Talks and events

[edit]

Upcoming talks

[oberseminar] Wed 01.03.2017, Math II (Lonza) at 10h20

Mickaël Kourganoff (Grenoble): Anosov geodesic flows, billiards and embedded surfaces

Consider an ellipsoid and make one of its axes tend to zero: the ellipsoid flattens and tends to an ellipse in the plane formed by the two other axes. As Birkhoff had noticed, the geodesic flow on the ellipsoid converges to the billiard flow on the ellipse. In fact, this phenomenon is far more general: we will see that it applies to almost any surface in R3 which is flattened along an axis. Moreover, if the billiard obtained at the limit is dispersing, under some mild conditions, then the geodesic flow on the surface is Anosov (then the two systems display the same type of chaotic behavior). This theorem allows us to obtain a concrete example of Anosov physical system: a linkage with 5 rods. Finally, with a new version of the theorem which applies, this time, to non-flat billiards, we obtain examples of surfaces with a small genus, with Anosov geodesic flow, isometrically embedded in the sphere S3.

[colloque] Tue 7.3.2017, Phys 2.52 at 17h15

Prof. Sergei Tabachnikov (Pennsylvania State University): Skewers

The skewer of a pair of skew lines in space is their common perpendicular. To configuration theorems of plane projective geometry involving points and lines (such as Pappus or Desargues) there correspond configuration theorems in space: points and lines in the plane are replaced by lines is space, the incidence between a line and a point translates as the intersection of two lines at right angle, and the operations of connecting two points by a line or by intersecting two lines at a point translate as taking the skewer of two lines. These configuration theorems hold in elliptic, Euclidean, and hyperbolic geometries.
This correspondence principle extends to plane configuration theorems involving polarity. For example, the theorem that the three altitudes of a triangle are concurrent corresponds to the Petersen-Morley theorem that the common normals of the opposite sides of a space right-angled hexagon have a common normal.
I shall also discuss the skewer versions of the Sylvester problem: given a finite collection of pairwise skew lines such that the skewer of any pair intersects at least one other line at right angle, do all the line have to share a skewer? The answer is positive in the elliptic and Euclidean geometries, but negative in the hyperbolic one.

[colloque] Tue 14.3.2017, Phys 2.52 at 17h15

Prof. Philipp Habegger (Uni Basel): Complex Multiplication or is $e^{\pi \sqrt{163}}$ an Integer?

Roots of unity are algebraic values of the exponential function at rational arguments shifted by $\pi i$. Kronecker's Jugendtraum was to find analytic functions that mimic this behavior for algebraic numbers of higher degree. The theory of complex multiplication of elliptic curves provides a rich trove of examples of such functions with many surprising symmetries. It originated in the 19th century in work of Kronecker and Weber and underwent a remarkable development in the 20th century by Hilbert, Shimura, Deligne and many others.
In this talk I will provide a glimpse into some classical aspects of complex multiplication from a diophantine point of view. Then I will discuss recent questions connected to problems in diophantine geometry, some of them are joint work with Jonathan Pila.

[colloque] Tue 21.3.2017, Phys 2.52 at 17h15

Prof. Jan Draisma (Uni Bern): tba

[colloque] Tue 25.4.2017, Phys 2.52 at 17h15

Prof. Antti Knowles (Uni Genève): tba

[colloque] Tue 16.5.2017, Phys 2.52 at 17h15

Prof. Pierre Nolin (ETHZ): tba

Archive:

Colloquia in the current semester

[colloque] Tue 1.3.2016, Phys 2.52 at 17h15 - Festvortrag zum 80. Geburtstag von Ernst Ruhmore

Prof. Dr. Ernst Heintze (Uni Augsburg): Affine root systems and submanifolds of Hilbert spaces

[colloque] Tue 8.3.2016, Phys 2.52 at 17h15more

Prof. Joan Porti (Barcelona): Reidemeister torsion and hyperbolic 3-manifolds

[colloque] Tue 22.3.2016, Phys 2.52 at 17h15more

Prof. Uwe Semmelmann (Uni. Stuttgart): Invariant 4-forms and exceptional Lie algebras

[colloque] Tue 12.4.2016, Phys 2.52 at 17h15more

Prof. Dr. Benjamin Sudakov (ETH Zürich): Induced matchings, arithmetic progressions and communication

[colloque] Tue 19.4.2016, Phys 2.52 at 17h15more

Prof. Christophe Bavard (Bordeaux): Points conjugués en géométrie riemannienne et lorentzienne

[colloque] Tue 26.4.2016, Phys 2.52 at 17h15more

Prof. Roman Sauer (KIT): Invariant random subgroups

[colloque] Tue 3.5.2016, Phys 2.52 at 17h15more

Prof. Hans Josef Pesch (Uni Bayreuth): Optimal Control of Dynamical Systems Governed by Partial Differential Equations

[colloque] Tue 10.5.2016, Phys 2.52 at 17h15more

Prof. Sergiu Moroianu (Bucharest): Renormalized volume in hyperbolic geometry

[colloque] Tue 17.5.2016, Phys 2.52 at 17h15more

Prof. Vincent Beffara (CNRS Grenoble): Introduction to the Schramm-Loewner Evolution

[colloque] Tue 24.5.2016, Phys 2.52 at 17h15more

Dr. Roger Zuest (Fribourg): Regularity theory for almost minimal surfaces

[colloque] Tue 31.5.2016, Phys 2.52 at 17h15more

Prof. Wolfgang Lück (Universität Bonn / HIM Bonn): Introduction to $L^2$-Betti numbers

[colloque] Tue 7.6.2016, Phys 2.52 at 15h30more

Prof. Alexandru Suciu (Northeastern University, Boston): Fundamental groups in algebraic geometry and three-dimensional topology

[colloque] Tue 20.9.2016, Phys 2.52 at 17h15more

Prof. Daniel Grieser (Universität Oldenburg): A look at triangles from elementary geometry, spectral theory and singular analysis

[colloque] Tue 27.9.2016, Phys 2.52 at 17h15more

Prof. Christoph Böhm (Universität Münster): Immortal homogeneous Ricci flows

[colloque] Tue 11.10.2016, Phys 2.52 at 17h15more

Prof. Gerhard Opfer (Universität Hamburg): Zeros of unilateral quaternionic and coquaternionic polynomials

[colloque] Tue, 25.10.2016, Phys 2.52 at 17h15more

Dr. Wim Hordijk (Konrad Lorenz Institut, Klosterneuburg): Autocatalytic Sets: The Origin and Organization of Life

[colloque] Tue 8.11.2016, Phys 2.52 at 17h15more

Prof. Manfred Lehn (JG Universität Mainz): The theorem of Grothendieck-Brieskorn-Slodowy and symplectic singularities

[colloque] Tue 15.11.2016, Phys 2.52 at 17h15more

Prof. Nicolas Curien (Université Paris-Sud Orsay): A panoramic introduction to random planar maps

[colloque] Tue 22.11.2016, Phys 2.52 at 17h15more

Prof. Masahiko Yoshinaga (Hokkaido University): Characteristic polynomials of hyperplane arrangements

[colloque] Tue 6.12.2016, Phys 2.52 at 17h15more

Prof. Priyam Patel (UCSB): Quantitative methods in hyperbolic geometry

[colloque] Tue 13.12.2016, Phys 2.52 at 17h15more

Prof. Christophe Soulé (IHES): La théorie d'Arakelov

[colloque] Tue 7.3.2017, Phys 2.52 at 17h15more

Prof. Sergei Tabachnikov (Pennsylvania State University): Skewers

[colloque] Tue 14.3.2017, Phys 2.52 at 17h15more

Prof. Philipp Habegger (Uni Basel): Complex Multiplication or is $e^{\pi \sqrt{163}}$ an Integer?

[colloque] Tue 21.3.2017, Phys 2.52 at 17h15more

Prof. Jan Draisma (Uni Bern): tba

[colloque] Tue 25.4.2017, Phys 2.52 at 17h15more

Prof. Antti Knowles (Uni Genève): tba

[colloque] Tue 16.5.2017, Phys 2.52 at 17h15more

Prof. Pierre Nolin (ETHZ): tba

Other talks and events in the current semester

[oberseminar] Oberseminar Geometrie, Wed 4.3.2015, Math II (Lonza) at 10:20more

Martin Herrmann (Fribourg): Almost nonnegative curvature operator, homogeneous spaces and a question of Karsten Grove

[oberseminar] Oberseminar Geometrie, Wed 11.3.2015, Math II (Lonza) at 10:20more

Mike Roberts (Durham): A methodical approach to the construction of Coxeter polytopes in hyperbolic n-space with n+3 facets

[oberseminar] Combinatorics seminar, Fri 13.3.2015, Math II (Lonza) at 13:15more

Ornella greco (KTH Stockholm): The Betti table of Veronese Modules

[oberseminar] Oberseminar Geometrie, Wed 18.3.2015, Math II (Lonza) at 10:20more

Kate Juschenko (Northwestern): Techniques and concepts of amenability of discrete groups

[oberseminar] Oberseminar Geometrie, Wed 26.3.2015, Math II (Lonza) at 10:20more

Stefan Rosemann (Jena): Kähler metrics with Hamiltonian 2-forms, their classification via projectively equivalent metrics and applications

[oberseminar] Oberseminar Geometrie, Wed 15.4.2015, Math II (Lonza) at 10:20more

Bernhard Mühlherr (Giessen): Tits-indices, affine Coxeter groups and buildings

[oberseminar] Oberseminar Geometrie, Wed 22.4.2015, Math II (Lonza) at 10:20more

Viktoriya Ozornova (Bremen / MPIM Bonn): Factorability structures

[oberseminar] Combinatorics seminar, Fri 24.04.2015, Time and place TBAmore

Matteo Varbaro (Genova): On dual graphs of complete intersections

[oberseminar] Oberseminar Geometrie, Wed 29.4.2015, Math II (Lonza) at 10:20more

Jordane Granier (Fribourg): Sous-groupe discret de PU(2,1) avec l'éponge de Menger pour ensemble limite

[oberseminar] Oberseminar Geometrie, Wed 6.5.2015, Math II (Lonza) at 10:20more

Vincent Emery (EPF Lausanne): Volumes des variétés hyperboliques et actions de Galois

[oberseminar] Oberseminar Geometrie, Wed 20.5.2015, Math II (Lonza) at 10:20more

Misha Wasem (ETHZ): Isometric extensions at low regularity and codimension

[oberseminar] Oberseminar Geometrie, Wed 27.5.2015, Math II (Lonza) at 10:20more

Martin Deraux (Grenoble): Groupes de triangles en géométrie hyperbolique complexe

Université de Fribourg - Mathématiques - Ch. du Musée 23, 1700 Fribourg - tél +41 26 / 300 9180      isabella.schmutz@unifr.ch
Last modified on Jun 27, 2016    Webmasters: Sophie Schneider, Michael Dougoud