Speaker
Description
While physically desirable, the extension of Functional Renormalization Group techniques to Lorentzian manifolds is technically challenging and is expected to lead to qualitatively new features. One of these features is the dependence on an underlying vacuum-like state, which I illustrate via Hadamard states in a perturbative expansion. For regulators that render the RHS of the flow equation finite, the ultraviolet aspects will by-and-large match those obtained in Euclidean signature through the standard heat kernel methodology. In contrast, the infrared aspects are state-dependent, technically difficult to extract, yet vital for the extrapolation of beta functions to small RG scales. We outline these features on cosmological spacetimes using a "spatial" regulator and so-called States of Low Energy.
