Preface; List of participants; 1. Notes on Sela's work: limit groups and Makanin-Razborov diagrams M. Bestvina and M. Feighn; 2. Solutions to Bestvina & Feighn's exercises on limit groups H. Wilton; 3. L2-Invariants from the algebraic point of view W. Lück; 4. Constructing non-positively curved spaces and groups J. McCammond; 5. Homology and dynamics in quasi-isometric rigidity of once-punctured mapping class groups L. Mosher; 6. Hattori-Stallings trace and Euler characteristics for groups I. Chatterji and G. Mislin; 7. Groups of small homological dimension and the Atiyah conjecture P. H. Kropholler, P. Linnell and W. Lück; 8. Logarithms and assembly maps on Kn(Zl[G]) V. P. Snaith; 9. On complete resolutions O. Talelli; 10. Structure theory for branch groups J. S. Wilson.