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Category Archives: Combinatorics
Sansation in the morning news – Yaroslav Shitov: Counterexamples to Hedetniemi’s conjecture.
Two days ago Nati Linial sent me an email entitled “Sansation in the morning news”. The link was to a new arXived paper by Yaroslav Shitov: Counterexamples to Hedetniemi’s conjecture. Hedetniemi’s 1966 conjecture asserts that if and are two graphs, … Continue reading
Posted in Combinatorics, Open problems, Updates
Tagged Hedetniemi's conjecture, Yaroslav Shitov
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Answer to TYI 37: Arithmetic Progressions in 3D Brownian Motion
Consider a Brownian motion in three dimensional space. We asked (TYI 37) What is the largest number of points on the path described by the motion which form an arithmetic progression? (Namely, , so that all are equal.) Here is … Continue reading
Posted in Combinatorics, Open discussion, Probability
Tagged Brownian motion, Gady Kozma, Itai Benjamini
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The last paper of Catherine Rényi and Alfréd Rényi: Counting k-Trees
A k-tree is a graph obtained as follows: A clique with k vertices is a k-tree. A k-tree with n+1 vertices is obtained from a k-tree with n-vertices by adding a new vertex and connecting it to all vertices of a … Continue reading
Are Natural Mathematical Problems Bad Problems?
One unique aspect of the conference “Visions in Mathematics Towards 2000” (see the previous post) was that there were several discussion sessions where speakers and other participants presented some thoughts about mathematics (or some specific areas), discussed and argued. In … Continue reading
Posted in Combinatorics, Conferences, Open discussion, What is Mathematics
Tagged Misha Gromov
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An Invitation to a Conference: Visions in Mathematics towards 2000
Let me invite you to a conference. The conference took place in 1999 but only recently the 57 videos of the lectures and the discussion sessions are publicly available. (I thank Vitali Milman for telling me about it.) One novel … Continue reading
The (Random) Matrix and more
Three pictures, and a few related links. Van Vu Spoiler: In one of the most intense scenes, the protagonist, with his bare hands and against all odds, took care of the mighty Wigner semi-circle law in two different ways. (From … Continue reading
Posted in Combinatorics, People, What is Mathematics
Tagged Alfréd Rényi, András Hajnal, Catherine Rényi, Paul Erdos, Saharon Shelah, Sándor Szalai, Van Vu
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Gothenburg, Stockholm, Lancaster, Mitzpe Ramon, and Israeli Election Day 2019
Lancaster – Watching the outcomes of the Israeli elections (photo: Andrey Kupavskii) Sweden I just came back from a trip to Sweden and the U.K. I was invited to Gothenburg to be the opponent for a Ph. D. Candidate Malin … Continue reading
Posted in Combinatorics, Probability, Updates
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Is it Legitimate/Ethical for Google to close Google+?
Update April 2, 2019: the links below are not working anymore. Google Plus is a nice social platform with tens of millions participants. I found it especially nice for scientific posts, e.g. by John Baez, Moshe Vardi, or about symplectic … Continue reading
News on Fractional Helly, Colorful Helly, and Radon
My 1983 Ph D thesis was on Helly-type theorems which is an exciting part of discrete geometry and, in the last two decades, I have had an ongoing research project with Roy Meshulam on topological Helly-type theorems. The subject found … Continue reading
