Seminars in August 2014

  • Suil O, Finding a spanning Halin subgraph in 3-connected {K_{1,3},P_5}-free graphs
    Finding a spanning Halin subgraph in 3-connected \{K_{1,3},P_5\}-free graphs
    Suil O
    Georgia State University, USA
    2014/08/28 *Thursday* 4PM-5PM
    Room 1409
    A Halin graph is constructed from a plane embedding of a tree whose non-leaf vertices have degree at least 3 by adding a cycle through its leaves in the natural order determined by the embedding. In this talk, we prove that every 3-connected \{K_{1,3},P_5\}-free graph has a spanning Halin subgraph. This result is best possible in the sense that the statement fails if K_{1,3} is replaced by K_{1,4} or P_5 is replaced by P_6. This is a joint work with Guantao Chen, Jie Han, Songling Shan, and Shoichi Tsuchiya.
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  • (KMRS Seminar) Imre Barany, Random points and lattice points in convex bodies

    FYI (KMRS Seminar)

    Random points and lattice points in convex bodies
    Imre Barany
    Hungarian Academy of Sciences & University College London
    2014/08/25-08/26 Monday & Tuesday
    4:00PM – 5:00PM Room 1409
    Assume K is a convex body in R^d and X is a (large) finite subset of K. How many convex polytopes are there whose vertices belong toX? Is there a typical shape of such polytopes? How well does the maximal such polytope (which is actually the convex hull of X) approximate K? In this lecture I will talk about these questions mainly in two cases. The first is when X is a random sample of n uniform, independent points from K. In this case motivation comes from Sylvester’s famous four-point problem and from the theory of random polytopes. The second case is when X is the set of lattice points contained in K and the questions come from integer programming and geometry of numbers. Surprisingly (or not so surprisingly), the answers in the two cases are rather similar. The methods are, however, very different.
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  • Suho Oh, Fun with wires
    Fun with wires
    Suho Oh
    University of Michigan/Texas State University, USA
    2014/08/01 Friday 4PM-5PM
    Room 3433
    Wiring diagrams are widely used combinatorial objects that are mainly used to describe reduced words of a permutation. In this talk, I will mention a fun property I recently found about those diagrams, and then introduce other results and problems related to this property.
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