SPECIAL DATE - High Energy Theory Seminar

Bad metals are a class of materials whose transport properties cannot be understood within a weakly interacting quasiparticle description. Away from weak interactions, the natural objects to characterize are the conserved charge and heat current operators. This talk concerns two aspects of these operators. Firstly, many bad metals exhibit unexpectedly similar transport behavior. We suggest that this could be explained by a certain universal bound on charge and heat diffusivities. Secondly, the cuprate high temperature superconductors are especially important examples of bad metals. Transport in the most puzzling part of the cuprate phase diagram is characterized by multiple scaling laws. I will show that at least five of these scaling laws can be understood from only two nontrivial critical exponents. One of these is an anomalous dimension for the charge density operator.