# Veranstaltungskalender

 Fr, 03.11.2017, 15:45 Operator algebras, order, and semigroups Mathematisches Kolloquium Referent: Prof. Dr. Karl-Hermann Neeb, Universität Erlangen-Nürnberg Raum: S2|08 /171 (Uhrturm) Festkolloquium anl. des 85. Geburtstags von Prof. Dr. Karl H. Hofmann16:45 Uhr Mathematik-Chor, danach Kaffeepause in S2/08 Raum 71Operator algebras, order and semigroups have been core themes of Karl Hofmann's mathematical work at different times of his life. Here we discuss some current problems at the borderline between mathematics and quantum physics, where these themes play a central role. \\ Concretely, we are interested in the space $Stand(H)$ of so-called standard subspaces of a complex Hilbert space $H$. These are closed real subspaces $V\subseteq H$ satisfying $V \cap i V = \{0\}$ and $\overline{V+ i V} = H$. In Quantum Field Theory standard subspaces encode crucial information on nets of algebras of local observables, but they are much easier to deal with than the operator algebras themselves. Nevertheless they contain most of the information on symmetries. Here a good understanding of the structure of the inclusion order on $Stand(H)$ is an important problem. On possible approach is based on antiunitary representations of finite dimensional Lie groups $G$ on $H$ and the structural information on the subsemigroup $S_V := \{g \in G \: gV \subseteq V\}$.

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Fachbereich Mathematik