Geometric construction of crystal bases for quantum generalized   Kac-Moody algebras
  We provide a geometric realization of the crystal $B(\infty)$ for quantum generalized Kac-Moody algebras in terms of the irreducible components of certain Lagrangian subvarieties in the representation spaces of a quiver. 
Seok-Jin Kang, Masaki Kashiwara, Olivier Schiffmann