Statut  Confirmé 
Série  STRLPTENSHE 
Domaines  hepth 
Date  Vendredi 11 Décembre 2020 
Heure  14:00 
Institut  LPTENS 
Salle  GoToMeeting 
Nom de l'orateur  Paulos 
Prenom de l'orateur  Miguel 
Addresse email de l'orateur  
Institution de l'orateur  ENS, CNRS 
Titre  Landau diagrams in AdS and Smatrices from conformal correlators 
Résumé  Quantum field theories in AdS generate conformal correlation functions on the boundary, and in the limit where AdS is nearly flat one should be able to extract an Smatrix from such correlators. We discuss a particularly simple positionspace procedure to do so. It features a direct map from boundary positions to (onshell) momenta and thereby relates cross ratios to Mandelstam invariants. This recipe succeeds in several examples, includes the momentumconserving delta functions, and can be shown to imply the two proposals in arXiv:1607.06109 based on Mellin space and on the OPE data. Interestingly the procedure does not always work: the Landau singularities of a Feynman diagram are shown to be part of larger regions, to be called `bad regions', where the flatspace limit of the Witten diagram diverges. To capture these divergences we introduce the notion of Landau diagrams in AdS. As in flat space, these describe onshell particles propagating over large distances in a complexified space, with a form of momentum conservation holding at each bulk vertex. As an application we recover the anomalous threshold of the fourpoint triangle diagram at the boundary of a bad region. 
Numéro de preprint arXiv  2007.13745 
Commentaires  https://global.gotomeeting.com/join/261832861 
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