Stellar matter with pseudoscalar condensates

TL;DR

This paper explores how gradients of pseudoscalar condensates in dense stellar matter influence photon and fermion transport, potentially affecting stellar cooling and observable astrophysical phenomena.

Contribution

It introduces a model incorporating Chern-Simons interactions and axial fields to study the effects of pseudoscalar gradients on particle properties in dense matter.

Findings

Non-trivial reflection coefficients for photons and fermions at pseudoscalar gradient boundaries.

Potential instability of fermion and boson modes due to pseudoscalar variations.

Possible impact on stellar cooling rates and observable astrophysical signatures.

Abstract

In this work we consider how the appearance of gradients of pseudoscalar condensates in dense systems may possibly influence the transport properties of photons in such a medium as well as other thermodynamic characteristics. We adopt the hypothesis that in regions where the pseudoscalar density gradient is large the properties of photons and fermions are governed by the usual lagrangian extended with a Chern-Simons interaction for photons and a constant axial field for fermions. We find that these new pieces in the lagrangian produce non-trivial reflection coefficients both for photons and fermions when entering or leaving a region where the pseudoscalar has a non-zero gradient. A varying pseudoscalar density may also lead to instability of some fermion and boson modes and modify some properties of the Fermi sea. We speculate that some of these modifications could influence the cooling rate of stellar matter (for instance in compact stars) and have other observable consequences. While quantitative results may depend on precise astrophysical details most of the consequences are quite universal and consideration should be given to this possibility.