Résumé / Abstract Journal-club_Postdoc

Journal-club Postdoc

« Lorentz-violating gravity theories: The black hole case »

Daniele Vernieri
Postdoc -

I will talk about Horava gravity, which has been proposed as an ultraviolet completion to general relativity. Adding to the gravitational action higher-order spatial derivatives, without adding higher-order time derivatives, leads to a modification of the graviton propagator. The resulting theory is power-counting renormalizable at the expense of violating Lorentz symmetry at all scales. Perhaps surprisingly, the theory appears to be phenomenologically viable in its more general form. It is really challenging to study the consequences of Lorentz invariance breaking in the case of black holes. In fact in a Lorentz-violating gravity theory with higher-order dispersion relations, the event horizon relinquishes its role as an absolute causal boundary, since modes propagating infinitely fast will be able to penetrate it. However, this
role will be taken over by the so called “universal horizon”. Because of the causal properties of such a spacetime, no signal can escape the interior of the universal horizon propagating to the exterior, no matter how fast it moves. So, the existence of a universal horizon is a strong indication that the notion of a black hole still makes sense in Lorentz-violating gravity theories.
mardi 26 mai 2015 - 11:00
Salle des séminaires Évry Schatzman, Institut d'Astrophysique
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