularized operators to represent the metric. It is shown that the
results achieved by Ashtekar about the existence of important quantum gravity
effects in the Einstein-Maxwell system at large distances from the symmetry
axis continue to be valid from a four-dimensional point of view. The only
significant difference is that, in order to admit an approximate classical
description in the asymptotic region, states that are coherent in the Maxwell
field need not contain a large number of photons anymore. We also analyze the
metric fluctuations on the symmetry axis and argue that they are generally
relevant for all of the coherent states.


title:
Cauchy-characteristic matching for a family of cylindrical vacuum
  solutions possessing both gravitational degrees of freedom

abstract:
  This paper is part of a long term program to Cauchy-characteristic matching
(CCM) codes as investigative tools in numerical relativity. The approach has
two distinct features: (i) it dispenses with an outer boundary condition and
replaces this with matching conditions at an interface between the Cauchy and
characteristic regions, and (ii) by employing a compactified coordinate, it
proves possible to generate global solutions. In this paper CCM is applied to
an exact two-parameter family of cylindrically symmetric vacuum solutions
possessing both gravitational degrees of freedom due to Piran, Safier and Katz.
This requires a modification of the previously constructed CCM cylindrical code
because, even after using Geroch decomposition to factor out the $z$-direction,
the family is not asymptotically flat. The key equations in the characteristic
regime turn out to be regular singular in nature.


title: Conformal invariance and particle aspects in general relativity

abstract:
  We study the breakdown of conformal symmetry in a conformally invariant
gravitational model. The symmetry breaking is introduced by defining a
preferred conformal frame in terms of the large scale characteristics of the
universe. In this context we show that a local change of the preferred
conformal frame results in a Hamilton-Jacobi equation describing a particle
with adjustable mass. In this equation the dynamical characteristics of the
particle substantially depends on the applied conformal factor and local
geometry. Relevant interpretations of the results are also discussed.


title:
Hamiltonian formulation of general relativity in the teleparallel
  geometry

abstract:
  We establish the Hamiltonian formulation of the teleparallel equivalent of
general relativity, without fixing the time gauge condition, by rigorously
performing the Legendre transform. The time gauge condition, previously
considered, restricts the teleparallel geometry to the three-dimensional
spacelike hypersurface. Geometrically, the teleparallel geometry is now
extended to the four-dimensional space-time. The resulting Hamiltonian
formulation is different from the standard ADM formulation in many aspects, the
main one being that the dynamics is now governed by the Hamiltonian constraint
H_0 and a set of primary constraints. The vector constraint H_i is derived from
the Hamiltonian constraint. The vanishing of the latter implies the vanishing
of the vector constraint.


title:
Hamiltonian formulation of teleparallel theories of gravity in the time
  gauge

abstract:
  We consider the most general class of teleparallel theories of gravity
quadratic in the torsion tensor, and carry out a detailed investigation of its
Hamiltonian formulation in the time gauge. Such general class is given by a
three-parameter family of theories. A consistent implementation of the Legendre
transform reduces the original theory to a one-parameter theory determined in
terms of first class constraints. The free parameter is fixed by requiring the
Newtonian limit. The resulting theory is the teleparallel equivalent of general
relativity.


title:
Metric Unification of Gravitation and Electromagnetism Solves the
  Cosmological Constant Problem

abstract:
  We first review the cosmological constant problem, and then mention a
conjecture of Feynman according to which the general relativistic theory of
gravity should be reformulated in such a way that energy does not couple to
gravity. We point out that our recent unification of gravitation and
electromagnetism through a symmetric tensor has the property that the free
electromagnetic energy and the vacuum energy do not contribute explicitly to
the curvature of spacetime just like the free gravitational energy. Therefore
in this formulation of general relativity, the vacuum energy density has its
very large value today as in the early universe, while the cosmological
constant does not exist at all.


title: Initial data and spherical dust collapse

abstract:
  By considering families of radial null geodesics, we study the subsets of
initial data that lead to naked singularities and black holes in inhomogeneous
spherical dust collapse. We introduce the notion of central homogeneity for
spherical dust collapse and prove that for the occurrence of naked
singularities, the initial data set must in general be centrally homogeneous.
Even though mathematically this indicates that naked singularities are in
general unstable, we show that centrally inhomogeneous perturbations in the
initial data are not physically reasonable. This provides an example of the
fact that instability in this context deduced with respect to general
perturbations can become stabilised once the class of perturbations are
restricted to be physical.


title: The dynamics of curved gravitating walls

abstract:
  We examine the dynamics of a self-gravitating domain wall using the $\lambda
\Phi^4$ model as a specific example. We find that the Nambu motion of the wall
is quite generic and dominates the wall motion even in the presence of gravity.
We calculate the corrections to this leading order motion, and estimate the
effect of the inclusion of gravity on the dynamics of the wall. We then treat
the case of a spherical gravitating thick wall as a particular example, solving
the field equations and calculating the corrections to the Nambu motion
analytically for this specific case. We find that the presence of gravity
retards collapse in this case.


title: Symmetries of asymptotically flat axisymmetric spacetimes with null dust

abstract:
  Symmetries of spacetimes with null dust field as a source compatible with
asymptotic flatness are studied by using the Bondi-Sachs-van der Burg
formalism. It is shown that in an axially symmetric spacetime with null dust
field in which at least locally a smooth null infinity in the sense of Penrose
exists, the only allowable additional Killing vector forming with the axial one
a two-dimensional Lie algebra (the axial and the additional Killing vector are
not assumed to be hypersurface orthogonal) is a supertranslational Killing
vector and the gravitational field is then non-radiative (the Weyl tensor has a
non-radiative character).


title: Gravity Quanta, Entropy and Black Holes

abstract:
  We propose the use of a gravitational uncertainty principle for gravitation.
We define the corresponding gravitational Planck's constant and the
gravitational quantum of mass. We define entropy in terms of the quantum of
gravity with the property of having an extensive quality. The equivalent 2nd
law of thermodynamics is derived, the entropy increasing linearly with
cosmological time. These concepts are applied to the case of black holes,
finding their entropy and discussing their radiation.


title: Some Remarks on the Neutrino Oscillation Phase in a Gravitational Field

abstract:
  The weak gravitational field expansion method to account for the
gravitationally induced neutrino oscillation effect is critically examined. It
is shown that the splitting of the neutrino phase into a ``kinematic'' and a
``gravitational'' phase is not always possible because the relativistic factor
modifies the particle interference phase splitting condition in a gravitational
field.


title: Type II Critical Collapse of a Self-Gravitating Nonlinear $\sigma$-Model

abstract:
  We report on the existence and phenomenology of type II critical collapse
within the one-parameter family of SU(2) $\sigma$-models coupled to gravity.
Numerical investigations in spherical symmetry show discretely self-similar
(DSS) behavior at the threshold of black hole formation for values of the
dimensionless coupling constant $\ccbeta$ ranging from 0.2 to 100; at 0.18 we
see small deviations from DSS. While the echoing period $\Delta$ of the
critical solution rises sharply towards the lower limit of this range, the
characteristic mass scaling has a critical exponent $\gamma$ which is almost
independent of $\ccbeta$, asymptoting to $0.1185 \pm 0.0005$ at large
$\ccbeta$. We also find critical scaling of the scalar curvature for
near-critical initial data. Our numerical results are based on an
outgoing-null-cone formulation of the Einstein-matter equations, specialized to
spherical symmetry. Our numerically computed initial-data critical parameters
$p^*$ show 2nd order convergence with the grid resolution, and after
compensating for this variation in $p^*$, our individual evolutions are
uniformly 2nd order convergent even very close to criticality.


title: On the triviality of certain non-Riemannian models of gravitation

abstract:
  We prove in the Tucker-Wang approach to non-Riemannian Gravity that a general
homogeneous Lagrangian density in the general connection with order of
homogeneity of at least two, gives no contribution to the generalised Einstein
equations. Using this result other important cases are also considered.


title: The Case for Inertia as a Vacuum Effect: A Reply to Woodward and Mahood

abstract:
  The possibility of an extrinsic origin for inertial reaction forces has
recently seen increased attention in the physical literature. Among theories of
extrinsic inertia, the two considered by the current work are (1) the
hypothesis that inertia is a result of gravitational interactions, and (2) the
hypothesis that inertial reaction forces arise from the interaction of material
particles with local fluctuations of the quantum vacuum. A recent article
supporting the former and criticizing the latter is shown to contain
substantial errors.


title:
Normal modes of relativistic systems in post-Newtonian approximation and
  the stability curve of r-modes

abstract:
  In part I, we use the post-Newtonian (pn) order of Liouville's equation to
study the normal modes of oscillation of a spherically symmetric relativistic
system. Perturbations that are neutral in Newtonian approximation develop into
a new sequence of normal modes.
  In part II, stability curve of r-modes of neutron stars are calculated by
considering vorticity-shear viscosity coupling.
  As an application, the loss of angular momentum through gravitational
radiation, driven by the excitation of r-modes, is considered in neutron stars
having rotation frequencies smaller than the associated critical frequency.


title: Open universes and avoidance of the cosmological singularity

abstract:
  In the present paper we give conclusive arguments pointing at physical
equivalence among conformally related metrics. Based on the argument that any
consistent effective theory of spacetime must be invariant under the
one-parameter group of transformations of the units of length, time and
reciprocal mass, it is shown, also, that canonical general relativity is not
such a consistent theory. Conformal general relativity provides a consistent
formulation of the laws of gravity instead. We further extend the results of
papers gr-qc/9908075 and gr-qc/9905071 to open universes by studying the
Raychaudhuri equation.


title:
Low-energy sector quantization of a massless scalar field outside a
  Reissner-Nordstrom black hole and static sources

abstract:
  We quantize the low-energy sector of a massless scalar field in the
Reissner-Nordstrom spacetime. This allows the analysis of processes involving
soft scalar particles occurring outside charged black holes. In particular, we
compute the response of a static scalar source interacting with Hawking
radiation using the Unruh (and the Hartle-Hawking) vacuum. This response is
compared with the one obtained when the source is uniformly accelerated in the
usual vacuum of the Minkowski spacetime with the same proper acceleration. We
show that both responses are in general different in opposition to the result
obtained when the Reissner-Nordstrom black hole is replaced by a Schwarzschild
one. The conceptual relevance of this result is commented.


title:
(^-L_n,g)-spaces. Length of a vector field and the angle between two
  vector fields

abstract:
  The notions of length of a vector field and cosine of the angle between two
vector fields over a differentiable manifold with contravariant and covariant
affine connections and metrics are introduced and considered. The change of the
length of a vector field and of the angle between two vector fields along a
contravariant vector field are found. The introduced notions are necessary for
investigations of different types of transports over a manifold of the above
mentioned type.


title: The Cauchy Problem for the Einstein Equations

abstract:
  Various aspects of the Cauchy problem for the Einstein equations are
surveyed, with the emphasis on local solutions of the evolution equations.
Particular attention is payed to giving a clear explanation of conceptual
issues which arise in this context. The question of producing reduced systems
of equations which are hyperbolic is examined in detail and some new results on
that subject are presented. Relevant background from the theory of partial
differential equations is also explained at some length


title: On the experimental foundations of the Maxwell equations

abstract:
  We begin by reviewing the derivation of generalized Maxwell equations from an
operational definition of the electromagnetic field and the most basic notions
of what constitutes a dynamical field theory. These equations encompass the
familiar Maxwell equations as a special case but, in other cases, can predict
birefringence, charge non-conservation, wave damping and other effects that the
familiar Maxwell equations do not. It follows that observational constraints on
such effects can restrict the dynamics of the electromagnetic field to be very
like the familiar Maxwellian dynamics, thus, providing an empirical foundation
for the Maxwell equations. We discuss some specific observational results that
contribute to that foundation.


title: Locating Boosted Kerr and Schwarzschild Apparent Horizons

abstract:
  We describe a finite-difference method for locating apparent horizons and
illustrate its capabilities on boosted Kerr and Schwarzschild black holes. Our
model spacetime is given by the Kerr-Schild metric. We apply a Lorentz boost to
this spacetime metric and then carry out a 3+1 decomposition. The result is a
slicing of Kerr/Schwarzschild in which the black hole is propagated and Lorentz
contracted. We show that our method can locate distorted apparent horizons
efficiently and accurately.


title: Shell sources as a probe of relativistic effects in neutron star models

abstract:
  A perturbing shell is introduced as a device for studying the excitation of
fluid motions in relativistic stellar models. We show that this approach allows
a reasonably clean separation of radiation from the shell and from fluid
motions in the star, and provides broad flexibility in the location and
timescale of perturbations driving the fluid motions. With this model we
compare the relativistic and Newtonian results for the generation of even
parity gravitational waves from constant density models. Our results suggest
that relativistic effects will not be important in computations of the
gravitational emission except possibly in the case of excitation of the neutron
star on very short time scales.


title:
Einstein-Yang-Mills Isolated Horizons: Phase Space, Mechanics, Hair and
  Conjectures

abstract:
  The concept of "Isolated Horizon" has been recently used to provide a full
Hamiltonian treatment of black holes. It has been applied successfully to the
cases of {\it non-rotating}, {\it non-distorted} black holes in Einstein
Vacuum, Einstein-Maxwell and Einstein-Maxwell-Dilaton Theories. In this note,
it is investigated the extent to which the framework can be generalized to the
case of non-Abelian gauge theories where `hairy black holes' are known to
exist. It is found that this extension is indeed possible, despite the fact
that in general, there is no `canonical normalization' yielding a preferred
Horizon Mass. In particular the zeroth and first laws are established for all
normalizations. Colored static spherically symmetric black hole solutions to
the Einstein-Yang-Mills equations are considered from this perspective. A
canonical formula for the Horizon Mass of such black holes is found. This
analysis is used to obtain nontrivial relations between the masses of the
colored black holes and the regular solitonic solutions in Einstein-Yang-Mills
theory. A general testing bed for the instability of hairy black holes in
general non-linear theories is suggested. As an example, the embedded Abelian
magnetic solutions are considered. It is shown that, within this framework, the
total energy is also positive and thus, the solutions are potentially unstable.
Finally, it is discussed which elements would be needed to place the Isolated
Horizons framework for Einstein-Yang-Mills theory in the same footing as the
previously analyzed cases. Motivated by these considerations and using the fact
that the Isolated Horizons framework seems to be the appropriate language to
state uniqueness and completeness conjectures for the EYM equations --in terms
of the horizon charges--, two such conjectures are put forward.


title: Gravitational Waves from Relativistic Stars

abstract:
  Stellar pulsations in rotating relativistic stars are reviewed. Slow rotation
approximation is applied to solving the Einstein equations. The rotational
effects on the non-axisymmetric oscillations are explicitly shown in the polar
and axial modes.


title:
Birth of the Universe as anti-tunnelling from the string perturbative
  vacuum

abstract:
  The decay of the string perturbative vacuum, if triggered by a suitable,
duality-breaking dilaton potential, can efficiently proceed via the parametric
amplification of the Wheeler-De Witt wave function in superspace, and can
appropriately describe the birth of our Universe as a quantum process of pair
production from the vacuum.


title: Is gravity inherent to relativistic many-particle systems?

abstract:
  This paper discusses the somewhat unintuitive conjecture that many
Lorentz-invariant many-particle models can be reinterpreted to satisfy the gtr
field equations. It is shown that a careful remapping of coordinates yields a
non-trivial Riemannian manifold. Furthermore an energy-momentum tensor is
outlined and it is argued that it may converge to its classical counterpart in
the macroscopic limit. These ideas could possibly be used to partially relieve
us of some the resilient problems of adding spacetime curvature to modern QM
theories.


title:
Effect of latent mass in inhomogeneous cosmological model with perfect
  fluid and self-acting scalar field

abstract:
  The inhomogeneous cosmological model with matter in the form self-acting
scalar field and perfect fluid is considered. On the basis of exact solutions
is considered the evolution of density distribution of a matter in space on a
background cosmological expansion by the Universe. Is shown, the first, in such
model the equation of a matter state is variable in time and is closely
connected to character cosmological expansions. Secondly, it is shown with
point of view of the observer the Universe looks as space flat, but with effect
of latent mass. This effect consists in that the mass of a perfect fluid by
dynamic measurements surpasses the own mass perfect fluid that is explained by
presence scalar field (20K).


title: Spin foams as Feynman diagrams

abstract:
  It has been recently shown that a certain non-topological spin foam model can
be obtained from the Feynman expansion of a field theory over a group. The
field theory defines a natural ``sum over triangulations'', which removes the
cut off on the number of degrees of freedom and restores full covariance. The
resulting formulation is completely background independent: spacetime emerges
as a Feynman diagram, as it did in the old two-dimensional matrix models. We
show here that any spin foam model can be obtained from a field theory in this
manner. We give the explicit form of the field theory action for an arbitrary
spin foam model. In this way, any model can be naturally extended to a sum over
triangulations. More precisely, it is extended to a sum over 2-complexes.


title:
Simplicial minisuperspace models in the presence of a massive scalar
  field with arbitrary scalar coupling

abstract:
  We extend previous simplicial minisuperspace models to account for arbitrary
scalar coupling \eta R\phi^2.


title: P-brane black holes for general intersections

abstract:
  Black hole generalized p-brane solutions for a wide class of intersection
rules are presented. The solutions are defined on a manifold that contains a
product of n - 1 Ricci-flat internal spaces. They are defined up to moduli
functions H_s = H_s(R) obeying a non-linear differential equations (equivalent
to Toda-type equations) with certain boundary conditions imposed. Using
conjecture on polynomial structure of H_s for intersections related to Lie
algebras, new A_2-dyon solutions are obtained. Two examples of these A_2-dyon
solutions, i.e. dyon in D = 11 supergravity with M2 and M5 branes intersecting
at a point and dyon in Kaluza-Klein theory, are considered.


title:
Macroscopic Einstein-Maxwell equations for a system of interacting
  particles to second-order accuracy in the interaction constant

abstract:
  In this paper the macroscopic Einstein and Maxwell equations for system, in
which the electromagnetic interactions are dominating (for instance, the
cosmological plasma before the moment of recombination), are derived. Ensemble
averaging of the microscopic Einstein - Maxwell equations and the iouville
equations for the random functions leads to a closed system of macroscopic
Einstein - Maxwell equations and kinetic equations for one-particle
distribution functions. The macroscopic Einstein equations for a relativistic
plasma differ from the classical Einstein equations in that their left-hand
sides contain additional terms due to particle interaction. The terms are
traceless tensors with zero divergence. An explicit covariant expression for
these terms is given in the form of momentum-space integrals of expressions
depending on one-particles distribution functions of the interacting particles
of the medium. The macroscopic Maxwell equations alsow differ from the
classical macroscopic Maxwell equations in that their left-hand sides contain
additional terms due to particle interaction as well the effects of general
relativity.


title:
Macroscopic Einstein equations for a system of interacting particles and
  their cosmological applications

abstract:
  One of the possible applications of macroscopic Einstein equations has been
considered. So, the nonsingular isotropic and uniform cosmological model is
built. The cosmological consequences of this model are agree with conclusions
of standard hot model of the Universe.


title:
See Project for Testing Gravity in Space: Current Status and New
  Estimates

abstract:
  We describe some new estimates concerning the recently proposed SEE
(Satellite Energy Exchange) experiment for measuring the gravitational
interaction parameters in space. The experiment entails precision tracking of
the relative motion of two test bodies (a heavy "Shepherd", and a light
"Particle") on board a drag-free capsule. The new estimates include (i) the
sensitivity of Particle trajectories and G measurement to the Shepherd
quadrupole moment uncertainties; (ii) the measurement errors of G and the
strength of a putative Yukawa-type force whose range parameter $\lambda$ may be
either of the order of a few metres or close to the Earth radius; (iii) a
possible effect of the Van Allen radiation belts on the SEE experiment due to
test body electric charging


title: Gravitational waves in preheating

abstract:
  We study the evolution of gravitational waves through the preheating era that
follows inflation. The oscillating inflaton drives parametric resonant growth
of scalar field fluctuations, and although super-Hubble tensor modes are not
strongly amplified, they do carry an imprint of preheating. This is clearly
seen in the Weyl tensor, which provides a covariant description of
gravitational waves.


title: Localization of gravitational energy in ENU model and its consequences

abstract:
  The contribution provides the starting points and background of the model of
Expansive Nondecelerative Universe (ENU), manifests the advantage of
exploitation of Vaidya metrics for the localization and quantization of
gravitational energy, and offers four examples of application of the ENU model,
namely energy of cosmic background radiation, energy of Z and W bosons acting
in weak interactions, hyperfine splitting observed for hydrogen 1s orbital.
Moreover, time evolution of vacuum permitivity and permeability is predicted.%


title: Inflation and quintessence with nonminimal coupling

abstract:
  The nonminimal coupling (NMC) of the scalar field to the Ricci curvature is
unavoidable in many cosmological scenarios. Inflation and quintessence models
based on nonminimally coupled scalar fields are studied, with particular
attention to the balance between the scalar potential and the NMC term in the
action. NMC makes acceleration of the universe harder to achieve for the usual
potentials, but it is beneficial in obtaining cosmic acceleration with unusual
potentials. The slow-roll approximation with NMC, conformal transformation
techniques, and other aspects of the physics of NMC are clarified.


title:
Boundary actions in Ponzano-Regge discretization, Quantum groups and
  AdS(3)

abstract:
  Boundary actions for three-dimensional quantum gravity in the discretized
formalism of Ponzano-Regge are studied with a view towards understanding the
boundary degrees of freedom. These degrees of freedom postulated in the
holography hypothesis are supposed to be characteristic of quantum gravity
theories. In particular it is expected that some of these degrees of freedom
reside on black hole horizons. This paper is a study of these ideas in the
context of a theory of quantum gravity that requires no additional structure
such as supersymmetry or special gravitational backgrounds. Lorentzian as well
as Euclidean regimes are examined. Some surprising relationships to Liouville
theory and string theory in AdS(3) are found.


title: The Velocity of Gravitational Waves

abstract:
  We examine the propagation of gravitational waves in the new field theory of
gravitation recently proposed by Novello-De Lorenci-Luciane (NDL). This
examination is done on a solvable case corresponding to a spherically symmetric
static configuration. We show that in NDL theory the velocity of gravitational
waves is lower than light velocity. We point out some consequences of this
result and suggest a possible scenario for its verification.


title: Pad\'e approximants for truncated post-Newtonian neutron star models

abstract:
  Pad\'e approximants to truncated post-Newtonian neutron star models are
constructed. The Pad\'e models converge faster to the general relativistic (GR)
solution than the truncated post-Newtonian ones. The evolution of initial data
using the Pad\'e models approximates better the evolution of full GR initial
data than the truncated Taylor models. In the absence of full GR initial data
(e.g., for neutron star binaries or black hole binary systems), Pad\'e initial
data could be a better option than the straightforward truncated post-Newtonian
(Taylor) initial data.


title: Spacetime as a Feynman diagram: the connection formulation

abstract:
  Spin foam models are the path integral counterparts to loop quantized
canonical theories. In the last few years several spin foam models of gravity
have been proposed, most of which live on finite simplicial lattice spacetime.
The lattice truncates the presumably infinite set of gravitational degrees of
freedom down to a finite set. Models that can accomodate an infinite set of
degrees of freedom and that are independent of any background simplicial
structure, or indeed any a priori spacetime topology, can be obtained from the
lattice models by summing them over all lattice spacetimes. Here we show that
this sum can be realized as the sum over Feynman diagrams of a quantum field
theory living on a suitable group manifold, with each Feynman diagram defining
a particular lattice spacetime. We give an explicit formula for the action of
the field theory corresponding to any given spin foam model in a wide class
which includes several gravity models. Such a field theory was recently found
for a particular gravity model [De Pietri et al, hep-th/9907154]. Our work
generalizes this result as well as Boulatov's and Ooguri's models of three and
four dimensional topological field theories, and ultimately the old matrix
models of two dimensional systems with dynamical topology. A first version of
our result has appeared in a companion paper [gr-qc\0002083]: here we present a
new and more detailed derivation based on the connection formulation of the
spin foam models.


title: Dynamic Cosmic Strings I

abstract:
  The field equations for a time dependent cylindrical cosmic string coupled to
gravity are reformulated in terms of geometrical variables defined on a
2+1-dimensional spacetime by using the method of Geroch decomposition. Unlike
the 4-dimensional spacetime the reduced case is asymptotically flat. A
numerical method for solving the field equations which involves conformally
compactifying the space and including null infinity as part of the grid is
described. It is shown that the code reproduces the results of a number of
vacuum solutions with one or two degrees of freedom. In the final section the
interaction between the cosmic string and a pulse of gravitational radiation is
briefly described. This will be fully analysed in the sequel.


title:
On the selection of triads in the teleparallel geometry and Bondi's
  radiating metric

abstract:
  A consistent Hamiltonian formulation of the teleparallel equivalent of
general relativity (TEGR) requires the theory to be invariant under the global
SO(3) symmetry group, which acts on orthonormal triads in three-dimensional
spacelike hypersurfaces. In the TEGR it is possible to make definite statements
about the energy of the gravitational field. In this geometrical framework two
sets of triads related by a local SO(3) transformation yield different
descriptions of the gravitational energy. Here we consider the problem of
assigning a unique set of triads to the metric tensor restricted to the
three-dimensional hypersurface. The analysis is carried out in the context of
Bondi's radiating metric. A simple and original expression for Bondi's news
function is obtained, which allows us to carry out numerical calculations and
verify that a triad with a specific asymptotic behaviour yields the minimum
gravitational energy for a fixed space volume containing the radiating source.
This result supports the conjecture that the requirement of a minimum
gravitational energy for a given space volume singles out uniquely the correct
set of orthonormal triads.


title:
Canonical Formulation of Gravitational Teleparallelism in 2+1 Dimensions
  in Schwinger's Time Gauge

abstract:
  We consider the most general class of teleparallel gravitational {}{}theories
quadratic in the torsion tensor, in three space-time dimensions, and carry out
a detailed investigation of its Hamiltonian formulation in Schwinger's time
gauge. This general class is given by a family of three-parameter theories. A
consistent implementation of the Legendre transform reduces the original theory
to a one-parameter family of theories. By calculating Poisson brackets we show
explicitly that the constraints of the theory constitute a first-class set.
Therefore the resulting theory is well defined with regard to time evolution.
The structure of the Hamiltonian theory rules out the existence of the
Newtonian limit.


title: Close limit of grazing black hole collisions: non-spinning holes

abstract:
  Using approximate techniques we study the final moments of the collision of
two (individually non-spinnning) black holes which inspiral into each other.
The approximation is based on treating the whole space-time as a single
distorted black hole. We obtain estimates for the radiated energy, angular
momentum and waveforms for the gravitational waves produced in such a
collision. The results can be of interest for analyzing the data that will be
forthcoming from gravitational wave interferometric detectors, like the LIGO,
GEO, LISA, VIRGO and TAMA projects.


title: New Einstein-Maxwell fields of Levi-Civita's type

abstract:
  The method based on the Horsky-Mitskievitch conjecture is applied to the
Levi-Civita vacuum metric. It is shown, that every Killing vector is connected
with a particular class of Einstein-Maxwell fields and each of those classes is
found explicitly. Some of obtained classes are quite new. Radial geodesic
motion in constructed space-times is discussed and graphically illustrated in
the Appendix.


title: Kinematics of vector fields

abstract:
  Different (not only by sign) affine connections are introduced for
contravariant and covariant tensor fields over a differentiable manifold by
means of a non-canonical contraction operator, defining the notion dual bases
and commuting with the covariant and with the Lie-differential operator.
Classification of the linear transports on the basis of the connections between
the connections is given. Notion of relative velocity and relative acceleration
for vector fields are determined. By means of these kinematic characteristics
several other types of notions as shear velocity, shear acceleration, rotation
velocity, rotation acceleration, expansion velocity and expansion acceleration
are introduced and on their basis auto-parallel and non-isotropic (non-null)
vector fields are classified.


title: Some remarks on the Bel-Robinson Tensor

abstract:
  In this paper we present our point of view on correct physical interpretation
of the Bel-Robinson tensor within the framework of the standard General
Relativity ({\bf GR}), i.e., within the framework of the {\bf GR} without
supplementary elements like arbitrary vector field, distinguished tetrads field
or second metric. We show that this tensor arises as a consequence of the
Bianchi identities and, in a natural manner, it is linked to the differences of
the canonical gravitational energy-momentum calculated in normal coordinates
{\bf NC(P)}.


title: A classification of spherically symmetric self-similar dust models

abstract:
  We classify all spherically symmetric dust solutions of Einstein's equations
which are self-similar in the sense that all dimensionless variables depend
only upon $z\equiv r/t$. We show that the equations can be reduced to a special
case of the general perfect fluid models with equation of state $p=\alpha \mu$.
The most general dust solution can be written down explicitly and is described
by two parameters. The first one (E) corresponds to the asymptotic energy at
large $|z|$, while the second one (D) specifies the value of z at the
singularity which characterizes such models. The E=D=0 solution is just the
flat Friedmann model. The 1-parameter family of solutions with z>0 and D=0 are
inhomogeneous cosmological models which expand from a Big Bang singularity at
t=0 and are asymptotically Friedmann at large z; models with E>0 are everywhere
underdense relative to Friedmann and expand forever, while those with E<0 are
everywhere overdense and recollapse to a black hole containing another
singularity. The black hole always has an apparent horizon but need not have an
event horizon. The D=0 solutions with z<0 are just the time reverse of the z>0
ones. The 2-parameter solutions with D>0 again represent inhomogeneous
cosmological models but the Big Bang singularity is at $z=-1/D$, the Big Crunch
singularity is at $z=+1/D$, and any particular solution necessarily spans both
z<0 and z>0. While there is no static model in the dust case, all these
solutions are asymptotically ``quasi-static'' at large $|z|$. As in the D=0
case, the ones with $E \ge 0$ expand or contract monotonically but the latter
may now contain a naked singularity. The ones with E<0 expand from or
recollapse to a second singularity, the latter containing a black hole.


title:
A New Study about the Two Formulations of Conservation Laws for Matter
  Plus Gravitational Field and Their Experimental Test

abstract:
  The debate on conservation laws in general relativity eighty years ago is
reviewed and restudied. The physical meaning of the identities in the
conservation laws for matter plus gravitational field is reexamined and new
interpretations for gravitational wave are given. The conclusions of these
studies are distinct from the prevalent views, it can be demonstrated that
gravitational wave does not transmit energy (and momentum) but only transmits
informations. An experimental test is offered to decide which conservation laws
are correct.


title:
Spherically symmetric self-similar solutions and their astrophysical and
  cosmological applications

abstract:
  We discuss spherically symmetric perfect fluid solutions of Einstein's
equations which have equation of state ($p=\alpha \mu$) and which are
self-similar in the sense that all dimensionless variables depend only upon
$z\equiv r/t$. For each value of $\alpha$, such solutions are described by two
parameters and have now been completely classified. There is a 1-parameter
family of solutions asymptotic to the flat Friedmann model at large values of
z. These represent either black holes or density perturbations which grow as
fast as the particle horizon; the underdense solutions may be relevant to the
existence of large-scale cosmic voids. There is also a 1-parameter family of
solutions asymptotic to a self-similar Kantowski-Sachs model at large z. These
are probably only physically realistic for $-1<\alpha<-1/3$, in which case they
may relate to the formation of bubbles in an inflationary universe. There is a
2-parameter family of solutions associated with a self-similar static solution
at large z. This family contains solutions with naked singularities and this
includes the ``critical'' solution discovered in recent collapse calculations
for $\alpha < 0.28$. Finally, for $\alpha >1/5$, there is a family of solutions
which are asymptotically Minkowski. These asymptote either to infinite z, in
which case they are described by one parameter, or to a finite value of z, in
which case they are described by two parameters and this includes the
``critical'' solution for $\alpha >0.28$. We discuss the stability of
spherically symmetric similarity solutions to more general (non-self-similar)
spherically symmetric perturbations.


title:
Canonical formulation of N = 2 supergravity in terms of the Ashtekar
  variable

abstract:
  We reconstruct the Ashtekar's canonical formulation of N = 2 supergravity
(SUGRA) starting from the N = 2 chiral Lagrangian derived by closely following
the method employed in the usual SUGRA. In order to get the full graded algebra
of the Gauss, U(1) gauge and right-handed supersymmetry (SUSY) constraints, we
extend the internal, global O(2) invariance to local one by introducing a
cosmological constant to the chiral Lagrangian. The resultant Lagrangian does
not contain any auxiliary fields in contrast with the 2-form SUGRA and the SUSY
transformation parameters are not constrained at all. We derive the canonical
formulation of the N = 2 theory in such a manner as the relation with the usual
SUGRA be explicit at least in classical level, and show that the algebra of the
Gauss, U(1) gauge and right-handed SUSY constraints form the graded algebra,
G^2SU(2)(Osp(2,2)). Furthermore, we introduce the graded variables associated
with the G^2SU(2)(Osp(2,2)) algebra and we rewrite the canonical constraints in
a simple form in terms of these variables. We quantize the theory in the
graded-connection representation and discuss the solutions of quantum
constraints.


title:
Coupling of Gravitation and Electromagnetism in the Weak Field
  Approximation

abstract:
  Using the weak field approximation, we can express the theory of general
relativity in a Maxwell-type structure comparable to electromagnetism. We find
that every electromagnetic field is coupled to a gravitoelectric and
gravitomagnetic field. Acknowledging the fact that both fields originate from
the same source, the particle, we can express the magnetic and electric field
through their gravitational respective analogues using the proportionality
coefficient k. This coefficient depends on the ratio of mass and charge and the
ratio between the electromagnetic and gravitic-gravitomagnetic permittivity and
permeability respectively. Although the coefficient is very small, the fact
that electromagnetic fields in material media can be used to generate
gravitational and gravitomagnetic fields and vice versa is not commonly known.
We find that the coupling coefficient can be increased by massive ion currents,
electron and nuclear spin-alignment. Advances in material sciences, cryogenic
technology and high frequency electromagnetic fields in material media may lead
to applications of the derived relationships.


title: The big bang as a higher-dimensional shock wave

abstract:
  We give an exact solution of the five-dimensional field equations which
describes a shock wave moving in time and the extra (Kaluza-Klein) coordinate.
The matter in four-dimensional spacetime is a cosmology with good physical
properties. The solution suggests to us that the 4D big bang was a 5D shock
wave.


title: Asymptotic singular behavior of Gowdy spacetimes in string theory

abstract:
  We study $T^{3}$ Gowdy spacetimes in the Einstein-Maxwell-dilaton-axion
system and show by the Fuchsian algorithm that they have in general
asymptotically velocity-term dominated singularities. The families of the
corresponding solutions depend on the maximum number of arbitrary functions.
Although coupling of the dilaton field with the Maxwell and/or the axion fields
corresponds to the ``potential'' which appears in the Hamiltonian of vacuum
Bianchi IX spacetimes, our result means that the spacetimes do not become
Mixmaster necessarily.


title: Measurement Theory and General Relativity

abstract:
  The theory of measurement is employed to elucidate the physical basis of
general relativity. For measurements involving phenomena with intrinsic length
or time scales, such scales must in general be negligible compared to the
(translational and rotational) scales characteristic of the motion of the
observer. Thus general relativity is a consistent theory of coincidences so
long as these involve classical point particles and electromagnetic rays
(geometric optics). Wave optics is discussed and the limitations of the
standard theory in this regime are pointed out. A nonlocal theory of
accelerated observers is briefly described that is consistent with observation
and excludes the possibility of existence of a fundamental scalar field in
nature.


title: Nonstatic global string in Brans-Dicke theory

abstract:
  Gravitational field of a nonstatic global string has been studied in the
context of Brans-Dicke theory of gravity. Both the metric components and the BD
scalar field are assumed to be nonseparable functions of time and space.The
spacetime may or may not have any singularity at a finite distance from the
string core but the singularity at a particular time always remains. It has
been shown that the spacetime exhibits both outgoing and incoming gravitational
radiation.


title:
U. Leonhardt and P. Piwnicki reply to the ``Comment on `Relativistic
  Effects of Light in Moving Media with Extremely Low Group Velocity ' '' by M.
  Visser

abstract:
  Leonhardt and Piwnicki reply to Visser's ``Comment on `Relativistic Effects
of Light in Moving Media with Extremely Low Group Velocity' ''.


title:
Thermal quasi-equilibrium states across Landau horizons in the effective
  gravity of superfluids

abstract:
  We give an account of the physical behaviour of a quasiparticle horizon due
to non-Lorentz invariant modifications of the effective space-time experienced
by the quasiparticles (``matter'') for high momenta. By introducing a
``relativistic'' conserved energy-momentum tensor, we derive quasi-equilibrium
states of the fluid across the ``Landau'' quasiparticle horizon at temperatures
well above the quantum Hawking temperature. Nonlinear dispersion of the
quasiparticle energy spectrum is instrumental for quasiparticle communication
and exchange across the horizon. It is responsible for the establishment of the
local thermal equilibrium across the horizon with the Tolman temperature being
inhomogeneous behind the horizon. The inhomogeneity causes relaxation of the
quasi-equilibrium states due to scattering of thermal quasiparticles, which
finally leads to a shrinking black hole horizon. This process serves as the
classical thermal counterpart of the quantum effect of Hawking radiation and
will allow for an observation of the properties of the horizon at temperatures
well above the Hawking temperature. We discuss the thermal entropy related to
the horizon. We find that only the first nonlinear correction to the energy
spectrum is important for the thermal properties of the horizon. They are fully
determined by an energy of order $E_{\rm Planck}(T/E_{\rm Planck})^{1/3}$,
which is well below the Planck energy scale $E_{\rm Planck}$, so that Planck
scale physics is not involved in determining thermal quantities related to the
horizon.


title: Spherically symmetric empty space and its dual in general relativity

abstract:
  In the spirit of the Newtonian theory, we characterize spherically symmetric
empty space in general relativity in terms of energy density measured by a
static observer and convergence density experienced by null and timelike
congruences. It turns out that space surrounding a static particle is entirely
specified by vanishing of energy and null convergence density. The
electrograv-dual$^{1}$ to this condition would be vanishing of timelike and
null convergence density which gives the dual-vacuum solution representing a
Schwarzschild black hole with global monopole charge$^{2}$ or with cloud of
string dust$^{3}$. Here the duality$^{1}$ is defined by interchange of active
and passive electric parts of the Riemann curvature, which amounts to
interchange of the Ricci and Einstein tensors. This effective characterization
of stationary vacuum works for the Schwarzschild and NUT solutions. The most
remarkable feature of the effective characterization of empty space is that it
leads to new dual spaces and the method can also be applied to lower and higher
dimensions.


title: Noether Charges, Brown-York Quasilocal Energy and Related Topics

abstract:
  The Lagrangian proposed by York et al. and the covariant first order
Lagrangian for General Relativity are introduced to deal with the (vacuum)
gravitational field on a reference background. The two Lagrangians are compared
and we show that the first one can be obtained from the latter under suitable
hypotheses. The induced variational principles are also compared and discussed.
A conditioned correspondence among Noether conserved quantities, quasilocal
energy and the standard Hamiltonian obtained by 3+1 decomposition is also
established. As a result, it turns out that the covariant first order
Lagrangian is better suited whenever a reference background field has to be
taken into account, as it is commonly accepted when dealing with conserved
quantities in non-asymptotically flat spacetimes. As a further advantage of the
use of a covariant first order Lagrangian, we show that all the quantities
computed are manifestly covariant, as it is appropriate in General Relativity.


title: On the Particle Definition in the presence of Black Holes

abstract:
  A canonical particle definition via the diagonalisation of the Hamiltonian
for a quantum field theory in specific curved space-times is presented. Within
the provided approach radial ingoing or outgoing Minkowski particles do not
exist. An application of this formalism to the Rindler metric recovers the
well-known Unruh effect. For the situation of a black hole the Hamiltonian
splits up into two independent parts accounting for the interior and the
exterior domain, respectively. It turns out that a reasonable particle
definition may be accomplished for the outside region only. The Hamiltonian of
the field inside the black hole is unbounded from above and below and hence
possesses no ground state. The corresponding equation of motion displays a
linear global instability. Possible consequences of this instability are
discussed and its relations to the sonic analogues of black holes are
addressed. PACS-numbers: 04.70.Dy, 04.62.+v, 10.10.Ef, 03.65.Db.


title: High energy physics and the very-early Universe with LISA

abstract:
  Gravitational wave experiments will play a key role in the investigation of
the frontiers of cosmology and the structure of fundamental fields at high
energies, by detecting, or setting strong upper-limits to, the primordial
gravitational wave background produced in the early-Universe. Here we discuss
the impact of space-borne laser interferometric detectors operating in the
low-frequency window ($\sim 1 \mu$Hz - 1 Hz); the aim of our analysis is to
assess the detectability of a primordial background characterized by a
fractional energy density $\Omega \sim 10^{-16} - 10^{-15}$, which is
consistent with the prediction of "slow-roll" inflationary models.


title: Gravitational Couplings of Intrinsic Spin

abstract:
  The gravitational couplings of intrinsic spin are briefly reviewed. A
consequence of the Dirac equation in the exterior gravitational field of a
rotating mass is considered in detail, namely, the difference in the energy of
a spin-1/2 particle polarized vertically up and down near the surface of a
rotating body is $\hbar\Omega\sin\theta$. Here $\theta$ is the latitude and
$\Omega = 2GJ/(c^2 R^3)$, where $J$ and $R$ are, respectively, the angular
momentum and radius of the body. It seems that this relativistic quantum
gravitational effect could be measurable in the foreseeable future.


title: Entropy using Path Integrals for Quantum Black Hole Models

abstract:
  Several eigenvalue equations that could describe quantum black holes have
been proposed in the canonical quantum gravity approach. In this paper, we
choose one of the simplest of these quantum equations to show how the usual
Feynman's path integral method can be applied to obtain the corresponding
statistical properties. We get a logarithmic correction to the
Bekenstein-Hawking entropy as already obtained by other authors by other means.


title:
Darkholes: Nicer than blackholes - with a bright side, too (Does energy
  produce gravity?)

abstract:
  The geometry of three-dimensional space guides the search for a better model
than the blackhole with its unwelcome singularity. An elementary construction
produces on the 4-manifold of 2-spheres in a Riemannian 3-space a space-time
metric invariant under uniform conformal transformations of the 3-space. When
the 3-space is Euclidean, the metric reduces to de Sitter's expanding universe
metric. Generalization yields a space-time metric that retains the `exponential
expansion property' of the de Sitter metric. A strictly geometric action
principle gives field equations which, because they do not adhere to Einstein's
early confounding of energy and inertial mass with gravitating mass, admit
solutions that escape the Penrose-Hawking singularity theorems. A spherically
symmetric solution that is asymptotic to the Schwarzschild blackhole metric
has, in place of a horizon and a singularity, an Einstein-Rosen `bridge', or
`tunnel', connecting two asymptotically Euclidean regions. On one side the
gravitational center attracts, and is dark but not black; on the other side it
repels, and is bright. Travel and signaling from either side to the other via
the tunnel are possible. Analysis of the Einstein tensor of this `darkhole' (or
`darkhole-brighthole') suggests that not all energy produces gravity, and that
calling energy `negative', or its relationship to geometry `exotic', is
unjustified.


title: Scalar fields, energy conditions, and traversable wormholes

abstract:
  We describe the different possibilities that a simple and apparently quite
harmless classical scalar field theory provides to violate the energy
conditions. We demonstrate that a non-minimally coupled scalar field with a
positive curvature coupling xi>0 can easily violate all the standard energy
conditions, up to and including the averaged null energy condition (ANEC).
Indeed this violation of the ANEC suggests the possible existence of
traversable wormholes supported by non-minimally coupled scalars. To
investigate this possibility we derive the classical solutions for gravity plus
a general (arbitrary xi) massless non-minimally coupled scalar field,
restricting attention to the static and spherically symmetric configurations.
Among these classical solutions we find an entire branch of traversable
wormholes for every xi>0. (This includes and generalizes the case of conformal
coupling xi=1/6 we considered in Phys. Lett. B466 (1999) 127--134;
gr-qc/9908029) For these traversable wormholes to exist we demonstrate that the
scalar field must reach trans-Planckian values somewhere in the geometry. We
discuss how this can be accommodated within the current state of the art
regarding scalar fields in modern theoretical physics. We emphasize that these
scalar field theories, and the traversable wormhole solutions we derive, are
compatible with all known experimental constraints from both particle physics
and gravity.


title: On product spacetime with 2-sphere of constant curvature

abstract:
  If we consider the spacetime manifold as product of a constant curvature
2-sphere (hypersphere) and a 2-space, then solution of the Einstein equation
requires that the latter must also be of constant curvature. There exist only
two solutions for classical matter distribution which are given by the Nariai
(anti) metric describing an Einstein space and the Bertotti - Robinson (anti)
metric describing a uniform electric field. These two solutions are
transformable into each other by letting the timelike convergence density
change sign. The hyperspherical solution is anti of the spherical one and the
vice -versa. For non classical matter, we however find a new solution, which is
electrograv dual to the flat space, and describes a cloud of string dust of
uniform energy density. We also discuss some interesting features of the
particle motion in the Bertotti - Robinson metric.


title: Gravitational waves from black hole collisions via an eclectic approach

abstract:
  We present the first results in a new program intended to make the best use
of all available technologies to provide an effective understanding of waves
from inspiralling black hole binaries in time for imminent observations. In
particular, we address the problem of combining the close-limit approximation
describing ringing black holes and full numerical relativity, required for
essentially nonlinear interactions. We demonstrate the effectiveness of our
approach using general methods for a model problem, the head-on collision of
black holes. Our method allows a more direct physical understanding of these
collisions indicating clearly when non-linear methods are important. The
success of this method supports our expectation that this unified approach will
be able to provide astrophysically relevant results for black hole binaries in
time to assist gravitational wave observations.


title: On the ADM Equations for General Relativity

abstract:
  The Arnowitt-Deser-Misner (ADM) evolution equations for the induced metric
and the extrinsic-curvature tensor of the spacelike surfaces which foliate the
space-time manifold in canonical general relativity are a first-order system of
quasi-linear partial differential equations, supplemented by the constraint
equations. Such equations are here mapped into another first-order system. In
particular, an evolution equation for the trace of the extrinsic-curvature
tensor K is obtained whose solution is related to a discrete spectral
resolution of a three-dimensional elliptic operator P of Laplace type.
Interestingly, all nonlinearities of the original equations give rise to the
potential term in P. An example of this construction is given in the case of a
closed Friedmann-Lemaitre-Robertson-Walker universe. Eventually, the ADM
equations are re-expressed as a coupled first-order system for the induced
metric and the trace-free part of K. Such a system is written in a form which
clarifies how a set of first-order differential operators and their inverses,
jointly with spectral resolutions of operators of Laplace type, contribute to
solving, at least in principle, the original ADM system.


title: A New Way to Make Waves

abstract:
  I describe a new algorithm for solving nonlinear wave equations. In this
approach, evolution takes place on characteristic hypersurfaces. The algorithm
is directly applicable to electromagnetic, Yang-Mills and gravitational fields
and other systems described by second differential order hyperbolic equations.
The basic ideas should also be applicable to hydrodynamics. It is an especially
accurate and efficient way for simulating waves in regions where the
characteristics are well behaved. A prime application of the algorithm is to
Cauchy-characteristic matching, in which this new approach is matched to a
standard Cauchy evolution to obtain a global solution. In a model problem of a
nonlinear wave, this proves to be more accurate and efficient than any other
present method of assigning Cauchy outer boundary conditions. The approach was
developed to compute the gravitational wave signal produced by collisions of
two black holes. An application to colliding black holes is presented.


title: Gravitational Aharonov-Bohm effect and gravitational lensing

abstract:
  Considering the spacetime around a rotating massif body it is seen that the
time of flight of a light ray is different whether it travels on one side of
the source or on the other. The difference is proportional to the angular
momentum of the body. In the case that a compact rapidly rotating object is the
source of a gravitational lensing effect, the contribution coming from the
above mentioned gravitational Aharonov-Bohm effect should be added to the other
causes of phase difference between light rays coming from different images of
the same object.


title: Making use of geometrical invariants in black hole collisions

abstract:
  We consider curvature invariants in the context of black hole collision
simulations. In particular, we propose a simple and elegant combination of the
Weyl invariants I and J, the {\sl speciality index} ${\cal S}$. In the context
of black hole perturbations $\cal S$ provides a measure of the size of the
distortions from an ideal Kerr black hole spacetime. Explicit calculations in
well-known examples of axisymmetric black hole collisions demonstrate that this
quantity may serve as a useful tool for predicting in which cases perturbative
dynamics provide an accurate estimate of the radiation waveform and energy.
This makes ${\cal S}$ particularly suited to studying the transition from
nonlinear to linear dynamics and for invariant interpretation of numerical
results.


title:
The Transition from Inspiral to Plunge for a Compact Body in a Circular
  Equatorial Orbit Around a Massive, Spinning Black Hole

abstract:
  There are three regimes of gravitational-radiation-reaction-induced inspiral
for a compact body with mass mu, in a circular, equatorial orbit around a Kerr
black hole with mass M>>mu: (i) The "adiabatic inspiral regime", in which the
body gradually descends through a sequence of circular, geodesic orbits. (ii) A
"transition regime", near the innermost stable circular orbit (isco). (iii) The
"plunge regime", in which the body travels on a geodesic from slightly below
the isco into the hole's horizon. This paper gives an analytic treatment of the
transition regime and shows that, with some luck, gravitational waves from the
transition might be measurable by the space-based LISA mission.


title: Locally U(1)*U(1) Symmetric Cosmological Models: Topology and Dynamics

abstract:
  We show examples which reveal influences of spatial topologies to dynamics,
using a class of spatially {\it closed} inhomogeneous cosmological models. The
models, called the {\it locally U(1)$\times$U(1) symmetric models} (or the {\it
generalized Gowdy models}), are characterized by the existence of two commuting
spatial {\it local} Killing vectors. For systematic investigations we first
present a classification of possible spatial topologies in this class. We
stress the significance of the locally homogeneous limits (i.e., the Bianchi
types or the `geometric structures') of the models. In particular, we show a
method of reduction to the natural reduced manifold, and analyze the
equivalences at the reduced level of the models as dynamical models. Based on
these fundamentals, we examine the influence of spatial topologies on dynamics
by obtaining translation and reflection operators which commute with the
dynamical flow in the phase space.


title: Solar System Tests of Higher-Dimensional Gravity

abstract:
  The classical tests of general relativity - light deflection, time delay and
perihelion shift - are applied, along with the geodetic precession test, to the
five-dimensional extension of the theory known as Kaluza-Klein gravity, using
an analogue of the four-dimensional Schwarzschild metric. The perihelion
advance and geodetic precession calculations are generalized for the first time
to situations in which the components of momentum and spin along the extra
coordinate do not vanish. Existing data on light- bending around the Sun using
long- baseline radio interferometry, ranging to Mars using the Viking lander,
and the perihelion precession of Mercury all constrain a small parameter b
associated with the extra part of the metric to be less than |b| < 0.07 in the
solar system. An order-of-magnitude increase in sensitivity is possible from
perihelion precession, if better limits on solar oblateness become available.
Measurement of geodetic precession by the Gravity Probe B satellite will
improve this significantly, probing values of b with an accuracy of one part in
10^4 or more.


title:
Angular momentum and an invariant quasilocal energy in general
  relativity

abstract:
  Owing to its transformation property under local boosts, the Brown-York
quasilocal energy surface density is the analogue of E in the special
relativity formula: E^2-p^2=m^2. In this paper I will motivate the general
relativistic version of this formula, and thereby arrive at a geometrically
natural definition of an `invariant quasilocal energy', or IQE. In analogy with
the invariant mass m, the IQE is invariant under local boosts of the set of
observers on a given two-surface S in spacetime. A reference energy subtraction
procedure is required, but in contrast to the Brown-York procedure, S is
isometrically embedded into a four-dimensional reference spacetime. This
virtually eliminates the embeddability problem inherent in the use of a
three-dimensional reference space, but introduces a new one: such embeddings
are not unique, leading to an ambiguity in the reference IQE. However, in this
codimension-two setting there are two curvatures associated with S: the
curvatures of its tangent and normal bundles. Taking advantage of this fact, I
will suggest a possible way to resolve the embedding ambiguity, which at the
same time will be seen to incorporate angular momentum into the energy at the
quasilocal level. I will analyze the IQE in the following cases: both the
spatial and future null infinity limits of a large sphere in asymptotically
flat spacetimes; a small sphere shrinking toward a point along either spatial
or null directions; and finally, in asymptotically anti-de Sitter spacetimes.
The last case reveals a striking similarity between the reference IQE and a
certain counterterm energy recently proposed in the context of the conjectured
AdS/CFT correspondence.


title: Naked Singularity Explosion

abstract:
  It is known that the gravitational collapse of a dust ball results in naked
singularity formation from an initial density profile which is physically
reasonable. In this paper, we show that explosive radiation is emitted during
the formation process of the naked singularity.


title:
Second post-Newtonian radiative evolution of the relative orientations
  of angular momenta in spinning compact binaries

abstract:
  The radiative evolution of the relative orientations of the spin and orbital
angular momentum vectors ${\bf S}_{{\bf 1}}, {\bf S}_{{\bf 2}}$ and ${\bf L}$,
characterizing a binary system on eccentric orbit is studied up to the second
post-Newtonian order. As an intermediate result, all Burke-Thorne type
instantaneous radiative changes in the spins are shown to average out over a
radial period. It is proved that spin-orbit and spin-spin terms contribute to
the radiative angular evolution equations, while Newtonian, first and second
post-Newtonian terms together with the leading order tail terms do not. In
complement to the spin-orbit contribution, given earlier, the spin-spin
contribution is computed and split into two-body and self-interaction parts.
The latter provide the second post-Newtonian order corrections to the 3/2 order
Lense-Thirring description.


title: A quasilocal calculation of tidal heating

abstract:
  We present a method for computing the flux of energy through a closed surface
containing a gravitating system. This method, which is based on the quasilocal
formalism of Brown and York, is illustrated by two applications: a calculation
of (i) the energy flux, via gravitational waves, through a surface near
infinity and (ii) the tidal heating in the local asymptotic frame of a body
interacting with an external tidal field. The second application represents the
first use of the quasilocal formalism to study a non-stationary spacetime and
shows how such methods can be used to study tidal effects in isolated
gravitating systems.


title: Can a Kasner Universe with a Viscous Cosmological Fluid be Anisotropic?

abstract:
  A Bianchi type -I metric of Kasner form is considered, when the space is
filled with a viscous fluid. Whereas an ideal (nonviscous) fluid permits the
Kasner metric to be anisotropic provided that the fluid satisfies the
Zel'dovich equation of state, the viscous fluid does not permit the Kasner
metric to be anisotropic at all. In the latter case, we calculate the Kasner
(isotropic) metric expressed by the fluid's density, pressure, and bulk
viscosity, at some chosen instant $t=t_0$. The equation of state is also
calculated. The present paper is related to a recent Comment of Cataldo and del
Campo [Phys. Rev. D, scheduled to April 15, 2000], on a previous work of the
present authors [Phys. Rev. D {\bf 56}, 3322 (1997)].


title: Group Averaging and Refined Algebraic Quantization

abstract:
  We review the framework of Refined Algebraic Quantization and the method of
Group Averaging for quantizing systems with first-class constraints. Aspects
and results concerning the generality, limitations, and uniqueness of these
methods are discussed.


title: Cosmic String Wakes in Scalar-Tensor Gravities

abstract:
  The formation and evolution of cosmic string wakes in the framework of a
scalar-tensor gravity are investigated in this work. We consider a simple model
in which cold dark matter flows past an ordinary string and we treat this
motion in the Zel'dovich approximation. We make a comaprison between our
results and previous results obtained in the context of General Relativity. We
propose a mechanism in which the contribution of the scalar field to the
evolution of the wakes may lead to a cosmological observation.