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7h
comment Relationship between group $C^\ast$-algebras $C^\ast(G)$ and graph $C^\ast$-algebras $C^\ast(E)$
It happens. You have more details.
7h
answered Relationship between group $C^\ast$-algebras $C^\ast(G)$ and graph $C^\ast$-algebras $C^\ast(E)$
Jan
12
answered Can one describe the multiplication of two Bruhat cells?
Jan
1
answered Directed homotopy in the Cayley graph of a monoid
Dec
10
comment A canonical representative in Morita equivalence class
The basic algebra is the endomorphism algebra of the direct sum of one copy of each projective indecomposable module and hence is uniquely determined.
Dec
10
comment A canonical representative in Morita equivalence class
If it exists, then it is unique since such an algebra must be basic and there is a unique basic algebra in each Morita class.
Dec
10
comment A canonical representative in Morita equivalence class
If $K$ is $\mathbb Q$ and $A$ is the quaternion division algebra over $\mathbb Q$, then $A$ is already basic and has trivial Jacobson radical. No algebra Morita equivalent to $A$ has quotient by is radical commutative because all such are semisimple and $A$ is not Morita equivalent to a commutative algebra..
Dec
6
comment How to construct a proper action of a group of finite virtual cohomological dimension?
More generally a finitely generated group has a cocompact proper action on a tree iff it has a finite index free subgroup.
Dec
6
comment How to construct a proper action of a group of finite virtual cohomological dimension?
A virtually cyclic group always has proper action on the real line.
Dec
4
comment How large can the smallest generating set of a group $G$ of order $n$ be?
Anyway I did not intend to criticize the closers although I see my comment could be read that way. I was really just curious since I can see the argument in both directions
Dec
4
comment How large can the smallest generating set of a group $G$ of order $n$ be?
The choice of a p-group shows a lack of knowledge of the Frattini subgroup, but on the other hand the prime factorization is in the problem and then CFSG is needed.
Dec
4
comment Group associated to the monoid $({\cal P}(X\times X), \circ)$
It is not closed under not multiplication if you remove the empty set
Dec
4
comment How large can the smallest generating set of a group $G$ of order $n$ be?
I am curious why there are 3 votes to close this?
Dec
2
awarded  Notable Question
Nov
30
comment Toposes (topoi) as classifying toposes of groupoids
Thanks for this. It will take me time to sort this out.
Nov
25
comment Okounkov-Vershik approach to representation theory of $S_n$
Anyway, the key point is that the complete set of Jucys-Murphy elements generates the subalgebra of elements that are diagonal in all representations of $S_n$. By extreme combinatorial cleverness, you can see standard Young tableaux in the spectra of these operators via a clever translation.
Nov
25
comment Okounkov-Vershik approach to representation theory of $S_n$
don't you need to throw in the center of $\mathbb Q[S_{n-1}]$?
Nov
21
answered Is the Frattini subgroup of a free profinite group trivial?
Nov
10
comment Do limit groups satisfy Howson's theorem?
I think we have the same answer
Nov
10
answered Do limit groups satisfy Howson's theorem?