Abstract
Let \({\mathbb{G}}\) be a co-amenable compact quantum group. We show that a right coideal of \({\mathbb{G}}\) is of quotient type if and only if it is the range of a conditional expectation preserving the Haar state and is globally invariant under the left action of the dual discrete quantum group. We apply this result to the theory of Poisson boundaries introduced by Izumi for discrete quantum groups and generalize a work of Izumi-Neshveyev-Tuset on SU q (N) for co-amenable compact quantum groups with the commutative fusion rules. More precisely, we prove that the Poisson integral is an isomorphism between the Poisson boundary and the right coideal of quotient type by a maximal quantum subgroup of Kac type. In particular, the Poisson boundary and the quantum flag manifold are isomorphic for any q-deformed classical compact Lie group.
Similar content being viewed by others
References
Baaj S., Skandalis G. (1993). Unitaires multiplicatifs et dualité pour les produits croisé de C *-algèbres. Ann. Sci. École Norm. Sup. (4) 26(4): 425–488
Bédos E., Conti R., Tuset L. (2005). On amenability and co-amenability of algebraic quantum groups and their corepresentations. Canad. J. Math. 57(1): 17–60
Bédos E., Murphy G., Tuset L. (2001). Co-amenability of compact quantum groups. J. Geom. Phys. 40(2): 130–153
Bédos E., Murphy G., Tuset L. (2002). Amenability and coamenability of algebraic quantum groups. Int. J. Math. Math. Sci. 31(10): 577–601
Connes A. (1980). On the spatial theory of von Neumann algebras. J. Funct. Anal. 35(2): 153–164
Effros E., Ruan Z.-J. (1994). Discrete quantum groups. I. The Haar measure. Internat. J. Math. 5(5): 681–723
Enock, M., Schwartz, J. M.: Kac algebras and duality of locally compact groups. Berlin: Springer-Verlag, 1992, pp. x+257
Haagerup U. (1979). Operator-valued weights in von Neumann algebras. I. J. Funct. Anal. 32(2): 175–206
Haagerup U. (1979). Operator-valued weights in von Neumann algebras. II. J. Funct. Anal. 33(3): 339–361
Izumi M. (2002). Non-commutative Poisson boundaries and compact quantum group actions. Adv. Math. 169(1): 1–57
Izumi M., Longo R., Popa S. (1998). A Galois correspondence for compact groups of automorphisms of von Neumann algebras with a generalization to Kac algebras. J. Funct. Anal. 155(1): 25–63
Izumi M., Neshveyev S., Tuset L. (2006). Poisson boundary of the dual of SU q (n). Commun. Math. Phys. 262(2): 505–531
Kosaki H. (1986). Extension of Jones’ theory on index to arbitrary factors. J. Funct. Anal. 66(1): 123–140
Kosaki, H.: Type III factors and index theory. Lecture Notes Series 43, Seoul: Seoul National University, Research Institute of Mathematics, Global Analysis Research Center, 1998, pp. ii+96
Korogodski, L.I., Soibelman, Y.S.: Algebras of functions on quantum groups. Part I. Mathematical Surveys and Monographs 56, Providence, RI: Amer. Math. Soc. 1998, pp. x+150
Kustermans J., Vaes S. (2003). Locally compact quantum groups in the von Neumann algebraic setting. Math. Scand. 92(1): 68–92
Neshveyev S., Tuset L. (2004). The Martin boundary of a discrete quantum group. J. Reine Angew. Math. 568: 23–70
Podleś P. (1987). Quantum spheres. Lett. Math. Phys. 14(3): 193–202
Podleś P. (1995). Symmetries of quantum spaces. Subgroups and quotient spaces of quantum SU(2) and SO(3) groups. Commun. Math. Phys. 170(1): 1–20
Sołtan P.M. (2005). Quantum Bohr compactification. Illinois J. Math. 49(4): 1245–1270
Takesaki M. (1972). Conditional expectations in von Neumann algebras. J. Funct. Anal. 9: 306–321
Tomatsu R. (2006). Amenable discrete quantum groups. J. Math. Soc. Japan 58(4): 949–964
Tomatsu, R.: Compact quantum ergodic systems. http://arxiv.org/list/math.OA/0412012, 2004
Vaes S. (2001). The unitary implementation of a locally compact quantum group action. J. Funct. Anal. 180(2): 426–480
Vaes, S., Vander Vennet, N.: Identification of the Poisson and Martin boundaries of orthogonal discrete quantum groups. http://arxiv.org/list/math.OA/0605489, 2006
Vaes, S., Vergnioux, R.: The boundary of universal discrete quantum groups, exactness and factoriality. http://arxiv.org/list/math.OA/0509706, 2005
Van Daele A. (1996). Discrete quantum groups. J. Algebra 180(2): 431–444
Woronowicz S.L. (1987). Compact matrix pseudogroups. Commun. Math. Phys. 111(4): 613–665
Woronowicz S.L. (1988). Tannaka-Kreĭn duality for compact matrix pseudogroups. Twisted SU(N) groups. Invent. Math. 93(1): 35–76
Woronowicz, S.L.: Compact quantum groups. In: Symétries quantiques (Les Houches, 1995), Amsterdam: North-Holland, 1998, pp. 845–884
Yamagami S. (1995). On unitary representation theories of compact quantum groups. Commun. Math. Phys. 167(3): 509–529
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by Y. Kawahigashi
Rights and permissions
About this article
Cite this article
Tomatsu, R. A Characterization of Right Coideals of Quotient Type and its Application to Classification of Poisson Boundaries. Commun. Math. Phys. 275, 271–296 (2007). https://doi.org/10.1007/s00220-007-0267-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00220-007-0267-6