High Energy Theory Seminar

Many condensed matter experiments measure the transport properties of finite temperature many-body systems in the vicinity of a zero temperature quantum phase transition. Although there are often no well-defined particle-like excitations at such critical points, the transport exhibits a universal collisionless-to-hydrodynamic crossover at a characteristic frequency of order the temperature. I will describe exact computations of these crossovers in 2+1 dimensions using black hole solutions of M theory. Insights from these exact results generalize to a robust hydrodynamic description, which should apply to a wide class of quantum critical points, including the superfluid-insulator transition. I will show how such computations shed light on experiments on the cuprate high temperature superconductors.