Nov 20, 2009 
talk "Recent progress on the Atiyah Conjecture", Seminar "Géométrie Non Commutative et Physique Théorique", Institut de Mathématiques de Luminy. Invited by Michael Puschnigg. 
May 4, 2010 
talk "On Turing machines, dynamical systems and the Atiyah problem", Seminar "Algebra and Geometry", Mathematisches Institut, Universität Leipzig. Invited by Andreas Thom. 
June 14, 2010 
talk "On Turing machines, dynamical systems and the Atiyah problem", Oberseminar Topologie, Mathematisches Institut der WWU Münster. Invited by Arthur Bartels. 
Sep 5  Sep 11, 2010 
talk "On the Atiyah problem for the lamplighter groups" at the workshop "Actions and Invariants of Residually Finite Groups: Asymptotic Methods", Mathematisches Forschungsinstitut Oberwolfach. 
Nov 1719, 2010 
talk in Operator algebra seminar, Leuven, Belgium. Invitation of Stefaan Vaes.

Nov 2527, 2010 
talk in the StrukturtheorieSeminar: "Turing machines and measurable graphings",TU Graz, Austria. Invitation of Franz Lehner 
January 4, 2011  talk "Measured groupoids as a tool for spectral
computations in certain group rings" in Oberseminar Algebra & Geometrie,
Leipzig. Invited by Andreas Thom.

January 21, 2011 
talk in the LaWiNe seminar. Invited by Alain Valette

June 1924, 2011 
talk at the conference Groups, graphs and stochastic processes, Banff, Canada 