Oberseminar Geometrie, Topologie und Analysis

H. Geiges, A. Lytchak, G. Marinescu, S. Sabatini

Wintersemester 2017/18

Freitag, 10:30-11:30, Seminarraum 2 (Raum 204)

6.10.17 BHKM Seminar in Köln

20.10.17 Filip Misev (Marseille)
The stabilisation height of fibre surfaces

Abstract: Fibre surfaces are embedded surfaces with boundary which arise as pages of open books for the three-sphere. The simplest examples are the standard disc and the Hopf bands (embedded annuli with a full twist). Using a special operation called plumbing, fibre surfaces can be glued together to form new ones. Call a fibre surface "stable" if it can be obtained from the disc by iterated plumbing of Hopf bands. The stabilisation height measures (in terms of Hopf plumbing) how far a fibre surface is from being stable. We will show that the stabilisation height is unbounded, even among fibre surfaces of fixed genus. (Joint work with S. Baader.)
3.11.17 Joint Seminar on Complex Algebraic Geometry and Complex Analysis in Bochum

BHKM Seminar in Bochum

17.11.17 Ivan Izmestiev (Fribourg)
Ivory's theorem: old and new

Abstract: Ivory's lemma states that the diagonals of a curvilinear quadrilateral bounded by confocal conics (and more generally, the great diagonals of a domain bounded by confocal quadrics) have equal lengths. This lemma is used in the proof of Ivory's theorem about the potential of an equilibrium charge on an ellipsoid. In this talk, based on a joint work with Sergey Tabachnikov, we will review Blaschke's characterization of coordinate nets that satisfy Ivory's lemma and will generalize Ivory's theorem to the potential of ellipsoidal layers in the spherical and hyperbolic space.
BHKM Seminar in Münster

8.12.17 Nina Lebedeva (St. Petersburg/Münster)

15.12.17 Sebastian Durst
Fakultätsöffentliche Disputation

12.1.18 Martin Kerin (Münster)

H. Geiges, 5.4.02