Geometric actions for Lower Spin Gravity

A bstract We perform the Hamiltonian reduction of Lower Spin Gravity, the simplest bulk dual for a Warped Conformal Field Theory (WCFT), consisting in an SL(2) × U(1) Chern-Simons model. We identify the boundary action as the geometric action on coadjoint orbits of the Warped Virasoro group. We use this reduced action to compute one-loop contributions to the torus partition function and compare them to the Warped Virasoro characters.