Spin Susceptibility of Neutron Matter at Zero Temperature

Fantoni, S.; Sarsa, A.; Schmidt, Kevin

doi:10.1103/physrevlett.87.181101

Cited by 133 publications

(205 citation statements)

References 18 publications

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“…For this reason even relatively simple estimates [36] of E P N M σ are not too different from the current state of the art [35]. In contrast, in SNM the large negative v CB cancels the T F G to produce a relatively small binding energy.…”

Section: Correlated Basis Interactionmentioning

confidence: 95%

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Quenching of weak interactions in nucleon matter

Cowell

Pandharipande

2003

Phys. Rev. C

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We have calculated the one-body Fermi and Gamow-Teller charge-current, and vector and axialvector neutral-current nuclear matrix elements in nucleon matter at densities of 0.08, 0.16 and 0.24 fm −3 and proton fractions ranging from 0.2 to 0.5. The correlated states for nucleon matter are obtained by operating on Fermi-gas states by a symmetrized product of pair correlation operators determined from variational calculations with the Argonne v18 and Urbana IX two-and threenucleon interactions. The squares of the charge current matrix elements are found to be quenched by 20 to 25 % by the short-range correlations in nucleon matter. Most of the quenching is due to spin-isospin correlations induced by the pion exchange interactions which change the isospins and spins of the nucleons. A large part of it can be related to the probability for a spin up proton quasi-particle to be a bare spin up/down proton/neutron. Within the interval considered the charge current matrix elements do not have significant dependence on the matter density, proton fraction and magnitudes of nucleon momenta; however, they do depend upon momentum transfer.The neutral current matrix elements have a significant dependence on the proton fraction. We also calculate the matrix elements of the nuclear Hamiltonian in the same correlated basis. These provide relatively mild effective interactions which give the variational energies in the HartreeFock approximation. The calculated two-nucleon effective interaction describes the spin-isospin susceptibilities of nuclear and neutron matter fairly accurately. However ≥ 3-body terms are necessary to reproduce the compressibility. Realistic calculations of weak interaction rates in nucleon matter can presumably be carried out using the effective operators and interactions studied here. All presented results use the simple 2-body cluster approximation to calculate the correlated basis matrix elements. This allows for a clear discussion of the physical effects in the effective operators and interactions.

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Section: Correlated Basis Interactionmentioning

confidence: 95%

“…16 along with those obtained from quantum Monte Carlo calculations [35] with the static part of Argonne v18 and Urbana-IX interactions. The two-body v CB using F ij of SNM gives fairly accurate values of E P N M σ .…”

Section: Correlated Basis Interactionmentioning

confidence: 99%

Quenching of weak interactions in nucleon matter

Cowell

Pandharipande

2003

Phys. Rev. C

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“…For n = n 2 we can check and have checked explicitly that this is the case. Finally, we find δµ at x c2 is given by δµ c2 /E F = 0.16 (2) where E F = (k 2 F /2m). Comparing with ∆ SF 2 /E F ∼ 0.23 obtained from Ref.…”

Section: Phase Competitionmentioning

confidence: 99%

“…The energetically favored phase depends on the masses and relative populations of the species, the interaction strength, and whether the interactions are long ranged. Polarized gases can exist in a variety of physical systems, including ultracold trapped atomic Fermi gases [1], in dense hadronic phases near the cores of neutron stars [2][3][4], and possibly in quark matter [5].…”

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confidence: 99%

Phase separation in low-density neutron matter

Gezerlis

Sharma

2012

Phys. Rev. C

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Low-density neutron matter has been studied extensively for many decades, with a view to better understanding the properties of neutron-star crusts and neutron-rich nuclei. Neutron matter is beyond experimental control, but in the past decade it has become possible to create a system of fermionic ultracold atomic gases in a regime close to low-density neutron matter. In both these systems pairing is significant, making simple perturbative approaches impossible to apply and necessitating ab initio microscopic simulations. Atomic experiments have also probed polarized matter. In this work, we study population-imbalanced neutron matter (possibly relevant to magnetars and to density functionals of nuclei) arriving at the lowest-energy configuration to date. For small to intermediate relative fractions the system turns out to be fully normal, while beyond a critical polarization we find phase coexistence between a partially polarized normal neutron gas and a balanced superfluid gas. As in cold atoms, a homogeneous polarized superfluid is close to stability but not stable with respect to phase separation. We also study the dependence of the critical polarization on the density.

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“…with b is different for each effective force at a given density. We can compare our results to the ratio of spin susceptibility of interacting neutron matter to the non interacting Fermi gas obtained by Fantoni, Sarsa and Schmidt [14] by means of the auxiliary field diffusion Monte Carlo method. This ratio is proportional to the polarizability as obtained in expression (1) and therefore inversely proportional to the spin symmetry coefficient A 1,0 .…”

Section: A Results For Skyrme Interactionsmentioning

confidence: 99%

Symmetry energy coefficients for asymmetric nuclear matter

Braghin¹

2003

Braz. J. Phys.

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Symmetry energy coefficients of asymmetric nuclear matter generalized are investigated as the inverse of nuclear matter polarizabilities with two different approaches. Firstly a general calculation shows they may depend on the neutron-proton asymmetry itself. The choice of particular prescriptions for the density fluctuations lead to certain isospin (n-p asymmetry) dependences of the polarizabilities. Secondly, with Skyrme type interactions, the static limit of the dynamical polarizability is investigated corresponding to the inverse symmetry energy coefficient which assumes different values at different asymmetries (and densities and temperatures). The symmetry energy coefficient (in the isovector channel) is found to increase as n-p asymmetries increase. The spin symmetry energy coefficient is also briefly investigated. I IntroductionThe (n-p) symmetry energy coefficient and its dependence on the nuclear density has been extensively studied and this is of relevance, for example, for the description of macroscopic nuclear properties as well as for proto-neutron and neutron stars. It represents the tendency of nuclear forces to have greater binding energies (E/A) for symmetric systems -equal number of protons and neutrons. It contributes as a coefficient for the squared neutron-proton asymmetry in usual macroscopic mass formula,, where H 0 does not depend on the asymmetry, Z, N and A are the proton, neutron and mass numbers respectively. Other powers of the asymmetry (proportional to (N − Z) n for n = 2 [1]) are usually expected to be less relevant for the equation of state (EOS) of nuclear matter based on such parameterizations [2,3]. The same kind of parameterization is considered for nuclear matter where instead of nucleon numbers one has to deal with densities. a τ is also the parameter which measures the response of the system to a perturbation which tends to separate protons from neutrons. It is given by the static polarizability of the system which also may depend on the asymmetry of the medium. This point has been developped and emphasized recently [4,5]. The spin symmetry energy coefficient of nuclear matter may also be defined, a σ , representing the cost in energy to make the system spin-asymmetric (and eventually polarized nuclear matter). The spin channel is relevant for the study of the neutrino interaction with matter because it couples with axial vector current together with the scalar channel [6,7,8]. A suppression of the spin susceptibility (in this work we will be dealing rather with its inverse) leads to the suppression of Gamow Teller transitions which are of interest for the supernovae mechanism [8] and eventually to instabilities associated to ferromagnetic polarized states [9,8]. In this work we articulate and extend the ideas developped previously for the dependence of symmetry energy coefficients on neutron-proton asymmetry. For this we use a calculation for the static polarizabilities -proportional to the inverse of the symmetry coefficients in asymmetric matterwhich was done using Sky...

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Spin Susceptibility of Neutron Matter at Zero Temperature

Cited by 133 publications

References 18 publications

Quenching of weak interactions in nucleon matter

Quenching of weak interactions in nucleon matter

Phase separation in low-density neutron matter

Symmetry energy coefficients for asymmetric nuclear matter

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