Logarithmic corrections to entropy of 3D cosmological solutions from celestial dual

A bstract Recently a one-dimensional Schwarzian type theory was proposed as an effective dual theory of pure gravity in (2+1) dimensional asymptotically flat spacetimes [1]. This codimension-two ‘celestial’ dual captures the Bekenstein-Hawking entropy of bulk flat cosmologies in semiclassical limit. In this paper, we extend this analysis beyond semiclassical approximation and evaluate the one-loop exact partition function of this celestial dual theory. Our analysis results in novel nontrivial logarithmic corrections to the entropy of flat cosmological solutions. These log contributions appear from the one-loop path integral itself and are present in all choices of ensemble, in contrast to BTZ black holes, where the log corrections only show up in certain ensembles.