Iso-$\mu/T$ holographic entropy and its attractor for a strongly coupled quantum fluid

Abstract

Numerical evidence has shown that a period of vanishing entropy production during far-from-equilibrium stages induces subsequent violations of the dominant energy condition in strongly coupled plasmas. This behavior also appears to hold for a Bjorken-expanding, hot and dense strongly coupled quantum fluid. In this context, it has been established that the chemical potential-to-temperature ratio ($\mu/T$) in the medium increases with higher initial charge density, $\rho_0$, and/or lower initial energy density, $\varepsilon_0$. Here, we present a numerical method to evolve Bjorken R-charged plasmas by varying $(\varepsilon_0,\rho_0)$ in order to generate a curve that preserves a constant $\mu/T$. This allows us to address the case in which all Bekenstein-Hawking entropy densities evolve towards configurations with the same $\mu/T$. This approach enables a more direct comparison with the $\mathcal{N}=4$ SYM plasma case ($\mu/T=0$) and, consequently, provides clearer evidence of the correlation between entropy production and violations of the dominant energy condition. Moreover, this procedure offers a characterization (albeit numerical and partial) of the iso$-\mu/T$ entropy density hydrodynamic attractor for hot and dense strongly coupled quantum fluids.