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Nuclear Theory·nucl-th

Thursday·May 26, 2016

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 05

    [Submitted on 23 May 2016] (cross-list from cond-mat.quant-gas)

    The entanglement spectrum and Rényi entropies of non-relativistic conformal fermions

    William J. Porter🇺🇸 · Joaquín E. Drut🇺🇸

    We characterize non-perturbatively the Rényi entropies of degree n=2,3,4, and 5 of three-dimensional, strongly coupled many-fermion systems in the scale-invariant regime of short interaction range and large scattering length, i.e. in the unitary limit. We carry out our calculations using lattice methods devised recently by us. Our results show the effect of strong pairing correlations on the entanglement entropy, which modify the sub-leading behavior for large subsystem sizes (as characterized by the dimensionless parameter x=kF L_A, where kF is the Fermi momentum and L_A the linear subsystem size), but leave the leading order unchanged relative to the non-interacting case. Moreover, we find that the onset of the sub-leading asymptotic regime is at surprisingly small x=2-4. We provide further insight into the entanglement properties of this system by analyzing the spectrum of the entanglement Hamiltonian of the two-body problem from weak to strong coupling. The low-lying entanglement spectrum displays clear features as the strength of the coupling is varied, such as eigenvalue crossing, a sharp change in the Schmidt gap, and scale invariance at unitarity. Beyond the low-lying component, the spectrum appears as a quasi-continuum distribution, for which we present a statistical characterization; we find, in particular, that the mean shifts to infinity as the coupling is turned off, which indicates that that part of the spectrum represents non-perturbative contributions to the entanglement Hamiltonian. In contrast, the low-lying entanglement spectrum evolves to finite values in the noninteracting limit. The scale invariance of the unitary regime guarantees that our results are universal features intrinsic to 3D quantum mechanics and represent a well-defined prediction for ultracold atom experiments, which were recently shown to have direct access to the entanglement entropy.

    Comments:
    18 pages, 13 figures
    Subjects:
    Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1605.07085 [pdf]
    PRB(2016)·11 citations
  2. 06

    [Submitted on 24 May 2016] (cross-list from astro-ph.HE)

    Electrical conductivity of a warm neutron star crust in magnetic fields

    Arus Harutyunyan · Armen Sedrakian

    We study the electrical conductivity of finite-temperature crust of a warm compact star which may be formed in the aftermath of a supernova explosion or a binary neutron star merger as well as when a cold neutron star is heated by accretion of material from a companion. We focus on the temperature-density regime where plasma is in the liquid state and, therefore, the conductivity is dominated by the electron scattering off correlated nuclei. The dynamical screening of this interaction is implemented in terms of the polarization tensor computed in the hard-thermal-loop effective field theory of QED plasma. The correlations of the background ionic component are accounted for via a structure factor derived from Monte Carlo simulations of one-component plasma. With this input we solve the Boltzmann kinetic equation in relaxation time approximation taking into account the anisotropy of transport due to the magnetic field. The electrical conductivity tensor is studied numerically as a function of temperature and density for carbon and iron nuclei as well as density-dependent composition of zero-temperature dense matter in weak equilibrium with electrons. We also provide accurate fit formulas to our numerical results as well as supplemental tables which can be used in dissipative magneto-hydrodynamics simulations of warm compact stars.

    Comments:
    v3: matches published version, 19 pages + 11 pages of supplemental tables, 15 figures; the source includes text-only tables
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1605.07612 [pdf]
    PRC(2016)·74 citations
  3. 07

    [Submitted on 24 May 2016] (cross-list from hep-ph)

    The LPM effect in sequential bremsstrahlung 2: factorization

    Peter Arnold🇺🇸 · Han-Chih Chang🇺🇸 · Shahin Iqbal🇺🇸

    The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue analysis of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-gluon approximations. In particular, this paper analyzes the subtle problem of how to precisely separate overlapping double splitting (e.g.\ overlapping double bremsstrahlung) from the case of consecutive, independent bremsstrahlung (which is the case that would be implemented in a Monte Carlo simulation based solely on single splitting rates). As an example of the method, we consider the rate of real double gluon bremsstrahlung from an initial gluon with various simplifying assumptions (thick media; approximation; large ; and neglect for the moment of processes involving 4-gluon vertices) and explicitly compute the correction due to overlapping formation times.

    Comments:
    59 pages, 37 figures. Change from v3: minor typo fixed on left hand side of eq. (E4); nothing else affected
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1605.07624 [pdf]
    JHEP(2016)·47 citations
  4. 08

    [Submitted on 25 May 2016] (cross-list from nucl-ex)

    Radii and binding energies in oxygen isotopes: a puzzle for nuclear forces

    V. Lapoux🇫🇷 · V. Somà🇫🇷 · C. Barbieri🇬🇧 · H. Hergert🇺🇸 · J.D. Holt🇨🇦 · S.R. Stroberg🇨🇦

    We present a systematic study of both nuclear radii and binding energies in (even) oxygen isotopes from the valley of stability to the neutron drip line. Both charge and matter radii are compared to state-of-the-art {\it ab initio} calculations along with binding energy systematics. Experimental matter radii are obtained through a complete evaluation of the available elastic proton scattering data of oxygen isotopes. We show that, in spite of a good reproduction of binding energies, {\it ab initio} calculations with conventional nuclear interactions derived within chiral effective field theory fail to provide a realistic description of charge and matter radii. A novel version of two- and three-nucleon forces leads to considerable improvement of the simultaneous description of the three observables for stable isotopes, but shows deficiencies for the most neutron-rich systems. Thus, crucial challenges related to the development of nuclear interactions remain.

    Comments:
    6 pages, 5 figures, Submitted to Nature Physics, April 12th 2016; first version (v1 Arxiv) Internal Report Preprint Irfu-18 December 2015. 6 p., 5 fig., Submitted to Physical Review Letters, April 29, May 3rd 2016; 2nd version. Int. Rep. Irfu-24 May 2016. Published in PRL, 27 July 2016 with the modified title (Radii and binding energies in oxygen isotopes: a challenge for nuclear forces)
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1605.07885 [pdf]
    PRL(2016)·136 citations
  5. 09

    [Submitted on 25 May 2016] (cross-list from hep-ph)

    Exotic Discoveries in Familiar Places: Theory of the Onia and Exotics

    Richard F. Lebed🇺🇸

    This brief overview presents an introduction to the heavy-quark exotic hadron candidates, , , , , believed to be tetraquark and pentaquark states. After an abridged account of their discovery, we outline the various theoretical pictures employed to describe their structure, with special focus on the new dynamical diquark picture.

    Comments:
    9 pages, 1 figure. Invited talk at 16th International Conference on B-Physics at Frontier Machines (Beauty 2016). Version accepted by PoS (Proceedings of Science)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1605.07975 [pdf]
    PoS(2016)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE