In this paper, we introduce a property of topological dynamical systems that we call finite dynamical complexity. For systems with this property, one can in principle compute the K-theory of the associated crossed product C*-algebra by splitting it up into simpler pieces and using the methods of controlled K-theory. The main part of the paper illustrates this idea by giving a new proof of the Baum-Connes conjecture for actions with finite dynamical complexity. We have tried to keep the paper as self-contained as possible: we hope the main part will be accessible to someone with the equivalent of a first course in operator K-theory. In particular, we do not assume prior knowledge of controlled K-theory, and use a new and concrete model for the Baum-Connes conjecture with coefficients that requires no bivariant K-theory to set up.
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K-homology and K-theory for pure braid groups
We produce an explicit description of the K-theory and K-homology of the pure braid group on n strands. We describe the Baum–Connes correspondence between the generators of the left- and right-hand sides for n = 4. Using functoriality of the assembly map and direct computations, we recover Oyono-Oyono’s result on the Baum–Connes conjecture for pure braid groups [24]. We also discuss the case of the full braid group on 3-strands.
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- Award ID(s):
- 1928930
- PAR ID:
- 10420186
- Date Published:
- Journal Name:
- New York journal of mathematics
- Volume:
- 28
- ISSN:
- 1076-9803
- Page Range / eLocation ID:
- 1256-1294
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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In this paper, we introduce a property of topological dynamical systems that we call finite dynamical complexity. For systems with this property, one can in principle compute the K-theory of the associated crossed product C*-algebra by splitting it up into simpler pieces and using the methods of controlled K-theory. The main part of the paper illustrates this idea by giving a new proof of the Baum-Connes conjecture for actions with finite dynamical complexity. We have tried to keep the paper as self-contained as possible: we hope the main part will be accessible to someone with the equivalent of a first course in operator K-theory. In particular, we do not assume prior knowledge of controlled K-theory, and use a new and concrete model for the Baum-Connes conjecture with coefficients that requires no bivariant K-theory to set up.more » « less
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