Past Seminars- Colloquium

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  • Hendrik Lenstra Jr.
    Tue Jan 7, 2014
    3:00 pm
    Given a polynomial map between two vector spaces over a field, how many values can it miss? The lecture will present a number of new results on this question. They were inspired by the work of Daqing Wan, and obtained jointly with Michiel Kosters (Leiden).
  • Jean-Pierre Bourguignon
    Thu Nov 7, 2013
    4:00 pm
    In the last century, Geometry underwent several substantial extensions and revisions based on the fundamental revolutions that it lived through in the XIXth century. The purpose of the lecture is to discuss several aspects of these transformations: the new concepts that emerged from these new points of view, the new perspectives that could be...
  • Eitan Tadmor
    Wed Jun 5, 2013
    4:00 pm
    We discuss self-organized dynamics of agent-based models with focus on a prototype model driven by non-symmetric self-alignment introduced in [1]. Unconditional consensus and flocking emerge when the self-alignment is driven by global interactions with a sufficiently slow decay rate.  In more realistic models, however, the interaction of...
  • Ravi Vakil
    Thu Apr 25, 2013
    4:00 pm
    Given some class of "geometric spaces", we can make a ring as follows. (additive structure)  When U is an open subset of such a space X, [X] = [U] + [(X \ U)]; (multiplicative structure)  [X x Y] = [X] [Y]. In the algebraic setting, this ring (the "Grothendieck ring of varieties")...
  • Leonid Parnovsky
    Thu Apr 4, 2013
    4:00 pm
    I will make a survey of recent results on the spectrum of periodic and, to a smaller extent, almost-periodic operators. I will consider two types of results: 1. Bethe-Sommerfeld Conjecture. For a large class of multidimensional periodic operators the numbers of spectral gaps is finite. 2. Asymptotic behaviour of the integrated density of states...
  • Fuquan Fang
    Thu Jan 17, 2013
    4:00 pm
    There is a well known link between (maximal) polar representations and isotropy representations of symmetric spaces provided by Dadok. Moreover, the theory by Tits and Burns-Spatzier provides a link between irreducible symmetric spaces of non-compact type of rank at least three and irreducible topological spherical buildings of rank at least three...
  • Paul Yang
    Thu Dec 6, 2012
    4:00 pm
    There is a good deal of resemblence of CR geometry in dimension three with conformal geometry in dimension four. Exploiting this resemblence is quite fruitful. For instance, the presence of several conformally covariant operators in both geometries allows us to formulate correct conditions for the embedding problem as well as the CR Yamabe problem...