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Colloquia & Seminars


Current Seminars

  1. GTC Graduate Seminar: Partitionable Extenders: A Combinatorial Interpretation of the h-vector

    Location: MSRI: Baker Board Room
    Speakers: Joseph Doolittle (University of Kansas)

    The h-vector of a pure simplicial complex is of critical importance to combinatorialists and algebraists. When the complex is partitionable, a combinatorial interpretation for the h-vector is well known. In joint work with Bennet Goeckner and Alexander Lazar, we introduce a new construction which allows for an interpretation of the h-vector as an error term between a partitionable complex and a partitionable relative complex. This construction is inductive and is not minimal. We will briefly discuss minimality and some other issues that arise.

    Updated on Dec 06, 2017 01:17 PM PST
  2. 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 tree width.
    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 Dec 08, 2017 08:44 AM PST
  3. GFA Main Seminar: Ideals in L(L_p)

    Location: MSRI: Simons Auditorium
    Speakers: William Johnson (Texas A & M University)
    I'll discuss the Banach algebra structure of the spaces of bounded linear operators on ell_p and L_p:=L_p(0,1).  
    The main new results are

    1. The only non trivial closed ideal in L(L_p), for 1 <= p < infty, that
    has a left approximate identity is the ideal of compact operators (joint
    with N. C. Phillips and G. Schechtman).

    2. There are infinitely many; in fact, a continuum; of closed ideals in
    L(L_1) (joint with G. Pisier and G. Schechtman).

    The second result answers a question from the 1978 book of A. Pietsch,
    ``Operator ideals".
    Updated on Dec 05, 2017 11:06 AM PST
  4. GFA Main Seminar: Ideals in L(L_p)

    Location: MSRI: Simons Auditorium
    Speakers: William Johnson (Texas A & M University)
    I'll discuss the Banach algebra structure of the spaces of bounded linear operators on ell_p and L_p:=L_p(0,1).  
    The main new results are

    1. The only non trivial closed ideal in L(L_p), for 1 <= p < infty, that
    has a left approximate identity is the ideal of compact operators (joint
    with N. C. Phillips and G. Schechtman).

    2. There are infinitely many; in fact, a continuum; of closed ideals in
    L(L_1) (joint with G. Pisier and G. Schechtman).

    The second result answers a question from the 1978 book of A. Pietsch,
    ``Operator ideals".
    Updated on Dec 05, 2017 11:06 AM PST

Upcoming Seminars

  1. GTC Main Seminar: GTC Farewell Seminar

    Location: MSRI: Simons Auditorium

    Several short talks by members of the GTC program on their work during the semester.

    Updated on Dec 08, 2017 08:45 AM PST
  2. GFA Young Researchers Seminar: A solution to the problem of bodies with congruent sections or projections

    Location: MSRI: Simons Auditorium
    Speakers: Ning Zhang (MSRI - Mathematical Sciences Research Institute)

    In this talk, we will construct two convex bodies K and L, such that their projections K|H, L|H onto every subspace H are congruent, but nevertheless, K and L do not coincide up to a translation or a reflection in the origin. This gives a negative answer to an old conjecture posed by Nakajima and Suss.

    Created on Dec 05, 2017 11:48 AM PST
  3. GFA Main Seminar: Are convex functions special?

    Location: MSRI: Simons Auditorium
    Speakers: Yanir Rubinstein (University of Maryland)

    Legendre duality is inherently a "real" object. Is there a complex analogue of Legendre? In our quest to find such an object, Berndtsson, Cordero-Erausquin, Klartag, and I revisit the « canonical'' role of convex functions, finding many similar classes of functions, all subsets of the space of plurisubharmonic functions. This turns out to have ties to several foundational works in interpolation theory going back to Calderon, Coifman, Cwikel, Rochberg, Sagher, and Weiss, as well as in complex analysis/geometry going back to Alexander--Wermer, Slodkowski, Moriyon, Lempert, Mabuchi, Semmes, and Donaldson.

    Created on Dec 05, 2017 11:49 AM PST
  4. GTC Visions Seminar: GTC Farewell Visions

    Location: MSRI: Simons Auditorium

    Several short talks by members of the GTC program on their work during the semester.

    Updated on Dec 08, 2017 08:45 AM PST
  5. GFA Main Seminar: Some new approaches to the heavy hitters problem

    Location: MSRI: Simons Auditorium
    Speakers: Jelani Nelson (Harvard University)
    In the 'frequent items' problem one sees a sequence of items in a stream (e.g. a stream of words coming into a search query engine like Google) and wants to report a small list of items containing all frequent items. In the 'change detection' problem one sees two streams, say one from yesterday and one from today, and wants to report a small list of items containing all those whose frequencies changed significantly. For both of these problems, we would like algorithms that use memory substantially sublinear in the length of the stream.
    We describe new state-of-the-art solutions to both problems. For the former, we make use of ideas familiar to this community such as chaining methods to control the suprema of Rademacher processes to develop an algorithm BPTree with provably near-optimal memory consumption. For the latter, ideas familiar to this community also pop up (e.g. isoperimetry and Cheeger's inequality) in the course of developing the first algorithm to simultaneously achieve asymptotically optimal space, fast query and update time, and high success probability (over the random coins flipped by the algorithm).
    Based on joint works with Vladimir Braverman, Stephen Chestnut, Nikita Ivkin, Kasper Green Larsen, Huy Le Nguyen, Mikkel Thorup, Zhengyu Wang, and David P. Woodruff
    Updated on Dec 08, 2017 09:24 AM PST
  6. GFA Main Seminar: Projection theorem in Banach spaces

    Location: MSRI: Simons Auditorium
    Speakers: Marianna Csornyei (University of Chicago)

    We study tangential properties of planar curves and demonstrate the failure of the Besicovitch-Federer projection theorem in Banach spaces. Based on joint works with David Bate and Bobby Wilson.

    Updated on Dec 08, 2017 09:24 AM PST
  7. 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 GTC Graduate Seminar

    Created on Aug 18, 2017 11:45 AM PDT
There are more then 30 past seminars. Please go to Past seminars to see all past seminars.