Kaon-meson coupling from SU(3) flavour symmetry and application to antikaon condensed dense matter in neutron star

Abstract Observations of massive pulsars suggest that the central density of neutron stars can exceed several times the nuclear saturation density, creating a favourable environment for the appearance of exotic states, such as strange and non-strange baryons, meson condensates, and deconfined quark matter. The antikaon condensate is the most studied and plausible candidate among meson condensates. However, little is known about the exact interaction mechanisms between antikaons and mediator mesons. In this work, we investigate these interactions by employing SU(3) flavour symmetry for the first time to study antikaon condensation in dense matter. We determine hadron couplings in the mesonic sector using SU(3) flavour symmetry. We consider two scenarios involving three key parameters: the mixing angle θ v (between octet meson ω 8 and singlet meson ϕ 1 ), the octet to singlet coupling ratio z , and the symmetric-antisymmetric weight factor α v . We consider two scenarios: in the first, the mesonic sector parameter α m is varied with fixed z m , comprising the cases where the baryonic sector parameter α b = α m , 2 α m , and α m /2; in the second, z m is varied with fixed α m , comprising the cases where the baryonic sector parameter z b = z m , 2 z m , and z m /2, to independently explore their respective impacts on the system. Using this approach, we obtain the couplings of antikaons with both octet and singlet vector mesons and examine the resulting implications for dense matter. Our results show that the equation of state becomes increasingly stiffer with higher values of α v or z , delaying the onset of antikaon condensation and raising the maximum mass of neutron stars. These findings demonstrate the sensitivity of the equation of state to meson-antikaon interactions and establish SU(3) symmetry as a robust framework for constraining them.