Talks and events

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Upcoming talks

[colloque] Tue 22.5.2018, Phys 2.52 at 17h15

Prof. Stéphane Loisel (ISFA Lyon): Reevaluation of the capital charge in insurance after a large shock: empirical and theoretical views

Motivated by the recent introduction of regulatory stress tests in the Solvency II framework, we study the impact of the re-estimation of the tail risk and of loss absorbing capacities on poststress solvency ratios. Our contribution is threefold. First, we build the first stylized model for re-estimated solvency ratio in insurance. Second, this leads us to solve a new theoretical problem in statistics: what is the asymptotic impact of a record on the re-estimation of tail quantiles and tail probabilities for classical extreme value estimators? Third, we quantify the impact of the re-estimation of tail quantiles and of loss absorbing capacities on real-world solvency ratios thanks to regulator data from EIOPA. Our analysis sheds a first light on the role of the loss absorbing capacity and its paramount importance in the Solvency II capital charge computations. We conclude with a number of policy recommendations for insurance regulators.

[oberseminar] Geometric Analysis Seminar, Fri 25.05.2018, place TBA, at 14:15

Roger Züst (University of Bern): TBA

[colloque] Tue 29.5.2018, Phys 2.52 at 17h15

Prof. Aleksandr Kolpakov (Uni Neuchâtel): Super-exponential families of hyperbolic manifolds

A classical theorem of Wang says that for every positive real number $v$ the number $N(v)$ of distinct (up to an isometry) hyperbolic $n$-manifolds with volume bounded by $v$, provided $n\geq 4$, is finite. The recent results by Burger-Gelander-Lubotzky-Mozes, Belolipetsky-Gelander-Lubotzky-Shalev, Gelander-Levit show that there are super-exponentially many non-isometric hyperbolic manifolds with respect to volume as a "complexity measure", i.e. $a_1 v^{b_1 v} \leq N(v) \leq a_2 v^{b_2}v$ (if $v$ is large enough), and an analogous statement holds for the number of arithmetic hyperbolic $n$-manifolds, and even the number of their commensurability classes. We shall continue in this direction and investigate some particular families of $4$-dimensional hyperbolic manifolds with more specific properties (still not entirely accessible in arbitrary dimensions), such as having a given number of cusps, a given symmetry group, and other natural geometric or topological restrictions. We shall show that in all cases the number of such manifolds grows super-exponentially with respect to volume. This talk is based on the joint papers and work in progress with Bruno Martelli (University of Pisa), Leone Slavich (University of Pisa), Steven Tschantz (Vanderbilt University), Alan Reid (Rice University) and Stefano Riolo (University of Neuchâtel).

[oberseminar] Oberseminar Geometrie, Tue 29.05.2018, Math II (Lonza) at 13h15

Matthieu Jacquemet (HES-SO Valais (Sion) and University of Fribourg): Computational aspects of the classification of hyperbolic Coxeter polyhedra

Hyperbolic Coxeter polyhedra are quite easy to describe, and yet they are of central interest in various quite deep contexts, such as small volume hyperbolic orbifolds, growth rate of groups, and sphere packings.
A hard question in this setting is the classification question. This is somehow surprizing: the spherical and Euclidean Coxeter polyhedra exist in all dimensions, and we have a complete (and very short) classification for them. This is no longer the case in the hyperbolic space, where there is a dimensional bound for the existence of such objects, as well as a totally different situation as for the combinatorial types which are realizable.
In this talk, we will focus on combinatorial tools which can be used in order to (try to) exhibit new classes of hyperbolic Coxeter polyhedra, or even just one new example enjoying certain properties. The fact that these polyhedra have a very simple combinatorial description suggests that an algorithmic approach could be promising, but we are going to see what kind of difficulties can arise, and give a couple of ideas on how to address them.

Archive:

Colloquia in the current semester

[colloque] Tue 20.2.2018, Phys 2.52 at 17h15more

Prof. Alexandre Stauffer (University of Bath): Spatial growth processes: dendritic formation and competition

[colloque] Tue 6.3.2018, Phys 2.52 at 17h15more

Prof. Jan Maas (IST Austria): Gradient flows and optimal transport in discrete and quantum systems

[colloque] Tue 13.3.2018, Phys 2.52 at 17h15more

Prof. Florian Bertrand (American University of Beirut): Invariant metrics in complex analysis

[colloque] Tue 20.3.2018, Phys 2.52 at 17h15more

Prof. Jean-Marc Schlenker (Luxembourg): Polyhedra inscribed in quadrics

[colloque] Tue 10.4.2018, Phys 2.52 at 17h15more

Prof. Pierre Pansu (Université Paris-Sud Orsay): Large scale conformal geometry

[colloque] Tue 8.5.2018, Phys 2.52 at 17h15more

Prof. Luis Guijarro (Universidad Autónoma de Madrid): The transverse Jacobi equation for geodesics

[colloque] Tue 15.5.2018, Phys 2.52 at 17h15 more

Prof. Andrea Mondino (Warwick): Smooth and non-smooth aspects of Ricci curvature lower bounds

[colloque] Tue 22.5.2018, Phys 2.52 at 17h15more

Prof. Stéphane Loisel (ISFA Lyon): Reevaluation of the capital charge in insurance after a large shock: empirical and theoretical views

[colloque] Tue 29.5.2018, Phys 2.52 at 17h15more

Prof. Aleksandr Kolpakov (Uni Neuchâtel): Super-exponential families of hyperbolic manifolds

Other talks and events in the current semester

[oberseminar] Oberseminar Geometrie, Tue 13.02.2018, Math II (Lonza) at 10h20more

Arielle Leitner (Technion): Generalized cusps on convex projective manifolds

[oberseminar] Oberseminar Geometrie, Wed 21.02.2018, Math II (Lonza) at 10h20more

Corina Ciobotaru (Fribourg): Applications of hyperbolic geometry to Kuramoto model of synchronization

[oberseminar] Informal Analysis Seminar, Tue 27.02.2018, Seminar room 0.102, at 10:15more

Kevin Wildrick: The theory of Newton-Sobolev mappings

[oberseminar] Oberseminar Geometrie, Wed 28.02.2018, Math II (Lonza) at 10h20more

Cesar Ceballos (University of Vienna): Combinatorics and Geometry of v-Tamari lattices

[oberseminar] Geometric Analysis Seminar, Fri 02.03.2018, Science de la Terre 1.309, at 14:15more

Changyu Guo (Fribourg): Theory of p-harmonic mappings: progress and open problems

[oberseminar] Combinatorics Seminar, Wed 7.3.2018, Math II (Lonza) at 14h00more

Enrico Cecini (Genoa): Matroid structures in Graph Signal Processing

[oberseminar] Oberseminar Geometrie, Wed 07.03.2018, Math II (Lonza) at 10h20more

Thibaut Dumont (Jyväskylä): Growth of the volume cocycle in Euclidean buildings

[oberseminar] Oberseminar Topologie, Mon 12.03.2018, Math II (Lonza) at 16h00 more

Uwe Semmelmann (Stuttgart): The kernel of the Rarita-Schwinger operator on Riemannian spin manifolds

[oberseminar] Oberseminar Topologie, Monday 19.03.2018, Math II (Lonza) at 16h00more

Jan-Bernhard Kordass (Karlsruhe): Spaces of Riemannian Metrics satisfying Surgery Stable Curvature Conditions

[oberseminar] Combinatorics Seminar, Wed 21.3.2018, Math II (Lonza) at 14h00more

Viola Siconolfi (Roma): Wonderful models for generalized Dowling lattices

[oberseminar] Oberseminar Geometrie, Wed 21.03.2018, Math II (Lonza) at 10:20more

Roman Prosanov (Fribourg): From cusped hyperbolic surfaces to convex ideal Fuchsian polyhedra

[oberseminar] Oberseminar Topologie, Monday 26.03.2018, Math II (Lonza) at 16h00more

Raphael Zentner (Regensburg/FIM): Irreducible SL(2,C)-representations of integer homology 3-sphere

[oberseminar] Oberseminar Geometrie, Wed 28.03.2018, Math II (Lonza) at 10:20more

Kurt Falk (Kiel): Dimension gaps for limit sets of Kleinian groups

[oberseminar] Oberseminar Geometrie, Wed 11.04.2018, Math II (Lonza)more

Olivier Mila (Bern): Nonarithmetic hyperbolic manifolds and trace rings

[oberseminar] Oberseminar Geometrie, Wed 18.04.2018, Math II (Lonza)more

Stefano Riolo (Neuchatel): Growth of geometrically bounding hyperbolic 3-manifolds

[oberseminar] Oberseminar Geometrie, Wed 02.05.2018, Math II (Lonza) at 10h20more

Ivan Izmestiev (Fribourg): Flexible Kokotsakis polyhedra

[oberseminar] Oberseminar Topologie, Thursday 03.05.2018, Math II (Lonza) at 15h00more

Wilderich Tuschmann (Karlsruhe, KIT): Nikolaev manifolds and Alexandrov metrics

[oberseminar] Geometric Analysis Seminar, Fri 04.05.2018, Sciences de la Terre, room 1.309, at 14:15more

Thomas Mettler (Goethe-Universitaet Frankfurt): The Beltrami differential revisited

[oberseminar] Oberseminar Topologie, Monday 07.05.2018, Math II (Lonza) at 16h00more

Mauricio Bustamante (Augsburg): Bundles with fiberwise negatively curved metrics

[oberseminar] Geometric Analysis Seminar, Tue 08.05.2018, Physics 2.52, at 10:15more

Hubert Sidler (University of Fribourg): Harmonic quasi-isometric maps into Gromov hyperbolic CAT(0)-spaces

[oberseminar] Oberseminar Geometrie, Wed 09.05.2018, Math II (Lonza) at 10h20more

Christoforos Neofytidis (Geneva): Aspherical circle bundles and a problem of Hopf

[oberseminar] Geometric Analysis Seminar, Tue 15.05.2018, Physics 2.52, at 10:15more

Andrea Mondino (Warwick): Geometric and functional inequalities via a 1-dimensional localisation method

[oberseminar] Oberseminar Geometrie, Wed 16.05.2018, Math II (Lonza) at 10h20more

Edoardo Dotti (Fribourg): Classification of Hyperbolic Coxeter Groups

[oberseminar] Geometric Analysis Seminar, Fri 18.05.2018, Science de la Terre 1.309, at 14:15more

Tomasz Adamowicz (Warsaw): Mean-value harmonic functions

[oberseminar] Geometric Analysis Seminar, Fri 25.05.2018, place TBA, at 14:15more

Roger Züst (University of Bern): TBA

[oberseminar] Oberseminar Geometrie, Tue 29.05.2018, Math II (Lonza) at 13h15more

Matthieu Jacquemet (HES-SO Valais (Sion) and University of Fribourg): Computational aspects of the classification of hyperbolic Coxeter polyhedra

Université de Fribourg - Mathématiques - Ch. du Musée 23, 1700 Fribourg - tél +41 26 / 300 9180      isabella.schmutz@unifr.ch
Last modified on Mar 5, 2018    Webmasters: Sophie Schneider, Simon Drewitz