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SUMMARY:Perturbative gravity and gauge theory at null infinity - Eduardo C
 asali (DAMTP)
DTSTART:20150423T120000Z
DTEND:20150423T130000Z
UID:TALK59130@talks.cam.ac.uk
CONTACT:Joao Miguel Vieira Gomes
DESCRIPTION:The symmetry group of the asymptotic null boundary of asymptot
 ically flat spacetimes is the infinite dimensional BMS group. It is expect
 ed that it will play an important role in any candidate holographic descri
 ption of gravity. Recently\, Strominger showed that the Ward identities fo
 r the BMS group are equivalent to Weinberg's soft graviton theorem. A simi
 lar story holds for the Ward identities of suitably defined 'large' gauge 
 transformations\, these are related to soft gluons.\n\nTo go beyond these 
 kinematical considerations I'll introduce two theories which live on the n
 ull conformal boundary of Minkowski spacetime. One of them describes gravi
 tational degrees of freedom\, and the other Yang-Mills degrees of freedom.
  Correlators on the worldsheet of these theories reproduce the tree-level 
 S-matrix for N=8 sugra and N=4 sYM respectively. These theories contain ch
 arges which implement the action of the symmetry algebra\, their Ward iden
 tities on the correlators give the soft graviton and soft gluon theorem. T
 here are also currents which implement proposed extensions of these symmet
 ry algebras\, these give the subleading contributions to the soft factors.
  
LOCATION:Potter Room (first floor\, Pav. B)
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