Speaker: Vincenzo Fiorentino (Padova Univ.)

After reviewing the foundational aspects of quantum field theory at finite density, the talk will focus on themodifications of axion properties in systems at finite baryonic density. Those are especially relevant for highly dense stellar environments such as supernovae and neutron stars, which are typically employed to set stringent limits on axion couplings from anomalous stellar cooling.

Specifically, we consider finite density modifications of axion couplings to nucleons within the framework of heavy baryon chiral perturbation theory and assess their consequences for astrophysical constraints on the axion parameter space.

Moreover, we analyse the effect of finite density corrections on nucleophobic axion models, i.e. ultraviolet completions of the axion effective field theory in which the axion couplings to nucleons are suppressed. These models have the advantage of evading some of the astrophysical bounds on the axion parameter space. Since these bounds are obtained from highly dense systems, we question whether the nucleophobia condition is spoiled by finite density effects