Category Archives: Combinatorics

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 | 1 Comment

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

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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 , , , , , , | 1 Comment

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 | Leave a comment

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

Posted in Combinatorics, Economics, Open discussion, Rationality | Tagged | 9 Comments

Danny Nguyen and Igor Pak: Presburger Arithmetic Problem Solved!

Short Presburger arithmetic is hard! This is a belated report on a remarkable breakthrough from 2017. The paper is Short Presburger arithmetic is hard, by Nguyen and Pak. Danny Nguyen Integer programming in bounded dimension: Lenstra’s Theorem Algorithmic tasks are … Continue reading

Posted in Combinatorics, Computer Science and Optimization, Convex polytopes | Tagged , , , , , , , , | 2 Comments

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

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Bob Sedgewick’s Free Online Courses on Analysis of Algorithms and Analytic Combinatorics.

Philippe Flajolet 1948-2011   I am  happy to forward the announcement on two free online courses (Mooks) by Bob Sedgewick  Analysis of Algorithms and Analytic Combinatorics. Analysis of Algorithms  page provides access to online lectures, lecture slides, and assignments for … Continue reading

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Karim Adiprasito: The g-Conjecture for Vertex Decomposible Spheres

J Scott Provan (site) The following post was kindly contributed by Karim Adiprasito. (Here is the link to Karim’s paper.) Update: See Karim’s comment on the needed ideas for extend the proof to the general case. See also  in the … Continue reading

Posted in Combinatorics, Convex polytopes, Geometry, Guest blogger | Tagged , , , , | 9 Comments

Attila Por’s Universality Result for Tverberg Partitions

In this post  I would like to tell you about three papers and three theorems. I am thankful to Moshe White and Imre Barany for helpful discussions. a) Universality of vector sequences and universality of Tverberg partitions, by Attila Por; Theorem … Continue reading

Posted in Combinatorics, Convexity | Tagged , , , , , , , | 6 Comments