Equilibration regime of the strong hyperonic reaction

Determine whether the strong reaction $2\Lambda \leftrightarrow \Xi^-+p$ is fully equilibrated on the timescale of tidal perturbations for neutron-star matter containing superconducting $\Xi^-$ hyperons, taking into account the poorly known $\Xi^-$ pairing gap.

Background

The paper considers hyperonic neutron-star matter containing neutrons, protons, leptons, $\Lambda$ hyperons, and superconducting $\Xi^-$ hyperons. The strong reaction $2\Lambda \leftrightarrow \Xi^-+p$ is normally much faster than the relevant weak nonleptonic reactions, but superconductivity can exponentially suppress its rate. For sufficiently low temperatures relative to the $\Xi^-$ critical temperature, the suppressed strong-reaction rate may become comparable to or slower than the weak rates.

Consequently, the reaction’s equilibration status depends on the uncertain $\Xi^-$ pairing gap and cannot be fixed without specifying that microphysical input. The paper adopts the equilibrated limit for definiteness, while noting that treating the reaction as frozen or equilibrated is not expected to substantially change its final results within the adopted model.