MG12 - Talk detail
 

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Abstract

From massive gravity to k-Mouflage

We introduce a large class of scalar-tensor theories where gravity becomes stronger at large distances via the exchange of a scalar that mixes with the graviton. At small distances, i.e. large curvature, the scalar is screened via an analog of the Vainshtein mechanism of massive gravity. The crossover distance between the two regimes can be made cosmological by an appropriate choice of the parameters.

Relativistic stars in f(R) gravity

We study the strong gravity regime in viable models of so-called f(R) gravity that account for the observed cosmic acceleration. In contrast with recent works suggesting that very relativistic stars might not exist in these models, we find numerical solutions corresponding to static star configurations with a strong gravitational field. The choice of the equation of state for the star is crucial for the existence of solutions. Indeed, if the pressure exceeds three times the energy density in a large part of the star, static configurations do not exist. In our analysis, we use a polytropic equation of state, which is not plagued with this problem and, moreover, provides a better approximation for a realistic neutron star.

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