Author Archives: Gil Kalai

Some Mathematical Puzzles that I encountered during my career

Recently, I gave some lectures based on a general-audience personal tour across four (plus one) mathematical puzzles that I encountered during my career. Here is a paper based on these lectures which is meant for a very wide audience (in … Continue reading

Posted in Combinatorics, Computer Science and Optimization, Quantum | Tagged | 1 Comment

Friendship and Sesame, Maryam and Marina, Israel and Iran

Happy new (Jewish) year everybody. Amazing scientific partnership  between Jordan, Cyprus, Egypt, Iran, Israel, Pakistan, the Palestinian Authority, and Turkey SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) is a “third-generation” synchrotron light source that was officially opened in Allan (Jordan) on 16 May 2017. … Continue reading

Posted in Obituary, Updates, Women in science | Tagged , , , , | 1 Comment

Elchanan Mossel’s Amazing Dice Paradox (your answers to TYI 30)

TYI 30 asked Elchanan Mossel’s Amazing Dice Paradox (that I heard from Yuval Peres yesterday) You throw a die until you get 6. What is the expected number of throws (including the throw giving 6) conditioned on the event that all throws … Continue reading

Posted in Combinatorics, Probability, Test your intuition | Tagged , | 62 Comments

TYI 30: Expected number of Dice throws

Test your intuition: You throw a dice until you get 6. What is the expected number of throws (including the throw giving 6) conditioned on the event that all throws gave even numbers. follow-up post

Posted in Combinatorics, Probability, Test your intuition | Tagged | 36 Comments

Test your intuition 29: Diameter of various random trees

Both trees in general and random trees in particular are wonderful objects. And there is nothing more appropriate to celebrate Russ Lyons great birthday conference “Elegance in Probability” (taking place now in Tel Aviv) than to test your intuition, dear … Continue reading

Posted in Combinatorics, Probability, Test your intuition | Tagged , | 18 Comments

Micha Perles’ Geometric Proof of the Erdos-Sos Conjecture for Caterpillars

A geometric graph is a set of points in the plane (vertices) and a set of line segments between certain pairs of points (edges). A geometric graph is simple if the intersection of  two edges is empty or a vertex … Continue reading

Posted in Combinatorics, Geometry | Tagged , | 1 Comment

Touching Simplices and Polytopes: Perles’ argument

Joseph Zaks (1984), picture taken by Ludwig Danzer (OberWolfach photo collection)   The story I am going to tell here was told in several places, but it might be new to some readers and I will mention my own angle, … Continue reading

Posted in Combinatorics, Convex polytopes, Geometry, Open problems | Tagged , | Leave a comment

Where were we?

I was slow blogging, and catching up won’t be so easy. Of course, this brings me back to the question of what I should blog about. Ideally, I should tell you about mathematical things I heard about. The problem is … Continue reading

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

Call for nominations for the Ostrowski Prize 2017

  Call for nominations for the Ostrowski Prize 2017 The aim of the Ostrowski Foundation is to promote the mathematical sciences. Every second year it provides a prize for recent outstanding achievements in pure mathematics and in the foundations of … Continue reading

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Problems for Imre Bárány’s Birthday!

  On June 18-23 2017 we will celebrate in Budapest the 70th birthday of Imre Bárány. Here is the webpage of the conference. For the occasion I wrote a short paper with problems in discrete geometry, mainly around Helly’s and … Continue reading

Posted in Combinatorics, Conferences, Open problems | Tagged | Leave a comment