Central Charge for AdS_2 Quantum Gravity

Understand

Two-dimensional Maxwell-dilaton quantum gravity on AdS_2 with radius $\ell$ and a constant electric field E is studied.

• In conformal gauge, this is equivalent to a CFT on a strip.
• In order to maintain consistent boundary conditions, the usual conformal diffeomorphisms must be accompanied by a certain U(1) gauge transformation.
• The resulting conformal transformations are generated by a twisted stress tensor, which has a central charge $c={3k E^2 \ell^4/4}$ where k is the level of the U(1) current.