Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 9672

Questions about the branch of algebra that deals with groups.

4 votes

Bernstein's presentation for the Hecke algebra

I found the paper of Chriss and Khuri-Makdisi (Chriss, Neil; Khuri-Makdisi, Kamal. On the Iwahori-Hecke algebra of a $p$-adic group. Internat. Math. Res. Notices 1998, no. 2, 85--100.) quite helpful. …
Martin Sleziak's user avatar
4 votes
1 answer
152 views

Do the class vector and character vector of a $p$-group determine each other?

To a finite $p$-group, we can associate two vectors $(v_0,v_1,\dotsc)$: The class vector - $v_i$ is the number of conjugacy classes of order $p^i$. The character vector - $v_i$ is the number of comp …
3 votes

The extension class of a finite Heisenberg group

I believe that your conjecture is equivalent to Theorem 3.5 in the paper Locally Compact Abelian Groups with Symplectic Self-duality, Advances in Mathematics, volume 225, pages 2429-2454, 2010.
Amritanshu Prasad's user avatar
9 votes
Accepted

Branching Rule for alternating groups

This is answered in Theorem 4 of my paper Comparison of Gelfand-Tsetlin Bases for Alternating and Symmetric Groups, with Geetha Thangavelu, which is published in Algebras and Representation Theory, an …
Xueyi Huang's user avatar
5 votes
Accepted

Induced representation of a Young subgroup

The answer is a special case of Young's rule. In my book, I give a very simple method for the slightly easier case where $r=0$. In that case we have: $$ \mathrm{Ind}_{S_k\times S_l}^{S_n} = \bigoplus_ …
Amritanshu Prasad's user avatar
13 votes

Automorphism group of a finite group

A nice set of generators for the automorphism group of a finite abelian group is described by Garrett Birkhoff in his paper titled "Subgroups of abelian groups", Proc. London Math. Soc., s2-38(1):385- …
LSpice's user avatar
  • 12.9k
9 votes
Accepted

Can monomial representations induced from nonmonomial representations?

According to Djokovic and Maizan, the Specht module $V_{(3, 1, 1)}$ of $S_5$ is monomial. This is a representation of dimension $6$, induced from a representation of dimension $3$ of $A_5$. Since $A_5 …
Amritanshu Prasad's user avatar
4 votes
Accepted

subgroups of General linear group with two generators

You would have an answer to your question if you could classify pairs of elements in $GL_n(\mathbf F_q)$ up to simultaneous conjugacy. This is the notorious matrix pair problem, which is the quintesse …
Community's user avatar
  • 1
3 votes
Accepted

A question on automorphisms of finite abelian groups

Here is an outline for odd order abelian $p$-groups: The main point is that every non-zero element in a field with at least three elements is a sum of two non-zero elements. Using this, you can show …
Amritanshu Prasad's user avatar
2 votes

Decomposition of induced representations / Refinement of Mackey's criterion

The proof of Mackey's theorem on intertwiners actually tells you how to construct the endomorphism algebra of an induced representation, not just its dimension. So, if you work a little harder, you ma …
Amritanshu Prasad's user avatar
3 votes

What are the necessary and sufficient conditions for GL(n,Z/p^lZ) to be isomorphic to GL(n,F...

For $l=2$, the only cases where the extension splits are $n=2$ and $p=2,3$ and $n=3$ and $p=2$. In her PhD thesis, on page 3, Pooja Singla attributes this to [Chih Han Sah. Cohomology of split group e …
Amritanshu Prasad's user avatar
7 votes

Hall polynomial when the subgroup is cyclic?

Let's say you want to compute the Hall polynomial $g^\lambda_{(r),\mu}(p)$. According to [Dutta and Prasad, Degenerations and orbits in finite abelian groups], the orbits under the automorphism group …
Amritanshu Prasad's user avatar
3 votes
Accepted

Non-split groups

Besides the basic definitions and examples, you will find a concise description of the vocabulary needed to talk about linear algebraic groups over fields that are not algebraically closed in T. A. Sp …
Amritanshu Prasad's user avatar
2 votes

Automorphisms of a matrix in Smith normal form?

If you have $P$, I think you can recover $Q$ as $(D^{-1}PD)^{-1}$. Therefore, you are looking for invertible integer matrices $P$ such that $D^{-1}PD$ is also invertible (i.e., $P\in GL_n(\mathbf Z)\c …
Amritanshu Prasad's user avatar
10 votes
Accepted

Bruhat decomposition for G(R), R local ring or R=Z/p^r

Bruhat decomposition over $\mathbf Z/p^r\mathbf Z$ is precisely the problem we looked at in this paper. We defined several invariants of double cosets, and classified the pairs $(n,k)$ for which, when …
Amritanshu Prasad's user avatar

15 30 50 per page