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Nuclear Theory·nucl-th

Monday·January 29, 2018

5 papers—5 primary·0 cross-listed

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  1. 01

    N* Structure and Strong QCD

    Craig D. Roberts🇺🇸

    In attempting to match QCD with Nature, it is necessary to confront the many complexities of strong, nonlinear dynamics in relativistic quantum field theory, e.g. the loss of particle number conservation, the frame and scale dependence of the explanations and interpretations of observable processes, and the evolving character of the relevant degrees-of-freedom. The peculiarities of QCD ensure that it is also the only known fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, gluons and quarks; and yet gluons and quarks are predicted to acquire mass dynamically so that the only massless systems in QCD are its composite Nambu-Goldstone bosons. All other everyday bound states possess nuclear-size masses, far in excess of anything that can directly be tied to the Higgs boson. These observations highlight fundamental questions within the Standard Model: what is the source of the mass for the vast bulk of visible matter in the Universe, how is its appearance connected with confinement; how is this mass distributed within hadrons and does the distribution differ from one hadron to another? This contribution sketches insights drawn using modern methods for the continuum bound-state problem in QCD, and how they have been informed by empirical information on the hadron spectrum and nucleon-to-resonance transition form factors.

    nucl-thhep-lathep-phnucl-exFew Body Syst.(2018)·23 citations
  2. 02

    Probing the tricritical endpoint of QCD phase diagram at NICA-FAIR energies

    K. A. Bugaev🇺🇦 · A. I. Ivanytskyi🇺🇦 · V. V. Sagun🇺🇦 · G. M. Zinovjev🇺🇦 · E. G. Nikonov🇷🇺 · R. Emaus🇳🇴 · L. V. Bravina🇳🇴 · E. E. Zabrodin🇳🇴 · A. V. Taranenko🇷🇺

    In this contributions we discuss the novel version of hadron resonance gas model which is based on the induced surface tension concept. Also we present new arguments in favor of a hypothesis that the chiral symmetry restoration transition in central nuclear collisions may occur at the center of mass energies 4.3-4.9 GeV and that the deconfinement phase transition may occur at the center of mass energies 8.8-9.2 GeV. These arguments are based on the unique thermostatic properties of the mixed phase and the ones of an exponential mass spectrum of hadrons.

    nucl-thEPJ Web Conf.(2018)·2 citations
  3. 03

    Microscopically-based energy density functionals for nuclei using the density matrix expansion: Full optimization and validation

    R. Navarro Perez🇺🇸 · N. Schunck🇺🇸 · A. Dyhdalo🇺🇸 · R.J. Furnstahl🇺🇸 · S.K. Bogner🇺🇸

    We seek to obtain a usable form of the nuclear energy density functional that is rooted in the modern theory of nuclear forces. We thus consider a functional obtained from the density matrix expansion of local nuclear potentials from chiral effective field theory. We propose a parametrization of this functional carefully calibrated and validated on selected ground-state properties that is suitable for large-scale calculations of nuclear properties. The first component of this functional is a non-local functional of the density and corresponds to the direct part (Hartree term) of the expectation value of local chiral potentials on a Slater determinant. A second component is a local functional of the density and is obtained by applying the density matrix expansion to the exchange part (Fock term) of the expectation value of the local chiral potential. We apply the UNEDF2 optimization protocol to determine the coupling constants of this energy functional. We obtain a set of microscopically-constrained functionals for local chiral potentials from leading-order up to next-to-next-to-leading order with and without three-body forces and contributions from excitations. These functionals are validated on the calculation of nuclear and neutron matter, nuclear mass tables, single-particle shell structure in closed-shell nuclei and the fission barrier of Pu. Quantitatively, they perform noticeable better than the more phenomenological Skyrme functionals. The inclusion of higher-order terms in the chiral perturbation expansion seems to produce a systematic improvement in predicting nuclear binding energies. This result is especially promising since all the fits have been performed at the single reference level of the energy density functional approach, where important collective correlations such as center-of-mass correction have not been taken into account yet.

    nucl-thhep-phnucl-exPRC(2018)·47 citations
  4. 04

    Nuclear fourth-order symmetry energy and its effects on neutron star properties in the relativistic Hartree-Fock theory

    Zhi Wei Liu · Zhuang Qian · Ruo Yu Xing · Jia Rui Niu · Bao Yuan Sun

    Adopting the density dependent relativistic mean-field (RMF) and relativistic Hartree-Fock (RHF) approaches, the properties of the nuclear fourth-order symmetry energy are studied within the covariant density functional (CDF) theory. It is found that the fourth-order symmetry energies are suppressed in RHF at both saturation and supranuclear densities, where the extra contribution from the Fock terms is demonstrated, specifically via the isoscalar meson-nucleon coupling channels. The reservation of and higher-order symmetry energies in the nuclear equation of state then affects essentially the prediction of neutron star properties, which is illustrated in the quantities such as the proton fraction, the core-crust transition density as well as the fraction of crustal moment of inertia. Since the Fock terms enhance the density dependence of the thermodynamical potential, the RHF calculations predict systematically smaller values of density, proton fraction and pressure at the core-crust transition boundary of neutron stars than density dependent RMF ones. In addition, a linear anti-correlation between the core-crust transition density and the density slope of symmetry energy is found which is then utilized to constrain the core-crust transition density as with the recent empirical information on . The study clarifies the important role of the fourth-order symmetry energy in determining the properties of nuclear matter at extreme isospin or density conditions.

    nucl-thPRC(2018)·40 citations
  5. 05

    Beyond the neutron-drip line: two-neutron decay of unbound nuclei

    K. Hagino · H. Sagawa

    We discuss a decay of unbound nuclei beyond the neutron drip-line using a three-body model with a core nucleus and two valence neutrons. We particularly discuss the role of dineutron correlation between the valence neutrons in the two-neutron emission from the ground state of O and He nuclei. Our calculations clearly indicate that the emission of the two neutrons in the back-to-back direction is enhanced due to the dineutron correlation.

    nucl-thnucl-exJPS Conf.Proc.(2018)·1 citation

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first authorsco-authorsvia INSPIRE