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Nuclear Theory·nucl-th

Monday·April 1, 2024

3 papers—1 primary·2 cross-listed

All3Primary1Cross-lists2
  1. 02

    [Submitted on 28 Mar 2024] (cross-list from hep-th)

    Vortical waves in a quantum fluid with vector, axial, and helical charges. I. Non-dissipative transport

    Sergio Morales-Tejera🇷🇴 · Victor E. Ambruş🇷🇴 · Maxim N. Chernodub🇫🇷

    Due to the spin-orbit coupling, Dirac fermions, submerged in a thermal bath with finite macroscopic vorticity, exhibit a spin polarisation along the direction parallel to the vorticity vector . Due to the symmetries of the Lagrangian for free massless Dirac particles, there are three independent and classically conserved currents corresponding to the vector, axial, and helical charges. The constitutive relations for the charge currents and the stress-energy tensor at thermal equilibrium, derived in the framework of quantum field theory at finite temperature, reveal vorticity-induced contributions that deviate from the perfect fluid form. In this paper, we consider the mode structure of the corresponding hydrodynamical theory and derive collective excitations associated with coherent fluctuations of all three charges. We show that the chirally imbalanced rotating fluid should possess non-reciprocal gapless waves that propagate with different velocities along and opposite to the vorticity vector. We also uncover a strictly unidirectional mode, which we call the Axial Vortical Wave, propagating in the background of the axial charge density. The emergence of this wave can be traced back to earlier studies of vortical chiral fluids in a hydrodynamic approach. We also point out an unexpected instability in the limit of degenerate matter and discuss possible solutions when helicity and axial charge non-conservation are taken into account.

    Comments:
    36 pages, 6 figures, 1 table. Part 1
    Subjects:
    High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    2403.19755 [pdf]
    EPJC(2024)·3 citations
  2. 03

    [Submitted on 28 Mar 2024] (cross-list from hep-th)

    Vortical waves in a quantum fluid with vector, axial and helical charges. II. Dissipative effects

    Sergio Morales-Tejera🇷🇴 · Victor E. Ambruş🇷🇴 · Maxim N. Chernodub🇫🇷

    In this paper, we consider the effect of interactions on the local, average polarization of a quantum plasma of massless fermion particles characterized by vector, axial, and helical quantum numbers. Due to the helical and axial vortical effects, perturbations in the vector charge in a rotating plasma can lead to chiral and helical charge transfer along the direction of the vorticity vector. At the same time, interactions between the plasma constituents lead to the dissipation of the helical charge through helicity-violating pair annihilation (HVPA) processes and of the axial charge through the axial anomaly. We will discuss separately a QED-like plasma, in which we ignore background electromagnetic fields and thus the axial charge is approximately conserved, as well as a QCD-like plasma, where instanton effects lead to the violation of the axial charge conservation, even in the absence of background chromomagnetic fields. The non-conservation of helicity and chirality leads to a gapping of the Helical, Axial, and mixed Axial-Helical vortical waves that prevents their infrared modes from propagating. On the other hand, usual dissipative effects, such as charge diffusion, lead to significant damping of ultraviolet modes. We end this paper with a discussion of the regimes where these vortical waves may propagate.

    Comments:
    43 pages, 14 figures. Part 2
    Subjects:
    High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
    arXiv:
    2403.19756 [pdf]
    EPJC(2025)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE