Category Archives: Combinatorics

Proof By Lice!

From camels to lice. (A proof promised here.) Theorem (Hopf and Pannwitz, 1934): Let be a set of points in the plane  in general position (no three points on a line) and consider line segments whose endpoints are in .  Then … Continue reading

Posted in Combinatorics, What is Mathematics | Tagged | 5 Comments

The seventeen camels riddle, and Noga Alon’s camel proof and algorithms

Three children inherited 17 camels. The will gave one half to one child, one third to a second child and one ninth to the third. The children did not know what to do and  a neighbor offered to lend them … Continue reading

Posted in Combinatorics | Tagged | 4 Comments

Edmund Landau and the Early Days of the Hebrew University of Jerusalem

Some personal/historical remarks in  first minutes of my lecture at 7ECM on July 2016… German-Jewish mathematicians in the early days of the Hebrew University of Jerusalem Being invited to give a plenary lecture at the 7ECM was a great honor … Continue reading

Posted in Academics, Combinatorics, personal | Tagged | 4 Comments

Boolean Functions: Influence, Threshold, and Noise

Here is the written version of my address at the 7ECM last July in Berlin. Boolean functions, Influence, threshold, and Noise Trying to follow an example of a 1925 lecture by Landau (mentioned in the lecture), the writing style is very … Continue reading

Posted in Combinatorics, Computer Science and Optimization, Probability | Tagged | 6 Comments

Laci Babai Visits Israel!

  I am sure that every one of the readers of this blog heard about Laci Babai’s quasi-polynomial algorithm for graph isomorphism and also the recent drama about it: A mistake pointed out by Harald Helfgott,  a new sub-exponential but … Continue reading

Posted in Combinatorics, Computer Science and Optimization, Updates | Tagged , | 2 Comments

Polymath10 conclusion

The Polymath10 project on the Erdos-Rado Delta-System conjecture took place over this blog from November 2015 to May 2016. I aimed for an easy-going project that people could participate calmly aside from their main research efforts and  the duration of … Continue reading

Posted in Combinatorics, Open problems, Polymath10 | Tagged , | 4 Comments

Is Heads-Up Poker in P?

Five years ago I wrote a post entitled Is Backgammon in P? It was based on conversations with Peter Bro Miltersen and Uri Zwick (shown together in the above picture) about the computational complexity of computing the values (and equilibrium … Continue reading

Posted in Combinatorics, Computer Science and Optimization, Games | Tagged , , , , | 3 Comments

Polynomial Method Workshop

The workshop on the  “polynomial method” will take place at the Hebrew University of Jerusalem on Monday Dec 26 and Tuesday Dec 27. The event is organized by Jordan Ellenberg and Gil Kalai. Program: Monday 10-11:45  (Combinatorics seminar) Adam Shefer – … Continue reading

Posted in Combinatorics, Conferences, Updates | Tagged | 3 Comments

Amazing: Stefan Glock, Daniela Kühn, Allan Lo, and Deryk Osthus give a new proof for Keevash’s Theorem. And more news on designs.

Blogging was slow recently, and I have various half written posts on all sort of interesting things, and plenty of unfulfilled promises. I want to quickly share with you two and a half news items regarding combinatorial designs. As you … Continue reading

Posted in Combinatorics, Updates | Tagged , , , , , , , , | 2 Comments

The US Elections and Nate Silver: Informtion Aggregation, Noise Sensitivity, HEX, and Quantum Elections.

Being again near general  elections is  an opportunity to look at some topics we talked about over the years. I am quite fond of (and a bit addicted to) Nate Silver’s site FiveThirtyEight. Silver’s models tell us what is the probability that … Continue reading

Posted in Combinatorics, Computer Science and Optimization, Probability, Quantum | Tagged , , | 14 Comments