Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Domaines hep-th
Date Vendredi 16 Avril 2021
Heure 14:00
Salle GoToMeeting
Nom de l'orateur Zhiboedov
Prenom de l'orateur Sasha
Addresse email de l'orateur
Institution de l'orateur CERN
Titre Probing gravitational EFTs with the four-graviton amplitude
Résumé We analyze constraints from perturbative unitarity and crossing on the leading contributions of higher- dimension operators to the four-graviton amplitude in four spacetime dimensions, including constraints that follow from distinct helicity configurations. We focus on the leading-order effect due to exchange by massive degrees of freedom which makes the amplitudes of interest infrared finite. In particular, we place a bound on the coefficient of the R3 operator that corrects the graviton three-point amplitude in terms of the R4 coefficient. To test the constraints we obtain nontrivial effective field-theory data by computing and taking the large-mass expansion of the one-loop minimally-coupled four-graviton amplitude with massive particles up to spin 2 circulating in the loop. Remarkably, we observe that the leading EFT coefficients obtained from both string and one-loop field-theory amplitudes lie in small islands. The shape and location of the islands can be derived from the dispersive representation for the Wilson coefficients using crossing and assuming that the lowest-spin spectral densities are the largest. Our analysis suggests that the Wilson coefficients of weakly-coupled gravitational physical theories are much more constrained than indicated by bounds arising from dispersive considerations of 2→2 scattering. The one-loop four-graviton amplitudes used to obtain the EFT data are computed using modern amplitude methods, including generalized unitarity, supersymmetric decompositions and the double copy.
Numéro de preprint arXiv 2103.12728
Commentaires Code: 418-109-349
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