Background independent action for double field theory

Understand

Double field theory describes a massless subsector of closed string theory with both momentum and winding excitations.

• The gauge algebra is governed by the Courant bracket in certain subsectors of this double field theory.
• We construct the associated nonlinear background-independent action that is T-duality invariant and realizes the Courant gauge algebra.
• The action is the sum of a standard action for gravity, antisymmetric tensor, and dilaton fields written with ordinary derivatives, a similar action for dual fields with dual derivatives, and a mixed term that is needed for gauge invariance.