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SUMMARY:Holography and the Celestial Sphere - Andrea Puhm\, CPHT\, Ecole P
 olytechnique
DTSTART:20221026T130000Z
DTEND:20221026T140000Z
UID:TALK184976@talks.cam.ac.uk
CONTACT:Prahar Mitra
DESCRIPTION:The holographic principle is a powerful tool in gaining insigh
 t into quantum gravity for spacetimes with a negative cosmological constan
 t\, but it is an outstanding question how generally it applies. I will rev
 iew recent advances in celestial holography which conjectures that quantum
  gravity in spacetimes with flat asymptotics (or vanishing cosmological co
 nstant) is dual to a co-dimension two conformal field theory (CFT) on the 
 celestial sphere at null infinity. Recasting the S-matrix\, which is the b
 asic observable in quantum gravity\, in a basis of boost (rather than ener
 gy) eigenstates reveals similarities with CFT correlation functions. In pa
 rticular\, universal features that arise in energetically soft and colline
 ar limits take a natural form in CFT language and spacetime (asymptotic) s
 ymmetries can be explained purely from CFT reasoning. I will highlight sev
 eral intriguing and some puzzling features that arise in this program\, an
 d discuss some avenues for developing celestial holography for non-trivial
  asymptotically flat backgrounds and for any number of dimensions.
LOCATION:Both in-person (at MR2\, DAMTP) and online (details to be sent by
  email)
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