Theoretical Physics Seminar: Andrea Puhm

  • Date: –15:15
  • Location:
  • Lecturer: Andrea Puhm
  • Organiser: Vladimir Procházka
  • Contact person: Vladimir Procházka
  • Seminarium

Asymptotic symmetries and celestial CFT

The realization that soft theorems in gauge theory and gravity are
 manifestations of Ward identities for asymptotic symmetries has
 reinvigorated recent attempts at flat space holography. One of the
 key milestones from applying this paradigm is that it solidifies a
 conjectured extension of the BMS group to include superrotations,
 based on a newly discovered subleading soft graviton theorem. This
 precipitated two parallel initiatives within the field. On the one
 hand, the subleading soft graviton mode is a natural stress tensor
 candidate for a putative dual celestial CFT with a Virasoro symmetry,
 which provoked reexamining scattering amplitudes in a basis that makes
 conformal covariance manifest. On the other hand, the correspondence
 between the subleading soft graviton theorem and the proposed
 asymptotic Virasoro superrotation symmetry does not appear to be
 bijective and an extension to arbitray diffeomorphisms on the
 celestial sphere was suggested. In this talk I will provide a unified
 treatment of conformally soft Goldstone modes of spontaneously broken
 asymptotic symmetries which will land us at the crossroads of the two
 ongoing debates about what the appropriate conformal basis for
 celestial CFT is and what the asymptotic symmetry group of Einstein
 gravity at null infinity should be.