Trimester Seminar
Venue: HIM lecture hall, Poppelsdorfer Allee 45
Organizers: Alex Eskin, Ursula Hamenstädt, Maxim Kontsevich, Martin Möller, Jean-Christophe Yoccoz and Anton Zorich
Tuesday, May 11
15:00 Vincent Delecroix and Samuel Lelièvre: Knowledge sharing - Demonstration of Sage, an open-source, free, collaborative computer algebra system
Tuesday, May 18
15:00 Alex Wright: Knowledge sharing - Smillie's Theorem (translation surfaces whose orbit under SL2(R) is closed are Veech surfaces)
16:30 Thierry Monteil: Knowledge sharing - Masur criterion (translation surfaces whose orbit under the geodesic flow is non-divergent have a uniquely ergodic vertical flow)
Thursday, May 20
16:30 Anna Lenzhen: Shape of a ball in Teichmüller space
Friday, May 21
14:00 Chris Judge: Introductory informal talk about Delaunay/Voronoi triangulation and tessellations
Wednesday, May 26
14:00 Alex Eskin: Introductory informal talk about random walks on groups and random transformations
Thursday, May 27
16:30 Chris Judge: Tessellations induced by quadratic differentials
Friday, May 28
15:15 Samuel Lelievre: Knowledge sharing - Combinatorics of square-tiled surfaces and geometry of their Teichmüller curve
Friday, June 4
14:15 Erwan Lanneau: Knowledge sharing - The Arnoux-Yoccoz surface
Thursday, June 10
16:30 Gabriela Schmidthuesen: Veech groups of infinite staircases
Friday, June 11
14:00 Pat Hooper: Knowledge sharing - Triangle groups as Veech groups
15:00 Alex Eskin: Semisimplicity of the Lyapunov spectrum
Thursday, July 8
16:30 Nikita Selinger: Oberseminar Differential Geometry - On the Boundary Behaviour of Thurston's Pull-back Map
Monday, July 12
11:00 Informal seminar on flows of SL(2,R)-type
Tuesday, July 13
16:30 Corinna Ulcigrai: Informal seminar - IETs techniques for absence of mixing in area-preserving flows
Thursday, July 15
11:00 Corentin Boissy: Two definitions of Rauzy Classes
16:30 Joshua Bowman: Oberseminar Differential Geometry - Singularities of non-compact translation surfaces
Friday, July 16
14:00 Vincent Delecroix: The wind-tree model (dynamic in a billiard of infinite area)
Tuesday, July 20
16:30 John Smillie: Compactification of strata
Wednesday, July 21
16:30 Vincent Delecroix: Sage advertisement session (open source math software)
Thursday, July 22
11:00 Inkang Kim: On character variety of free group representations in PSL(2,C)
Abstract: I want to discuss about geometrically infinite hyperbolic handlebodies which are primitive stable
Tuesday, July 27
16:30 Ken'ichi Ohshika: Algebraic limits viewed through geometric limits
Abstract: We consider a sequence of quasi-Fuchsian groups Gi. In general, it was not easy to determine its algebraic limit even when we know it converges. We shall show how we can determine the algebraic limit from the conformal structures at infinity of Gi.
Thursday, August 10
16:30 Ken'ichi Ohshika: Necessary sufficient conditions for primitive stability
Abstract: We shall give necessary sufficient conditions for Kleinian groups on the boundary of Schottky spaces to be primitive stable in the sense of Minsky.
Thursday, August 17
16:30 Ara Basmajian: Universal Length bounds for self-intersecting closed geodesics
Abstract: We investigate the relationship, in various contexts, between a closed geodesic with self-intersection number k (for brevity, called a k-geodesic) and its length. The length of a k-geodesic on any hyperbolic surface is known to be bounded from below by a constant that goes to infinity with k. We show that the optimal constants grow like log k. Moreover, we show that for each natural number k, there exists a hyperbolic surface where the optimal constant is realized as the length of a k-geodesic. This was previously known for k=1, where the optimal constant is realized by the length of the figure eight on the thrice punctured sphere.
Thursday, August 24
16:30 Shinpei Baba: 2π-graftings on complex projective structures
Abstract: A complex projective structure is a certain geometric structure on a surface, which is a generalization of a hyperbolic structure. A complex projective structure comes with a holonomy representation of the surface group into PSL(2,C). On the other hand, such a fixed representation may correspond to infinitely many different projective structures. We show that 2π-graftings, a certain surgery operation, generate this class of projective structures, under the assumption that the fixed representation is generic one in the character variety.