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Nuclear Theory·nucl-th

Friday·January 1, 2016

11 papers—3 primary·8 cross-listed

All11Primary3Cross-lists8
  1. 01

    [Submitted on 30 Dec 2015]

    Finite amplitude method applied to giant dipole resonance in heavy rare-earth nuclei

    Tomohiro Oishi · Markus Kortelainen · Nobuo Hinohara

    Background: The quasiparticle random phase approximation (QRPA), within the framework of the nuclear density functional theory (DFT), has been a standard tool to access the collective excitations of the atomic nuclei. Recently, finite amplitude method (FAM) has been developed, in order to perform the QRPA calculations efficiently without any truncation on the two-quasiparticle model space. Purpose: We discuss the nuclear giant dipole resonance (GDR) in heavy rare-earth isotopes, for which the conventional matrix diagonalization of the QRPA is numerically demanding. A role of the Thomas-Reiche-Kuhn (TRK) sum rule enhancement factor, connected to the isovector effective mass, is also investigated. Methods: The electric dipole photoabsorption cross section was calculated within a parallelized FAM-QRPA scheme. We employed the Skyrme energy density functional self-consistently in the DFT calculation for the ground states and FAM-QRPA calculation for the excitations. Results: The mean GDR frequency and width are mostly reproduced with the FAM-QRPA, when compared to experimental data, although some deficiency is observed with isotopes heavier than erbium. A role of the TRK enhancement factor in actual GDR strength is clearly shown: its increment leads to a shift of the GDR strength to higher-energy region, without a significant change in the transition amplitudes. Conclusions: The newly developed FAM-QRPA scheme shows a remarkable efficiency, which enables to perform systematic analysis of GDR for heavy rare-earth nuclei. Theoretical deficiency of photoabsorption cross section could not be improved by only adjusting the TRK enhancement factor, suggesting the necessity of beyond the self-consistent QRPA approach, and/or a more systematic optimization of the EDF parameters.

    Comments:
    11 pages, 7 figures, 3 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1512.09146 [pdf]
    PRC(2016)·44 citations
  2. 02

    [Submitted on 30 Dec 2015]

    High temperature Bose-Einstein condensation

    Viktor V. Begun🇵🇱

    The indications of a possible pion condensation at the LHC are summarized. The condensation is predicted by the non-equilibrium hadronization model for 2.76 TeV Pb+Pb collisions at the LHC. The model solves the proton/pion puzzle and reproduces the low enhancement of the pion spectra, as well as the spectra of protons and antiprotons, charged kaons, , and . The obtained parameters allow to estimate the amount of pion condensate on the level of 5\% from the total number of pions at the LHC. The condensate is located at MeV.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1512.09157 [pdf]
    EPJ Web Conf.(2016)·4 citations
  3. 03

    [Submitted on 30 Dec 2015]

    The Constant-Sound-Speed parameterization for NJL models of quark matter in hybrid stars

    Ignacio F. Ranea-Sandoval🇦🇷 · Sophia Han🇺🇸 · Milva G. Orsaria🇦🇷 · Gustavo A. Contrera🇦🇷 · Fridolin Weber🇺🇸 · Mark G. Alford🇺🇸

    The discovery of pulsars as heavy as 2 solar masses has led astrophysicists to rethink the core compositions of neutron stars, ruling out many models for the nuclear equations of state (EoS). We explore the hybrid stars that occur when hadronic matter is treated in a relativistic mean-field approximation and quark matter is modeled by three-flavor local and non-local Nambu Jona-Lasinio (NJL) models with repulsive vector interactions. The NJL models typically yield equations of state that feature a first order transition to quark matter. Assuming that the quark-hadron surface tension is high enough to disfavour mixed phases, and restricting to EoSes that allow stars to reach 2 solar masses, we find that the appearance of the quark matter core either destabilizes the star immediately (this is typical for non-local NJL models) or leads to a very short hybrid star branch in the mass-radius relation (this is typical for local NJL models). Using the Constant-Sound-Speed parametrization we can see that the reason for the near-absence of hybrid stars is that the transition pressure is fairly high and the transition is strongly first order.

    Comments:
    14 pages, 6 figures. Accepted for publication in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    1512.09183 [pdf]
    PRC(2016)·72 citations

Affiliations

first authorsco-authorsvia INSPIRE