Violation of the KSS Bound in Holographic Bjorken-Flow

Abstract

In a system with a Bjorken-flow (BF), considering the inside of a BF as a subsystem for the reason explained in the body text, we compute entanglement entropy appearing in our side holographically . BF consists of many concentrically scattering quark-gluon plasmas created by colliding two masses of hadrons. Our BF is defined in the boundary space in an asymptoticly five-dimensional Anti de-Sitter space with a growing Schwartzshild black hole. %, where its Hawking temperature diminishes with time. In our analysis we can get a parameter prescribing our bulk space-time in terms of the boundary QCD's variables. Using this, we find that the $\eta/s$ dips from $1/4\pi$ just for a moment before asymptoting to $1/4\pi$ at infinitely large time. Since $1/4\pi$ is the KSS bound, this result is intriguing as an example of violation of the KSS bound.