Talk detail

Participant	Deffayet, Cédric
Institution	CNRS (IAP and IHÉS) - 98 bis Bd Arago - Paris - - France

Session	AT4	Accepted	Yes	Order	3	Time	15:00	15'
Talk	Oral abstract	Title	Consistent massive graviton on arbitrary backgrounds
Coauthors	Bernard, Laura; von Strauss, Mikael.
Abstract	We obtain the fully covariant linearized field equations for the metric perturbation in the de Rham- Gabadadze-Tolley (dRGT) ghost free massive gravities. For a subset of these theories, we show that the nondynamical metric that appears in the dRGT setup can be completely eliminated leading to the theory of a massive graviton moving in a single metric. This has a mass term which contains nontrivial contributions of the space-time curvature. We show further how five covariant constraints can be obtained including one which leads to the tracelessness of the graviton on flat space-time and removes the Boulware-Deser ghost. The five constraints are obtained for a background metric which is arbitrary, i.e. which does not have to obey the background field equations.
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Session	AT2	Accepted	Yes	Order	1	Time	14:35	25'
Talk	Oral abstract	Title	Counting the degrees of freedom of generalized Galileons
Coauthors	Gilles Esposito-Farese, Daniele A. Steer
Abstract	We consider Galileon models on curved spacetime, as well as the counterterms introduced to maintain the second-order nature of the field equations of these models when both the metric and the scalar are made dynamical. Working in a gauge invariant framework, we first show how all the third-order time derivatives appearing in the field equations -- both metric and scalar -- of a Galileon model or one defined by a given counterterm can be eliminated to leave field equations which contain at most second-order time derivatives of the metric and of the scalar. The same is shown to hold for arbitrary linear combinations of such models, as well as their k-essence-like/Horndeski generalizations. This supports the claim that the number of degrees of freedom in these models is only 3, counting 2 for the graviton and 1 for the scalar. We comment on the arguments given previously in support of this claim. We then prove that this number of degrees of freedom is strictly less that 4 in one particular such model by carrying out a full-fledged Hamiltonian analysis. In contrast to previous results, our analyses do not assume any particular gauge choice of restricted applicability.
Pdf file