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Colloquia & Seminars


Current Seminars

  1. GFA Main Seminar: Sidon Sets and Random Matrices

    Location: MSRI: Simons Auditorium
    Speakers: Gilles Pisier (Texas A & M University)

    We will recall some of the classical theory of Sidon sets of characters on compact groups (Abelian or not), and its connections with Gaussian random variables. We will then give several recent extensions of the notions of Sidon set, randomly Sidon set and subgaussian sequence in bounded orthonormal systems, triggered by Bourgain and Lewko’s recent work. In the second part of the talk, non-commutative analogues will be discussed, involving Sidon subsets in the dual of compact non-Abelian groups. The case of matricial systems, analogous to Fourier-Peter-Weyl series on compact groups, connects the subject to Random Matrix Theory. Several open problems will be discussed. All relevant papers are currently available on arxiv.

    Updated on Nov 13, 2017 03:15 PM PST
  2. GFA Young Researchers Seminar: Gaussian concentration and random unconditional structure

    Location: MSRI: Simons Auditorium
    Speakers: Petros Valettas (University of Missouri)

    The concentration of measure is a basic tool with various applications in geometric functional analysis. Unlike in the isomorphic theory, in the almost isometric context more delicate forms of it are required. In this talk we will discuss how one can take advantage of the linear structure of the normed space in order to establish almost optimal small deviation estimates for the corresponding norm. We will also present an application of the latter on estimates in Dvoretzky’s theorem. (Based on joint work with G. Paouris).

    Updated on Nov 16, 2017 01:44 PM PST

Upcoming Seminars

  1. GTC Graduate Seminar

    Location: MSRI: Baker Board Room
    Speakers: Mónica Blanco Gómez (University of Cantabria), Marcel Celaya (Georgia Institute of Technology)
    Marcel Celaya, Assorted Topics on Matroids
    Monica Blanco Gomez, Preparation for Spanning Lattice Polytopes and the Uniform Position Principle (Lukas Katthan)
    Created on Aug 18, 2017 11:45 AM PDT
  2. GTC Main Seminar: Spanning lattice polytopes and the Uniform position principle

    Location: MSRI: Simons Auditorium
    Speakers: Lukas Katthän (University of Minnesota)

    A lattice polytope is called spanning (or primitive) if its lattice points affinely span the ambient lattice. This property can be translated to a natural algebraic property of the Ehrhart ring of the polytope.
    In this talk, I will present recent joint work with Johannes Hofscheier and Benjamin Nill, where we use methods from commutative algebra and algebraic geometry to obtain new inequalities for the h^*-vector.
    This extends our previous work on the absence of inner zeros in the h^*-vector, as well as Hibi's inequality for polytopes with inner lattice points.

    Updated on Oct 30, 2017 11:24 AM PDT
  3. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:53 AM PDT
  4. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:53 AM PDT
  5. GFA Young Researchers Seminar: Iterative Methods for Solving Factorized Linear Systems

    Location: MSRI: Baker Board Room
    Speakers: Anna Ma (Claremont Graduate University)
    Stochastic iterative algorithms such as the Kacmarz and Gauss-Seidel methods have gained recent attention because of their speed, simplicity, and the ability to approximately solve large-scale linear systems of equations without needing to access the entire matrix. In this work, we consider the setting where we wish to solve a linear system in a large matrix $X$ that is stored in a factorized form, $X = UV$; this setting either arises naturally in many applications or may be imposed when working with large low-rank datasets for reasons of space required for storage. We propose a variant of the randomized Kaczmarz method for such systems that takes advantage of the factored form, and avoids computing $X$. We prove an exponential convergence rate and supplement our theoretical guarantees with experimental evidence demonstrating that the factored variant yields significant acceleration in convergence. Joint work with Deanna Needell and Aaditya Ramdas.
    Updated on Nov 22, 2017 08:41 AM PST
  6. GTC Visions Seminar: Continuous Matroids revisited

    Location: Space Science Lab, Room 105
    Speakers: Anders Björner (Royal Institute of Technology (KTH))

    There are several analogies between discrete and continuous mathematics that influence our thinking and understanding. For a very basic example, take the the Boolean lattice of subsets of a finite set with its continuous analog the measurable subsets of the unit interval.
    A general setting for such analogs, suggested by matroid theory and inspired by von Neumann’s work on "continuous geometries" from 1936, will be discussed. It is based on work from the 1980’s, much of it joint with L. Lovász, on continuous matroids, including continuous analogs of partitions and of field extensions.

    Updated on Nov 22, 2017 02:03 PM PST
  7. GFA Main Seminar

    Location: Space Science Lab, Room 105
    Updated on Nov 22, 2017 08:44 AM PST
  8. GFA Main Seminar

    Location: Space Science Lab, Room 105
    Updated on Nov 22, 2017 08:44 AM PST
  9. UC Berkeley Colloquium: Algebraic Structures on Polytopes

    Location: 60 Evans Hall
    Speakers: Federico Ardila (San Francisco State University)

    http://events.berkeley.edu/index.php/calendar/sn/math.html?event_ID=113270

    Generalized permutahedra are a beautiful family of polytopes with a rich combinatorial structure and strong connections to optimization. We study their algebraic structure: we prove they are the universal family of polyhedra with a certain “Hopf monoid" structure. This construction provides a unifying framework to organize and study many combinatorial families:
    1. It uniformly answers open questions and recovers known results about graphs, posets, matroids, hypergraphs, and simplicial complexes.
    2. It reveals that three combinatorial reciprocity theorems of Stanley and Billera–Jia–Reiner on graphs, posets, and matroids are really the same theorem.
    3. It shows that permutahedra and associahedra “know" how to compute the multiplicative and compositional inverses of power series.
    The talk will be accessible to undergraduates and will not assume previous knowledge of these topics.

    Updated on Nov 20, 2017 12:10 PM PST
  10. GTC Graduate Seminar

    Location: MSRI: Baker Board Room
    Created on Aug 18, 2017 11:45 AM PDT
  11. GTC Main Seminar: On the treewidth of triangulated three-manifolds

    Location: MSRI: Simons Auditorium
    Speakers: Jonathan Spreer (Freie Universität Berlin)

    In graph theory, as well as three-manifold topology, a wide range of parameters exist to decide how "simple", or "thin", a given graph or three-manifold is. These width-type parameters, such as pathwidth or treewidth for graphs, or the concept of thin position for three-manifolds, play an important role when studying algorithmic problems in the field: There exist several topological problems -- some of them known to be computationally hard in general -- which become solvable in polynomial time as soon as the dual graph of the input triangulation has bounded treewidth. 
    In view of such algorithmic results, the question of whether there exists an explicit link between combinatorial concepts such as treewidth (applicable to a single input triangulation of a given three-manifold M) and results in three-manifold topology (applicable to all possible triangulations of M) has repeatedly been asked by researchers working in the computational branch of three-manifold topology.
    In this talk I will present such a link, stating that there exist families of three-manifolds not admitting triangulations of bounded treewidth.

    Updated on Nov 01, 2017 09:18 AM PDT
  12. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:53 AM PDT
  13. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:53 AM PDT
  14. GTC Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:50 AM PDT
  15. GFA Young Researchers Seminar

    Location: MSRI: Simons Auditorium
    Updated on Sep 01, 2017 01:05 PM PDT
  16. GTC Visions Seminar

    Location: MSRI: Simons Auditorium
    Updated on Sep 28, 2017 08:50 AM PDT
  17. GFA Main Seminar: Pisier's cotype dichotomy problem revisited

    Location: MSRI: Simons Auditorium
    Speakers: Gideon Schechtman (Weizmann Institute of Science)

    In an effort to renew interest in the dichotomy problem, I'll survey what is known and in particular tell you about an old/new result of Nicole Tomczak-Jaegermann and myself along the lines of a result of Bourgain but with some improvement. This gives the best known estimate concerning the dichotomy problem . I'll also try to suggest what should be done next.

    Updated on Nov 20, 2017 09:11 AM PST
  18. GFA Main Seminar: Pisier's cotype dichotomy problem revisited

    Location: MSRI: Simons Auditorium
    Speakers: Gideon Schechtman (Weizmann Institute of Science)

    In an effort to renew interest in the dichotomy problem, I'll survey what is known and in particular tell you about an old/new result of Nicole Tomczak-Jaegermann and myself along the lines of a result of Bourgain but with some improvement. This gives the best known estimate concerning the dichotomy problem . I'll also try to suggest what should be done next.

    Updated on Nov 20, 2017 09:11 AM PST
  19. Lattice Points Working Group

    Location: MSRI: Baker Board Room
    Updated on Oct 26, 2017 03:50 PM PDT
  20. GFA Postdoc Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 21, 2017 09:21 AM PDT
  21. GTC Postdoc Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 21, 2017 09:22 AM PDT
  22. GTC Graduate Seminar

    Location: MSRI: Baker Board Room
    Created on Aug 18, 2017 11:45 AM PDT
  23. GTC Main Seminar

    Location: MSRI: Simons Auditorium
    Updated on Nov 01, 2017 09:18 AM PDT
  24. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:53 AM PDT
  25. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:53 AM PDT
  26. GTC Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:50 AM PDT
  27. GFA Young Researchers Seminar

    Location: MSRI: Simons Auditorium
    Updated on Sep 01, 2017 01:06 PM PDT
  28. GTC Visions Seminar

    Location: MSRI: Simons Auditorium
    Updated on Sep 28, 2017 08:50 AM PDT
  29. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:59 AM PDT
  30. GFA Main Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 18, 2017 11:58 AM PDT
  31. Lattice Points Working Group

    Location: MSRI: Baker Board Room
    Updated on Oct 26, 2017 03:51 PM PDT
  32. GFA Postdoc Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 21, 2017 09:21 AM PDT
  33. GTC Postdoc Seminar

    Location: MSRI: Simons Auditorium
    Created on Aug 21, 2017 09:22 AM PDT
  34. Seminar Sequence

    Location: MSRI: Simons Auditorium
    Created on Aug 31, 2017 03:27 PM PDT

Past Seminars

  1. Seminar GTC Graduate Seminar

    Created on Aug 18, 2017 11:45 AM PDT
  2. Seminar Writing Seminar

    Created on Oct 04, 2017 03:29 PM PDT
There are more then 30 past seminars. Please go to Past seminars to see all past seminars.