Scalar-tensor theories with pseudoscalar couplings

TL;DR

This paper investigates scalar-tensor theories with pseudoscalar couplings, deriving constraints from laboratory and cosmological observations, and provides new bounds on pseudoscalar-photon interactions and Lorentz-violating backgrounds.

Contribution

It introduces a comprehensive analysis of pseudoscalar couplings in scalar-tensor gravity, combining local and cosmological constraints to tighten bounds on new physics.

Findings

New bounds on pseudoscalar-photon couplings from laboratory experiments

Constraints on Lorentz-violating backgrounds coupled to proton spin

Complementary local and cosmological constraints on scalar-pseudoscalar interactions

Abstract

We consider the scalar-tensor theories of gravity extended by the pseudoscalar couplings to matter and gauge fields and derive constraints on the CP-odd combinations of scalar and pseudoscalar couplings from laboratory spin precession experiments and from the evolution of photon polarization over cosmological distances. We show the complimentary character of local and cosmological constraints, and derive novel bounds on the pseudoscalar couplings to photons from the laboratory experiments. It is also shown that the more accurate treatment of the spin content of nuclei used in the spin precession experiments allows to tighten bounds on Lorentz-violating backgrounds coupled to the proton spin.