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Linear representations of algebras and groups, Lie theory, associative algebras, multilinear algebra.
8
votes
1
answer
682
views
Kazhdan-Lusztig Polynomials and Intersection Cohomology
I hope this question has not been asked before.
I would like to know which Ideas led (Deligne), Kazhdan and Lusztig believe, that Kazhdan–Lusztig polynomials can be expressed via intersection cohom …
6
votes
1
answer
231
views
Harish-Chandra modules of $\mathrm{PSL}_2(\mathbb{R})$
I am sorry to bother you with this question but I can't figure out this myself (and Mathematics Stack Exchange didn't help).
Is the category of Harish-Chandra Modules of $PSL_2(\mathbb{R})$ equivalen …
11
votes
1
answer
1k
views
Characteristic Classes in Geometric Representation Theory
Geometric respectively topological methods are widely applied in representation theory. As far as I know mainly cohomological methods are used.
I wonder if there are concrete applications of the …
3
votes
reference help indecomposable representations of SL(2,R)
I hope my answer is not a reproduction of Jeffrey Adams answer. (I dont have the book at hand)
If I understand you right you want to know the indecomposable Harish-Chandra modules of $SL_2(\mathbb{R} …
6
votes
Accepted
Learning representation theory of real reductive lie groups
First note that there is the book of Vogan (Representation Theory if real reductive groups) which discusses the case of $SL_2(\mathbb{R})$ on a very basic level. I think this is a good start. In my o …
5
votes
1
answer
401
views
Equivariant Formality
Let $G$ be a finite group and $\mathcal{A}$ be a $dg$-algebra. Assume $G$ acts on $\mathcal{A}$, i.e. there exists a homomorphism $G\to {\rm Aut}_{dg}(\mathcal{A})$.
Assume further there exists a $dg …
14
votes
Introductory References for Geometric Representation Theory
Additionally to Peter Crooks answer I would recommend to study the book of Hotta and others :
D-Modules, Perverse Sheaves, and Representation Theory
Here you can learn about derived categories and pe …
5
votes
Accepted
Whitney stratification and affine grassmanian
The point is following: $\overline{Gr^\lambda}$ is a finite dimensional variety acted upon by the pro-algebraic group $G(\mathbb{C}[[t]])$.
This action factors through the action of some finite dim …
4
votes
Accepted
Stratifications and Filtrations of the Affine Grassmannian
I do not really answer you question but maybe this helps:
Let $\mathcal{K} =\mathbb{C}((t))$ and $\mathcal{O}:=\mathbb{C}[[t]]$. For $n\geq 0$ denote the $\mathcal{K}_n$ the $\mathcal{O}$ ideal in $\ …
5
votes
Strata of the Affine Grassmannian
One can also argue as follows:
$G(\mathcal{O})$ operates transitivly on each stratum $\mathcal{G}^\lambda$. The isotropy group at $t^\lambda$ is $P^a_\lambda:= (t^\lambda)^{-1}G(\mathcal{O})t^\lambda …
3
votes
1
answer
303
views
A question on algebraic loop groops
Setup:
Let $\mathcal{K}=\mathbb{C}((t))$, $\mathcal{O}:= \mathbb{C}[[t]]$ and $G$ be a reductive algebraic group (over $\mathbb{C}$). Let further $\mathcal{K}_n$ denote the $\mathcal{O}$-ideal in $\m …
8
votes
1
answer
517
views
Restriction to Levi Subgroups and the Affine Grassmannian
Let $G$ be a complex reductive group, $L\subset G$ a Levi subgroup and $Rep(G)$ the category of rational representations of $G$.
My Question:
What is the geometric analogue of the restriction f …
1
vote
Orbits on the affine Grassmanian, and closure ordering
This may be a little bit lazy but the statement you want is given on page 227 in [Lu]. The proof is given on page 228.
[Lu]=Lusztig, George
Singularities, character formulas, and a q-analog of weigh …
2
votes
1
answer
683
views
Derived Push-Forward of Morphism of Perverse Sheaves and Translation Functors
I hope this question is not too vague.
Let $G$ be a complex reductive group, $B$ a Borel subgroup of $G$, and $P$ a parabolic containing $B$.
Denote by $\pi:G/B\to G/P$ the canonical map. Consider th …
10
votes
0
answers
428
views
A question about multiplication in $G(\mathbb{C}((t)))$ and Affine Grassmannians
I am sorry to give a bounty to such a crappy question but an answer would help me a lot.
I am stuck with the following simple (i guess but) technical problem.
Let $G$ be a complex reductive grou …