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 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.

5 pages, 2 figures. v2: minor changes, JCAP published version

References in corpus (6)

• The Effective Field Theory of Inflation
• Galileon inflation
• DBI and the Galileon reunited
• Primordial fluctuations and non-Gaussianities in multi-field DBI inflation
• DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios
• Primordial fluctuations and non-Gaussianities from multifield DBI Galileon inflation

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• Symmetric Superfluids
• The Cosmological Phonon: Symmetries and Amplitudes on Sub-Horizon Scales
• Symmetric Scalars
• K-nonizing