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Nuclear Theory·nucl-th

Wednesday·December 31, 2014

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    [Submitted on 29 Dec 2014]

    Pasta Nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

    M. E. Caplan · A. S. Schneider · C. J. Horowitz · D. K. Berry

    Background: Exotic non-spherical nuclear pasta shapes are expected in nuclear matter at just below saturation density because of competition between short range nuclear attraction and long range Coulomb repulsion. Purpose: We explore the impact of nuclear pasta on nucleosynthesis, during neutron star mergers, as cold dense nuclear matter is ejected and decompressed. Methods: We perform classical molecular dynamics simulations with 51200 and 409600 nucleons, that are run on GPUs. We expand our simulation region to decompress systems from an initial density of 0.080 fm^{-3} down to 0.00125 fm^{-3}. We study proton fractions of Y_P=0.05, 0.10, 0.20, 0.30, and 0.40 at T =0.5, 0.75, and 1.0 MeV. We calculate the composition of the resulting systems using a cluster algorithm. Results: We find final compositions that are in good agreement with nuclear statistical equilibrium models for temperatures of 0.75 and 1 MeV. However, for proton fractions greater than Y_P=0.2 at a temperature of T = 0.5 MeV, the MD simulations produce non-equilibrium results with large rod-like nuclei. Conclusions: Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.

    Comments:
    13 pages
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    1412.8502 [pdf]
    PRC(2015)·27 citations
  2. 02

    [Submitted on 30 Dec 2014]

    The emergent dynamical symmetry at the triple point of nuclear deformations

    Yu Zhang · Feng Pan · Yu-xin Liu · Yan-an Luo · J. P. Draayer

    Based on the boson realization of the Euclidean algebras, it is shown that the five-dimensional Euclidean dynamical symmetry may emerge at the triple point of the shape phase diagram of the interacting boson model, which thus offers a symmetry-based understanding of this isolated point. It is further shown that the low-lying dynamics in Pd, Ba, Zn, and Cd may be dominated by the Euclidean dynamical symmetry.

    Comments:
    8 pages, 5 figures, 1 table
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1412.8557 [pdf]
    PRC(2014)·15 citations
  3. 03

    [Submitted on 30 Dec 2014]

    Hypernuclei and the hyperon problem in neutron stars

    Paulo F. Bedaque🇺🇸 · Andrew W. Steiner🇺🇸

    The likely presence of baryons in dense hadronic matter tends to soften the equation of state to an extend that the observed heaviest neutron stars are difficult to explain. We analyze this "hyperon problem" with a phenomenological approach. First, we review what can be learned about the interaction of particle with dense matter from the observed hypernuclei and extend this phenomenological analysis to asymmetric matter. We add to this the current knowledge on non-strange dense matter, including its uncertainties, to conclude that the interaction between s and dense matter has to become repulsive at densities below three times the nuclear saturation density.

    Comments:
    9 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1412.8686 [pdf]
    PRC(2015)·20 citations
  4. 04

    [Submitted on 29 Dec 2014] (cross-list from hep-th)

    OPE convergence in non-relativistic conformal field theories

    Walter D. Goldberger🇺🇸 · Zuhair U. Khandker🇺🇸 · Siddharth Prabhu🇺🇸

    Motivated by applications to the study of ultracold atomic gases near the unitarity limit, we investigate the structure of the operator product expansion (OPE) in non-relativistic conformal field theories (NRCFTs). The main tool used in our analysis is the representation theory of charged (i.e. non-zero particle number) operators in the NRCFT, in particular the mapping between operators and states in a non-relativistic "radial quantization" Hilbert space. Our results include: a determination of the OPE coefficients of descendant operators in terms of those of the underlying primary state, a demonstration of convergence of the (imaginary time) OPE in certain kinematic limits, and an estimate of the decay rate of the OPE tail inside matrix elements which, as in relativistic CFTs, depends exponentially on operator dimensions. To illustrate our results we consider several examples, including a strongly interacting field theory of bosons tuned to the unitarity limit, as well as a class of holographic models. Given the similarity with known statements about the OPE in SO(2,d) invariant field theories, our results suggest the existence of a bootstrap approach to constraining NRCFTs, with applications to bound state spectra and interactions. We briefly comment on a possible implementation of this non-relativistic conformal bootstrap program.

    Comments:
    35 pages, v2: references added, minor typos corrected
    Subjects:
    High Energy Physics — Theory (hep-th); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
    arXiv:
    1412.8507 [pdf]
    JHEP(2015)·51 citations
  5. 05

    [Submitted on 30 Dec 2014] (cross-list from hep-ph)

    Confronting fluctuations of conserved charges in central nuclear collisions at the LHC with predictions from Lattice QCD

    Peter Braun-Munzinger🇩🇪 · Alexander Kalweit🇨🇭 · Krzysztof Redlich🇵🇱 · Johanna Stachel🇩🇪

    We construct net baryon number and strangeness susceptibilities as well as correlations between electric charge and strangeness from experimental data of the ALICE Collaboration at the CERN LHC. The data were taken in Pb-Pb collisions at =2.76 TeV. The resulting fluctuations and correlations are consistent with Lattice QCD results at the chiral crossover pseudocritical temperature MeV. This agreement lends strong support to the assumption that the fireball created in these collisions is of thermal origin and exhibits characteristic properties expected in QCD at the transition from the quark gluon plasma to the hadronic phase. The volume of the fireball for one unit of rapidity at is found to exceed 4000 fm. A detailed discussion on uncertainties in the temperature and volume of the fireball is presented. The results are linked to pion interferometry measurements and predictions from percolation theory.

    Comments:
    7 pages, 4 figures Accepted for publication in PLB
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1412.8614 [pdf]
    PLB(2015)·62 citations
  6. 06

    [Submitted on 30 Dec 2014] (cross-list from hep-ph)

    Constraints on Galactic Wino Densities from Gamma Ray Lines

    Matthew Baumgart🇺🇸 · Ira Z. Rothstein🇺🇸 · Varun Vaidya🇺🇸

    We systematically compute the annihilation rate for neutral winos into the final state gamma + X, including all leading radiative corrections. This includes both the Sommerfeld enhancement (in the decoupling limit for the Higgsino) and the resummation of the leading electroweak double logarithms. Adopting an analysis of the HESS experiment, we place constraints on the mass as a function of the wino fraction of the dark matter and the shape of the dark matter profile. We also determine how much coring is needed in the dark matter halo to make the wino a viable candidate as a function of its mass. Additionally, as part of our effective field theory formalism, we show that in the pure-Standard Model sector of our theory, emissions of soft Higgses are power-suppressed and that collinear Higgs emission does not contribute to leading double logs.

    Comments:
    32 pages, 10 figures; v2: inconsistency fixed between 2- and 4-component fermions, final results unchanged
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1412.8698 [pdf]
    JHEP(2015)·64 citations

Affiliations

first authorsco-authorsvia INSPIRE