2026/07/22 by Prashant Thakur, Ishfaq Ahmad Rather
#astro-ph.HE #nucl-th
We study core composition \(g1\) modes of cold, nonrotating neutron stars containing antikaon condensates, hyperons, and \(Δ(1232)\) baryons and present, to our knowledge, the first calculation in full general relativity of the continuous-composition \(g1\)-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 \(n↔ p+K-\) and a strong-equilibrium limit for the \(Δ\) 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 \(Δ\) equilibration removes most of the direct \(Δ\)-induced enhancement, returning the \(NΔ\) mode toward the nucleonic band, whereas the high-frequency \(NYΔ\) branch survives through the frozen \(Λ\) gradient. Eigenfunction tracking confirms a continuous \(g1\) branch, and representative DD-ME2 calculations reproduce this hierarchy. The direct full-GR frozen-composition phase shifts satisfy \(|ΔΦg1|≤1.410×10-3\) 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.