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Linear representations of algebras and groups, Lie theory, associative algebras, multilinear algebra.
3
votes
0
answers
154
views
Are these statements correct for all reductive groups, or just for $\operatorname{GL}_2$?
I'm reading the following notes on Brian Conrad's website. There are a couple of statements there which seem too good to be true. There is Proposition 3.6, which states:
(Bernstein): Every irred …
1
vote
0
answers
128
views
Is the root cone is contained in the weight cone?
Originally posted on math.stackexchange. Let $G$ be a semisimple algebraic group over a field $k$. Let $A_0$ be a maximal split torus of $G$, and $\mathfrak a_0 = \operatorname{Hom}(X(A_0), \mathbb …
2
votes
0
answers
220
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Classification of finite dimensional representations of split complex reductive groups
Finite dimensional, irreducible representations of simply connected, complex semisimple algebraic groups can be classified by their highest weight. I was wondering if there is an analogous classifica …
3
votes
1
answer
76
views
Functions in the induced space compactly supported in $PN^-$ modulo $P$
Let $P_0$ be a minimal parabolic subgroup of a connected, reductive group $G$ over a $p$-adic field $k$. Let $P$ be a parabolic subgroup containing $P_0$ with Levi decomposition $P = MN$. Let $N^-$ …
3
votes
0
answers
276
views
Errata for Casselman's unpublished notes
In the first chapter of W. Casselman's unpublished notes on representation theory, there is at least one stated result which is not true:
A counterexample to this last result is given in the questi …
2
votes
0
answers
47
views
If $f \in \operatorname{c-Ind}_Q^P \sigma$, then $f|_N$ is compactly supported modulo $Q \ca...
There is a claim in a proof in Casselman's notes on representation theory which I have not been able to verify. I have asked several people and nobody knows why it is true.
The thing I can't figur …
5
votes
1
answer
427
views
Generic supercuspidal representations of $\operatorname{GL}_n$ can be defined by integrals o...
Let $(V,\pi)$ be an irreducible, admissible, supercuspidal representation of $G = \operatorname{GL}_n(F)$ for $F$ a $p$-adic field. Let $B = TU$ be the usual Borel subgroup, maximal torus, and unipot …
4
votes
0
answers
282
views
Meaning of a highly ramified character for reductive groups
Let $F$ be a $p$-adic local field, and $G$ a connected reductive group over $F$. What is the meaning of a "highly ramified character" of $G(F)$? I have seen this terminology in many places in repres …
4
votes
0
answers
130
views
Supercuspidals and representations of $\operatorname{Gal}(\overline{F}/F)$
Let $F$ be a $p$-adic field, $G = \operatorname{Gal}(\overline{F}/F)$ and $W$ the Weil group of $F$. The inclusion map $W \subset G$ is continuous with dense image, so $\rho \mapsto \rho|_W$ defines …
6
votes
1
answer
331
views
Irreducibility of the unramified principal series
Let $G = \operatorname{GL}_n(F)$ with the usual Borel subgroup $P = TU$. Let $\chi = \chi_1 \otimes \cdots \otimes \chi_n$ be an unramified character of $T$. Suppose that $\chi$ is regular, which is …
13
votes
0
answers
397
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Bernstein-Zelevinsky classification: viewing a representation as a subrepresentation or a qu...
$\DeclareMathOperator{\GL}{GL}$
$\DeclareMathOperator{\Ind}{Ind}$I have a question on the details of the Bernstein-Zelevinsky classification. This classification allows us to obtain irreducible repre …
2
votes
2
answers
1k
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Definition of the weight lattice for a nonreduced root system
Let $(V,\Phi)$ be a root system with dual root system $(V^{\ast},\Phi^{\vee})$. Let $\Delta = \{\alpha_1, ... , \alpha_n\}$ be a set of simple roots for $V$, and let $\Delta^{\vee} = \{\alpha_1^{\vee …
7
votes
1
answer
238
views
Definition of functions in the induced space from parabolic induction
Let $P$ be a parabolic subgroup of a connected, reductive group $G$ over a $p$-adic field. Let $M$ be a Levi subgroup of $P$, and let $N$ be the unipotent radical of $P$. If $(\pi,V)$ is a smooth, i …
3
votes
1
answer
354
views
In a non-reduced root system, $s_{\alpha}(\beta)^{\vee} = s_{\alpha^{\vee}}(\beta^{\vee})$
In Bill Casselman's notes on root systems (http://www.math.ubc.ca/~cass/courses/tata-07a/Roots.pdf), I am confused about the proof of the result $s_{\alpha}(\beta)^{\vee} = s_{\alpha^{\vee}}(\beta^{\v …
1
vote
0
answers
85
views
The convergence of the factor $\gamma(P)$ in the Iwasawa decomposition
Let $G$ be a connected, reductive group over a $p$-adic field $k$, $A_0$ a maximal split torus of $G$, and $P = MU$ a parabolic subgroup with $M$ containing $A_0$. Let $\overline{P} = M \overline{U}$ …