Fine Structure of Jackiw-Teitelboim Quantum Gravity

We investigate structural aspects of JT gravity through its BF description. In particular, we provide evidence that JT gravity should be thought of as (a coset of) the noncompact subsemigroup SL$^+$(2,R) BF theory. We highlight physical implications, including the famous sinh Plancherel measure. Exploiting this perspective, we investigate JT gravity on more generic manifolds with emphasis on the edge degrees of freedom on entangling surfaces and factorization. It is found that the one-sided JT gravity degrees of freedom are described not just by a Schwarzian on the asymptotic boundary, but also include frozen SL$^+$(2,R) degrees of freedom on the horizon, identifiable as JT gravity black hole states. Configurations with two asymptotic boundaries are linked to 2d Liouville CFT on the torus surface.
Comment: 37 pages + appendices, v3: added extensive discussion on the gluing measure (comparing with the recent work of Saad-Shenker-Stanford), clarified discussion on factorization and explicit volume factors, and added evidence from hyperbolic geometry, added references, matches published version