arXiv subjects

Athira S.

Publications and source records attributed to Athira S..

3 recordsLinked to original sources

arXiv2026

Neutron star matter with hyperons: Bayesian comparison of nucleonic and SU(6)/SU(3) hyperonic models

We investigate neutron star matter with hyperons within a density-dependent relativistic mean-field framework using Bayesian inference, considering three composition scenarios: purely nucleonic matter, hyperonic matter under SU(6) flavor symmetry, and hyperonic matter under SU(3) symmetry with free vector-sector parameters. The analysis incorporates constraints from empirical nuclear matter properties, theoretical inputs at low densities, and multimessenger observations of neutron stars. We find that the SU(6) scheme, grounded in the quark model and isospin counting rule, leads to a significantly softer equation of state. In contrast, the additional flexibility of the SU(3) framework enhances vector repulsion and yields a comparatively stiffer equation of state consistent with observational bounds across the explored parameter space; in particular, the posterior distributions favor values of the vector coupling ratio $\alpha_v$ lower than the SU(6) limit $\alpha_v = 1$. These differences are reflected in neutron star observables, including mass--radius relations, tidal deformabilities, direct Urca thresholds, and oscillation properties, all of which remain compatible with current constraints within the SU(3) scenario. We further examine structural signatures through the curvature of the mass--radius relation and find that, although hyperon-rich configurations can induce noticeable variations, such features depend sensitively on the stiffness of the equation of state and are therefore not universally robust indicators. Bayesian model comparison further shows that present constraints do not meaningfully discriminate between the purely nucleonic and SU(3) hyperonic scenarios, while providing positive, but not decisive, evidence against the more restrictive SU(6) framework.

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arXiv2026

Thermal conductivity of dense $np\Lambda$ matter in neutron star cores

The possible presence of hyperons in the cores of massive neutron stars has important implications for their microscopic transport properties and thermal evolution. Despite recent progress in modelling core transport, a dedicated analysis regarding the thermal conductivity of a specific $np\Lambda$ mixture remains absent from the existing literature. In this work, we investigate the thermal conductivity of dense, $\beta $-equilibrated $np\Lambda$ matter within the framework of the variational linearized Boltzmann kinetic approach, employing the density-dependent DDME2 equation of state across a baryon density range of $(0.5\text{--}4.5)\,n_0$. We find that neutrons still dominate thermal transport, while the onset of $\Lambda $ hyperons induces only a remarkably small reduction in neutron conductivity compared to pure nucleonic matter. These results suggests that the core thermal relaxation timescale remains practically unaltered in the presence of $\Lambda$ hyperons.

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arXiv2025

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

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, for the first time, employing SU(3) flavor symmetry to study antikaon condensation in dense matter. We determine hadron couplings in the mesonic sector using SU(3) flavour symmetry. Among the three key parameters we calculate $θ_v$, the mixing angle between the octet meson $ω_8$ and the singlet meson $ϕ_1$; the ratio of the octet to singlet couplings $z$; and leave the weight factor that balances the symmetric and antisymmetric couplings $α_v$ as a free parameter to explore its impact on the system. Using this approach, we derive the couplings for antikaon interactions with both singlet and octet mesons in the nonet vector meson family and examine the corresponding implications for dense matter featuring antikaon condensation. Our findings reveal that the equation of state for dense matter becomes progressively stiffer with increasing values of $α_v$, which delays the onset of antikaon condensation and increases the maximum achievable mass of neutron stars.

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