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6 votes
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Centralizer of elements in the upper-triangular matrices

Let $p$ be a prime number and $G=\operatorname{GL}_n ( \mathbb{Z} / p \mathbb{Z} )$ such that $n\leq p$. Consider the set $U$ of upper-triangular matrices of $G$ having entries of $1$ on the diagonal. ...
Nourddine Snanou's user avatar
4 votes
0 answers
186 views

On 2-groups of exponent 4 and class 2

Suppose A is a 2-group with the following properties: $\lvert A \rvert = t^3$ with $t$ some even power of $2$; $A$ and $Z(A)$ (the center of $A$) are of exponent $4$; $\lvert Z(A) \rvert = t$ and $[A,...
THC's user avatar
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2 votes
0 answers
167 views

Centralizer of PSL in PGL and of SL in GL: reference request

$\DeclareMathOperator\GL{GL}\DeclareMathOperator\SL{SL}\DeclareMathOperator\PGL{PGL}\DeclareMathOperator\PSL{PSL}$Consider the general linear group $\GL(n,q)$ over a finite field with $q$ elements and ...
Nick Belane's user avatar
1 vote
0 answers
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Central-by-cyclic

This is a following-up question of this. Lemma 2.4 from Robert Griess' paper "Elementary abelian $p$-subgroups of algebraic groups" states: (i) Let $T$ be a finite $p$-group whose Frattini ...
user488802's user avatar
1 vote
0 answers
74 views

$C_G(E)= E \times{\rm PGL}_k(q)$

Let $r$ be an odd prime and $q$ a power of a prime $p$ where $r\neq p$. If $r^m|n$ and $q\equiv1$ (mod $r$), then $r^{1+2m}.{\rm Sp}_{2m}(r)\le{\rm GL}_n(q)$ and $Center(r^{1+2m}.{\rm Sp}_{2m}(r))\le ...
user488802's user avatar
1 vote
0 answers
60 views

Centralisers of involutions not quasi-isolated

The quasi-isolated elements of the algebraic group $G=\operatorname{PGL}_{n}(\mathbb{C})$ are classified in the paper "quasi-isolated elements in reductive groups" by C. Bonnafe. Let's focus ...
user488802's user avatar