In this talk I will describe my work characterizing
quantum entanglement in systems with a Fermi surface. This class includes everything from Fermi
liquids to exotic spin liquids in frustrated magnets and perhaps even
holographic systems. I review my
original scaling argument and then describe in detail a number of new precise
results on entanglement in Fermi liquids.
I will also discuss recent quantum Monte Carlo calculations of Renyi
entropies and will argue that we now have a rather complete agreement between
theory and numerics for Fermi liquid entanglement. I will also discuss universal crossovers
between thermal and entanglement entropy and a class of solvable interacting
models where we can prove the universality of the Widom formula for Fermi
surface entanglement. If there is time,
I will comment on several other topics including fluctuations of conserved
quantities and connections to holography.