36,036 research outputs found

    BCS-BEC crossover in nuclear matter with the relativistic Hartree-Bogoliubov theory

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    Based on the relativistic Hartree-Bogoliubov theory, the influence of the pairing interaction strength on the di-neutron correlations and the crossover from superfluidity of neutron Cooper pairs in the 1S0^{1}S_{0} channel to Bose-Einstein condensation of di-neutron pairs is systematically investigated in the nuclear matter. The bare nucleon-nucleon interaction Bonn-B is taken in the particle-particle channel with an effective factor to simulate the medium effects and take into account the possible ambiguity of pairing force, and the effective interaction PK1 is used in the particle-hole channel. If the effective factor is larger than 1.10, a di-neutron BEC state appears in the low-density limit, and if it is smaller than 0.85, the neutron Cooper pairs are found totally in the weak coupling BCS region. The reference values of several characteristic quantities which characterize the BCS-BEC crossover are obtained respectively from the dimensionless parameter 1/(kFna)1/(k_{\rm Fn}a) with aa the scattering length and kFnk_{\rm{Fn}} the neutron Fermi momentum, the zero-momentum transfer density correlation function D(0) and the effective chemical potential νn\nu_{\rm n}.Comment: 8 pages, 4 figures, 2 tables, Accepted Thursday Jun 14, 2012 for Physical Review

    Challenge on the Astrophysical R-process Calculation with Nuclear Mass Models

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    Our understanding of the rapid neutron capture nucleosynthesis process in universe depends on the reliability of nuclear mass predictions. Initiated by the newly developed mass table in the relativistic mean field theory (RMF), in this paper the influence of mass models on the rr-process calculations is investigated assuming the same astrophysical conditions. The different model predictions on the so far unreachable nuclei lead to significant deviations in the calculated r-process abundances.Comment: 3 pages, 3 figure

    Influence of nuclear physics inputs and astrophysical conditions on Th/U chronometer

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    The productions of thorium and uranium are key ingredients in rr-process nucleo-cosmochronology. With the combination of improved nuclear and stellar data, we have made detailed investigations on the rr-process abundance pattern in the very metal-poor halo stars based on the classical rr-process approach. It is found that the results are almost independent of specified simulations to observed abundances. The influence from nuclear mass uncertainties on Th/U chronometer can approach 2 Gyr. Moreover, the ages of the metal-poor stars HE 1523-0901, CS 31082-001, and BD +17^\circ3248 are determined as 11.8±3.711.8\pm 3.7, 13.5±2.913.5\pm 2.9, and 10.9±2.910.9 \pm 2.9 Gyr, respectively. The results can serve as an independent check for age estimate of the universe.Comment: 20 pages, 5 figures. accepted by Phys. Rev.

    Pairing Properties of Symmetric Nuclear Matter in Relativistic Mean Field Theory

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    The properties of pairing correlations in symmetric nuclear matter are studied in the relativistic mean field (RMF) theory with the effective interaction PK1. Considering well-known problem that the pairing gap at Fermi surface calculated with RMF effective interactions are three times larger than that with Gogny force, an effective factor in the particle-particle channel is introduced. For the RMF calculation with PK1, an effective factor 0.76 give a maximum pairing gap 3.2 MeV at Fermi momentum 0.9 fm1^{-1}, which are consistent with the result with Gogny force.Comment: 14 pages, 6 figures