Recent Comments

Recent Posts
 Amazing: Stefan Glock, Daniela Kühn, Allan Lo, and Deryk Osthus give a new proof for Keevash’s Theorem. And more news on designs.
 The US Elections and Nate Silver: Informtion Aggregation, Noise Sensitivity, HEX, and Quantum Elections.
 Avifest live streaming
 AlexFest: 60 Faces of Groups
 Postoctoral Positions with Karim and Other Announcements!
 Jirka
 AviFest, AviStories and Amazing Cash Prizes.
 Polymath 10 post 6: The ErdosRado sunflower conjecture, and the Turan (4,3) problem: homological approaches.
 Polymath 10 Emergency Post 5: The ErdosSzemeredi Sunflower Conjecture is Now Proven.
Top Posts & Pages
 Amazing: Peter Keevash Constructed General Steiner Systems and Designs
 Amazing: Stefan Glock, Daniela Kühn, Allan Lo, and Deryk Osthus give a new proof for Keevash's Theorem. And more news on designs.
 Answer: Lord Kelvin, The Age of the Earth, and the Age of the Sun
 A Breakthrough by Maryna Viazovska Leading to the Long Awaited Solutions for the Densest Packing Problem in Dimensions 8 and 24
 Why Quantum Computers Cannot Work: The Movie!
 The Erdős Szekeres polygon problem  Solved asymptotically by Andrew Suk.
 Greg Kuperberg: It is in NP to Tell if a Knot is Knotted! (under GRH!)
 Polymath 10 Emergency Post 5: The ErdosSzemeredi Sunflower Conjecture is Now Proven.
 Extremal Combinatorics VI: The FranklWilson Theorem
RSS
Monthly Archives: August 2008
A Diameter Problem (2)
2. The connection with Hirsch’s Conjecture The Hirsch Conjecture asserts that the diameter of the graph G(P) of a dpolytope P with n facets is at most nd. Not even a polynomial upper bound for the diameter in terms of d and … Continue reading
Posted in Combinatorics, Convex polytopes, Open problems
5 Comments
Two Very Early Problems, a Simple Solution, and a New Problem
As an undergraduate student whenever I studied some subject I tried to come up with problems. Many of these problems were artificial or silly and, of course, I forgot most of them. But a few still make sense. Here are … Continue reading
Posted in Open problems
9 Comments
Surprising Math
1. A pleasant surprise When I worked on the diameter problem for dpolytopes with n facets. I was aiming to prove an upper bound of the form but my proof only gave It was a pleasant surprise to note that . 2. … Continue reading
Posted in Uncategorized
4 Comments
Plans and Updates
Jerusalem and Budapest Monday, last week was the last day of lectures for the spring term here at the Hebrew U. One outcome of the long professors’ strike was a very fruitful year for research seminars. We ran them during … Continue reading
More Art: Tami’s Autoportrait
And in my office, there is a beautiful autoportrait by my sister Tamar Kalai. (Click for a deatiled picture.)
Our Department’s Quilt
Academic administation is a topic of great interest that desrves a special post. The highest post I served was as the department chair, and one thing I did was to acquire for the department a quilt by the artist Anna Maria … Continue reading