MG12 - Talk detail
 

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Abstract

R^4 terms and d=4 supergravity

We show there are two independent combinations of R^4 present, at one loop, in the type IIA and heterotic d=4 effective action, which contradicts the common belief that there is only one R^4 term in d=4 supergravity. In pure N=1 supergravity this new R^4 combination cannot be directly supersymmetrized, but we show that, when coupled to a scalar chiral multiplet, it emerges in the action on-shell. We then move to the N=8 supersymmetrization of this term and show that it cannot be achieved at the linearized level. This is in conflict with the theory one gets after toroidal compactification of type II superstrings being N=8 supersymmetric. We interpret this result in face of the recent claim that perturbative supergravity cannot be decoupled from string theory in d>4, and N=8, $d=4$ supergravity is in the swampland.

Perturbations of dilatonic black holes in heterotic string theory: stability and scattering

We obtain the spherically symmetric black hole solutions with dilatoniccharge in heterotic string theory with curvature-squared corrections inarbitrary d spacetime dimensions (previously this result was only knownfor d=4). We compute the tensorial perturbations to this metric andtheir respective potential, from which we study their stability. Wethen derive the absorption cross section for low-frequency tensor typegravitational waves. We compare these with our previous results for nondilatonic string-corrected black holes.

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