Speaker
Description
There has been recently renewed interest in the quantisation of gravity by considering local subsystems on light-like hypersurfaces. In this talk, I will present a theory-independent framework that clarifies the common structure underlying these developments, assuming only standard quantum theory and general relativity.
The central idea is to describe local physics in terms of elementary light-like building blocks: three-dimensional null slabs bounded by past and future cuts. After briefly reviewing the timeless formulation of quantum theory, I will explain how to associate a kinematical Hilbert space to each null slab, with a natural factorization into bulk and corner degrees of freedom. Assuming the existence of appropriate vacuum states and a fundamental projector onto physical states, I will then show how local transition amplitudes can be constructed by gluing boundary data according to the causal structure of a diamond.
I will conclude by demonstrating that the resulting amplitudes satisfy Ward identities and charge conservation for the underlying symmetries, and by discussing how different approaches to quantum gravity may implement this framework in concrete settings.
