Finite-nucleus-protected high-density reshaping of the DD-ME2 covariant density functional for neutron-star matter

摘要: Density-dependent covariant energy-density functionals provide a unified theoretical framework for finite nuclei and uniform neutron-star matter, but finite-nucleus data do not uniquely fix their extrapolation to supranuclear densities. We construct a finite-nucleus-protected high-density reshaping of the DD-ME2 functional, leaving the original low-density coupling functions unchanged while modifying selected high-density meson-nucleon couplings in a thermodynamically consistent way. Finite-nucleus ground-state regression tests with the DirHB solver show that binding energies, charge radii, neutron and proton rms radii, and neutron skins are preserved within numerical output precision. The neutron-star equation of state is computed separately for homogeneous Hartree RMF matter in beta equilibrium, without pairing or Bogoliubov quasiparticles. The dominant neutron-star response is generated by the isoscalar-vector $\omega$ channel: moderate high-density softening lowers the canonical radius and tidal deformability to $R_{1.4}=12.19$ km and $\Lambda_{1.4}\simeq 470$, while preserving a maximum mass $M_{\rm max}=2.35M_\odot$. The simple isovector-vector $\rho$-channel reshaping considered here produces only a weak response in the symmetry sector, proton fraction, direct-Urca threshold, and bulk stellar observables. As a proof-of-concept statistical test, we perform a two-parameter Bayesian reweighting of the protected $(f_V,f_{TV})$ grid using NICER mass-radius posteriors and an event-level GW170817 tidal likelihood. The posterior favors negative isoscalar-vector reshaping, with a marginal mode near $f_V=-0.043$, while leaving the present isovector reshaping weakly constrained.