DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios

TL;DR

This paper demonstrates that the pseudo-conformal universe scenario can be realized within DBI-like theories, linking conformal symmetry breaking and scale-invariant perturbations to geometric features in an AdS bulk, offering a novel theoretical framework.

Contribution

It shows how the pseudo-conformal universe can be embedded in DBI inflation models, connecting conformal symmetry breaking to geometric directions in AdS space.

Findings

Pseudo-conformal scenario realizable in DBI theories.

Scale invariance protected by shift symmetry.

Geometric flat directions correspond to scale-invariant fields.

Abstract

The pseudo-conformal universe is an alternative to inflation in which the early universe is described by a conformal field theory on approximately flat space-time. The fields develop time-dependent expectation values, spontaneously breaking the conformal symmetries to a de Sitter subalgebra, and fields of conformal weight zero acquire a scale invariant spectrum of perturbations. In this paper, we show that the pseudo-conformal scenario can be naturally realized within theories that would ordinarily be of interest for DBI inflation, such as the world-volume theory of a probe brane in an AdS bulk space-time. In this approach, the weight zero spectator field can be associated with a geometric flat direction in the bulk, and its scale invariance is protected by a shift symmetry.