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arXiv · 1304.4238

ISO(4,1) Symmetry in the EFT of Inflation

Paolo Creminelli·Razieh Emami·Marko Simonović·Gabriele Trevisan
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Abstract

In DBI inflation the cubic action is a particular linear combination of the two, otherwise independent, cubic operators \dot π^3 and \dot π(\partial_i π)^2. We show that in the Effective Field Theory (EFT) of inflation this is a consequence of an approximate 5D Poincaré symmetry, ISO(4,1), non-linearly realized by the Goldstone π. 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 π. 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.

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Paolo Creminelli, Razieh Emami, Marko Simonović, Gabriele Trevisan. 2014-02-27. ISO(4,1) Symmetry in the EFT of Inflation. https://doi.org/10.1088/1475-7516%2F2013%2F07%2F037

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