Monthly Archives: June 2009

Test Your Intuition (6)

Posted on June 29, 2009 by

This is not as clear cut a question as the earlier ones, and if you do not know an answer then it will be difficult to figure one out just based on intuition. (But perhaps possible). If you are intrigued by … Continue reading →

Posted in Test your intuition | Tagged | 12 Comments

Praise For ‘Gina says’

Posted on June 24, 2009 by

Praise for: ” ‘Gina Says,’ Adventures in the Blogsphere String War (Below the dividing line:  Greg Kuperberg, Scott Aaronson, Clifford Johnson, Peter Woit, Motty Perry, Caterina Calsamiglia, Yuval Peres, Eva Illouz, and (right from the comment section)  Luca Trevisan, Thomas … Continue reading →

Posted in Book review, Gina Says | 11 Comments

My Book: “Gina Says,” Adventures in the Blogosphere String War

Posted on June 23, 2009 by

Update (November 2017): I received an advanced copy. How exciting! Update (October 2017): The much changed version of the book with beautiful drawing by my daughter Neta Kalai is soon to appear in print. It is published by World Scientific. Here … Continue reading →

Posted in Blogging, Gina Says | 36 Comments

A Little Story Regarding Borsuk’s Conjecture

Posted on June 22, 2009 by

Jeff Kahn Jeff and I worked on the problem for several years. Once he visited me with his family for two weeks. Before the visit I emailed him and asked: What should we work on in your visit? Jeff asnwered: … Continue reading →

Posted in Convexity, Taxi-and-other-stories | Tagged , | 7 Comments

Borsuk’s Conjecture

Posted on June 21, 2009 by

Karol Borsuk conjectured in 1933 that every bounded set in can be covered by sets of smaller diameter.  Jeff Kahn and I found a counterexample in 1993. It is based on the Frankl-Wilson theorem. Let be the set of vectors of length . … Continue reading →

Posted in Combinatorics | Tagged , | 7 Comments

Istanbul!

Posted on June 19, 2009 by

   

Posted in Uncategorized | 6 Comments

Banknotes with Pictures of Mathematicians

Posted on June 18, 2009 by

Are you aware of any? (current ones? old ones?)

Posted in Uncategorized | 12 Comments

Test Your Intuition (5)

Posted on June 9, 2009 by

  (Not such a set) consider a planar set A with the following property. In every direction, the distance between the two parallel lines that touch A from both sides is the same! Must A be a circle?

Posted in Convexity, Test your intuition | Tagged | 4 Comments

Answer To Test Your Intuition (4)

Posted on June 6, 2009 by

Let G be a graph and u and v two vertices. (1) Let H be a random graph where every edge of G is chosen with probability ½. Let p be the probability that there is a path between u … Continue reading →

Posted in Probability, Test your intuition | Tagged , | 1 Comment

Test Your Intuition (4)

Posted on June 4, 2009 by

Let G be a graph and u and v two vertices. (1) Let H be a random graph where every edge of G is chosen with probability ½. Let p be the probability that there is a path between u … Continue reading →

Posted in Probability | 18 Comments