Marcelo Sales, On Pisier type problems
Zoom ID: 224 221 2686 (ibsecopro)A subset $A\subseteq \mathbb Z$ of integers is free if for every two distinct subsets $B, B'\subseteq A$ we have \Pisier asked if for every subset $A\subseteq \mathbb Z$ of …
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Virtual Discrete Math Colloquium
Paul Seymour, A loglog step towards the Erdős-Hajnal conjecture
Zoom ID: 869 4632 6610 (ibsdimag)In 1977, Erdős and Hajnal made the conjecture that, for every graph $H$, there exists $c>0$ such that every $H$-free graph $G$ has a clique or stable set of size …
Qizhong Lin, Two classical Ramsey-Turán numbers involving triangles
Zoom ID: 224 221 2686 (ibsecopro)In 1993, Erdős, Hajnal, Simonovits, Sós and Szemerédi proposed to determine the value of Ramsey-Turán density $\rho(3,q)$ for $q\ge3$. Erdős et al. (1993) and Kim, Kim and Liu (2019) proposed …
Jie Han, Spanning trees in expanders
Zoom ID: 224 221 2686 (ibsecopro)We consider the spanning tree embedding problem in dense graphs without bipartite holes and sparse graphs. In 2005, Alon, Krivelevich and Sudakov asked for determining the best possible spectral gap …
Shin-ichiro Seki, On the extension of the Green-Tao theorem to number fields
Zoom ID: 897 6822 0619 (ibsecopro) [04/19 only]In 2006, Tao established the Gaussian counterpart of the celebrated Green-Tao theorem on arithmetic progressions of primes. In this talk, I will explain the extension of Tao's theorem and the …
Szymon Toruńczyk, Flip-width: Cops and Robber on dense graphs
Zoom ID: 869 4632 6610 (ibsdimag)We define new graph parameters, called flip-width, that generalize treewidth, degeneracy, and generalized coloring numbers for sparse graphs, and clique-width and twin-width for dense graphs. The flip-width parameters are defined …