Semi-invariants of symmetric quivers of finite type
arXiv:0910.1070 · doi:10.1007/s10468-012-9346-2
Abstract
Let be a symmetric quiver, where is a finite quiver without oriented cycles and is a contravariant involution on . The involution allows us to define a nondegenerate bilinear form on a representation of . We shall call the representation orthogonal if is symmetric and symplectic if is skew-symmetric. Moreover we can define an action of products of classical groups on the space of orthogonal representations and on the space of symplectic representations. For symmetric quivers of finite type, we prove that the rings of semi-invariants for this action are spanned by the semi-invariants of determinantal type and, in the case when matrix defining is skew-symmetric, by the Pfaffians .