1:30 pm
Analyticity and the Unruh effect.
The Unruh effect, which states that an accelerating observer experiences the Minkowski vacuum as a thermal bath, is a significant ingredient in understanding both black hole radiance and the entanglement structure of quantum field theory. In modern terms, the Unruh effect is the statement that the Minkowski vacuum restricted to a Rindler wedge has "local modular flow." I will begin with a big-picture explanation of local modular flow and why it is an important physical phenomenon, emphasizing how it shows up as a key ingredient in the proofs of the generalized second law and the averaged null energy condition. I will then explain new results that place tight, rigorous constraints on when local modular flow can arise. I will emphasize how the new results explain the empirical rarity of local modular flow, and speculate about how this rarity can be overcome in the near future to push modular flow to its limits as a tool for understanding quantum field theory. Based on 2309.16766 and 2403.18937.