Events & Seminars

  • 2019 Mar 19

    Dynamics Seminar: Elon Lindenstrauss (HUJI) - Double variational principle for mean dimension

    2:15pm to 3:15pm

    Mean dimension is a topological invariant of dynamical systems introduced by Gromov that measures the number of parameters per iteration needed to describe a trajectory in the system. We characterize this invariant (at least for dynamical systems with the marker property, such as infinite minimal systems) using a min-max principle, where choices of both a metric on the topological space and an invariant probability measure on the system are varied. The work I will report on is joint work with M. Tsukamoto.
  • 2019 Mar 19

    T&G: Viatcheslav Kharlamov (Strasbourg), Segre indices, Welschinger weights, and an invariant signed count of real lines on real projective hypersurfaces

    1:00pm to 2:30pm

    Location: 

    Room 110, Manchester Building, Jerusalem, Israel
    As it was observed a few years ago, there exists a certain signed count of real lines on real projective hypersurfaces of degree 2n+1 and dimension n that, contrary to the honest "cardinal" count, is independent of the choice of a hypersurface, and by this reason provides, as a consequence, a strong lower bound on the honest count. Originally, in this invariant signed count the input of a line was given by its local contribution to the Euler number of an appropriate auxiliary universal vector bundle.
  • 2019 Mar 18

    Special course: A. Goncharov (Yale, visiting Einstein Institute of Mathematics) "Quantum geometry of moduli spaces of local systems on surfaces and representation theory"

    Repeats every week every Monday until Mon Apr 29 2019 except Mon Apr 22 2019.
    4:00pm to 6:00pm

    Location: 

    Ross 70
    Abstract. This is a joint work with Linhui Shen. A decorated surface is an oriented surface with punctures and a finite collection of special points on the boundary, considered modulo isotopy. Let G be a split adjoint group. We introduce a moduli space Loc(G,S) of G-local systems on a decorated surface S, which reduces to the character variety when S has no boundary, and quantize it.
  • 2019 Mar 18

    NT & AG - Antoine Ducros (Sorbonne Université), "Non-standard analysis and non-archimedean geometry"

    2:30pm to 3:30pm

    Location: 

    Room 70A, Ross Building, Jerusalem, Israel
    There is a general slogan according to which the limit behaviour of a one-parameter family of complex algebraic varieties when the parameter t tends to zero should be (partially) encoded in the associated t-adic analytic space in the sense of Berkovich; this slogan has given rise to deep and fascinating conjecturs by Konsevich and Soibelman, as well as positive results by various authors (Berkovich, Nicaise, Boucksom, Jonsson...).
  • 2019 Mar 18

    NT & AG Lunch: Ehud DeShalit "An overview of class field theory"

    1:00pm to 2:00pm

    Location: 

    Faculty lounge, Math building
    Class field theory classifies abelian extensions of local and global fields in terms of groups constructed from the base. We shall survey the main results of class field theory for number fields and function fields alike. The goal of these introductory lectures is to prepare the ground for the study of explicit class field theory in the function field case, via Drinfeld modules. I will talk for the first 2 or 3 times.
  • 2019 Mar 17

    Ari Shnidman "Geometric expressions for derivatives of L-functions of automorphic forms" (after Yun and Zhang)

    Repeats every week every Sunday until Sun Jun 23 2019 except Sun Apr 21 2019.
    2:00pm to 4:00pm

    Yun and Zhang compute the Taylor series expansion of an automorphic L-function over a function field, in terms of intersection pairings of certain algebraic cycles on the so-called moduli stack of shtukas. This generalizes the Waldspurger and Gross-Zagier formulas, which concern the first two coefficients. The goal of the seminar is to develop the background necessary to state their formula, and then indicate the structure of the proof. If time allows, we may also discuss applications to the Birch and Swinnerton-Dyer conjecture for elliptic curves over function fields.
  • 2019 Mar 17

    Zlil Sela and Alex Lubotzky "Model theory of groups"

    Repeats every week every Sunday until Sat Jun 29 2019 except Sun Apr 21 2019.
    11:00am to 1:00pm

    Zlil Sela and Alex Lubotzky "Model theory of groups" In the first part of the course we will present some of the main results in the theory of free, hyperbolic and related groups, many of which appear as lattices in rank one simple Lie groups We will present some of the main objects that are used in studying the theory of these groups, and at least sketch the proofs of some of the main theorems. In the second part of the course, we will talk about the model theory of lattices in high rank simple Lie groups.
  • 2019 Mar 14

    Colloquium: Alexander Bors (University of Western Australia) - Finite groups with a large automorphism orbit

    2:30pm to 3:30pm

    Location: 

    Manchester Building (Hall 2), Hebrew University Jerusalem
    Abstract: If X is an object such that the notion of an automorphism of X is defined (e.g., an algebraic structure, a graph, a topological space, etc.), then one can define an equivalence relation ∼ on X via x ∼ y if and only if α(x) = y for some automorphism α of X. The equivalence classes of ∼ are called the automorphism orbits of X. Say that X is highly symmetric if and only if all elements of X lie in the same automorphism orbit. Finite highly symmetric objects are studied across various mathematical disciplines, e.g. in combinatorics, graph theory and geometry. When

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