Piotr M. Sołtan

  1. Examples of non-compact quantum group actions.

    Authors: Piotr M. Sołtan
    Subjects: Operator Algebras
    Abstract

    We present two examples of actions of non-regular locally compact quantum
    groups on their homogeneous spaces. The homogeneous spaces are defined in a way
    specific to these examples, but the definitions we use have the advantage of
    being expressed in purely $\mathrm{C}^*$-algebraic language. We also discuss
    continuity of the obtained actions. Finally we describe in detail a general
    construction of quantum homogeneous spaces obtained as quotients by compact
    quantum subgroups.

  2. When is a quantum space not a group?.

    Authors: Piotr M. Sołtan
    Subjects: Operator Algebras
    Abstract

    We give a survey of techniques from quantum group theory which can be used to
    show that some quantum spaces (objects of the category dual to the category of
    $\mathrm{C}^*$-algebras) do not admit any quantum group structure. We also
    provide a number of examples which include some very well known quantum spaces.
    Our tools include several purely quantum group theoretical results as well as
    study of existence of characters and traces on $\mathrm{C}^*$-algebras
    describing the considered quantum spaces as well as properties such as
    nuclearity.

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