Speaker
Description
In this work, we explore a Bemfica--Disconzi--Noronha--Kovtun (BDNK)-type formulation of relativistic magnetohydrodynamics, providing a causal and stable first-order description of dissipative fluids. We derive coupled evolution equations for the temperature and magnetic field in a boost-invariant Bjorken background, restricting to $(0+1)$D dynamics while retaining all relevant first-order gradients. By varying the transport coefficients, we disentangle the interplay and mutual backreaction between the thermal and electromagnetic sectors.
We find that, for comparable transport coefficients, the magnetic field is more sensitive to the temperature evolution than vice versa. We also examine the number density evolution, which is influenced by both temperature gradients and magnetic-field dynamics.
We further investigate dilepton production, where the magnetic field modifies the emission rate through the relaxation time in a kinetic-theory framework. Relative to the baseline case with vanishing expansion coefficients, nonzero first-order coupling coefficients significantly modify the low-mass dilepton spectrum. For the positive coefficients considered here, the dilepton yield is enhanced by a factor of approximately $3$--$5$, while negative coefficients lead to an overall suppression. Nevertheless, the central physical conclusion remains unchanged within the parameter range studied: coupling between temperature gradients and magnetic-field evolution accelerates the cooling of the medium, thereby reducing the dilepton yield compared to the case without this feedback. This qualitative behavior persists for both positive and negative expansion coefficients, although the overall yield depends on their values.
