title: Gravitational field of a rotating gravitational dyon

abstract:
  We have obtained the most general solution of the Einstein vacuum equation
for the axially symmetric stationary metric in which both the
  Hamilton-Jacobi equation for particle motion and the Klein - Gordon equation
are separable. It can be interpreted to describe the gravitational field of a
rotating dyon, a particle endowed with both gravoelectric (mass) and
gravomagnetic (NUT parameter) charge. Further, there also exists a duality
relation between the two charges and the radial and the polar angle coordinates
which keeps the solution invariant. The solution can however be transformed
into the known Kerr - NUT solution indicating its uniqueness under the
separability of equations of motion.


title:
Holographic principle and the dominant energy condition for Kasner type
  metrics

abstract:
  In this letter we study adiabatic anisotropic matter filled Bianchi type I
models of the Kasner form together with the cosmological holographic bound. We
find that the dominant energy condition and the holographic bound give
precisely the same constraint on the scale factor parameters that appear in the
metric.


title: An alternative to Minkowski space-time

abstract:
  The starting point of this work is the principle that all movement of
particles and photons must follow geodesics of a 4-dimensional space where time
intervals are always a measure on geodesic arc lengths. The last 3 coordinates
(alpha = 1,2,3) are immediately associated with the usual physical space
coordinates, while the first coordinate (\alpha=0) is later found to be related
to proper time. Avoiding the virtually hopeless effort to prove the initial
hypothesis, the work goes through several examples of increasing complexity, to
show that it is plausible. Starting with special relativity it is shown that
there is perfect mapping between the geodesics on Minkowski space-time and on
this alternative space. The discussion than follows through light propagation
in a refractive medium, and some cases of gravitation, including
Schwartzschild's outer metric. The last part of the presentation is dedicated
to electromagnetic interaction and Maxwell's equations, showing that there is a
particular solution where one of the space dimensions is eliminated and the
geodesics become equivalent to light rays in geometrical optics. A very brief
discussion is made of the implications for wave-particle duality and
quantization.


title:
Decay of accelerated protons and the existence of the
  Fulling-Davies-Unruh effect

abstract:
  We investigate the weak decay of uniformly {\em accelerated protons} in the
context of {\em standard} Quantum Field Theory. Because the mean {\em proper}
lifetime of a particle is a scalar, the same value for this observable must be
obtained in the inertial and coaccelerated frames. We are only able to achieve
this equality by considering the Fulling-Davies-Unruh effect. This reflects the
fact that the Fulling-Davies-Unruh effect is mandatory for the consistency of
Quantum Field Theory. There is no question about its existence provided one
accepts the validity of standard Quantum Field Theory in flat spacetime.


title:
Maximum Mass-Radius Ratio for Compact General Relativistic Objects in
  Schwarzschild- de Sitter Geometry

abstract:
  Upper limits for the mass-radius ratio are derived for arbitrary general
relativistic matter distributions in the presence of a cosmological constant.
General restrictions for the red shift and total energy (including the
gravitational contribution) for compact objects in the Schwarzschild-de Sitter
geometry are also obtained in terms of the cosmological constant and of the
mean density of the star.


title:
The origins of length contraction: I. The FitzGerald-Lorentz deformation
  hypothesis

abstract:
  One of the widespread confusions concerning the history of the 1887
Michelson-Morley experiment has to do with the initial explanation of this
celebrated null result due independently to FitzGerald and Lorentz. In neither
case was a strict, longitudinal length contraction hypothesis invoked, as is
commonly supposed. Lorentz postulated, particularly in 1895, any one of a
certain family of possible deformation effects for rigid bodies in motion,
including purely transverse alteration, and expansion as well as contraction;
FitzGerald may well have had the same family in mind. A careful analysis of the
Michelson-Morley experiment (which reveals a number of serious inadequacies in
many text-book treatments) indeed shows that strict contraction is not
required.


title:
Quantum fluctuations in brane-world inflation without inflaton on the
  brane

abstract:
  A Randall-Sundrum type brane-cosmological model in which slow-roll inflation
on the brane is driven solely by a bulk scalar field was recently proposed by
Himemoto and Sasaki. We analyze their model in detail and calculate the quantum
fluctuations of the bulk scalar field $\phi$ with $m^2=V''(\phi)$. We decompose
the bulk scalar field into the infinite mass spectrum of 4-dimensional fields;
the field with the smallest mass-square, called the zero-mode, and the
Kaluza-Klein modes above it with a mass gap. We find the zero-mode dominance of
the classical solution holds if $|m^2|\bar\ell^2\ll1$, where $\bar{\ell}$ is
the curvature radius of the effectively anti-de Sitter bulk, but it is violated
if $|m^2|\bar\ell^2\gg1$, though the violation is very small. Then we evaluate
the vacuum expectation value $<\delta\phi^2>$ on the brane. We find the
zero-mode contribution completely dominates if $|m^2|\bar{\ell}^2\ll 1$ similar
to the case of classical background. In contrast, we find the Kaluza-Klein
contribution is small but non-negligible if the value of $|m^2|\bar{\ell}^2$ is
large.


title: Observables in quantum gravity

abstract:
  We study a family of physical observable quantities in quantum gravity. We
denote them W functions, or n-net functions. They represent transition
amplitudes between quantum states of the geometry, are analogous to the n-point
functions in quantum field theory, but depend on spin networks with n connected
components. In particular, they include the three-geometry to three-geometry
transition amplitude. The W functions are scalar under four-dimensional
diffeomorphism, and fully gauge invariant. They capture the physical content of
the quantum gravitational theory. We show that W functions are the natural
n-point functions of the field theoretical formulation of the gravitational
spin foam models. They can be computed from a perturbation expansion, which can
be interpreted as a sum-over-four-geometries. Therefore the W functions bridge
between the canonical (loop) and the covariant (spinfoam) formulations of
quantum gravity. Following Wightman, the physical Hilbert space of the theory
can be reconstructed from the W functions, if a suitable positivity condition
is satisfied. We compute explicitly the W functions in a "free" model in which
the interaction giving the gravitational vertex is shut off, and we show that,
in this simple case, we have positivity, the physical Hilbert space of the
theory can be constructed explicitly and the theory admits a well defined
interpretation in terms of diffeomorphism invariant transition amplitudes
between quantized geometries.


title:
Revisiting Weyl's calculation of the gravitational pull in Bach's
  two-body solution

abstract:
  When the mass of one of the two bodies tends to zero, Weyl's definition of
the gravitational force in an axially symmetric, static two-body solution can
be given an invariant formulation in terms of a force four-vector. The norm of
this force is calculated for Bach's two-body solution, that is known to be in
one-to-one correspondence with Schwarzschild's original solution when one of
the two masses l, l' is made to vanish. In the limit when, say, l' goes to
zero, the norm of the force divided by l' and calculated at the position of the
vanishing mass is found to coincide with the norm of the acceleration of a test
body kept at rest in Schwarzschild's field. Both norms happen thus to grow
without limit when the test body (respectively the vanishing mass l') is kept
at rest in a position closer and closer to Schwarzschild's two-surface.


title:
Four-dimensional effective theory of gravity embeddable in a distorted
  Randall-Sundrum brane scenario

abstract:
  We present an effective four-dimensional formulation of the laws of gravity
that respects the main features of a higher (five)-dimensional scenario of
Randall-Sundrum type. The geometrical structure of the theory is that of a
Weyl-integrable configuration. Standard general relativity over Riemann
geometry is recovered through breaking of conformal symmetry. The singularity
problem is treated. The local problem in the case of the static,
spherically-symmetric Schwarzschild metric and the cosmological issue, in the
case of Friedmann-Robertson-Walker perfect fluid filled universe, are treated
separately. Vanishing of the spacetime singularities for some values of the
free parameter of the theory is achieved. The implications of the results
obtained for brane stabilization in the higher-dimensional structure are
briefly discussed.


title: Is the active gravitational mass of a charged body distance-dependent?

abstract:
  It appears to follow from the Reissner-Nordstrom solution of Einstein's
equations that the charge of a body reduces its gravitational field. In a
recent note Hushwater offered an explanation of this apparent paradox. His
explanation, however, raises more questions than solves since it implies that
the active gravitational mass of a charged body is distance-dependent and
therefore is not equal to its inertial mass.


title:
Scalar and Spinor Particles in the Spacetime of a Domain Wall in String
  Theory

abstract:
  We consider scalar and spinor particles in the spacetime of a domain wall in
the context of low energy effective string theories, such as the generalized
scalar-tensor gravity theories. This class of theories allows for an arbitrary
coupling of the wall and the (gravitational) scalar field. First, we derive the
metric of a wall in the weak-field approximation and we show that it depends on
the wall's surface energy density and on two post-Newtonian parameters. Then,
we solve the Klein-Gordon and the Dirac equations in this spacetime. We obtain
the spectrum of energy eigenvalues and the current density in the scalar and
spinor cases, respectively. We show that these quantities, except in the case
of the energy spectrum for a massless spinor particle, depend on the parameters
that characterize the scalar-tensor domain wall.


title: Global Structure of Certain Static Spacetimes (I)

abstract:
  In this paper, static spacetimes with a topological structure of R^2 \times N
is studied, where N is an arbitrary manifold. Well known Schwarzschild
spacetime and Reissner-Nordstrom spacetime are special cases. It is shown that
the existence of a constant and positive surface gravity $\kappa$ ensures the
existence of the Killing horizon, with the cross section homeomorphic to N.


title:
Modulating the experimental signature of a stochastic gravitational wave
  backgroun

abstract:
  Detecting a stationary, stochastic gravitational wave signal is complicated
by impossibility of observing the detector noise independently of the signal.
One consequence is that we require at least two detectors to observe the
signal, which will be apparent in the cross-correlation of the detector
outputs. A corollary is that there remains a systematic error, associated with
the possible presence of correlated instrumental noise, in any observation
aimed at estimating or limiting a stochastic gravitational wave signal. Here we
describe a method of identifying this systematic error by varying the
orientation of one of the detectors, leading to separate and independent
modulations of the signal and noise contribution to the cross-correlation. Our
method can be applied to measurements of a stochastic gravitational wave
background by the ALLEGRO/LIGO Livingston Observatory detector pair. We explore
-- in the context of this detector pair -- how this new measurement technique
is insensitive to a cross-correlated detector noise component that can confound
a conventional measurement.


title:
Evolution of circular, non-equatorial orbits of Kerr black holes due to
  gravitational-wave emission: II. Inspiral trajectories and gravitational
  waveforms

abstract:
  The inspiral of a ``small'' ($\mu \sim 1-100 M_\odot$) compact body into a
``large'' ($M \sim 10^{5-7} M_\odot$) black hole is a key source of
gravitational radiation for the space-based gravitational-wave observatory
LISA. The waves from such inspirals will probe the extreme strong-field nature
of the Kerr metric. In this paper, I investigate the properties of a restricted
family of such inspirals (the inspiral of circular, inclined orbits) with an
eye toward understanding observable properties of the gravitational waves that
they generate. Using results previously presented to calculate the effects of
radiation reaction, I assemble the inspiral trajectories (assuming that
radiation reacts adiabatically, so that over short timescales the trajectory is
approximately geodesic) and calculate the wave generated as the compact body
spirals in. I do this analysis for several black hole spins, sampling a range
that should be indicative of what spins we will encounter in nature. The spin
has a very strong impact on the waveform. In particular, when the hole rotates
very rapidly, tidal coupling between the inspiraling body and the event horizon
has a very strong influence on the inspiral time scale, which in turn has a big
impact on the gravitational wave phasing. The gravitational waves themselves
are very usefully described as ``multi-voice chirps'': the wave is a sum of
``voices'', each corresponding to a different harmonic of the fundamental
orbital frequencies. Each voice has a rather simple phase evolution. Searching
for extreme mass ratio inspirals voice-by-voice may be more effective than
searching for the summed waveform all at once.


title: LIGO's "Science Reach"

abstract:
  Technical discussions of the Laser Interferometer Gravitational Wave
Observatory (LIGO) sensitivity often focus on its effective sensitivity to
gravitational waves in a given band; nevertheless, the goal of the LIGO Project
is to ``do science.'' Exploiting this new observational perspective to explore
the Universe is a long-term goal, toward which LIGO's initial instrumentation
is but a first step. Nevertheless, the first generation LIGO instrumentation is
sensitive enough that even non-detection --- in the form of an upper limit ---
is also informative. In this brief article I describe in quantitative terms
some of the science we can hope to do with first and future generation LIGO
instrumentation: it short, the ``science reach'' of the detector we are
building and the ones we hope to build.


title:
Barrett-Crane spin foam model from generalized BF-type action for
  gravity

abstract:
  We study a generalized action for gravity as a constrained BF theory, and its
relationship with the Plebanski action. We analyse the discretization of the
constraints and the spin foam quantization of the theory, showing that it leads
naturally to the Barrett-Crane spin foam model for quantum gravity. Our
analysis holds true in both the Euclidean and Lorentzian formulation.


title: Equation of state for a classical gas of BPS black holes

abstract:
  A point particle treatment to the statistical mechanics of BPS black holes in
Einstein-Maxwell-dilaton theory is developed. Because of the absence of the
static potential, the canonical partition function for $N$ BPS black holes can
be expressed by the volume of the moduli space for them. We estimate the
equation of state for a classical gas of BPS black holes by Pad\'e
approximation and find that the result agrees with the one obtained by the
mean-field approximation.


title: The Cosmological Constant Problem and Kaluza-Klein Theory

abstract:
  We present technical results which extend previous work and show that the
cosmological constant of general relativity is an artefact of the reduction to
4D of 5D Kaluza-Klein theory (or 10D superstrings and 11D supergravity). We
argue that the distinction between matter and vacuum is artificial in the
context of ND field theory. The concept of a cosmological ``constant'' (which
measures the energy density of the vacuum in 4D) should be replaced by that of
a series of variable fields whose sum is determined by a solution of ND field
equations in a well-defined manner.


title: Vacuum in quantum liquids and in general relativity

abstract:
  Quantum liquids, in which an effective Lorentzian metric and thus some kind
of gravity gradually arise in the low-energy corner, are the objects where the
problems related to the quantum vacuum can be investigated in detail. In
particular, they provide the possible solution of the cosmological constant
problem: why the vacuum energy is by 120 orders of magnitude smaller than the
estimation from the relativistic quantum field theory. The almost complete
cancellation of the cosmological constant does not require any fine tuning and
comes from the fundamental ``trans-Planckian'' physics of quantum liquids. The
remaining vacuum energy is generated by the perturbations of quantum vacuum
caused by matter (quasiparticles), curvature, and other possible sources, such
as smooth component -- the quintessence. This provides the possible solution of
another cosmological constant problem: why the present cosmological constant is
on the order of the present matter density of the Universe. We discuss here
some properties of the quantum vacuum in quantum liquids: the vacuum energy
under different conditions; excitations above the vacuum state and the
effective acoustic metric for them provided by the motion of the vacuum;
Casimir effect, etc.


title: Static Black Holes of Metric-Affine Gravity in the Presence of Matter

abstract:
  We investigate spherically symmetric and static gravitational fields
representing black hole configurations in the framework of metric-affine gauge
theories of gravity (MAG) in the presence of different matter fields. It is
shown that in the triplet ansatz sector of MAG, black hole configurations in
the presence of non-Abelian matter fields allow the existence of black hole
hair. We analyze several cases of matter fields characterized by the presence
of hair and for all of them we show the validity of the no short hair
conjecture.


title:
Oscillatory approach to the singularity in vacuum spacetimes with $T^2$
  isometry

abstract:
  We use qualitative arguments combined with numerical simulations to argue
that, in the approach to the singularity in a vacuum solution of Einstein's
equations with $T^2$ isometry, the evolution at a generic point in space is an
endless succession of Kasner epochs, punctuated by bounces in which either a
curvature term or a twist term becomes important in the evolution equations for
a brief time. Both curvature bounces and twist bounces may be understood within
the context of local mixmaster dynamics although the latter have never been
seen before in spatially inhomogeneous cosmological spacetimes.


title: Holonomy and gravitomagnetism

abstract:
  We analyze parallel transport of a vector field around an equatorial orbit in
Kerr and stationary axisymmetric spacetimes that are reflection symmetric about
their equatorial planes. As in Schwarzschild spacetime, there is a band
structure of holonomy invariance. The new feature introduced by rotation is a
shift in the timelike component of the vector, which is the holonomic
manifestation of the gravitomagnetic clock effect.


title: On the Detection of Scalar Field Induced Spacetime Torsion

abstract:
  We argue that the geodesic hypothesis based on the autoparalllels of the
Levi-Civita connection may need refinement in the scalar- tensor theories of
gravity. Based on a reformulation of the Brans- Dicke theory in terms of a
connection with torsion determined dynamically in terms of the gradient of the
Brans-Dicke scalar field, we compute the perihelion shift in the orbit of
Mercury on the alternative hypothesis that its worldline is an autoparallel of
a connection with torsion. If the Brans-Dicke scalar field couples
significantly to matter and test particles move on such worldlines, the current
time keeping methods based on the conventional geodesic hypothesis may need
refinement.


title: Photons from quantized electric flux representations

abstract:
  The quantum theory of U(1) connections admits a diffeomorphism invariant
representation in which the electric flux through any surface is quantized.
This representation is the analog of the representation of quantum SU(2) theory
used in loop quantum gravity. We investigate the relation between this
representation, in which the basic excitations are `polymer-like', and the Fock
representation, in which the basic excitations are wave-like photons. We show
that normalizable states in the Fock space are associated with `distributional'
states in the quantized electric flux representation. This work is motivated by
the question of how wave-like gravitons in linearised gravity arise from
polymer-like states in non-perturbative loop quantum gravity.


title:
Non-Newtonian Gravity, Fluctuative Hypothesis and the Sizes of
  Astrophysical Structures

abstract:
  We show that the characteristic sizes of astrophysical and cosmological
structures, where gravity is the only overall relevant interaction assembling
the system, have a phenomenological relation to the microscopic scales whose
order of magnitude is essentially ruled by the Compton wavelength of the
proton. This result agrees with the absence of screening mechanisms for the
gravitational interaction and could be connected to the presence of Yukawa
correcting terms in the Newtonian potential which introduce typical interaction
lengths. Furthermore, we are able to justify, in a straightforward way, the
Sanders--postulated mass of a vector boson considered in order to obtain the
characteristic sizes of galaxies.


title: Poincare' invariance for continuous-time histories

abstract:
  We show that the relativistic analogue of the two types of time translation
in a non-relativistic history theory is the existence of two distinct
Poincar\'{e} groups. The `internal' Poincar\'{e} group is analogous to the one
that arises in the standard canonical quantisation scheme; the `external'
Poincar\'{e} group is similar to the group that arises in a Lagrangian
description of the standard theory. In particular, it performs explicit changes
of the spacetime foliation that is implicitly assumed in standard canonical
field theory.


title:
Quantum entropy of the Kerr black hole arising from gravitational
  perturbation

abstract:
  The quantum entropy of the Kerr black hole arising from gravitational
perturbation is investigated by using Null tetrad and \'t Hooft\'s brick-wall
model. It is shown that effect of the graviton\'s spins on the subleading
correction is dependent of the square of the spins and the angular momentum per
unit mass of the black hole, and contribution of the logarithmic term to the
entropy will be positive, zero, and negative for different value of $a/r_+$.


title: Hawking Radiation of Dirac Particles in a Variable-mass Kerr Space-time

abstract:
  Hawking effect of Dirac particles in a variable-mass Kerr space-time is
investigated by using a method called as the generalized tortoise coordinate
transformation. The location and the temperature of the event horizon of the
non-stationary Kerr black hole are derived. It is shown that the temperature
and the shape of the event horizon depend not only on the time but also on the
angle. However, the Fermi-Dirac spectrum displays a residual term which is
absent from that of Bose-Einstein distribution.


title:
Asymmetry of Hawking Radiation of Dirac Particles in a Charged Vaidya -
  de Sitter Black Hole

abstract:
  The Hawking radiation of Dirac particles in a charged Vaidya - de Sitter
black hole is investigated by using the method of generalized tortoise
coordinate transformation. It is shown that the Hawking radiation of Dirac
particles does not exist for $P_1, Q_2$ components, but for $P_2, Q_1$
components it does. Both the location and the temperature of the event horizon
change with time. The thermal radiation spectrum of Dirac particles is the same
as that of Klein-Gordon particles.


title:
A finiteness proof for the Lorentzian state sum spinfoam model for
  quantum general relativity

abstract:
  We show that the normalized Lorentzian state sum is finite on any
triangulation. It thus provides a candidate for a perturbatively finite quantum
theory of general relativity in four dimensions with Lorentzian signature.


title: Maximal Acceleration Effects in Kerr Space

abstract:
  We consider a model in which accelerated particles experience line--elements
with maximal acceleration corrections that are introduced by means of
successive approximations. It is shown that approximations higher than the
first need not be considered. The method is then applied to the Kerr metric.
The effective field experienced by accelerated test particles contains
corrections that vanish in the limit $\hbar\to 0$, but otherwise affect the
behaviour of matter greatly. The corrections generate potential barriers that
are external to the horizon and are impervious to classical particles.


title:
Compensation for thermal effects in mirrors of Gravitational Wave
  Interferometers

abstract:
  In this paper we study several means of compensating for thermal lensing
which, otherwise, should be a source of concern for future upgrades of
interferometric detectors of gravitational waves. The methods we develop are
based on the principle of heating the cold parts of the mirrors. We find that
thermal compensation can help a lot but can not do miracles. It seems finally
that the best strategy for future upgrades (``advanced configurations'') is
maybe to use thermal compensation together with another substrate materials
than Silica, for example Sapphire.


title: On the Creation of the Universe out of Nothing

abstract:
  We explain how the Universe was created with no expenditure of energy or
initial mass.


title:
Gauge invariant perturbations of Schwarzschild black holes in
  horizon-penetrating coordinates

abstract:
  We derive a geometrical version of the Regge-Wheeler and Zerilli equations,
which allows us to study gravitational perturbations on an arbitrary
spherically symmetric slicing of a Schwarzschild black hole. We explain how to
obtain the gauge-invariant part of the metric perturbations from the amplitudes
obeying our generalized Regge-Wheeler and Zerilli equations and vice-versa. We
also give a general expression for the radiated energy at infinity, and
establish the relation between our geometrical equations and the Teukolsky
formalism. The results presented in this paper are expected to be useful for
the close-limit approximation to black hole collisions, for the Cauchy
perturbative matching problem, and for the study of isolated horizons.


title: The first BritGrav meeting

abstract:
  The first British Gravity Meeting was held at the University of Southampton,
UK, on 27/28 March. 47 10-minute plenary talks were given. Here are the
abstracts in the order given. A brief conference report will also appear in
Matters of Gravity.


title:
The Lazarus project: A pragmatic approach to binary black hole
  evolutions

abstract:
  We present a detailed description of techniques developed to combine 3D
numerical simulations and, subsequently, a single black hole close-limit
approximation. This method has made it possible to compute the first complete
waveforms covering the post-orbital dynamics of a binary black hole system with
the numerical simulation covering the essential non-linear interaction before
the close limit becomes applicable for the late time dynamics. To determine
when close-limit perturbation theory is applicable we apply a combination of
invariant a priori estimates and a posteriori consistency checks of the
robustness of our results against exchange of linear and non-linear treatments
near the interface. Once the numerically modeled binary system reaches a regime
that can be treated as perturbations of the Kerr spacetime, we must
approximately relate the numerical coordinates to the perturbative background
coordinates. We also perform a rotation of a numerically defined tetrad to
asymptotically reproduce the tetrad required in the perturbative treatment. We
can then produce numerical Cauchy data for the close-limit evolution in the
form of the Weyl scalar $\psi_4$ and its time derivative $\partial_t\psi_4$
with both objects being first order coordinate and tetrad invariant. The
Teukolsky equation in Boyer-Lindquist coordinates is adopted to further
continue the evolution. To illustrate the application of these techniques we
evolve a single Kerr hole and compute the spurious radiation as a measure of
the error of the whole procedure. We also briefly discuss the extension of the
project to make use of improved full numerical evolutions and outline the
approach to a full understanding of astrophysical black hole binary systems
which we can now pursue.


title: Study of the anomalous acceleration of Pioneer 10 and 11

abstract:
  Our previous analyses of radio Doppler and ranging data from distant
spacecraft in the solar system indicated that an apparent anomalous
acceleration is acting on Pioneer 10 and 11, with a magnitude a_P ~ 8 x 10^{-8}
cm/s^2, directed towards the Sun (anderson,moriond). Much effort has been
expended looking for possible systematic origins of the residuals, but none has
been found. A detailed investigation of effects both external to and internal
to the spacecraft, as well as those due to modeling and computational
techniques, is provided. We also discuss the methods, theoretical models, and
experimental techniques used to detect and study small forces acting on
interplanetary spacecraft. These include the methods of radio Doppler data
collection, data editing, and data reduction.
  There is now further data for the Pioneer 10 orbit determination. The
extended Pioneer 10 data set spans 3 January 1987 to 22 July 1998. [For Pioneer
11 the shorter span goes from 5 January 1987 to the time of loss of coherent
data on 1 October 1990.] With these data sets and more detailed studies of all
the systematics, we now give a result, of a_P = (8.74 +/- 1.33) x 10^{-8}
cm/s^2. (Annual/diurnal variations on top of a_P, that leave a_P unchanged, are
also reported and discussed.)


title:
Properties of the quasistationary universe in context of the Big-bang
  cosmology problems

abstract:
  Old and new puzzles of cosmology are reexamined from the point of view of
quantum theory of the universe developed here. It is shown that in proposed
approach the difficulties of the standard cosmology do not arise. The theory
predicts the observed dimensions of the nonhomogeneities of matter density and
the amplitude of the fluctuations of the cosmic background radiation
temperature in the Universe and points to a new quantum mechanism of their
origin. It allows to obtain the value of the deceleration parameter which is in
good agreement with the recent SNe Ia measurements. The theory explains the
large value of entropy of the Universe and describes other parameters.


title:
Measurement of the gravitational constant $G$ in space (Project SEE):
  sensitivity to orbital parameters and space charge effect

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 space 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 meters 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. The main conclusions are that (i) the SEE concept
may allow one to measure G with an uncertainty smaller than 10^{-7} and a
progress up to 2 orders of magnitude is possible in the assessment of the
hypothetic Yukawa forces and (ii) van Allen charging of test bodies is a
problem of importance but it may be solved by the existing methods.


title: OPTIS - a satellite-based test of Special and General Relativity

abstract:
  A new satellite based test of Special and General Relativity is proposed. For
the Michelson-Morley experiment we expect an improvement of at least three
orders of magnitude, and for the Kennedy-Thorndike experiment an improvement of
more than one order of magnitude. Furthermore, an improvement by two orders of
the test of the universality of the gravitational red shift by comparison of an
atomic clock with an optical clock is projected.
  The tests are based on ultrastable optical cavities, an atomic clock and a
comb generator.


title: Self-dual gravity with topological terms

abstract:
  The canonical analysis of the (anti-) self-dual action for gravity
supplemented with the (anti-) self-dual Pontrjagin term is carried out. The
effect of the topological term is to add a `magnetic' term to the original
momentum variable associated with the self-dual action leaving the Ashtekar
connection unmodified. In the new variables, the Gauss constraint retains its
form, while both vector and Hamiltonian constraints are modified. This shows,
the contribution of the Euler and Pontrjagin terms is not the same as that
coming from the term associated with the Barbero-Immirzi parameter, and thus
the analogy between the theta-angle in Yang-Mills theory and the
Barbero-Immirzi parameter of gravity is not appropriate.


title: Consistency analysis of Kaluza-Klein geometric sigma models

abstract:
  Geometric sigma models are purely geometric theories of scalar fields coupled
to gravity. Geometrically, these scalars represent the very coordinates of
space-time, and, as such, can be gauged away. A particular theory is built over
a given metric field configuration which becomes the vacuum of the theory.
Kaluza-Klein theories of the kind have been shown to be free of the classical
cosmological constant problem, and to give massless gauge fields after
dimensional reduction. In this paper, the consistency of dimensional reduction,
as well as the stability of the internal excitations, are analyzed. Choosing
the internal space in the form of a group manifold, one meets no
inconsistencies in the dimensional reduction procedure. As an example, the
SO(n) groups are analyzed, with the result that the mass matrix of the internal
excitations necessarily possesses negative modes. In the case of coset spaces,
the consistency of dimensional reduction rules out all but the stable mode,
although the full vacuum stability remains an open problem.


title: Three-dimensional metrics as deformations of a constant curvature metric

abstract:
  Any three-dimensional Riemannian metric can be locally obtained by deforming
a constant curvature metric along one direction. The general interest of this
result, both in geometry and physics, and related open problems are stressed.


title:
Noise parametric identification and whitening for LIGO 40-meter
  interferometer data

abstract:
  We report the analysis we made on data taken by Caltech 40-meter prototype
interferometer to identify the noise power spectral density and to whiten the
sequence of noise. We concentrate our study on data taken in November 1994, in
particular we analyzed two frames of data: the 18nov94.2.frame and the
19nov94.2.frame.
  We show that it is possible to whiten these data, to a good degree of
whiteness, using a high order whitening filter. Moreover we can choose to
whiten only restricted band of frequencies around the region we are interested
in, obtaining a higher level of whiteness.


title: Dynamical Initial Conditions in Quantum Cosmology

abstract:
  Loop quantum cosmology is shown to provide both the dynamical law and initial
conditions for the wave function of a universe by one discrete evolution
equation. Accompanied by the condition that semiclassical behavior is obtained
at large volume, a unique wave function is predicted.


title: Critical Phenomena in Gravitational Collapse: The Studies So Far

abstract:
  Studies of black hole formation from gravitational collapse have revealed
interesting non-linear phenomena at the threshold of black hole formation. In
particular, in 1993 Choptuik studied the collapse of a massless scalar field
with spherical symmetry and found some behaviour, which is quite similar to the
critical phenomena well-known in {\em Statistical Mechanics} and {\em Quantum
Field Theory}. Universality and echoing of the critical solution and power-law
scaling of the black hole masses have given rise to the name {\em Critical
Phenomena in Gravitational Collapse}. Choptuik's results were soon confirmed
both numerically and semi-analytically, and have extended to various other
matter fields.
  In this paper, we shall give a brief introduction to this fascinating and
relatively new area, and provides an updated publication list. An analytical
"toy" model of critical collapse is presented, and some current investigations
are given.


title: Extra Spin-Rotation Coupling Effect in a Radiating Kerr Space-time

abstract:
  Source-less wave equations are derived for massless scalar, neutrino and
electromagnetic perturbations of a radiating Kerr space-time, and the Hawking
radiation of massless particles with spin $s =0, 1/2$ and 1 in this geometry is
investigated by using a method of the generalized tortoise coordinate
transformation. An extra interaction between the spin of particles and the
rotation of the hole displays in the thermal spectra of Hawking radiation of
massless particles with spin $s = 1/2, 1$ in the evaporating Kerr space-time.
The character of such effect is its obvious dependence on different helicity
states of particles with higher spin.


title:
Functional Schroedinger picture for conformally flat spacetime with
  cosmological constant

abstract:
  A quantum-field model of the conformally flat space is formulated using a
standard field-theoretical technique, a probability interpretation and a way to
establish the classical limit. The starting point is the following: after
conformal transformation of the Einstein -- Hilbert action, the conformal
factor represents a scalar field with the negative kinetical term and the
self-interaction inspired by the cosmological constant. (It has been found that
quanta of such action have a negative value as a sequence of the negative
energy.) The metric energy-momentum tensor of this scalar field is proportional
to the Einstein tensor for the initial metric. Therefore, a vacuum state of the
field is treated as a classical space. In such vacuum the zero mode is a scale
factor of the flat Friedmann Universe. It is shown that conformal factor may be
viewed as a an inflaton field, and its small non-homogeneities represent gauge
invariant scalar metric perturbations.


title: Chromaticity effects in microlensing by wormholes

abstract:
  Chromaticity effects introduced by the finite source size in microlensing
events by presumed natural wormholes are studied. It is shown that these
effects provide a specific signature that allow to discriminate between
ordinary and negative mass lenses through the spectral analysis of the
microlensing events. Both galactic and extragalactic situations are discussed.


title: On Radar Time and the Twin `Paradox'

abstract:
  In this paper we apply the concept of radar time (popularised by Bondi in his
work on k-calculus) to the well-known relativistic twin `paradox'. Radar time
is used to define hypersurfaces of simultaneity for a class of travelling
twins, from the `Immediate Turn-around' case, through the `Gradual Turn-around'
case, to the `Uniformly Accelerating' case. We show that this definition of
simultaneity is independent of choice of coordinates, and assigns a unique time
to any event (with which the travelling twin can send and receive signals),
resolving some common misconceptions.


title: Relativistic mechanics on rotating disk

abstract:
  We find equations of particle motion from the point of view of observer on a
rotating disk, and demonstrate that a particle moving along a rotating disk is
influenced by forces arising from geometry. They can be considered as analogs
of the centrifugal forces and the Coriolis forces.


title:
On the Effect of Constraint Enforcement on the Quality of Numerical
  Solutions in General Relativity

abstract:
  In Brodbeck et al 1999 it has been shown that the linearised time evolution
equations of general relativity can be extended to a system whose solutions
asymptotically approach solutions of the constraints. In this paper we extend
the non-linear equations in similar ways and investigate the effect of various
possibilities by numerical means. Although we were not able to make the
constraint submanifold an attractor for all solutions of the extended system,
we were able to significantly reduce the growth of the numerical violation of
the constraints. Contrary to our expectations this improvement did not imply a
numerical solution closer to the exact solution, and therefore did not improve
the quality of the numerical solution.


title: Quantum strings and black holes

abstract:
  The transition between (non supersymmetric) quantum string states and
Schwarzschild black holes is discussed. This transition occurs when the string
coupling $g^2$ (which determines Newton's constant) increases beyond a certain
critical value $g_c^2$. We review a calculation showing that self-gravity
causes a typical string state of mass $M$ to shrink, as the string coupling
$g^2$ increases, down to a compact string state whose mass, size, entropy and
luminosity match (for the critical value $g_c^2 \sim (M \sqrt{\alpha'})^{-1}$)
those of a Schwarzschild black hole. This confirms the idea (proposed by
several authors) that the entropy of black holes can be accounted for by
counting string states. The level spacing of the quantum states of
Schwarzschild black holes is expected to be exponentially smaller than their
radiative width. This makes it very difficult to conceive (even Gedanken)
experiments probing the discreteness of the quantum energy levels of black
holes.


title:
General relativity histories theory: Spacetime diffeomorphisms and the
  Dirac algebra of constraints

abstract:
  We show that representations of the group of spacetime diffeomorphism and the
Dirac algebra both arise in a phase-space histories version of canonical
general relativity. This is the general-relativistic analogue of the novel time
structure introduced previously in history theory: namely, the existence in
non-relativistic physics of two types of time translation; and the existence in
relativistic field theory of two distinct Poincare groups.


title:
Quantum nondemolition measurements of a particle in electric and
  gravitational fields

abstract:
  In this work we obtain a nondemolition variable for the case in which a
charged particle moves in the electric and gravitational fields of a spherical
body. Afterwards we consider the continuous monitoring of this nondemolition
parameter, and calculate along the ideas of the so called restricted path
integral formalism, the corresponding propagator. Using these results the
probabilities associated with the possible measurement outputs are evaluated.
The limit of our results, as the resolution of the measuring device goes to
zero, is analyzed, and the dependence of the corresponding propagator upon the
strength of the electric and gravitational fields are commented. The role that
mass plays in the corresponding results, and its possible connection with the
equivalence principle at quantum level, are studied.


title: Post-Newtonian Expansion of Gravitational Radiation

abstract:
  The post-Newtonian expansion appears to be a relevant tool for predicting the
gravitational waveforms generated by some astrophysical systems such as
binaries. In particular, inspiralling compact binaries are well-modelled by a
system of two point-particles moving on a quasi-circular orbit whose decay by
emission of gravitational radiation is described by a post-Newtonian expansion.
In this paper we summarize the basics of the computation by means of a series
of multipole moments of the exterior field generated by an isolated source in
the post-Newtonian approximation. This computation relies on an ansatz of
matching the exterior multipolar field to the inner field of a slowly-moving
source. The formalism can be applied to point-particles at the price of a
further ansatz, that the infinite self-field of point-particles can be
regularized in a certain way. As it turns out, the concept of point-particle
requires a precise definition in high post-Newtonian approximations of general
relativity.


title: Post-Newtonian Computation of Binary Inspiral Waveforms

abstract:
  Contents: I. Introduction; II. Summary of optimal signal filtering; III.
Newtonian binary polarization waveforms; IV. Newtonian orbital phase evolution;
V. Post-Newtonian wave-generation; VI. Inspiral binary waveform.


title: Gravitational Radiation and the Small-Scale Structure of Cosmic Strings

abstract:
  We calculate the gravitational radiation emitted by an infinite cosmic string
with two oppositely moving wave-trains, in the small amplitude approximation.
After comparing our result to the previously studied cases we extend the
results to a new regime where the wavelengths of the opposing wave-trains are
very different. We show that in this case the amount of power radiated vanishes
exponentially. This means that small excitations moving in only one direction
may be very long lived, and so the size of the smallest scales in a string
network might be much smaller than what one would expect from gravitational
back reaction. This result allows for a potential host of interesting
cosmological possibilities involving ultra-high energy cosmic rays, gamma ray
bursts and gravitational wave bursts.


title:
A phenomenological description of quantum-gravity-induced space-time
  noise

abstract:
  I propose a phenomenological description of space-time foam and discuss the
experimental limits that are within reach of forthcoming experiments.


title: Collapsing strange quark matter in Vaidya geometry

abstract:
  Exact solutions of the gravitational field equations for a mixture of a null
charged strange quark fluid and radiation are obtained in a Vaidya space-time.
The conditions for the formation of a naked singularity are analyzed by
considering the behavior of radial geodesics originating from the central
singularity.


title: Fermion zero modes in Painlev\'e-Gullstrand black hole

abstract:
  Painleve-Gullstrand metric of the black hole allows to discuss the fermion
zero modes inside the hole. The statistical mechanics of the fermionic
microstates can be responsible for the black hole thermodynamics. Fermion zero
modes also lead to quantization of the horizon area.


title: Nonlinear Spinor and Scalar Fields in General Relativity

abstract:
  We consider a system of nonlinear spinor and scalar fields with minimal
coupling in general relativity. The nonlinearity in the spinor field Lagrangian
is given by an arbitrary function of the invariants generated from the bilinear
spinor forms $S= {\bar \psi} \psi$ and $P=i {\bar \psi} \gamma^5 \psi$; the
scalar Lagrangian is chosen as an arbitrary function of the scalar invariant
${\Upsilon} = {\phi}_{,\alpha}{\phi}^{,\alpha}$, that becomes linear at
${\Upsilon} \to 0$. The spinor and the scalar fields in question interact with
each other by means of a gravitational field which is given by a
plane-symmetric metric. Exact plane-symmetric solutions to the gravitational,
spinor and scalar field equations have been obtained. Role of gravitational
field in the formation of the field configurations with limited total energy,
spin and charge has been investigated. Influence of the change of the sign of
energy density of the spinor and scalar fields on the properties of the
configurations obtained has been examined. It has been established that under
the change of the sign of the scalar field energy density the system in
question can be realized physically iff the scalar charge does not exceed some
critical value. In case of spinor field no such restriction on its parameter
occurs. In general it has been shown that the choice of spinor field
nonlinearity can lead to the elimination of scalar field contribution to the
metric functions, but leaving its contribution to the total energy unaltered.
  Key words: Nonlinear spinor field (NLSF), nonlinear scalar field,
plane-symmetric metric PACS: 03.65.P, 04.20.H


title: Null cone preserving maps, causal tensors and algebraic Rainich theory

abstract:
  A rank-n tensor on a Lorentzian manifold V whose contraction with n arbitrary
causal future directed vectors is non-negative is said to have the dominant
property. These tensors, up to sign, are called causal tensors, and we
determine their general properties in dimension N. We prove that rank-2 tensors
which map the null cone on itself are causal. It is known that, to any tensor A
on V there is a corresponding ``superenergy'' (s-e) tensor T{A} which always
has the dominant property. We prove that, conversely, any symmetric rank-2
tensor with the dominant property can be written in a canonical way as a sum of
N s-e tensors of simple forms. We show that the square of any rank-2 s-e tensor
is proportional to the metric if N<5, and that this holds for the s-e tensor of
any simple form for arbitrary N. Conversely, we prove that any symmetric rank-2
tensor T whose square is proportional to the metric must be, up to sign, the
s-e of a simple p-form, and that the trace of T determines the rank p of the
form. This generalises, both with respect to N and the rank p, the classical
algebraic Rainich conditions, which are necessary and sufficient conditions for
a metric to originate in some physical field, and has a geometric
interpretation: the set of s-e tensors of simple forms is precisely the set of
tensors which preserve the null cone and its time orientation. It also means
that all involutory Lorentz transformations (LT) can be represented as s-e
tensors of simple forms, and that any rank-2 s-e tensor is the sum of at most N
conformally involutory LT. Non-symmetric null cone preserving maps are shown to
have a causal symmetric part and are classified according to the null
eigenvectors of the skew-symmetric part. We thus obtain a complete
classification of all conformal LT and singular null cone preserving maps on V.


title: Properties of Bel currents

abstract:
  The Bel tensor is divergence-free in some important cases leading to the
existence of conserved currents associated to Killing vectors analogously to
those of the energy-momentum tensor. When the divergence of the Bel tensor does
not vanish one can study the interchange of some quantities between the
gravitational and other fields obtaining mixed total conserved currents.
Nevertheless, the Bel currents are shown to be conserved (independently of the
matter content) if the Killing vectors satisfy some very general conditions.
These properties are similar to some very well known statements for the
energy-momentum tensor.


title: Spherically symmetric false vacuum: no-go theorems and global structure

abstract:
  We enumerate all possible types of spacetime causal structures that can
appear in static, spherically symmetric configurations of a self-gravitating,
real, nonlinear, minimally coupled scalar field \phi in general relativity,
with an arbitrary potential V(\phi), not necessarily positive-definite. It is
shown that a variable scalar field adds nothing to the list of possible
structures with a constant \phi field, namely, Minkowski (or AdS),
Schwarzschild, de Sitter and Schwarzschild - de Sitter. It follows, in
particular, that, whatever is V(\phi), this theory does not admit regular black
holes with flat or AdS asymptotics. It is concluded that the only possible
globally regular, asymptotically flat solutions are solitons with a regular
center, without horizons and with at least partly negative potentials V(\phi).
Extension of the results to more general field models is discussed.


title: Oscillatons revisited

abstract:
  In this paper, we study some interesting properties of a spherically
symmetric oscillating soliton star made of a real time-dependent scalar field
which is called an oscillaton. The known final configuration of an oscillaton
consists of a stationary stage in which the scalar field and the metric
coefficients oscillate in time if the scalar potential is quadratic. The
differential equations that arise in the simplest approximation, that of
coherent scalar oscillations, are presented for a quadratic scalar potential.
This allows us to take a closer look at the interesting properties of these
oscillating objects. The leading terms of the solutions considering a quartic
and a cosh scalar potentials are worked in the so called stationary limit
procedure. This procedure reveals the form in which oscillatons and boson stars
may be related and useful information about oscillatons is obtained from the
known results of boson stars. Oscillatons could compete with boson stars as
interesting astrophysical objects, since they would be predicted by scalar
field dark matter models.


title: On the extension of Jackiw's scalar theory to (2+1)- dimensional gravity

abstract:
  We study some aspects of three-dimensional gravity by extending Jackiw's
scalar theory to (2+1)-dimensions and find a black hole solution. We show that
in in general this teory does not possess a Newtonian limit except for special
metric configurations.


title:
On the Riemannian and Einstein-Weyl Geometry in Theory of the Second
  Order Ordinary Differential Equations

abstract:
  Some properties of the 4-dim Riemannian spaces with metrics $$
ds^2=2(za_3-ta_4)dx^2+4(za_2-ta_3)dxdy+2(za_1-ta_2)dy^2+2dxdz+2dydt $$
associated with the second order nonlinear differential equations $$
y''+a_{1}(x,y){y'}^3+3a_{2}(x,y){y'}^2+3a_{3}(x,y)y'+a_{4}(x,y)=0 $$ with
arbitrary coefficients $a_{i}(x,y)$ and 3-dim Einstein-Weyl spaces connected
with dual equations $$ b''=g(a,b,b') $$ where the function $g(a,b,b')$
satisfied the partial differential equation $$
g_{aacc}+2cg_{abcc}+2gg_{accc}+c^2g_{bbcc}+2cgg_{bccc}+
g^2g_{cccc}+(g_a+cg_b)g_{ccc}-4g_{abc}- $$ $$
  -4cg_{bbc} -cg_{c}g_{bcc}- 3gg_{bcc}-g_cg_{acc}+
4g_cg_{bc}-3g_bg_{cc}+6g_{bb} =0 $$ are considered.


title: Three Dimensional Gravity in the Presence of Scalar Fields

abstract:
  We study a scalar field in curved space in three dimensions. We obtain a
static perturbative solution and show that this solution satisfies the exact
equations in the asymptotic region at infinity. The new solution gives rise to
a singularity in the curvature scalar at the origin. Our solution, however,
necessitates the excising the region near the origin, thus this naked
singularity is avoided.


title:
The present moment in quantum cosmology: challenges to the arguments for
  the elimination of time

abstract:
  Barbour, Hawking, Misner and others have argued that time cannot play an
essential role in the formulation of a quantum theory of cosmology. Here we
present three challenges to their arguments, taken from works and remarks by
Kauffman, Markopoulou and Newman. These can be seen to be based on two
principles: that every observable in a theory of cosmology should be measurable
by some observer inside the universe, and all mathematical constructions
necessary to the formulation of the theory should be realizable in a finite
time by a computer that fits inside the universe. We also briefly discuss how a
cosmological theory could be formulated so it is in agreement with these
principles.


title: A Proposed Absolute Entropy of Near Extremal Kerr-Newman Black Hole

abstract:
  Some problems have been found as to the definition of entropy of black hole
being applied to the extremal Kerr-Newman case, which has conflicts with the
third law of thermodynamics. We have proposed a new modification for the near
extremal one, which not only obeys the third law, but also does not conflict
with other results in black hole thermodynamics. Then we proved that the inner
horizon has temperature and proposed that the inner horizon contributes to the
entropy of the near extremal one so that the entropy of it has a modified form
and vanishes at absolute zero temperature.


title: Wheeler-DeWitt Equation with Variable Constants

abstract:
  In this paper we study how all the physical "constants" vary in the framework
described by a model in which we have taken into account the generalize
conservation principle for its stress-energy tensor. This possibility enable us
to take into account the adiabatic matter creation in order to get rid of the
entropy problem. We try to generalize this situation by contemplating
multi-fluid components. To validate all the obtained results we explore the
possibility of considering the variation of the"constants" in the quantum
cosmological scenario described by the Wheeler-DeWitt equation. For this
purpose we explore the Wheeler-DeWitt equation in different contexts but from a
dimensional point of view. We end by presenting the Wheeler-DeWitt equation in
the case of considering all the constants varying. The quantum potential is
obtained and the tunneling probability is studied.


title: Back-reaction of Quantum fields in an Einstein Universe

abstract:
  We study the back-reaction effects of the finite-temperature scalar field and
the photon field in the background of an Einstein universe. In each case we
find a relation between the temperature of the universe and its radius. These
relations exhibit a minimum radius below which no self-consistent solution for
the Einstein field equation can be found. A maximum temperature marks the
transition from the vacuum dominated era to the radiation dominated era. An
interpretation to this behavior in terms of Bose-Einstein condensation in the
case of the scalar field is given.


title:
Measurement of the Relativistic Potential Difference Across a Rotating
  Dielectric Cylinder

abstract:
  According to the Special Theory of Relativity, a rotating magnetic dielectric
cylinder in an axial magnetic field should exhibit a contribution to the radial
electric potential that is associated with the motion of the material's
magnetic dipoles. In 1913 Wilson and Wilson reported a measurement of the
potential difference across a magnetic dielectric constructed from wax and
steel balls. Their measurement has long been regarded as a verification of this
prediction. In 1995 Pelligrini and Swift questioned the theoretical basis of
experiment. In particular, they pointed out that it is not obvious that a
rotating medium may be treated as if each point in the medium is locally
inertial. They calculated the effect in the rotating frame and predicted a
potential different from both Wilson's theory and experiment. Subsequent
analysis of the experiment suggests that Wilson's experiment does not
distinguish between the two predictions due to the fact that their composite
steel-wax cylinder is conductive in the regions of magnetization. We report
measurements of the radial voltage difference across various rotating
dielectric cylinders, including a homogeneous magnetic material (YIG), to
unambiguously test the competing calculations. Our results are compatible with
the traditional treatment of the effect using a co-moving locally inertial
reference frame, and are incompatible with the predictions based on the model
of Pelligrini and Swift.


title: Teleparallel Spin Connection

abstract:
  A new expression for the spin connection of teleparallel gravity is proposed,
given by minus the contorsion tensor plus a zero connection. The corresponding
minimal coupling is covariant under local Lorentz transformation, and
equivalent to the minimal coupling prescription of general relativity. With
this coupling prescription, therefore, teleparallel gravity turns out to be
fully equivalent to general relativity, even in the presence of spinor fields.


title:
Causality, shocks and instabilities in vector field models of Lorentz
  symmetry breaking

abstract:
  We show that that vector field-based models of the ether generically do not
have a Hamiltonian that is bounded from below in a flat spacetime. We also
demonstrate that these models possess multiple light cones in flat or curved
spacetime, and that the non-lightlike characteristic is associated with an
ether degree of freedom that will tend to form shocks. Since the field
equations (and propagation speed) of this mode is singular when the timelike
component of the ether vector field vanishes, we demonstrate that linearized
analyses about such configurations cannot be trusted to produce robust
approximations to the theory.


title:
Perturbed Spherically Symmetric Dust Solution of the Field Equations in
  Observational Coordinates with Cosmological Data Functions

abstract:
  Using the framework for solving the spherically symmetric field equations in
observational coordinates given in Araujo and Stoeger (1999), their formulation
and solution in the perturbed FLRW sperically symmetric case with observational
data representing galaxy redshifts, number counts and observer area distances,
both as functions of redshift on our past light cone, are presented. The
importance of the central conditions, those which must hold on our world line
C, is emphasized. In detailing the solution for these perturbations, we discuss
the gauge problem and its resolution in this context, as well as how errors and
gaps in the data are propagated together with the genuine perturbations. This
will provide guidance for solving, and interpreting the solutions of the more
complicated general perturbation problem with observational data on our past
light cone.


title: Detectability of Cosmic Topology in Almost Flat Universes

abstract:
  Recent observations suggest that the ratio of the total density to the
critical density of the universe, $\Omega_0$, is likely to be very close to
one, with a significant proportion of this energy being in the form of a dark
component with negative pressure. Motivated by this result, we study the
question of observational detection of possible non-trivial topologies in
universes with $\Omega_0 \sim 1$, which include a cosmological constant. Using
a number of indicators we find that as $\Omega_0 \to 1$, increasing families of
possible manifolds (topologies) become either undetectable or can be excluded
observationally. Furthermore, given a non-zero lower bound on $|\Omega_0 - 1|$,
we can rule out families of topologies (manifolds) as possible candidates for
the shape of our universe. We demonstrate these findings concretely by
considering families of topologies and employing bounds on cosmological
parameters from recent observations. We find that given the present bounds on
cosmological parameters, there are families of both hyperbolic and spherical
manifolds that remain undetectable and families that can be excluded as the
shape of our universe. These results are of importance in future search
strategies for the detection of the shape of our universe, given that there are
an infinite number of theoretically possible topologies and that the future
observations are expected to put a non-zero lower bound on $|\Omega_0 - 1|$
which is more accurate and closer to zero.


title: Spherical Structures in the Inflationary Cosmology

abstract:
  It has been suggested that wormholes and other non-trivial geometrical
structures might have been formed during the quantum cosmological era ($t\sim
10^{-43}$s). Subsequent inflation of the universe might have enlarged these
structures to macroscopic sizes. In this paper, spherical geometrical
structures in an inflationary RW background are derived from the Einstein
equations, using a constraint on the energy-momentum tensor which is an
extension of the one expected for inflation. The possibility of dynamical
wormholes and other spherical structures are explored in the framework of the
solutions.


title: Electrostatic boundary value problems in the Schwarzschild background

abstract:
  The electrostatic potential of any test charge distribution in Schwarzschild
space with boundary values is derived. We calculate the Green's function,
generalize the second Green's identity for p-forms and find the general
solution. Boundary value problems are solved. With a multipole expansion the
asymptotic property for the field of any charge distribution is derived. It is
shown that one produces a Reissner--Nordstrom black hole if one lowers a test
charge distribution slowly toward the horizon. The symmetry of the distribution
is not important. All the multipole moments fade away except the monopole. A
calculation of the gravitationally induced electrostatic self-force on a
pointlike test charge distribution held stationary outside the black hole is
presented.


title: Topology of spacetime and quantization of particle dynamics

abstract:
  We compare classical and quantum dynamics of a particle in the de Sitter
spacetimes with different topologies to show that the result of quantization
strongly depends on global properties of a classical system. We present
essentially self-adjoint representations of the algebra of observables for each
system. Quantization based on global properties of a classical system accounts
properly its symmetries.


title: Discrete Symmetries in Translation Invariant Cosmological Models

abstract:
  In this paper we investigate a class of (d+1) dimensional cosmological models
with a cosmological constant possessing an R^d simply transitive symmetry group
and show that it can be written in a form that manifests the effect of a
permutation symmetry. We investigate the solution orbifold and calculate the
probability of a certain number of dimensions that will expand or contract. We
use this to calculate the probabilities up to dimension d=5.


title: Infinite Kinematic Self-Similarity and Perfect Fluid Spacetimes

abstract:
  Perfect fluid spacetimes admitting a kinematic self-similarity of infinite
type are investigated. In the case of plane, spherically or hyperbolically
symmetric space-times the field equations reduce to a system of autonomous
ordinary differential equations. The qualitative properties of solutions of
this system of equations, and in particular their asymptotic behavior, are
studied. Special cases, including some of the invariant sets and the geodesic
case, are examined in detail and the exact solutions are provided. The class of
solutions exhibiting physical self-similarity are found to play an important
role in describing the asymptotic behavior of the infinite kinematic
self-similar models.


title: Particles on a Circle in Canonical Lineal Gravity

abstract:
  A description of the canonical formulation of lineal gravity minimally
coupled to N point particles in a circular topology is given. The Hamiltonian
is found to be equal to the time-rate of change of the extrinsic curvature
multiplied by the proper circumference of the circle. Exact solutions for pure
gravity and for gravity coupled to a single particle are obtained. The presence
of a single particle significantly modifies the spacetime evolution by either
slowing down or reversing the cosmological expansion of the circle, depending
upon the choice of parameters.


title: Metric-based Hamiltonians, null boundaries, and isolated horizons

abstract:
  We extend the quasilocal (metric-based) Hamiltonian formulation of general
relativity so that it may be used to study regions of spacetime with null
boundaries. In particular we use this generalized Brown-York formalism to study
the physics of isolated horizons. We show that the first law of isolated
horizon mechanics follows directly from the first variation of the Hamiltonian.
This variation is not restricted to the phase space of solutions to the
equations of motion but is instead through the space of all (off-shell)
spacetimes that contain isolated horizons. We find two-surface integrals
evaluated on the horizons that are consistent with the Hamiltonian and which
define the energy and angular momentum of these objects. These are closely
related to the corresponding Komar integrals and for Kerr-Newman spacetime are
equal to the corresponding ADM/Bondi quantities. Thus, the energy of an
isolated horizon calculated by this method is in agreement with that recently
calculated by Ashtekar and collaborators but not the same as the corresponding
quasilocal energy defined by Brown and York. Isolated horizon mechanics and
Brown-York thermodynamics are compared.


title: Observables of D=4 Euclidean Supergravity and Dirac Eigenvalues

abstract:
  Results on the observables of the Euclidean supergravity in terms of the
Dirac eigenvalues are briefly revisited.


title: Decoherence of gauge-invariant metric fluctuations during inflation

abstract:
  I study the gauge-invariant fluctuations of the metric during inflation. In
the infrared sector the metric fluctuations can be represented by a
coarse-grained field. We can write a Schroedinger equation for the
coarse-grained metric fluctuations which is related to an effective Hamiltonian
for a time dependent parameter of mass harmonic oscillator with a stochastic
external force. I study the wave function for a power-law expanding universe. I
find that the phase space of the quantum state for super Hubble scalar metric
perturbations loses its coherence at the end of inflation. This effect is a
consequence of interference between the super Hubble metric perturbations and
its canonical conjugate variable, which is produced by the interaction of the
coarse-grained scalar metric fluctuation with the environment.


title:
Anisotropic fluids in the case of stationary and axisymmetric spaces of
  General Relativity

abstract:
  We present a stationary axisymmetric solution belonging to Carter's family
[A] of spaces and representing an anisotropic fluid configuration.


title: Gravity-induced entropy in the quantum motion of a macroscopic body

abstract:
  It is shown that a recently proposed model for the gravitational interaction
in non relativistic quantum mechanics may turn to be relevant to the derivation
of the second law of thermodynamics. In particular, the spreading of the
probability density of the center of mass of an isolated macroscopic body does
not imply delocalization of the wave function, but on the contrary it
corresponds to an entropy growth.


title:
Testing General Relativity with LAGEOS, LAGEOS II and Ajisai
  laser-ranged satellites

abstract:
  The accuracy reached in the past few years by Satellite Laser Ranging (SLR)
allows for measuring even tiny features of the Earth's gravitational field
predicted by Einstein's General Relativity by means of artificial satellites.
The gravitomagnetic dragging of the orbit of a test body is currently under
measurement by analyzing a suitable combination of the orbital residuals of
LAGEOS and LAGEOS II. The lower bound of the error in this experiment amount to
12.92%. It is due to the mismodeling in the even zonal harmonics of the
geopotential which are the most important sources of systematic error. A
similar approach could be used in order to measure the relativistic
gravitoelectric pericenter shift in the field of the Earth with a lower bound
of the systematic relative error of 0.6% due to the even zonal harmonics as
well. The inclusion of the ranging data to the Japanese passive geodetic
satellite Ajisai would improve such limits to 10.78% and 0.08% respectively and
would allow to improve the accuracy in the determination of the PPN parameters
beta and gamma.

categories: gr-qc astro-ph physics.geo-ph physics.space-ph


title: Moments of inertia of relativistic magnetized stars

abstract:
  We consider principal moments of inertia of axisymmetric, magnetically
deformed stars in the context of general relativity. The general expression for
the moment of inertia with respect to the symmetric axis is obtained. The
numerical estimates are derived for several polytropic stellar models. We find
that the values of the principal moments of inertia are modified by a factor of
2 at most from Newtonian estimates.


title: Radiative falloff in Einstein-Straus spacetime

abstract:
  The Einstein-Straus spacetime describes a nonrotating black hole immersed in
a matter-dominated cosmology. It is constructed by scooping out a spherical
ball of the dust and replacing it with a vacuum region containing a black hole
of the same mass. The metric is smooth at the boundary, which is comoving with
the rest of the universe. We study the evolution of a massless scalar field in
the Einstein-Straus spacetime, with a special emphasis on its late-time
behavior. This is done by numerically integrating the scalar wave equation in a
double-null coordinate system that covers both portions (vacuum and dust) of
the spacetime. We show that the field's evolution is governed mostly by the
strong concentration of curvature near the black hole, and the discontinuity in
the dust's mass density at the boundary; these give rise to a rather complex
behavior at late times. Contrary to what it would do in an asymptotically-flat
spacetime, the field does not decay in time according to an inverse power-law.


title:
Statistical mechanics and the description of the early universe I.:
  Foundations for a slightly non-extensive cosmology

abstract:
  We analyze how the thermal history of the universe is influenced by the
statistical description, assuming a deviation from the usual Bose-Einstein,
Fermi-Dirac and Boltzmann-Gibbs distribution functions. These deviations
represent the possible appearance of non-extensive effects related with the
existence of long range forces, memory effects, or evolution in fractal or
multi-fractal space. In the early universe, it is usually assumed that the
distribution functions are the standard ones. Then, considering the evolution
in a larger theoretical framework will allow to test this assumption and to
place limits to the range of its validity. The corrections obtained will change
with temperature, and consequently, the bounds on the possible amount of
non-extensivity will also change with time. We generalize results which can be
used in other contexts as well, as the Boltzmann equation and the Saha law, and
provide an estimate on how known cosmological bounds on the masses of neutrinos
are modified by a change in the statistics. We particularly analyze here the
recombination epoch, making explicit use of the chemical potentials involved in
order to attain the necessary corrections. All these results constitute the
basic tools needed for placing bounds on the amount of non-extensivity that
could be present at different eras and will be later used to study primordial
nucleosynthesis.


title:
Statistical mechanics and the description of the early universe II.
  Principle of detailed balance and primordial 4He formation

abstract:
  If the universe is slightly non-extensive, and the distribution functions are
not exactly given by those of Boltzmann-Gibbs, the primordial production of
light elements will be non-trivially modified. In particular, the principle of
detailed balance (PDB), of fundamental importance in the standard analytical
analysis, is no longer valid, and a non-extensive correction appears. This
correction is computed and its influence is studied and compared with previous
works, where, even when the universe was considered as an slightly
non-extensive system, the PDB was assumed valid. We analytically track the
formation of Helium and Deuterium, and study the kind of deviation one could
expect from the standard regime. The correction to the capture time, the moment
in which Deuterium can no longer be substantially photo-disintegrated, is also
presented. This allows us to take into account the process of the free decay of
neutrons, which was absent in all previous treatments of the topic. We show
that even when considering a first (linear) order correction in the quantum
distribution functions, the final output on the primordial nucleosynthesis
yields cannot be reduced to a linear correction in the abundances. We finally
obtain new bounds upon the non-extensive parameter, both comparing the range of
physical viability of the theory, and using the latest observational data.


title:
Gravitational collapse of spherically symmetric perfect fluid with
  kinematic self-similarity

abstract:
  Analytic spherically symmetric solutions of the Einstein field equations
coupled with a perfect fluid and with self-similarities of the zeroth, first
and second kinds, found recently by Benoit and Coley [Class. Quantum Grav. {\bf
15}, 2397 (1998)], are studied, and found that some of them represent
gravitational collapse. When the solutions have self-similarity of the first
(homothetic) kind, some of the solutions may represent critical collapse but in
the sense that now the "critical" solution separates the collapse that forms
black holes from the collapse that forms naked singularities. The formation of
such black holes always starts with a mass gap, although the "critical"
solution has homothetic self-similarity. The solutions with self-similarity of
the zeroth and second kinds seem irrelevant to critical collapse. Yet, it is
also found that the de Sitter solution is a particular case of the solutions
with self-similarity of the zeroth kind, and that the Schwarzschild solution is
a particular case of the solutions with self-similarity of the second kind with
the index $\alpha = 3/2$.


title: Comparison of advanced gravitational-wave detectors

abstract:
  We compare two advanced designs for gravitational-wave antennas in terms of
their ability to detect two possible gravitational wave sources. Spherical,
resonant mass antennas and interferometers incorporating resonant sideband
extraction (RSE) were modeled using experimentally measurable parameters. The
signal-to-noise ratio of each detector for a binary neutron star system and a
rapidly rotating stellar core were calculated. For a range of plausible
parameters we found that the advanced LIGO interferometer incorporating RSE
gave higher signal-to-noise ratios than a spherical detector resonant at the
same frequency for both sources. Spheres were found to be sensitive to these
sources at distances beyond our galaxy. Interferometers were sensitive to these
sources at far enough distances that several events per year would be expected.


title:
Nonrelativistic field theoretic setting for gravitational
  self-interactions

abstract:
  It is shown that a recently proposed model for the gravitational interaction
in non relativistic quantum mechanics is the instantaneous action at a distance
limit of a field theoretic model containing a negative energy field. It reduces
to the Schroedinger-Newton theory in a suitable mean field approximation. While
both the exact model and its approximation lead to estimates for localization
lengths, only the former gives rise to an explicit non unitary dynamics
accounting for the emergence of the classical behavior of macroscopic bodies.


title: General Relativity, the Cosmological Constant and Modular Forms

abstract:
  Strong field (exact) solutions of the gravitational field equations of
General Relativity in the presence of a Cosmological Constant are investigated.
In particular, a full exact solution is derived within the inhomogeneous
Szekeres-Szafron family of space-time line element with a nonzero Cosmological
Constant. The resulting solution connects, in an intrinsic way, General
Relativity with the theory of modular forms and elliptic curves. The
homogeneous FLRW limit of the above space-time elements is recovered and we
solve exactly the resulting Friedmann Robertson field equation with the
appropriate matter density for generic values of the Cosmological Constant
%Lambda and curvature constant K. A formal expression for the Hubble constant
is derived. The cosmological implications of the resulting non-linear solutions
are systematically investigated. Two particularly interesting solutions i) the
case of a flat universe K=0, Lambda not= 0 and ii) a case with all three
cosmological parameters non-zero, are described by elliptic curves with the
property of complex multiplication and absolute modular invariant j=0 and 1728,
respectively. The possibility that all non-linear solutions of General
Relativity are expressed in terms of theta functions associated with
Riemann-surfaces is discussed.


title: On uniqueness of static Einstein-Maxwell-dilaton black holes

abstract:
  We prove uniqueness of static, asymptotically flat spacetimes with
non-degenerate black holes for three special cases of Einstein-Maxwell-dilaton
theory: For the coupling ``$\alpha = 1$'' (which is the low energy limit of
string theory) on the one hand, and for vanishing magnetic or vanishing
electric field (but arbitrary coupling) on the other hand. Our work generalizes
in a natural, but non-trivial way the uniqueness result obtained by
Masood-ul-Alam who requires both $\alpha = 1$ and absence of magnetic fields,
as well as relations between the mass and the charges. Moreover, we simplify
Masood-ul-Alam's proof as we do not require any non-trivial extensions of
Witten's positive mass theorem. We also obtain partial results on the
uniqueness problem for general harmonic maps.


title: Quantum black hole inflation

abstract:
  In this paper we follow a new approach for particle creation by a localized
strong gravitational field. The approach is based on a definition of the
physical vacuum drawn from Heisenberg uncertainty principle. Using the fact
that the gravitational field red-shifts the frequency modes of the vacuum, a
condition on the minimum stregth of the gravitational field required to achieve
real particle creation is derived. Application of this requirement on a
Schwartzchid black hole resulted in deducing an upper limit on the region,
outside the event horizon, where real particles can be created. Using this
regional upper limit, and considering particle creation by black holes as a
consequence of the Casimir effect, with the assumption that the created quanta
are to be added to the initial energy, we deduce a natural power law for the
development of the event horizon, and consequently a logarithmic law for the
area spectrum of an inflating black hole. Application of the results on a
cosmological model shows that if we start with a Planck-dimensional black hole,
then through the process of particle creation we end up with a universe having
the presently estimated critical density. Such a universe will be in a state of
eternal inflation.


title: Charge conservation and Equivalence principle

abstract:
  The $TH\epsilon\mu$ formalism was developed to study nonmetric theories of
gravitation. In this letter we show that theories that violate Local Lorentz
Invariance (LLI) or Local Position Invariance (LPI) also violate charge
conservation. Using upper bounds on this violation we can put very stringent
limits to violations of Einstein Equivalence Principle (EEP). These limits, in
turn, severely restrict string-based models of low energy physics.


title: The Cosmic Microwave Background and Scalar-Tensor Theories of Gravity

abstract:
  We show that if all observers see an isotropic cosmic microwave background in
an expanding geodesic perfect fluid spacetime within a scalar-tensor theory of
gravity, then that spacetime must be isotropic and spatially homogeneous. This
result generalizes the Ehlers-Geren-Sachs Theorem of General Relativity, and
serves to underpin the important result that any evolving cosmological model in
a scalar-tensor theory that is compatible with observations must be almost
Friedmann-Lemaitre-Robertson-Walker.


title: Cosmological Models With Variable G an Lambda and Bulk viscosity

abstract:
  We have analyzed a nonsingular model with a variable cosmological term
following the Carvalho {\it et al}. ansatz. The model was shown to approximate
to the model of Freese {\it et al}. in one direction and to the \"{O}zer-Taha
in the other. We have then included the effect of viscosity in this cosmology,
as this effect has not been considered before. The analysis showed that this
viscous effect could be important with a present contribution to the cosmic
pressure, at most, of order of that of radiation. The model puts a stronger
upper bound on the baryonic matter than that required by the standard model. A
variable gravitational and cosmological constant were then introduced in a
scenario which conserves the energy and momentum in the presence of bulk
viscosity. The result of the analysis reveals that various models could be
viscous. A noteworthy result is that some nonsingular closed models evolve
asymptotically into a singular viscous one. The considered models solve for
many of the standard model problems. Though the introduction of bulk viscosity
results in the creation of particles, this scenario conserves energy and
momentum. As in the standard model the entropy remains constant. We have not
explained the generation of bulk viscosity but some workers attributes this to
neutrinos. Though the role of viscosity today is minute it could, nevertheless,
have had an important contribution at early times. We have shown that these
models encompass many of the old and recently proposed models, in particular,
Brans-Dicke, Dirac, Freese {\it et al}., Berman, Abdel Rahman and Kalligas {\it
et al}. models. Hence we claim that the introduction of bulk viscosity enriches
the adopted cosmology.


title:
On the Detection of a Scalar Stochastic Background of Gravitational
  Waves

abstract:
  In the near future we will witness the coming to a full operational regime of
laser interferometers and resonant mass detectors of spherical shape. In this
work we study the sensitivity of pairs of such gravitational wave detectors to
a scalar stochastic background of gravitational waves. Our computations are
carried out both for minimal and non minimal coupling of the scalar fields.


title:
Solving the characteristic initial value problem for colliding plane
  gravitational and electromagnetic waves

abstract:
  A method is presented for solving the characteristic initial value problem
for the collision and subsequent nonlinear interaction of plane gravitational
or gravitational and electromagnetic waves in a Minkowski background. This
method generalizes the monodromy transform approach to fields with nonanalytic
behaviour on the characteristics inherent to waves with distinct wave fronts.
The crux of the method is in a reformulation of the main nonlinear symmetry
reduced field equations as linear integral equations whose solutions are
determined by generalized (``dynamical'') monodromy data which evolve from data
specified on the initial characteristics (the wavefronts).


title:
Exact Charged 2-Body Motion and the Static Balance Condition in Lineal
  Gravity

abstract:
  We find an exact solution to the charged 2-body problem in $(1+1)$
dimensional lineal gravity which provides the first example of a relativistic
system that generalizes the Majumdar-Papapetrou condition for static balance.


title:
Extending the lifetime of 3D black hole computations with a new
  hyperbolic system of evolution equations

abstract:
  We present a new many-parameter family of hyperbolic representations of
Einstein's equations, which we obtain by a straightforward generalization of
previously known systems. We solve the resulting evolution equations
numerically for a Schwarzschild black hole in three spatial dimensions, and
find that the stability of the simulation is strongly dependent on the form of
the equations (i.e. the choice of parameters of the hyperbolic system),
independent of the numerics. For an appropriate range of parameters we can
evolve a single 3D black hole to $t \simeq 600 M$ -- $1300 M$, and are
apparently limited by constraint-violating solutions of the evolution
equations. We expect that our method should result in comparable times for
evolutions of a binary black hole system.


title:
Boundary conditions from boundary terms, Noether charges and the trace K
  lagrangian in general relativity

abstract:
  We present the Lagrangian whose corresponding action is the trace K action
for General Relativity. Although this Lagrangian is second order in the
derivatives, it has no second order time derivatives and its behaviour at space
infinity in the asymptotically flat case is identical to other alternative
Lagrangians for General Relativity, like the gamma-gamma Lagrangian used by
Einstein. We develop some elements of the variational principle for field
theories with boundaries, and apply them to second order Lagrangians, where we
stablish the conditions -- proposition 1 -- for the conservation of the Noether
charges. From this general approach a pre-symplectic form is naturally obtained
that features two terms, one from the bulk and another from the boundary. When
applied to the trace K Lagrangian, we recover a pre-symplectic form first
introduced using a different approach. We prove that all diffeomorphisms
satisfying certain restrictions at the boundary -- that keep room for a
realization of the Poincar\'e group -- will yield Noether conserved charges. In
particular, the computation of the total energy gives, in the asymptotically
flat case, the ADM result.


title: Detection of Impulsive Light-Like Signals in General Relativity

abstract:
  The principal purpose of this paper is to study the effect of an impulsive
light-like signal on neighbouring test particles. Such a signal can in general
be unambiguously decomposed into a light-like shell of null matter and an
impulsive gravitational wave. Our results are: (a) If there is anisotropic
stress in the light-like shell then test particles initially moving in the
signal front are displaced out of this 2-surface after encountering the signal;
(b) For a light-like shell with no anisotropic stress accompanying a
gravitational wave the effect of the signal on test particles moving in the
signal front is to displace them relative to each other with the usual
distortion due to the gravitational wave diminished by the presence of the
light-like shell. An explicit example for a plane-fronted signal is worked out.


title: S-matrix for s-wave gravitational scattering

abstract:
  In the s-wave approximation the 4D Einstein gravity with scalar fields can be
reduced to an effective 2D dilaton gravity coupled nonminimally to the matter
fields. We study the leading order (tree level) vertices. The 4-particle matrix
element is calculated explicitly. It is interpreted as scattering with
formation of a virtual black hole state. As one novel feature we predict the
gravitational decay of s-waves.


title:
Anomalies In The beta-decay Processes And The Pulse Strong-Current
  Discharges As Consequence Of Electron Gravitational Emission

abstract:
  Parity nonconservation in the beta-decay processes is considered as
fundamental property of weak interactions. Nevertheless, this property can be
treated as anomaly, because in fundamental interactions of the rest types
parity is conserved. Analogously, anomaly in the short-duration strong-current
pulse discharges is well known. The essence of this phenomenon consists in
generation of local high-temperature plasma formations (LHTF) with the typical
values of its thermodynamical parameters exceeding those related to the central
section of a discharge. In this paper, an attempt is undertaken to treat these
anomalies as manifestation of fundamental properties of gravitational emission.
Some consequences of this assumption can be tested in the beta-decay
experiments as well as in the experiments with short-duration z-pinch-type
pulse discharges.


title: On the anomalies of gravity

abstract:
  The paper is based on the recently proposed 4-dimensional optical space
theory and draws some of its consequences for gravitation. Starting with the
discussion of central movement, the paper proceeds to establish the a metric
compatible with Newtonian mechanics which can be accommodated by the new theory
and finds a correction term which can be neglected in most practical
circumstances. Being effective in the very short range, the correction term
affects substantially the results when continuous mass distributions are
considered. The main consequence is the possibility of explaining the orbital
speeds found around galaxies, without the need to appeal for a lot of dark
matter. The speed of gravity is also discussed and the theory is found
compatible with a gravitational speed equal to the speed of light. On the
subject of black holes, it is suggested that they are just a possibility but
not a geometric inevitability.


title: Scaling Solutions and reconstruction of Scalar Field Potentials

abstract:
  Starting from the hypothesis of scaling solutions, the general exact form of
the scalar field potential is found. In the case of two fluids, it turns out to
be a negative power of hyperbolic sine. In the case of three fluids the
analytic form is not found, but is obtained by quadratures.


title:
Dimensional regularization of the gravitational interaction of point
  masses

abstract:
  We show how to use dimensional regularization to determine, within the
Arnowitt-Deser-Misner canonical formalism, the reduced Hamiltonian describing
the dynamics of two gravitationally interacting point masses. Implementing, at
the third post-Newtonian (3PN) accuracy, our procedure we find that dimensional
continuation yields a finite, unambiguous (no pole part) 3PN Hamiltonian which
uniquely determines the heretofore ambiguous ``static'' parameter: namely,
$\omega_s=0$. Our work also provides a remarkable check of the perturbative
consistency (compatibility with gauge symmetry) of dimensional continuation
through a direct calculation of the ``kinetic'' parameter $\omega_k$, giving
the unique answer compatible with global Poincar\'e invariance
($\omega_k={41/24}$) by summing $\sim50$ different dimensionally continued
contributions.


title:
More on Tanaka-Tagoshi Parametrization of post-1PN Spin-Free
  Gravitational Wave Chirps: Equispaced and Cardinal Interpolated Lattices

abstract:
  The conclusions obtained in gr-qc/0101067 are shown to be valid also if the
full 2.5PN expansion of the chirp phase is used.


title: Gravitational self force by mode sum regularization

abstract:
  We propose a practical scheme for calculating the local gravitational
self-force experienced by a test mass particle moving in a black hole
spacetime. The method---equally effective for either weak or strong field
orbits---employs the {\em mode-sum regularization scheme} previously developed
for a scalar toy model. The starting point for the calculation, in this
approach, is the formal expression for the regularized self-force derived by
Mino et al. (and, independently, by Quinn and Wald), which involves a worldline
integral over the tail part of the retarded Green's function. This force is
decomposed into multipole (tensor harmonic) modes, whose sum is subjected to a
carefully designed regularization procedure. This procedure involves an
analytic derivation of certain ``regularization parameters'' by means of a
local analysis of the Green's function. This manuscript contains the following
main parts: (1) Introduction of the mode sum scheme as applied to the
gravitational case. (2) Two simple cases studied: the test case of a static
particle in flat spacetime, and the case of a particle at a turning point of a
radial geodesic in Schwarzschild spacetime. In both cases we derive all
necessary regularization parameters. (3) An Analytic foundation is set for
applying the scheme in more general cases. (In this paper, the mode sum scheme
is formulated within the harmonic gauge. The implementation of the scheme in
other gauges shall be discussed in a separate, forthcoming paper.)


title: Null Geodesics in Five Dimensional Manifolds

abstract:
  We analyze a class of 5D non-compact warped-product spaces characterized by
metrics that depend on the extra coordinate via a conformal factor. Our model
is closely related to the so-called canonical coordinate gauge of Mashhoon et
al. We confirm that if the 5D manifold in our model is Ricci-flat, then there
is an induced cosmological constant in the 4D sub-manifold. We derive the
general form of the 5D Killing vectors and relate them to the 4D Killing
vectors of the embedded spacetime. We then study the 5D null geodesic paths and
show that the 4D part of the motion can be timelike -- that is, massless
particles in 5D can be massive in 4D. We find that if the null trajectories are
affinely parameterized in 5D, then the particle is subject to an anomalous
acceleration or fifth force. However, this force may be removed by
reparameterization, which brings the correct definition of the proper time into
question. Physical properties of the geodesics -- such as rest mass variations
induced by a variable cosmological ``constant'', constants of the motion and 5D
time-dilation effects -- are discussed and are shown to be open to experimental
or observational investigation.


title:
Backscattering of electromagnetic and gravitational waves off
  Schwarzschild geometry

abstract:
  Major changes in Sec. II (with much stronger estimates), minor changes in
remaining sections, a new title. Deleted Appendix, added 2 new references.


title:
Extreme objects with arbitrary large mass, or density, and arbitrary
  size

abstract:
  We consider a generalization of the interior Schwarzschild solution that we
match to the exterior one to build global C^1 models that can have arbitrary
large mass, or density, with arbitrary size. This is possible because of a new
insight into the problem of localizing the center of symmetry of the models and
the use of principal transformations to understand the structure of space.


title: Many accelerating black holes

abstract:
  We show how the Weyl formalism allows metrics to be written down which
correspond to arbitrary numbers of collinear accelerating neutral black holes
in 3+1 dimensions. The black holes have arbitrary masses and different
accelerations and share a common acceleration horizon. In the general case, the
black holes are joined by cosmic strings or struts that provide the necessary
forces that, together with the inter black hole gravitational attractions,
produce the acceleration. In the cases of two and three black holes, the
parameters may be chosen so that the outermost black hole is pulled along by a
cosmic string and the inner black holes follow behind accelerated purely by
gravitational forces. We conjecture that similar solutions exist for any number
of black holes.