paper

Quintessence-Chameleon transitions in anisotropic Kiselev model of neutron stars

arXiv:2508.04744 · doi:10.1142/S0217751X2550112X

Abstract

We investigate a chameleon scalar field dynamically interacting with a Kiselev-type metric, where the static anisotropic fluid part of the metric is replaced by a density-dependent scalar field non-minimally coupled to curvature. This construction enables a transition from screened behavior in high-density regions-where the scalar acquires an effective mass m_ϕ\proptoρ^1/2-to unscreened quintessence dynamics at large scales, characterized by a critical screening radius r_\rm crit\propto m_ϕ^-1. By solving the modified TOV equations under spherical symmetry, we show that radial scalar gradients \partial_rϕinduce pressure anisotropies Δp\propto r^-1 in neutron star envelopes, while deviations from general relativity are suppressed deep in the core r<r_\rm crit\sim 0.03\,\mathrm{km} without destabilizing it. We further demonstrate that increasing the scalar coupling βenhances scalar energy density, which counteracts anisotropic pressure support and slightly reduces the maximum mass. The resulting (stable) configurations yield maximum mass M_max\approx 1.75\pm0.280\,M_\odot and radii R\approx11.35\pm1.11\,\mathrm{km}, consistent with conservative upper and lower bounds from multimessenger observations. Scalar contributions induce a modest suppression in the dimensionless tidal deformability Λ_\rm STΛ_\rm GR\sim0.137 at 1.4\,M_\odot i.e, 86% suppression compared to typical GR star, falling well within the LIGO/Virgo range 70\lesssimΛ_1.4\lesssim 580. These results demonstrate that environmentally screened scalar fields can dynamically generate anisotropies and modify neutron star structure without violating current astrophysical bounds. In particular, percent-level deviations in compactness and tidal response provide falsifiable signatures of short-range scalar forces, offering a novel target for next-generation GW and multimessenger surveys.

arXiv comment42 pages, 3 appendices

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