  We prove the Arnold-Givental conjecture for a class of Lagrangian
submanifolds in Marsden-Weinstein quotients which are fixpoint sets of some
antisymplectic involution. For these Lagrangians the Floer homology cannot in
general be defined by standard means due to the bubbling phenomenon. To
overcome this difficulty we consider moment Floer homology whose boundary
operator is defined by counting solutions of the symplectic vortex equations on
the strip which have better compactness properties than the original Floer
equations.
