Statut  Confirmé 
Série  RENCTHEO 
Domaines  hepth 
Date  Jeudi 10 Novembre 2022 
Heure  10:00 
Institut  LPTHE 
Salle  Institut Henri Poincaré, Room 314 
Nom de l'orateur  Mason 
Prenom de l'orateur  Lionel 
Addresse email de l'orateur  
Institution de l'orateur  Oxford 
Titre  Twistors and Lw_{1+infinity} symmetries in celestial formulations of 4d gravity 
Résumé  Recently in their celestial holography programme, Strominger and coworkers uncovered a hidden loop algebra version of winfinity symmetry in the `celestial soft OPEs' for graviton scattering. This talk will explain the origin of this symmetry in terms of old ideas of Newman and Penrose based on lightcone cuts of null infinity and their description in terms of asymptotic twistors. W_n symmetries were introduced by Zamolodchikov as higher spin symmetries in 2d conformal field theories. These were given a geometric interpretation as for n=infinity as areapreserving diffeomorphisms of the plane. I will explain how the corresponding classical loop algebra becomes a hidden symmetry of selfdual gravity realized geometrically as the structurepreserving diffeomorphisms of Penrose's nonlinear graviton construction. This can be realized particularly cleanly by recasting the constructions in split signature. We introduce an open chiral sigma model with target the asymptotic twistor space. The full gravity treelevel Smatrix can then be obtained from tree correlators of this model. The action of the Lw_{1+\infty} symmetry on the treelevel Smatrix of full gravity beyond the selfdual sector is then realized by the action of certain vertex operators and act on the full amplitude. This is based on joint work with Tim Adamo and Atul Sharma https://arxiv.org/abs/2110.06066 and https://arxiv.org/abs/2103.16984 together with some more recent work. 
Numéro de preprint arXiv  2110.06066 
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