Nonlinear resolution of an infrared instability from birefringence

Investigate whether nonlinear interactions can cure the infrared instability of one polarization that arises as the wavenumber k tends to zero in the birefringent open electromagnetism dispersion relation with a nonzero helicity-splitting term, and characterize the resulting low-k behavior if stabilization occurs.

Background

Including a birefringent operator that splits the helicities modifies the dispersion relations of open electromagnetism. The authors note that, for one polarization, an IR instability appears as k→0, suggesting that linear theory may be insufficient in that regime.

They explicitly suggest that non-linearities might resolve the instability and leave its paper open.