Dual diffeomorphisms and finite distance asymptotic symmetries in 3d gravity

Understand

We study the finite distance boundary symmetry current algebra of the most general first order theory of 3d gravity.

• We show that the space of quadratic generators contains diffeomorphisms but also a notion of dual diffeomorphisms, which together form either a double Witt or centreless BMS$_3$ algebra.
• The relationship with the usual asymptotic symmetry algebra relies on a duality between the null and angular directions, which is possible thanks to the existence of the dual diffeomorphisms.