# Mathematical Sciences Research Institute

Home > Scientific > Colloquia & Seminars

1. # DMS Research Seminar: Stable commutator length on mapping class groups

Location: MSRI: Simons Auditorium
Speakers: Koji Fujiwara (Kyoto University)

In the first part I explain the classical construction of quasi-morphisms by Brooks, a connection between quasi-morphisms and stable commutator length of a group element, scl.

In the second part I discuss algebraic conditions for an element to have scl=0, and on the other hand, explain why negative curvature tends to imply scl>0. Combining them I give a precise condition for a mapping class to have scl >0 in terms Nielsen-Thurston classification. This is a joint work with Bestvina and Bromberg.

Updated on Mar 20, 2015 11:42 AM PDT
2. # Minicourse

Location: MSRI: Simons Auditorium
Speakers: Bernhard Leeb (Ludwig-Maximilians-Universität München)

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 Mar 23, 2015 09:57 AM PDT
1. # DMS Postdoc Seminar: Andreev's theorem on projective Coxeter polyhedra

Location: MSRI: Simons Auditorium
Speakers: Gye-Seon Lee (Ruprecht-Karls-Universität Heidelberg)

In 1970, E.M. Andreev gave a full description of 3-dimensional compact hyperbolic polyhedra with dihedral angles submultiples of pi. We call them hyperbolic Coxeter polyhedra. More precisely, given a combinatorial polyhedron C with assigned dihedral angles, Andreev’s theorem provides necessary and sufficient conditions for the existence of a hyperbolic Coxeter polyhedron realizing C. Since hyperbolic geometry arises naturally as sub-geometry of real projective geometry, we can ask an analogous question for compact real projective Coxeter polyhedra. In this talk, I’ll give a partial answer to this question. This is a joint work with Suhyoung Choi.

Created on Mar 20, 2015 11:57 AM PDT
2. # GAAHD Postdoc Seminar: Gap distributions for saddle connections on the octagon

Location: MSRI: Simons Auditorium
Speakers: Grace Work (University of Illinois at Urbana-Champaign)

(Joint with Caglar Uyanik.) Following a strategy developed by Athreya and Cheung, we compute the gap distribution of the slopes of saddle connections on the octagon by translating the problem to a question about return times of the horocycle flow to an appropriate Poincaré Section. This same strategy was used by Athreya, Chaika, and Lelièvre to compute the gap distribution on the Golden L. The octagon is the first example of this type of computation where the Veech group has two cusps.

Created on Mar 20, 2015 12:00 PM PDT
3. # GAAHD Research Seminar: Density of lattice orbits on homogeneous varieties

Location: MSRI: Simons Auditorium
Speakers: Anish Ghosh (Tata Institute of Fundamental Research)

I will discuss the effective density of lattice orbits on homogeneous varieties. Joint work with A. Gorodnik and A. Nevo.

Updated on Mar 26, 2015 03:46 PM PDT
4. # 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
5. # Open ended seminar: Quantum ergodicity on large graphs

Location: MSRI: Baker Board Room
Speakers: Nalini Anantharaman (Université de Strasbourg)

Consider a sequence of finite graphs, of fixed valency, whose size goes to infinity. Assuming their girths go to infinity and that they are expanders, Etienne Le Masson and I proved some version of the "quantum ergodicity" phenomenon : for most of the eigenfunctions $psi_j$ of the laplacian, the probability measure $|psi_j(x)|^2$ on the set of vertices is close to the uniform measure.

I first want to sketch the published proof of this result, based on the "pseudo-differential calculus" on the regular tree, defined by Le Masson. This proof is very specific to regular graphs.

I then want to present a new, simpler proof, that looks as if it could, in principle, be adapted to non-regular graphs. However this extension to general graphs does not seem obvious and raises several interesting questions in ergodic theory.

Updated on Mar 26, 2015 03:48 PM PDT
6. # Geometry and Analysis of Surface Group Representations: Introduction to Spectral Networks (II)

Location: MSRI: Baker Board Room
Speakers: Daniele Alessandrini (Ruprecht-Karls-Universität Heidelberg)

I will give an introduction to the theory of Spectral Networks, developed by Gaiotto, Moore and Neitzke during their research about supersymmetry.

These objects have an independent interest for mathematicians, mostly in the theory of surfaces. They can be described as combinatorical objects on the surface, or, equivalently as some orbits associated to a conformal structure on the surface and a collection of holomorphic differentials.

The main focus will be on how to use these objects to give coordinates on the moduli spaces of representations of surface groups. These coordinates generalise Fenchel-Nielsen coordinates and Fock-Goncharov coordinates in an especially intriguing way.

Updated on Mar 26, 2015 04:16 PM PDT
7. # Lorentzian geometric structures seminar: Margulis spacetimes and contracting deformations of hyperbolic surfaces II

Location: MSRI: Baker Board Room
Speakers: Jeffrey Danciger (University of Texas)

This second talk will go into more details of the proof.

We will describe a properness criterion for free groups acting by isometries of Minkowski 3-space in terms of the deformation theory of hyperbolic surfaces. A corollary of the criterion is that every Margulis spacetime fibers in lines over a hyperbolic surface.

We will discuss some details of the proof, including the case in which the linear part has parabolics. This talk is based on joint work with François Guéritaud and Fanny Kassel.

Updated on Mar 26, 2015 03:39 PM PDT
8. # DMS Research Seminar: TBA

Location: MSRI: Simons Auditorium
Speakers: Jeffrey Brock (Brown University), Kenneth Bromberg (University of Utah)
Updated on Mar 26, 2015 04:27 PM PDT
9. # DMS Postdoc Seminar: Coupled Hitchin Equations

Location: MSRI: Simons Auditorium
Speakers: Qiongling Li (Rice University)

In this talk, I will talk about a technical part in the joint paper with Brian Collier about studying asymptotic behavior of Hitchin representations in terms of Higgs bundles. This technical part estimates the asymptotic solution of the coupled Hitchin equations. I will also discuss how the analysis is related to geometry of frames.

Updated on Mar 26, 2015 04:14 PM PDT
10. # GAAHD Postdoc Seminar: The stable type of the mapping class group and some relatively hyperbolic groups and applications to pointwise ergodic averages

Location: MSRI: Simons Auditorium
Speakers: Ilya Gekhtman (Yale University)

The stable ratio set of a nonsingular action is a notion introduced by Bowen and Nevo to prove pointwise ergodic theorems for measure preserving actions of certain nonamenable groups.

I  prove that stable ratio set of the action of a discrete subgroup of isometries of a CAT(-1) space with finite Bowen-Margulis measure on its boundary with the Patterson-Sullivan measure has numbers other than 0, 1 and \infinity, extending techniques of Bowen from the setting of hyperbolic groups.

I also prove the same result for the action of the mapping class group on the sphere of projective measured foliations with the Thurston measure, using some "statistical hyperbolicity" properties for the (non hyperbolic) Teichmueller metric on Teichmueller space.

Updated on Mar 26, 2015 03:44 PM PDT
11. # Lorentzian geometric structures seminar

Location: MSRI: Baker Board Room
Created on Feb 23, 2015 11:02 AM PST
12. # MSRI Evans Talk

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

Location: MSRI: Simons Auditorium
Updated on Feb 20, 2015 09:47 AM PST
14. # 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
15. # Open ended seminar

Location: MSRI: Baker Board Room
Updated on Mar 06, 2015 09:52 AM PST
16. # Geometry and Analysis of Surface Group Representations

Location: MSRI: Baker Board Room
Speakers: Qiongling Li (Rice University), Andrew Sanders (University of Illinois at Chicago)
Created on Jan 22, 2015 04:35 PM PST
17. # 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 02:17 PM PST
18. # DMS Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 01:54 PM PST
19. # GAAHD Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 01:55 PM PST
20. # Lorentzian geometric structures seminar

Location: MSRI: Baker Board Room
Created on Feb 23, 2015 11:04 AM PST
21. # GAAHD Research Seminar

Location: MSRI: Simons Auditorium
Updated on Feb 20, 2015 09:49 AM PST
22. # 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
23. # Open ended seminar

Location: MSRI: Baker Board Room
Updated on Mar 06, 2015 09:52 AM PST
24. # Geometry and Analysis of Surface Group Representations

Location: MSRI: Baker Board Room
Speakers: Qiongling Li (Rice University), Andrew Sanders (University of Illinois at Chicago)
Created on Jan 22, 2015 04:36 PM PST
25. # 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 02:16 PM PST
26. # DMS Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 01:57 PM PST
27. # GAAHD Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 02:02 PM PST
28. # Lorentzian geometric structures seminar

Location: MSRI: Baker Board Room
Created on Feb 23, 2015 11:06 AM PST
29. # MSRI Evans Talk

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

Location: MSRI: Simons Auditorium
Updated on Feb 20, 2015 09:49 AM PST
31. # 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
32. # Open ended seminar

Location: MSRI: Baker Board Room
Updated on Mar 06, 2015 09:51 AM PST
33. # Geometry and Analysis of Surface Group Representations

Location: MSRI: Baker Board Room
Speakers: Qiongling Li (Rice University), Andrew Sanders (University of Illinois at Chicago)
Created on Jan 22, 2015 04:38 PM PST
34. # 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
35. # DMS Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 02:04 PM PST
36. # GAAHD Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 02:05 PM PST
37. # Lorentzian geometric structures seminar

Location: MSRI: Baker Board Room
Created on Feb 23, 2015 11:07 AM PST
38. # GAAHD Research Seminar

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

Location: MSRI: Baker Board Room
Updated on Mar 06, 2015 09:51 AM PST
40. # Geometry and Analysis of Surface Group Representations

Location: MSRI: Baker Board Room
Speakers: Qiongling Li (Rice University), Andrew Sanders (University of Illinois at Chicago)
Created on Jan 22, 2015 04:39 PM PST
41. # 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
42. # DMS Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 02:06 PM PST
43. # GAAHD Postdoc Seminar

Location: MSRI: Simons Auditorium
Speakers: Guillaume Dreyer (University of Notre Dame), Nicolas de Saxce (Université de Paris XIII (Paris-Nord))
Created on Jan 28, 2015 02:07 PM PST
44. # Lorentzian geometric structures seminar

Location: MSRI: Baker Board Room
Created on Feb 23, 2015 11:08 AM PST
45. # GAAHD Research Seminar

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

Location: MSRI: Baker Board Room
Updated on Mar 06, 2015 09:50 AM PST
47. # Geometry and Analysis of Surface Group Representations

Location: MSRI: Baker Board Room
Speakers: Qiongling Li (Rice University), Andrew Sanders (University of Illinois at Chicago)
Created on Jan 22, 2015 04:40 PM PST
48. # 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

seminar
1. # SeminarGeometry and Analysis of Surface Group Representations: Introduction to Spectral Networks

Updated on Mar 20, 2015 11:38 AM PDT
2. # SeminarOpen ended seminar: From dynamics to flat geometry

Updated on Mar 20, 2015 11:48 AM PDT
3. # SeminarGAAHD Research Seminar: Patterson-Sullivan Theory and Orbit Counting for Subgroups of Mapping Class Groups

Updated on Mar 20, 2015 11:47 AM PDT
4. # SeminarLorentzian geometric structures seminar: Margulis spacetimes and contracting deformations of hyperbolic surfaces

Updated on Mar 20, 2015 11:44 AM PDT
5. # SeminarSimplicial volume, barycenter method, and bounded cohomology

Created on Mar 16, 2015 09:03 AM PDT
6. # SeminarMinicourse

Created on Feb 23, 2015 10:43 AM PST
7. # SeminarGeometry and Analysis of Surface Group Representations: Hitchin representations and equivariant minimal surfaces

Updated on Mar 17, 2015 12:08 PM PDT
8. # Seminar3-Manifold Seminar

Created on Jan 29, 2015 09:23 AM PST
9. # SeminarOpen ended seminar: Orbits of diagonal flows

Updated on Mar 12, 2015 11:02 AM PDT
10. # SeminarGAAHD Research Seminar: Critical exponents, regular covers and amenability

Updated on Mar 13, 2015 10:02 AM PDT
11. # SeminarDMS Research Seminar: Affine deformations of one-holed torus

Updated on Mar 11, 2015 11:03 AM PDT
12. # SeminarGAAHD Postdoc Seminar: Sparse equidistribution under a unipotent flow

Created on Mar 05, 2015 04:18 PM PST
13. # SeminarDMS Postdoc Seminar: Degeneration of complex projective structures on surfaces that converges in the character variety

Created on Mar 05, 2015 04:20 PM PST
14. # SeminarMinicourse

Created on Feb 23, 2015 10:40 AM PST
15. # SeminarDMS Research Seminar: Counting, Randomness, and Renormalization

Updated on Feb 27, 2015 12:04 PM PST
16. # SeminarOpen ended seminar: Recurrence in random walks

Updated on Mar 05, 2015 04:24 PM PST
17. # Seminar3-Manifold Seminar

Created on Jan 29, 2015 09:22 AM PST
18. # SeminarGAAHD Research Seminar: Equidistribution of expanding translates of curves on homogeneous spaces

Updated on Mar 05, 2015 04:22 PM PST
19. # SeminarWomen in Science

Updated on Feb 05, 2015 12:10 PM PST
20. # SeminarMinicourse

Updated on Feb 23, 2015 10:37 AM PST
21. # SeminarDMS Research Seminar: Flows on irreducible parabolic geometries

Updated on Feb 27, 2015 12:13 PM PST
22. # SeminarGeometry and Analysis of Surface Group Representations: Cubic Differentials and Limits of Convex $RP^2$ Strucures under Neck Pinches

Updated on Feb 27, 2015 03:35 PM PST
23. # Seminar3-Manifold Seminar

Created on Jan 29, 2015 09:21 AM PST
24. # SeminarOpen ended seminar

Updated on Mar 06, 2015 09:53 AM PST
25. # SeminarGAAHD Research Seminar: Asymptotic properties of the Brownian motion on the universal covers of compact negatively curved manifolds

Updated on Feb 27, 2015 11:53 AM PST
26. # SeminarMSRI Evans Talk: Moduli of Geometric Structures

Updated on Feb 18, 2015 08:58 AM PST
27. # SeminarLorentzian geometric structures seminar: Anosov Structure on Margulis Space Time II

Updated on Feb 27, 2015 11:59 AM PST
28. # SeminarGAAHD Postdoc Seminar: Hausdorff dimension of divergent trajectories under the diagonal geodesic flow on product space of hyperbolic spaces

Updated on Feb 27, 2015 12:18 PM PST
29. # SeminarDMS Postdoc Seminar: MCG actions on character varieties

Updated on Feb 27, 2015 02:05 PM PST
30. # SeminarGAAHD Postdoc Seminar: Generalizations of Furstenberg's x2 x3 theorem

Updated on Feb 20, 2015 09:13 AM PST
There are more then 30 past seminars. Please go to Past seminars to see all past seminars.