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Nuclear Theory·nucl-th

Monday·October 29, 2018

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 26 Oct 2018]

    Nuclear structure and the nucleon effective mass: explorations with the versatile KIDS functional

    Panagiota Papakonstantinou🇰🇷 · Hana Gil🇰🇷

    The connection from the structure and dynamics of atomic nuclei (finite nuclear system) to the nuclear equation of state (thermodynamic limit) is primarily made through nuclear energy-density functional (EDF) theory. Failure to describe both entities simultaneously within existing EDF frameworks means that we have either seriously misjudged the scope of EDF or not fully taken advantage of it. Enter the versatile KIDS Ansatz, which is based on controlled, order-by-order extensions of the nuclear EDF with respect to the Fermi momentum and allows a direct mapping from a given, immutable equation of state to a convenient Skyrme pseudopotential for applications in finite nuclei. A recent proof-of-principle study of nuclear ground-states revealed the subversive role of the effective mass. Here we summarize the formalism and previous results and present further explorations related to giant resonances. As examples we consider the electric dipole polarizability of 68Ni and the giant monopole resonance (GMR) of heavy nuclei, particularly the "fluffiness" of 120Sn. We find that the choice of the effective mass parameters and that of the compression modulus affect the centroid energy of the GMR to comparable degrees.

    Comments:
    8 pages, incl. 2 figures; prepared for the Procs. 27th Annual Symposium of the Hellenic Nuclear Physics Society (HNPS2018), June 8-9 2018, Athens. Greece
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1810.11198 [pdf]
    Adv.Nucl.Phys.(2019)·3 citations
  2. 02

    [Submitted on 26 Oct 2018]

    Empirical pairing gaps and neutron-proton correlations

    B.S. Ishkhanov · S. Sidorov · T. Tretyakova · E. Vladimirova

    Analysis of various mass relations connected with neutron-proton correlations in atomic nuclei is carried out. On the example of chain it is shown that for self-adjoint nuclei various formulas proposed in literature for pairing energy estimations lead to similar results. Significant differences between the calculation methods arise when nuclei with are considered, which allows to show the complexity of neutron-proton correlations in different types of atomic nuclei and to make some assumptions on the correspondence of a mass ratio to the real effect of pairing. The Shell Model parametrization of binding energy makes it possible to arrive to additional conclusions on the structure of mass formulas and their interrelationships with one another.

    Comments:
    15 pages, 9 figures, to be published in Chinese Physics C
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1810.11210 [pdf]
    CPC(2019)·8 citations
  3. 03

    [Submitted on 26 Oct 2018]

    Particle-number projected Bogoliubov coupled cluster theory. Application to the pairing Hamiltonian

    Y. Qiu🇺🇸 · T. M. Henderson🇺🇸 · T. Duguet🇫🇷 · G. E. Scuseria🇺🇸

    While coupled cluster theory accurately models weakly correlated quantum systems, it often fails in the presence of strong correlations where the standard mean-field picture is qualitatively incorrect. In many cases, these failures can be largely ameliorated by permitting the mean-field reference to break physical symmetries. Symmetry-broken coupled cluster, e.g. Bogoliubov coupled cluster, theory can indeed provide reasonably accurate energetic predictions, but the broken symmetry can compromise the quality of the resulting wave function and predictions of observables other than the energy. Merging symmetry projection and coupled cluster theory is therefore an appealing way to describe strongly correlated systems. Independently, two different but related formalisms have been recently proposed to achieve this goal. The two formalisms are contrasted in this manuscript, with results tested on the Richardson pairing Hamiltonian. Both formalisms are based on the disentangled cluster representation of the symmetry-rotated coupled cluster wavefunction. However, they differ in the way that the disentangled clusters are solved. One approach sets up angle-dependent coupled cluster equations, while the other involves first-order ordinary differential equations. The latter approach yields energies and occupation probabilities significantly better than those of number-projected BCS and BCS coupled cluster and, when the disentangled clusters are truncated at low excitation levels, has a computational cost not too much larger than that of BCS coupled cluster. The high quality of results presented in this manuscript indicates that symmetry-projected coupled cluster is a promising method that can accurately describe both weakly and strongly correlated finite many-fermion systems.

    Comments:
    20 pages, 9 figures (1 figure added)
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el); physics.chem-ph (physics.chem-ph)
    arXiv:
    1810.11245 [pdf]
    PRC(2019)·41 citations
  4. 04

    [Submitted on 26 Oct 2018]

    An exact solution of spherical mean-field plus orbit-dependent non-separable pairing model with two non-degenerate j-orbits

    Feng Pan · Shuli Yuan · Yingwen He · Yunfeng Zhang · Siyu Yang · J. P. Draayer

    An exact solution of nuclear spherical mean-field plus orbit-dependent non-separable pairing model with two non-degenerate j-orbits is presented. The extended one-variable Heine-Stieltjes polynomials associated to the Bethe ansatz equations of the solution are determined, of which the sets of the zeros give the solution of the model, and can be determined relatively easily. A comparison of the solution to that of the standard pairing interaction with constant interaction strength among pairs in any orbit is made. It is shown that the overlaps of eigenstates of the model with those of the standard pairing model are always large, especially for the ground and the first excited state. However, the quantum phase crossover in the non-separable pairing model cannot be accounted for by the standard pairing interaction.

    Comments:
    5 pages, 1 figure, LaTeX
    Subjects:
    Nuclear Theory (nucl-th); Mathematical Physics (math-ph); math.MP (math.MP); Quantum Physics (quant-ph)
    arXiv:
    1810.11267 [pdf]
    NPA(2019)·7 citations
  5. 05

    [Submitted on 25 Oct 2018] (cross-list from hep-lat)

    Reliability of Taylor expansions in QCD

    Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪

    We investigate the reliability of the Taylor expansion method in QCD with isospin chemical potentials using lattice simulations. By comparing the expansion of the number density to direct results, the range of validity of the leading- and next-to-leading order expansions is determined. We also elaborate on the convergence properties of the Taylor series by comparing the leading estimate for the radius of convergence to the position of the nearest singularity, i.e. the onset of pion condensation. Our results provide a handle for quantifying the uncertainties of Taylor expansions in baryon chemical potentials.

    Comments:
    8 pages, 8 figures; v2: typos corrected, reference list updated, discussion on finite size effects clarified
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1810.11045 [pdf]
    PRD(2019)·46 citations
  6. 06

    [Submitted on 26 Oct 2018] (cross-list from hep-ph)

    TMD factorization for dijets + photon production from the dilute-dense CGC framework

    Tolga Altinoluk🇵🇱 · Renaud Boussarie🇵🇱 · Cyrille Marquet🇫🇷 · Pieter Taels🇮🇹

    We calculate the production of a photon and two jets at forward rapidity in proton-nucleus collisions, within the hybrid dilute-dense framework in the Color Glass Condensate (CGC) formalism. After obtaining the cross section for both the quark- and gluon-initiated channels, we consider the correlation limit, in which the vector sum of the transverse momenta of the three outgoing particles is small with respect to the individual transverse momenta. In this limit, the cross section simplifies considerably and can be written in a factorized form, sensitive to various unpolarized and linearly-polarized transverse-momentum-dependent gluon distribution functions (gluon TMDs). Thus, we demonstrate for the first time that the emergence of a TMD factorization formula in the correlation limit, from CGC expressions, holds beyond the previously-considered simpler processes.

    Comments:
    65 pages, 2 figures. V2: Typos corrected, references added, sign mistake corrected, main results remained unchanged, new appendix added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1810.11273 [pdf]
    JHEP(2019)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE