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All Colloquia & Seminars

  1. 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
  2. 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
  1. Lorentzian geometric structures seminar: Affine crystallographic and properly discontinuous groups

    Location: MSRI: Baker Board Room
    Speakers: Grigory Soifer (Bar-Ilan University)

    In 1964  L. Auslander conjectured that every crystallographic subgroup $\Gamma$ of the affine group $\text{Aff}(\mathbb R^n)$ is virtually solvable, i.e. contains a solvable subgroup of finite index. D.~Fried and W.~Goldman proved Auslander's conjecture for $n=3$ using cohomological arguments.  We (H. Abels G. Margulis, G.Soifer) proved the Auslander conjecture for $n < 7$. The proof is based mainly on dynamical arguments. The talk is divided into three parts: (1) What is proved. (2) The main ideas and methods. (3) Open problems.

    Updated on Apr 24, 2015 11:02 AM PDT
  2. Information Theory Seminar: The game of Amazons

    Location: Simons Institute for Theoretical Computing
    Speakers: Elwyn Berlekamp (University of California, Berkeley)

    Amazons is a board game in which each of the two players controls a few pieces called "Amazons".  Traditional games begin with four Amazons of each color in a defined starting position on a 10 x 10 board; shorter games are sometimes played with each player having three Amazons on an 8 x 8 board.  Each Amazon moves like a chess queen: any desired distance in a straight line in any of 8 directions.  After landing on an empty square, the Amazon must complete her move by shooting a flaming arrow, which also moves in a straight line in any of the 8 directions.  When the arrow lands, it burns that square off of the board.  This is conventionally denoted placing an immobile Go stone on each burned-out square.  Neither Amazons nor arrows can move onto or over burned-out squares.  Eventually so many squares are burned out that some player, at his turn, is unable to move.  The game then ends and that player loses.

    In most games, the burned-out squares eventually partition the board into several disjoint regions.  We show how combinatorial game theory allows us to evaluate each region, and to sum these values to determine optimal strategies for playing specific endgames.

    Created on Apr 24, 2015 10:07 AM PDT
  3. 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
  4. GAAHD Research Seminar: Dynamics of the horocycle flow on the eigenform loci in genus 2

    Location: MSRI: Simons Auditorium
    Speakers: Barak Weiss (Tel Aviv University)

    This is a joint work with Bainbridge and Smillie, in which we import ideas from homogeneous flows, and specifically Ratner's measure classification and the Dani-Margulis linearization method, to the study of dynamics on strata of translation surfaces in a restricted setting. We discuss dynamics of the horocycle flow on the eigenform loci discovered by Calta and McMullen. We reprove and improve the measure classification result of Calta and Wortman, and obtain a corresponding orbit-closure classification. We show that every orbit is equidistributed in its orbit-closure. We also obtain some statements regarding limits of sequences of measures arising in some counting problems.

    I will state and motivate the results and give a sample of the challenges presented by the translation surface setting. I will try to make it understandable to members of both MSRI programs.

    Updated on Apr 24, 2015 10:12 AM PDT
  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 09:29 AM PST
  6. Open ended seminar: Expansion in linear groups and sum-product

    Location: MSRI: Baker Board Room
    Speakers: Alireza Salehi Golsefidy (University of California, San Diego)

    Let S be a finite symmetric subset of GL(n,Z[1/q]) and G be the group generated by S. In this talk I will explain the necessary and sufficient condition under which the Cayley graphs Cay(G mod p^m,S) form a family of expanders as p runs through primes (coprime with q) and m runs through positive integers. I will also explain the related sum-product result which is based on a new method by Lindenstrauss and Varjú.

    Updated on Apr 24, 2015 10:13 AM PDT
  7. Geometry and Analysis of Surface Group Representations: Characters of representations and character varieties

    Location: MSRI: Baker Board Room
    Speakers: Adam Sikora (University at Buffalo (SUNY))
    We will discuss the extent representations of finitely generated groups into reductive groups are determined by their characters and the related question, whether trace functions generate the coordinate rings of character varieties.
    We will explore some anomalies related to SO(2n,C), for which the character variety is not the variety of characters.
    Updated on Apr 24, 2015 10:03 AM PDT
  8. DMS Research Seminar: Convex projective structures on non-hyperbolic three-manifolds

    Location: MSRI: Simons Auditorium
    Speakers: Jeffrey Danciger (University of Texas)

    Y. Benoist proved that if a closed three-manifold M admits a convex real projective structure, then M is topologically the union along tori of finitely many sub-manifolds each of which admits a complete finite volume hyperbolic structure on its interior. We describe some initial results in the direction of a potential converse to Benoist’s theorem. Specifically, we show that a cusped hyperbolic three-manifold may (under assumptions) be deformed to convex projective structures with totally geodesic torus boundary. Such structures may be (convexly) glued together whenever the geometry at the boundary matches up. In particular, we prove that many doubles of cusped hyperbolic three-manifolds admit convex projective structures. Joint work with Sam Ballas and Gye Seon Lee.

    Updated on Apr 24, 2015 10:19 AM PDT
  9. DMS Postdoc Seminar: Bounded cohomology of mapping class groups (and acylindrically hyperbolic groups)

    Location: MSRI: Simons Auditorium
    Speakers: Maria Beatrice Pozzetti (MSRI - Mathematical Sciences Research Institute)

    Bounded cohomology is a variation of usual cohomology that has many interesting geometric applications: for example it allows to define interesting invariants on some character varieties, and select maximal representations. However it is in general very difficult to compute and still poorly understood.

    I will discuss in which sense mapping class groups have enough hyperbolic features to ensure that their third bounded cohomology is infinite dimensional. This is joint work with Roberto Frigerio and Alessandro Sisto.

    Updated on Apr 24, 2015 03:26 PM PDT
  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 09:28 AM PST
  2. Seminar 3-Manifold Seminar

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

    Created on Mar 23, 2015 09:57 AM PDT
There are more then 30 past seminars. Please go to Past seminars to see all past seminars.