Stability of Affine G-varieties and Irreducibility in Reductive Groups

Abstract

Let $G$ be a reductive affine algebraic group, and let $X$ be an affine algebraic $G$-variety. We establish a (poly)stability criterion for points $x\in X$ in terms of intrinsically defined closed subgroups $H_x$ of $G$, and relate it with the numerical criterion of Mumford, and with Richardson and Bate-Martin-Röhrle criteria, in the case $X=G^N$. Our criterion builds on a close analogue of a theorem of Mundet and Schmitt on polystability and allows the generalization to the algebraic group setting of results of Johnson-Millson and Sikora about complex representation varieties of finitely presented groups. By well established results, it also provides a restatement of the non-abelian Hodge theorem in terms of stability notions.

29 pages. To appear in Int. J. Math. Note: this version 4 is identical with version 2 (version 3 is empty)

Cited by in corpus (2)

• Topology of character varieties of Abelian groups
• Principal Schottky Bundles over Riemann surfaces