Room 327

Logarithmic CFT structure on the celestial sphere

Subramanya Hegde

IMSc

Flat space scattering amplitudes, under Melin transform and a
suitable change of variables manifest the SL(2,C) symmetry on the celestial
sphere. This has led to an area of work where these celestial "correlators"
are investigated for a conformal field theory (CFT) like structure, by
including super-rotations on the celestial sphere. From double soft limits
for tree level flat space amplitudes, it can be shown that the central
charge of this description vanishes. In traditional CFT literature, when
the central charge vanishes a new anomaly maybe present when the stress
tensor admits a logarithmic partner. Recently, authors of the below paper
have claimed that they find such a logarithmic partner for the celestial
stress tensor. They prescribe a limiting procedure where, as the IR cut-off
for gravity is taken to zero, the celestial stress tensor and its log
partner have two point correlators appropriate for log CFTs.