# Flat Space Holography: Cosmological Entropy, Chiral Gravity and Phase Transitions

Stephane Detournay (Harvard U.)

16.01.2014 at 16:15

This talk will report on progress in defining a holographic dictionary for gravity
theories in flat space. The symmetry algebra of asymptotically flat spacetimes
at null infinity consists in the so-called BMS algebra. In 2+1 dimensions, it
plays the role of the two dimensional conformal algebra for AdS_3 gravity.
Interestingly, the corresponding phase space contains solutions that can be
interpreted as cosmological spacetimes. In particular, they possess a nontrivial
Bekenstein-Hawking entropy. We show that the latter can be reproduced
by an asymptotic counting of states in the putative dual theory, by deriving an
analog of the Cardyformula for BMS_3-invariant theories. We then describe a
limit in which the symmetry algebra reduces to a chiral copy of a Virasoro
algebra, and conjecture that the dual theory can be identied with a chiral CFT.
We finally discuss a flat-space analog of the Hawking-Page phase transition.

Arnold Sommerfeld Center

Theresienstrasse 37

Room 348/349