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C*-simplicity of locally compact Powers groups

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Veröffentlicht/Copyright: 29. Juli 2016

Abstract

In this article we initiate research on locally compact C*-simple groups. We first show that every C*-simple group must be totally disconnected. Then we study C*-algebras and von Neumann algebras associated with certain groups acting on trees. After formulating a locally compact analogue of Powers’ property, we prove that the reduced group C*-algebra of such groups is simple. This is the first simplicity result for C*-algebras of non-discrete groups and answers a question of de la Harpe. We also consider group von Neumann algebras of certain non-discrete groups acting on trees. We prove factoriality, determine their type and show non-amenability. We end the article by giving natural examples of groups satisfying the hypotheses of our work.

Funding statement: The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement No. 622322.

Acknowledgements

We want to thank Alain Valette for his hospitality at the University of Neuchâtel, where part of this work was done. We are grateful to Pierre-Emmanuel Caprace for useful comments on groups acting on trees. We thank Siegfried Echterhoff for asking us whether C*-simple groups are totally disconnected and for a helpful discussion about this question. Further we thank Hiroshi Ando, Pierre de la Harpe, Pierre Julg and Stefaan Vaes for useful comments on the first version this article. Finally, we thank the anonymous referee his comments and for suggesting an easier proof of Theorem 6.1.

References

[1] S. Adams and W. Ballmann, Amenable isometry groups of Hadamard spaces, Math. Ann. 312 (1998), no. 1, 183–195. 10.1007/s002080050218Suche in Google Scholar

[2] M. Bekka, M. Cowling and P. de la Harpe, Simplicity of the reduced C*-algebra of PSL(n,), Int. Math. Res. Not. IMRN 1994 (1994), no. 7, 285–291. 10.1155/S1073792894000322Suche in Google Scholar

[3] B. Bekka, P. de la Harpe and A. Valette, Kazhdan’s property (T), New Math. Monogr. 11, Cambridge University Press, Cambridge 2008. 10.1017/CBO9780511542749Suche in Google Scholar

[4] J. Bernstein, All reductive p-adic groups are of type I, Funct. Anal. Appl. 8 (1974), 91–93. 10.1007/BF01078592Suche in Google Scholar

[5] E. Breuillard, M. Kalantar, M. Kennedy and N. Ozawa, C*-simplicity and the unique trace property for discrete groups, preprint (2014), http://arxiv.org/abs/1410.2518. Suche in Google Scholar

[6] A. Connes, Une classification des facteurs de type III, Ann. Sci. Éc. Norm. Supér. (4) 6 (1973), 133–252. 10.24033/asens.1247Suche in Google Scholar

[7] A. Connes, Classification des facteurs, Operator algebras and applications (Kingston 1980), Proc. Sympos. Pure Math. 38. Part 2, American Mathematical Society, Providence (1982), 43–109. 10.1090/pspum/038.2/679497Suche in Google Scholar

[8] P. de la Harpe, Reduced C*-algebras of discrete groups which are simple with a unique trace, Operator algebras and their connections with topology and ergodic theory (Buşteni 1983), Lecture Notes in Math. 1132, Springer, Berlin (1985), 230–253. 10.1007/BFb0074887Suche in Google Scholar

[9] P. de la Harpe, On simplcity of reduced C*-algebras of groups, Bull. Lond. Math. Soc. 39 (2007), 1–26. 10.1112/blms/bdl014Suche in Google Scholar

[10] P. de la Harpe and J.-P. Préaux, C*-simple groups: Amalgamated free products, HNN extensions, and fundamental groups of 3-manifolds, J. Topol. Anal. 3 (2011), no. 4, 451–489. 10.1142/S1793525311000659Suche in Google Scholar

[11] J. Dixmier, C*-algebras, North-Holland, Amsterdam 1977. Suche in Google Scholar

[12] J. M. Fell, The dual spaces of C*-algebras, Trans. Amer. Math. Soc. 94 (1960), no. 3, 365–403. 10.1090/S0002-9947-1960-0146681-0Suche in Google Scholar

[13] A. Figà-Talamanca and C. Nebbia, Harmonic analysis and representation theory for groups acting on homogeneous trees, London Math. Soc. Lecture Note Ser. 162, Cambridge University Press, Cambridge 1991. 10.1017/CBO9780511662324Suche in Google Scholar

[14] J. Glimm, Type IC*-algebras, Ann. of Math. (2) 73 (1961), 572–612. 10.2307/1970319Suche in Google Scholar

[15] U. Haagerup, A new look at C*-simplicity and the unique trace property of a group, preprint (2015), http://arxiv.org/abs/1509.05880. Suche in Google Scholar

[16] Harish-Chandra, Discrete series for semisimple Lie groups. II. Explicit determination of the characters, Acta Math. 116 (1966), 1–111. 10.1007/BF02392813Suche in Google Scholar

[17] A. Ioana, S. Popa and S. Vaes, A class of superrigid group von Neumann algebras, Ann. of Math. (2) 178 (2013), 231–286. 10.4007/annals.2013.178.1.4Suche in Google Scholar

[18] I. Kaplansky, The structure of certain operator algebras, Trans. Amer. Math. Soc. 70 (1951), 219–255. 10.1090/S0002-9947-1951-0042066-0Suche in Google Scholar

[19] M. Kennedy, Characterizations of C*-simplicity, preprint (2015), http://arxiv.org/abs/1509.01870. Suche in Google Scholar

[20] J. Kustermans, KMS-weights on C*-algebras, preprint (1997), https://arxiv.org/abs/funct-an/9704008. Suche in Google Scholar

[21] J. Kustermans and S. Vaes, Weight theory for C*-algebraic quantum groups, preprint (1999), http://arxiv.org/abs/math/9901063. Suche in Google Scholar

[22] A. Le Boudec, C*-simplicity and the amenable radical, preprint (2015), http://arxiv.org/abs/1507.03452. Suche in Google Scholar

[23] W. Lück, L2-invariants and their applications to geometry, group theory and spectral theory, Ergeb. Math. Grenzgeb. (3) 44, Springer, Berlin 2001. 10.1007/978-3-642-56478-9_42Suche in Google Scholar

[24] G. W. Mackey, Induced representations of locally compact groups I, Ann. of Math. (2) 55 (1952), no. 1, 101–139. 10.2307/1969423Suche in Google Scholar

[25] D. McDuff, Uncountably many II1 factors, Ann. of Math. (2) 90 (1969), 372–377. 10.2307/1970730Suche in Google Scholar

[26] S. Murakami, On the automorphisms of a real semi-simple Lie algebra, J. Math. Soc. Japan 4 (1952), no. 2, 103–133. 10.2969/jmsj/00420103Suche in Google Scholar

[27] R. T. Powers, Simplicity of the C*-algebra associated with the free group on two generators, Duke Math. J. 42 (1975), 151–156. 10.1215/S0012-7094-75-04213-1Suche in Google Scholar

[28] J. Rosenberg, C*-algebras and Mackey’s theory of group representations, C*-algebras: 1943-1993 (San Antonio 1993), Contemp.Math. 167, American Mathematical Society, Providence (1994), 151–181. 10.1090/conm/167/1292014Suche in Google Scholar

[29] M. Takesaki, Theory of operator algebras II, Springer, Berlin 2003. 10.1007/978-3-662-10451-4Suche in Google Scholar

[30] K. Tzanev, Hecke C*-algebras and amenability, J. Operator Theory 50 (2003), no. 1, 169–178. Suche in Google Scholar

[31] D. van Dantzig, Zur topologischen Algebra. III. Brouwersche und Cantorsche Gruppen, Compos. Math. 3 (1936), 408–426. Suche in Google Scholar

Received: 2015-06-25
Revised: 2016-01-08
Published Online: 2016-07-29
Published in Print: 2019-03-01

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