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 Polymath10post 4: Back to the drawing board?
 News (mainly polymath related)
 Polymath 10 Post 3: How are we doing?
 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
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 Polymath10post 4: Back to the drawing board?
 Answer: Lord Kelvin, The Age of the Earth, and the Age of the Sun
 Polymath10: The Erdos Rado Delta System Conjecture
 Believing that the Earth is Round When it Matters
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 Amazing: Peter Keevash Constructed General Steiner Systems and Designs
 News (mainly polymath related)
 The KadisonSinger Conjecture has beed Proved by Adam Marcus, Dan Spielman, and Nikhil Srivastava
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Category Archives: Open problems
Polymath 10 Post 3: How are we doing?
The main purpose of this post is to start a new research thread for Polymath 10 dealing with the ErdosRado Sunflower problem. (Here are links to post 2 and post 1.) Here is a very quick review of where we … Continue reading
Posted in Combinatorics, Mathematics over the Internet, Open problems, Polymath10
Tagged polymath10, sunflower conjecture
103 Comments
More Reasons for Small Influence
Readers of the bigleague ToC blogs have already heard about the breakthrough paper An averagecase depth hierarchy theorem for Boolean circuits by Benjamin Rossman, Rocco Servedio, and LiYang Tan. Here are blog reports on Computational complexity, on the Shtetl Optimized, and of Godel … Continue reading
Coloring Simple Polytopes and Triangulations
Coloring Edgecoloring of simple polytopes One of the equivalent formulation of the fourcolor theorem asserts that: Theorem (4CT) : Every cubic bridgeless planar graph is 3edge colorable So we can color the edges by three colors such that every two … Continue reading
Jim Geelen, Bert Gerards, and Geoﬀ Whittle Solved Rota’s Conjecture on Matroids
Gian Carlo Rota Rota’s conjecture I just saw in the Notices of the AMS a paper by Geelen, Gerards, and Whittle where they announce and give a high level description of their recent proof of Rota’s conjecture. The 1970 conjecture asserts … Continue reading
Posted in Combinatorics, Open problems, Updates
Tagged Bert Gerards, Eric Katz, Geoﬀ Whittle, Gian Carlo Rota, Jim Geelen, June Huh, Matroids
7 Comments
My Mathematical Dialogue with Jürgen Eckhoff
Jürgen Eckhoff, Ascona 1999 Jürgen Eckhoff is a German mathematician working in the areas of convexity and combinatorics. Our mathematical paths have met a remarkable number of times. We also met quite a few times in person since our first … Continue reading
Posted in Combinatorics, Convex polytopes, Open problems
Tagged Andy Frohmader, Helly's theorem, Jurgen Eckhoff, Nina Amenta, Noga Alon, Roy Meshulam
1 Comment
NavierStokes Fluid Computers
Smart fluid Terry Tao posted a very intriguing post on the NavierStokes equation, based on a recently uploaded paper Finite time blowup for an averaged threedimensional NavierStokes equation. The paper proved a remarkable negative answer for the regularity conjecture for a certain … Continue reading
Amazing: Peter Keevash Constructed General Steiner Systems and Designs
Here is one of the central and oldest problems in combinatorics: Problem: Can you find a collection S of qsubsets from an nelement set X set so that every rsubset of X is included in precisely λ sets in the collection? … Continue reading
Many triangulated threespheres!
The news Eran Nevo and Stedman Wilson have constructed triangulations with n vertices of the 3dimensional sphere! This settled an old problem which stood open for several decades. Here is a link to their paper How many nvertex triangulations does the 3 … Continue reading
Posted in Combinatorics, Convex polytopes, Geometry, Open problems
Tagged Eran Nevo, Stedman Wilson
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Polymath 8 – a Success!
Yitang Zhang Update (July 22, ’14). The polymath8b paper “Variants of the Selberg sieve, and bounded intervals containing many primes“, is now on the arXiv. See also this post on Terry Tao’s blog. Since the last update, we also had here … Continue reading
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