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 Mathematical Gymnastics
 Media Item from “Haaretz” Today: “For the first time ever…”
 Jim Geelen, Bert Gerards, and Geoﬀ Whittle Solved Rota’s Conjecture on Matroids
 Media items on David, Amnon, and Nathan
 Next Week in Jerusalem: Special Day on Quantum PCP, Quantum Codes, Simplicial Complexes and Locally Testable Codes
 Happy Birthday Ervin, János, Péter, and Zoli!
 My Mathematical Dialogue with Jürgen Eckhoff
 Test Your Intuition (23): How Many Women?
 Happy Birthday Richard Stanley!
Top Posts & Pages
 The KadisonSinger Conjecture has beed Proved by Adam Marcus, Dan Spielman, and Nikhil Srivastava
 Believing that the Earth is Round When it Matters
 Polymath 8  a Success!
 Why is mathematics possible?
 Emmanuel Abbe: Erdal Arıkan's Polar Codes
 Why Quantum Computers Cannot Work: The Movie!
 When It Rains It Pours
 Extremal Combinatorics III: Some Basic Theorems
 Extremal Combinatorics I: Extremal Problems on Set Systems
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Category Archives: Convex polytopes
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
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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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Richard Stanley: How the Proof of the Upper Bound Theorem (for spheres) was Found
The upper bound theorem asserts that among all ddimensional polytopes with n vertices, the cyclic polytope maximizes the number of facets (and kfaces for every k). It was proved by McMullen for polytopes in 1970, and by Stanley for general triangulations … Continue reading
Lionel Pournin found a combinatorial proof for SleatorTarjanThurston diameter result
I just saw in Claire Mathieu’s blog “A CS professor blog” that a simple proof of the SleatorTarjanThurston’s diameter result for the graph of the associahedron was found by Lionel Pournin! Here are slides of his lecture “The diameters of associahedra” … Continue reading
Posted in Combinatorics, Computer Science and Optimization, Convex polytopes
Tagged Associahedron, Lionel Pournin
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Karim Adiprasito: Flag simplicial complexes and the nonrevisiting path conjecture
This post is authored by Karim Adiprasito The past months have seen some exciting progress on diameter bounds for polytopes and polytopal complexes, both in the negative and in the positive direction. Jesus de Loera and Steve Klee described simplicial polytopes which are not … Continue reading
Posted in Convex polytopes, Guest blogger
Tagged Convex polytopes, Flag complexes, Hirsch conjecture, Karim Adiprasito
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Tokyo, Kyoto, and Nagoya
Near Nagoya: Firework festival; Kyoto: with Gunter Ziegler; with Takayuki Hibi, Hibi, Marge Bayer, Curtis Green and Richard Stanly; Tokyo: Peter Frankl; crowded crossing. Added later: Mazi and I at the same restaurant taken by Stanley. I just returned from … Continue reading
Posted in Combinatorics, Conferences, Convex polytopes
Tagged Alternating sign matrices, Convex polytopes, FPSAC, Japan
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Satoshi Murai and Eran Nevo proved the Generalized Lower Bound Conjecture.
Satoshi Murai and Eran Nevo have just proved the 1971 generalized lower bound conjecture of McMullen and Walkup, in their paper On the generalized lower bound conjecture for polytopes and spheres . Let me tell you a little about it. … Continue reading
Updates, Boolean Functions Conference, and a Surprising Application to Polytope Theory
The Debate continues The debate between Aram Harrow and me on Godel Lost letter and P=NP (GLL) regarding quantum fault tolerance continues. The first post entitled Perpetual motions of the 21th century featured mainly my work, with a short response by Aram. … Continue reading
Projections to the TSP Polytope
Michael Ben Or told me about the following great paper Linear vs. Semidefinite Extended Formulations: Exponential Separation and Strong Lower Bounds by Samuel Fiorini, Serge Massar, Sebastian Pokutta, Hans Raj Tiwary and Ronald de Wolf. The paper solves an old conjecture … Continue reading