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Colloquia & Seminars


  1. GAAHD Research Seminar: On the classification of C-Fuchsian subgroups of Picard modular groups

    Location: MSRI: Simons Auditorium
    Speakers: Frédéric Paulin (Centre National de la Recherche Scientifique (CNRS))

    Given an imaginary quadratic number field K, we give a classification of the maximal nonelementary subgroups of the Picard modular group PSU_{1,2}(O_K) preserving a complex geodesic in the complex hyperbolic plane. Complementing work of Holzapfel, Chinburg-Stover and Möller-Toledo, we show that these maximal C-Fuchsian subgroups are arithmetic, arising from a quaternion algebra over Q with Hilbert symbol (D,D_K) for some explicit positive integer D and with D_K the discriminant of K. We thus prove the existence of infinitely many orbits of K-arithmetic Cartan chains in Poincaré's hypersphere in the complex projective plane. This is a joint work with Jouni Parkkonen.

    Updated on Apr 17, 2015 09:51 AM PDT
  2. 3-Manifold Seminar

    Location: 939 Evans Hall
    Speakers: Ian Agol (University of California, Berkeley)
    The topic this semester is representations of 3-manifold groups into SL_2 C. Topics will include:
     
    - character varieties and curves of characters
    - ideal points, R-tree actions, tree actions associated to ideal points of curves
    - associating incompressible surfaces to tree actions and measured laminations to R-tree actions
    - volumes of representations and Chern-Simons invariant
    - Dehn invariants, the Bloch group, and extensions
    - volume rigidity, via simplicial volume and the barycenter map
    - the A-polynomial 
     
    Created on Jan 29, 2015 09:28 AM PST
  3. Open ended seminar: Measures on the boundary minimizing energy

    Location: MSRI: Baker Board Room
    Speakers: Seonhee Lim (Seoul National University)

    Let X be the universal cover of a compact manifold of negative curvature. We will present local limit theorem of the heat kernel and explain how we use equidistribution of large spheres. The equidistribution is based on uniform mixing of geodesic flow with respect to a conformal family of measures on the boundary of X, which is the family associated to the Martin kernel. 

     
    This family of measures turns out to be the unique family of measures minimizing the energy (or the Rayleigh quotient of Mohsen). We will also look at the generalized Harish-Chandra function. The normalizing constant which can be defined for any conformal family depends only on the cohomology class of the family of measures.
     
    This is a joint work with François Ledrappier.
    Updated on Apr 17, 2015 09:46 AM PDT
  1. Geometry and Analysis of Surface Group Representations: The Area of Convex Projective 2-Orbifolds

    Location: MSRI: Baker Board Room
    Speakers: Ilesanmi Adeboye (Wesleyan University)

    The Hilbert metric on a bounded convex set $\Omega\subset\mathbb R^2$ determines an area 2-form on $\Omega$. One of the coordinates used by Fock and Goncharov assigns to an ideal triangle $T\subset\Omega$ a shape parameter $t >0$. We obtain a lower bound for the area of $T$ in terms of $t$.

    Updated on Apr 17, 2015 09:54 AM PDT
  2. DMS Research Seminar: The modular action on PSL(2,R)-characters

    Location: MSRI: Simons Auditorium
    Speakers: Maxime Wolff (Institut de Mathematiques de Jussieu)

    I will present joint work with Julien Marché, in which we investigate the action of the mapping class group on the character variety Hom(\pi_1\Sigma_g,PSL(2,R))/PSL(2,R). When g=2 we prove the action is ergodic on every connected component of the space of conjugacy classes of non elementary representations of non extremal Euler class. The first 45 minutes will be introductory.

    Updated on Apr 17, 2015 09:58 AM PDT
  3. DMS Postdoc Seminar: An Overview of the Nahm Transform

    Location: MSRI: Simons Auditorium
    Speakers: Andres Larrain-Hubach (University of Arizona)

    The Nahm Transform is a nonlinear analog of the Fourier Transform, used to construct maps between moduli spaces of solutions of dimensional reductions of Yang-Mills equations. I will discuss several examples and open problems related  to this construction, focusing on the moduli space of solutions to Hitchin equations over a Riemann surface. 

    Updated on Apr 17, 2015 10:38 AM PDT
  4. GAAHD Postdoc Seminar: Hausdorff dimension of product sets

    Location: MSRI: Simons Auditorium
    Speakers: Nicolas de Saxce (Université de Paris XIII (Paris-Nord))

    Given a subset A of a group G, we want to compare the size the product set AAA of elements that can be written as products of three elements of A with the size of A. I will discuss this problem when G is a simple Lie group and the sets A and AAA are measured by their Hausdorff dimension.

    Updated on Apr 17, 2015 10:00 AM PDT
  5. MSRI Evans Talk: Topological rigidity theorems and Homogeneous dynamics

    Location: 60 Evans Hall
    Speakers: Hee Oh (Yale University)

    In the hyperbolic plane H^2, horocycles are given by Euclidean circles tangent to the boundary. In 1936, Hedlund showed that in a compact hyperbolic surface Gamma\H^2, every horocycle is dense; this is one of the first theorems on orbit closures in homogeneous spaces.

    Hedlund’s approach is based on the study of minimal sets and long time behavior of horocyclic flows. This approach was significantly generalized by Margulis  in his proof of Oppenheim conjecture on values of quadratic forms  in 1989.

    In 1991, Ratner gave a complete description of all possible orbit closures on a finite volume homogeneous space under the action of a subgroup generated by unipotent one-parameter subgroups, based on her measure classification theorem.

    We will discuss certain topological rigidity theorems in infinite volume hyperbolic manifolds of dimension 2 or 3 which can be approached by generalizing the ideas of Hedlund and Margulis.  

    Updated on Apr 17, 2015 11:14 AM PDT
  6. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:49 AM PST
  7. 3-Manifold Seminar

    Location: 939 Evans Hall
    Speakers: Ian Agol (University of California, Berkeley)
    The topic this semester is representations of 3-manifold groups into SL_2 C. Topics will include:
     
    - character varieties and curves of characters
    - ideal points, R-tree actions, tree actions associated to ideal points of curves
    - associating incompressible surfaces to tree actions and measured laminations to R-tree actions
    - volumes of representations and Chern-Simons invariant
    - Dehn invariants, the Bloch group, and extensions
    - volume rigidity, via simplicial volume and the barycenter map
    - the A-polynomial 
     
    Created on Jan 29, 2015 09:29 AM PST
  8. Open ended seminar

    Location: MSRI: Baker Board Room
    Updated on Mar 06, 2015 09:51 AM PST
  9. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (Eidgenössische TH Zürich-Hönggerberg), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:15 PM PST
  10. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:50 AM PST
  11. Open ended seminar

    Location: MSRI: Baker Board Room
    Updated on Mar 06, 2015 09:51 AM PST
  12. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (Eidgenössische TH Zürich-Hönggerberg), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:15 PM PST
  13. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:52 AM PST
  14. Open ended seminar

    Location: MSRI: Baker Board Room
    Updated on Mar 06, 2015 09:50 AM PST
  15. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (Eidgenössische TH Zürich-Hönggerberg), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:14 PM PST

Past Seminars

seminar
  1. Seminar 3-Manifold Seminar

    Created on Jan 29, 2015 09:25 AM PST
  2. Seminar Minicourse

    Created on Mar 23, 2015 09:57 AM PDT
  3. Seminar Minicourse

    Created on Feb 23, 2015 10:43 AM PST
  4. Seminar 3-Manifold Seminar

    Created on Jan 29, 2015 09:23 AM PST
There are more then 30 past seminars. Please go to Past seminars to see all past seminars.