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Nuclear Theory·nucl-th

Friday·December 21, 2018

16 papers—7 primary·9 cross-listed

All16Primary7Cross-lists9
  1. 01

    Chiral symmetry restoration by parity doubling and the structure of neutron stars

    Michał Marczenko · David Blaschke · Krzysztof Redlich · Chihiro Sasaki

    Recent lattice QCD studies at vanishing density exhibit the parity-doubling structure for the low-lying baryons around the chiral crossover temperature. This finding is likely an imprint of the chiral symmetry restoration in the baryonic sector of QCD, and is expected to occur also in cold dense matter, which makes it of major relevance for compact stars. By contrast, typical effective models for compact star matter embody chiral physics solely in the deconfined sector, with quarks as degrees of freedom. In this contribution, we present a description of QCD matter based on the effective hybrid quark-meson-nucleon model. Its characteristic feature is that, under neutron-star conditions, the chiral symmetry is restored in a first-order phase transition deep in the hadronic phase, before the deconfinement of quarks takes place. We discuss the implications of the parity doubling of baryons on the mass-radius relation for compact stars obtained in accordance with the modern constraints on the mass from PSR J0348+0432, the compactness from GW170817, as well as the direct URCA process threshold. We show that the existence of high-mass stars might not necessarily signal the deconfinement of quarks.

    nucl-thPoS(2018)·0 citations
  2. 02

    Iterative approaches to the self-consistent nuclear energy density functional problem. Heavy ball dynamics and potential preconditioning

    W. Ryssens🇺🇸 · M. Bender🇫🇷 · P.-H. Heenen🇧🇪

    Large-scale applications of energy density functional (EDF) methods depend on fast and reliable algorithms to solve the associated non-linear self-consistency problem. When dealing with large single-particle variational spaces, existing solvers can become very slow, and their performance dependent on manual fine-tuning of numerical parameters. In addition, convergence can sensitively depend on particularities of the EDF's parametrisation under consideration. Using the widely-used Skyrme EDF as an example, we investigate the impact of the parametrisation of the EDF, both in terms of the operator structures present and the size of coupling constants, on the convergence of numerical solvers. We focus on two aspects of the self-consistency cycle, which are the diagonalisation of a fixed single-particle Hamiltonian on one hand and the evolution of the mean-field densities and potentials on the other. Throughout the article we use a coordinate-space representation, for which the behaviour of algorithms can be straightforwardly analysed. We propose two algorithmic improvements that are easily implementable in existing solvers, heavy-ball dynamics and potential preconditioning. We demonstrate that these methods can be made virtually parameter-free, requiring no manual fine-tuning to achieve near-optimal performance except for isolated cases. The combination of both methods decreases substantially the CPU time required to obtain converged results. The improvements are illustrated for the MOCCa code that solves the self-consistent HFB problem in a 3d coordinate space representation for parametrisations of the standard Skyrme EDF at next-to-leading order in gradients and its extension to next-to-next-to-leading order.

    nucl-thEPJA(2019)·19 citations
  3. 03

    Dilute Fermi gas at fourth order in effective field theory

    C. Wellenhofer🇩🇪 · C. Drischler🇺🇸 · A. Schwenk🇩🇪

    Using effective field theory methods, we calculate for the first time the complete fourth-order term in the Fermi-momentum or expansion for the ground-state energy of a dilute Fermi gas. The convergence behavior of the expansion is examined for the case of spin one-half fermions and compared against quantum Monte-Carlo results, showing that the Fermi-momentum expansion is well-converged at this order for .

    nucl-thcond-mat.quant-gashep-phPLB(2020)·20 citations
  4. 04

    Low-lying dipole strengths for probable -wave one-neutron halos in the medium mass region

    Manju (IITR) · J. Singh (Uni Hokkaido) · Shubhchintak (ULB) · R. Chatterjee (IITR)

    The one-neutron halos lying in the island of inversion around has provided the podium, to study the variation of total low-lying dipole strength with the neutron separation energy. We study three probable p-wave one-neutron halo candidates 31Ne and 34Na and 37Mg lying in the island of inversion. A simple analytic model has been used for the calculation of the total low-lying dipole strength for the medium mass p-wave one-neutron halos. A correction factor to this analytical model has been estimated with a realistic Woods-Saxon potential. A comparison of these analytic calculations has been made with the those performed by a finite-range distorted-wave Born approximation theory of the Coulomb dissociation. We also make an estimate of the one-neutron separation energies of 31Ne, 34Na and 37Mg.

    nucl-thnucl-exEPJA(2019)·14 citations
  5. 05

    Bottom Production in Collisions at Large Hadron Collider Energies using Parton Cascade Model

    Rupa Chatterjee · Dinesh K. Srivastava

    We study the production of bottom quarks in collisions at Large Hadron Collider energies using previously developed parton cascade model to explore the impact of Landau Pomeranchuk Midgal (LPM) effect on their dynamics. In contrast to the case for charm quarks reported recently, we find only a marginal impact of the suppression of multiple scatterings of partons due to the LPM effect on their production. It is felt that this happens as they are only produced in very hard collisions.

    nucl-thhep-ph1 citation
  6. 06

    Proton elastic scattering on calcium isotopes from chiral nuclear optical potentials

    T. R. Whitehead · Y. Lim · J. W. Holt

    We formulate microscopic optical potentials for nucleon-nucleus scattering from chiral two- and three-nucleon forces. The real and imaginary central terms of the optical potentials are obtained from the nucleon self energy in infinite nuclear matter at a given density and isospin asymmetry, calculated self-consistently to second order in many-body perturbation theory. The real spin-orbit term is extracted from the same chiral potential using an improved density matrix expansion. The density-dependent optical potential is then folded with the nuclear density distributions of 40Ca, 42Ca, 44Ca, and 48Ca from which we study proton-nucleus elastic scattering and total reaction cross sections using the reaction code TALYS. We compare the results of the microscopic calculations to those of phenomenological models and experimental data up to projectile energies of E = 180 MeV. While overall satisfactory agreement with the available experimental data is obtained, we find that the elastic scattering and total reaction cross sections can be significantly improved with a weaker imaginary optical potential, particularly for larger projectile energies.

    nucl-thPRC(2019)·37 citations
  7. 07

    Ab initio no-core shell model study of O and F isotopes

    Archana Saxena · Praveen C. Srivastava

    In the present work, we have done a comprehensive study of low-lying energy spectrum for oxygen and fluorine chains using no core shell model. We have used inside nonlocal outside Yukawa (INOY) potential, which is a two body interaction but also has the effect of three body forces by short range and nonlocal character. Also, we have performed calculations with N3LO and N2LOopt interactions and compared corresponding results with the experimental data and phenomenological USDB interaction. We have reached up to =6 for O and F, =4 for other oxygen and fluorine isotopes, respectively. We have also discussed the binding energy of oxygen and fluorine chains. Over binding in the ground state (g.s.) energy in neutron rich oxygen isotopes is observed in our largest model space calculations.

    nucl-thJ.Phys.G(2020)·19 citations

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first authorsco-authorsvia INSPIRE