**Title and Abstract of Talks
**

In this talk I will provide an overview of a powerful variational

description of relativistic fluid dynamics due to Brandon Carter.

I will compare the formulation to the "standard" approach, and

discuss how one can model systems with several independent

dynamical degrees of fluids. A typical example is provided by

a superfluid neutron star, and I will discuss recent result in

that problem area. A key poit is the introduction of the entrainment

effect, by means of which the different fluids are coupled

and which can lead to velocities and momenta not being parallel.

Finally, I will discuss the challenges that have to be met in

the future, in particular ones associated with dissipation in relativistic fluids.

I will discuss possible modifications of Newton's law at short and

large distance scales in models of extra dimensions and compare

with present experimental bounds.

models from string theory. In the most well-studied scenario, brane

inflation, the inflationary phase typically ends with a phase transition,

leading to the production of a network of cosmic (super)strings. In this

talk I will discuss the cosmological evolution of such string networks and

point out several differences to usual field theory strings arising in

more conventional theories. The fact that these differences could in

principle be observed, renders cosmic strings an excellent probe for the

physics of the early universe.

We will present the basics of a gauge-boson mass-generating mechanism in a

higher-dimensional (essentially Kaluza-Klein) setting, devoid of the

standard Higgs sector. We will also examine the possibility of applying the

idea in D=4, as a realistic geometric alternative to the standard Higgs

mechanism.

We consider the problem of a scalar field, non-minimally coupled to gravity

through a $-\xi\phi^{2}R$ term, in the presence of a Brane. Exact solutions,

for a wide range of values of the coupling parameter $\xi$, for both $\phi$-dependent

and $\phi$-independent Brane tension, are derived and their behaviour is studied.

In the case of a Randall-Sundrum geometry, a class of the resulting scalar field solutions

exhibits a folded-kink profile. We go beyond the Randall-Sundrum geometry

studying general warp factor solutions in the presence of a kink scalar. Analytic and

numerical results are provided for the case of a Brane or for smooth geometries, where

the scalar field acts as a thick Brane. It is shown that finite geometries with warp

factors that asymptotically decrease exponentially are realizable for a wide range

of parameter values.

**Speaker:** S. Bonanos

**Title: ***The choice of the Bondi radial coordinate and the physical
interpretation of the news function in axisymmetric space-times.*

In the Bondi formulation of the axisymmetric vacuum Einstein

equations, we argue that the ``surface area'' coordinate condition

determining the ``radial'' coordinate is part of the initial data and can

be chosen in a way that gives information about the physical problem

whose solution is sought. We suggest a coordinate choice that follows

from interpreting the radial coordinate, near infinity, as the (inverse

of the) Newtonian potential. In this way, physical quantities that

specify the problem (mass moments) enter the equations from the very

beginning and play the role of ``source" terms. A natural identification

of the news function in terms of these ``source" terms is suggested,

leading to an expression for the radiated energy that formally differs

from the standard quadrupole formula. We consider ways to reconcile this

conclusion with the classical result.

**Speaker:** P. Boonserm

**Title:** *Generating perfect fluid spheres in general relativity.*

**Abstract:**

Ever since Karl Schwarzschild's 1916 discovery of the spacetime geometry

describing the interior of a particular idealized general relativistic star-a

static spherically symmetric blob of fluid with position-independent

density-the general relativity community has continued to devote considerable

time and energy to understanding the general-relativistic static perfect

fluid sphere. Over the last 90 years a tangle of specific perfect fluid

spheres has been discovered, with most of these specific examples seemingly

independent from each other. To bring some order to this collection, we

develop several new transformation theorems that map perfect fluid spheres

into perfect fluid spheres. These transformation theorems sometimes lead to

unexpected connections between previously known perfect fluid spheres,

sometimes lead to new previously unknown perfect fluid spheres, and in

general can be used to develop a systematic way of classifying the set of all

perfect fluid spheres.

**Speaker:** C. Cattoen

**Title: ***Necessary and sufficient conditions for big bangs, bounces,
crunches,
rips, sudden singularities and extremality events.*

Abstract:

had traditionally been thought to be limited to the “big bang”, and possibly a

“big crunch”. However, over the last few years, the zoo of cosmological singularities

considered in the literature has become considerably more extensive, with “big rips”

and “sudden singularities” added to the mix, as well as renewed interest in non-singular

cosmological events such as “bounces” and “turnarounds”. In this talk, I will present

an extensive catalogue of such cosmological milestones, both at the kinematical and dynamical

level.First, using generalized power series, purely kinematical definitions of these cosmological

events are provided in terms of the behaviour of the scale factor a(t). The notion of a

“scale-factor singularity” is defined, and its relation to curvature singularities (polynomial

and differential) is explored. Second, dynamical information is extracted by using the Friedmann

equations (without assuming even the existence of any equation of state) to place constraints

on whether or not the classical energy conditions are satisfied at the cosmological milestones.

Since the classification is extremely general, and modulo certain technical assumptions complete,

the corresponding results are to a high degree model-independent.

**Speaker:** C.
Charmousis

**Title: ***Solution generating methods for stationary and axisymmetric
metrics.***
Abstract:
**We will present solution generating methods in Einstein gravity

for stationary metrics with axial symmetry in the presence of a

cosmological constant. We will relate our findings to the classic works of

Papapetrou and Ernst in 4 dimensional general relativity, and we will

extend them for a cosmological constant and in higher dimensions than

four. We will discuss higher dimensional black hole solutions such as the

black ring, their Kaluza-Klein reduction and other construction methods

relating lower to higher dimensional spacetimes.

**Speaker:** M.
Chichikina

**Title: ***Group Analysis in Quantum Gravity.*

**Abstract:**

New scheme of quantization of nonlinear systems is proposed.

We quantize bozon fields on nontrivial classical background.

Using of Bogoliubov group variables permits to avoid difficulties:

1. nonevident conservation laws while perturbation theory is used.

2. zero-mode problem

The scheme permits to quantize, for example, gravitational field in the

neubourgood of exact solution of Einstein equations, taking into account

conservation laws explisitly in any order of perturbation theory.

**Speaker:** D. Christodoulou

**Title: ***The formation of shocks in 3-dimensional fluids.*

**Abstract:
**In the lecture I shall present a summary of the contents of my recent 1100

page monograph with this title. The monograph considers the relativistic

Euler equations in three space dimensions for a perfect fluid with

an arbitrary equation of state. We consider regular initial data on a

spacelike hyperplane in Minkowski spacetime which

outside a sphere coincide with the data corresponding to a constant state.

We consider the restriction of the initial data to the exterior of a concentric

sphere and we consider the maximal classical development of this data.

Then, under a suitable restriction on the size of the departure of the

initial data from those of the constant state, we prove certain theorems

which give a complete description of the maximal classical development.

In particular, the theorems give a detailed description of the geometry of

the boundary of the domain of the maximal classical development and a detailed

analysis of the behavior of the solution at this boundary.

A complete picture of shock formation in three-dimensional fluids is thereby

obtained. Also, sharp sufficient conditions on the initial data for the formation

of a shock in the evolution are established and sharp upper and bounds for

the time required for the onset of shock formation are derived.

and show how fundamentally independent arguments seem to converge to one

particular type of it. On a second, parallel theme, we present a canonical

*-product, and the associated deformed integral, with simple, trace-like

properties.

**Speaker:** A.
Corichi

**Title: ***Microscopic back holes in loop quantum gravity.
*

quantum theory of the gravitational field. An importat test that every such

framework should satisfy is to account for the microscopic degrees of freedom

of black holes. The approach to black hole entropy within loop quantum gravity

will be reviewed, together with recent analytical results. Next we shall

discuss new numerical results in entropy counting for small black holes that

uniquely fix the value of the Barbero-Immirzi parameter.

**Speaker:** S. Cotsakis

**Title: ***The Dominant Balance in Cosmology.***
Abstract:
**After a short discussion reviewing the basic issues of the

singularity vs completeness puzzle in general relativity, we introduce the

basic features of a new technique, the method of asymptotic splittings,

designed to deal with the nature of spacetimes near their singularities. We

focus on the more elementary parts, namely, the dominant balance and

asymptotic decompositions of vector fields, and then exploit the results to

discuss recent kinds of cosmological singularities including the so-called

sudden future singularities. Finally we remark on the general applicability

of the technique in general relativity.

Abstract:

We consider scalar and axial gravitational perturbations of black hole

solutions in brane world scenarios. We show that perturbation

dynamics is surprisingly similar to the Schwarzschild case with strong

indications that the models are stable. Quasinormal modes and late-time

tails are discussed. We also study the thermodynamics of these scenarios

verifying the universality of Bekenstein's entropy bound as well as the

applicability of 't Hooft's brickwall method.

The properties of a massless string endowed with intrinsic spin are discussed.

Even though the spacetime is Minkowskian geometrically, it has a

nontrivial topology due to a horizon located at r =0, similar with

the Rindler spacetime. The Sagnac time delay is calculated and proves

to be constant. We conjecture the spin of an elementary particle

originates in the frame dragging effect produced by the rotation

of the source. The radial acceleration of a rotating test particle

depends upon the sense of rotation due to the Planck length

entering the line element.

To investigate whether quantum entanglement between the inside and

outside of a black hole can give rise to Bekenstein-Hawking entropy, we

first compute the entanglement entropy of a quantum field, by tracing

over its degrees of freedom inside a spherical volume. We show that this

entropy is proportional to the area of the sphere when the field is in

its ground state, a generic coherent state or a class of squeezed

states. However, it is proportional to a power of area less than unity

when it is in an excited state. We discuss its generalisation to curved

spacetimes and implications of our results to black hole entropy. We

also identify the location of the degrees of freedom which give rise to

entanglement entropy.

of Vector Fields.

The closed-universe-recollapse conjecture for the existence of

all-encompassing future singularities in Bianchi IX vacuum, dust and perfect

fluid (P=kρ) space-times is shown to be correct using the method of

asymptotic decomposition of vector fields. Various physically relevant cases

for the ratio P/ρ are examined and analyzed and exact expressions for the

expansions of the dynamical variables detailing the nature of the universe

near the singularity are derived.

The classical Einstein's equations for the two ``Bianchi types'' in

(2+1)-dimensions coupled to a general scalar field are laid down and

completely integrated. The corresponding Wheeler-DeWitt

equations are presented and solved for particular configurations.

generalize the Bargmann-Wigner formalism for higher spins to be compatible

with other formalisms for bosons. Relations with dual electrodynamics, with

the Ogievetskii-Polubarinov notoph and the Weinberg 2(2J+1) theory are

found. Next, we introduce the dual analogues of the Riemann tensor and

derive corresponding dynamical equations in the Minkowski space. Relations

with the Marques-Spehler chiral gravity theory are discussed.

**Speaker: **O. Efthimiou

Title: *Graviton emission in the bulk from higher dimensional
Schwarzschild black holes.***
Abstract:
**In this talk we consider the evaporation of (4+n)-dimensional

non-rotating black holes into gravitons. We calculate the energy

emission rate for gravitons in the bulk obtaining analytical solutions

of the master equation satisfied by all three types (S,V,T) of

gravitational perturbations. Our results, valid in the low-energy

regime, show a vector radiation dominance for every value of n, while

the relative magnitude of the energy emission rate of the subdominant

scalar and tensor radiation depends on n. The calculated low-energy

emission rate, for all types of degrees of freedom decreases with n,

although the full energy emission rate, integrated over all

frequencies, is expected to increase with n, as in the previously

studied case of a bulk scalar field.

What is the gravitational field of a high energy photon in

a given state of its polarization? To attack this problem we consider

its classical analogue. Namely, we obtain exact solutions of the Einstein

equations for the gravitational field created by a beam-pulse of

spinning radiation (gyraton) in a D-dimensional spacetime. First we

demonstrate that these solutions belong to the class of metrics for

which all scalar invariants constructed from the curvature and its

covariant derivatives vanish. Next, we show that the vacuum Einstein

equations for a gyraton reduce to a linear problem in (D-2)-dimensional

Euclidean space. A general solution of these equations is obtained.

We construct gyraton-type solutions of the vacuum Einstein equations

and discuss their properties. We also discuss generalizations of the

gyraton metrics to the case when a gyraton is charges or is moving

in the asymptotically AdS spacetime. Possible applications to the

problem of mini-black-hole production in the collision of highly

relativistic particles is briefly discussed.

and Modified Symmetries.

I will first recall why quantum reference frames are of a key importance

in the understanding of the quantum gravity physics.

I will then study a toy model where one can construct quantum reference

frames, and show how in the semi classical limit they naturally imply a

deformation of the symmetries.

The toy model therfore provides another hint that in the semi classical

regime of quantum gravity one should have a deformation of the symmetries

such as met in Deformed Special Relativity.

Title:

Abstract:

nonperturbative solutions of gauge theories with spontaneous

symmetry breaking, namely monopoles and sphalerons.

Although the total mass within the cosmological horizon of these configurations is finite,

their mass evaluated at timelike infinity generically diverges for most values

of the cosmological constant. Thus, no finite energy monopoles and sphalerons

can exist for the currently accepted value of the cosmological constant.

We consider the generation of thick brane configurations in a 5D Riemannian

space time. In this framework, we show how 4D gravity can be localized on a

scalar thick brane which does not necessarily respect reflection symmetry,

generalizing in this way several previous models based on the Randall-Sundrum

(RS) system and avoiding both, the restriction to orbifold geometries and the

introduction of the branes in the action by hand. We first obtain a thick

brane solution that preserves 4D Poincare' invariance and breaks Z_2-symmetry

along the extra dimension which, indeed, can be either compact or extended. In

the non-compact case, this field configuration represents a thick brane with

positive energy density centered at y=c_2, whereas pairs of thick branes arise

in the compact case. We also recast the wave equations of the transverse

traceless modes of the linear fluctuations of the classical background into a

Schrodinger's equation form with a volcano potential of finite bottom. We

solve Schrodinger equation for the massless zero mode m^2=0 and obtain a

single bound wave function which represents a stable 4D graviton (without

tachyon modes). We also get a continuum gapless spectrum of KK states with

m^2>0 that are suppressed at y=c_2 and turn asymptotically into plane waves.

We found a particular case in which the Schrodinger equation can be solved

for all m^2>0, giving us the opportunity of studying analytically the massive

modes of the spectrum of KK states, a rare fact when considering thick brane

configurations.

by using the simple observation that a three-brane in a

six-dimensional bulk is flat. A model is described in which

Standard Model vacuum energy is always absorbed by the transverse

space. The latter is a tear-drop like space with a conical

singularity, which preserves bulk supersymmetry and gives rise to

conventional macroscopic 4D gravity with no cosmological constant.

Its cone acts like a drain depleting vacuum energy from the

three-brane to the tear drop increasing its volume. We stress that

although gravity is treated classically, Standard Model is handled

quantum-field theoretically and the model is robust against

Standard Model corrections and particular details.

Dynamical Cosmological Term Lambda.

string cosmological model by considering three different forms of

dynamical variable $\Lambda$: $\Lambda \sim \left

(\frac{\dot{R}}{R}\right)^2,$ $\Lambda \sim

\left(\frac{\ddot{R}}{R}\right)$ and $\Lambda \sim \rho$. It is

found that, the connecting free parameters of the models with

cosmic matter and vacuum energy density parameters are equivalent,

in the context of higher dimensional space time.

universe by exploiting the behaviours of three functions, namely, the Hubble expansion

rate, the scale factor and the Bel-Robinson energy of these universes. We use the Bel-Robinson

energy to test whether the character of the singularity present in any particular exact solution

of the field equations describing such universes depends on the given spatial geometry.

We further examine the relation between the existence of closed trapped surfaces and possible

bounds on the Bel-Robinson energy in these types of universes.

Speaker:

relativistic stars. The study involves spacetime modes of fast rotating

stars and stars in scalar-tensor theory of gravity.

Speaker:

anisotropic structure of fields which are depended on the position and the

direction (velocity).In this framework the generalized FRW-metric,Friedman

and Raychadouri equations are studied. In some cases a cosmological magnetic

field is considered in relation with the physical geometry of space-time

in which Cartan connection has a fundamental role. As well a corelation with the

inflation is examined on the basis of the aforementioned metric structure.

Speaker:

generating the time evolution of the Dirac wave function

in relativistic quantum mechanics is not hermitian with respect to

the covariantly defined inner product whenever the background

metric is time dependent. An alternative, hermitian, Hamiltonian is

found and is shown to be directly related to the canonical

field energy. Further, the relation of the Hamiltonian to the generator of

time translations in the second quantized theory is established.

Title:

Abstract:

Unruh-DeWitt particle detector whose coupling to a scalar field on

Minkowski space is regularised by a finite spatial profile. We show,

under mild technical assumptions, that the zero size limit of the

detector response is well defined, independent of the choice of the

profile function, and given by a manifestly finite integral formula

that no longer involves epsilon-regulators or limits. The thermal result

for uniform acceleration is recovered as a special case. Applications to

quotients of Minkowski space are discussed, with a view to probing the

topology of quantum black holes by particle detectors.

Speaker:

Title:

Abstract:

universe from observations. A satisfactory explanation of this acceleration is

perhaps the greatest theoretical challenge in cosmology. Within the

framework of general relativity, the acceleration typically originates from a

dark energy field with effectively negative pressure. Alternatively, it is

possible that there is no dark energy, but instead an infrared modification of

general relativity on very large scales that accounts for late-time

acceleration. I will review various models of modified gravity that have been

proposed, looking at their dynamics and perturbations and how they

compare against observational data.

Speaker:

Title:

Abstract:

Rovelli which proposes a intrinsic definition of the notion of "physical flow of time" that

may be interesting in a quantum gravity context. Here we shall illustrate the TTH by emphasizing some

applications to general relativity and quantum field theories in curved spacetimes. Especially we

will present our adaptation of the Unruh effect (i.e. the fact that the vacuum state of a quantum

field theory on Minkovski spacetime is viewed as a thermal state for an eternal observer with constant

acceleration) to observers with finite lifetime. Also we aim at discussing some recent application of the TTH

to de Sitter space.

Speaker:

Title:

Abstract:

varying speed of light using the method of asymptotic splittings.

Speaker:

Title:

Abstract:

on a body of $m$ dimensions in a space of $n$ dimensions. Early work on

moving mirrors is generalised to cosmological branes moving in higher

dimensions. This raises the question-can branes radiate away their

cosmological constant? (Answer=no)

Speaker:

Title:

Abstract:

-Trautman equation and give its possible symmetric

solutions and symmetry reductions.

Speaker:

Title:

Abstract:

literature was made: the Full Gold (FG) dataset (157 data points 0 < z < 1.75), a

Truncated Gold (TG) dataset (140 data points 0 < z < 1) and the most recent Supernova

Legacy Survey (SNLS) dataset (115 data points 0 < z < 1). It was found that the best fit

dynamical w(z) obtained from the SNLS dataset does not cross the PDL w = -1 and

remains above and close to the w = -1 line for the whole redshift range 0 < z < 1 showing

no evidence for phantom behaviour. In contrast, the best fit dynamical w(z) obtained

from the Gold datasets (FG and TG) clearly crosses the PDL and departs significantly

from the PDL w = -1 line while the LCDM parameter values are about 2 \sigma away

from the best fit w(z). Also for the Gold dataset a scalar-tensor theory was reconstructed,

for which the best fit form of w(z) was also found to cross the phantom divide line.

Speaker:

Title:

Abstract:

warped Salam-Sezgin model with codimension-2 branes. We focus on the

perturbations which mix with the dilaton. We show that the scalar

fluctuations analysis can be reduced to studying two scalar modes

of constant wavefunction, plus modes of non-constant wavefunction which

obey a single Schrodinger equation. From the obtained explicit solution of

the scalar modes, we point out the importance of the non-constant modes in

describing the four dimensional effective theory. This observation remains

true for the unwarped case and was neglected in the relevant literature.

Furthermore, we show that due to these modes, the warped solutions can be

unstable for a certain region of the parameter space.

Speaker:

Title:

Abstract:

contained in a metric tensor field is addressed. The codification of the problem leads to

a criterion, which in turn, reduces the initial problem to that of solving a system of partial

differential equations of the first order

Speaker:

Title:

Abstract:

interacts non-minimally with gravity, via a possible interaction term of the form -(1/2) \xi R \phi^2.

By solving numerically the corresponding Einstein equations with the scalar field, in the case of

a \phi^4 potential, we obtain three classes of solutions with different features, in appropriate

regions of the non-minimal coupling \xi. As a possible implication, we examine the possibility

to construct brane models which incorporate a layer-phase mechanism for the localization of

ordinary particles on the brane.

Speaker:

Title:

Abstract:

perturbative approach, which is appropriate for investigating the low

and mild nonlinear dynamical regimes. In this talk, we present the

perturbative framework to describe, in the time domain, the nonlinear

coupling between the radial and nonradial perturbations of spherically

symmetric and perfect fluid compact stars. This particular coupling

can be described by gauge invariant quantities that obeys a system of

partial differential equations with source terms, which are made up of

product of first order radial and nonradial perturbations. We report

the results of numerical simulations that exhibit in the stellar dynamics

and in the related gravitational wave signal some interesting nonlinear

effects, such as combination harmonics and resonances.

Speaker:

Title:

Abstract:

that the dark energy equation of state parameter $w$ may be

evolving with time and crossing the phantom divide barrier $w=-1$

at recent times. The confirmation of these indications by future

data would indicate that minimally coupled quintessence can not

reproduce the observed expansion rate $H(z)$ for any scalar field

potential. Here we explicitly demonstrate that scalar tensor

theories of gravity (extended quintessence) can predict crossing

of the phantom divide barrier. We reconstruct phenomenologically

viable scalar-tensor potentials $F(\Phi)$ and $U(\Phi)$ that can

reproduce a polynomial best fit expansion rate $H(z)$ and the

corresponding dark energy equation of state parameter $w(z)$

crossing the $w=-1$ line. The form of the reconstructed scalar

tensor potentials is severely constrained but is not uniquely

determined. This is due to observational uncertainties in the form

of $H(z)$ and also because a single observed function $H(z)$ does

not suffice for the reconstruction of the two potential functions

$F(\Phi)$ and $U(\Phi)$.

Speaker:

Title:

Abstract:

We study thermodynamics of various black hole families by means of

Ruppeiner geometry which is a one particular type of information geometry.

The Ruppeiner metric is defined as the negative of the Hessian of the thermodynamic

entropy function of the system with respect to the mechanically conserved parameters,

like mass, charge and spin in the case of black holes. The Ruppeiner metric has a

conformal counterpart called the Weinhold metric. We find that for many black hole

families, one or the other of these metrics is flat. The Ruppeiner metric, when it is

curved, tends to behave in a way that suggests that it is physically meaningful. Most

recent findings from the Ruppeiner information geometry in black hole thermodynamics

include the prediction of the thermodynamic stabilities of the Kerr black holes in all dimensions.

Speaker:

Title:

Abstract:

and truncation (elimination of most of KK modes) as a way to formulate

lower dimensional theories starting from higher dimensional ones. Then

one can get solutions of the higher dimensional theories through the

uplifting of solutions of the lower dimensional ones. I discuss also the

role of contraints to further reduce the degrees of freedom and I show its

connection with Dirac approach to gauge systems. Examples of succesfull

truncations will be given, as well as of solutions obtained by uplifting.

Speaker:

Inflation is the currently accepted explanation for the origin of

large-scale structure in the Universe by naturally providing a nearly

scale-invariant density perturbation at early times. In conventional

single-field inflationary models this perturbation is a Gaussian random

field to very high accuracy. I will discuss the possibility of enhanced

non-Gaussianity from multi-field models at a level possibly observable in

the near future. Hence, non-Gaussianity emerges as an additional probe of

the physics of the early Universe.

a toy model of the quantum collapse of more complicated objects. In 3+1 gravity

the possible Hamiltonians that describe this collapse (generated from the Israel

equation for shell motion) are so complicated that only numerical solutions are

possible. Even in the Newtonian analogue of this problem, where an analytic

solution exists, it is impossible to find analytic wave packets whose evolution

can tell us something about horizon formation. In 2+1 gravity, one possible

Hamiltonian is simple enough to allow us to carry out the entire canonical

quantization program analytically and allows us to study horizon formation.

black holes under conformal-flat condition.

importance. This particularly applies to Einstein's theory of gravity.

In my talk an analytical solution of the two-body problem will be

presented within a conformally truncated version of the Einstein field

equations. The solution represents a stationary gravitational field and

related herewith a conservative dynamics of two black holes with

Brill-Lindquist initial data. Various limiting cases of the solution

will be discussed including post-Newtonian expansion.

The ISCO will be given and it will be shown that for

circular orbits the ADM and Komar masses coincide.

We discuss properties of the axially symmetric static saddle point

solutions of SU(2) Yang-Mills-Higgs theory which represent composite

states of monopoles and antimonopoles and/or vortex rings. They are either

deformations of the topologically trivial sector or deformations of the

axially symmetric charge n multimonopole. The energy of these

configurations exceeds the Bogomol'nyi bound even in the limit of

vanishing scalar coupling. When the theory is coupled with gravity new

branches of the graviting monopoles/vortices emerges smoothly from these

flat space configurations. We discuss interpretation of the upper branche

configuration as a composite system consisting of Bartnik-McKinnon

solution of EYM theory and an outer multimonopole/vortex solution of the

EYMH theory.

Schwarzschild black hole to focus on whether we can extract any of its

physical properties from a direct detection of gravitational waves. We

adopt a black hole perturbation approach in a time domain, which is a

satisfactory approximation to illustrate a dust disk in a supermassive

black hole. We find that we can determine the radius of the disk by

using the power spectrum of gravitational waves and that our method to

extract the radius works for a disk of arbitrary density distribution.

Therefore we believe a possibility exists for determining the radius of

the disk from a direct observation of gravitational waves detected by

the Laser Interferometer Space Antenna.

f(R) gravity, has received considerable attention, mainly due to its

interesting applications in cosmology. However, the phenomenology of such

theories is not only relevant to cosmological scales, especially when it is

treated within the framework of the so called Palatini variation, an

independent variation with respect to the metric and the connection, which is

not considered a priopi to be the Levi-Civita connection of the metric. If this

connection has its standard geometrical meaning the resulting theory will be a

metric-affine theory of gravity, as will be discussed in this talk. The general

formalism will be presented and several aspects of the theory will be covered,

mainly focusing on the enriched phenomenology that such theories exhibit with

respect to General Relativity, relevant not only to large scales (cosmology)

but also to small scales (e.g. torsion).

general relativistic evolution of a differentially rotating supermassive star with toroidal

shape. We find that a large number of such models are unstable to nonaxisymmetric modes, which

leads to a fragmentation into self-gravitating, collapsing components. In the case

of one such fragment, we apply a simplified adaptive mesh refinement technique to follow the

evolution to the formation of an apparent horizon centered on the fragment. This is the first study

of the one-armed instability in full general relativity.

temperature fluctuations in the CMB and the corresponding predictions coming from inflationary models

are taken as confirmation of the quantum fluctuation origin of the seeds of cosmic structure. This

talk focuses on the transmutation of the original quantum fluctuations, which are essentially homogeneous and

isotropic-- arising as they do from an homogeneous and isotropic vacuum state-- into the classical

inhomogeneities and anisotropies that correspond to the observations. We argue that the standard accounts

of this aspect of the problem are not fully satisfactory and that there is a need for New Physics. This

New Physics would be presumably tied to some Quantum aspects of Gravitation, as suggested by R. Penrose, and we

show that a simple generalization of his ideas seems to be able to account for that transformation, and

have the features required for a successful phenomenology.

In this talk I give a short review of formulations of self-duality

conditions in the Einstein theory. Self-dual metrics are meaningful for

description of gravitational instantons, nonlinear gravitons and completely

integrable equations. I make some historical remarks with an emphasis on

little known results of physicists from the Hiroshima University in 1935.

I discuss relations between equations obtained by Plebanski, Husain or

Grant. In particular, I find the Backlund transformation between

the Plebanski and the Husain equations. I also show that the self-duality

conditions are equivalent to a pair of equations describing canonical

transformations in 2-dimensional phase spaces. Examples of solutions are

presented.

The theory of symmetries of systems of coupled, ordinary

differential equations (ODE's) is used to develop a concise

algorithm for cartographing the space of solutions to vacuum Bianchi

Einstein's Field Equations (EFE). The symmetries used are the well

known automorphisms of the Lie algebra for the corresponding

isometry group of each Bianchi Type, as well as the scaling and the

time reparameterization symmetry. Application of the method to Type

III results in: a) the recovery of all known solutions without prior

assumption of any extra symmetry, b) the enclosure of the entire

unknown part of the solution space into a single, second order ODE

in terms of one dependent variable and c) a partial solution to this

ODE, i.e. a new Type III vacuum solution. It is also

worth-mentioning the fact that the solution space is seen to be

naturally partitioned into three distinct, disconnected pieces: one

consisting of the known Siklos (pp-wave) solution, another occupied

by the Type III member of the known Ellis-MacCallum family and the

third described by the aforementioned ODE in which the new solution

resides. Lastly, preliminary results reported show that the unknown

part of the solution space for other Bianchi Types is described by a

strikingly similar ODE, pointing to a natural operational

unification as far as the problem of solving the cosmological EFE's

is concerned.

We study the cosmological evolution on a brane within a bulk with arbitrary

matter content. We consider a Friedmann-Robertson-Walker brane, invariantly

characterized by a six-dimensional group of isometries. We derive the

effective Friedmann and Raychaudhuri equations. We show that the Hubble

expansion rate on the brane depends on the covariantly defined integrated

mass in the bulk, which determines the energy density of the generalized

dark radiation. We present particular examples, some of which (such as the

radiating brane) describe energy exchange between the brane and the bulk.

We also consider the possibility of an induced gravity term on the brane.

The Friedmann equation has a branch characterized by an effective

cosmological constant and accelerated expansion. Another remarkable feature

is that the contribution from the generalized dark radiation appears with a

negative sign. As a result, the presence of the bulk corresponds to an

effective negative energy density on the brane, without violation of the

weak energy condition. The transition from a period of domination of the

matter energy density by non-relativistic brane matter to domination by the

generalized dark radiation corresponds to a crossing of the phantom divide w=-1.

**Speaker:** C.
Tsagas

**Title:** *Superadiabatic Magnetic Amplification in Conformally Flat
Universes.*

**Abstract:**

We consider the evolution of cosmological magnetic fields in FRW models

and outline a geometrical mechanism for their large-scale superadiabatic

amplification. Contrary to the widespread perception of the opposite,

this is possible within standard electromagnetic theory. We discuss the

general relativistic nature of the effect, how it modifies the adiabatic

magnetic evolution and estimate the main features of the

superadiabatically amplified residual B-field.

**Speaker:** M. Tsamparlis

**Title:** *General Relativity and Collineations.*

**Abstract:**

The symmetries in General Relativity are applied either to the

Physics or the Geometry via relations of the form L_{X}A_{ab}=B_{ab}

where A_{ab} is a metric geometric object, that is, \Gamma^a_{bc},R_{ab},\ldots.

These later symmetries are called collineations.

This talk is a general talk which explains why and how collineations

are defined, how they are interrelated in a collineation tree, what is their

effect on the kinematics and the dynamics of spacetime and finally

we describe briefly how they are applied in certain situations.

We explain the tools used in their study and show their utilization

by means of examples. The subject of collineations is an ever open

subject where one can find interesting and fundamental applications to all
branches of Physics.

**Speaker:** A. Tsokaros

**Title:** *New numerical method for binary black hole/neutron star data.*

**Abstract:**

New numerical method to construct binary black hole/neutron star initial

data is presented. The new method uses three spherical coordinate

patches; two of them are centered at the binary compact objects, and

the one at the center of mass extends to the asymptotics. Detail convergence

tests for the essential part of the code are performed for a few types of
selected

Green's functions to treat different boundary conditions. Test problems are

the calculation of gravitational potential of a fluid source, as well as the toy

model for binary black hole field.

**Speaker:** D. Tsoubelis

**Title:** *Lie point symmetry reductions of Bondi's radiating
metric.*

**Abstract:**

The Lie point symmetries of the Einstein vacuum equations

corresponding to the Bondi form of the line element are presented.

Using these symmetries, we study reductions of the field equations,

which might lead to new asymptotically flat solutions,

representing gravitational waves emitted by an isolated source.

**Speaker:** P. Wallden

**Title:** *Effective Topology through Spacetime Tomography.*

**Abstract:**

In this talk we recover the effective topology of spacetime using certain

concepts of the decoherent histories approach to Quantum Theory and

in particular the notion of records. From a series of (gedanken) experiments,

we obtain the set of possible events, grouped into sub-sets that corresponds

to histories, but with no other information such as (causal) order or any notion
of

proximity. This corresponds to tomography of the `effective' spacetime, that is

done in an operational way. Making certain assumptions about these records,

and using the existence of upper bound in the speed of transfer of matter and
information, we

recover the full partial (causal) order up to certain ambiguities that are then
classified.

The partially ordered set of events corresponds to an `effective' causal set
which

is a discretized version of spacetime with the causal relation as defining
feature.

We conclude with a derivation of the topology of this effective discretized
spacetime.

**
Speaker:** R. Woodard

During inflation the quantum effects of massless, minimally

coupled scalars and gravitons are vastly enhanced. In perturbative

loop corrections this enhancement manifests as factors of the

logarithm of the inflationary scale factor, which are known as

``infrared logarithms.'' No matter how small the coupling constant,

the continued expansion of spacetime must eventually increase the

infrared logarithms to the point that perturbation theory breaks

down. A reasonable approach for evolving past this breakdown is to

resume the series of leading infrared logarithms. Alexei Starobinskii

has developed a technique for accomplishing this for any minimally

coupled scalar with non-derivative interactions. In this talk I

generalize Starobinskii's technique to two more complicated theories

which also show infrared logarithms: scalar quantum electrodynamics

and Yukawa theory. In SQED the result is that the photon develops a

mass of order the inflationary Hubble constant, and that the scalar

evolves to a non-perturbatively large amplitude of the Hubble

constant over the electric charge. In Yukawa the result is even more

interesting: the scalar causes the fermion to develop a mass which

grows without bound, and the resulting negative vacuum energy must

eventually cancel the cosmological constant, no matter how large.

The dynamics of a D3-brane in the background of a bulk tachyon field of a

D3-brane solution of Type-0 string theory is studied. It has been shown that

these dynamics can be described by a geometrical tachyon field rolling down

its potential which is modified by a function of the bulk tachyon and

inflation occurs at weak string coupling, where the bulk tachyon condenses,

near the top of the geometrical tachyon potential. Moreover a late

accelerating phase has been found when the bulk tachyon asymptotes to zero

and the geometrical tachyon field reaches the minimum of the potential.

**Speaker:** J. Zanelli

**Title:** *Chern-Simons Forms and Transgression Actions.*

**Abstract:**

Chern-Simons (CS) gravity theories have many virtues:

- They are background-independent gauge theories;

- They give rise to second order field equations for the metric;

- Thanks to their topological pedigree, all their coupling constants are

dimensionless and fixed by gauge invariance (they don't run);

- They are scale invariant, and yet possess local (propagating) degrees

of freedom, unlike topological field theories;

They also have certain shortcomings:

- They are only defined in odd dimensions;

- These actions are not exactly gauge invariant -they change by a surface

term.

- The action and other integral charges, such as the mass, the entropy,

etc., generically diverge for asymptotically AdS geometries and
must be

regularized;

While the first problem is an inevitable feature of CS theories, the other

two can be simultaneously solved by turning the CS action into a

transgression, a form that interpolates between two characteristic

classes. The transgression action is not only a true invariant, it is also

finite.

This idea is shown to yield the right thermodynamics for asymptotically

locally AdS black holes, and has an interesting topological

interpretation.