Neutron matter at low density and the unitary limit

Abstract

Neutron matter at low density is studied within the hole-line expansion. Calculations are performed in the range of Fermi momentum $k_F$ between 0.4 and 0.8 fm${}^{-1}$. It is found that the Equation of State is determined by the ${}^1{S}_0$ channel only, the three-body forces contribution is quite small, the effect of the single particle potential is negligible and the three hole-line contribution is below 5% of the total energy and indeed vanishing small at the lowest densities. Despite the unitary limit is actually never reached, the total energy stays very close to one half of the free gas value throughout the considered density range. A rank one separable representation of the bare NN interaction, which reproduces the physical scattering length and effective range, gives results almost indistinguishable from the full Brueckner G-matrix calculations with a realistic force. The extension of the calculations below $k_F=0.4$ fm${}^{-1}$ does not indicate any pathological behavior of the neutron Equation of State.

17 pages, 7 figures. To be published in Phys. Rev. C

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• Microscopic Study of ${}^1{S}_0$ Superfluidity in Dilute Neutron Matter
• Phase separation in low-density neutron matter
• Quantum Monte Carlo study of dilute neutron matter at finite temperatures
• Magnetised neutron star crust within effective relativistic mean-field model
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• Quantum Monte Carlo method applied to strongly correlated dilute fermi gases with finite effective range