Scalar-tensor theories with pseudoscalar couplings

We consider scalar-tensor theories of gravity extended by 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 complementary 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 us to tighten bounds on Lorentz-violating backgrounds coupled to the proton spin.