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Recent Posts
 Gil’s Collegial Quantum Supremacy Skepticism FAQ
 Amazing! Keith Frankston, Jeff Kahn, Bhargav Narayanan, Jinyoung Park: Thresholds versus fractional expectationthresholds
 Starting today: Kazhdan Sunday seminar: “Computation, quantumness, symplectic geometry, and information”
 The story of Poincaré and his friend the baker
 Gérard Cornuéjols’s baker’s eighteen 5000 dollars conjectures
 Noisy quantum circuits: how do we know that we have robust experimental outcomes at all? (And do we care?)
 Test Your Intuition 40: What Are We Celebrating on Sept, 28, 2019? (And answer to TYI39.)
 Quantum computers: amazing progress (Google & IBM), and extraordinary but probably false supremacy claims (Google).
 Jeff Kahn and Jinyoung Park: Maximal independent sets and a new isoperimetric inequality for the Hamming cube.
Top Posts & Pages
 Gil's Collegial Quantum Supremacy Skepticism FAQ
 Amazing! Keith Frankston, Jeff Kahn, Bhargav Narayanan, Jinyoung Park: Thresholds versus fractional expectationthresholds
 Amazing: Hao Huang Proved the Sensitivity Conjecture!
 Quantum computers: amazing progress (Google & IBM), and extraordinary but probably false supremacy claims (Google).
 TYI 30: Expected number of Dice throws
 Jeff Kahn and Jinyoung Park: Maximal independent sets and a new isoperimetric inequality for the Hamming cube.
 Answer: Lord Kelvin, The Age of the Earth, and the Age of the Sun
 The story of Poincaré and his friend the baker
 Amazing: Ryan Alweiss, Shachar Lovett, Kewen Wu, Jiapeng Zhang made dramatic progress on the Sunflower Conjecture
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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, 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