title: The warp drive and antigravity

abstract:
  The warp drive envisioned by Alcubierre that can move a spaceship faster than
light can, with modification, levitate it as if it were lighter than light,
even allow it to go below a black hole's horizon and return unscathed.
Wormhole-like versions of the author's `drainhole' (1973) might provide the
drive, in the form of a by-pass of the spaceship composed of a multitude of
tiny topological tunnels. The by-pass would divert the gravitational `ether'
into a sink covering part of the spaceship's hull, connected by the tunnels to
a source covering the remainder of the hull, to produce an ether flow like that
of a river that disappears underground only to spring forth at a point
downstream. This diversion would effectively shield the spaceship from external
gravity.


title: Asymmetric brane-worlds with induced gravity

abstract:
  The Randall-Sundrum scenario, with a 1+3-dimensional brane in a 5-dimensional
bulk spacetime, can be generalized in various ways. We consider the case where
the Z2-symmetry at the brane is relaxed, and in addition the gravitational
action is generalized to include an induced gravity term on the brane. We
derive the complete set of equations governing the gravitational dynamics for a
general brane and bulk, and identify how the asymmetry and the induced gravity
act as effective source terms in the projected field equations on the brane.
For a Friedmann brane in an anti de Sitter bulk, the solution of the Friedmann
equation is given by the solution of a quartic equation. We find the
perturbative solutions for small asymmetry, which has an effect at late times.


title: Spinning particles in the vacuum C metric

abstract:
  The motion of a spinning test particle given by the Mathisson-Papapetrou
equations is studied on an exterior vacuum C metric background spacetime
describing the accelerated motion of a spherically symmetric gravitational
source. We consider circular orbits of the particle around the direction of
acceleration of the source. The symmetries of this configuration lead to the
reduction of the differential equations of motion to algebraic relations. The
spin supplementary conditions as well as the coupling between the spin of the
particle and the acceleration of the source are discussed.


title: Cartan's equivalence method and null coframes in General Relativity

abstract:
  Using Cartan's equivalence method for point transformations we obtain from
first principles the conformal geometry associated with third order ODEs and a
special class of PDEs in two dimensions. We explicitly construct the null
tetrads of a family of Lorentzian metrics, the conformal group in three and
four dimensions and the so called normal metric connection. A special feature
of this connection is that the non vanishing components of its torsion depend
on one relative invariant, the (generalized) W\"unschmann Invariant. We show
that the above mentioned construction naturally contains the Null Surface
Formulation of General Relativity.


title: Quantum Effect and Curvature Strength of Naked Singularities

abstract:
  There are many solutions to the Einstein field equations that demonstrate
naked singularity (NS) formation after regular evolution. It is possible,
however, that such a quantum effect as particle creation prevents NSs from
forming. We investigate the relation between the curvature strength and the
quantum effects of NSs in a very wide class of spherical dust collapse. Through
a perturbative calculation, we find that if the NS is very strong, the quantum
particle creation diverges as the Cauchy horizon is approached, while if the NS
is very weak, the creation should be finite. In the context of cosmic
censorship, strong NSs will be subjected to the backreaction of quantum effects
and may disappear or be hidden behind horizons, while weak NSs will not.


title:
On Loop Quantum Gravity Phenomenology and the Issue of Lorentz
  Invariance

abstract:
  A simple model is constructed which allows to compute modified dispersion
relations with effects from loop quantum gravity. Different quantization
choices can be realized and their effects on the order of corrections studied
explicitly. A comparison with more involved semiclassical techniques shows that
there is agreement even at a quantitative level.
  Furthermore, by contrasting Hamiltonian and Lagrangian descriptions we show
that possible Lorentz symmetry violations may be blurred as an artifact of the
approximation scheme. Whether this is the case in a purely Hamiltonian analysis
can be resolved by an improvement in the effective semiclassical analysis.


title: Self-similar Bianchi models: II. Class B models

abstract:
  In a companion article (referred hearafter as paper I) a detailed study of
the simply transitive Spatially Homogeneous (SH) models of class A concerning
the existence of a simply transitive similarity group has been given. The
present work (paper II) continues and completes the above study by considering
the remaining set of class B models. Following the procedure of paper I we find
all SH models of class B subjected only to the minimal geometric assumption to
admit a proper Homothetic Vector Field (HVF). The physical implications of the
obtained geometric results are studied by specialising our considerations to
the case of vacuum and $\gamma -$law perfect fluid models. As a result we
regain all the known exact solutions regarding vacuum and non-tilted perfect
fluid models. In the case of tilted fluids we find the \emph{general
}self-similar solution for the exceptional type VI$_{-1/9}$ model and we
identify it as equilibrium point in the corresponding dynamical state space. It
is found that this \emph{new} exact solution belongs to the subclass of models
$n_\alpha ^\alpha =0$, is defined for $\gamma \in (\frac 43,\frac 32)$ and
although has a five dimensional stable manifold there exist always two unstable
modes in the restricted state space. Furthermore the analysis of the remaining
types, guarantees that tilted perfect fluid models of types III, IV, V and
VII$_h$ cannot admit a proper HVF strongly suggesting that these models either
may not be asymptotically self-similar (type V) or may be extreme tilted at
late times. Finally for each Bianchi type, we give the extreme tilted
equilibrium points of their state space.


title:
Non-Riemannian acoustic black holes: Hawking radiation and Lorentz
  symmetry breaking

abstract:
  A non-Riemannian geometrical approach to the investigation of an acoustic
black hole in irrotational mean flows, based on the Lighthill vortex sound
theory is given. This additional example of analog gravity based on classical
fluids is used to investigate the acoustic Lorentz violation. An example is
given where the contortion vector is distributed along a ring inside the fluid
which can be gravitational analog of the torsion thick string spacetime defect.
It is found that the linear background flow velocity approximation, acoustic
Lorentz symmetry is breaking by the acoustic Cartan contortion in analogy to
the spontaneous gravitational Lorentz breaking in Riemann-Cartan spacetime
discovered recently by Kostelecky. We also show that although the acoustic
torsion contributes to the fiducial observer acceleration, it is not present in
Hawking radiation since is not presnt in the surface gravity of the acoustic
black hole.


title: Modelling the rotational curves of spiral galaxies with a scalar field

abstract:
  In a previous work (Mbelek 2001), we modelled the rotation curves (RC) of
spiral galaxies by including in the equation of motion of the stars the
dynamical terms from an external real self-interacting scalar field, $\psi$,
minimally coupled to gravity and which respects the equivalence principle in
the weak fields and low velocity approximation. This model appeared to have
three free parameters : the turnover radius, $r_{0}$, the maximum tangential
velocity, $v_{\theta max} = v_{\theta}(r_{0})$, plus a strictly positive
integer, $n$. Here, we propose a new improved version where the coupling of the
$\psi$-field to dark matter is emphasized at the expense of its
self-interaction. This reformulation presents the very advantageous possibility
that the same potential is used for all galaxies. Using at the same time a
quasi-isothermal dark matter density and the scalar field helps to better fit
the RC of spiral galaxies. In addition, new correlations are established.


title: Conformal Relativity: Theory and Observations

abstract:
  Theoretical and observational arguments are listed in favor of a new
principle of relativity of units of measurements as the basis of a
conformal-invariant unification of General Relativity and Standard Model by
replacement of all masses with a scalar (dilaton) field. The relative units
mean conformal observables: the coordinate distance, conformal time, running
masses, and constant temperature. They reveal to us a motion of a universe
along its hypersurface in the field space of events like a motion of a
relativistic particle in the Minkowski space, where the postulate of the vacuum
as a state with minimal energy leads to arrow of the geometric time. In
relative units, the unified theory describes the Cold Universe Scenario, where
the role of the conformal dark energy is played by a free minimal coupling
scalar field in agreement with the most recent distance-redshift data from type
Ia supernovae. In this Scenario, the evolution of the Universe begins with the
effect of intensive creation of primordial W-Z-bosons explaining the value of
CMBR temperature, baryon asymmetry, tremendous deficit of the luminosity masses
in the COMA-type superclusters and large-scale structure of the Universe.


title: Gravitating Monopole--Antimonopole Chains and Vortex Rings

abstract:
  We construct monopole-antimonopole chain and vortex solutions in
Yang-Mills-Higgs theory coupled to Einstein gravity. The solutions are static,
axially symmetric and asymptotically flat. They are characterized by two
integers (m,n) where m is related to the polar angle and n to the azimuthal
angle. Solutions with n=1 and n=2 correspond to chains of m monopoles and
antimonopoles. Here the Higgs field vanishes at m isolated points along the
symmetry axis. Larger values of n give rise to vortex solutions, where the
Higgs field vanishes on one or more rings, centered around the symmetry axis.
When gravity is coupled to the flat space solutions, a branch of gravitating
monopole-antimonopole chain or vortex solutions arises, and merges at a maximal
value of the coupling constant with a second branch of solutions. This upper
branch has no flat space limit. Instead in the limit of vanishing coupling
constant it either connects to a Bartnik-McKinnon or generalized
Bartnik-McKinnon solution, or, for m>4, n>4, it connects to a new
Einstein-Yang-Mills solution. In this latter case further branches of solutions
appear. For small values of the coupling constant on the upper branches, the
solutions correspond to composite systems, consisting of a scaled inner
Einstein-Yang-Mills solution and an outer Yang-Mills-Higgs solution.


title: Static cylindrical symmetry and conformal flatness

abstract:
  We present the whole set of equations with regularity and matching conditions
required for the description of physically meaningful static cylindrically
symmmetric distributions of matter, smoothly matched to Levi-Civita vacuum
spacetime. It is shown that the conformally flat solution with equal principal
stresses represents an incompressible fluid. It is also proved that any
conformally flat cylindrically symmetric static source cannot be matched
through Darmois conditions to the Levi-Civita spacetime. Further evidence is
given that when the Newtonian mass per unit length reaches 1/2 the spacetime
has plane symmetry.


title: Mass change and motion of a scalar charge in cosmological spacetimes

abstract:
  Continuing previous work reported in an earlier paper [L.M. Burko, A.I.
Harte, and E. Poisson, Phys. Rev. D 65, 124006 (2002)] we calculate the
self-force acting on a point scalar charge in a wide class of cosmological
spacetimes. The self-force produces two types of effect. The first is a
time-changing inertial mass, and this is calculated exactly for a particle at
rest relative to the cosmological fluid. We show that for certain cosmological
models, the mass decreases and then increases back to its original value. For
all other models except de Sitter spacetime, the mass is restored only to a
fraction of its original value. For de Sitter spacetime the mass steadily
decreases. The second effect is a deviation relative to geodesic motion, and we
calculate this for a charge that moves slowly relative to the dust in a
matter-dominated cosmology. We show that the net effect of the self-force is to
push on the particle. We show that this is not an artifact of the scalar
theory: The electromagnetic self-force acting on an electrically charged
particle also pushes on the particle. The paper concludes with a demonstration
that the pushing effect can also occur in the context of slow-motion
electrodynamics in flat spacetime.


title: Holographic bound and spectrum of quantized black hole

abstract:
  Recent attempts to calculate the black-hole entropy in loop quantum gravity
are demonstrated to be erroneous. The correct solution of the problem is
pointed out.


title:
Constraint-preserving boundary conditions in the Z4 Numerical Relativity
  formalism

abstract:
  The constraint-preserving approach, which aim is to provide consistent
boundary conditions for Numerical Relativity simulations, is discussed in
parallel with other recent developments. The case of the Z4 system is
considered, and constraint-preserving boundary conditions of the Sommerfeld
type are provided. A necessary condition for the stability of the proposed
boundary conditions is obtained, which amounts to the requirement of a
symmetric ordering of space derivatives. This requirement is numerically seen
to be also sufficient in the absence of corners and edges. Maximally
dissipative boundary conditions are also implemented. In this case, a less
restrictive stability condition is obtained, which is shown numerically to be
also sufficient even in the presence of corners and edges.


title: Anisotropic Brane Cosmology with Variable $G$ and $\Lambda$

abstract:
  In this work, the cosmological implications of brane world scenario are
investigated when the gravitational coupling $G$ and the cosmological term
$\Lambda$ are not constant but rather there are time variation of them. From
observational point of view, these time variations are taken in the form
$\frac{\dot{G}}{G}\sim H$ and $\Lambda \sim H^{2}$. The behavior of scale
factors and different kinematical parameters are investigated for different
possible scenarios where the bulk cosmological constant $\Lambda_{5}$ can be
zero, positive or negative.


title: Multigrid elliptic equation solver with adaptive mesh refinement

abstract:
  In this paper we describe in detail the computational algorithm used by our
parallel multigrid elliptic equation solver with adaptive mesh refinement. Our
code uses truncation error estimates to adaptively refine the grid as part of
the solution process. The presentation includes a discussion of the orders of
accuracy that we use for prolongation and restriction operators to ensure
second order accurate results and to minimize computational work. Code tests
are presented that confirm the overall second order accuracy and demonstrate
the savings in computational resources provided by adaptive mesh refinement.


title: Progress in Lunar Laser Ranging Tests of Relativistic Gravity

abstract:
  Analyses of laser ranges to the Moon provide increasingly stringent limits on
any violation of the Equivalence Principle (EP); they also enable several very
accurate tests of relativistic gravity. We report the results of our recent
analysis of Lunar Laser Ranging (LLR) data giving an EP test of \Delta
(M_G/M_I)_{EP} =(-1.0 +/- 1.4) x 10^{-13}. This result yields a Strong
Equivalence Principle (SEP) test of \Delta (M_G/M_I)_{SEP} =(-2.0 +/- 2.0) x
10^{-13}. Also, the corresponding SEP violation parameter \eta is (4.4 +/- 4.5)
x 10^{-4}, where \eta=4\beta-\gamma-3 and both \beta and \gamma are
parametrized post-Newtonian (PPN) parameters. Using the recent Cassini result
for the parameter \gamma, PPN parameter \beta is determined to be \beta-1=(1.2
+/- 1.1) x 10^{-4}. The geodetic precession test, expressed as a relative
deviation from general relativity, is K_{gp}=-0.0019 +/- 0.0064. The search for
a time variation in the gravitational constant results in \dot G/G=(4 +/- 9) x
10^{-13} yr^{-1}, consequently there is no evidence for local (~1AU) scale
expansion of the solar system.


title: Quantum energy inequalities in two dimensions

abstract:
  Quantum energy inequalities (QEIs) were established by Flanagan for the
massless scalar field on two-dimensional Lorentzian spacetimes globally
conformal to Minkowski space. We extend his result to all two-dimensional
globally hyperbolic Lorentzian spacetimes and use it to show that flat
spacetime QEIs give a good approximation to the curved spacetime results on
sampling timescales short in comparison with natural geometric scales. This is
relevant to the application of QEIs to constrain exotic spacetime metrics.


title: Asymptotic behaviour of curvature and matter in the Penrose limit

abstract:
  The asymptotic behaviour of the components of the Weyl tensor and of the
energy-momentum tensor in the Penrose limit is determined. In both cases a
peeling-off property is found. Examples of different types of matter are
provided. The expansion and shear of the congruence of null geodesics along
which the Penrose limit is taken are determined. Finally, the approach to the
singularity in the Penrose limit of cosmological space-times is discussed.


title:
Automatic Mirror Alignment for VIRGO: First experimental demonstration
  of the Anderson technique on a large-scale interferometer

abstract:
  The French-Italian interferometric gravitational wave detector VIRGO is
currently being commissioned. Its principal instrument is a Michelson laser
interferometer with 3 km long optical cavities in the arms and a
power-recycling mirror. The interferometer resides in an ultra-high vacuum
system and the mirrors are suspended from multistage pendulums for seismic
isolation.
  This type of laser interferometer reaches its maximum sensitivity only when
the optical setup is held actively very accurately at a defined operating
point: control systems using the precise interferometer signals stabilise the
longitudinal and angular positions of the optical component. This paper gives
an overview of the control system for the angular degrees of freedom; we
present the current status of the system and report the first experimental
demonstration of the Anderson technique on a large-scale interferometer.


title:
Canonical analysis of the BCEA topological matter model coupled to
  gravitation in (2+1) dimensions

abstract:
  We consider a topological field theory derived from the Chern - Simons action
in (2+1) dimensions with the I(ISO(2,1)) group,and we investigate in detail the
canonical structure of this theory.Originally developed as a topological theory
of Einstein gravity minimally coupled to topological matter fields in (2+1)
dimensions, it admits a BTZ black-hole solutions, and can be generalized to
arbitrary dimensions.In this paper, we further study the canonical structure of
the theory in (2+1) dimensions, by identifying all the distinct gauge
equivalence classes of solutions as they result from holonomy considerations.
The equivalence classes are discussed in detail, and examples of solutions
representative of each class are constructed or identified.


title: No news for Kerr-Schild fields

abstract:
  Algebraically special fields with no gravitational radiation are described.
Kerr-Schild fields, which include as a concrete case the Kinnersley photon
rocket, form an important subclass of them.


title: On the teleparallel limit of Poincare gauge theory

abstract:
  We will address the question of the consistency of teleparallel theories in
presence of spinning matter which has been a controversial subject of
discussion over the last twenty years. We argue that the origin of the problem
is not simply the symmetry or asymmetry of the stress-energy tensor of the
matter fields, which has been recently analyzed by several authors, but arises
at a more fundamental level, namely from the invariance of the field equatins
under a frame change, a problem that has been discussed long time ago by
Kopczynski in the framework of the teleparallel equivalent of general
relativity. More importantly, we show that the problem is not only confined to
the purely teleparallel theory but arises actually in every Poincare gauge
theory that admits a teleparallel geometry in the absence of spinning sources,
i.e. in its classical limit.


title: Dilatonic, Chiral Cosmic Strings

abstract:
  In this work, we deal with the chiral string model for which the world-sheet
current is null in the framework of a scalar-tensor gravity. Our main goal is
to analyse the impact of such a current on the gravitational macroscopic
effects. For the purpose of this analysis, we first study the gravitational
properties of the spacetime generated by this string in the presence of a
dilaton field. Then, we carry out an investigation of the mechanism of
formation and evolution of wakes in this framework, showing the explicit
contribution of the chirality to this effect.


title:
Smooth Singularities Exposed: Chimeras of the Differential Spacetime
  Manifold

abstract:
  The smooth gravitational singularities of the differential spacetime manifold
based General Relativity (GR) are viewed from the perspective of the background
manifold independent and, in extenso, Calculus-free Abstract Differential
Geometry (ADG). In particular, the inner Schwarzschild singularity is being
`resolved' ADG-theoretically in two different ways. A plethora of important
mathematical, physical and philosophical issues in current classical and
quantum gravity research are addressed and tackled.


title: On the Gravitational Wave in de Sitter Spacetime

abstract:
  For there is always a wrong sign in the mass of graviton in the so-called
perturbation expansion approximation of both Minkowski and de Sitter
spacetimes, the existence of gravitational wave from the metric perturbation of
de Sitter spacetime is doubtful. We try another way to start from the
assumption that the gravitational wave equation should be both general
covariant and conformal invariant and find that graviton is no longer a part of
metric field, it has an effective mass of $m_g=\sqrt{R/6}=% \sqrt{2\Lambda/3}$
with correct sign in de Sitter spacetime, though it's intrinsic mass remains
zero.


title: Bounding the mass of the graviton using eccentric binaries

abstract:
  We describe a method by which gravitational wave observations of eccentric
binary systems could be used to test General Relativity's prediction that
gravitational waves are dispersionless. We present our results in terms of the
graviton having a non-zero rest mass, or equivalently a non-infinite Compton
wavelength. We make a rough estimate of the bounds that might be obtained
following gravitational wave detections by the space-based LISA interferometer.
The bounds we find are comparable to those obtainable from a method proposed by
Will, and several orders of magnitude stronger than other dynamic (i.e.
gravitational wave based) tests that have been proposed. The method described
here has the advantage over those proposed previously of being simple to apply,
as it does not require the inspiral to be in the strong field regime nor
correlation with electromagnetic signals. We compare our results with those
obtained from static (i.e. non-gravitational wave based) tests.


title: Early Universe Dynamics in Semi-Classical Loop Quantum Cosmology

abstract:
  Within the framework of loop quantum cosmology, there exists a semi-classical
regime where spacetime may be approximated in terms of a continuous manifold,
but where the standard Friedmann equations of classical Einstein gravity
receive non-perturbative quantum corrections. An approximate, analytical
approach to studying cosmic dynamics in this regime is developed for both
spatially flat and positively-curved isotropic universes sourced by a
self-interacting scalar field. In the former case, a direct correspondence
between the classical and semi-classical field equations can be established
together with a scale factor duality that directly relates different expanding
and contracting universes. Some examples of non-singular, bouncing cosmologies
are presented together with a scaling, power-law solution.


title:
Inflationary Cosmology and Oscillating Universes in Loop Quantum
  Cosmology

abstract:
  We study oscillatory universes within the context of Loop Quantum Cosmology.
We make a comparative study of flat and positively curved universes sourced by
scalar fields with either positive or negative potentials. We investigate how
oscillating universes can set the initial conditions for successful slow-roll
inflation, while ensuring that the semi-classical bounds are satisfied. We
observe rich oscillatory dynamics with negative potentials, although it is
difficult to respect the semi-classical bounds in models of this type.


title: Formation of voids in the Universe within the Lemaitre-Tolman model

abstract:
  We develop models of void formation starting from a small initial fluctuation
at recombination and growing to a realistic present day density profile in
agreement with observations of voids. The model construction is an extension of
previously developed algorithms for finding a Lemaitre-Tolman metric that
evolves between two profiles of either density or velocity specified at two
times. Of the 4 profiles of concern -- those of density and velocity at
recombination and at the present day -- two can be specified and the other two
follow from the derived model. We find that, in order to reproduce the
present-day void density profiles, the initial velocity profile is more
important than the initial density profile. Extrapolation of current CMB
observations to the scales relevant to proto-voids is very uncertain. Even so,
we find that it is very difficult to make both the initial density and velocity
fluctuation amplitudes small enough, and still obtain a realistic void by
today.


title: Last orbits of binary strange quark stars

abstract:
  We present the first relativistic calculations of the final phase of inspiral
of a binary system consisting of two stars built predominantely of strange
quark matter (strange quark stars). We study the precoalescing stage within the
Isenberg-Wilson-Mathews approximation of general relativity using a multidomain
spectral method. A hydrodynamical treatment is performed under the assumption
that the flow is either rigidly rotating or irrotational, taking into account
the finite density at the stellar surface -- a distinctive feature with respect
to the neutron star case. The gravitational-radiation driven evolution of the
binary system is approximated by a sequence of quasi-equilibrium configurations
at fixed baryon number and decreasing separation. We find that the innermost
stable circular orbit (ISCO) is given by an orbital instability both for
synchronized and irrotational systems. This constrasts with neutron stars for
which the ISCO is given by the mass-shedding limit in the irrotational case.
The gravitational wave frequency at the ISCO, which marks the end of the
inspiral phase, is found to be 1400 Hz for two irrotational 1.35 Msol strange
stars and for the MIT bag model of strange matter with massless quarks and a
bag constant B=60 MeV/fm^3. Detailed comparisons with binary neutrons star
models, as well as with third order Post-Newtonian point-mass binaries are
given.


title: Gravitational wave interactions with magnetized plasmas

abstract:
  Gravitational waves (GWs) propagating through a uniformly magnetized plasma
interact directly with the magnetic field and excite magnetohydrodynamic (MHD)
waves with both electromagnetic and matter components. We study this process
for arbitrary geometry in the MHD approximation and find that all three
fundamental MHD modes -- slow and fast magnetosonic, and Alfven -- are excited
depending on both the polarization of the GW and the orientation of the ambient
magnetic field. The latter two modes can interact coherently with the GW
resulting in damping of the GW and linear growth of the plasma waves.


title:
Estimating spinning binary parameters and testing alternative theories
  of gravity with LISA

abstract:
  We investigate the effect of spin-orbit and spin-spin couplings on the
estimation of parameters for inspiralling compact binaries of massive black
holes, and for neutron stars inspiralling into intermediate-mass black holes,
using hypothetical data from the proposed Laser Interferometer Space Antenna
(LISA). We work both in Einstein's theory and in alternative theories of
gravity of the scalar-tensor and massive-graviton types. We restrict the
analysis to non-precessing spinning binaries, i.e. to cases where the spins are
aligned normal to the orbital plane. We find that the accuracy with which
intrinsic binary parameters such as chirp mass and reduced mass can be
estimated within general relativity is degraded by between one and two orders
of magnitude. We find that the bound on the coupling parameter omega_BD of
scalar-tensor gravity is significantly reduced by the presence of spin
couplings, while the reduction in the graviton-mass bound is milder. Using fast
Monte-Carlo simulations of 10^4 binaries, we show that inclusion of spin terms
in massive black-hole binaries has little effect on the angular resolution or
on distance determination accuracy. For stellar mass inspirals into
intermediate-mass black holes, the angular resolution and the distance are
determined only poorly, in all cases considered. We also show that, if LISA's
low-frequency noise sensitivity can be extrapolated from 10^-4 Hz to as low as
10^-5 Hz, the accuracy of determining both extrinsic parameters (distance, sky
location) and intrinsic parameters (chirp mass, reduced mass) of massive
binaries may be greatly improved.


title:
A geometric procedure for the reduced-state-space quantisation of
  constrained systems

abstract:
  We propose in this paper an alternative method for the quantisation of
systems with first-class constraints. This method is a combination of the
coherent-state-path-integral quantisation developed by Klauder, with the ideas
of reduced state space quantisation. The key idea is that the physical Hilbert
space may be defined by a coherent-state path-integral on the reduced state
space and that the metric on the reduced state space that is necessary for the
regularisation of the path-integral may be computed from the geometry of the
classical reduction procedure. We provide a number of examples--notably the
relativistic particle. Finally we discuss the quantisation of systems, whose
reduced state space has orbifold-like singularities.


title: Cosmography: Cosmology without the Einstein equations

abstract:
  How much of modern cosmology is really cosmography? How much of modern
cosmology is independent of the Einstein equations? (Independent of the
Friedmann equations?) These questions are becoming increasingly germane -- as
the models cosmologists use for the stress-energy content of the universe
become increasingly baroque, it behoves us to step back a little and carefully
disentangle cosmological kinematics from cosmological dynamics. The use of
basic symmetry principles (such as the cosmological principle) permits us to do
a considerable amount, without ever having to address the vexatious issues of
just how much "dark energy", "dark matter", "quintessence", and/or "phantom
matter" is needed in order to satisfy the Einstein equations. This is the
sub-sector of cosmology that Weinberg refers to as "cosmography", and in this
article I will explore the extent to which cosmography is sufficient for
analyzing the Hubble law and so describing many of the features of the universe
around us.


title: Charged perfect fluid configurations with a dilaton field

abstract:
  We examine static charged perfect fluid configurations in the presence of a
dilaton field. A method for construction of interior solutions is given. An
explicit example of an interior solution which matches continuously the
external Gibbons-Maeda-Garfinkle-Horowitz-Strominger solution is presented.
Extremely charged perfect fluid configurations with a dilaton are also
examined. We show that there are two types of extreme configurations. For each
type the field equations are reduced to a single nonlinear equation on a space
of a constant curvature. In the particular case of a perfect fluid with a
linear equation of state, the field equations of the first type configurations
are reduced to a Helmlotz equation on a space with a constant curvature. An
explicit example of an extreme configuration is given and discussed.


title:
A quantum cosmology and discontinuous signature changing classical
  solutions

abstract:
  We revisit the classical and quantum cosmology of a universe in which a self
interacting scalar field is coupled to gravity with a flat FRW type metric
undergoing continuous signature transition. We arrange for quantum
cosmologically allowed discontinuity in the classical solutions at the
signature changing hypersurface, provided these solutions be dual in some
respects. This may be of some importance in the study of early universe within
the signature changing scenarios.


title: Quantum fields and "Big Rip" expansion singularities

abstract:
  The effects of quantized conformally invariant massless fields on the
evolution of cosmological models containing a ``Big Rip'' future expansion
singularity are examined. Quantized scalar, spinor, and vector fields are found
to strengthen the accelerating expansion of such models as they approach the
expansion singularity.


title:
Mass and angular momenta of Kerr anti-de Sitter spacetimes in
  Einstein-Gauss-Bonnet theory

abstract:
  We compute the mass and angular momenta of rotating anti-de Sitter spacetimes
in Einstein-Gauss-Bonnet theory of gravity using a superpotential derived from
standard Noether identities. The calculation relies on the fact that the
Einstein and Einstein-Gauss-Bonnet vacuum equations are the same when
linearized on maximally symmetric backgrounds and uses the recently discovered
D-dimensional Kerr-anti-de Sitter solutions to Einstein's equations.


title: Two-dimensional static black holes with pointlike sources

abstract:
  We study the static black hole solutions of generalized two-dimensional
dilaton-gravity theories generated by pointlike mass sources, in the hypothesis
that the matter is conformally coupled. We also discuss the motion of test
particles. Due to conformal coupling, these follow the geodesics of a metric
obtained by rescaling the canonical metric with the dilaton.


title: Testing excision techniques for dynamical 3D black hole evolutions

abstract:
  We perform both distorted black hole evolutions and binary black hole head on
collisions and compare the results of using a full grid to results obtained by
excising the black hole interiors. In both cases the evolutions are found to
run essentially indefinitely, and produce the same, convergent waveforms.
Further, since both the distorted black holes and the head-on collision of
puncture initial data can be carried out without excision, they provide an
excellent dynamical test-bed for excision codes. This provides a strong
numerical demonstration of the validity of the excision idea, namely the event
horizon can be made to "protect" the spacetime from the excision boundary and
allow an accurate exterior evolution.


title:
Testing the Master Constraint Programme for Loop Quantum Gravity I.
  General Framework

abstract:
  Recently the Master Constraint Programme for Loop Quantum Gravity (LQG) was
proposed as a classically equivalent way to impose the infinite number of
Wheeler -- DeWitt constraint equations in terms of a single Master Equation.
While the proposal has some promising abstract features, it was until now
barely tested in known models. In this series of five papers we fill this gap,
thereby adding confidence to the proposal. We consider a wide range of models
with increasingly more complicated constraint algebras, beginning with a finite
dimensional, Abelean algebra of constraint operators which are linear in the
momenta and ending with an infinite dimensional, non-Abelean algebra of
constraint operators which closes with structure functions only and which are
not even polynomial in the momenta. In all these models we apply the Master
Constraint Programme successfully, however, the full flexibility of the method
must be exploited in order to complete our task. This shows that the Master
Constraint Programme has a wide range of applicability but that there are many,
physically interesting subtleties that must be taken care of in doing so. In
this first paper we prepare the analysis of our test models by outlining the
general framework of the Master Constraint Programme. The models themselves
will be studied in the remaining four papers. As a side result we develop the
Direct Integral Decomposition (DID) for solving quantum constraints as an
alternative to Refined Algebraic Quantization (RAQ).


title:
Testing the Master Constraint Programme for Loop Quantum Gravity II.
  Finite Dimensional Systems

abstract:
  This is the second paper in our series of five in which we test the Master
Constraint Programme for solving the Hamiltonian constraint in Loop Quantum
Gravity. In this work we begin with the simplest examples: Finite dimensional
models with a finite number of first or second class constraints, Abelean or
non -- Abelean, with or without structure functions.


title:
Testing the Master Constraint Programme for Loop Quantum Gravity III.
  SL(2,R) Models

abstract:
  This is the third paper in our series of five in which we test the Master
Constraint Programme for solving the Hamiltonian constraint in Loop Quantum
Gravity. In this work we analyze models which, despite the fact that the phase
space is finite dimensional, are much more complicated than in the second
paper: These are systems with an $SL(2,\Rl)$ gauge symmetry and the
complications arise because non -- compact semisimple Lie groups are not
amenable (have no finite translation invariant measure). This leads to severe
obstacles in the refined algebraic quantization programme (group averaging) and
we see a trace of that in the fact that the spectrum of the Master Constraint
does not contain the point zero. However, the minimum of the spectrum is of
order $\hbar^2$ which can be interpreted as a normal ordering constant arising
from first class constraints (while second class systems lead to $\hbar$ normal
ordering constants). The physical Hilbert space can then be be obtained after
subtracting this normal ordering correction.


title:
Testing the Master Constraint Programme for Loop Quantum Gravity IV.
  Free Field Theories

abstract:
  This is the fourth paper in our series of five in which we test the Master
Constraint Programme for solving the Hamiltonian constraint in Loop Quantum
Gravity. We now move on to free field theories with constraints, namely Maxwell
theory and linearized gravity. Since the Master constraint involves squares of
constraint operator valued distributions, one has to be very careful in doing
that and we will see that the full flexibility of the Master Constraint
Programme must be exploited in order to arrive at sensible results.


title:
Testing the Master Constraint Programme for Loop Quantum Gravity V.
  Interacting Field Theories

abstract:
  This is the final fifth paper in our series of five in which we test the
Master Constraint Programme for solving the Hamiltonian constraint in Loop
Quantum Gravity. Here we consider interacting quantum field theories,
specificlly we consider the non -- Abelean Gauss constraints of Einstein --
Yang -- Mills theory and 2+1 gravity. Interestingly, while Yang -- Mills theory
in 4D is not yet rigorously defined as an ordinary (Wightman) quantum field
theory on Minkowski space, in background independent quantum field theories
such as Loop Quantum Gravity (LQG) this might become possible by working in a
new, background independent representation.


title:
Causal hierarchy of spacetimes, temporal functions and smoothness of
  Geroch's splitting. A revision

abstract:
  After the heroic epoch of Causality Theory, problems concerning the
smoothability of time functions and Cauchy hypersurfaces remained as unanswered
folk questions. Just recently solved, our aim is to discuss the state of the
art on this topic, including self-contained proofs for questions on causally
continuous, stably causal and globally hyperbolic spacetimes.


title: Quantum cosmology of the brane universe

abstract:
  We canonically quantize the dynamics of the brane universe embedded into the
five-dimensional Schwarzschild-anti-deSitter bulk space-time. We show that in
the brane-world settings the formulation of the quantum cosmology, including
the problem of initial conditions, is conceptually more simple than in the
3+1-dimensional case. The Wheeler-deWitt equation is a finite-difference
equation. It is exactly solvable in the case of a flat universe and we find the
ground state of the system. The closed brane universe can be created as a
result of decay of the bulk black hole.


title: Relativistic Elastostatics I: Bodies in Rigid Rotation

abstract:
  We consider elastic bodies in rigid rotation, both nonrelativistically and in
special relativity. Assuming a body to be in its natural state in the absence
of rotation, we prove the existence of solutions to the elastic field equations
for small angular velocity.


title:
Parameter estimation of inspiralling compact binaries using 3.5
  post-Newtonian gravitational wave phasing: The non-spinning case

abstract:
  (Abridged) We revisit the problem of parameter estimation of
gravitational-wave chirp signals from inspiralling non-spinning compact
binaries in the light of the recent extension of the post-Newtonian (PN)
phasing formula to order $(v/c)^7$ beyond the leading Newtonian order. We study
in detail the implications of higher post-Newtonian orders from 1PN up to 3.5PN
in steps of 0.5PN ($\sim v/c$), and examine their convergence. In both initial
and advanced detectors the estimation of the chirp mass (${\cal M}$) and
symmetric mass ratio ($\eta$) improve at higher PN orders but oscillate with
every half-a-PN order. We compare parameter estimation in different detectors
and assess their relative performance in two different ways: at a {\it fixed
SNR,} with the aim of understanding how the bandwidth improves parameter
estimation, and for a {\it fixed source}, to gauge the importance of
sensitivity. Errors in parameter estimation at a fixed SNR are smaller for
VIRGO than for both initial and advanced LIGO. However, for sources at a fixed
distance it is advanced LIGO that achieves the lowest errors owing to its
greater sensitivity. Finally, we compute the amplitude corrections due to the
`frequency-sweep' in the Fourier domain representation of the waveform within
the stationary phase approximation and discuss its implication on parameter
estimation.


title:
Quasiequilibrium sequences of binary strange quark stars in general
  relativity

abstract:
  Inspiraling compact binaries are expected to be the strongest sources of
gravitational waves for VIRGO, LIGO and other laser interferometers. We present
the first computations of quasi-equilibrium sequences of compact binaries
containing two strange quark stars (which are currently considered as a
possible alternative to neutron stars). We study a precoalescing stage in the
conformal flatness approximation of general relativity using a multidomain
spectral method. A hydrodynamical treatment is performed under the assumption
that the flow is irrotational.


title:
Quasi-local holography and quasi-local mass of classical fields in
  Minkowski spacetime

abstract:
  The 2-surface characterization of special classical radiative Higgs-,
Yang-Mills and linear zero-rest-mass (l.z.r.m) fields with any spin is
investigated. We determine all the zero quasi-local mass Higgs- and Yang-Mills
field configurations with compact semisimple gauge groups, and show that they
are plane waves (provided the Higgs field is massless and linear) and
appropriate generalizations of plane waves (`Yang-Mills pp-waves'),
respectively. A tensor field (generalizing the energy-momentum tensor for the
Maxwell field and of the Bel-Robinson tensor for the linearized gravitational
field) is found by means of which the pp-wave nature of the solutions of the
l.z.r.m. field equations with any spin can be characterized equivalently. It is
shown that these radiative Yang-Mills and l.z.r.m. fields, given on a finite
globally hyperbolic domain D, are determined completely by certain
unconstrained data set on a closed spacelike 2-surface, the `edge of D'. These
pure radiative solutions are shown to determine a dense subset in the set of
solutions of various (Yang-Mills and l.z.r.m.) field equations. Thus for these
field configurations some `classical quasi-local holography' holds.


title: Dynamical evolution of quasi-circular binary black hole data

abstract:
  We study the fully nonlinear dynamical evolution of binary black hole data,
whose orbital parameters are specified via the effective potential method for
determining quasi-circular orbits. The cases studied range from the
Cook-Baumgarte innermost stable circular orbit (ISCO) to significantly beyond
that separation. In all cases we find the black holes to coalesce (as
determined by the appearance of a common apparent horizon) in less than half an
orbital period. The results of the numerical simulations indicate that the
initial holes are not actually in quasi-circular orbits, but that they are in
fact nearly plunging together. The dynamics of the final horizon are studied to
determine physical parameters of the final black hole, such as its spin, mass,
and oscillation frequency, revealing information about the inspiral process. We
show that considerable resolution is required to extract accurate physical
information from the final black hole formed in the merger process, and that
the quasi-normal modes of the final hole are strongly excited in the merger
process. For the ISCO case, by comparing physical measurements of the final
black hole formed to the initial data, we estimate that less than 3% of the
total energy is radiated in the merger process.


title: Self-force Regularization in the Schwarzschild Spacetime

abstract:
  We discuss the gravitational self-force on a particle in a black hole
space-time. For a point particle, the full (bare) self-force diverges. The
metric perturbation induced by a particle can be divided into two parts, the
direct part (or the S part) and the tail part (or the R part), in the harmonic
gauge, and the regularized self-force is derived from the R part which is
regular and satisfies the source-free perturbed Einstein equations. But this
formulation is abstract, so when we apply to black hole-particle systems, there
are many problems to be overcome in order to derive a concrete self-force.
These problems are roughly divided into two parts. They are the problem of
regularizing the divergent self-force, i.e., ``subtraction problem'' and the
problem of the singularity in gauge transformation, i.e., ``gauge problem''. In
this paper, we discuss these problems in the Schwarzschild background and
report some recent progress.


title: LARES/WEBER-SAT, frame-dragging and fundamental physics

abstract:
  After a brief introduction on the scientific objectives of the
LARES/WEBER-SAT satellite we present the recent measurement of the
Lense-Thirring effect using the nodes of the LAGEOS and LAGEOS 2 satellites and
using the Earth gravity model EIGENGRACE02S obtained by the GRACE space
mission, we also include some determination of the rate of change of the lowest
order Earth's even zonal harmonics. Finally, we describe an interesting
possibility of testing the Brane-World unified theory of fundamental
interactions by the use of a specially designed LARES/WEBER-SAT satellite.


title: The initial value problem in numerical relativity

abstract:
  The conformal method for constructing initial data for Einstein's equations
is presented in both the Hamiltonian and Lagrangian picture (extrinsic
curvature decomposition and conformal thin sandwich formalism, respectively),
and advantages due to the recent introduction of a weight-function in the
extrinsic curvature decomposition are discussed. I then describe recent
progress in numerical techniques to solve the resulting elliptic equations, and
explore innovative approaches toward the construction of astrophysically
realistic initial data for binary black hole simulations.


title:
Quantum horizons and black hole entropy: Inclusion of distortion and
  rotation

abstract:
  Equilibrium states of black holes can be modelled by isolated horizons. If
the intrinsic geometry is spherical, they are called type I while if it is
axi-symmetric, they are called type II. The detailed theory of geometry of
\emph{quantum} type I horizons and the calculation of their entropy can be
generalized to type II, thereby including arbitrary distortions and rotations.
The leading term in entropy of large horizons is again given by 1/4th of the
horizon area for the \emph{same} value of the Barbero-Immirzi parameter as in
the type I case. Ideas and constructions underlying this extension are
summarized.


title: Physics of Deformed Special Relativity: Relativity Principle revisited

abstract:
  In many different ways, Deformed Special Relativity (DSR) has been argued to
provide an effective limit of quantum gravity in almost-flat regime. Some
experiments will soon be able to test some low energy effects of quantum
gravity, and DSR is a very promising candidate to describe these latter.
Unfortunately DSR is up to now plagued by many conceptual problems (in
particular how it describes macroscopic objects) which forbids a definitive
physical interpretation and clear predictions. Here we propose a consistent
framework to interpret DSR. We extend the principle of relativity: the same way
that Special Relativity showed us that the definition of a reference frame
requires to specify its speed, we show that DSR implies that we must also take
into account its mass. We further advocate a 5-dimensional point of view on DSR
physics and the extension of the kinematical symmetry from the Poincare group
to the Poincare-de Sitter group (ISO(4,1)). This leads us to introduce the
concept of a pentamomentum and to take into account the renormalization of the
DSR deformation parameter kappa. This allows the resolution of the "soccer ball
problem" (definition of many-particle-states) and provides a physical
interpretation of the non-commutativity and non-associativity of the addition
the relativistic quadrimomentum. In particular, the coproduct of the
kappa-Poincare algebra is interpreted as defining the law of change of
reference frames and not the law of scattering. This point of view places DSR
as a theory, half-way between Special Relativity and General Relativity,
effectively implementing the Schwarzschild mass bound in a flat relativistic
context.


title:
Transition from decelerated to accelerated cosmic expansion in
  braneworld universes

abstract:
  Braneworld theory provides a natural setting to treat, at a classical level,
the cosmological effects of vacuum energy. Non-static extra dimensions can
generally lead to a variable vacuum energy, which in turn may explain the
present accelerated cosmic expansion. We concentrate our attention in models
where the vacuum energy decreases as an inverse power law of the scale factor.
These models agree with the observed accelerating universe, while fitting
simultaneously the observational data for the density and deceleration
parameter. The redshift at which the vacuum energy can start to dominate
depends on the mass density of ordinary matter. For Omega = 0.3, the transition
from decelerated to accelerated cosmic expansion occurs at z approx 0.48 +/-
0.20, which is compatible with SNe data. We set a lower bound on the
deceleration parameter today, namely q > - 1 + 3 Omega/2, i.e., q > - 0.55 for
Omega = 0.3. The future evolution of the universe crucially depends on the time
when vacuum starts to dominate over ordinary matter. If it dominates only
recently, at an epoch z < 0.64, then the universe is accelerating today and
will continue that way forever. If vacuum dominates earlier, at z > 0.64, then
the deceleration comes back and the universe recollapses at some point in the
distant future. In the first case, quintessence and Cardassian expansion can be
formally interpreted as the low energy limit of our model, although they are
entirely different in philosophy. In the second case there is no correspondence
between these models and ours.


title:
Linearized solutions of the Einstein equations within a Bondi-Sachs
  framework, and implications for boundary conditions in numerical simulations

abstract:
  We linearize the Einstein equations when the metric is Bondi-Sachs, when the
background is Schwarzschild or Minkowski, and when there is a matter source in
the form of a thin shell whose density varies with time and angular position.
By performing an eigenfunction decomposition, we reduce the problem to a system
of linear ordinary differential equations which we are able to solve. The
solutions are relevant to the characteristic formulation of numerical
relativity: (a) as exact solutions against which computations of gravitational
radiation can be compared; and (b) in formulating boundary conditions on the
$r=2M$ Schwarzschild horizon.


title: A Solution to Symmetric Teleparallel Gravity

abstract:
  Teleparallel gravity models, in which the curvature and the nonmetricity of
spacetime are both set zero, are widely studied in the literature. We work a
different teleparallel theory, in which the curvature and the torsion of
spacetime are both constrained to zero, but the nonmetricity is nonzero. After
reformulating the general relativity in this spacetime we find a solution and
investigate its singularity structure.


title: Quantum Horizons and Space-Time Non-Commutativity

abstract:
  We study dynamics of a scalar field in the near-horizon region described by a
static Klein-Gordon operator which is the Hamiltonian of the system. The
explicite construction of a time operator near-horizon is given and its
self-adjointness discussed.


title: Quasi-local contribution to the gravitational self-force

abstract:
  The gravitational self-force on a point particle moving in a vacuum
background spacetime can be expressed as an integral over the past worldline of
the particle, the so-called tail term. In this paper, we consider that piece of
the self-force obtained by integrating over a portion of the past worldline
that extends a proper time ${\Delta}{\tau}$ into the past, provided that
${\Delta}{\tau}$ does not extend beyond the normal neighborhood of the
particle. We express this ``quasi-local'' piece as a power series in the proper
time interval ${\Delta}{\tau}$. We argue from symmetries and dimensional
considerations that the $O({\Delta}{\tau}^0)$ and $O({\Delta}{\tau})$ terms in
this power series must vanish, and compute the first two non-vanishing terms
which occur at $O({\Delta}{\tau}^2)$ and $O({\Delta}{\tau}^3)$. The
coefficients in the expansion depend only on the particle's four velocity and
on the Weyl tensor and its derivatives at the particle's location. The result
may be useful as a foundation for a practical computational method for
gravitational self-forces in the Kerr spacetime, in which the portion of the
tail integral in the distant past is computed numerically from a mode sum
decomposition.


title:
The final phase of inspiral of neutron stars: realistic equations of
  state

abstract:
  Coalescing compact star binaries are expected to be among the strongest
sources of gravitational radiation to be seen by laser interferometers. We
present calculations of the final phase of inspiral of equal mass irrotational
neutron star binaries and strange quark star binaries. Six types of equations
of state at zero temperature are used - three realistic nuclear equations of
state of various softness and three different MIT bag models of strange quark
matter. We study the precoalescing stage within the Isenberg-Wilson-Mathews
approximation of general relativity using a multidomain spectral method. The
gravitational-radiation driven evolution of the binary system is approximated
by a sequence of quasi-equilibrium configurations at fixed baryon number and
decreasing separation. We find that the innermost stable circular orbit (ISCO)
is given by an orbital instability for binary strange quark stars and by the
mass-shedding limit for neutron star binaries. The gravitational wave frequency
at the ISCO, which marks the end of the inspiral phase, is found to be around
1100-1460 Hz for two 1.35 solar masses irrotational strange stars described by
the MIT bag model and between 800 Hz and 1230 Hz for neutron stars.


title:
Relating Spin Foams and Canonical Quantum Gravity: (n-1)+1 formulation
  of nD spin foams

abstract:
  In this article we lay foundations for a formal relationship of spin foam
models of gravity and BF theory to their continuum canonical formulations.
First the derivation of the spin foam model of the BF theory from the discrete
BF theory action in n dimensions is reviewed briefly. By foliating the
underlying n dimensional simplicial manifold using n-1 dimensional simplicial
hypersurfaces, the spin foam model is reformulated. Then it is shown that spin
network functionals arise naturally on the foliations. The graphs of these spin
network functionals are dual to the triangulations of the foliating
hypersurfaces. Quantum Transition amplitudes are defined. I calculate the
transition amplitudes related to 2D BF theory explicitly and show that these
amplitudes are triangulation independent. The application to the spin foam
models of gravity is discussed briefly.


title: Geons with spin and charge

abstract:
  We construct new geon-type black holes in D>3 dimensions for Einstein's
theory coupled to gauge fields. A static nondegenerate vacuum black hole has a
geon quotient provided the spatial section admits a suitable discrete isometry,
and an antisymmetric tensor field of rank 2 or D-2 with a pure F^2 action can
be included by an appropriate (and in most cases nontrivial) choice of the
field strength bundle. We find rotating geons as quotients of the
Myers-Perry(-AdS) solution when D is odd and not equal to 7. For other D we
show that such rotating geons, if they exist at all, cannot be continuously
deformed to zero angular momentum. With a negative cosmological constant, we
construct geons with angular momenta on a torus at the infinity. As an example
of a nonabelian gauge field, we show that the D=4 spherically symmetric SU(2)
black hole admits a geon version with a trivial gauge bundle. Various
generalisations, including both black-brane geons and Yang-Mills theories with
Chern-Simons terms, are briefly discussed.


title: False Vacuum Lumps with Fermions

abstract:
  This paper studies false vacuum lumps surrounded by the true vacuum in a real
scalar field potential in flat spacetime. Fermions reside in the core of the
lump, which are coupled with the scalar field via Yukawa interaction. Such
lumps are stable against spherical collapse and deformation from spherical
shape based on energetics considerations. The fermions inside the lump are
treated as a uniform Fermi gas. We consider the Fermi gas in both
ultrarelativistic and nonrelativistic limits. The mass and size of these lumps
depend on the scale characterizing the scalar field potential as well as the
mass density of the fermions.


title: A numerical examination of an evolving black string horizon

abstract:
  We use the numerical solution describing the evolution of a perturbed black
string presented in Choptuik et al. (2003) to elucidate the intrinsic behavior
of the horizon. It is found that by the end of the simulation, the affine
parameter on the horizon has become very large and the expansion and shear of
the horizon in turn very small. This suggests the possibility that the horizon
might pinch off in infinite affine parameter.


title: Isometry germs and related structures

abstract:
  We define an Isometry germ at any given event $x$ of space-time as a vector
field $\xi$ defined in a neighborhood of $x$ such that the Lie derivative of
both the metric and the Riemannian connection are zero at this event. Two
isometry germs can be said to be equivalent if their values and the values of
their first derivatives coincide at $x$. The corresponding quotient space can
be endowed with a structure of a bracket algebra which is a deformation of de
Sitter's Lie algebra. Each isometry germ defines also a local stationary frame
of reference, the consideration of the family of adapted coordinate
transformations between any two of them leading to a local novel structure that
generalizes the Lorentz group.


title: Kerr--Schild metrics and gravitational radiation

abstract:
  We describe conditions assuring that the Kerr--Schild type solutions of
Einstein equations with pure radiation fields are asymptotically flat at future
null infinity. Such metrics cannot describe ``true'' gravitational radiation
from bounded sources--it is shown that the Bondi news function vanishes
identically. We obtain formulae for the total energy and angular momentum at
scri+. As an example we consider non-stationary generalization of the Kerr
metric given by Vaidya and Patel. Angular momentum and total energy are
expressed in closed form as functions of retarded time.


title: Introduction to cosmology

abstract:
  This text consists on a series of introductory lectures on cosmology for
mathematicians and physicists who are not specialized on the subject.


title:
Gravitational radiation reaction in the equations of motion of compact
  binaries to 3.5 post-Newtonian order

abstract:
  We compute the radiation reaction force on the orbital motion of compact
binaries to the 3.5 post-Newtonian (3.5PN) approximation, i.e. one PN order
beyond the dominant effect. The method is based on a direct PN iteration of the
near-zone metric and equations of motion of an extended isolated system, using
appropriate ``asymptotically matched'' flat-space-time retarded potentials. The
formalism is subsequently applied to binary systems of point particles, with
the help of the Hadamard self-field regularisation. Our result is the 3.5PN
acceleration term in a general harmonic coordinate frame. Restricting the
expression to the centre-of-mass frame, we find perfect agreement with the
result derived in a class of coordinate systems by Iyer and Will using the
energy and angular momentum balance equations.


title: The status of numerical relativity

abstract:
  Numerical relativity has come a long way in the last three decades and is now
reaching a state of maturity. We are gaining a deeper understanding of the
fundamental theoretical issues related to the field, from the well posedness of
the Cauchy problem, to better gauge conditions, improved boundary treatment,
and more realistic initial data. There has also been important work both in
numerical methods and software engineering. All these developments have come
together to allow the construction of several advanced fully three-dimensional
codes capable of dealing with both matter and black holes. In this manuscript I
make a brief review the current status of the field.


title:
Asymptotically simple solutions of the vacuum Einstein equations in even
  dimensions

abstract:
  We show that a set of conformally invariant equations derived from the
Fefferman-Graham tensor can be used to construct global solutions of the vacuum
Einstein equations, in all even dimensions. This gives, in particular, a new,
simple proof of Friedrich's result on the future hyperboloidal stability of
Minkowski space-time, and extends its validity to even dimensions.


title:
Quantum Properties of a General Path Deviation Equation in the
  Pap-Geometry

abstract:
  A path deviation equation in the Parameterized Absolute Parallelism (PAP)
geometry is derived. This equation includes curvature and torsion terms. These
terms are found to be naturally quantized. The equation represents the
deviation from a general path equation, in the PAP-geometry, derived by the
author in a previous work. It is shown that, as the effect of the torsion, on
the deviation, increases, the effect of the curvature decreases. It is also
shown that the general path deviation equation can be reduced to the geodesic
deviation equation if PAP-geometry becomes Riemannian. The equation can be used
to study the deviation from the trajectories of spinning elementary particles.


title:
First upper limit analysis and results from LIGO science data:
  stochastic background

abstract:
  I describe analysis of correlations in the outputs of the three LIGO
interferometers from LIGO's first science run, held over 17 days in August and
September of 2002, and the resulting upper limit set on a stochastic background
of gravitational waves. By searching for cross-correlations between the LIGO
detectors in Livingston, LA and Hanford, WA, we are able to set a 90%
confidence level upper limit of h_{100}^2 Omega_0 < 23 +/- 4.6.


title: Massive scalar field instability in Kerr spacetime

abstract:
  We study the Klein-Gordon equation for a massive scalar field in Kerr
spacetime in the time-domain. We demonstrate that under conditions of
super-radiance, the scalar field becomes unstable and its amplitude grows
without bound. We also estimate the growth rate of this instability.


title: Universality in Quasi-normal Modes of Neutron Stars

abstract:
  We study the universality in gravitational waves emitted from non-rotating
neutron stars characterized by different equations of state (EOS). We find that
the quasi-normal mode frequencies of such waves, including the $w$-modes and
the $f$-mode, display similar universal scaling behaviours that hold for most
EOS. Such behaviours are shown to stem from the mathematical structure of the
axial and the polar gravitational wave equations, and the fact that the mass
distribution function can be approximated by a cubic-quintic polynomial in
radius. As a benchmark for other realistic neutron stars, a simple model of
neutron stars is adopted here to reproduce the pulsation frequencies and the
generic scaling behaviours mentioned above with good accuracy.


title:
On the possibility of testing the Brane-World scenario with orbital
  motions in the Solar System

abstract:
  Recently it has been suggested to use the perigee of the proposed
LARES/WEBER-SAT satellite in order to measure the secular precession which
would be induced on such Keplerian orbital element by a weak-field modification
of gravity occurring in some Brane-World scenarios put forth by Dvali,
Gabadadze and Porrati. This precession, derived for the first time by Lue and
Starkman, amounts to 4\times 10-3 milliarcseconds per year for an Earth
orbiting satellite. In this paper we show that, according to the recently
released EIGEN-CG01C Earth gravity model the quite larger systematic errors due
to the Newtonian part of the terrestrial gravitational potential would vanish
any attempts to detect a so small effect. The situation is much more favorable
in the Solar System scenario. Indeed, the non-Newtonian perihelion advance of
Mars, which is the currently best tracked planet, has recently been measured
with an accuracy of 1\times 10^-4 arcseconds per century; the Dvali precession
is 4\times 10^-4 arcseconds per century. A suitable combination of the
perihelia and the nodes of Mars and Mercury, which disentangles the Dvali
effect from the competing larger Newtonian and general relativistic
precessions, might allow to reach a 1-sigma 47% level of accuracy.


title: Quantum Cosmological Models

abstract:
  We contrast the initial condition requirements of various contemporary
cosmological models, including inflationary and bouncing cosmologies. Various
proposals such as Hartle-Hawking's no boundary, or Tunnelling boundary
conditions are assessed on grounds of naturalness and fine tuning.
Alternatively a quiescent or ``time machine'' state is considered. Extensions
to brane models are also addressed. Further ideas about universe creation from
a meta-universe are outlined.
  We compare the recent loop quantum cosmology of Bojowald and coworkers with
these earlier proposals. A number of possible difficulties and limitations are
outlined.


title: Testing Dark Energy and Cardassian Expansion for Causality

abstract:
  Causality principle is a powerful criterion that allows us to discriminate
between what is possible or not. In this paper we study the transition from
decelerated to accelerated expansion in the context of Cardassian and dark
energy models. We distinguish two important events during the transition. The
first one is the end of the matter-dominated phase, which occurs at some time
$t_{eq}$. The second one is the actual crossover from deceleration to
acceleration, which occurs at some $t_{T}$. Causality requires $t_{T} \geq
t_{eq}$. We demonstrate that dark energy models, with constant $w$, and
Cardassian expansion, are compatible with causality only if $(\Omega_{M} -
\bar{q}) \leq 1/2$. However, observational data indicate that the most probable
option is $(\Omega_{M} - \bar{q}) > 1/2$. Consequently, the transition from
deceleration to acceleration in dark energy and Cardassian models occurs before
the matter-dominated epoch comes to an end, i.e., $t_{eq} > t_{T}$. Which
contradicts causality principle.


title: Asymptotics of Regulated Field Commutators for Einstein-Rosen Waves

abstract:
  We discuss the asymptotic behavior of regulated field commutators for
linearly polarized, cylindrically symmetric gravitational waves and the
mathematical techniques needed for this analysis. We concentrate our attention
on the effects brought about by the introduction of a physical cut-off in the
study of the microcausality of the model and describe how the different
physically relevant regimes are affected by its presence. Specifically we
discuss how genuine quantum gravity effects can be disentangled from those
originating in the introduction of a regulator.


title:
Generalized Smarr relation for Kerr AdS black holes from improved
  surface integrals

abstract:
  By using suitably improved surface integrals, we give a unified geometric
derivation of the generalized Smarr relation for higher dimensional Kerr black
holes which is valid both in flat and in anti-de Sitter backgrounds. The
improvement of the surface integrals, which allows one to use them
simultaneously at infinity and on the horizon, consists in integrating them
along a path in solution space. Path independence of the improved charges is
discussed and explicitly proved for the higher dimensional Kerr AdS black
holes. It is also shown that the charges for these black holes can be correctly
computed from the standard Hamiltonian or Lagrangian surface integrals.


title: Geometrization of the Gauge Connection within a Kaluza-Klein Theory

abstract:
  Within the framework of a Kaluza-Klein theory, we provide the geometrization
of a generic (Abelian and non-Abelian) gauge coupling, which comes out by
choosing a suitable matter fields dependence on the extra-coordinates.
  We start by the extension of the Nother theorem to a multidimensional
spacetime being the direct sum of a 4-dimensional Minkowski space and of a
compact homogeneous manifold (whose isometries reflect the gauge symmetry); we
show, how on such a ``vacuum'' configuration, the extra-dimensional components
of the field momentum correspond to the gauge charges. Then we analyze the
structure of a Dirac algebra as referred to a spacetime with the Kaluza-Klein
restrictions and, by splitting the corresponding free-field Lagrangian, we show
how the gauge coupling terms outcome.


title: Dynamics of a Spherical Null Shell within the Distributional Formalism

abstract:
  Dynamics of a null thin shell immersed in a generic spherically symmetric
spacetime is obtained within the distributional formalism. It has been shown
that the distributional formalism leads to the same result as in the
conventional formalism.


title: General Relativity as a Genuine Connection Theory

abstract:
  The Palatini formulation is used to develop a genuine connection theory for
general relativity, in which the gravitational field is represented by a
Lorentz-valued spin connection. The existence of a tetrad field, given by the
Fock-Ivanenko covariant derivative of the tangent-space coordinates, implies a
coupling between the spin connection and the coordinate vector-field, which
turns out to be the responsible for the onset of curvature. This
connection-coordinate coupling can thus be considered as the very foundation of
the gravitational interaction. The peculiar form of the tetrad field is shown
to reduce both Bianchi identities of general relativity to a single one, which
brings this theory closer to the gauge theories describing the other
fundamental interactions of Nature. Some further properties of this approach
are also examined.


title:
New class of post-Newtonian approximants to the waveform templates of
  inspiralling compact binaries: Test-mass in the Schwarzschild spacetime

abstract:
  (Abridged): The standard adiabatic approximation to phasing of gravitational
waves from inspiralling compact binaries uses the post-Newtonian expansions of
the binding energy and gravitational wave flux both truncated at the same
relative post-Newtonian order. Motivated by the eventual need to go beyond the
adiabatic approximation we must view the problem as the dynamics of the binary
under conservative post-Newtonian forces and gravitational radiation damping.
  From the viewpoint of the dynamics of the binary, the standard approximation
at leading order is equivalent to retaining the 0PN and 2.5PN terms in the
acceleration and neglecting the intervening 1PN and 2PN terms. A complete
mathematically consistent treatment of the acceleration at leading order should
include all PN terms up to 2.5PN without any gaps. These define the 'standard'
and 'complete' non-adiabatic approximants respectively. We propose a new and
simple complete adiabatic approximant constructed from the energy and flux
functions. At the leading order it uses the 2PN energy function rather than the
0PN one in the standard approximation so that in spirit it corresponds to the
dynamics where there are no missing post-Newtonian terms in the acceleration.
We compare the overlaps of the standard and complete adiabatic approximants
with the exact waveforms for a test-particle orbiting a Schwarzschild black
hole. The complete adiabatic approximants lead to a remarkable improvement in
the effectualness at lower PN (< 3PN) orders. However, standard adiabatic
approximants of order $\geq$ 3PN are nearly as good as the complete adiabatic
approximants for the construction of effectual templates. Standard and complete
approximants beyond the adiabatic approximation are next studied using the
Lagrangian models of Buonanno, Chen and Vallisneri.


title: Torsion as Alternative to Curvature in the Description of Gravitation

abstract:
  The general covariance principle, seen as an active version of the principle
of equivalence, is used to study the gravitational coupling prescription in the
presence of curvature and torsion. It is concluded that the coupling
prescription determined by this principle is always equivalent with the
corresponding prescription of general relativity. An application to the case of
a Dirac spinor is made.


title:
The Feynman propagator for quantum gravity: spin foams, proper time,
  orientation, causality and timeless-ordering

abstract:
  We discuss the notion of causality in Quantum Gravity in the context of
sum-over-histories approaches, in the absence therefore of any background time
parameter. In the spin foam formulation of Quantum Gravity, we identify the
appropriate causal structure in the orientation of the spin foam 2-complex and
the data that characterize it; we construct a generalised version of spin foam
models introducing an extra variable with the interpretation of proper time and
show that different ranges of integration for this proper time give two
separate classes of spin foam models: one corresponds to the spin foam models
currently studied, that are independent of the underlying orientation/causal
structure and are therefore interpreted as a-causal transition amplitudes; the
second corresponds to a general definition of causal or orientation dependent
spin foam models, interpreted as causal transition amplitudes or as the Quantum
Gravity analogue of the Feynman propagator of field theory, implying a notion
of ''timeless ordering''.


title:
Temperature Fluctuation and an Expected Limit of Hubble Parameter in the
  Self-Consistent Model

abstract:
  The temperature gradient of microwave background radiation (CMBR) is
calculated in the Self Consistent Model. An expected values for Hubble
parameter have been presented in two different cases. In the first case the
temperature is treated as a function of time only, while in the other one the
temperature depends on relaxation of isotropy condition in the self-consistent
model and the assumption that the universe expands adiabatically. The COBE's or
WMAP's fluctuations in temperature of CMBR may be used to predict a value for
Hubble parameter.


title: Tetrads in Geometrodynamics

abstract:
  A new tetrad is introduced within the framework of geometrodynamics for
non-null electromagnetic fields. This tetrad diagonalizes the electromagnetic
stress-energy tensor and allows for maximum simplification of the expression of
the electromagnetic field. The Einstein-Maxwell equations will also be
simplified.


title: On the history of fourth order metric theories of gravitation

abstract:
  We present the history of fourth order metric theories of gravitation from
its beginning in 1918 until 1988.


title: Quantum black holes from null expansion operators

abstract:
  Using a recently developed quantization of spherically symmetric gravity
coupled to a scalar field, we give a construction of null expansion operators
that allow a definition of general, fully dynamical quantum black holes. These
operators capture the intuitive idea that classical black holes are defined by
the presence of trapped surfaces, that is surfaces from which light cannot
escape outward. They thus provide a mechanism for classifying quantum states of
the system into those that describe quantum black holes and those that do not.
We find that quantum horizons fluctuate, confirming long-held heuristic
expectations. We also give explicit examples of quantum black hole states. The
work sets a framework for addressing the puzzles of black hole physics in a
fully quantized dynamical setting.


title:
Kink instability and stabilization of the Friedmann universe with scalar
  fields

abstract:
  The evolution of weak discontinuity is investigated in the flat FRW universe
with a single scalar field and with multiple scalar fields. We consider both
massless scalar fields and scalar fields with exponential potentials. Then we
find that a new type of instability, i.e. kink instability develops in the flat
FRW universe with massless scalar fields. The kink instability develops with
scalar fields with considerably steep exponential potentials, while less steep
exponential potentials do not suffer from kink instability. In particular,
assisted inflation with multiple scalar fields does not suffer from kink
instability. The stability of general spherically symmetric self-similar
solutions is also discussed.


title: Creation of Kerr-de Sitter Black Hole in All Dimensions

abstract:
  We discuss the quantum creation scenario of a Kerr-de Sitter black hole in
all dimensions. We show that its relative creation probability is the
exponential to the entropy of the black hole, using a topological argument. The
action of the regular Euclidean instanton can be calculated in the same way.


title:
Dynamics of gravitational field within a wave front and thermodynamics
  of black holes

abstract:
  Hamiltonian dynamics of gravitational field contained in a spacetime region
with boundary $S$ being a null-like hypersurface (a wave front) is discussed.
Complete Hamiltonian formula for the dynamics (with no surface integrals
neglected) is derived. A quasi-local proof of the first law of black holes
thermodynamics is obtained as a consequence, in case when $S$ is a
non-expanding horizon. The zeroth law and Penrose inequalities are discussed
from this point of view.


title:
Recent verifications of a new relativity principle and a new
  gravitational theory based on properties of light

abstract:
  Recent astronomical observations verify the new scenario resulting from new
conservation laws and a new relativity principle fixed either by dual
properties of light or by new gravitational (G) tests and the Einstein's
equivalence principle. This scenario is radically different from the classical
one. During a free fall, the relative masses of free bodies, with respect to
the observer at rest in a G field, remain constants. The energy released during
the stops in different G potentials (GP) comes not from the G field but from
the bodies. The relative properties of the bodies at rest with respect to the
observer depend on the differences of GP between the bodies and the observer.
The increase of GP due to universe expansion expands bodies in identical
proportion. The universe age may be infinite. Its entropy is conserved because
the new black hole, without singularity, after absorbing radiation, explodes
regenerating new gas that transforms dark galaxies into luminous ones. Galaxies
evolve, indefinitely in closed cycles with luminous and dark periods. All of
their phases are found anywhere in the universe. They solve fundamental
dilemmas like dark matter and radiation backgrounds


title:
The challenge to reliably measure the general relativistic
  Lense-Thirring effect with a few percent accuracy

abstract:
  In this paper we critically analyze the so far performed and proposed tests
for measuring the general relativistic Lense-Thirring effect in the
gravitational field of the Earth with some of the existing accurately tracked
artificial satellites. The impact of the 2nd generation GRACE-only
EIGEN-GRACE02S Earth gravity model and of the 1st CHAMP+GRACE+terrestrial
gravity combined EIGEN-CG01C Earth gravity model is discussed. The role of the
proposed LARES is discussed as well.

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


title:
Time asymmetric spacetimes near null and spatial infinity. II.
  Expansions of developments of initial data sets with non-smooth conformal
  metrics

abstract:
  This article uses the conformal Einstein equations and the conformal
representation of spatial infinity introduced by Friedrich to analyse the
behaviour of the gravitational field near null and spatial infinity for the
development of initial data which are, in principle, non-conformally flat and
time asymmetric. This article is the continuation of the investigation started
in Class. Quantum Grav. 21 (2004) 5457-5492, where only conformally flat
initial data sets were considered. For the purposes of this investigation, the
conformal metric of the initial hypersurface is assumed to have a very
particular type of non-smoothness at infinity in order to allow for the
presence of non-Schwarzschildean initial data sets in the class under study.
The calculation of asymptotic expansions of the development of these initial
data sets reveals --as in the conformally flat case-- the existence of a
hierarchy of obstructions to the smoothness of null infinity which are
expressible in terms of the initial data. This allows for the possibility of
having spacetimes where future and past null infinity have different degrees of
smoothness. A conjecture regarding the general structure of the hierarchy of
obstructions is presented.


title: Modified Friedman scenario from the Wheeler-DeWitt equation

abstract:
  We consider the possible modification of the Friedman equation due to
operator ordering parameter entering the Wheeler-DeWitt equation.


title:
Error and symmetry analysis of Misner's algorithm for spherical harmonic
  decomposition on a cubic grid

abstract:
  Computing spherical harmonic decompositions is a ubiquitous technique that
arises in a wide variety of disciplines and a large number of scientific codes.
Because spherical harmonics are defined by integrals over spheres, however, one
must perform some sort of interpolation in order to compute them when data is
stored on a cubic lattice. Misner (2004, Class. Quant. Grav., 21, S243)
presented a novel algorithm for computing the spherical harmonic components of
data represented on a cubic grid, which has been found in real applications to
be both efficient and robust to the presence of mesh refinement boundaries. At
the same time, however, practical applications of the algorithm require
knowledge of how the truncation errors of the algorithm depend on the various
parameters in the algorithm. Based on analytic arguments and experience using
the algorithm in real numerical simulations, I explore these dependencies and
provide a rule of thumb for choosing the parameters based on the truncation
errors of the underlying data. I also demonstrate that symmetries in the
spherical harmonics themselves allow for an even more efficient implementation
of the algorithm than was suggested by Misner in his original paper.


title: Complex geometry and pre-metric electromagnetism

abstract:
  The intimate link between complex geometry and the problem of the pre-metric
formulation of electromagnetism is explored. In particular, the relationship
between 3+1 decompositions of R4 and the decompositions of the vector space of
bivectors over R4 into real and imaginary subspaces relative to a choice of
complex structure is emphasized. The role of the various scalar products on the
space of bivectors that are defined in terms of a volume element on R4 and a
complex structure on the space of bivectors that makes it C-linear isomorphic
to C3 is discussed in the context of formulation of a theory of
electromagnetism in which the Lorentzian metric on spacetime follows as a
consequence of the existence of electromagnetic waves, not a prior assumption.


title:
Lunar Laser Ranging Science: Gravitational Physics and Lunar Interior
  and Geodesy

abstract:
  Laser pulses fired at retroreflectors on the Moon provide very accurate
ranges. Analysis yields information on Earth, Moon, and orbit. The highly
accurate retroreflector positions have uncertainties less than a meter. Tides
on the Moon show strong dissipation, with Q=33 \pm 4 at a month and a weak
dependence on period. Lunar rotation depends on interior properties; a fluid
core is indicated with radius ~20% that of the Moon. Tests of relativistic
gravity verify the equivalence principle to \pm 1.4 x 10^{-13}, limit
deviations from Einstein's general relativity, and show no rate for the
gravitational constant $\dot{G}/G$ with uncertainty 9 x 10^{-13} 1/yr.


title: Simple Cosmological Model with Relativistic Gas

abstract:
  We construct simple and useful approximation for the relativistic gas of
massive particles. The equation of state is given by an elementary function and
admits analytic solution of the Friedmann equation, including more complex
cases when the relativistic gas of massive particles is considered together
with radiation or with dominating cosmological constant. The model of
relativistic gas may be interesting for the description of primordial Universe,
especially as a candidate for the role of a Dark Matter.


title: Interacting with the fifth dimension

abstract:
  Some new five dimensional minimal scalar-Einstein exact solutions are
presented. These new solutions are tested against various criteria used to
measure interaction with the fifth dimension.


title: Accelerating multidimensional cosmologies with scalar fields

abstract:
  We study multidimensional cosmological models with a higher-dimensional
product manifold, that consists of spherical and flat spaces, in the presence
of a minimal free scalar field. Dynamical behaviour of the model is analyzed
both in Einstein and Brans-Dicke conformal frames. For a number of particular
cases, it is shown that external space-time undergoes an accelerated expansion


title:
Brans-Dicke gravity and the capture of stars by black holes: some
  asymptotic results

abstract:
  In the context of star capture by a black hole, a new noticeable difference
between Brans-Dicke theory and general relativity gravitational radiation is
pointed out. This feature stems from the non-stationarity of the black hole
state, barring Hawking's theorem.


title: Brief History of Black-Holes

abstract:
  We show that the gravitational collapse of a black-hole terminates in the
birth of a white-hole, due to repulsive gravitation (antigravitation); in
particular, the infinite energy density singularity does NOT occur.


title: Accelerated observers and gravitational radiation

abstract:
  We evaluate the energy-momentum of the gravitational field of a Schwarzschild
black hole of mass M in the frame of a moving observer that asymptotically
undergoes a Lorentz boost. The analysis is carried out in the framework of the
teleparallel equivalent of general relativity (TEGR). We find that the total
expression for the energy-momentum of the gravitational field is similar to the
usual relativistic expression for the energy-momentum four-vector of a particle
of inertial mass M under a Lorentz boost in flat space-time. Moreover we
conclude that if the observer accelerates with respect to the black hole he
will experience gravitational energy radiation, in similarity to the expected
radiation of an accelerated charged particle in electrodynamics. We show that
the increase of the mass of the black hole by the usual factor gamma as
observed in the moving frame, which is a typical feature of special relativity
if the black hole is considered asymptotically as a body of mass M, is due to
gravitational radiation.


title:
Approximate stress-energy tensor of the massless spin-1/2 field in
  Schwarzschild spacetime

abstract:
  The approximate stress-energy tensor of the conformally invariant massless
spin-1/2 field in the Hartle-Hawking state in the Schwarzschild spacetime is
constructed. It is shown that by solving the conservation equation in conformal
space and utilizing the regularity conditions in a physical metric one obtains
the stress-energy tensor that is in a good agreement with the numerical
calculations. The back reaction of the quantized field upon the spacetime
metric is briefly discussed.


title:
A critical analysis of a recent test of the Lense-Thirring effect with
  the LAGEOS satellites

abstract:
  We discuss the impact of the present-day uncertainties in the recently
released CHAMP and/or GRACE Earth gravity models on the measurement of the
Lense-Thirring effect with the nodes of the LAGEOS satellites. Also the role of
the secular variations Jdots of the even zonal harmonics is quantitatively
assessed via numerical simulations and tests. While the systematic error due to
the static part of the geopotential ranges from 4% (EIGEN-GRACE02S) to 9%
(GGM02S), the impact of the Jdots amounts to 13% over 11 years. This yields a
19% 1-sigma total error in the test recently performed with EIGEN-GRACE02S.


title: Black holes: a prediction of theory or phantasy?

abstract:
  We argue for black holes do not represent a strict consequence of general
relativity.


title: General Relativity Histories Theory

abstract:
  The canonical description is based on the prior choice of a spacelike
foliation, hence making a reference to a spacetime metric. However, the metric
is expected to be a dynamical, fluctuating quantity in quantum gravity. After
presenting the developments in the History Projection Operator histories theory
in the last seven years--giving special emphasis on the novel temporal
structure of the formalism--we show how this problem can be solved in the
histories formulation of general relativity. We implement the 3+1 decomposition
using metric-dependent foliations which remain spacelike with respect to all
possible Lorentzian metrics. This allows us to find an explicit relation of
covariant and canonical quantities which preserves the spacetime character of
the canonical description. In this new construction we have a coexistence of
the spacetime diffeomorphisms group Diff(M) and the Dirac algebra of
constraints.


title: Chaos of Yang-Mills Field in Class A Bianchi Spacetimes

abstract:
  Studying Yang-Mills field and gravitational field in class A Bianchi
spacetimes, we find that chaotic behavior appears in the late phase (the
asymptotic future). In this phase, the Yang-Mills field behaves as that in
Minkowski spacetime, in which we can understand it by a potential picture,
except for the types VIII and IX. At the same time, in the initial phase (near
the initial singularity), we numerically find that the behavior seems to
approach the Kasner solution. However, we show that the Kasner circle is
unstable and the Kasner solution is not an attractor. From an analysis of
stability and numerical simulation, we find a Mixmaster-like behavior in
Bianchi I spacetime. Although this result may provide a counterexample to the
BKL (Belinskii, Khalatnikov and Lifshitz) conjecture, we show that the BKL
conjecture is still valid in Bianchi IX spacetime. We also analyze a
multiplicative effect of two types of chaos, that is, chaos with the Yang-Mills
field and that in vacuum Bianchi IX spacetime. Two types of chaos seem to
coexist in the initial phase. However, the effect due to the Yang-Mills field
is much smaller than that of the curvature term.


title: On the existence of initial data containing isolated black holes

abstract:
  We present a general construction of initial data for Einstein's equations
containing an arbitrary number of black holes, each of which is instantaneously
in equilibrium. Each black hole is taken to be a marginally trapped surface and
plays the role of the inner boundary of the Cauchy surface. The black hole is
taken to be instantaneously isolated if its outgoing null rays are shear-free.
Starting from the choice of a conformal metric and the freely specifiable part
of the extrinsic curvature in the bulk, we give a prescription for choosing the
shape of the inner boundaries and the boundary conditions that must be imposed
there. We show rigorously that with these choices, the resulting non-linear
elliptic system always admits solutions.


title:
Recent analytical and numerical techniques applied to the Einstein
  equations

abstract:
  Combining deeper insight of Einstein's equations with sophisticated numerical
techniques promises the ability to construct accurate numerical implementations
of these equations. We illustrate this in two examples, the numerical evolution
of ``bubble'' and single black hole spacetimes. The former is chosen to
demonstrate how accurate numerical solutions can answer open questions and even
reveal unexpected phenomena. The latter illustrates some of the difficulties
encountered in three-dimensional black hole simulations, and presents some
possible remedies.


title: Computations of primordial black hole formation

abstract:
  Results are presented from general relativistic numerical computations of
primordial black-hole formation during the radiation-dominated era of the
universe. Growing-mode perturbations are specified within the linear regime and
their subsequent evolution is followed as they become nonlinear. We use a
spherically symmetric Lagrangian code and study both super-critical
perturbations, which go on to produce black holes, and sub-critical
perturbations, for which the overdensity eventually disperses into the
background medium. For super-critical perturbations, we confirm the results of
previous work concerning scaling-laws but note that the threshold amplitude for
a perturbation to lead to black-hole formation is substantially reduced when
the initial conditions are taken to represent purely growing modes. For
sub-critical cases, where an initial collapse is followed by a subsequent
re-expansion, strong compressions and rarefactions are seen for perturbation
amplitudes near to the threshold. We have also investigated the effect of
including a significant component of vacuum energy and have calculated the
resulting changes in the threshold and in the slope of the scaling law.


title: Gravitationally induced electromagnetism at the Compton scale

abstract:
  It is shown that Einstein gravity tends to modify the electric and magnetic
fields appreciably at distances of the order of the Compton wavelength. At that
distance the gravitational field becomes spin dominated rather than mass
dominated. The gravitational field couples to the electromagnetic field via the
Einstein-Maxwell equations which in the simplest model causes the electrostatic
field of charged spinning particles to acquire an oblate structure relative to
the spin direction. For electrons and protons, a pure Coulomb field is
therefore likely to be incompatible with general relativity at the Compton
scale. In the simplest model, the magnetic dipole corresponds to the Dirac
g-factor, g=2. Also, it follows from the form of the electric field that the
electric dipole moment vanishes, in agreement with current experimental limits
for the electron. Quantitatively, the classical Einstein-Maxwell theory
predicts the magnetic and electric dipoles of the electron to an accuracy of
about one part in 10^{-3} or better. Going to the next multipole order, one
finds that the first non-vanishing higher multipole is the electric quadrupole
moment which is predicted to be -124 barn for the electron. Any non-zero value
of the electric quadrupole moment for the electron or the proton would be a
clear sign of curvature due to the implied violation of rotation invariance.
There is also a possible spherical modification of the Coulomb force
proportional to r^{-4}. However, the size of this effect is well below current
experimental limits. The corrections to the hydrogen spectrum are expected to
be small but possibly detectable.