6 exposés sur les sources d'ondes gravitationnelles
salle 204 du bâtiment Evry Schatzman (bât. 18 de l'Observatoire de Meudon) :
Lundi 4 avril, 14 h :
Alexandre Le Tiec (Univ. of Maryland, USA) :
Perturbative, post-Newtonian, and general relativistic dynamics of black hole binaries
Mercredi 6 avril, 11 h :
Sebastiano Bernuzzi (Friedrich-Schiller-Univ., Jena, Allemagne)
Numerical modellization of gravitational waves from binary systems: extreme mass ratio
binaries and neutron star binaries
Jeudi 7 avril, 11 h (séminaire régulier du LUTH) :
Pau Amaro-Seoane (Max Planck Institute for Gravitational Physics, Potsdam, Allemagne) :
The connection between missing stellar cusps in galactic nuclei and general relativity
Jeudi 7 avril, 14 h :
Yuichiro Sekiguchi (National Astronomical Observatory of Japan, Tokyo) :
Simulations of numerical relativity with microphysics
Jeudi 7 avril, 15 h 30 :
Antoine Petiteau (Max Planck Institute for Gravitational Physics, Potsdam, Allemagne):
Analyzing massive black hole binaries in LISA data and using these observations for cosmology
Jeudi 7 avril, 16 h 30 :
José Luis Jaramillo (Max Planck Institute for Gravitational Physics, Potsdam, Allemagne)
A cross-correlation approach to strong-field dynamics in black hole spacetimes
Ci-dessous les résumés.
Toute personne intéressée est la bienvenue !
Bien cordialement,
Eric Gourgoulhon.
RESUMES
A. Le Tiec :
The detection and analysis of the gravitational radiation from coalescing black holes binaries
by the ground-based LIGO/VIRGO and spaced-based LISA observatories requires very accurate
theoretical predictions, used as gravitational wave templates. The relativistic dynamics
of such compact binary systems can be investigated using a variety of approximation schemes
and numerical methods within general relativity: post-Newtonian expansions,
black hole perturbation theory, numerical relativity, and the effective-one-body formalism.
We shall review the recent work at the multiple interfaces of all these analytical
and numerical methods, emphasizing the use of coordinate invariant relations
to perform meaningful comparisons. Such comparisons are crucial for several reasons:
they provide independant consistency checks of the validity of the various calculations,
they help to delineate the respective domains of validity of each method,
and ultimately to improve the modelling of black hole binaries.
S. Bernuzzi :
The numerical modellization of gravitational radiation from compact binary systems
strongly depend on the the mass ratio (e.g. comparable masses Vs large mass ratio)
and the nature of the objects (e.g. black-hole Vs neutron stars).
While the basic characteristics of the dynamics and the waveforms remain the same,
the numerical techniques required as well as the physical details may be very different.
In this talk I will present results concerning the numerical modellization
of the gravitational radiation from two different binary systems.
In the first part of the talk I will report of recent works
concerning the modellization of extreme-mass-ratio binaries.
I will describe
the "hybrid" perturbative+post-Newtonian approach developed, the results obtained
on the multipolar structure of the radiation emitted and the comparison/calibration
with the effective-one-body model.
In the second part of the talk I will report about recent progress in the simulations
of binary neutron star system with the Jena's BAM code. First I will briefly review
the methods employed in numerical relativity, then I will describe the results
obtained so far including gauge and thermal effects on the dynamics and the waves,
convergence tests and numerical difficulties.
P. Amaro-Seoane :
One of the most interesting sources of gravitational waves for the space-borne detector LISA
is the inspiral of compact objects on to a massive black hole (MBH) of mass ~ 10^5-10^7,
commonly referred to as an extreme-mass ratio inspiral (EMRI). The small object,
typically a stellar black hole, emits significant amounts of GW along each orbit
in the detector bandwidth. On the other hand, recent observations of the Galactic center
revealed a dearth of giant stars inside the inner parsec relative to the numbers
theoretically expected for a fully relaxed stellar cusp. The possibility
of unrelaxed nuclei (or, equivalently, with no or only a very shallow cusp)
adds substantial uncertainty to the EMRI estimates. I show that under quite generic
initial conditions, the time required for the growth of a relaxed,
mass segregated stellar cusp is shorter than a Hubble time
for MBHs with masses <~ 5 x 10^6 Msun, so that we can expect galaxies
in the range of LISA to have relaxed stellar cusps and, thus, EMRIs.
Y. Sekiguchi:
Recently, I developed a code in numerical relativity taking account of microphysics
such as finite temperature equations of state, weak interaction processes,
and neutrino cooling. These microphysics are important in stellar core collapse
and compact binary mergers. In this talk, I first briefly review the developed code.
Then, as applications I will talk about recent results of stellar core collapse
to a black hole and preliminary result of binary neutron star merger.
A. Petiteau:
Coalescing massive black hole binaries are the strongest and probably the most important
gravitational wave sources in the band of the future space based
observatory LISA (Laser Interferometer Space Antenna). The observation of these sources
will give a large amount of astrophysical and cosmological informations. In this seminar,
I will present how we can extract astrophysical informations from LISA data
using an analysis method based on genetic algorithms and a model of gravitational wave signal
including spin of both black holes. Then I will show an application of these observations,
using the massive black hole binaries as a standard sirens to make an independent measurement
of dark energy equation of state. This statistical method which combines LISA observations
and spectroscopic surveys of galaxies, provides an independent measurement
without using any distinctive electromagnetic counterpart.
J. L. Jaramillo :
The qualitative and quantitative understanding of near-horizon gravitational dynamics
in the strong- field regime represents a challenge both at a fundamental level
and in astrophysical applications. Recent advances in numerical relativity
and in the geometric characterization of black hole horizons open new conceptual
and technical avenues into the problem. We discuss here a research methodology
in which spacetime dynamics is probed through the cross-correlation of geometric quantities
constructed on the black hole horizon and on null infinity.
These two hypersurfaces respond to evolvinggravitational fields in the bulk,
providing canonical {\em test screens} in a {\em scattering}-like perspective
onto spacetime dynamics. More specifically, we adopt a 3+1 initial value approach
to the construction of generic spacetimes and discuss the role and properties
of dynamical trapping horizons as canonical inner {\em screens} in this context.
We apply these ideas and techniques to the study of the recoil dynamics
in post-merger binary black holes, an important issue in supermassive
galactic black hole mergers.