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HK: Fachverband Physik der Hadronen und Kerne

HK 48: Heavy-Ion Collisions and QCD Phases XII

HK 48.3: Talk

Wednesday, March 13, 2024, 18:00–18:15, HBR 14: HS 1

On the validity of Ohm's law in relativistic plasmas — •Ashutosh Dash, Masoud Shokri, Luciano Rezzolla, and Dirk Rischke — Goethe university, Institute for theoretical physics, 60438 Frankfurt am Main

Relativistic plasmas play a significant role in high-energy phenomena, including heavy-ion collisions, black-hole magnetospheres, relativistic jets, and the early universe. The coarse-grained framework for describing the motion of charged fluid is known as relativistic magnetohydrodynamics (MHD). The MHD equations, which comprise the particle conservation law, the energy/momentum conservation laws, and Maxwell*s equations, must also be complemented by Ohm*s law. The usual Navier-Stokes form of Ohm's law is acausal and needs to be replaced with an evolution equation of the charge diffusion current with a finite relaxation time, which ensures causality and stability.

This, in turn, leads to transient effects in the charge-diffusion current, the nature of which depends on the particular values of electrical conductivity and the charge-diffusion relaxation time. We will investigate in a simplified 1+1-dimensional setting in the context of heavy-ion collision, where matter and electromagnetic fields are assumed to be transversely homogeneous and are initially expanding according to a Björken scaling. We will see how the scale invariance is broken by the ensuing self-consistent dynamics of matter and electromagnetic fields. Implications of these findings on the recent measurement of charged particle directed flow by the STAR experiment will also be discussed.

Keywords: MHD; Causality; Ohm's law; Björken expansion; Numerical hydrodynamics