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Questions about the branch of algebra that deals with groups.

1 vote
1 answer
303 views

A question in ring theory

Is there an example of two groups $G_{1}, G_{2}$ such that there are two non isomorphic ring $R_{1}$ and $R_{2}$ such that the additive group of both rings is isomorphic to $G_{1}$ and their unit gro …
Ali Taghavi's user avatar
6 votes
2 answers
447 views

A possible characterization of the category of finite $p$-groups

Let $\mathcal{FG}$ be the category of finite groups. Let $S$ be a full subcategory of $\mathcal{FG}$. Assume that $G\in \mathcal{FG}$ and $P\in S$ is a subgroup of $G$. We say that $P$ is $S$-maximal …
Ali Taghavi's user avatar
0 votes
0 answers
203 views

A particular functor on the category of abelian groups?

Is there a functor $F$ from the category of abelian groups to itself such that for every non trivial group $G$, $F(G)$ can not be embedded in $G$? Edit: According to the comment by Prof. Goodwillie …
Ali Taghavi's user avatar
1 vote
1 answer
389 views

Does a cocompact subgroup of a topological group contain a cocompact normal subgroup?

Motivation: It is obvious that for a finite index subgroup $H$ of a group $G$, there exists a normal subgroup $K$ of $G$, $K\subset H$, with $|G/K|<\infty$. Our question: Let $G$ be a topological gro …
Ali Taghavi's user avatar
6 votes
1 answer
250 views

Is $G\mapsto \operatorname{Hol}(G)$ the object component of any functor on the category of g...

On the objects of the category of groups we define the mapping $G\mapsto \operatorname{Hol}(G)$, the holomorph $G\rtimes \operatorname{Aut}(G)$ of $G$. Can we extend this mapping to a functor on this …
Ali Taghavi's user avatar
3 votes

Solving algebraic problems with topology

The following paper and its references contains some algebraic consequences of vector bundle theory. Vakhtang Lomadze, Applications of vector bundles to factorization of rational matrices, Line …
5 votes
2 answers
494 views

Is every countable discrete group a subgroup of a non discrete Lie group?

1)Let $G$ be a countable discrete group. Can $G$ be embbeded in a locally connected Lie group? 2)let $G$ be a countable discrete group with a prescribed generating set and corresponding word metr …
Ali Taghavi's user avatar
2 votes
1 answer
152 views

A group associated to a pair of integers $(k,p)$ where $p$ is a prime number

Let $k\in \mathbb{N}$ be a natural number and $p$ be a prime number with $p\nmid k$. (We thank Prof. Bartel for his comment on the latter non divisibility condition.) We denote by $U(p)=\{1,2,\ldots …
Ali Taghavi's user avatar
5 votes
1 answer
303 views

Amenability of $S^{\infty}$

Let $G$ be the group of all permutations of $\mathbb{N}$. If I am not mistaken, this group is denoted by $S^{\infty}$. Is there a precise locally compact topology on $G$ such that $G$ would b …
Ali Taghavi's user avatar
1 vote
0 answers
85 views

A cross product on $C^*_{red} G$

For every group $G$, the reduced group $C^*$-algebra $C^*_{red}G$ is equipped with the inner product $\langle a,b\rangle=tr(ab^*)$ where "$tr$" is the standard trace on group $C^*$-algebras. For wha …
Ali Taghavi's user avatar
2 votes
1 answer
613 views

Groupoid isomorphism vs. group isomorphism

Assume that $\Gamma$ is a group with neutral element $e$. We associate to $\Gamma$ the following groupoid $G$: $G=\Gamma \times \Gamma,\;\;\;G^{(0)}=\Gamma \times \{0\},\;\;s(a,b)=(a,e),\;\;\; r(a, …
Ali Taghavi's user avatar
8 votes
1 answer
619 views

Why is this group called "The Holomorph of a group"

Many years ago I found in google the notation "Holomorph of group". It is the semi direct product of $G$ with $Aut(G)$. Why is the term "Holomorph" used here, while it is usually used for complex anal …
Ali Taghavi's user avatar
2 votes
0 answers
301 views

A question on Giles Gardam counter example to the Unit conjecture of Kaplansky

The unit version of the Kaplansky conjecture is about units in $FG$ where $F$ is a field and $G$ is a torsion free group. In a recent counter example by Giles Gardam, it is given an e …
Ali Taghavi's user avatar
1 vote
1 answer
107 views

Some quantities associated to finite dimensional Hopf algebras

let $(H,\Delta,m,s)$ be a Hopf algebra. To this Hopf algebra one can associate two obvious linear maps $T_H, S_H: H \to H $ with $T_H=m\circ \Delta,\quad S_H=s$. Are there two finite dimensional …
Ali Taghavi's user avatar
0 votes
1 answer
185 views

A subset (or subgroup) associated to a group

Edit: According to comment conversations we revise the question. Let $G$ be a group. We consider the following subset of $G$: $$\{g\in G \mid e^{\lambda_g} \in \mathbb{C}\lambda (G)\},$$ where $\lamb …
Ali Taghavi's user avatar

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