Year: 2026
Type: article
Abstract: We investigate the effects of the isovector-scalar δ meson on the density dependence of the symmetry energy within the density-dependent relativistic Hartree–Fock (DDRHF) framework. As a baseline, we generate 1006 accepted DDRHF parametrizations including the σ, ω, ρ , and π mesons by imposing empirical constraints on the saturation properties of nuclear matter. The resulting symmetry-energy slope parameters are confined to relatively large values, L ≃ 65–110 MeV. Two representative parametrizations, denoted RHF-NK1 and RHF-NK2, are randomly selected from this ensemble. Starting from these two parametrizations, we introduce the δ meson and readjust the meson–nucleon couplings under the same saturation-property constraints. The numerical optimization shows that small values of L are obtained most efficiently when the δ coupling is taken to be constant. In this case, L is reduced from approximately 73 to 32 MeV, while the binding energy per nucleon, saturation density, symmetry energy, and incompressibility coefficient remain nearly unchanged. A channel-by-channel decomposition shows that the softening is not caused by the direct δ -meson contribution alone, but by a redistribution among the δ, ρ , and π mesons together with the isoscalar Fock contributions. The resulting neutron-star mass–radius relations shift toward smaller radii, indicating that the δ meson provides an efficient additional degree of freedom for controlling the isovector properties of DDRHF models.
Source: Physics Letters B
Authors: Qirui Li, Jinniu Hu, Ying Zhang, Hong Shen
Institutions: Nankai University, Tianjin University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
Awards: G2199792964, G4906078596, G7646543586
OpenAlex ID: W7203686647