Subir Sachdev
Herchel Smith Professor of Physics, Harvard University
Guest speaker invited by the Collège de France assemblyat the suggestion of Pr Antoine Georges.
My lectures will begin by reviewing the Gibbons-Hawking theory of the quantum thermodynamics of charged black holes in Einstein gravity. I will describe recent progress in computing the semiclassical corrections to this theory at low temperatures, which are obtained using a theory of time reparameterizations controlled by a Schwarzian action. Then I will turn to the Sachdev-Ye-Kitaev model of fermions with random interactions: remarkably, the low temperature properties of this model are also described by the same theory of time reparameterizations. Finally, I will turn to the theory of strange metals obtained by coupling a two-dimensional Fermi surface to gapless scalars: a SYK-style strong coupling theory shows that this strange metal has linear-in-temperature resistivity from spatially random fluctuations in the Yukawa couplings between the fermions and the scalars.