Exact Semiclassical Gravity and Partial Cauchy Slice Holography

This talk has two parts. In the first, I will discuss a well-known Lorentzian axiomatic framework in which quantum gravity theorems can be rigorously established, with the quantum extremal surface prescription as a central highlight. I will describe a recently sharpened understanding of its regime of validity—namely the limit $G\to0$ with cG held fixed, where c counts the number of matter species. Exactness in cG allows the framework to reach non-perturbatively beyond Einstein gravity. To exemplify its power, I will explain constraints on possible singularity-resolution scenarios, presenting two explicit geometric solutions: one in which the singularity resolves and one in which it does not. In the second part, I will discuss preliminary work on a “holographic” encoding of Lorentzian subregions via the gravitational path integral. As an example, I will present a computation of black hole entropy obtained directly from bulk partial Cauchy-slice preparations in the Lorentzian sector. I will explain potential applications of this approach.