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 Ringel Conjecture, Solved! Congratulations to Richard Montgomery, Alexey Pokrovskiy, and Benny Sudakov
 Test your intuition 43: Distribution According to Areas in Top Departments.
 Two talks at HUJI: on the “infamous lower tail” and TOMORROW on recent advances in combinatorics
 Amazing: Zhengfeng Ji, Anand Natarajan, Thomas Vidick, John Wright, and Henry Yuen proved that MIP* = RE and thus disproved Connes 1976 Embedding Conjecture, and provided a negative answer to Tsirelson’s problem.
 Do Not Miss: Abel in Jerusalem, Sunday, January 12, 2020
 The BrownErdősSós 1973 Conjecture
 Tomorrow: Boolean functions day at the TAU theory fest
 The Google Quantum Supremacy Demo and the Jerusalem HQCA debate.
 Four Great Numberphile Graph Theory Videos
Top Posts & Pages
 Ringel Conjecture, Solved! Congratulations to Richard Montgomery, Alexey Pokrovskiy, and Benny Sudakov
 Test your intuition 43: Distribution According to Areas in Top Departments.
 Amazing: Zhengfeng Ji, Anand Natarajan, Thomas Vidick, John Wright, and Henry Yuen proved that MIP* = RE and thus disproved Connes 1976 Embedding Conjecture, and provided a negative answer to Tsirelson's problem.
 TYI 30: Expected number of Dice throws
 Amazing: Peter Keevash Constructed General Steiner Systems and Designs
 R(5,5) ≤ 48
 A sensation in the morning news  Yaroslav Shitov: Counterexamples to Hedetniemi's conjecture.
 Answer: Lord Kelvin, The Age of the Earth, and the Age of the Sun
 Elchanan Mossel's Amazing Dice Paradox (your answers to TYI 30)
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Category Archives: Convexity
Isabella Novik and Hailun Zheng: Neighborly centrally symmetric spheres exist in all dimensions!
A tweetlong summary: The cyclic polytope is wonderful and whenever we construct an analogous object we are happy. Examples: Neighborly cubic polytopes; The amplituhedron; and as of last week, the NovikZheng new construction of neighborly centrally symmetric spheres! At last: … Continue reading
News on Fractional Helly, Colorful Helly, and Radon
My 1983 Ph D thesis was on Hellytype 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 Hellytype theorems. The subject found … Continue reading
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
Jean
Jean Bourgain and Joram Lindenstrauss. I was very sad to hear that Jean Bourgain, among the greatest mathematicians of our time, and a dear friend, passed away. I first met Jean about forty years ago and later we became friends … Continue reading
Posted in Analysis, Combinatorics, Computer Science and Optimization, Convexity, Number theory, Obituary
Tagged Jean Bourgain
4 Comments
Ricky and Branko
Two dear friends, and great geometers, Ricky Pollack and Branko Grünbaum passed away a few weeks ago. Ricky was a close friend that both Mazi my wife and I loved, and we were both fascinated by his wisdom, charm and … Continue reading
Posted in Combinatorics, Convexity, Geometry, Obituary
Tagged Branko Grunbaum, Ricky Pollack
3 Comments
Nathan Rubin Improved the Bound for Planar Weak εNets and Other News From EinGedi
I just came back from a splendid visit to Singapore and Vietnam and I will write about it later. While I was away, Nathan Rubin organized a lovely conference on topics closed to my heart ERC Workshop: Geometric Transversals and EpsilonNets with … Continue reading
Basic Notions Seminar is Back! Helly Type Theorems and the Cascade Conjecture
Kazhdan’s Basic Notion Seminar is back! The “basic notion seminar” is an initiative of David Kazhdan who joined the Hebrew University math department around 2000. People give series of lectures about basic mathematics (or not so basic at times). Usually, speakers do … Continue reading
Posted in Combinatorics, Convexity, Open problems
Tagged David Kazhdan, Helly type theorems, Tverberg's theorem
4 Comments
From Oberwolfach: The Topological Tverberg Conjecture is False
The topological Tverberg conjecture (discussed in this post), a holy grail of topological combinatorics, was refuted! The threepage paper “Counterexamples to the topological Tverberg conjecture” by Florian Frick gives a brilliant proof that the conjecture is false. The proof is … Continue reading
Posted in Combinatorics, Conferences, Convexity, Updates
Tagged Florian Frick, Issac Mabillard, Oberwolfach, Uli Wagner
3 Comments
Around Borsuk’s Conjecture 3: How to Save Borsuk’s conjecture
Borsuk asked in 1933 if every bounded set K of diameter 1 in can be covered by d+1 sets of smaller diameter. A positive answer was referred to as the “Borsuk Conjecture,” and it was disproved by Jeff Kahn and me in 1993. … Continue reading