Displaying similar documents to “Moduli for stable actions of an abelian group on trees of projective lines”

R-trees and the Bieri-Neumann-Strebel invariant.

Gilbert Levitt (1994)

Publicacions Matemàtiques

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Let G be a finitely generated group. We give a new characterization of its Bieri-Neumann-Strebel invariant Σ(G), in terms of geometric abelian actions on R-trees. We provide a proof of Brown's characterization of Σ(G) by exceptional abelian actions of G, using geometric methods.

Actions of finitely generated groups on -trees

Vincent Guirardel (2008)

Annales de l’institut Fourier

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We study actions of finitely generated groups on -trees under some stability hypotheses. We prove that either the group splits over some controlled subgroup (fixing an arc in particular), or the action can be obtained by gluing together actions of simple types: actions on simplicial trees, actions on lines, and actions coming from measured foliations on 2 -orbifolds. This extends results by Sela and Rips-Sela. However, their results are misstated, and we give a counterexample to their...

Moduli spaces of decomposable morphisms of sheaves and quotients by non-reductive groups

Jean-Marc Drézet, Günther Trautmann (2003)

Annales de l’institut Fourier

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We extend the methods of geometric invariant theory to actions of non–reductive groups in the case of homomorphisms between decomposable sheaves whose automorphism groups are non–reductive. Given a linearization of the natural action of the group Aut ( E ) × Aut ( F ) on Hom(E,F), a homomorphism is called stable if its orbit with respect to the unipotent radical is contained in the stable locus with respect to the natural reductive subgroup of the automorphism group. We encounter effective numerical conditions...