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Effects of the tensor couplings on the nucleonic direct URCA processes in neutron star matter

The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter are investigated within the relativistic Hartree-Fock approximation. We study particularly the influences of the tensor couplings of vector mesons $ω$ and $ρ$ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons $ω$ and $ρ$ can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons $ω$ and $ρ$ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non-superfluid neutron star matter. However, when considering only the tensor coupling of vector meson $ρ$, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities.That is to say that the tensor coupling of vector meson $ρ$ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.