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Colloquia & Seminars


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  1. DMS Postdoc Seminar: MCG actions on character varieties

    Location: MSRI: Simons Auditorium
    Speakers: Sara Maloni (Brown University)
    In this talk we consider the SL(2,C)-character variety X=Hom(F_3, SL(2,C))//SL(2,C) of the free group F_3 of rank 3. We will consider F_3 as the fundamental group of two different surfaces: the four-holed sphere S, and of the three-holed punctured plane N. We will consider the action of the mapping class groups MCG(S) and MCG(N) on it. In particular, we describe a domain of discontinuity for these actions on the relative character varieties X_rel(S) and X_rel(N), which  are the set of representations for which the traces of the boundary curves are fixed. Time permitting, we will mention some open questions on which we are working on now.
     
    (Part of this is joint work with F. Palesi and S. P. Tan, and part is work in progress with F. Palesi.)
    Updated on Feb 27, 2015 02:05 PM PST
  2. GAAHD Postdoc Seminar: Hausdorff dimension of divergent trajectories under the diagonal geodesic flow on product space of hyperbolic spaces

    Location: MSRI: Simons Auditorium
    Speakers: Lei Yang (Yale University)
    In this talk, we will study the behavior of trajectories of diagonal geodesic flow on product space of k copies of n-dimensional non-compact hyperbolic spaces with finite volume,  and shall show that the Hausdorff dimension of the collection of divergent trajectories is equal to k(2n-1)-\frac{n-1}{2}. This extends a result of Yitwah Cheung.
    Updated on Feb 27, 2015 12:18 PM PST
  3. Lorentzian geometric structures seminar: Anosov Structure on Margulis Space Time II

    Location: MSRI: Baker Board Room
    Speakers: Sourav Ghosh (Université Paris-Sud (Orsay))

    This is a continuation from last week.


    In this talk I will describe the stable and unstable leaves for the geodesic flow on the space of non-wandering spacelike geodesics of a Margulis Space Time and prove contraction properties of the leaves under the flow. Using this I will also define the notion of an Anosov representation in the context of representations of the free group into the non-semisimple Lie group $\mathsf{SO}^0(2,1)\ltimes\mathbb{R}^3$.

    Updated on Feb 27, 2015 11:59 AM PST
  4. MSRI Evans Talk: Moduli of Geometric Structures

    Location: 60 Evans Hall
    Speakers: William Goldman (University of Maryland)

    Given a topology S, how many ways (if any) are there of putting some kind of classical geometry on S? For example, the sphere has no compatible system of coordinates with Euclidean geometry. (There is no metrically accurate atlas of the world.) On the other hand, the 2-torus admits a rich supply of Euclidean structures, which form an interesting moduli space which itself enjoys hyperbolic non-Euclidean geometry. For other geometric structures, the moduli spaces are much more complicated and are best described by a dynamical system. This talk will survey some of the interesting dynamical systems which arise for simple examples of geometries on surfaces.

     

     

    Updated on Feb 18, 2015 08:58 AM PST
  5. 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 09:21 AM PST
  6. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 04:52 PM PST
  7. Geometry and Analysis of Surface Group Representations: Cubic Differentials and Limits of Convex $RP^2$ Strucures under Neck Pinches

    Location: MSRI: Simons Auditorium
    Speakers: John Loftin

    Labourie and I independently proved that on a closed oriented surface $S$ of genus $g$ at least 2, a convex real projective structure is equivalent to a pair $(\Sigma,U)$, where $\Sigma$ is a conformal structure and $U$ is a holomorphic cubic differential. It is then natural to allow $\Sigma$ to go to the boundary of the moduli space of Riemann surfaces.  The bundle of cubic differentials then extends over the boundary to form the bundle of regular cubic differentials, which is an orbifold vector bundle over the Deligne-Mumford compactification $\bar{\mathcal M}_g$ of moduli space.

    We define regular convex real projective structures corresponding to the regular cubic differentials over nodal Riemann surfaces and define a topology on these structures. Our topology is an extension of Harvey's use of the Chabauty topology to analyze $\bar {\mathcal M}_g$ via limits of Fuchsian groups.  The main theorem is that the total space of the bundle of regular cubic differentials over $\bar {\mathcal M}_g$ is homeomorphic to the space of regular real projective structures.  The proof involves several analytic inputs: a recent result of Benoist-Hulin on the convergence of some invariant tensors on families of convex domains converging in the Gromov-Hausdorff sense, a recent uniqueness theorem of Dumas-Wolf for certain complete conformal metrics, and some old techniques of the author to specify the real projective end of a surface in terms of the residue of a regular cubic differential.

    Updated on Feb 27, 2015 03:35 PM PST
  8. DMS Research Seminar: Flows on irreducible parabolic geometries

    Location: MSRI: Simons Auditorium
    Speakers: Karin Melnick (University of Maryland)

    Irreducible parabolic geometries are a family of geometric structures including conformal semi-Riemannian structures, projective structures, and many more.  Automorphisms of these structures need not be linearizable around a fixed point, in contrast to semi-Riemannian isometries or affine transformations of a connection.  I will present rigidity theorems for structures of this type admitting special nonlinearizable flows by automorphisms.  A consequence will be that in many cases, if the geometry is not flat---that is, not locally equivalent to the homogeneous model---then automorphisms are determined by their 1-jet at a point.

    Updated on Feb 27, 2015 12:13 PM PST
  9. Minicourse

    Location: MSRI: Simons Auditorium
    Speakers: Michael Kapovich (University of California, Davis)

    This is a series of talks on my work with Bernhard Leeb and Joan Porti, aiming to extend the theory of geometrically finite discrete groups from rank 1 symmetric spaces to higher rank. I will start by reviewing various equivalent definitions of convex-cocompact subgroups of rank 1 Lie groups. Then I review basic geometry of higher rank symmetric spaces and their ideal boundaries. After that, I will define several notions of geometric finiteness in higher rank which generalize (some of) the rank one definitions and prove at least some of the implications between them.  My lectures will be continued by the ones by Bernhard Leeb, who will prove further equivalences of different definitions. 

    Updated on Feb 23, 2015 10:37 AM PST
  10. Women in Science

    Location: MSRI: Simons Auditorium
    Speakers: Shulamit Kahn (Boston University)
    Updated on Feb 05, 2015 12:10 PM PST
  11. GAAHD Research Seminar

    Location: MSRI: Baker Board Room
    Speakers: Nimish Shah (Ohio State University)
    Updated on Feb 17, 2015 03:58 PM PST
  12. 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 09:22 AM PST
  13. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 04:53 PM PST
  14. DMS Research Seminar: Counting, Randomness, and Renormalization

    Location: MSRI: Baker Board Room
    Speakers: Jayadev Athreya (University of Illinois at Urbana-Champaign)

    We describe several uses of the SL(2, R) action on moduli spaces of translation surfaces, in particular how to use ergodic theorems and recurrence results for the SL(2, R) action to understand counting and ergodicity properties for linear flows. Most of this will be based on work of Veech, Masur, Eskin-Masur, Forni, and Zorich. The talk will be elementary and assume very little background.

    Updated on Feb 27, 2015 12:04 PM PST
  15. Minicourse

    Location: MSRI: Baker Board Room
    Speakers: Michael Kapovich (University of California, Davis)

    This is a series of talks on my work with Bernhard Leeb and Joan Porti, aiming to extend the theory of geometrically finite discrete groups from rank 1 symmetric spaces to higher rank. I will start by reviewing various equivalent definitions of convex-cocompact subgroups of rank 1 Lie groups. Then I review basic geometry of higher rank symmetric spaces and their ideal boundaries. After that, I will define several notions of geometric finiteness in higher rank which generalize (some of) the rank one definitions and prove at least some of the implications between them.  My lectures will be continued by the ones by Bernhard Leeb, who will prove further equivalences of different definitions. 

    Created on Feb 23, 2015 10:40 AM PST
  16. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 17, 2015 04:02 PM PST
  17. 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 09:23 AM PST
  18. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 04:55 PM PST
  19. Minicourse

    Location: MSRI: Baker Board Room
    Speakers: Michael Kapovich (University of California, Davis)

    This is a series of talks on my work with Bernhard Leeb and Joan Porti, aiming to extend the theory of geometrically finite discrete groups from rank 1 symmetric spaces to higher rank. I will start by reviewing various equivalent definitions of convex-cocompact subgroups of rank 1 Lie groups. Then I review basic geometry of higher rank symmetric spaces and their ideal boundaries. After that, I will define several notions of geometric finiteness in higher rank which generalize (some of) the rank one definitions and prove at least some of the implications between them.  My lectures will be continued by the ones by Bernhard Leeb, who will prove further equivalences of different definitions. 

    Created on Feb 23, 2015 10:43 AM PST
  20. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:46 AM PST
  21. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 04:57 PM PST
  22. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Jan 28, 2015 02:18 PM PST
  23. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:47 AM PST
  24. 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 09:25 AM PST
  25. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 04:59 PM PST
  26. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (ETH Zurich), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:18 PM PST
  27. MSRI Evans Talk

    Location: 60 Evans Hall
    Speakers: Maryam Mirzakhani (Stanford University)
    Updated on Jan 15, 2015 09:40 AM PST
  28. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:47 AM PST
  29. 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 09:26 AM PST
  30. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 05:01 PM PST
  31. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (ETH Zurich), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:17 PM PST
  32. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:49 AM PST
  33. 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
  34. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 05:03 PM PST
  35. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (ETH Zurich), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:16 PM PST
  36. MSRI Evans Talk

    Location: 60 Evans Hall
    Speakers: Hee Oh (Yale University)
    Updated on Jan 15, 2015 09:42 AM PST
  37. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:49 AM PST
  38. 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
  39. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 05:03 PM PST
  40. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (ETH Zurich), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:15 PM PST
  41. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:50 AM PST
  42. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 05:05 PM PST
  43. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (ETH Zurich), Fanny Kassel (Université de Lille I (Sciences et Techniques de Lille Flandres Artois))
    Updated on Jan 28, 2015 02:15 PM PST
  44. GAAHD Research Seminar

    Location: MSRI: Simons Auditorium
    Updated on Feb 20, 2015 09:52 AM PST
  45. Technical Seminar

    Location: MSRI: Baker Board Room
    Created on Feb 24, 2015 05:06 PM PST
  46. DMS Research Seminar

    Location: MSRI: Simons Auditorium
    Speakers: Marc Burger (ETH Zurich), 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 09:19 AM PST
  2. Seminar 3-Manifold Seminar

    Created on Jan 29, 2015 09:18 AM PST
There are more then 30 past seminars. Please go to Past seminars to see all past seminars.