OG51

Project title: Gravitational wave sources.
Convener: Valeria Ferrari

Sites: Ferrara Milano Bicocca Parma Roma I Torino Trieste 
International collaborations: - Departament de Fisica Aplicada, Universitat d'Alacant, Spain (Dr. J.A. Pons). - Department of Physics, Section Astrophysics, Astronomy and Mechanics, Aristotle University of Thessaloniki, Greece (Dr. A. Passamonti). - Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Potsdam, Golm, Germany (Prof. L. Rezzolla and Dr. L. Baiotti). - Institute des Hautes Etudes Scientifiques, Bures-Sur-Yvette, Paris, France (Prof. T. Damour). - Department of Astronomy and Astrophysics, University of Valencia, Burjassot, Valencia, Spain (Dr. J.A. Font). - Center for Computation and Technology and Department of Physics and Astronomy, Louisiana State University, Baton Rouge, USA (Dr. M. Tiglio). - Department of Theoretical Physics, Belarusian State University, Minsk, Bielorussia (Prof. A. Gorbatsievich). - Planetary Science Institute - Tucson AZ, USA (Dr. P. Tricarico). - UCSC, Santa Cruz, USA (Prof. P. Madau). - University of Michigan, Ann Harbor, USA (Prof. M. Volonteri).

Participants

Ferrara

Name Position INFN Position Time percentage Comments
Pierluigi Fortini Prof. Associato Incarico di Ricerca 20

Milano Bicocca

Name Position INFN Position Time percentage Comments
Francesco Haardt Prof. Associato Scientifica Universita' 100

Parma

Name Position INFN Position Time percentage Comments
Sebastiano Bernuzzi Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 100
Giovanni Corvino Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 100
Mario Casartelli Prof. Associato Scientifica Universita' 50
Roberto Depietri Ricercatore Scientifica Universita' 80

Roma I

Name Position INFN Position Time percentage Comments
Omar Benhar Noccioli Dirigente di Ricerca Tempo Indeterminato 50
Valeria Ferrari Prof. Ordinario Incarico di Ricerca 100
Leonardo Gualtieri Ricercatore Incarico di Ricerca 100
Stefania Marassi Assegnista Scientifica Dottorandi, Borse non INFN e Assegni 100
Francesco Pannarale Greco Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 100
Marco Valli Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 50

Torino

Name Position INFN Position Time percentage Comments
Mariafelicia De Laurentis Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 100
Alessandro Nagar Borsista Post doct. Scientifica Dottorandi, Borse non INFN e Assegni 80
Angelo Tartaglia Prof. Associato Scientifica Universita' 30

Trieste

Name Position INFN Position Time percentage Comments
Ernazar Abdikamalov Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 100
Enrico Barausse Dottorando Scientifica Dottorandi, Borse non INFN e Assegni 100
Konstantinos Glampedakis Borsista Post doct. Scientifica Dottorandi, Borse non INFN e Assegni 100
John Charles Miller Prof. Associato Scientifica Universita' 100
Luciano Rezzolla Dirigente di Ricerca Scientifica Enti stranieri 100

Scientific project

Our research program will be focused on studying the physics of black
holes and compact stars, as regards their role as possible sources of
gravitational waves. The different topics we plan to
investigate in the next three years are listed below node by node;
here we want stress the main problems that we are going to study, using
different and complementary approaches.

Stars emit gravitational waves at the frequencies of their oscillation
modes; these frequencies depend on the equation of state of matter in
the stellar interior, and on the evolutionary stage the star is going
through. They can be determined using perturbative methods in the
frequency domain, and a new approach to find pulsation frequencies
of rapidly rotating stars is going to be developed in Rome; in
alternative, they can be studied by integrating non linear Einstein's
equations in the time domain, and this is one of the main topics on
which research in Parma, Trieste and Torino will focus. Stellar modes
may become unstable, and may trigger a strong gravitational emission.
The onset of instabilities can be determined by perturbative
approaches (Rome), but in order to study the subsequent growth of the
mode-amplitude, full general relativistic simulations are needed
(Trieste-Parma). Detailed studies on the microphysics of neutron
stars are ongoing in Rome and in Trieste, and modern EOS will be
implemented in all numerical simulations regarding neutron star
dynamics, as well as magnetic field effects.

Binary coalescence is another process from which a large gravitational
emission is expected. The pre-merging phase is studied in Rome
integrating the equations of tidal deformation using the affine model,
while the merger phase is studied by integrating Einstein's equations
in time domain (Trieste) or using the Effective-One-Body approach
(Torino).

Numerical simulations of gravitational core collapse are performed in
Trieste, whereas the subsequent evolution of newly born neutron
stars, including finite temperature effects and neutrino processes
is also studied in Rome.

The Milano-Bicocca is a new entry in our collaboration; altough it is
composed by only one member, Francesco Haardt, the node will introduce
an interesting new field of research, i.e. the study of massive black
hole binaries, their formation, dinamics and population.

A relevant point to be stressed concerns our ongoing connection with
the Albert Einstein Institute in Potsdam where a previous member of
the SISSA staff, Luciano Rezzolla, has recently taken up a position as
head of the numerical relativity group. Since the scientific
collaborations with Rezzolla is very active and involves basically all
nodes, we will continue to benefit greatly from this connection in the
coming years, both as regards collaborations and also from
possibilities for access to facilities.

In the following the research plan of each node is briefly summarized.

ROMA
(1) We are developing a new approach to find the frequencies of the
quasi-normal modes of rotating neutron stars. This approach has
already been tested for slowly rotating stars (a paper on the subject
is in preparation) and will be suitably generalized to rapidly
rotating stars. We consider perturbations of a stationary axisymmetric
background, describing a rapidly rotating star, develop the perturbed
functions in circular harmonics and Fourier-expand time dependent
quantities; we shall determine the mode frequencies by solving partial
differential equations in 2D (the radial coordinate r and the
azimuthal angle theta), using spectral methods.

(2) The past year we have developed models (described in a paper in
preparation) of non rotating magnetized neutron stars in the framework
of general relativity, which take into account several features:
poloidal and toroidal magnetic fields, conducting or superconducting
cores, possibile presence of a magnetosphere, different equations of
state of the matter composing the star. We now plan to generalize
this model to rotating stars. Then, using these equilibrium models as
a background, we will study the oscillations of magnetized neutron
stars, using a perturbative approach. We will focus our study on
crustal oscillations, in order compare our results with the
observational data of giant flares.

(3) We are developing a unified treatment of nuclear dynamics, to be
employed to consistently obtain both the equation of state and the
transport properties of neutron star matter. We plan to use the same
formalism we employed to calculate the shear viscosity, to carry out a
systematic study of the weak response of nuclear matter. As the
calulated viscosity is significantly larger than that previously used
in the literature, we will use the new value to reassess the
instability window of r-modes.

(4) We shall compute the gravitational signals emitted by white dwarf
binaries with orbital periods of the order of 10 minutes, which fall
in the bandwidth of the space-born interferometer LISA, by taking into
account tidal deformation of the interacting stars. To this purpose,
we will integrate the equations that describe the tidal deformation,
suitably generalizing the theory developed by Carter and Luminet
(Ap. J. 121,97, 1983). We shall consider realistic models of white
dwarfs.

(5) Using estimates of pulsars magnetic field derived from
astronomical observations, and independent of spin-down measurements,
we plan to provide an upper limit for the GW-emission of known
pulsars; to this purpose, we shall assume that the observed variation
of their rotational energy is dissipated through the electromagnetic
and the gravitational channel. These estimates will improve current
upper limits derived form spin-down measurements, which assume that
all energy is dissipated in gravitational waves.

TRIESTE/SISSA

(1) The present work on phase-transition induced collapse will be
extended by using more realistic descriptions for the phase transition
and for the equation of state of the deconfined quark matter. We will
model the phase-transition surface using a level set method and
incorporate this within the CoCoNuT GR hydro code. We will also give
an improved treatment of the behaviour of matter in the outer regions
of the star.

(2) Using an AMR null-slicing general relativistic hydrodynamical
code, we will investigate the collapse and bounce of primordial
perturbations which are near to producing primordial black holes but
just fail to do so. It has been suggested that the very high
accelerations produced in this way favour growth of non-axisymmetric
modes giving significant gravitational-wave emission.

(3) We will continue our calculations to investigate the inspiral and
merger of mixed compact-object binary systems (black hole plus neutron
star). We will implement more general initial conditions and
investigate the effect of introducing a more detailed microphysical
description of the neutron-star matter.

(4) Concerning Extreme Mass Ratio Inspirals: we will study the effect
of satellite-disc encounters, focusing on accretion of disc matter
onto the satellite and on dynamical friction.

(5) We will simulate the formation of a proto-neutron star encircled
by a high-density disc, starting from initial stellar models
representing precursors of type Ic supernovae. We will investigate the
role of magnetic fields in such systems and study the disc oscillation
modes both before and after the eventual collapse of the proto-neutron
star to form a black hole.

(6) Using the magneto-hydrodynamics (MHD) formalism which we have been
developing, we will study wave propagation in superfluid and
superconducting neutron star cores, searching for possible
instabilities related with the neutron and proton vortex arrays. We
will also study global magneto-elastic oscillations in magnetars.


PARMA

(1) Rotational instability of relativistic compact stars: recent works
show that dynamical instabilities may have the effect of enhancing a
gravitational wave emission during stellar core collapse by more than
a factor of 10. The Parma unit plans to study the viability of such a
mechanism by first studying the main properties of the bar-mode
dynamical instability, extending our previous work on the subject, to
see their dependence on the rotation law assumed to describe the
differentially rotating star compactness and on the equation of state, with
particular emphasis on the use of ``realistic EOS''.

(2) We plan to study non-axisymmtric and "runaway" instability of
thick discs around compact objects and rotating black holes.

(3) We shall study the non-linear non-axisymmetric pulsation of
rotating Neutron Stars in full General Relativity in the time domain
using three dimensional simulations (in collaboration with the Rome
and Trieste units). The aim of these simulations is to extract and
analyze the fluid and gravitational modes of oscillation of neutron
stars for sequences in uniform and differential rotation. Modes will
be excited by adding some perturbation and the corresponding
frequencies will be found by a spectral analysis.

MILANO-BICOCCA

Study of the dynamics of massive black hole (MBH) binaries
in different environments; in particular of the astrophysical and
cosmological characterization of MBH binaries as gravitational wave
sources. We plan to study:

(1) the dynamics on sub-pc scales of MBH binaries in dense
circumnuclear gaseous disks: set up of the hydro codes followed by
massive parallel simulations.

(2) the effect of triaxiality on the loss-cone in stellar
backgrounds. We plan to develop a new hybrid model, exploiting 3-body
scattering experiments, to better constrain the merging time-scale of
MBH binaries.

(3) the GW signal from the MBH binary population. We plan to release
better and updated coalescence rates framing the results outlined in
points 1) and 2) in cosmological context, by means of EPS dedicated
algorithm.


TORINO

(1) We plan to continue current work on binary black hole merger and
the comparison between analytical and numerical results. In
particular, we want to move (in the Effective-One-body framework) from
the small mass limit to the comparable mass case, by comparing our
analytical-based waveforms with data coming from Numerical Relativity
simulations. This will be done in collaboration with the AEI numerical
relativity group and will also include the effect of spin. Other
semianalytical approaches will also be explored.

(2) We plan to investigate how different types of initial data may
trigger the neutron star oscillations. Our immediate goal is to study
simple non-spherical oscillations of a polytropic star and compare
perturbative and 3D evolutions, focusing in particular on
gravitational wave extraction techniques. We want to understand the
influence of the extraction techniques on a controllable, but
physically meaningful scenario (an oscillating relativistic star), by
contrasting 3D simulations with "almost exact" perturbative results.
In addition we want to evolve (in full GR) the system composed by a
relativistic star surrounded by a thick (light) disk (wich might also
collapse and plunge down if properly perturbed) aiming at
understanding the relevance of the excitation of spacetime w-modes in
such scenario.

FERRARA

Solve the equation of motion of relativistic binary system in the
field of the supermassive Black Hole in the Center of Galaxy. Study
the electromagnetic and gravitational emission of such systems in the
eikonal approximation, looking for observable effects, not predicted
in the PPN approximation.

Activity

Past year activity in the various nodes has been the following.

ROMA
- We have developed a general relativistic model for equilibrium
cofigurations of non rotating neutron stars with strong magnetic
fields. We have determined the structure of the star and of the
magnetic field, considering several possible configurations: magnetic
fields extending inside the star or confined to the crust, stars with
or without magnetosphere, different "realistic" equations of state for
the matter composing the star. We have considered various combinations
of poloidal and toroidal magnetic fields. (collaboration with J. Pons,
Alicante) A paper on this work is in preparation.

- We have studied the spectrum of stable and unstable g-modes of newly
born proto-neutron stars (PNS), in order to understand whether
unstable g-modes associated to convective motions can excite stable
oscillating g-modes through non linear coupling. The problem is of
interest because in a PNS oscillating g-modes have frequencies in the
bandwidth of VIRGO and LIGO. We have shown that nonlinear saturation
of unstable modes occurs at relatively low amplitudes, and therefore,
even if there exists a coupling between stable and unstable modes, it
does not seem to be sufficiently effective to determine a strong
gravitational emission. (collaboration with J. Pons, Alicante) A paper
on this work has been submitted to Class.Quant.Grav.

- We have computed the waveform emitted when a neutron star coalesces
onto a black hole, suitably generalizing the affine model developed by
Carter and Luminet , which allows to compute how a star is deformed by
the black hole tidal field. A paper on this work is in preparation.

- The shear viscosity of neutron matter at temperatures up to few tens
of MeV has been computed using an effective interaction obtained from
a state-of-the-art parametrization of nucleon-nucleon potential and
including the effect of three-nucleon interactions. A paper on this
subject is in preparation.

- We are developing a new approach to find the frequencies of the
quasi-normal modes (QNM) of rotating neutron stars. The past year the
basics of this approach have been set up, and tested by considering
perturbations of a slowly rotating star. We have developed the
perturbed functions in circular harmonics and Fourier-expanded time
dependent quantities. We have set up the boundary conditions
appropriate to find the quasi-normal mode (QNM) frequencies in two
dimensions (the radial coordinate r and the azimuthal angle theta),
and we have integrated the perturbed equations in 2D using spectral
methods. This allowed us to compute, for the first time, the QNM
frequencies without making restrictive assumptions, like Cowling
approximation, and without neglecting coupling among different
harmonic indexes.


TRIESTE/SISSA
- We have studied the prospects for significant gravitational
radiation being emitted in phase-transition induced collapses of
neutron-star cores (going from standard neutron-star matter to quark
matter), performing 2-D axisymmetric simulations within the
conformally-flat approximation to general relativity so as to improve
on previous Newtonian calculations. We find that the resulting
gravitational-wave spectrum is still dominated by the fundamental
quasi-radial and quadrupole oscillation modes of the star. These
oscillations produce strong shock waves in the interior which provide
the main damping mechanism for the oscillations. For the more slowly
rotating models, the development of differential rotation leads to
significant amplification of the gravitational wave emission.

- We have been making numerical calculations for the merger of mixed
compact-object binary systems consisting of a stellar-mass black hole
together with a neutron star, computing the gravitational-wave
emission produced. Initial test calculations have been made for the
idealised case of head-on collisions and the calculations are now
being extended to treat more general configurations including orbital
angular momenta and spin.

- Concerning Extreme Mass Ratio Inspirals (EMRIs): we have made
calculations for a solar mass black hole inspiralling towards a
supermassive black hole, investigating whether having a nearly
extreme-Kerr central black hole could leave a distinctive imprint on
the gravitational waveform produced, as recently suggested. We found
that a more careful examination does not reveal the suggested
behaviour. Also, we have studied EMRIs for the case of a Kerr black
hole encircled by a torus.

- We have been studying neutron-star oscillations including a detailed
treatment of the interior structure. We have developed an MHD
framework for neutron star cores composed of superfluid neutrons,
superconducting protons, and electrons, considering multifluid models
for freely precessing neutron stars, including effects such as
entrainment, interactions between proton and neutron vortices, and
magnetic coupling to the crust.

PARMA
The research activity of the Parma group has been focused on the
numerical simulation of non-axisymmetric dynamical instabilities of
relativistic-star models in full General Relativity (GR), with a
special attention to their viability as Gravitational Wave (GW)
sources. In fact, these unstable excitations of self-gravitating
bodies are rather generic phenomena, and could appear in a variety of
astrophysical scenarios, including stellar core collapse, spin up of
pulsars in binary systems, accretion-induced collapse of white dwarfs,
and mergers of two neutron stars.

The main result we obtain is that the m > 1 non axisymmetric
excitations (and in particular the m = 2 mode) are damped on a
dynamical time-scale (and so is the corresponding GW emission) by pure
nonlinear inviscid hydro-dynamical phenomena; in all simulations we
performed, the m = 1 mode, coupled with other azimuthal excitations,
always becomes the dominant one in the final stages of evolution, both
for non-corotating, high T/W, and corotating, low T/W, instabilities
(T/W is the ratio between the kinetic rotational energy (T) and the
gravitational binding energy (|W|) of the model). This phenomenology
seems to be quite general and, in parallel to our work, Newtonian
simulations of very low T/W dynamical instabilities appeared in the
literature showing a similar behavior (Ou&Tohline ApJ 2006).

Our investigation shows that the compactness of relativistic stellar
model can have a large effect on the dynamics of non-axisymmetric
deformation. Moreover, we have shown that it is possible to determine
with good accuracy the threshold of the high-T/W instability and its
dependence on compactness by means of an extrapolation technique,
through the analysis of very over-critical models only. This allows to
save large amounts of computational resources since simulations near
the threshold, that need higher resolutions and longer simulation
times, are no longer required to determine the threshold. Two papers
have been published on this work.


MILANO-BICOCCA
The research activity of the Milano-Bicocca group in the last year was
mainly focused on the study of the dynamics of massive black hole
(MBH) binaries in stellar and gaseous environment, and on the estimate
of the gravitational wave signal emitted by the cosmic population of
such systems. Selected results include:

Hardening of MBH binaries in a stellar background. We computed the
hardening of MBH binaries performing 3-body scattering Montecarlo
experiments. The scattering signal was then plugged into an hybrid
model for loss-cone depletion and orbital decay. This allowed us to
estimate the region of the mass/mass-ratio/eccentricity volume better
targeted by LISA (a paper has been published on this work).

Ejection of hypervelocity stars from the Galactic center.
Hypervelocity stars (HVSs) are a natural consequence of the presence
of a massive nuclear black hole (Sgr A*) in the Galactic Center. We
used numerical simulations of the propagation of HVSs in the Milky Way
halo to constrain three plausible ejection mechanisms: 1) the
scattering of stars bound to Sgr A* by an inspiraling
intermediate-mass black hole (IMBH); 2) the disruption of stellar
binaries in the tidal field of Sgr A*; and 3) the two-body scattering
of stars off a cluster of stellar-mass black holes orbiting Sgr A*. A
paper on this work is in press.

Dynamics of MBH binaries in circumnuclear disks. The dynamics of two
massive black holes in a rotationally supported nuclear disc of 10E8
Msun was explored using N-Body/SPH simulations. The inspiral process
is insensitive to the mass fraction in stars and gas present in the
disc and is accompanied by the circularization of the orbit. A paper
on this work is in press.

Gravitational waves from the cosmic population of SMBH binaries. We
studied, by means of dedicated simulations of black hole build-up, the
possibility of constraining different models of black hole cosmic
evolution using future gravitational wave space-borne missions, such
as LISA. We considered two main scenarios for black hole formation,
namely, one where seeds are light (~100 Msun, remnant of Population
III stars), and one where seeds are heavy (>1E4 Msun, direct
collapse). A paper has been published on this work.


TORINO
Binary black hole coalescence. Collaboration with prof. T. Damour
and the Albert Einstein Institute numerical relativity group. The
final goal has been to devise analytical and semi-analytical
techniques (based on post-Newtonian results and in particular on the
Effective-One- Body (EOB) approach to the general relativistic
two-body dynamics) for the generation of effectual and faithful
templates for the full transition inspiral-merger-ringdown of the
binary system, to be used for gravitational wave detection. Effectual
templates are defined by the property of having sufficiently large
(say >96.5%) overlaps with the expected "real signals". The main
result we have obtained has been to show that this is indeed possible
in the extreme mass ratio limit, with errors (with respect to some
"exact" waveform computed by means of Regge-Wheeler-Zerilli
perturbation theory) that are less then 4% in the modulus and less
then 1% in the phase of the wave.

In addition, it has been shown that the EOB approach (taking advantage
of results in the extreme mass ratio limit, suitably, but reasonably,
rescaled) is able to reproduce with good accuracy (in the order of 2%)
the angular momentum of the Kerr black hole resulting from the merger
of two Schwarzschild black holes (for different values of the mass
ratio) computed by means of Numerical Relativity simulations.

Neutron star oscillations. Collaboration with the Thessaloniki group
for studying the coupling between radial and non-radial oscillations
of relativistic stars by means of perturbative techniques. In
collaboration with the Parma group (Bernuzzi, Corvino, De Pietri) and
the AEI group (Baiotti, Rezzolla) we have developed a module in the
Cactus-Whisky code (Whisky_PerturbTOV), that makes initial data
compatible with the ones sometimes implemented in perturbative
studies: this will allow us (in the next future) to make extensive
comparisons between perturbative and fully relativistic evolutions in
the framework of general relativity. In particular, we have set up the
framework to study a system composed by a non-rotating relativistic
star plus a relativistic light torus. Initial data are given
consistently by the solution of the perturbative Hamiltonian and
momentum constraints.

Wave extraction techniques. In collaboration with the numerical
relativity group at Louisiana State University we have worked on the
improvement of standard wave-extraction techniques in Numerical
Relativity based on Regge-Wheeler-Zerilli perturbations of
Schwarzschild spacetimes. A general covariant formalism has been
used, due to Sarbach and Tiglio, that does not assume that the
background Schwarzschild spacetime is explicitly written in
Schwarzschild coordinates. We have shown (in particular situations and
for the odd-parity case) that systematic errors due to the
inappropriate choice of the coordinates of the background spacetime
exist and are not eliminated with the improvement of the resolution.

FERRARA
We have studied the gravitational emission of pulsars in binary
systems, deriving a general relativistic equation similar to
Papapetrou equation with the usual spin term and a new term that
describes the quadrupole moment.

Publications

2007:

1 "Gravitational waves from Extreme Mass Ratio Inspirals in non-pure Kerr spacetimes"
E. Barausse, L. Rezzolla, D. Petroff, M. Ansorg Phys. Rev. D75 (2007) 064026
2 "Post-Newtonian expansion for Gauss-Bonnet gravity"
T.P. Sotiriou, E. Barausse Phys.Rev. D75 (2007) 084007
3 "Accurate simulations of the dynamical barmode instability in full General Relativity"
L. Baiotti, R. De Pietri, G. M. Manca and L. Rezzolla Phys. Rev. D75 (2007) 044023
4 "The planar spectrum in U(N)-invariant quantum mechanics by Fock space methods:
I. The bosonic case"
R. De Pietri, S. Mori and E. Onofri J.H.E.P. 01 (2007) 018
5 "Dynamical non-axisymmetric instabilities in rotating relativistic stars"
G. M. Manca, L. Baiotti, R. De Pietri and L. Rezzolla Class. Quantum Grav. 24 (2007) S171
6 "The imprint of massive black hole formation models on the LISA data stream"
A. Sesana, M. Volonteri, F. Haardt M.N.R.A.S. 377 (2007) 1711
7 "Interaction of Massive Black Hole Binaries with Their Stellar Environment. II. Loss
Cone Depletion and Binary Orbital Decay"
A. Sesana, F. Haardt, P. Madau Ap. J. 660 (2007) 546
8 "Unresolved X-ray background: clues on galactic nuclear activity at z > 6"
R. Salvaterra, F. Haardt, M. Volonteri M.N.R.A.S. 374 (2007) 761
9 "Gravitational waves from nonlinear couplings of radial and polar nonradial modes in
relativistic stars"
A. Passamonti, N. Stergioulas and A. Nagar Phys. Rev. D75 (2007) 084038
10 "Gravitational Faraday Rotation in Binary Pulsar Systems"
M. L. Ruggiero and A. Tartaglia M.N.R.A.S. 374 (2007) 847
11 "How far away is far enough for extracting numerical
waveforms, and how much do they depend on the extraction method?"
E. Pazos, E. N. Dorband, A. Nagar, C. Palenzuela, E. Schnetter and M. Tiglio Class. Q. Grav. 24 (2007) S341
12 "Binary black hole merger in the extreme mass ratio limit"
A. Nagar, T. Damour and A. Tartaglia Class. Q. Grav. 24 (2007) S109
13 "On the accretion-induced QNM excitation of a Schwarzschild black hole"
A. Nagar, O. Zanotti, J.A. Font and L. Rezzolla Phys. Rev. D75 (2007) 044016
14 "WhiskyMHD: a new numerical code for general relativistic magnetohydrodynamics"
B. Giacomazzo, L. Rezzolla Class. Quantum Grav. 24 (2007) S235


2006:
1 "Gravitational signals due to tidal interactions between white dwarfs and black holes"
C. Casalvieri, V. Ferrari, A. Stavridis M.N.R.A.S. 365 (2006) 929
2 "A hybrid approach to black hole perturbations from extended matter sources"
V. Ferrari, L. Gualtieri, L. Rezzolla Phys. Rev. D73 (2006) 124028
3 "Coupling of radial and axial non-radial oscillations of compact
stars: gravitational waves from first-order differential rotation"
A. Passamonti, M. Bruni, L. Gualtieri, A. Nagar, C. F. Sopuerta Phys. Rev. D73 (2006) 084010
4 "Hawking emission of gravitons in higher dimensions: non-rotating black holes"
V. Cardoso, M. Cavaglia', L. Gualtieri J.H.E.P. 0602 (2006) 021
5 "Black hole particle emission in higher dimensional spacetimes"
V. Cardoso, M. Cavaglia', L. Gualtieri Phys. Rev. Lett. 96 (2006) 071301, Erratum-ibid 96 (2006) 219902
6 "Neutrino opacity in cold neutron matter"
O. Benhar, A. Fabrocini, S. Fantoni, G.I. Lykasov Phys. Atom. Nucl. 69 (2006) 1962
7 "Many-Body Theory of the Electroweak Nuclear Response"
O. Benhar Act. Phys. Pol. B37 (2006) 2243
8 "Numerical evolutions of a black hole-neutron star system in full general relativity:
Head-on collision"
F. Löffler, L. Rezzolla, M. Ansorg Phys.Rev.D74 (2006) 4018
9 "The exact solution of the Riemann problem in relativistic MHD"
B. Giacomazzo, L. Rezzolla J. Fluid Mech. (2006) 562, 223
10 "Iterated Crank-Nicolson method for hyperbolic and parabolic equations in numerical
relativity"
G. Leiler, L. Rezzolla Phys. Rev. D73 (2006) 4001
11 "Constraints on the accretion history of massive black holes from faint X-ray counts"
M. Volonteri, R. Salvaterra, F. Haardt M.N.R.A.S. 373 (2006) 121
12 "Interaction of Massive Black Hole Binaries with Their Stellar Environment. I.
Ejection of Hypervelocity Stars"
A. Sesana, F. Haardt, P. Madau Ap.J. 651 (2006) 392
13 "On the search of electromagnetic cosmological counterparts to coalescences of massive
black hole binaries"
M. Dotti, R. Salvaterra, A. Sesana, M. Colpi, F. Haardt M.N.R.A.S. 372 (2006) 869
14 "Laser Interferometer Space Antenna double black holes: dynamics in gaseous nuclear
discs"
M. Dotti, M. Colpi, F. Haardt M.N.R.A.S. 367 (2006) 103
15 "Doppler Effects from Bending of Light Rays in Curved Space-Times"
M. L. Ruggiero, A. Tartaglia and L. Iorio Int. J. Mod. Phys. D15 (2007) 1183
16 "Numerical analysis of backreaction in acoustic black holes"
R. Balbinot, A. Fabbri, S. Fagnocchi and A. Nagar Nuovo Cim. B 121 (2006) 201
17 "Gravitational waves from oscillating accretion tori"
A. Nagar AIP Conf. Proc. 861 (2006) 695
18 "A Lagrangian for the dark side of spacetime"
A. Tartaglia and M. Capone AIP Conf. Proc. 861 (2006) 1045
19 "Relativistic r-modes and shear viscosity"
L. Gualtieri, J.A. Pons, J.A. Miralles and V. Ferrari AIP Conf. Proc. 861 (2006) 638
20 "Gravitational wave sources"
V. Ferrari Proceedings of the Sixth International Symposium "Frontiers of Fundamental and Computational Physics", Udine, Italy, Springer (2006)
21 "Accurate simulations of the barmode instability in General Relativity "
R. De Pietri, L. Baiotti, G. M. Manca, and L. Rezzolla AIP Conf. Proc. 841 (2006) 416

2005:
1 Perturbative approach to the structure of rapidly rotating neutron stars"
O. Benhar, V. Ferrari, L. Gualtieri, S. Marassi Phys. Rev. D72 (2005) 044028
2 Relativistic $r$-modes and shear viscosity: regularizing the continuum spectrum"
J.A. Pons, L. Gualtieri, J.A. Miralles, V. Ferrari M.N.R.A.S. 363 (2005) 121
3 "Coupling of radial and non-radial oscillations of relativistic stars:
gauge-invariant formalism"
A. Passamonti, M. Bruni, L. Gualtieri, C. Sopuerta Phys. Rev. D71 (2005) 024022
4 "Neutron star matter equation of state and gravitational wave emission"
O. Benhar Mod. Phys. Lett. A20 (2005) 2335
5 "Dynamics of oscillating relativistic tori around Kerr black holes"
O. Zanotti, J.A. Font, L. Rezzolla, P.J. Montero M.N.R.A.S. 356 (2005) 1371
6 "The double pulsar J0737-3039: Testing the neutron star equation of state"
Ph. Podsiadlowski, J.D.M. Dewi, P. Lesaffre, J.C. Miller, W. Newton, J.R. Stone
M.N.R.A.S. 361 (2005) 1243
7 "Topical Review: Gauge-invariant non-spherical metric perturbations of Schwarzschild
black-hole spacetimes"
A. Nagar, L. Rezzolla Class. Quantum Grav. 22 (2005) R167
8 "Computations of primordial black-hole formation"
I. Musco, J.C. Miller, L. Rezzolla Class. Quantum Grav. 22 (2005) 1405
9 "Gravitational-wave emission from rotating gravitational collapse in three dimensions"
L. Baiotti, I. Hawke, L. Rezzolla, E. Schnetter Phys. Rev. Lett. 94 (2005) 1101
10 "Three-dimensional relativistic simulations of rotating neutron star collapse to a
Kerr black hole"
L. Baiotti. I. Hawke, P. Montero, F. Löffler Phys. Rev. D71 (2005) 024035
11 "Gravitational waves from oscillating accretion tori: Comparison between different
approaches"
A. Nagar, J.A. Font, O. Zanotti and R. De Pietri Phys. Rev. D72 (2005) 024007
12 "Cosmic backgrounds from miniquasars"
R. Salvaterra, F. Haardt, A. Ferrara M.N.R.A.S. 362 (2005) 50
13 "The Gravitational Wave Signal from Massive Black Hole Binaries and Its Contribution
to the LISA Data Stream"
A. Sesana, F. Haardt, P. Madau, M. Volonteri Ap. J. 623 (2005) 23
14 "A post-Keplerian parameter to test gravito-magnetic effects in binary pulsar systems"
M. L. Ruggiero and A. Tartaglia Phys. Rev. D72 (2005) 084030
15 "Post-Newtonian parameters from alternative theories of gravity"
G. Allemandi, M. Francaviglia, M. L. Ruggiero and A. Tartaglia Gen. Rel. Grav. 37 (2005) 1891
16 "On the time delay in binary systems"
A. Tartaglia, M. L. Ruggiero and A. Nagar Phys. Rev. D71 (2005) 023003
17 "Upper Limits on Gravitational-Wave Emission in Association with the 27
Dec 2004 Giant Flare of SGR1806-20"
L. Baggio, M. Bignotto, M. Bonaldi, M. Cerdonio, L. Conti, M. De Rosa, P. Falferi,
P. Fortini, M. Inguscio, N. Liguori, F. Marin, R. Mezzena, A. Mion, A. Ortolan,
G. A. Prodi, S. Poggi, F. Salemi, G. Soranzo, L. Taffarello, G. Vedovato, A. Vinante,
S. Vitale, and J. P. Zendri Phys. Rev. Lett. 95 (2005) 081103, Erratum-ibid 95 (2005) 139903
18 "On the equation of motion of the binary in the field of supermassive Black Hole"
Y .Deshko, P. Fortini, A. Gorbatsevich
Proceedins of the International Conference Bolyai-Gauss-Lobathevsky, Minsk,
Bielorussia (2006) 492
19 "Space Time Defects as a Source of Curvature and Torsion"
A. Tartaglia Int. J. Mod. Phys. A20 (2005) 2336
20 "Gravitational wave emission from matter accretion onto a Schwarzschild black hole"
A. Nagar AIP Conf. Proc. 751 (2005) 221
21 "Imprint of the equation of state of dense matter on gravitational waves
emitted by oscillating neutron stars"
V. Ferrari J. Phys. Conf. Ser. 8 (2005) 58
22 "Gravitational waves from neutron stars described by modern EOS"
O. Benhar, V. Ferrari and L. Gualtieri, AIP Conf. Proc. 751 (2005) 211
23 "Coupling of radial and non-radial oscillations of Neutron stars"
A. Passamonti, M. Bruni, L. Gualtieri and C.F. Sopuerta
Proceedings of the NATO Advanced Study Institute on the Electromagnetic
Spectrum of Neutron Stars, Marmaris, Turkey, Springer (2005)
24 "The High Density Region of QCD in a Large Mass and Chenical Potential Model"
R. De Pietri. A. Feo, E. Seiler, I.O. Stamatescu, PoS LAT2005, (2005), 170

2004:
1 "Gravitational Wave asteroseismology revisited"
O. Benhar, V. Ferrari, L. Gualtieri Phys. Rev. D70 (2004) 124015
2 "Non-adiabatic oscillations of compact stars in general relativity"
L. Gualtieri, J.A. Pons, G. Miniutti Phys. Rev. D70 (2004) 084009
3 "Nonlinear $N$--parameter spacetime perturbations: gauge transformations"
C. Sopuerta, M. Bruni, L. Gualtieri Phys.Rev. D70 (2004) 064002
4 "Gravitational waves from rotating proto--neutron stars"
V. Ferrari, L. Gualtieri, J.A. Pons, A. Stavridis Class. Quant. Grav. 21 (2004) S515
5 "Rotational effects on the oscillation frequencies of newly born proto--neutron stars"
V. Ferrari, L. Gualtieri, J.A. Pons, A. Stavridis M.N.R.A.S. 350 (2004) 763
6 "Gravitational energy loss in high--energy particle collisions:
ultrarelativistic plunge into a multidimensional black hole"
E. Berti, M. Cavagli\`a, L. Gualtieri Phys. Rev. D69 (2004) 124011
7 "Oscillations of vertically integrated relativistic tori - II. Axisymmetric modes
in a Kerr space-time"
P.J. Montero, L. Rezzolla, S'i. Yoshida M.N.R.A.S. 354 (2004) 1040
8 "Electromagnetic Fields in the Exterior of an Oscillating Relativistic Star -- I.
General Expressions and application to a rotating magnetic dipole"
L. Rezzolla, B.J. Ahmedov M.N.R.A.S. 352 (2004) 1161
9 "Hamiltonian linearization of the rest-frame instant form of tetrad gravity in a
completely fixed 3-orthogonal gauge: a radiation gauge for background-independent
gravitational waves in a post-Minkowskian Einstein spacetime"
J. Agresti, R. De Pietri, L. Lusanna and L. Martucci Gen. Rel. Grav. 36 (2004) 1055
10 "Exact and semiclassical approach to a class of singular integral operators arising
in fluid mechanics and quantum field theory"
V.A. Fateev, R. De Pietri, E. Onofri J. Phys. A37 (2004) 11379
11 "Accretion-driven gravitational radiation from non-rotating compact
objects. I: Radially infalling quadrupolar shells"
A. Nagar, G. Diaz, J.A. Pons and J.A. Font Phys. Rev. D 69 (2004) 124028
12 "Gravito-electromagnetism versus electromagnetism"
A. Tartaglia and M.L. Ruggiero Eur. J. Phys. 25 (2004) 203
13 "Fluid accretion onto relativistic stars and gravitational radiation"
A. Nagar and G. Diaz
Proceedings of 27th Spanish Relativity Meeting (ERE 2003),Alicante, Spain, Sep 2003
14 "The Gravitomagnetic measurement of the angular momentum of celestial bodies"
A Tartaglia and M.L. Ruggiero
Proceedings of 10th Marcel Grossmann Meeting, Rio de Janeiro 2003
15 "A New, Simple Model for Black Hole High Frequency QPOs"
L. Rezzolla AIP Conf. Proc. 714 (2004) 36

Talks

V. Ferrari:
1) Jun 2007 International Symposium on Exotic States of Nuclear Matter
Catania (Italy)
"What gravitational wave say about the internal structure of neutron stars"
2) Jun 2007 SISSA Highlight Colloquium
Trieste (Italy)
"Studying gravitational wave sources in preparation for Gravitational
Wave Astronomy"
3) May 2007 Workshop On Pulsars Theory and Observations
Paris (France)
"Gravitational waves from neutron stars"
4) Feb 2007 Seminar at Universita' agli studi di Napoli
Napoli (Italy)
"Alla ricerca delle onde gravitazionali"

L. Gualtieri:
1) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Unstable g-modes in proto-neutron stars"
2) Dec 2006 3rd ILIAS/N6-ENTApP Meeting
Paris (France)
"Unstable g-modes in proto-neutron stars"
3) Sep 2006 17th SIGRAV Conference on General Relativity and Gravitational Waves
Turin (Italy)
"Gravitational waves from oscillations of relativistic stars"
4) Sep 2006 Mini-workshop "Understanding Neutron Stars"
Alicante (Spain)
"Unstable g-modes in proto-neutron stars"
5) Feb 2006 3rd ILIAS Meeting
LNGS, Assergi (Italy)
"Gravitational wave asteroseismology with strange stars"

S. Marassi
1) Apr 2007 VESF Meeting
Pisa (Italy)
"A new approach to study the emission frequencies of rotating stars"
2) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"A new approach to study quasi-normal modes of rotating stars"
3) Mar 2007 Rencontres de Moriond: Gravitational waves and experimental gravity
La Thuile, Aosta (Italy)
"A new approach to study quasi-normal modes of rotating stars"
4) May 2006 Seminar at University of Southampton
Southampton (U.K.)
"Constraining the M.I.T. Bag model of quark matter with gravitational
wave observations"

E. Abdikamalov:
1) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Gravitational Waves from Phase-Transition-Induced Collapse of Neutron Stars"

E. Barausse:
1) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Extreme mass ratio inspirals in non-pure Kerr spacetimes"
2) Sep 2006 LISA Astro-GR
Golm (Germany)
"EMRIs in non-Kerr spacetimes"

K. Glampedakis:
1) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Neutron star asteroseismology via magnetar flares"

J.C. Miller:
1) Apr 2007 IOP Nuclear and Particle Physics divisional conference
Guildford (U.K.)
"Gravitational wave emission by compact objects"
2) Feb 2007 Seminar at Oxford University
Oxford (U.K.)

"Relativistic hydrodynamics"
3) Sep 2006 RAGtime 8 workshop on neutron stars and black holes
Opava (Czech Republic)
"Ideas in relativistic hydrodynamics"
4) Sep 2006 Mini-workshop "Understanding Neutron Stars"
Alicante (Spain)
"Magnetic fields in compact stars"

F. Haardt:
1) May/Jul 2007 KITP program "Physics of Galactic Nuclei" at U.C.S.B.
S. Barbara, CA (U.S.A.)
"Dynamics of binary black holes"
2) Nov 2006 EDGE science meeting
Bologna (Italy)
"Electromagnetic counterparts to LISA sources"

R. De Pietri
1) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Bar-mode instability in full GR"
2) Sep 2006 17th SIGRAV Conference on General Relativity and Gravitational Waves
Turin (Italy)
"Accurate simulations of the dynamical BAR-mode instability in General
relativity"
3) Jul 2006 11th Marcel Grossmann Meeting on General Relativity
Berlin (Germany)
"Accurate simulations of the dynamical BAR-mode instability in General
relativity"

G.M. Manca:
1) Jul 2006 New frontiers in numerical relativity
Golm (Germany)
"Dynamical bar-mode instability in General Relativity"
2) Mar 2006 Workshop on SHORT GAMMA-RAY BURSTS: Observations and Physics
Lake Tegernsee (Germany)
"Dynamical Instabilities in Rotating Neutron Stars"
3) Feb 2006 3rd ILIAS Meeting
LNGS, Assergi (Italy)
Accurate simulations of the dynamical bar-mode instability in General
Relativity"

S. Bernuzzi:
1) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Gaussian pulse excitation of compact objects' spacetime modes"

O. Benhar
1) Jun 2007 International Symposium on Exotic States of Nuclear Matter
Catania (Italy)
"Shear viscosity of neutron matter from realistic NN interactions"
2) Jun 2007 Seminar at Argonne national Laboratory
Argonne, IL (U.S.A.)
"The equation of state of neutron star matter and gravitational wave emission"
3) Apr 2007 Problemi attuali di fisica teorica
Vietri sul Mare, Salerno (Italy)
"Constraining the EOS of quark matter with gravitational wave observations"
4) Nov/Dic 2006 Lectures at S.I.S.S.A.
Trieste (Italy)
"The structure of compact stars"
5) Jul 2006 Informal meeting on the QCD phase diagram
L.N.F., Frascati (Italy)
"Deconfinement in Compact Stars: Fact or Fiction?"
6) May/Jun 2006 Lectures at "Raimondo Aini" school
Otranto (Italy)
"Compact star structure and Gravitational Wave Emission"

P. Fortini
1) Jul 2006 Conference on Astrophysics of Supermassive Black Hole
Santa Fe, New Mexico (U.S.A.)
"Gravitational Waves from binary compact systems in the field of the
Supermassive black hole in the galactic center"

Theses

DOTTORATO DI RICERCA:

1) Mar 2007 G.M. Manca
Supervisor: R. De Pietri
"Dynamical instabilities in rapidly rotating neutron star models"
Dottorato di ricerca in Fisica, Universita' di Parma

2) Jan 2007 A. Sesana
Supervisor: F. Haardt and M. Colpi
"Dynamics of massive black hole binaries in stellar environments"
Dottorato in Fisica e Astrofisica, Universita' di Milano Bicocca

3) Oct 2006 B. Giacomazzo
"General Relativistic Magnetohydrodynamics: fundamental aspects and applications"
Supervisor: L. Rezzolla
Dottorato di ricerca in Astrofisica, S.I.S.S.A.

LAUREA VECCHIO ORDINAMENTO:

1) Apr 2007 L. Sarti
"Analisi on-line in simulazioni numeriche di stelle di neutroni in relativita' generale"
Supervisor: R. De Pietri
Laurea in Fisica, Universita' di Parma

2) Mar 2007 L. Frattarolo
"Fasi della QCD a grande potenziale chimico"
Supervisor: O. Benhar
Laurea in Fisica, Universita' di Roma La Sapienza

LAUREA SPECIALISTICA:

1) Sep 2006 F. Pannarale
"Emissione gravitazionale di sistemi binari formati da un buco nero di Schwarzschild
e una stella"
Supervisor: V. Ferrari
Laurea specialistica in Fisica, Universita' di Roma La Sapienza

2) Sep 2006 A. Colaiuda
"Stelle di neutroni con campi magnetici"
Supervisor: V. Ferrari
Laurea specialistica in Astronomia e Astrofisica, Universita' di Roma La Sapienza


LAUREA TRIENNALE:

1) Apr 2007 F. Sassi
"Determinazione nuymerice dei modi quasinormali di oscillazione in elativita' genenerale"
Supervisor: R. De Pietri
Laurea in Fisica, Universita' di Parma

2) Oct 2006 A. Valli
"Equilibrio delle Stelle Compatte"
Supervisor: O. Benhar
Laurea in Fisica, Universita' di Roma La Sapienza

3) May 2007 F. Aceti
"L'equazione di Dirac e le equazioni d'onda relativistiche"
Supervisor: O. Benhar
Laurea in Fisica, Universita' di Roma La Sapienza

Other publications

1 "Quasi-normal modes and gravitational wave astronomy"
V. Ferrari, L. Gualtieri Gen. Rel. Grav., in press (2007)
2 "Lagrangian perturbation theory for rotating magnetic stars"
K. Glampedakis, N. Andersson M.N.R.A.S., in press (2007)
3 "Final spin of a coalescing black-hole binary: An effective-one-body approach"
T. Damour, A. Nagar Phys. Rev. D, in press (2007)
4 "Quark matter imprint on gravitational waves from neutron stars"
O. Benhar, V. Ferrari, L. Gualtieri, S. Marassi, Gen. Rel. Grav., in press (2007)
5 "Hypervelocity stars and the environment of Sgr A*"
A. Sesana, F. Haardt, P. Madau M.N.R.A.S. letters, in press (2007)
6 "Supermassive black hole binaries in gaseous and stellar circumnuclear discs: orbital
dynamics and gas accretion"
M Dotti, M. Colpi, F. Haardt, L. Mayer M.N.R.A.S., in press (2007)
7 "Unstable g-modes in proto-neutron stars"
V. Ferrari, L. Gualtieri, J.A. Pons submitted to Class. Quant. Grav.
8 "A new approach to the study of quasi-normal modes of rotating stars"
V. Ferrari, L. Gualtieri, S. Marassi, submitted to Phys. Rev. D
8 "Dynamics of magnetized relativistic tori oscillating around black holes"
P.J. Montero, O. Zanotti, J.A. Font and L. Rezzolla submitted to M.N.R.A.S.
9 "Faithful Effective-One-Body waveforms of small-mass-ratio coalescing black-hole
binaries"
T. Damour, A. Nagar submitted to Phys. Rev. D
10 "Circular and non-circular nearly horizon-skimming orbits in Kerr spacetimes"
E. Barausse, S.A. Hughes, L. Rezzolla submitted to Phys. Rev. D
11 "A no-go theorem for polytropic spheres in Palatini f(R) gravity"
E. Barausse, T.P. Sotiriou, J.C. Miller submitted to Phys. Rev. Lett.
12 "Modelling magnetically deformed neutron stars"
B. Haskell, L. Samuelsson, K. Glampedakis, N. Andersson submitted to M.N.R.A.S.
13 "A Model for QCD at High Density and Large Quark Mass"
R. De Pietri, A. Feo, E. Seiler, I.-O. Stamatescu submitted to Phys. Rev. D

Financial requests

Site Missioni interne Missioni estere Inviti ospiti stranieri Tot
Ferrara 2.00 2.00 4.00
Milano Bicocca 1.00 2.00 3.00 6.00
Parma 2.00 4.50 6.50
Roma I 6.00 12.00 18.00
Torino 1.00 2.00 3.00
Trieste 4.00 10.00 14.00
Totals 16.00 32.50 3.00 51.50