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Nuclear Theory·nucl-th

Thursday·August 25, 2022

4 papers—1 primary·3 cross-listed

All4Primary1Cross-lists3
  1. 02

    [Submitted on 24 Aug 2022] (cross-list from astro-ph.HE)

    Vortex Pinning in Neutron Stars, Slip-stick Dynamics, and the Origin of Spin Glitches

    Bennett Link · Yuri Levin

    We study pinning and unpinning of superfluid vortices in the inner crust of a neutron star using 3-dimensional dynamical simulations. Strong pinning occurs for certain lattice orientations of an idealized, body-centered cubic lattice, and occurs generally in an amorphous or impure nuclear lattice. The pinning force per unit length is dyn cm for a vortex-nucleus interaction that is repulsive, and dyn cm for an attractive interaction. The pinning force is strong enough to account for observed spin jumps (glitches). Vortices forced through the lattice move with a slip-stick character; for a range of superfluid velocities, the vortex can be in either a cold, pinned state or a hot unpinned state, with strong excitation of Kelvin waves on the vortex. This two-state nature of vortex motion sets the stage for large-scale vortex movement that creates an observable spin glitch. We argue that the vortex array is likely to become tangled as a result of repeated unpinnings and repinnings. We conjecture that during a glitch, the Kelvin-wave excitation spreads rapidly along the direction of the mean superfluid vorticity and slower in the direction perpendicular to it, akin to an anisotropic deflagration.

    Comments:
    12 pages, 7 figures (two animations)
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); cond-mat.other (cond-mat.other); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
    arXiv:
    2208.11494 [pdf]
    ApJ(2022)·21 citations
  2. 03

    [Submitted on 23 Aug 2022] (cross-list from astro-ph.HE)

    Explosion of a Minimum-Mass Neutron Star within Relativistic Hydrodynamics

    A.V. Yudin

    The relativistic hydrodynamics equations are adapted for the spherically symmetric case and the Lagrangian form. They are used to model the explosive disruption of a minimum-mass neutron star: a key ingredient of the stripping model for short gamma-ray bursts. The shock breakout from the neutron star surface accompanied by the acceleration of matter to ultrarelativistic velocities is studied. A comparison with the results of previously published nonrelativistic calculations is made.

    Comments:
    17 pages, 5 figs
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2208.11514 [pdf]
    Astron.Lett.(2022)·9 citations
  3. 04

    [Submitted on 24 Aug 2022] (cross-list from quant-ph)

    Symmetry breaking/symmetry preserving circuits and symmetry restoration on quantum computers: A quantum many-body perspective

    Denis Lacroix🇫🇷 · Edgar Andres Ruiz Guzman🇫🇷 · Pooja Siwach🇺🇸

    We discuss here some aspects related to the symmetries of a quantum many-body problem when trying to treat it on a quantum computer. Several features related to symmetry conservation, symmetry breaking, and possible symmetry restoration are reviewed. After briefly discussing some of the standard symmetries relevant for many-particle systems, we discuss the advantage of encoding some symmetries directly in quantum ansätze, especially to reduce the quantum register size. It is, however, well-known that the use of symmetry-breaking states can also be a unique way to incorporate specific internal correlations when a spontaneous symmetry breaking occurs. These aspects are discussed in the quantum computing context. Ultimately, an accurate description of quantum systems can be achieved only when the initially broken symmetries are properly restored. We review several methods explored previously to perform symmetry restoration on a quantum computer, for instance, the ones based on symmetry filtering by quantum phase estimation and by an iterative independent set of Hadamard tests. We propose novel methods that pave the new directions to perform symmetry restoration, like those based on the purification of the state employing the linear combination of unitaries (LCU) approach.

    Comments:
    Revides version, submitted to Eur. Phys. J. A in the topical issue on "Quantum computing in low-energy nuclear theory"
    Subjects:
    Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
    arXiv:
    2208.11567 [pdf]
    EPJA(2023)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE