Amitsur Algebra

  • 2016 Dec 29

    Amitsur Algebra: Igor Rivin, "Random integer matrices"

    12:00pm to 1:00pm

    Location: 

    Manchester Building, Room 209
    Title: Random integer matrices
    Abstract: I will discuss various models of random integer matrices, and their (occasionally surprising) properties. Some of the work discussed is joint with E. Fuchs.
  • 2016 Dec 22

    Amitsur Algebra: Mark Sapir (Vanderbilt)

    12:00pm to 1:00pm

    Location: 

    Manchester Building, Room 209
    Title: On groups with quadratic Dehn functions
    Abstract: This is a joint work with A. Olshanskii. We construct a finitely presented group with quadratic Dehn function and undecidable conjugacy problem.
  • 2016 Dec 08

    Amitsur Algebra: George Glauberman (Chicago)

    12:00pm to 1:15pm

    Location: 

    Manchester Building, Room 209
    Title: Fixed points of finite groups on modules
    Abstract: Suppose G is a finite group, p is a prime, S is a Sylow p-subgroup of G, and V is a G-module over a field of characteristic p. In some situations, an easy calculation shows that the fixed points of G on V are the same as the fixed points of the normalizer
    of S in G. Generalizations of this result have been obtained previously to study the structure of G for p odd. We plan to describe a new generalization for p = 2. (This is part of joint work with J. Lynd that removes the classification of finite simple groups
  • 2016 Jun 16

    Amitsur Algebra: Gili Golan, "The generation problem in Thompson group F"

    12:00pm to 1:15pm

    Location: 

    Manchester Building (room 209), Jerusalem, Israel
    We show that the generation problem in Thompson group F is decidable, i.e., there is an algorithm which decides if a finite set of elements of F generates the whole F. The algorithm makes use of the Stallings 2-core of subgroups of F, which can be defined in an analogue way to the Stallings core of subgroups of a free group. An application of the algorithm shows that F is a cyclic extension of a group K which has a maximal elementary amenable subgroup B. The group B is a copy of a subgroup of F constructed by Brin.
  • 2016 Jun 09

    Joint Amitsur Algebra&NT Seminar: Shai Haran (Technion), "New foundations for geometry"

    12:00pm to 1:15pm

    Location: 

    Manchester Building (Ross 63), Jerusalem, Israel
    *** Please note the LOCATION ***
    We shall give a simple generalization of commutative rings. The
    category GR of such generalized rings contains ordinary commutative
    rings (fully, faithfully), but also the "integers" and the "residue
    field" at a real or complex place of a number field ; the "field with
    one element" F1 (the initial object of GR) ; the "Arithmetical
    Surface" (the categorical sum of the integers Z with them self). We
    shall show this geometry sees the real and complex places of a number
  • 2016 Apr 21

    Amitsur Algebra: Konstantin Golubev (HU)

    12:00pm to 1:15pm

    Location: 

    Manchester Building (room 209), Jerusalem, Israel
    Title: Spectral approach to the chromatic number of a simplicial complex
    Abstract: In this talk, we'll summarize results obtained in recent years in a pursuit for spectral bounds for the chromatic number of a simplicial complex. As the principal application, we'll show that Ramanujan complexes serve as family of explicitly constructed complexes with large girth and large chromatic number. We'll also present other results, such as a bound on the expansion and a bound on the mixing of a complex, and refer to open questions.
  • 2016 Apr 07

    Amitsur Algebra: Ayala Byron (HUJI), "Definable fields in the free group"

    12:00pm to 1:15pm

    Location: 

    Manchester Building (room 209), Jerusalem, Israel
    Abstract: In the early 2000s Sela proved that all non-abelian free groups share a common first-order theory. Together with R. Sklinos, we use tools developed in his work to show that no infinite field is definable in this theory. In this talk we will survey the line of proof for a formal solution theorem for a simple sort of definable sets, that have a structure of a hyperbolic tower, and use it to characterize definable sets that do not carry a definable structure of an abelian group.

Pages