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15 votes
1 answer
1k views

Gelfand-Naimark from the category-theoretic point of view

I was thinking about the Gelfand-Naimark theorem asserting the isometric * isomorphism between a commutative $C^*$-algebra (with unit) $\mathcal{A}$ and the $C^*$ -algebra of continuous complex-valued ...
3 votes
0 answers
132 views

Takesaki's duality in representation theory of $C^*$-algebras

In M.Takesaki's 1967 article titled A Duality in the Representation Theory of C-Algebras*, admissible operator fields are defined in order to generalize Gelfand transform to a non-abelian setting. ...
4 votes
0 answers
189 views

Gelfand's transform for noncommutative $C^*$-algebras

Please excuse me if this is well-known, I am not very familiar with the general theory of $C^*$-algebras. Let $A$ be a unital separable liminal $C^*$-algebra (in the case I am interested in, ...
1 vote
0 answers
283 views

Continuous fields of Hilbert spaces arising from representations of abelian C*-algebras

This is a followup to a previous question [1] on MO. Let $X$ be a second-countable, locally compact, Hausdorff space, and let $\mathscr H =\{H_x\}_{x\in X}$, be a measurable field of Hilbert spaces ...
2 votes
0 answers
116 views

General construction of enveloping C*-algebra, left/right-regular representation, etc

In a number of contexts (e.g. groups, crossed products, groupoids, Fell bundles) there are similar constructions of enveloping C*-algebras and left/right-regular representations that incorporate ...
2 votes
1 answer
645 views

Enveloping $C^*$-algebra

Consider a finite dimensional $C^*$-algebra $\cal{A}$. Is there any enveloping $C^*$-algebra $\cal{C^*(G)}$ such that $\cal{A}\cong C^*(G)$ for some locally compact group $\cal{G}$? (Note that "$\...
2 votes
1 answer
122 views

Why is the ker-hull-topology on $Irr(A)$ is the discrete topology?

Let $A$ be a C$^*$-algebra. Let $Irr(A)=\{[\pi]: \pi$ is an irreducible representation of A}, here is $\rho\in [\pi]$ if there is an unitary operator $V:H_{\pi}\to H_{\rho}$ such that $V\pi(a)=\rho(a)...
7 votes
1 answer
572 views

What is $\hat{A}=\{[\pi]:\pi$ is a irreducible representation of $A$} ( $A$ is a $C^*$-algebra)?

Let $A=\{f:[0,1]\to M_2(\mathbb{C}): $f continuous and $ f(0)=\begin{pmatrix} f_{11}(0) & 0 \\ 0 & f_{22}(0) \end{pmatrix}\}$ be a $C^*$-algebra with pointwise multiplication, involutions and ...