2
votes
1answer
130 views
The Jantzen-Schaper theorem
Does anybody have an electronic copy of Schaper's PhD thesis:
K.D. SCHAPER, ‘Charakterformeln fur Weyl-Moduln und Specht-Moduln in Primcharacteristik’,
Diplomarbeit, Bonn, 1981.
…
3
votes
0answers
70 views
Expression of basis vectors of permutation modules in different bases.
This is a cross-post from math.se, because I did not get any answer there:
Write $[n]:=\{1,\ldots,n\}$. For a partition $\lambda\vdash n$, I will write $[\lambda]$ for the Specht …
1
vote
0answers
38 views
On generalization of Wigner semi circle
I want to analyse noise model for a matrix M whose entries are not real numbers. The matrix is a collection of N permutation matrices of size nxn i.e, M is NnxNn. Because its a col …
14
votes
1answer
270 views
What is the length of the shortest law of $S_n$?
What is the length of the shortest word $w\in F_2$ such that $w(x,y)$ is trivial for every $x,y\in S_n$?
There is a simple argument showing that we must have $\ell(w)\geq n$. See …
4
votes
1answer
110 views
Representations of Sym(n) and SL_d
Irreducible representations of the symmetric group Sym$(n)$, and degree-$n$ algebraic representations of SL$_d(\mathbb C)$ for $d\ge n$, can both be classified by Young diagrams wi …
7
votes
1answer
148 views
Permutation character of the symmetric group on subsets of certain size
The symmetric group $S_n$ acts on $[n]:=\{1,\ldots,n\}$, thereby inducing an action on the set $$\wp_k(n)=\{\: A\subseteq[n] \::\: \#A=k \:\}$$ of subsets of cardinality $k$, simpl …
5
votes
1answer
108 views
Dimension of Specht Modules $S^\lambda$
In the study of representation theory of $S_n$, we know that the irreducible characters of $\chi_\lambda$ of $S_n$ are indexed by partitions $\lambda \vdash n$. There are several m …
6
votes
1answer
165 views
Decomposition of $\mathrm{End}(V)$ as $S_n\times S_n$-module
Let $V$ be a finite-dimensional, complex vector space and set $\newcommand{\Gl}{\mathrm{Gl}}G:=\Gl(V)\times\Gl(V)$. Let $E:=\mathrm{End}(V)$ and consider its coordinate ring $\math …
12
votes
4answers
524 views
Largest permutation group without 2-cycles or 3-cycles
The largest permutation group without 2-cycles is $A_n$, which has size $n!/2$. I think the largest permutation group without 2-cycles or 3-cycles is much smaller, but I can't figu …
3
votes
2answers
230 views
A basis for Schur functors
Suppose $V$ is a finite-dimensional vector space (over $\mathbb{C}$) and $\lambda$ is a partition of $n$ (not necessarily the dimension). Let $S^\lambda(V)=(V^{\otimes n})_\lambda$ …
1
vote
0answers
72 views
Next smallest dimension of Specht Module after $(n)$, $(1^n)$, $(n-1,1)$ and $(2,1^{n-2})$
In representation theory of $S_n$, we know that for $n \geq 9$, the only Specht modules $S^\alpha$ of dimension $f^\alpha < {n-1 \choose 2} - 1$ are:
$S^{(n)}$ and $S^{(1^n)}$ …
7
votes
1answer
252 views
Littlewood Richardson rule and seminormal basis of Specht modules
Background
Seminormal Basis of Specht modules of $\mathfrak{S}_n$
Let $\lambda$ be a partition of $n$. A $\lambda$-tableau is a
bijection $\mathfrak{t}:\lambda \to {1,2...,n} …
1
vote
1answer
384 views
How to solve a system of equations over permutations?
Imagine you have a $n\times n$ matrix filled in with permutations over $n$ elements. Now you pick one permutation from each row randomly starting from the first row and by multiply …
4
votes
1answer
203 views
Identity involving partitions coming from representations of alternating groups
It is not difficult to show that the number of conjugacy classes in the alternating group $A_n$ is given by
classes in the alternating group = no. of even partitions + no. of s …
4
votes
2answers
306 views
Algorithm for reducing words in a Coxeter group
Let $W$ be a Coxeter group with set of simple reflections $S$. Suppose that I have chosen a preferred reduced decomposition for every element of $W$. Given an arbitrary word in the …

