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Linear representations of algebras and groups, Lie theory, associative algebras, multilinear algebra.

5 votes

Reference request: representation theory of the hyperoctahedral group

This is quite late but I've been playing around with type BC Coxeter group representations recently and thought I'd provide a nice reference I've found for anyone else that is interested: Alun Morris …
George Melvin's user avatar
3 votes

Computing the Grothendieck-Springer resolution for $G = SL_2$

Hi Vinoth, here are my thoughts, hopefully they're correct and what you're after: You can think of $\mathfrak{\tilde{g}}$ as the set of pairs $$\{(X,L)\in \mathfrak{g}\times \mathbb{P}^{1}\;|\; X(L …
George Melvin's user avatar
2 votes
2 answers
602 views

A remark in Jantzen's 'Lectures on Quantum Groups'

In Jantzen's AMS text 'Lectures on Quantum Groups' he makes the following remark (p.187, preface to Chapter 9): "For general (complex semisimple f.d. Lie algebra) $\frak{g}$ we can consider for each …
George Melvin's user avatar
6 votes
2 answers
720 views

Triviality of Associated Bundles

Let $P\rightarrow M$ be a principal (right) $G$-bundle, where $G$ is a Lie group. Given a finite-dimensional representation of $G$, $V$ say, we can define the associated bundle $P\times_{G}V\rightarr …
George Melvin's user avatar
11 votes
5 answers
2k views

Applications of Chevalley Restriction Theorem

Let $G$ be a simple linear algebraic group (over $\mathbb{C}$, say) and $\mathfrak{g}$ be its Lie algebra, $\mathfrak{t}\subset \mathfrak{g}$ the Lie algebra of a maximal torus in $G$ and $W$ the corr …
George Melvin's user avatar
2 votes
Accepted

Nilpotent Lie Algebras

Whenever $ad_{\xi}$ is an endomorphism of $\mathfrak{g}$ whose corresponding partition $\pi: 1^{s_{1}}2^{s_{2}} \cdots \;$ of $\dim \mathfrak{g}$ is such that $s_{1} =0$, then we have $im\; ad_{\xi} \ …
George Melvin's user avatar
1 vote

springer resolution over $\wedge^3 \mathbb{C}^6$

The dimension of the nilpotent orbits of $\mathfrak{gl}_{6}$ can be described using the corresponding partition $\pi: d_{1}+d_{2}+\ldots + d_{k} =6$ associated to a nilpotent orbit - so $\pi$ is the p …
George Melvin's user avatar
2 votes
1 answer
243 views

Springer Action on Centre of Parabolic Category O (after Brundan)

I recently learned of a result of Brundan describing the centre of the regular block of parabolic category $\mathcal{O}$ for $\mathfrak{gl}_{n}$ as the cohomology of a corresponding Springer fibre (av …
George Melvin's user avatar
5 votes
2 answers
923 views

Status of a conjectural definition of H. Nakajima

In his paper '$t$-analogue of $q$-characters of finite dimensional representations of quantum affine algebras' - http://arxiv.org/abs/math/0009231 - H. Nakajima states a conjectural definition of the …
George Melvin's user avatar
5 votes
1 answer
304 views

Endomorphisms in Category O and Schubert Classes

Let $\mathfrak{g}\supset \mathfrak{b}\supset \mathfrak{h}$ be a complex semisimple Lie algebra, with choice of Borel and Cartan subalgebras, $W$ the Weyl group. W. Soergel's 'Endomorphismensatz' all …
George Melvin's user avatar
3 votes
1 answer
860 views

'Generalised' coinvariant algebras

Let $\mathfrak{g}$ be a simple complex Lie algebra, and $\mathfrak{h}\subset\mathfrak{g}$ a Cartan subalgebra with Weyl group $W$. Consider the fibre product $\mathfrak{h}\times_{\mathfrak{g}} N$, whe …
George Melvin's user avatar
5 votes
3 answers
574 views

Non-symmetric quiver varieties

Given a symmetric Cartan datum $(I,\cdot)$, H. Nakajima has defined a family of varieties - known as quiver varieties - and has used them to give geometric constructions of the representation theory o …
George Melvin's user avatar
10 votes

motivating geometric representation theory

I'm struggling to see what the actual question is but here is an example of a non-trivial use of geometry to prove a simple statement in representation theory; moreover, it is the only known way to o …