JT gravity from holographic reduction of 3D asymptotically flat spacetime

We attempt to understand the CFT1 structure underlying (2+1)D gravity in flat spacetime via dimensional reduction. We observe that under superrotation, the hyperbolic (and dS(2)) slices of flat spacetime transform to asymptotically (A)dS(2) slices. We consider a wedge region bounded by two such surfaces as End-of-the-World branes and employ Wedge holography to perform holographic reduction. We show that once we consider fluctuating branes, the localised theory on the branes is Jackiw-Teitelboim (JT) theory. Finally, using the dual description of JT, we derive an 1D Schwarzian theory at the spatial slice of null infinity. In this dual Celestial (nearly) CFT, the superrotation mode of 3D plays the role of the Schwarzian derivative of the boundary time reparametrization mode.

Automated summary

In this paper, the authors aim to understand the CFT1 structure of (2+1)D gravity in flat spacetime through dimensional reduction. They find that under superrotation, the hyperbolic (and dS(2)) slices of flat spacetime transform to asymptotically (A)dS(2) slices. By considering a wedge region bounded by two such surfaces as End-of-the-World branes, they use Wedge holography to perform holographic reduction and show that the localized theory on the branes is Jackiw-Teitelboim (JT) theory. Finally, they derive a 1D Schwarzian theory at the spatial slice of null infinity using the dual description of JT.