Reaction-constrained composition \(g\)-modes in neutron stars with antikaon condensates, hyperons, and \(\Delta(1232)\) resonances

Abstract

We study core composition \(g_1\) modes of cold, nonrotating neutron stars containing antikaon condensates, hyperons, and \(\Delta(1232)\) baryons and present, to our knowledge, the first calculation in full general relativity of the continuous-composition \(g_1\)-mode frequency and gravitational-wave damping time for stars with a \(K^-\) condensate. Using the BigApple relativistic mean-field equation of state, we compute frequencies, damping times, and frozen-composition tidal overlaps, and identify the buoyancy channels with a species-resolved Ledoux decomposition validated by mode-frequency sensitivities. We compare fully frozen matter with a fast-\(K\) limit for \(n\leftrightarrow p+K^-\) and a strong-equilibrium limit for the \(\Delta\) quartet. Fast-\(K\) equilibration retains \(36\%\)--\(44\%\) of the peak local kaon buoyancy and \(65.7\%\)--\(73.4\%\) of the frozen terminal-configuration frequencies, while increasing the damping times by factors of \(14.4\)--\(31.8\); the mode remains above the nucleonic band. Strong \(\Delta\) equilibration removes most of the direct \(\Delta\)-induced enhancement, returning the \(N\Delta\) mode toward the nucleonic band, whereas the high-frequency \(NY\Delta\) branch survives through the frozen \(\Lambda\) gradient. Eigenfunction tracking confirms a continuous \(g_1\) branch, and representative DD-ME2 calculations reproduce this hierarchy. The direct full-GR frozen-composition phase shifts satisfy \(|\Delta\Phi_{g_1}|\leq1.410\times10^{-3}\) rad, a factor of 21 below the \(0.03\)-rad favorable-event scale for the Einstein Telescope. An exotic species therefore produces a distinct composition mode only if its composition gradient, or a coupled slowly equilibrating gradient, survives over the oscillation period.

Comments: 20 pages, 9 figures, 8 tables