Statistical Mechanics of Metals Without Quasiparticles, and of 
Charged Black Holes 

The very successful theory of metals is based upon a Boltzmann equation for electronic quasiparticles. But the “strange metals’ found in high temperature superconductors do not have well-defined quasiparticle excitations, which raises the problem of a theory of electrical transport in such metals. In their quantum theory of charged black holes, Gibbons and Hawking applied the Boltzmann-Gibbs ensemble to the Einstein-Maxwell theory, and obtained results for black hole entropy which did not have an evident interpretation in terms of the eigenstates of a quantum Hamiltonian. I will describe progress in resolving these long-standing problems in very different fields of physics using insights from the solvable Sachdev-Ye-Kitaev model of fermions with random interactions