  We establish restrictions on Lagrangian embeddings of rational homology
spheres into certain open symplectic manifolds, namely the (A_m) Milnor fibres
of odd complex dimension. This relies on general considerations about
equivariant objects in module categories (which may be applicable in other
situations as well), as well as results of Ishii-Uehara and Ishii-Ueda-Uehara
concerning the derived categories of coherent sheaves on the resolutions of
(A_m) surface singularities.
