ICTS

In the past years there has been renewed interest in identifying bounds, originating from quantum mechanics, on various quantities such as transport coefficients, including conductivity and viscosity. These remain elusive, but a “bound to chaos,” limiting the value of a Lyapunov exponent, was derived by Maldacena, Shenker, and Stanford. The reason this result has generated so much interest in field theory is that Black Holes are expected to saturate these bounds; conversely, any model that does so is a potential toy model for a Black Hole. The MSS derivation is not difficult, but it can be made even simpler by recasting it in a way that shows that the bound follows directly from the fluctuation–dissipation (KMS) relation, fundamental in statistical mechanics.