18.11.16	Matthias Nagel (Montréal, z.Zt. HIM Bonn) Concordance invariance of Levine-Tristram signatures of links Abstract: We determine for which complex numbers on the unit circle the Levine-Tristram signature gives rise to link concordance invariants. For this we recast the Levine-Tristram signature as a signature defect and use Cohn localization. This is joint work with Mark Powell.
9.12.16	Thomas Rot (Köln) Classification of homotopy classes of Fredholm maps
16.12.16	Christian Lange (Köln) Topology of complex hyperplane complements
27.1.17	Sinem Onaran (Ankara) Legendrian Lens Space Surgeries Abstract: In this talk, first I will review topological Dehn surgery and its contact analogue, contact surgery. Then I will focus on a question: which tight contact structures on a given lens space can be obtained by a single contact (− 1)-surgery along a Legendrian knot in S3 with some contact structure? I will given an answer to the question for lens spaces L(ns2 − s + 1, s2) with n ≥ 2, s ≥ 1. This work is joint with H. Geiges.
10.2.17	Gerrit Herrmann (Regensburg) The L2-Alexander torsion for Seifert fibre spaces Abstract: Dubois, Friedl and Lück define the L2-Alexander torsion of a 3-manifold. It is a function τ(2)(N,φ)(t) associated to a pair (N,φ), where N is an irreducible 3-manifold and φ is a first cohomology class. I calculate the L2-Alexander torsion for Seifert fibre spaces and graph manifolds in terms of the Thurston norm.

H. Geiges, 5.4.02