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Nuclear Theory·nucl-th

Thursday·May 13, 2021

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 05

    [Submitted on 11 May 2021] (cross-list from hep-ph)

    Neutron star structure with a new force between quarks

    Jeffrey M. Berryman🇺🇸 · Susan Gardner🇺🇸

    The discovery of nondiffuse sources of gravitational waves through compact-object mergers opens new prospects for the study of physics beyond the Standard Model. In this paper, we study the effects of a new force between quarks, suggested by the gauging of baryon number, on pure neutron matter at supranuclear densities. This leads to a stiffening of the equation of state, allowing neutron stars to be both larger and heavier and possibly accommodating the light progenitor of GW190814 as a neutron star. The role of conventional three-body forces in neutron star structure is still poorly understood, though they can act in a similar way, implying that the mass and radius do not in themselves resolve whether new physics is coming into play. However, a crucial feature of the scenario we propose is that the regions of the new physics parameter space that induce observable changes to neutron star structure are testable at low-energy accelerator facilities. This testability distinguishes our scenario from other classes of new phenomena in dense matter.

    Comments:
    9 pages, 3 figures; updated to match journal version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2105.05254 [pdf]
    PRC(2021)·11 citations
  2. 06

    [Submitted on 11 May 2021] (cross-list from cond-mat.quant-gas)

    Dissipative superfluid hydrodynamics for the unitary Fermi gas

    Jiaxun Hou🇺🇸 · Thomas Schaefer🇺🇸

    In this work we establish constraints on the temperature dependence of the shear viscosity in the superfluid phase of a dilute Fermi gas in the unitary limit. Our results are based on analyzing experiments that measure the aspect ratio of a deformed cloud after release from an optical trap. We discuss how to apply the two-fluid formalism to the unitary gas, and provide a suitable parametrization of the equation of state. We show that in expansion experiments the difference between the normal and superfluid velocities remains small, and can be treated as a perturbation. We find that expansion experiments favor a shear viscosity that decreases significantly in the superfluid regime. Using an exponential parametrization we find , where is the critical temperature, is the local Fermi temperature of the gas.

    Comments:
    30 pages, 11 figures. To appear in Phys Rev A
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
    arXiv:
    2105.05284 [pdf]
    PRA(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE