Di-neutrons in neutron matter within a Brueckner-Hartree-Fock approach

Abstract

We investigate the appearance of di-neutron bound states in pure neutron matter within the Brueckner-Hartree-Fock approach at zero temperature. We consider the Argonne v 18 and Paris bare interactions as well as chiral two-and three-nucleon forces. Self-consistent single-particle potentials are calculated by controlling explicitly singularities in the g matrix associated with bound states. Di-neutrons are loosely bound, with binding energies below 1 MeV, but are unambiguously present for Fermi momenta below 1 fm −1 for all interactions. Within the same framework we are able to calculate and characterize di-neutron bound states, obtaining mean radii as high as ∼ 110 fm. Implications of these findings are presented and discussed.

$$^1S_0$$ 1 S 0 Pairing in Neutron Matter

“…In the calculations being reported, we have not encountered such an instability, which could be taken as evidence that medium-driven formation of dineutrons in low-density neutron matter does not occur, or, in current terminology, that a BEC-BCS crossover 58,59,60,61 does not take place. This is remarkable in view of the fact that, at low densities (k F ≈ 0.2 fm −1 ), the gap reaches 0.45 times the Fermi energy e F which is comparable to what is found in the unitary Fermi gas at the BCS-BEC crossover 62 .…”

Hyperon–nucleon interaction within chiral effective field theory revisited

“…Indeed, the difference for, e.g., U Λ (0, ρ) using U N (p N , ρ) from Ref. [25] or the parameterization utilized in Ref. [20] amounts to around 1 MeV at nuclear matter saturation density ρ = 0.17 fm −3 (k F = 1.35 fm −1 ).…”

In-medium properties of a $ \Xi$ΞN interaction derived from chiral effective field theory

“…Indeed, the difference for U Ξ (0, ρ) using U N (p N , ρ) from Ref. [36] or the parameterization utilized in Ref. [32] amounts to less than 1 MeV at nuclear matter saturation density ρ = 0.17 fm −3 (k F = 1.35 fm −1 ).…”