bio  website  math.umass.edu/~jeh 

location  U. Massachusetts, Amherst  
age  75  
visits  member for  5 years, 6 months 
seen  1 hour ago  
stats  profile views  16,374 
Moreorless retired professor at UMass Amherst.
Basically an algebraist with interests in Lie theory,
specifically representation theory and related
algebraic geometry.
1d

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Form of elements of a Lie algebra
@Bruce: Probably it's helpful to include more details about the book ams.org/mathscinetgetitem?mr=1231799, along with the later short expository article ams.org/mathscinetgetitem?mr=2035110 
Aug
27 
awarded  Nice Answer 
Aug
26 
awarded  Nice Answer 
Aug
21 
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Any representation is a sub representation of direct sum of regular representation
As abx and David point out, this is a basic (early) lemma in the Chevalley development of affine algebraic groups. It's found in textbooks by Borel et al., and generalizes well to affine group schemes as Scott Carnahan indicates. The traditional language involves "representative functions" as developed by Chevalley, Hochschild, and others. (The notes of Steinberg's Tata lectures were written up by Deodhar, then a student there, but could have used some editing.) 
Aug
20 
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CasselmanShalika formula for split reductive groups
This does seem to be a helpful reference (which I've corrected to get the link right). 
Aug
20 
revised 
CasselmanShalika formula for split reductive groups
deleted 5 characters in body 
Aug
16 
awarded  Popular Question 
Aug
14 
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Classification of finite group schemes over a field
As Jason points out, there is a big difference depending on the characteristic of the field. In prime characteristic there are also Frobenius kernels, etc. 
Aug
13 
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Coxeter Subgroups of Coxeter Groups
Be careful about the formulation: being a "Coxeter group" requires fixing a set of involutive generators. However, a finite symmetric group $S_n$ will typically contain a lot of smaller Coxeter groups whose generators have nothing to do with those of $S_n$ itself, since every finite group has some embedding in a symmetric group. In another direction, a subgroup of a Coxeter group generated by a finite set of "reflections" (conjugates of the given generators) will be a Coxeter group relative to this new set of involutions (Deodhar, Dyer). Many possibilities. 
Aug
13 
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Role of nontrivial component groups in Springer Correspondence?
@Dror: Yes, I should have specified that $G$ is semisimple of adjoint type as is usually done in the literature on Springer correspondence, to avoid such cases. I've edited appropriately. Thanks for pointing this out. 
Aug
13 
revised 
Role of nontrivial component groups in Springer Correspondence?
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Aug
13 
revised 
Normalized invariant form on a KacMoody Algebra
edited tags 
Aug
13 
answered  Normalized invariant form on a KacMoody Algebra 
Aug
12 
awarded  Necromancer 
Aug
12 
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Are the orders of the generators of a group and the product of pairs of thereof enough for this group to be isomorphic to a Coxeter group?
@Geoff: Your expanded answer is more helpful, though I was still wondering how to specify a smallest possible $G$ of the type specified which couldn't have the structure of a Coxeter group. Is there a smallest such simple group one can point to? 
Aug
12 
answered  Are the orders of the generators of a group and the product of pairs of thereof enough for this group to be isomorphic to a Coxeter group? 
Aug
12 
revised 
Are the orders of the generators of a group and the product of pairs of thereof enough for this group to be isomorphic to a Coxeter group?
added 10 characters in body; edited tags; edited title 
Aug
11 
revised 
Bruhat decomposition for reductive groups in characteristic zero?
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Aug
11 
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Bruhat decomposition for reductive groups in characteristic zero?
@ L Spice: No, that was just too hurriedly written. Will edit. Thanks. 
Aug
6 
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Generalization of a theorem of Steinberg
@Nick: Yes, that's the paper by Matt Douglass. The Lehrer paper has open access if you follow the article link given and click on PDF at the lower right. (MathSciNet access shouldn't be needed for the two links I gave.) 