On singularities of quiver moduli
arXiv:0903.4139
Abstract
Any moduli space of representations of a quiver (possibly with oriented cycles) has an embedding as a dense open subvariety into a moduli space of representations of a bipartite quiver having the same type of singularities. A connected quiver is Dynkin or extended Dynkin if and only if all moduli spaces of its representations are smooth.
a known side result removed, a reference added, minor changes in exposition