String Theory Journal Club

Celestial holography is the idea that the holographic dual theory for an asymptotically flat spacetime is codimension 2 CFT living in the celestial sphere at null infinity. Originally proposed in 4 dimensions, this idea is non-trivial to extend in lower dimensional gravitational theories due to absence of propagating gravitons. In this talk, we will show the construction of a one-dimensional dual theory that effectively describes the phase space of (2+1) dimensional gravity near a Flat Space Cosmology saddle. This Schwarzian type dual theory, living on the celestial circle, describes the dynamics of (pseudo)-Goldstone modes associated with the asymptotic symmetries of flat space. We also compute the Bekenstein-Hawking entropy of Flat Space Cosmological solutions and find agreement with gravitational calculations.