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Current Colloquia & Seminars

  1. DDC - Computability Theory: Degree spectra of analytic complete equivalence relations

    Location: MSRI: Online/Virtual
    Speakers: Dino Rossegger (University of Waterloo)

    To participate in this seminar, please register here: https://www.msri.org/seminars/25206

    Abstract: We present new results on the complexity of the classification problem of countable structures and their computational complexity. We show that the elementary bi-embeddability relation on the class of graphs is analytic complete under Borel reducibility by giving a reduction from the bi-embeddability relation on graphs. We then compare the degree spectra with respect to these equivalence relations. The degree spectrum of a countable structure with respect to an equivalence relation E is the set of Turing degrees of structures E-equivalent to it. We show that the degree spectra of structures with respect to bi-embeddability and elementary bi-embeddability are related: Every bi-embeddability spectrum of a graph is the set of jumps of Turing degrees in the elementary bi-embeddability spectrum of a graph.

    Updated on Nov 19, 2020 11:42 AM PST
  2. RAS - Postdoc Seminar: A Deligne Complex for Artin Monoids

    Location: MSRI: Online/Virtual
    Speakers: Rose Morris-Wright (University of California, Los Angeles)

    To attend this seminar, please register here: https://www.msri.org/seminars/25205

     

    A Deligne Complex for Artin Monoids

    (Based on joint work with Rachael Boyd and Ruth Charney)

     

    I will introduce a new geometric construction associated to an Artin monoid. Artin groups are a generalization of braid groups and the Artin monoid is the monoid with the same generators and relations as in the Artin group. In 1995, Charney and Davis introduced the Deligne complex, a CAT(0) cube complex, which they use to prove the K(pi,1) conjecture for FC type Artin groups. In a recent paper, Boyd, Charney and I use Boyd’s construction of a monoid coset for an Artin monoid to create a version of the Deligne complex for an Artin monoid. 

    In this talk, I will first discuss Artin monoids, how they differ from Artin groups, and why Artin monoids are interesting objects to study. Then I will outline the construction of the Deligne complex for an Artin monoid. Finally I will discuss some of the geometric properties of this complex that we have derived, including the fact that the Deligne complex of a monoid is always contractible, with a locally isometric embedding into the Deligne complex of the group. 

    Updated on Nov 24, 2020 04:36 PM PST
  3. Tea for DDC Members and Participants

    Location: MSRI: Online/Virtual

    Tea for members and participants of the Decidability, definability and computability in number theory virtual program.

    To participate, please register here: https://www.msri.org/seminars/25206

    Updated on Nov 24, 2020 08:57 AM PST
  4. DDC - Minicourse: Picard-Fuchs Differential Equations - Discussion Section 5

    Location: MSRI: Online/Virtual
    Speakers: Charles Doran (University of Alberta)

    To participate in this seminar, please register here: https://www.msri.org/seminars/25206

    This mini course is an introduction to the theory, computation, and applications of Picard-Fuchs differential equations.  The main prerequisite is knowledge of basic complex algebraic geometry at the introductory graduate level.  We will develop a thorough understanding, from several different theoretical perspectives, of some of the key examples in the mathematics and physics literature.  This course should be of interest to geometers, model theorists, and physicists alike.

    Updated on Dec 02, 2020 08:19 AM PST
  5. Fellowship of the Ring, National Seminar:

    Location: MSRI: Online/Virtual

    To attend this seminar, you must register in advance, by clicking HERE.

    Updated on Sep 03, 2020 11:07 AM PDT