Let G 4 be the unique, connected, simply connected, four-dimensional, nilpotent Lie group. In this paper, the discrete cocompact subgroups H of G 4 are classified and shown to be in 1-1 correspondence with triples p 1 p 2 p 3 β 3 that satisfy p 2 p 3 > 0 and a certain restriction on p 1 . The K-grou
Strength of Convergence in Duals of C*-Algebras and Nilpotent Lie Groups
β Scribed by R.J. Archbold; E. Kaniuth; J. Ludwig; G. Schlichting; D.W.B. Somerset
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 284 KB
- Volume
- 158
- Category
- Article
- ISSN
- 0001-8708
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β¦ Synopsis
By using trace formulae, the recent concept of upper multiplicity for an irreducible representation of a C*-algebra is linked to the earlier notion of strength of convergence in the dual of a nilpotent Lie group G. In particular, it is shown that if ? # G has finite upper multiplicity then this integer is the greatest strength with which a sequence in G can converge to ?. Upper multiplicities are calculated for all irreducible representations of the groups in the threadlike generalization of the Heisenberg group. The values are computed by combining new C*-theoretic results with detailed analysis of the convergence of coadjoint orbits and they show that every positive integer occurs for this class of groups.
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