# Effective field theory for gravitational radiation in scalar-tensor gravity

## TL;DR

This paper extends the effective field theory framework to scalar-tensor gravity, analyzing gravitational wave signals from binary systems and exploring violations of the strong equivalence principle due to scalar fields.

## Contribution

It introduces a novel EFT approach for scalar-tensor theories, including conformal and disformal couplings, and compares results with existing post-Newtonian methods.

## Key findings

- EFT formalism reproduces known post-Newtonian results
- Violations of the strong equivalence principle can occur in scalar-tensor models
- Disformal couplings have significant implications for gravitational wave signals

## Abstract

A light scalar degree of freedom, as the one possibly responsible for the accelerated expansion of the Universe, could leave observable traces in the inspiral gravitational wave signal of binary systems. In order to study these effects, we extend the effective field theory formalism of Goldberger and Rothstein to minimal scalar-tensor theories of gravity. This class of models is still very broad, because the couplings of the scalar to matter are far less constrained than those a massless spin-2 field. In most of the paper we focus on conformal couplings. Using the effective field theory approach, we discuss the emergence of violations of the strong equivalence principle even in models that exhibit universality of free fall at the microscopic level. Our results on the conservative dynamics of the binary and its power emitted in gravitational and scalar radiation agree with those obtained with the standard post-Newtonian formalism. We also compare them to more recent work. Finally, we discuss the implications of considering a disformal coupling to matter.