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 Polymath10, Post 2: Homological Approach
 Polymath10: The Erdos Rado Delta System Conjecture
 Convex Polytopes: Seperation, Expansion, Chordality, and Approximations of Smooth Bodies
 Igor Pak’s collection of combinatorics videos
 EDP Reflections and Celebrations
 Séminaire N. Bourbaki – Designs Exist (after Peter Keevash) – the paper
 Important formulas in Combinatorics
 Updates and plans III.
 NogaFest, NogaFormulas, and Amazing Cash Prizes
Top Posts & Pages
 The KadisonSinger Conjecture has beed Proved by Adam Marcus, Dan Spielman, and Nikhil Srivastava
 Polymath10, Post 2: Homological Approach
 Polymath10: The Erdos Rado Delta System Conjecture
 Four Derandomization Problems
 Believing that the Earth is Round When it Matters
 Updates and plans III.
 NogaFest, NogaFormulas, and Amazing Cash Prizes
 Why is Mathematics Possible: Tim Gowers's Take on the Matter
 'Gina Says'
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Monthly Archives: March 2009
An Open Discussion and Polls: Around Roth’s Theorem
Suppose that is a subset of of maximum cardinality not containing an arithmetic progression of length 3. Let . How does behave? We do not really know. Will it help talking about it? Can we somehow look beyond the horizon and try to guess what … Continue reading
Posted in Combinatorics, Open discussion, Open problems
Tagged Cap sets, polymath1, Roth's theorem, Szemeredi's theorem
25 Comments
A Proposal Regarding Gilad Shalit
Since an agreement for the release of Gilad Shalit in exchange for the release of Hamas prisoners could not be reached, I propose to initiate negotiations (perhaps with Egyptian help) on the improvement of Gilad Shalit’s captivity conditions. In return … Continue reading
A Deeper Look at Basketball
This basketball is combinatorially equivalent to? Answer
Colorful Caratheodory Revisited
Janos Pach wrote me: “I saw that you several times returned to the colored Caratheodory and Helly theorems and related stuff, so I thought that you may be interested in the enclosed paper by Holmsen, Tverberg and me, in … Continue reading
A Beautiful Garden of Hypertrees
We had a series of posts (1,2,3,4) “from Helly to Cayley” on weighted enumeration of Qacyclic simplicial complexes. The simplest case beyond Cayley’s theorem were Qacyclic complexes with vertices, edges, and triangles. One example is the sixvertex triangulation of the … Continue reading
Posted in Combinatorics
Tagged Mishael Rosenthal, Nati Linial, Roy Meshulam, Topological combinatorics, Trees
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Extremal Combinatorics on Permutations
We talked about extremal problems for set systems: collections of subsets of an element sets, – Sperner’s theorem, the ErdosKoRado theorem, and quite a few more. (See here, here and here.) What happens when we consider collections of permutations rather … Continue reading
Posted in Combinatorics
Tagged ErdosKoRado theorem, Extremal combinatorics, Permutations
9 Comments
Polymath1: Success!
“polymath” based on internet image search And here is a link to the current draft of the paper. Update: March 26, the name of the post originally entitled “Polymath1: Probable Success!” was now updated to “Polymath1: Success!” It is now becoming … Continue reading
Posted in Blogging, Combinatorics, What is Mathematics
Tagged Density HalesJewett theorem, polymath1
10 Comments
Do Politicians Act Rationally?
Well, I wrote an article (in Hebrew) about it in the Newspaper Haaretz. An English translation appeared in the English edition. Here is an appetizer: During World War II, many fighter planes returned from bombing missions in Japan full of bullet holes. The … Continue reading
Noise Sensitivity Lecture and Tales
A lecture about Noise sensitivity Several of my recent research projects are related to noise, and noise was also a topic of a recent somewhat philosophical post. My oldest and perhaps most respectable noiserelated project was the work with Itai Benjamini and Oded … Continue reading
The Mystery Beeping Riddle
We came back from the airport with our daughter who has just landed after a fourmonth trip to India. The car was making a strange beep every so often. Maybe it is an indicator signal that should have … Continue reading
Posted in Mathematics to the rescue, Rationality, Riddles
12 Comments