The effective field theory of K-mouflage

TL;DR

This paper formulates K-mouflage modified gravity models within the effective field theory of dark energy, providing a framework to reconstruct and analyze their cosmological behavior and screening mechanisms.

Contribution

It introduces a method to embed K-mouflage models into the effective field theory framework, enabling reconstruction from two functions of the scale factor and analysis of screening effects.

Findings

K-mouflage models generate only $( abla g^{00})^n$ operators at each order.

Reconstruction of models from two functions of the scale factor is possible.

Screening occurs when $K'$ is large in dense environments.

Abstract

We describe K-mouflage models of modified gravity using the effective field theory of dark energy. We show how the Lagrangian density $K$ defining the K-mouflage models appears in the effective field theory framework, at both the exact fully nonlinear level and at the quadratic order of the effective action. We find that K-mouflage scenarios only generate the operator $(\delta g^{00}_{(u)})^n$ at each order $n$. We also reverse engineer K-mouflage models by reconstructing the whole effective field theory, and the full cosmological behaviour, from two functions of the Jordan-frame scale factor in a tomographic manner. This parameterisation is directly related to the implementation of the K-mouflage screening mechanism: screening occurs when $ K'$ is large in a dense environment such as the deep matter and radiation eras. In this way, K-mouflage can be easily implemented as a calculable subclass of models described by the effective field theory of dark energy which could be probed by future surveys.