Unipotent representations and derived functor modules

Author(s):  
Dan Barbasch
1984 ◽  
Vol 78 (1) ◽  
pp. 131-141 ◽  
Author(s):  
Nolan R. Wallach
Keyword(s):  

2003 ◽  
Vol 201 (2) ◽  
pp. 430-456 ◽  
Author(s):  
Alexander Dvorsky ◽  
Siddhartha Sahi

2006 ◽  
Vol 182 ◽  
pp. 313-379 ◽  
Author(s):  
J.-L. Waldspurger

AbstractLet q be a finite field, G = GLn(q), θ be the outer automorphism of G, suitably normalized. Consider the non-connected group G ⋊ {1, θ} and its connected component = Gθ. We know two ways to produce functions on , with complex values and invariant by conjugation by G: on one hand, let π be an irreducible representation of G we can and do extend to a representation π+ of G ⋊ {1, θ}, then the restriction trace to of the character of π+ is such a function; on the other hand, Lusztig define character-sheaves a, whose characteristic functions ϕ(a) are such functions too. We consider only “quadratic-unipotent” representations. For all such representation π, we define a suitable extension π+, a character-sheave f(π) and we prove an identity trace = γ(π)ϕ(f(π)) with an explicit complex number γ(π).


2019 ◽  
Vol 56 (1) ◽  
pp. 1-12
Author(s):  
Wei Ren ◽  
Duocai Zhang

Abstract Let R be an IF ring, or be a ring such that each right R-module has a monomorphic flat envelope and the class of flat modules is coresolving. We firstly give a characterization of copure projective and cotorsion modules by lifting and extension diagrams, which implies that the classes of copure projective and cotorsion modules have some balanced properties. Then, a relative right derived functor is introduced to investigate copure projective and cotorsion dimensions of modules. As applications, some new characterizations of QF rings, perfect rings and noetherian rings are given.


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