Abstract
We consider transport properties of the hypernuclear matter in neutron star cores. In particular, we calculate the thermal conductivity, the shear viscosity, and the momentum transfer rates for npΣ−Λeμ composition of dense matter in β–equilibrium for baryon number densities in the range 0.1–1 fm−3. The calculations are based on baryon interactions treated within the framework of the non-relativistic Brueckner-Hartree-Fock theory. Bare nucleon-nucleon (NN) interactions are described by the Argonne v18 phenomenological potential supplemented with the Urbana IX three-nucleon force. Nucleon-hyperon (NY) and hyperon-hyperon (YY) interactions are based on the NSC97e and NSC97a models of the Nijmegen group. We find that the baryon contribution to transport coefficients is dominated by the neutron one as in the case of neutron star cores containing only nucleons. In particular, we find that neutrons dominate the total thermal conductivity over the whole range of densities explored and that, due to the onset of Σ− which leads to the deleptonization of the neutron star core, they dominate also the shear viscosity in the high density region, in contrast with the pure nucleonic case where the lepton contribution is always the dominant one.
Highlights
The interior composition of neutron stars (NSs)—among the most dense material objects in the Universe—is not known yet and various phases of dense matter might be expected in their interiors, see, e.g., Ref. [1], for a recent review
We find that the baryon contribution to transport coefficients is dominated by the neutron one as in the case of neutron star cores containing only nucleons
We find that neutrons dominate the total thermal conductivity over the whole range of densities explored and that, due to the onset of Σ− which leads to the deleptonization of the neutron star core, they dominate the shear viscosity in the high density region, in contrast with the pure nucleonic case where the lepton contribution is always the dominant one
Summary
The interior composition of neutron stars (NSs)—among the most dense material objects in the Universe—is not known yet and various phases of dense matter might be expected in their interiors, see, e.g., Ref. [1], for a recent review. At densities of about (2–3)n0 simple energy arguments suggest that other baryonic degrees of freedom, such as, for instance, hyperons, can appear This possibility was first proposed by Ambartsumyan and Saakyan [2] in 1960 and it has been later extensively studied in great detail by many authors using different phenomenological [3,4,5,6,7,8,9,10,11,12] or microscopical [13,14,15,16,17,18,19,20,21,22,23,24,25,26] approaches to the equation of state (EOS) of NS matter with hyperons.
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