A von Neumann regular extension of a semiprime ring naturally deenes a epimorphic extension in the category of rings. These are studied, and four natural examples are considered, two in commutative ring theory, and two in rings of continuous functions.

We prove a von Neumann type ergodic theorem for averages of unitary operators arising from the Furstenberg-Poisson boundary representation (the quasi-regular representation) of any lattice in a non-compact connected semisimple Lie group with finite center.

λ(s)δt = δst and ρ(s)δt = δts−1 for s, t ∈ Γ. The reduced group C∗-algebra C∗ λΓ is the C∗-algebra generated by λ, likewise for C∗ ρΓ; C∗ λΓ = λ(CΓ) ‖ ‖ ⊂ B(`2Γ) and C∗ ρΓ = ρ(CΓ) ‖ ‖ ⊂ B(`2Γ). The group von Neumann algebra LΓ is the von Neumann algebra generated by λ; LΓ = λ(CΓ)′′ = ρ(CΓ)′. We sometime use M instead of LΓ, and L2M instead of `2Γ. We denote by τ the canonical tracial state on L...

Zusammenfassung Es wurden zwei empirische Studien durchgeführt. In der einen Studie konnten Internetnutzer ihr Suchverhalten aus ihrer Sicht in einer Online Umfrage beschreiben. Die Fragen orientieren sich an den Ergebnissen früherer Studien und sind durch neue Fragestellungen bei der Online Suche erweitert worden. In der anderen Studie wurden vier weltweit Datensätze von Suchanfragen generiert...

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We prove that certain classes of von Neumann algebras with regular, injective subalgebras are thin. As a consequence, all Hochschild cohomology groups of these algebras are zero. Mathematics subject classification (2010): 46L10, 47A16.

In [15], Kaplansky introduced Baer rings as rings in which every right (left) annihilator ideal is generated by an idempotent. According to Clark [9], a ring R is called quasi-Baer if the right annihilator of every right ideal is generated (as a right ideal) by an idempotent. Further works on quasi-Baer rings appear in [4, 6, 17]. Recently, Birkenmeier et al. [8] called a ring R to be a right (...

form the base of a topology on the Stone spectrum Q(R) such that Q(R) becomes a zero-dimensional, completely regular Hausdorff space. The sets QP (R) are closed-open. If the von Neumann algebra R is abelian, then the Stone spectrum Q(R) is homeomorphic to the Gelfand spectrum Ω(R) of R. For an arbitrary non-abelian unital von Neumann algebra R, the Stone spectrum can hence be regarded as a non-...

We give a new proof of a result of Ozawa showing that if a von Neumann subalgebra Q of a free group factor LFn, 2 ≤ n ≤ ∞ has relative commutant diffuse (i.e. without atoms), then Q is amenable.