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Affine braid group actions on derived categories of Springer resolutions

Roman Bezrukavnikov, Simon Riche (2012)

Annales scientifiques de l'École Normale Supérieure

In this paper we construct and study an action of the affine braid group associated with a semi-simple algebraic group on derived categories of coherent sheaves on various varieties related to the Springer resolution of the nilpotent cone. In particular, we describe explicitly the action of the Artin braid group. This action is a “categorical version” of Kazhdan-Lusztig-Ginzburg’s construction of the affine Hecke algebra, and is used in particular by the first author and I. Mirković in the course...

Compactification via le spectre réel d’espaces des classes de représentation dans SO ( n , 1 )

Taoufik Bouzoubaa (1994)

Annales de l'institut Fourier

Soit Γ un groupe de type fini non élémentaire. On note D n ( Γ ) l’ensemble des structures hyperboliques de dimension n sur Γ . D n ( Γ ) peut se réaliser comme fermé dans un espace semi-algébrique qui admet une compactification naturelle par le spectre réel. On note D n ( Γ ) sp le compactifié via le spectre _ réel de D n ( Γ ) . L’objet de cet article est de décrire les points ajoutés dans D n ( Γ ) sp . La compactification obtenue de cette manière permet d’interpréter “les points frontières” comme des représentations de Γ dans SO F + ( n , 1 ) F ( ) est un corps réel...

Contractions of Lie algebras and algebraic groups

Dietrich Burde (2007)

Archivum Mathematicum

Degenerations, contractions and deformations of various algebraic structures play an important role in mathematics and physics. There are many different definitions and special cases of these notions. We try to give a general definition which unifies these notions and shows the connections among them. Here we focus on contractions of Lie algebras and algebraic groups.

Genus sets and SNT sets of certain connective covering spaces

Huale Huang, Joseph Roitberg (2007)

Fundamenta Mathematicae

We study the genus and SNT sets of connective covering spaces of familiar finite CW-complexes, both of rationally elliptic type (e.g. quaternionic projective spaces) and of rationally hyperbolic type (e.g. one-point union of a pair of spheres). In connection with the latter situation, we are led to an independently interesting question in group theory: if f is a homomorphism from Gl(ν,A) to Gl(n,A), ν < n, A = ℤ, resp. p , does the image of f have infinite, resp. uncountably infinite, index in...

Naive boundary strata and nilpotent orbits

Matt Kerr, Gregory Pearlstein (2014)

Annales de l’institut Fourier

We give a Hodge-theoretic parametrization of certain real Lie group orbits in the compact dual of a Mumford-Tate domain, and characterize the orbits which contain a naive limit Hodge filtration. A series of examples are worked out for the groups S U ( 2 , 1 ) , S p 4 , and G 2 .

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