ISO(4,1) Symmetry in the EFT of Inflation
Abstract
In DBI inflation the cubic action is a particular linear combination of the two, otherwise independent, cubic operators \dot \pi^3 and \dot \pi (\partial_i \pi)^2. We show that in the Effective Field Theory (EFT) of inflation this is a consequence of an approximate 5D Poincar\'e symmetry, ISO(4,1), non-linearly realized by the Goldstone \pi. This symmetry uniquely fixes, at lowest order in derivatives, all correlation functions in terms of the speed of sound c_s. In the limit c_s \to 1, the ISO(4,1) symmetry reduces to the Galilean symmetry acting on \pi. On the other hand, we point out that the non-linear realization of SO(4,2), the isometry group of 5D AdS space, does not fix the cubic action in terms of c_s.
Keywords
Cite
@article{arxiv.1304.4238,
title = {ISO(4,1) Symmetry in the EFT of Inflation},
author = {Paolo Creminelli and Razieh Emami and Marko Simonović and Gabriele Trevisan},
journal= {arXiv preprint arXiv:1304.4238},
year = {2014}
}
Comments
5 pages, 2 figures. v2: minor changes, JCAP published version