SÉMINAIRE DU GRECO
"Strong Gravity in Compact Objects" 

Térence Delsate 

In this talk I will describe my recent work on the topic of compact astrophysical objects. In particular these compact objects can be used to probe the theory of gravity at a fundamental level. Neutron stars are among the best observed compact objects, and can display the strongest gravitational field right after black holes. These extreme objects are useful theoretical labs for testing not only the fundamental laws of gravity but also of nuclear matter at high density. The behaviour of nuclear matter in this regime is not well understood, which is manifest from the fact that there exists many candidate equations of state for such matter. In practice, different equations of states result in different macroscopic properties of the star, such as mass, radius, deformability, moments of inertia, ... Fortunately, it has been recently discussed in the literature that universal relations exist between some of these quantities, independently of the equation of state. I will very briefly review these relations which were formulated in the slow rotation approximation and introduce new relations in the strong rotation regime. Next, I will introduce a new method of treating perturbations of compact objects, by comparing the gravitational field of the object with that of a point particle surrounded with multi polar degrees of freedom. This is an effective description valid when looking at the compact object from far, where it appears as a point. This procedure allows to disentangle the gravitational radiation field from the matter response to tidal perturbation, and in particular defines a dynamical treatment of relativistic tides.


mardi 22 avril 2014  11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris 
