I will outline a general framework, based on the covariant phase space formalism, allowing to realize gauge and gravitational edge modes as dynamical reference frames, an often suggested interpretation that can be made entirely explicit. On top of clarifying the operational meaning of edge modes, this construction leads to a principled derivation of their (pre)symplectic structure, and more generally, of boundary actions governing their dynamics.
Including such degrees of freedom into the description of a bounded region allows to cleanly distinguish two types of transformations that have non-trivial support on the boundary: 1) boundary symmetries, which affect relational observables relating the region of interest to its complement, and 2) gauge transformations, which do not. Furthermore, as will be illustrated in example gauge theories, the physical relevance of boundary symmetries remains contingent on the type of boundary conditions being considered, and as a result, is also theory-dependent.
Based on arxiv.org/abs/2109.06184, in collaboration with Philipp Höhn, and work in progress together with Philipp Höhn and Stefan Eccles.