Quotients by actions of the derived group of a maximal unipotent subgroup

Actions of the Derived Group of a Maximal Unipotent Subgroup on G-varieties

The ground field k is algebraically closed and of characteristic zero. Let G be a semisimple simply-connected algebraic group over k and U a maximal unipotent subgroup of G. One of the fundamental invariant-theoretic facts, which goes back to Hadžiev [9], is that k[G/U ] is a finitely generated k-algebra and regarded as G-module it contains every finite-dimensional simple G-module exactly once....

Quotients by Reductive Group, Borel Subgroup, Unipotent Group and Maximal Torus

Consider an algebraic action of a connected complex reductive algebraic group on a complex polarized projective variety. In this paper, we first introduce the nilpotent quotient, the quotient of the polarized projective variety by a maximal unipotent subgroup. Then, we introduce and investigate three induced actions: one by the reductive group, one by a Borel subgroup, and one by a maximal toru...

Geometric Quotients of Unipotent Group Actions

This article is devoted to the problem of constructing geometric quotients of a quasiaffine scheme X over a field of characteristic 0 by a unipotent algebraic group G. This problem arises naturally if one tries to construct moduli spaces in the sense of Mumford's 'geometric invariant theory' for singularities of algebraic varieties or for modules over the local ring of such a singularity. Indee...

On the Fischer-Clifford matrices of a maximal subgroup of the Lyons group Ly

The non-split extension group $overline{G} = 5^3{^.}L(3,5)$ is a subgroup of order 46500000 and of index 1113229656 in Ly. The group $overline{G}$ in turn has L(3,5) and $5^2{:}2.A_5$ as inertia factors. The group $5^2{:}2.A_5$ is of order 3 000 and is of index 124 in L(3,5). The aim of this paper is to compute the Fischer-Clifford matrices of $overline{G}$, which together with associated parti...

Characterizing the Multiplicative Group of a Real Closed Field in Terms of its Divisible Maximal Subgroup