8,096 research outputs found

    Halos in medium-heavy and heavy nuclei with covariant density functional theory in continuum

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    The covariant density functional theory with a few number of parameters has been widely used to describe the ground-state and excited-state properties for the nuclei all over the nuclear chart. In order to describe exotic properties of unstable nuclei, the contribution of the continuum and its coupling with bound states should be treated properly. In this Topical Review, the development of the covariant density functional theory in continuum will be introduced, including the relativistic continuum Hartree-Bogoliubov theory, the relativistic Hartree-Fock-Bogoliubov theory in continuum, and the deformed relativistic Hartree-Bogoliubov theory in continuum. Then the descriptions and predictions of the neutron halo phenomena in both spherical and deformed nuclei will be reviewed. The diffuseness of the nuclear potentials, nuclear shapes and density distributions, and the impact of the pairing correlations on nuclear size will be discussed.Comment: 63 pages; Topical Review, J. Phys. G (in press

    Microscopic linear response calculations based on the Skyrme functional plus the pairing contribution

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    A self-consistent Quasiparticle-Random-Phase-Approximation (QRPA) model which employs the canonical Hartree-Fock-Bogoliubov (HFB) basis and an energy-density functional with a Skyrme mean field part and a density-dependent pairing, is used to study the monopole collective excitations of spherical even-even nuclei. The influence of the spurious state on the strength function of the isoscalar monopole excitations is clearly assessed. We compare the effect of different kinds of pairing forces (volume pairing, surface pairing and mixed pairing) on the monopole excitation strength function. The energy of the Isoscalar Giant Monopole Resonance (ISGMR), which is related to the nuclear incompressibility KK_{\infty}, is calculated for tin isotopes and the results are discussed.Comment: Accepted for publication in Phys. Rev.

    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.

    Transfer Learning across Networks for Collective Classification

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    This paper addresses the problem of transferring useful knowledge from a source network to predict node labels in a newly formed target network. While existing transfer learning research has primarily focused on vector-based data, in which the instances are assumed to be independent and identically distributed, how to effectively transfer knowledge across different information networks has not been well studied, mainly because networks may have their distinct node features and link relationships between nodes. In this paper, we propose a new transfer learning algorithm that attempts to transfer common latent structure features across the source and target networks. The proposed algorithm discovers these latent features by constructing label propagation matrices in the source and target networks, and mapping them into a shared latent feature space. The latent features capture common structure patterns shared by two networks, and serve as domain-independent features to be transferred between networks. Together with domain-dependent node features, we thereafter propose an iterative classification algorithm that leverages label correlations to predict node labels in the target network. Experiments on real-world networks demonstrate that our proposed algorithm can successfully achieve knowledge transfer between networks to help improve the accuracy of classifying nodes in the target network.Comment: Published in the proceedings of IEEE ICDM 201

    Octet-baryon masses in finite space

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    We report on a recent study of finite-volume effects on the lowest-lying octet baryon masses using the covariant baryon chiral perturbation theory up to next-to-leading order by analysing the latest nf=2+1n_f = 2 + 1 lattice QCD results from the NPLQCD Collaboration.Comment: 4 pages, 1 figure; parallel talk delivered by XLR at the 14th national conference on nuclear structure, April 12nd - 16th, 2012, Huzhou, Chin

    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