Statut  Confirmé 
Série  STRLPTENSHE 
Domaines  hepth 
Date  Vendredi 16 Avril 2021 
Heure  14:00 
Institut  DPTPHYSENS 
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 fourgraviton amplitude 
Résumé  We analyze constraints from perturbative unitarity and crossing on the leading contributions of higher dimension operators to the fourgraviton amplitude in four spacetime dimensions, including constraints that follow from distinct helicity configurations. We focus on the leadingorder 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 threepoint amplitude in terms of the R4 coefficient. To test the constraints we obtain nontrivial effective fieldtheory data by computing and taking the largemass expansion of the oneloop minimallycoupled fourgraviton 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 oneloop fieldtheory 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 lowestspin spectral densities are the largest. Our analysis suggests that the Wilson coefficients of weaklycoupled gravitational physical theories are much more constrained than indicated by bounds arising from dispersive considerations of 2→2 scattering. The oneloop fourgraviton 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  https://www.gotomeet.me/LPENSIF Code: 418109349 
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