Talks and events


Upcoming talks

[oberseminar] Oberseminar Topologie, Mon 18.12.2017, Math II (Lonza) at 16h00

Manuel Amann (Augburg): Orbifolds with all geodesics closed

The concept of a Riemannian orbifold generalises the one of a Riemannian manifold by permitting certain singularities. In particular, one is able to speak about several concepts known from classical Riemannian geometry including geodesics. Whenever all geodesics can be extended for infinite time and are all periodic, the orbifold is called a Besse orbifold—in analogy to Besse manifolds. A classical result in the simply-connected manifold case states that in odd dimensions only spheres may arise as examples of Besse manifolds. In this talk we shall illustrate that the same holds for Besse orbifolds, namely that they are actually already manifolds whence they are spheres. The talk is based on joint work in progress with Christian Lange and Marco Radeschi.

[oberseminar] Wed 20.12.2017, Math II (Lonza) at 10h20

Roman Prosanov (Fribourg): Covering problems in discrete geometry

Let X and Y be subsets of some geometric space. What is the least possible k such that we can cover X using k copies of Y? (If X can not be covered with a finite numbers of copies of Y then we can introduce and investigate the {\it density} of covering.) This is the most basic scheme for covering problems in discrete geometry. These problems are important for different applications. The richest theory was developed in the case when the ``geometric'' space is R^n or Euclidean torus and copies are translates of Y.
The main milestone was the theorem of Rogers which can be reformulated as follows.
{\bf Theorem.} Let T^n be an n-dimensional Euclidean torus and K \subset T^n be a convex body. Define the relative volume \rho(K) = \frac{{\rm vol}(K)}{{\rm vol}(T^n)}. Then it is possible to cover T^n using no more than \rho(K)^{-1}(n \ln n + n \ln \ln n + 5n) translates of K.
This result had a big impact on discrete geometry and was reproved several times. We will discuss the recent approach proposed in 2015 by M. Nasz\'odi. It uses fractional coverings in hypergraphs. We will also speak about its possible perspectives to other problems.

[colloque] Tue 20.2.2018, Phys 2.52 at 17h15

Prof. Alexandre Stauffer (University of Bath): tba

[colloque] Tue 6.3.2018, Phys 2.52 at 17h15

Prof. Jan Maas (IST Austria): tba

[colloque] Tue 20.3.2018, Phys 2.52 at 17h15

Prof. Jean-Marc Schlenker (Luxembourg): tba


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): Stabilisation in algebra and geometry

[colloque] Tue 28.03.2017, Phys 2.52 at 17h15more

Martin Kerin (Univ. of Münster): Curvature and exotic spheres

[colloque] Tue 4.4.2017, Phys 2.52 at 17h15more

Prof. Armin Iske (Uni Hamburg): Kernel-based Scattered Data Approximation

[colloque] Tue 25.4.2017, Phys 2.52 at 17h15more

Prof. Antti Knowles (Uni Genève): Extreme eigenvalues of sparse random graphs

[colloque] Tue 16.5.2017, Phys 2.52 at 17h15more

Prof. Pierre Nolin (ETHZ): Near-critical percolation and self-organized criticality in two dimensions

[colloque] Tue 30.5.2017, Phys 2.52 at 17h15more

Prof. Gerhard Wanner (Uni Genève): Porous media modelling with a 250 years old method

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

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