In the past few years. there has been considerable activity around a set of quantum bounds on transport coefficients (viscosity) and chaos (Lyapunov exponent). relevant at low temperatures. The interest comes from the fact that Black-Hole models seem to saturate all of them. https://www.jmannino.com/quick-offer-Viqua-F4-50-Plus-Monitored-UV-System-Powered-by-UVMax-15-gpm-230-Volt-on-sale/