Statut  Confirmé 
Série  IPHTHEP 
Domaines  hepph 
Date  Mardi 12 Novembre 2019 
Heure  16:00 
Institut  IPHT 
Salle  Salle Claude Itzykson, Bât. 774 
Nom de l'orateur  Alexander Monin 
Prenom de l'orateur  
Addresse email de l'orateur  
Institution de l'orateur  EPFL 
Titre  When epsilon expansion goes semiclassical 
Résumé  Even for weakly coupled theories processes with many quanta in general become nonperturbative. In the framework of the standard perturbation theory this fact is related to the factorial growth (with the number of external legs) of the number of Feynman diagrams contributing to the process. Thus, in order to study regimes with many quanta a different approach is needed. I'll present such an approach for $O(2)$ invariant $\lambda \phi^4$ theory at the WilsonFisher fixed point. Namely, using the operatorstate correspondence, valid for conformal field theories, I'll show how anomalous dimensions of operators with arbitrary charge $n$ can be computed as a power series in $\lambda$, by expanding around a nontrivial saddle. The result reproduces both $\lambda n \ll 1$ and $\lambda n \gg 1$ limits amenable to the usual perturbative analysis and the large charge expansion correspondingly. 
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