Non-universal scalar-tensor theories and big bang nucleosynthesis

TL;DR

This paper examines how big-bang nucleosynthesis constrains scalar-tensor theories of gravity, especially those violating the equivalence principle, and finds it provides tighter limits than Solar system tests.

Contribution

It analyzes constraints on extended quintessence and scalar-tensor models with equivalence principle violations, highlighting the phase space where general relativity is an attractor.

Findings

Big-bang nucleosynthesis imposes stronger constraints than Solar system tests.

Certain scalar-tensor theories with quadratic couplings are ruled out by nucleosynthesis.

The phase space analysis identifies theories that naturally evolve toward general relativity.

Abstract

We investigate the constraints that can be set from big-bang nucleosynthesis on two classes of models: extended quintessence and scalar-tensor theories of gravity in which the equivalence principle between standard matter and dark matter is violated. In the latter case, and for a massless dilaton with quadratic couplings, the phase space of theories is investigated. We delineate those theories where attraction toward general relativity occurs. It is shown that big-bang nucleosynthesis sets more stringent constraints than those obtained from Solar system tests.