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Linear representations of algebras and groups, Lie theory, associative algebras, multilinear algebra.
1
vote
Can $T$ act trivial in a repn of SL$_2(\mathbb{Z}_N)$?
I answer the question in the title: $T$ can act trivial iff the rep is trivial.
Here is the proof:
We have
$$ SL_2(Z/N) = \oplus_{p^k || N} SL(Z/p^k)$$
by the Chinese remainder theorem and because S …
2
votes
Restriction of discrete series representations
I'll give some fairly general remarks - too long for a comment.
I assume $G$ is reductive and $P$ parabolic. The Mackey Restriction Induction formula yields
$$ Res_{H} Ind_{P}^G \pi = \int\limits_{\g …
6
votes
Accepted
Harish-Chandra modules of $\mathrm{PSL}_2(\mathbb{R})$
Yes, the central character of the even $K$-types is trivial, and of the odd ones is the sign character.
Also, this can easily be seen from the classification of irreducible representation on Hilbert …
1
vote
Accepted
Theorem of Cantor-Bernstein in the category of smooth representation of $G$
Here are some observations, too long for a comment:
1) Note that cuspidal irreducible representation are compactly induced
$\sigma = c-ind_K^G \tau = Ind_K^G \tau$
2) You have the second adjointnes …
1
vote
1
answer
1k
views
Restriction of irreducible representations
Given a locally compact group $G$ with a compact subgroup $K$.
Assume we are given two irreducible, infinite dimensional, admissible representations $\pi$ and $\pi'$ of $G$.
What are examples, w …
9
votes
2
answers
2k
views
Frobenius formula for the determinant
Is there a formula for the determinant of an induced representation, e.g. in the fashion of the Frobenius character formula.
I would hope for something:
$$ det \; Ind_H^G \rho(g) = (-1)^\alpha \p …
1
vote
fixed vector of a generic representation of GL(n,F)
To my knowledge, it is not known whether $Ind_{P_{n,k}}^{GL_n(o)} 1$ decomposes with single multiplicity.
This is certainly necessary by Frobenius reciprocity
$$ dim Hom_{P_{n,k}}( 1 , Res_{P_{n,k}} …
1
vote
How does one show the existence of discrete and complementary series for SL(2,R)?
I found Traces of Hecke operators by Knightly and Li very readable. They treat Gl(2,R) by a similar method. Knapp or Wallach is
also nice to read and more general. They have chapters for Sl(2,R) and …
1
vote
Accepted
Modular Forms w.r.t. different representations linearly independent?
No, they are not. Consider $\rho_1$ and $\rho_1 \oplus \rho_2$. It the $\rho_j$ are pairwise disjoint, i.e., $Hom_G(\rho_j , \rho_l)= \{0 \}$ for $j \neq l$, then this is sufficient. This can be expre …
2
votes
Decomposition into irreducibles of the representation $L^2(SL_2(\mathbb{C})/\Gamma)$ for $\G...
Because only infinite dimensional, unitary representation of $SL(2,F)$ for a local field $F$ can fail to be tempered, if they are spherical. This follows from the classification. This is true for $GL( …
1
vote
1
answer
330
views
Fell topology in terms of distributions
Question: Can the Fell topology be expressed in terms of the distributions of the the tracial states of a unitary representations, that, is $\pi_j \rightarrow \pi$ if and only if $tr\; \pi_j \righ …
1
vote
Accepted
reference help about a result on representation theory
Every unitary $\infty$-dim'l irreducible representation can be writen as inducing a square-integrable representation from a parabolic subgroup with Levi subgroup $G' =G_{r_1} \times \dots G_{r_2}$. G …
1
vote
Unitary Representations of $GL_2({\mathbb Q}_p)$
If an irreducible representation is unitarizable, it has at most one unitarization (up to equivalence). Going back from $S_2$ to $S_1$, you only have to consider the invariant subspace of smooth vecto …
3
votes
Accepted
Strata of K-types appearing in irreducible representations of p-adic GL(2)
I will try to answer the question as far as I have understood it. Please comment.
Clifford's theorem
Let $G$ be a finite group. Let $H$ be a normal subgroup of $G$. The groups $G$ resp. $G/H$ act on …
2
votes
Accepted
algebraic groups and their Lie algebras
I suggest the following lecture notes of Bruhat:
www.math.tifr.res.in/~publ/ln/tifr14.pdf
Chapter 3 & 4 should answer most of your questions.
For example, there are statements like this :
Proposi …