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Nuclear Theory·nucl-th

Tuesday·September 12, 2023

6 papers—2 primary·4 cross-listed

All6Primary2Cross-lists4
  1. 03

    [Submitted on 9 Sept 2023] (cross-list from astro-ph.HE)

    Anisotropic neutron star crust, solar system mountains, and gravitational waves

    J.A. Morales🇺🇸 · C. J. Horowitz🇺🇸

    "Mountains" or non-axisymmetric deformations of rotating neutron stars (NS) efficiently radiate gravitational waves (GW). We consider analogies between NS mountains and surface features of solar system bodies. Both NS and moons such as Europa or Enceladus have thin crusts over deep oceans while Mercury has a thin crust over a large metallic core. Thin sheets may wrinkle in universal ways. Europa has linear features, Enceladus has "Tiger" stripes, and Mercury has lobate scarps. NS may have analogous features. The innermost inner core of the Earth is anisotropic with a shear modulus that depends on direction. If NS crust material is also anisotropic this will produce an ellipticity, when the crust is stressed, that grows with spin frequency. This yields a braking index (log derivative of spin down rate assuming only GW spin down) very different from and could explain the maximum spin observed for neutron stars and a possible minimum ellipticity of millisecond pulsars.

    Comments:
    8 pages, 2 figures, Added finite element simulations that confirm results, PRD in press
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2309.04855 [pdf]
    PRD(2024)·12 citations
  2. 04

    [Submitted on 10 Sept 2023] (cross-list from hep-ph)

    An introduction to the parton and hadron cascade model PACIAE 3.0

    An-Ke Lei🇨🇳 · Yu-Liang Yan🇨🇳 · Dai-Mei Zhou🇨🇳 · Zhi-Lei She🇨🇳 · Liang Zheng🇨🇳 · Gao-Chan Yong🇨🇳 · Xiao-Mei Li🇨🇳 · Gang Chen🇨🇳 · Xu Cai🇨🇳 · Ben-Hao Sa🇨🇳

    We introduce a parton and hadron cascade model PACIAE 3.0 based on PYTHIA 6.428 and the PACIAE 2.2 program series. The simulation framework of C-, B-, and A-loops are designed for the high energy ( GeV) and low energy ( GeV) nuclear collisions, respectively, in PACIAE 3.0. In the C-loop simulation, the parton-parton inelastic scattering processes are added in the partonic rescattering process. The single string structure and multiple string interaction mechanism have been introduced investigating the strangeness enhancement in C- and B-loop. An improved mapping relation between the centrality percentage definition and the impact parameter definition is proposed responding the observation of fm from ALICE, ATLAS, and CMS collaborations. We have extensively modified the phenomenological coalescence hadronization model. The PACIAE 3.0 model simulated results of particle yield, transverse momentum distribution, and rapidity distribution well reproduce, respectively, the experimental data measured at FOPI, E895, RHIC, and LHC energies.

    Comments:
    15 pages, 15 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2309.05110 [pdf]
    PRC(2023)·21 citations
  3. 05

    [Submitted on 10 Sept 2023] (cross-list from cond-mat.stat-mech)

    The functional generalization of the Boltzmann-Vlasov equation and its Gauge-like symmetry

    Giorgio Torrieri🇧🇷

    We argue that one can model deviations from the ensemble average in non-equilibrium statistical mechanics by promoting the Boltzmann equation to an equation in terms of {\em functionals} , representing possible candidates for phase space distributions inferred from a finite observed number of degrees of freedom. We find that, provided the collision term and the Vlasov drift term are both included, a gauge-like redundancy arises which does not go away even if the functional is narrow. We argue that this effect is linked to the gauge-like symmetry found in relativistic hydrodynamics \cite{bdnk} and that it could be part of the explanation for the apparent fluid-like behavior in small systems in hadronic collisions and other strongly-coupled small systems\cite{zajc}. When causality is omitted this problem can be look at via random matrix theory show, and we show that in such a case thermalization happens much more quickly than the Boltzmann equation would infer. We also sketch an algorithm to study this problem numerically

    Comments:
    Discussion significantly extended and reorganized Accepted for publication, scipost Physics
    Subjects:
    Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2309.05154 [pdf]
    SciPost Phys.(2024)·4 citations
  4. 06

    [Submitted on 11 Sept 2023] (cross-list from hep-ph)

    Shear viscosity of rotating, hot, and dense spin-half fermionic systems from quantum field theory

    Sarthak Satapathy🇮🇳 · Rajeev Singh🇺🇸 · Pushpa Panday🇮🇳 · Salman Ahamad Khan🇮🇳 · Debarshi Dey🇮🇳

    In this study, we calculate the shear viscosity for rotating fermions with spin-half under conditions of high temperature and density. We employ the Kubo formalism, rooted in finite-temperature quantum field theory, to compute the field correlation functions essential for this evaluation. The one-loop diagram pertinent to shear viscosity is analyzed within the context of curved space, utilizing tetrad formalism as an effective approach in cylindrical coordinates. Our findings focus on extremely high angular velocities, ranging from 0.1 to 1 GeV, which align with experimental expectations. Furthermore, we explore the inter-relationship between the chemical potential and angular velocity within the scope of this study.

    Comments:
    14 pages, 4 figures. arXiv admin note: substantial text overlap with arXiv:2307.09953
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2309.05284 [pdf]
    2 citations

Affiliations

first authorsco-authorsvia INSPIRE