Weakly Broken Galileon Symmetry

TL;DR

This paper introduces the concept of weakly broken galileon symmetry, enabling the construction of cosmological models that preserve key properties of galileon theories even in curved spacetime, with potential applications in inflation and dark energy.

Contribution

It defines weakly broken galileon invariance and demonstrates how it allows for stable, symmetry-preserving couplings to gravity, leading to new cosmological models.

Findings

Construction of models with minimal quantum corrections in curved spacetime

Development of cosmological scenarios for inflation and late-time acceleration

Identification of symmetry-preserving couplings to gravity

Abstract

Effective theories of a scalar $\phi$ invariant under the internal \textit{galileon symmetry} $\phi\to\phi+b_\mu x^\mu$ have been extensively studied due to their special theoretical and phenomenological properties. In this paper, we introduce the notion of \textit{weakly broken galileon invariance}, which characterizes the unique class of couplings of such theories to gravity that maximally retain their defining symmetry. The curved-space remnant of the galileon's quantum properties allows to construct (quasi) de Sitter backgrounds largely insensitive to loop corrections. We exploit this fact to build novel cosmological models with interesting phenomenology, relevant for both inflation and late-time acceleration of the universe.