title: Holography of 3D flat cosmological horizons.
abstract: We provide a first derivation of the Bekenstein-Hawking entropy of 3D flat cosmological horizons in terms of the counting of states in a dual field theory. These horizons appear in the flat limit of nonextremal rotating Banados-Teitleboim-Zanelli black holes and are remnants of the inner horizons. They also satisfy the first law of thermodynamics. We study flat holography as a limit of AdS(3)/CFT(2) to semiclassically compute the density of states in the dual theory, which is given by a contraction of a 2D conformal field theory, exactly reproducing the bulk entropy in the limit of large charges. We comment on how the dual theory reproduces the bulk first law and how cosmological bulk excitations are matched with boundary quantum numbers.
authors.affiliation: School of Mathematics and Maxwell Institute, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
authors.forename: Arjun
authors.initials: A
authors.lastname: Bagchi
authors.affiliation: Center for the Fundamental Laws of Nature, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Detournay
authors.affiliation: School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Fareghbal
authors.affiliation: School of Mathematics and Maxwell Institute, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
authors.forename: Joan
authors.initials: J
authors.lastname: Simón