Physical representations of corner symmetries

We give the full representation theory of the gravitational extended corner symmetry group in two dimensions. This includes projective representations, which correspond to representations of the quantum corner symmetry group. We find that they are described by one-dimensional conformal fields with an additional index in the Fock space of the harmonic oscillator. We begin with a review of Mackey’s theory of induced representations and then proceed to its application to the corner symmetries. The field representations, induced from the irreducible representations of the special linear group, are worked out first. The little group method is then applied to the extended corner symmetry group to obtain the irreducible unitary representations. Finally, we focus on projective representations and their application to the description of local subsystems. Published by the American Physical Society 2025