Statut  Confirmé 
Série  RENCTHEO 
Domaines  hepth 
Date  Jeudi 7 Fevrier 2019 
Heure  11:40 
Institut  IHP 
Salle  314 
Nom de l'orateur  Puhm 
Prenom de l'orateur  Andrea 
Addresse email de l'orateur  
Institution de l'orateur  CPHT, Palaiseau 
Titre  Conformally soft photons and gravitons 
Résumé  The fourdimensional $S$matrix will be reconsidered as a correlator on the celestial sphere at null infinity. Asymptotic particle states can be characterized by the point at which they enter or exit the celestial sphere as well as their $SL(2,\mathbb C)$ Lorentz quantum numbers: namely their conformal scaling dimension and spin $h\pm \bar h$ instead of the energy and momentum. This characterization precludes the notion of a soft particle whose energy is taken to zero which plays an important role in the conventional formulation of quantum field theory scattering amplitudes. We propose that in this new formulation it should be replaced by the notion of a {\it conformally soft} particle with $h=0$ or $\bar h=0$. For photons and gravitons we explicitly construct conformally soft $SL(2,\mathbb C)$ currents with dimensions $(1,0)$ and $(2,0)$ respectively and identify them with the generators of a $U(1)$ KacMoody symmetry on the celestial sphere and celestial conformal symmetry. BMS supertranslations are generated by a spinone current whose OPE relation looks quite unusual from the celestial CFT$_2$ perspective but is equivalent to the leading soft graviton theorem and may usefully constrain celestial correlators in quantum gravity. 
Numéro de preprint arXiv  
Commentaires  
Fichiers attachés 
Pour obtenir l' affiche de ce séminaire : [ Postscript  PDF ]

[ English version ] 