Monthly Archives: April 2012

A Really Nice Talk About PDE, Numerics (and Pyramids)

My previous post recommended a really nice talk by Jonathan Israel about human rights. Here is the link again. It is very recommended. Actually, I was in the audience and after the lecture, at the reception,  I came to the … Continue reading

Posted in Analysis, Applied mathematics | 1 Comment

The 1789 Declaration of the Rights of Man

Today (April 27, 2012) it is precisely 213 years 7 months, and 29 days to the completion of the declaration of the rights of man, which makes it a perfect occasion to celebrate this remarkable human creation. Here is a … Continue reading

Posted in Law, Philosophy | Tagged | 4 Comments

Galvin’s Proof of Dinitz’s Conjecture

Dinitz’ conjecture The following theorem was conjectured by Jeff Dinitz in 1979 and proved by Fred Galvin in 1994: Theorem: Consider an n by n square table such that in each cell (i,j) you have a set with n or more elements. … Continue reading

Posted in Combinatorics, Games | 4 Comments

Greg Kuperberg: It is in NP to Tell if a Knot is Knotted! (under GRH!)

Wolfgang Haken found an algorithm to tell if a knot is trivial, and, more generally with Hemion, if two knots are equivalent. Joel Hass, Jeff Lagarias and Nick Pippinger proved in 1999 that telling that a knot is unknotted is … Continue reading

Posted in Computer Science and Optimization, Geometry | Tagged | 8 Comments

Exciting News on Three Dimensional Manifolds

The Virtually Haken Conjecture A Haken 3-manifold is a compact 3-dimensional manifold M which is irreducible (in a certain strong sense) but contains an incompressible surface S. (An embedded surface S is incompressible if the embedding indices an injection of its … Continue reading

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