


Chair: L. Rezzolla 
9:00 
9:30 
D.Hilditch 
Numerical Stability of a conformal decomposition of Z4
I will briefly summarize the motivation for the use of different
formulations of GR in numerical relativity. I will then present a
conformal decomposition of the Z4 formulation, Z4c, and discuss
issues relating to stability in numerical approximation. The
discussion will include a presentation of the apples with apples
tests, comparing results obtained with BSSNOK and Z4c.

9:30 
10:00 
A.Weyhausen 
Constraint damping for the Z4 formulation of general relativity
The Z4 formulation of general relativity provides a build in damping scheme
which promises to damp away constraint violations during free evolutions.
In this talk I present the results of a numerical study of the damping
system in Z4c, a conformal decomposition of Z4. I will dicuss the effect
of the damping on lowfrequency and on highamplitude perturbations
of flat spacetime as well and on the longterm dynamics of puncture and
compact star initial data in the context of spherical symmetry.

10:00 
10:30 
P. CerdáDurán 
Gravitational waves in the Fully Constrained Formulation
The Fully Constrained Formulation (FCF) of General Relativity is a novel
framework introduced as an alternative to the hyperbolic formulations
traditionally used in numerical relativity. The FCF equations form a hybrid
elliptichyperbolic system of equations including explicitly the constraints.
We present an implicitexplicit numerical algorithm to solve the hyperbolic
part, whereas the elliptic sector shares the form and properties with the well
known Conformally Flat Condition (CFC) approximation. We show the stability and
convergence properties of the numerical scheme with numerical simulations of
vacuum solutions. We have performed the first numerical evolutions of the
coupled system of hydrodynamics and Einstein equations within FCF. We apply
this formalism to extract gravitational waves from compact objects.

10:30 
11:00 

COFFE BREAK 



Chair: U. Sperhake 
11:00 
11:30 
A.Nerozzi 
A new approach to the NewmanPenrose formalism
The NewmanPenrose formalism is widely used in the areas of numerical relativity
and perturbation theory as the quantities introduced by the formalism are coordinate
independent and therefore give a gauge invariant description of the physical properties
of the spacetime under study, among which its gravitational wave content. Perturbation theory
for a rotating black hole is introduced within this formalism, through the Teukolsky equation.
However, the full set of equations introduced by the formalism is not yet fully understood,
and even the mechanism that allows the decoupling of the Teukolsky equation is not yet fully
clear. Understanding better the nature of these equations would turn out to be very helpful
in several areas, as for example attempts to obtain a higher dimensional version of the
Teukolsky equation have failed up to date. We present a new approach to the NewmanPenrose
formalism that aims to simplify considerably the whole formalism, giving a better understanding
of the known features, and suggesting procedures to extend such features to more general
scenarios of interest.

11:00 
11:30 
S.Hergt 
Canonical Treatment of Noncanonical pN Potentials for Spinning Compact Binaries
Essentially there are two different ways to derive EOMs for spinning
compact binaries in postNewtonian (pN) approximation. One method is
called the Effective Field Theory approach that aims to calculate an
effective potential for the interaction with the disadvantage to
depend on noncanonical coordinates in nonreduced phase space, i.e the
spin supplementary condition specifying the frame of reference is not
yet eliminated. A more elaborate method is to directly derive a
Hamiltonian within the ADM approach. Starting from a fourdimensional
covariant action functional the general procedure and formulae to
compare the corresponding potentials and Hamiltonians are derived,
clarifying the short notice on this procedure in arXiv:1002.2093.

12:00 
12:30 
R.Sturani 
Complete phenomenological waveforms from spinning coalescing binaries
An accurate knowledge of the coalescing binary gravitational waveform
is crucial for experimental searches as the ones performed by the LIGOVirgo
collaboration. We present the construction
of analytical phenomenological waveforms describing the signal sourced
by generically spinning binary systems.
The gap between the initial inspiral part of the waveform, described by
spinTaylor approximants, and its final ringdown part, described by damped
exponentials, is bridged by a phenomenological phase calibrated by
comparison with the dominant spherical harmonic mode of a set of waveforms
including both numerical and phenomenological waveforms of different type.
The Advanced LIGO noiseweighted overlap integral between the numerical and
phenomenological waveforms presented here ranges between 0.95 and 0.99
for a wide span of mass values.

12:30 
13:00 
S.Foffa 
The energy of a binary system at 3PN and beyond
I will show how the effective field theory methods for the gravitationally bound
twobody system proposed by Goldberger and Rothstein can be employed to efficiently
compute the conservative dynamics of a binary system.
In particular, I will show how this method successfully reproduce the
already known effective action at 3PN order, and I will sketch the steps to extend
the computation to the yetunknown 4PN order.

13:00 
14:30 

LUNCH BREAK 



Chair: S. Foffa 
14:30 
15:00 
L.Gualtieri 
Tidal interaction in compact binaries: a postNewtonian affine framework
Semianalytical approaches can be very useful in
describing compact star coalescing binaries.
In our approach, based on the postNewtonian
expansion and on the affine approximation, we
model the tidal deformation of neutron stars
in the coalescence of compact binary systems.
We apply our approach to study black holeneutron
star coalescences up to the onset of neutron star
tidal disruption, comparing our results with the
outcome of numerical relativity simulations.

15:00 
15:30 
A.Nagar 
The effective one body description of tidal effects in compact
binaries and its comparison with numerical relativity simulations
The late part of the gravitational wave signal of binary neutron star inspirals
can in principle yield crucial information on the nuclear equation of state via
its dependence on relativistic tidal parameters. In the hope of describing
analytically the late part of the gravitational wave signal, I will briefly introduce
an extension of the effectiveonebody formalism that includes the tidal interaction.
The analytical predictions are then compared/constrasted with two numerical
relativity simulations of inspiralling and coalescing neutron star binaries.
By calibrating one single flexibility parameter accounting for higherorder
tidal effects, one finds that the EOB model can reproduce, within the
numerical error, the two waveforms essentially up to merger.

15:30 
16:00 
J.Steinhoff 
The PN Approximation Beyond PointMasses
Compact objects like black holes or neutron stars can
approximately be described by point masses very well. However, very
interesting astronomical information might be contained in effects to
gravitational waves arising from the object's higher multipoles (or
their finite size). Some of these effects can be modeled by an
extension of the point mass action. Based on such an action,
contributions of dipole (i.e., spin) and quadrupole to the
postNewtonian (PN) approximation can be obtained. The potential
relevance of recent results (such as arXiv:1104.3079 and
arXiv:1002.2093) for gravitational wave astronomy is briefly discussed.

16:00 
16:30 

COFFE BREAK 



Chair: A. Nagar 
16:30 
17:00 
S.Dolan 
Selfforce calculations for black hole inspirals
Advances in numerical relativity (NR) since 2005 have led to rapid
progress in the modelling of black hole inspirals. Yet an important
frontier awaits: the large massratio regime. For example, in the
final year before merger, an Extreme MassRatio Inspiral (EMRI) will
undergo $~ 10^5$ orbits in the strongfield regime. EMRIs may be
analysed via black hole perturbation theory, by assuming the small
body follows a trajectory on the background spacetime of the large
black hole, and that the trajectory is perturbed away from a geodesic
of the background by a `selfforce'. Practical methods for computing
selfforce effects at first order in the mass ratio are now
wellestablished.
In this short review, I will focus on four emerging themes in the
selfforce programme: (i) comparison of gaugeinvariant results from
gravitational selfforce (GSF) calculations with other methodologies
(e.g. PostNewtonian, EOB and NR in arXiv:1106.3278); (ii) ongoing
development of numerical schemes for highly accurate calculations of
GSF on Kerr spacetime; (iii) aspirations to achieve accurate,
selfconsistent longterm orbital evolutions of EMRIs using GSF
calculations; (iv) understanding of new qualitatively new phenomena,
such as resonances [arXiv:1009.4923], which have practical
implications for data analysis strategies.

17:00 
17:30 
K.Takami 
A quasiradial stability criterion for rotating relativistic stars
The stability properties of relativistic stars against gravitational
collapse to black holes is a classical problem in general relativity.
In 1988, a sufficient criterion for secular instability was
established by Friedman, Ipser \& Sorkin, who proved that a sequence of
uniformly rotating barotropic stars are secularly unstable on one side
of a turning point and then argued that a stronger result should hold:
that the sequence should be stable on the opposite side, with the
turning point marking the onset of secular instability. We show here
that this expectation is not met. By computing in full general
relativity the Fmode frequency for a large number of rotating stars,
we show that the neutralstability point, that is, where the frequency
becomes zero, differs from the turning point for rotating stars. Using
numerical simulations, we validate that the new criterion can be used
to assess the dynamical stability of relativistic rotating stars.
(This work is appeared in MNRAL(2011).)

17:30 
18:00 
L.Villain 
Properties of stationary differentially rotating relativistic cold stars
Stationary configurations of differentially rotating relativistic
polytrops are studied using a multidomain pseudospectral code based
on the method developed in Jena (Ansorg, Kleinwächter, Meinel,
2003). Results concerning the solution space, the maximal masses, and
the maximal values of rotation parameters such as the ratio between
kinetic and gravitational energies will be presented and analyzed for
several cold equations of states. Implications for the emission of
gravitational waves from binary neutron star mergers will be
discussed.

20:30 
 

Social Dinner
At the "Trattoria ai Corriere" with a menu of the tipical
Parmesan food.
A vegeterian option will available on advanced request.
(web page)
[DIRECTION]
