PaperPanorama
FAQ

Nuclear Theory·nucl-th

Tuesday·April 27, 2021

14 papers—6 primary·8 cross-listed

All14Primary6Cross-lists8
  1. 01

    [Submitted on 23 Apr 2021]

    Glassy quantum nuclear pasta in neutron star crusts

    William G. Newton · Mark Alexander Kaltenborn · Sarah Cantu · Shuxi Wang · Amber Stinson · Jirina Rikovska Stone

    We investigate the nuclear pasta phases in neutron star crusts by conducting a large number of three-dimensional Hartree-Fock+BCS calculations at densities leading to the crust-core transition. We survey the shape parameter space of pasta at constant pressure. Spaghetti, waffles, lasagna, bi-continuous phases and cylindrical holes occupy local minima in the resulting Gibbs energy surfaces. The bi-continuous phase, in which both the neutron gas and nuclear matter extend continuously in all dimensions and therefore protons are delocalized, appears over a large range of depths. Our results support the idea that nuclear pasta is a glassy system. Multiple pasta configurations coexist in a given layer of the crust. At a characteristic temperature, of order -K, different phases become frozen into domains whose sizes we estimate to be 1-50 times the lattice spacing and over which the local density and electron fraction can vary. Above this temperature, there is very little long-range order and matter is an amorphous solid. Electron scattering off domain boundaries may contribute to the disorder resistivity of the pasta phases. Annealing of the domains may occur during cooling; repopulating of local minima during crustal heating might lead to temperature dependent transport properties in the deep layers of the crust. We identify 4 distinct regions: (1) nuclear pasta first appears as a local minima, but spherical nuclei are the ground state; (2) nuclear pasta become the absolute minimum, but spherical nuclei are still a local minimum (3) only nuclear pasta appears in local minima, and protons are still localized in at least one dimension (4) only pasta appears, and protons are delocalized. The whole pasta region can occupy up to 70% of the crust by mass and 40% by thickness, and the layer in which protons are delocalized could occupy 45% of the crust mass and 25% of its thickness.

    Comments:
    32 pages, 23 figures, submitted to Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    2104.11835 [pdf]
    PRC(2022)·37 citations
  2. 02

    [Submitted on 25 Apr 2021]

    Symmetry energy extracted from the SRIT pion data in Sn+Sn systems

    Gao-Chan Yong🇨🇳

    With the improved particular Isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model (impIBUU) including the nucleon-nucleon short-range correlations, the ratios and yields of and in Sn+Sn systems with different asymmetries at 270 MeV/nucleon are studied. It is found that the yields of and and their ratios in Sn+Sn systems characterized by different neutron to proton ratios obtained from the very recent SRIT pion data, are quite well described by the model, especially when a soft symmetry energy with = 66.7524.75 MeV is used. The calculations also clearly demonstrate that the high-momentum tail of the nucleon initialization in momentum space strongly affects the yields and ratios of pion production in Sn+Sn systems with different asymmetries near or below threshold. In addition, given many insoluble theoretical uncertainties in transport models, multi-system experimental measurements with various N/Z asymmetries are proposed to extract the symmetry energy less model-dependently by using heavy-ion collisions.

    Comments:
    6 pages, 4 figures, PRC in production
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2104.12098 [pdf]
    PRC(2021)·24 citations
  3. 03

    [Submitted on 25 Apr 2021]

    Relativistic resistive dissipative magnetohydrodynamics from the relaxation time approximation

    Ankit Kumar Panda🇮🇳 · Ashutosh Dash🇮🇳 · Rajesh Biswas🇮🇳 · Victor Roy🇮🇳

    Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution equations using the Boltzmann equation, thus extending our work from the previous paper \href{https://link.springer.com/article/10.1007/JHEP03(2021)216}{JHEP 03 (2021) 216} where we considered the non-resistive limit. We solve the Boltzmann equation for a system of particles and antiparticles using the relaxation time approximation and the Chapman-Enskog like gradient expansion for the off-equilibrium distribution function, truncating beyond second-order. In the first order, the bulk and shear stress are independent of the electromagnetic field, however, the diffusion current, shows a dependence on the electric field. In the first order, the transport coefficients~(shear and bulk stress) are shown to be independent of the electromagnetic field. The diffusion current, however, shows a dependence on the electric field. In the second-order, the new transport coefficients that couple electromagnetic field with the dissipative quantities appear, which are different from those obtained in the 14-moment approximation~\cite{Denicol:2019iyh} in the presence of the electromagnetic field. Also we found out the various components of conductivity in this case.

    Comments:
    11 pages, 0 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    2104.12179 [pdf]
    PRD(2021)·40 citations
  4. 04

    [Submitted on 25 Apr 2021]

    Mapping Dirac--Hartree--Fock approach onto relativistic mean field model

    S. Gmuca🇸🇰 · K. Petrik🇸🇰 · J. Leja🇸🇰

    The exchange part of energy density of the linear Dirac--Hartree--Fock (DHF) model in symmetric nuclear matter is evaluated in a parameter--free closed form and expressed as density functional. After the rearranging terms the relativistic mean-field approach with density-dependent couplings may be recovered with density dependence coming from the Fock exchange. The formalism developed, is then extended to the nonlinear DHF approximation with field self-couplings allowed. The nonlinear self--interactions result in essential density dependence (medium modification) of effective couplings that are decoupled from the Fock ones.

    Comments:
    14 pages
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2104.12246 [pdf]
    0 citations
  5. 05

    [Submitted on 26 Apr 2021]

    From nuclei to neutron stars: simple binding energy computer modelling in the classroom (part 2)

    A. Rios · A. Pastore · C. Diget · A. M. Romero · K. Leech · P. Stokoe

    We introduce two simple online activities to explore the physics of neutron stars. These provide an introduction to the basic properties of compact objects, like their masses and radii, for secondary school students. The first activity explores the idea of the minimum mass of a neutron star. It is directly linked to the concept of binding energy and follows on from our previous activities. The second activity focuses on the maximum mass of neutron stars using a solvable model of the neutron star interior. The activities are based on spreadsheets, provided as Supplementary Material, and can be easily adapted to different levels, age groups and discussion topics. In particular, these activities can naturally lead towards discussions on extrapolations and limits of theoretical models.

    Comments:
    This submission is a follow-up of Part 1 in arXiv:2007.06872, published as A Pastore et al 2021 Phys. Educ. 56 035012 in https://doi.org/10.1088/1361-6552/abe09d. Worksheet attached in Excel file
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); physics.ed-ph (physics.ed-ph)
    arXiv:
    2104.12449 [pdf]
    0 citations
  6. 06

    [Submitted on 26 Apr 2021]

    Hydrodynamic Attractor in a Hubble Expansion

    Zhiwei Du🇨🇳 · Xu-Guang Huang🇨🇳 · Hidetoshi Taya🇯🇵

    We analytically investigate hydrodynamic attractor solutions in both Müller-Israel-Stewart (MIS) and kinetic theories in a viscous fluid system undergoing a Hubble expansion with a fixed expansion rate. We show that the gradient expansion for the MIS theory and the Chapman-Enskog expansion for the Boltzmann equation within the relaxation time approximation are factorially divergent and obtain hydrodynamic attractor solutions by applying the Borel resummation technique to those asymptotic divergent series. In both theories, we find that the hydrodynamic attractor solutions are globally attractive and only the first-order non-hydrodynamic mode exists. We also find that the hydrodynamic attractor solutions in the two theories disagree with each other when gradients become large, and that the speed of the attraction is different. Similarities and differences from hydrodynamic attractors in the Bjorken and Gubser flows are also discussed. Our results push the idea of far-from-equilibrium hydrodynamics in systems undergoing a Hubble expansion.

    Comments:
    12 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    2104.12534 [pdf]
    PRD(2021)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE