Introduction to compact and discrete quantum groups

Quasi-Discrete Locally Compact Quantum Groups

Let A be a C *-algebra. Let A ⊗ A be the minimal C *-tensor product of A with itself and let M (A ⊗ A) be the multiplier algebra of A ⊗ A. A comultiplication on A is a non-degenerate *-homomorphism ∆ : A → M (A ⊗ A) satisfying the coassociativity law (∆ ⊗ ι)∆ = (ι ⊗ ∆)∆ where ι is the identity map and where ∆ ⊗ ι and ι ⊗ ∆ are the unique extensions to M (A ⊗ A) of the obvious maps on A ⊗ A. We ...

Introduction to Compact Transformation Groups

Characterizations of compact and discrete quantum groups through second duals

A locally compact group G is compact if and only if L(G) is an ideal in L(G), and the Fourier algebra A(G) of G is an ideal in A(G)∗∗ if and only if G is discrete. On the other hand, G is discrete if and only if C0(G) is an ideal in C0(G)∗∗. We show that these assertions are special cases of results on locally compact quantum groups in the sense of J. Kustermans and S. Vaes. In particular, a vo...

Compact quantum groups

In this paper we review the theory of compact quantum groups.

Integration over Compact Quantum Groups

We find a combinatorial formula for the Haar functional of the orthogonal and unitary quantum groups. As an application, we consider diagonal coefficients of the fundamental representation, and we investigate their spectral measures. Introduction A basic question in functional analysis is to find axioms for quantum groups, which ensure the existence of a Haar measure. In the compact case, this ...