523 research outputs found

    A Thomas-Fermi model of localization of proton impurities in neutron matter

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    We show that the proton impurity in a neutron matter can create an inhomogeneity in density which acts as a potential well localizing the proton’s wave function. At low densities this inhomogeneity is a neutron bulge, whereas at high densities a neutron deficiency (bubble) occurs. We calculate variationally the proton’s energy using a Gaussian wave function. The neutron background is treated in a Thomas–Fermi approximation. The Skyrme interactions are used. We find that the localized proton has lower energy than the plane wave proton for densities below the lower critical density n1_{1} \cong 0.3n0_{0}, and above the upper critical density nu_{u} \cong 2.2n0_{0}, where n0_{0} = 0.17 fm3^{-3}. We discuss some implications of the proton localization for magnetic properties of neutron matter containing a small admixture of protons

    Mixed quark-nucleon phase in neutron stars and nuclear symmetry energy

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    The influence of the nuclear symmetry energy on the formation of a mixed quark-nucleon phase in neutron star cores is studied. We use simple parametrizations of the nuclear matter equation of state, and the bag model for the quark phase. The behavior of nucleon matter isobars, which is responsible for the existence of the mixed phase, is investigated. The role of the nuclear symmetry energy changes with the value of the bag constant B. For lower values of B the properties of the mixed phase do not depend strongly on the symmetry energy. For larger B we find that a critical pressure for the first quark droplets to form is strongly dependent on the nuclear symmetry energy, but the pressure at which last nucleons disappear is independent of it.Comment: 12 pages, 16 figures, Phys. Rev. C in pres

    Shell model study of the pairing correlations

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    A systematic study of the pairing correlations as a function of temperature and angular momentum has been performed in the sd-shell region using the spherical shell model approach. The pairing correlations have been derived for even-even, even-odd and odd-odd systems near N=Z and also for the asymmetric case of N=Z+4. The results indicate that the pairing content and the behavior of pair correlations is similar in even-even and odd-mass nuclei. For odd-odd N=Z system, angular momentum I=0 state is an isospin, t=1 neutron-proton paired configuration. Further, these t=1 correlations are shown to be dramatically reduced for the asymmetric case of N=Z+4. The shell model results obtained are qualitatively explained within a simplified degenerate model

    Lifetime Measurements in 120Xe

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    Lifetimes for the lowest three transitions in the nucleus 120^{120}Xe have been measured using the Recoil Distance Technique. Our data indicate that the lifetime for the 21+01+2_{1}^{+} \to 0_{1}^{+} transition is more than a factor of two lower than the previously adopted value and is in keeping with more recent measurements performed on this nucleus. The theoretical implications of this discrepancy and the possible reason for the erroneous earlier results are discussed. All measured lifetimes in 120^{120}Xe, as well as the systematics of the lifetimes of the 21+_{1}^{+} states in Xe isotopes, are compared with predictions of various models. The available data are best described by the Fermion Dynamic Symmetry Model (FDSM).Comment: 9 pages, RevTeX, 3 figures with Postscript file available on request at [email protected], [email protected]. Submitted to Phys. Rev.

    Low Energy Skyrmion-Skyrmion Scattering

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    We study the scattering of Skyrmions at low energy and large separation using the method proposed by Manton of truncation to a finite number of degrees freedom. We calculate the induced metric on the manifold of the union of gradient flow curves, which for large separation, to first non-trivial order is parametrized by the variables of the product ansatz. (presented at the Lake Louise Winter Institute, 1994)Comment: 6 page

    Degeneracies when T=0 Two Body Matrix Elements are Set Equal to Zero and Regge's 6j Symmetry Relations

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    The effects of setting all T=0 two body interaction matrix elements equal to a constant (or zero) in shell model calculations (designated as =0=0) are investigated. Despite the apparent severity of such a procedure, one gets fairly reasonable spectra. We find that using =0=0 in single j shell calculations degeneracies appear e.g. the I=1/2I={1/2} ^{-} and 13/2{13/2}^{-} states in 43^{43}Sc are at the same excitation energies; likewise the I=32+3_{2}^{+},72+7_{2}^{+},91+^{+}_{1} and 101+^{+}_{1} states in 44^{44}Ti. The above degeneracies involve the vanishing of certain 6j and 9j symbols. The symmetry relations of Regge are used to explain why these vanishings are not accidental. Thus for these states the actual deviation from degeneracy are good indicators of the effects of the T=0 matrix elements. A further indicator of the effects of the T=0 interaction in an even - even nucleus is to compare the energies of states with odd angular momentum with those that are even