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Nuclear Theory·nucl-th

Friday·September 16, 2022

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    [Submitted on 14 Sept 2022]

    Polarization in heavy ion collisions: a theoretical review

    Matteo Buzzegoli🇺🇸

    In these proceedings I discuss the recent progress in the theory of spin polarization in relativistic fluids. To date, a number of studies have begun to examine the impact of the shear tensor on the local spin polarization and whether this contribution can restore agreement between the measurements and the predictions obtained from a polarization induced by the gradients of the plasma. I present the derivation of the spin polarization vector of a fermion at local thermal equilibrium and I discuss the role of pseudo-gauge transformations and of dissipative effects. I list what we can learn from the polarization measured at lower energies. Finally, I discuss possible applications of spin polarization measurements in relativistic heavy ion collisions.

    Comments:
    9 pages. Presented at the 20th International Conference on Strangeness in Quark Matter (SQM 2022)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2209.06879 [pdf]
    EPJ Web Conf.(2023)·3 citations
  2. 02

    [Submitted on 14 Sept 2022]

    Spurious dipole mode in random-phase approximation and in the RPA-based models

    V. Tselyaev

    The problems related to the existence of the spurious dipole mode (SDM) in the self-consistent nuclear-structure models are considered. A method is formulated that allows to eliminate coupling of the SDM with the physical modes in the extended random-phase approximation (ERPA) theories, in particular, in the time blocking approximation (TBA) which is the model of the ERPA type. It is shown that the application of this method in the realistic TBA calculations of the excitations gives the results which are very close to the results of the TBA calculations without using this method if the bare external-field operators are replaced by the effective ones.

    Comments:
    14 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2209.06935 [pdf]
    PRC(2022)·1 citation
  3. 03

    [Submitted on 15 Sept 2022]

    Intermittency of charged particles in the hybrid UrQMD+CMC model at energies available at the BNL Relativistic Heavy Ion Collider

    Jin Wu🇨🇳 · Zhiming Li🇨🇳 · Xiaofeng Luo🇨🇳 · Mingmei Xu🇨🇳 · Yuanfang Wu🇨🇳

    Within the framework of intermittency analysis, a search for critical fluctuations is ongoing to locate the possible critical point in the quantum chromodynamics phase diagram. In this study, self-similar critical fluctuations from a critical Monte Carlo (CMC) model have been incorporated into the cascade ultrarelativistic quantum molecular dynamics (UrQMD) model. This hybrid UrQMD+CMC model exhibits a clear power-law behavior of scaled factorial moment for charged particles in Au+Au collisions at = 7.7-200 GeV. By comparing the UrQMD+CMC model results with those from the STAR experiment, it is found that the value of a calculated scaling exponent falls in the range of the experimental measurement when 1-2 \% signal of intermittency fluctuations is added into the UrQMD sample.

    Comments:
    8 pages, 6 figures, published version
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2209.07135 [pdf]
    PRC(2022)·10 citations
  4. 04

    [Submitted on 15 Sept 2022]

    Proximity effects of vortices in neutron superfluids in neutron stars: Vortex core transitions and covalent bonding of vortex molecules

    Michikazu Kobayashi🇯🇵 · Muneto Nitta🇯🇵

    Neutron superfluids consisting of neutron pairs with the total angular momentum with spin-triplet and -wave are believed to be realized in neutron star cores. Within the Ginzburg-Landau theory it was previously found that a singly quantized vortex is split into two half-quantized non-Abelian vortices connected by one (or three) soliton(s) forming a vortex molecule with the soliton bond(s), in the absence (presence) of magnetic field parallel to them. In this paper, we investigate proximity effects of two vortex molecules by exhausting all possible two vortex molecule states consisting of four half-quantized vortices and determining the phase diagram spanned by the magnetic field and rotation speed. As the rotation speed is increased, the distance between the two vortex molecules becomes shorter. In the magnetic field below the critical value, we find that as the rotation speed is increased, the two separated vortex molecules transit to a dimerized vortex molecule, where the two vortex molecules are bridged by two solitons that we call "covalent bonds" in analogy with chemical molecules. We also find that the orders of the constituent half-quantized vortex cores transit from a ferromagnetic order to a cyclic order as the vortex molecules come closer. On the other hand, no dimerization occurs in the magnetic field above the critical value. Instead, we find a transition for the polarization direction of the vortex molecules from a configuration parallel to the separation to one perpendicular to the separation as they come closer. We also show some examples of three and four vortex molecule states.

    Comments:
    16 pages, 12 figures. Continuing project to arXiv:2203.09300
    Subjects:
    Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
    arXiv:
    2209.07205 [pdf]
    PRC(2023)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE