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Category Archives: Open problems
Cohen, Haeupler, and Schulman: Explicit Binary Tree-Codes & Cancellations
The high-dimensional conference in Jerusalem is running with many exciting talks (and they are videotaped), and today in Tel Aviv there is a conference on Optimization and Discrete Geometry : Theory and Practice. Today in Jerusalem, Leonard Schulman talked (video available!) … Continue reading
Coloring Problems for Arrangements of Circles (and Pseudocircles)
To supplement and celebrate Aubrey de Grey’s result here are Eight problems on coloring circles A) Consider a finite family of unit circles. What is the minimum number of colors needed to color the circles so that tangent circles are … Continue reading
Posted in Combinatorics, Geometry, Open problems
Tagged Geometric combinatorics, geometric graphs, Graph-coloring
9 Comments
Aubrey de Grey: The chromatic number of the plane is at least 5
A major progress on an old standing beautiful problem. Aubrey de Grey proved that the chromatic number of the plane is at least 5. (I first heard about it from Alon Amit.) The Hadwiger–Nelson problem asks for the minimum number of … Continue reading
Posted in Combinatorics, Geometry, Open problems, Updates
Tagged Aubrey de Grey, The Hadwiger–Nelson problem
11 Comments
Nathan Rubin Improved the Bound for Planar Weak ε-Nets and Other News From Ein-Gedi
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 Epsilon-Nets with … Continue reading
Frankl’s Conjecture for Large Families: Ilan Karpas’ Proof
Frankl’s conjecture asserts that a for every finite family of of finite sets that is closed under union, there is an element that belongs to at least half the sets in the family. We mentioned the problem in our very … Continue reading
Ilan Karpas: Frankl’s Conjecture for Large Families
Frankl’s conjecture Frankl’s conjecture is the following: Let be a finite family of finite subsets of which is closed under union, namely, if then also . Then there exists an element which belongs to at least half the sets in . … Continue reading
Posted in Combinatorics, Open problems
Tagged Abigail Raz, Frankl's conjecture, Ilan Karpas, Peter Frankl
3 Comments
Third third of my ICM 2018 paper – Three Puzzles on Mathematics, Computation and Games. Corrections and comments welcome
Update: Here is a combined version of all three parts: Three puzzles on mathematics computations and games. Thanks for the remarks and corrections. More corrections and comments welcome. Dear all, here is the draft of the third third of my … Continue reading
Posted in Combinatorics, Computer Science and Optimization, Open problems, Physics, Quantum
Tagged ICM2018, Quantum computers
3 Comments
Preview: The solution by Keller and Lifshitz to several open problems in extremal combinatorics
Peter Frankl (right) and Zoltan Furedi The news A new paper by Nathan Keller and Noam Lifshitz settles several open problems in extremal combinatorics for wide range of parameters. Those include the three problems we mention next. Three central open … Continue reading
Posted in Combinatorics, Open problems, Updates
Tagged David Ellis, Ehud Friedgut, Michel Deza, Nathan Keller, Noam Lifshitz, Paul Erdos, Peter Frankl, Zoltán Füredi
1 Comment
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
Eran Nevo: g-conjecture part 4, Generalizations and Special Cases
This is the fourth in a series of posts by Eran Nevo on the g-conjecture. Eran’s first post was devoted to the combinatorics of the g-conjecture and was followed by a further post by me on the origin of the g-conjecture. Eran’s second post was about … Continue reading
Posted in Combinatorics, Convex polytopes, Guest blogger, Open problems
Tagged Eran Nevo, g-conjecture
2 Comments
