Author Archives: Gil Kalai

The Simplex, the Cyclic polytope, the Positroidron, the Amplituhedron, and Beyond

A quick schematic road-map to these new geometric objects. The  positroidron can be seen as a cellular structure on the nonnegative Grassmanian – the part of the real Grassmanian G(m,n) which corresponds to m by n matrices with all m by … Continue reading

Posted in Algebra and Number Theory, Combinatorics, Convex polytopes, Physics | Tagged , , , , , , | 1 Comment

From Oberwolfach: The Topological Tverberg Conjecture is False

The topological Tverberg conjecture (discussed in this post), a holy grail of topological combinatorics, was refuted! The three-page paper “Counterexamples to the topological Tverberg conjecture” by Florian Frick gives a brilliant proof that the conjecture is false. The proof is … Continue reading

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

Midrasha Mathematicae #18: In And Around Combinatorics

  Tahl Nowik                  Update 3 (January 30): The midrasha ended today. Update 2 (January 28): additional videos are linked; Update 1 (January 23): Today we end the first week of the school. David Streurer and Peter Keevash completed … Continue reading

Posted in Combinatorics, Conferences, Updates | 1 Comment

Quantum computing: achievable reality or unrealistic dream

  Michel Dyakonov’s View on QC                                     My view (based on Michel’s drawing*) Update: Alexander Vlasov’s view (based on Michel and Konstantin’s drawing) … Continue reading

Posted in Quantum | Tagged , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , | 7 Comments

A Historical Picture Taken by Nimrod Megiddo

Last week I took a bus from Tel Aviv to Jerusalem and I saw (from behind) a person that I immediately recognized. It was Nimrod Megiddo, from IBM Almaden, one of the very first  to relate game theory with complexity … Continue reading

Posted in Conferences, Economics, Games | Tagged , | Leave a comment

Scott Triumphs* at the Shtetl

Scott Aaronson wrote a new post on the Shtetl Optimized** reflecting on the previous thread  (that I referred to in my post on Amy’s triumph), and on reactions to this thread. The highlight is a list of nine of Scott’s … Continue reading

Posted in Updates, Women in science | Tagged , | 6 Comments

Amy Triumphs* at the Shtetl

It was not until the 144th comment by a participants named Amy on Scott’s Aaronson recent Shtetl-optimized** post devoted to a certain case of sexual harassment at M. I. T. that the discussion turned into something quite special. Amy’s great … Continue reading

Posted in Controversies and debates, Women in science | Tagged , , | 23 Comments

@HUJI

Ilya Rips and me during Ilyafest last week (picture Itai Benjamini) Ilya Rips Birthday Conference Last week we had here a celebration for Ilya Rips’ birthday. Ilya is an extraordinary mathematician with immense influence on algebra and topology. There were … Continue reading

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When Do a Few Colors Suffice?

When can we properly color the vertices of a graph with a few colors? This is a notoriously difficult problem. Things get a little better if we consider simultaneously a graph together with all its induced subgraphs. Recall that an … Continue reading

Posted in Combinatorics | Tagged | 1 Comment

From Peter Cameron’s Blog: The symmetric group 3: Automorphisms

Originally posted on Peter Cameron's Blog:
No account of the symmetric group can be complete without mentioning the remarkable fact that the symmetric group of degree n (finite or infinite) has an outer automorphism if and only if n=6.…

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