Quiver concomitants are often reflexive Azumaya. (English) Zbl 0675.16015
Let Q be a finite oriented graph with vertices 1,...,n. Given \(d=(d_ 1,...,d_ n)\in N^ n\) and an algebraically closed field K of characteristic zero the set \({\mathcal R}(Q,d)\) of all K-representations of Q of dimension type d is the affine variety \(\prod_{\gamma: i\to j}K_{\gamma}^{d_ id_ j}\), where \(K_{\gamma}^{d_ id_ j}=K^{d_ id_ j}\) and \(\gamma\) : \(i\to j\) runs through all arrows in Q. The group \(Gl(d)=\prod^{n}_{i=1}Gl(d_ i,K)\) acts naturally on \({\mathcal R}(Q,d)\). The ring T[Q,d] of all polynomial maps \({\mathcal R}(Q,d)\to M_ t(K)\), \(t=d_ 1+...+d_ n\), which commute with the actions of Gl(d) is called the ring of quiver concomitants. Here Gl(d) acts on the matrix algebra \(M_ t(K)\) by conjugation. T[Q,d] is an affine Noetherian PI-ring. Under the assumption that the Ringel bilinear form of Q is symmetric and that d is a root from the fundamental chamber of Q such that \(d_ 1,...,d_ n\geq 2\) it is proved that T[Q,d] is a reflexive Azumaya R-order in a central simple algebra over the field of fractions of a normal domain R, except for three low dimensional anormalities. In particular T[Q,d] is a maximal order.
Reviewer: D.Simson
MSC:
16Gxx | Representation theory of associative rings and algebras |
16H05 | Separable algebras (e.g., quaternion algebras, Azumaya algebras, etc.) |
15A72 | Vector and tensor algebra, theory of invariants |
20G15 | Linear algebraic groups over arbitrary fields |
14F22 | Brauer groups of schemes |
14M20 | Rational and unirational varieties |