paper

Surface Enhanced Anisotropy and Its Impacts on Massive Neutron Star Configurations in Einstein Gravity : Stability, Structure, and Multimessenger Consistency

arXiv:2611.09974 · doi:10.1016/j.aop.2026.170792

Abstract

Anisotropic neutron-star configurations are investigated within Einstein's General Relativity using a third-order polynomial equation of state, (p_r=Aρ+Bρ^2+Cρ^3), and the Buchdahl class-I metric ansatz, (e^{q(r)}=\frac{L(1+τr^2)}{L-τr^2}). Physically viable interior solutions are constructed and smoothly matched to the exterior Schwarzschild spacetime using the Darmois-Israel junction conditions. The stellar properties are examined through the matter distribution, pressure anisotropy, hydrostatic equilibrium, compactness, surface redshift, tidal deformability, causality, and dynamical stability. The energy density and radial and tangential pressures remain finite, positive, and monotonically decreasing throughout the interior, while the anisotropy vanishes at the centre and increases smoothly toward the surface. Generalized Tolman-Oppenheimer-Volkoff equation confirms equilibrium through the balance of gravitational, hydrostatic, and anisotropic forces. Furthermore, adiabatic index satisfies the Chandrasekhar stability criterion, and both sound speeds obey the causality and Herrera cracking conditions. The compactness remains below the Buchdahl limit, with physically acceptable surface redshifts. The predicted maximum masses exceed the corresponding observed masses, with some configurations extending into the lower mass-gap region. The tidal deformabilities are consistent with multimessenger constraints from GW170817 and NICER. In addition, the theoretical mass-compactness relation and its prediction intervals show good agreement with observational estimates. Finally, Bayesian Markov Chain Monte Carlo analysis provides statistically reliable constraints on the tidal Love number, compactness, and perturbation parameter. These results establish a physically viable and observationally compatible framework for describing anisotropic neutron stars within General Relativity.

arXiv comment13 figures, 35 pages, 6 tables

References in corpus (43)