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Apr
22
answered Topologies for which $\mathcal{M}(X)\otimes \mathcal{M}(Y)$ is dense in $\mathcal{M}(X\times Y)$
Apr
19
comment Quantum mechanics formalism and C*-algebras
I bet, $F^*$-algebras will not save quantum mechanics, but stereotype ones will do: arxiv.org/abs/1303.2424 :)
Mar
23
comment What are the applications of operator algebras to other areas?
Sébastien, the problem exists. Not only in this concrete field, but in many fields in mathematics. You were right when asking this question, this is a normal reaction of a human (contrary to robot). The discussions like this must be common in science, otherwise this activity turns into a religion (where references to "tone" replace doubts :).
Mar
22
comment What are the applications of operator algebras to other areas?
Nice to hear this from a specialist in operator algebras. :) When at the Last Judgment we will be accused of snobbery, we will point at Sébastien Palcoux and say: "Here's a conscientious man among us!"
Feb
16
asked Quotient groups of “Abelian-times-compact”, what are they called?
Feb
7
comment Which group algebras in analysis are “true group algebras”?
And are there other constructions? Will $W^*(G)$ be initial object anywhere?
Feb
7
comment Which group algebras in analysis are “true group algebras”?
Ah, OK! That's interesting... What is the problem in the non-discrete case?
Feb
7
comment Which group algebras in analysis are “true group algebras”?
So as far as I understand, for the case of discrete $G$ you and Tobias suggest two examples: 1) $C^*(G)$ will be an initial object in the category of unitary representations of $G$ in C*-algebras, and 2) $\ell^1(G)$ will be an initial object in the category of representations of $G$ in Banach algebras. Is it correct?
Feb
7
comment Which group algebras in analysis are “true group algebras”?
As to unitality, I would bear (you could appreciate this, by the way!), if there would exist some constructions of group algebras with this universality property in some categories of ``representations in non-unital algebras''.
Feb
7
comment Which group algebras in analysis are “true group algebras”?
Yemon, yes if $L^1(G)$ or $C^*(G)$ could be characterized as initial objects, that would be interesting. I suppose, you mean initial object in some ``category of representations of $G$''? I did not understand, are $C^*(G)$ or $\ell^1(G)$ such an initial objects for discrete $G$?
Feb
7
revised Which group algebras in analysis are “true group algebras”?
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Feb
7
asked Which group algebras in analysis are “true group algebras”?
Jan
31
revised A generalization of real characters on a group
I found a mistake in one of the identities
Jan
26
comment Trigonometric polynomials on non-compact and non-abelian groups
Yes! I indeed need a reference, so if somebody could write something about this, it would be great! :)
Jan
26
comment What are the reasons for considering rings without identity?
$M(\mathbb T)$ is a good illustration: if you want to have a Banach algebra, then you get $M(\mathbb T)$, and this is neither a Hopf algebra, nor a group algebra. But if you allow your algebras to be just stereotype, the very same space of measures $M(\mathbb T)$, with the same multiplication (but with another topology) turns into a stereotype Hopf algebra ${\mathcal C}^\star(\mathbb T)$ which is a group algebra.
Jan
26
comment Trigonometric polynomials on non-compact and non-abelian groups
Yemon, could you, please, make a little paper from this (for example, in arxiv), so that I could cite it? A separate request: if ${\tt Trig}(G)$ is not an algebra even for Moore groups, then this should be mentioned there, because this is an important proposition for me.
Jan
26
comment What are the reasons for considering rings without identity?
Yemon, I don't understand you. Does anybody consider $\ell^1({\mathbb T})$? The stereotype theory suggests several natural group algebras, in particular, the algebra of measures ${\mathcal C}^\star(G)$, the algebra of distributions ${\mathcal E}^\star(G)$, etc., and they are all Hopf algebras in contrast to $L^1(G)$. The full measure algebra $M({\mathbb T})$ is unital, but it is not a Hopf algebra and not a group algebra, since it does not generate equivalence between representations (of $\mathbb T$ and of $M({\mathbb T})$).
Jan
26
revised What are the reasons for considering rings without identity?
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Jan
25
revised What are the reasons for considering rings without identity?
added 45 characters in body
Jan
25
revised What are the reasons for considering rings without identity?
added 69 characters in body