Events & Seminars

  • 2018 Nov 22

    Colloquium: Spencer Unger (HUJI) - A constructive solution to Tarski's circle squaring problem

    2:30pm to 3:30pm

    Location: 

    Manchester Building (Hall 2), Hebrew University Jerusalem
    In 1925, Tarski asked whether a disk in R^2 can be partitioned into finitely many pieces which can be rearranged by isometries to form a square of the same area. The restriction of having a disk and a square with the same area is necessary. In 1990, Laczkovich gave a positive answer to the problem using the axiom of choice. We give a completely explicit (Borel) way to break the circle and the square into congruent pieces. This answers a question of Wagon. Our proof has three main components. The first is work of Laczkovich in Diophantine approximation.
  • 2018 Nov 22

    Basic Notions seminar : Zlil Sela - Basic conjectures and preliminary results in non-commutative algebraic geometry

    4:00pm to 5:15pm

    Location: 

    Ross 70
    Speaker: Zlil Sela
    Title: Basic conjectures and preliminary results in non-commutative algebraic geometry

     Abstract: Algebraic geometry studies the structure of varieties over
     fields and commutative rings. Starting in the 1960's ring theorists
     (Cohn, Bergman and others) have tried to study the structure of varieties
     over some non-commutative rings (notably free associative algebras).

     The lack of unique factorization that they tackled and studied in detail,
  • 2018 Nov 25

    Kazhdan seminar: Tomer Schlank "The Nonabelian Chabauty Method"

    12:00pm to 2:00pm

    Location: 

    Ross 70A
    Abstract: The Chabauty method is a remarkable tool which employs p-adic analitic methods (in particular Colman integration.) To study rational points on curves. However the method can be applied only when the genus of the curve in question is larger than its Mordell-Weil rank. Kim developed a sophisticated "nonableian" generalisation. We shall present the classical methid, and give an approachable introduction to Kim's method. I'm basically going to follow http://math.mit.edu/nt/old/stage_s18.html
  • 2018 Nov 25

    Kazhdan seminar: Karim Adiprasito "Positivity in combinatorics and beyond"

    3:00pm to 5:00pm

    Location: 

    Ross 70A
    Abstract: I will discuss applications of algebraic results to combinatorics, focusing in particular on Lefschetz theorem, Decomposition theorem and Hodge Riemann relations. Secondly, I will discuss proving these results combinatorially, using a technique by McMullen and extended by de Cataldo and Migliorini. Finally, I will discuss Lefschetz type theorems beyond positivity. Recommended prerequisites: basic commutative algebra
  • 2018 Nov 27

    Amir Dembo (Stanford), Large deviations of subgraph counts for sparse random graphs

    2:15pm to 3:15pm

    Location: 

    Ross 70
    For fixed t>1 and L>3 we establish sharp asymptotic formula for the log-probability that the number of cycles of length L in the Erdos - Renyi random graph G(N,p) exceeds its expectation by a factor t, assuming only that p >> log N/sqrt(N). In a narrower range of p=p(N) we obtain such sharp upper tail for general subgraph counts and for the Schatten norms of the corresponding adjacency matrices. In this talk, based on a joint work with Nick Cook, I will explain our approach, based on convex-covering and a new quantitative refinement of
  • 2018 Dec 02

    Kazhdan seminar: Tomer Schlank "The Nonabelian Chabauty Method"

    12:00pm to 2:00pm

    Location: 

    Ross 70A
    Abstract: The Chabauty method is a remarkable tool which employs p-adic analitic methods (in particular Colman integration.) To study rational points on curves. However the method can be applied only when the genus of the curve in question is larger than its Mordell-Weil rank. Kim developed a sophisticated "nonableian" generalisation. We shall present the classical methid, and give an approachable introduction to Kim's method. I'm basically going to follow http://math.mit.edu/nt/old/stage_s18.html

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