The probe limit in MHD and its implications for magnetic transport

Fuente: arXiv
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Auteurs principaux: Frangi, Giorgio, Bajec, Matej, Buza, Guri K., Soloviev, Alexander, Grozdanov, Sašo
Format: Preprint
Publié: 2025
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author Frangi, Giorgio
Bajec, Matej
Buza, Guri K.
Soloviev, Alexander
Grozdanov, Sašo
author_facet Frangi, Giorgio
Bajec, Matej
Buza, Guri K.
Soloviev, Alexander
Grozdanov, Sašo
contents Many phenomenological and effective field-theoretical (EFT) applications of magnetohydrodynamics (MHD) in the presence of a background magnetic field employ a simplifying assumption whereby the electromagnetic and the energy-momentum fluctuations decouple. In studies of magnetic transport, for example in magnetic diffusion, the conservation of energy and momentum is then neglected. In this paper, we investigate the details and the consistency of this so-called $\textit{probe limit}$ in different parametric regimes of MHD plasmas. In the first part of the paper, our discussion explores the hydrodynamic (higher-form) theory of MHD. In the second part, we then explicitly test the probe limit by using a microscopic holographic (AdS/CFT) model of a strongly coupled plasma. In the process, we develop the holographic Schwinger-Keldysh EFT prescription for describing the bulk 2-form fields and their dual 1-form symmetries. Moreover, we find evidence of a phase transition at low temperatures and show that magnetic Hall transport can emerge as a consequence of background charge density that breaks the charge conjugation symmetry of the state. Finally, we discuss the implications for magnetic transport, with a particular view towards the dynamics of dense nuclear matter in neutron stars.
format Preprint
id arxiv_https___arxiv_org_abs_2510_12352
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The probe limit in MHD and its implications for magnetic transport
Frangi, Giorgio
Bajec, Matej
Buza, Guri K.
Soloviev, Alexander
Grozdanov, Sašo
High Energy Physics - Theory
High Energy Astrophysical Phenomena
Nuclear Theory
Many phenomenological and effective field-theoretical (EFT) applications of magnetohydrodynamics (MHD) in the presence of a background magnetic field employ a simplifying assumption whereby the electromagnetic and the energy-momentum fluctuations decouple. In studies of magnetic transport, for example in magnetic diffusion, the conservation of energy and momentum is then neglected. In this paper, we investigate the details and the consistency of this so-called $\textit{probe limit}$ in different parametric regimes of MHD plasmas. In the first part of the paper, our discussion explores the hydrodynamic (higher-form) theory of MHD. In the second part, we then explicitly test the probe limit by using a microscopic holographic (AdS/CFT) model of a strongly coupled plasma. In the process, we develop the holographic Schwinger-Keldysh EFT prescription for describing the bulk 2-form fields and their dual 1-form symmetries. Moreover, we find evidence of a phase transition at low temperatures and show that magnetic Hall transport can emerge as a consequence of background charge density that breaks the charge conjugation symmetry of the state. Finally, we discuss the implications for magnetic transport, with a particular view towards the dynamics of dense nuclear matter in neutron stars.
title The probe limit in MHD and its implications for magnetic transport
topic High Energy Physics - Theory
High Energy Astrophysical Phenomena
Nuclear Theory
url https://arxiv.org/abs/2510.12352