- Alef Corner: Math Collaboration
- Alef’s Corner: Math Collaboration 2
- To cheer you up in difficult times 11: Immortal Songs by Sabine Hossenfelder and by Tom Lehrer
- To cheer you up in difficult times 10: Noam Elkies’ Piano Improvisations and more
- Quantum Matters
- To cheer you up in difficult times 9: Alexey Pokrovskiy proved that Rota’s Basis Conjecture holds asymptotically
- To Cheer you up in Difficult Times 8: Nathan Keller and Ohad Klein Proved Tomaszewski’s Conjecture on Randomly Signed Sums
- Noam Lifshitz: A new hypercontractivity inequality — The proof!
- To cheer you up in difficult times 7: Bloom and Sisask just broke the logarithm barrier for Roth’s theorem!
Top Posts & Pages
- TYI 30: Expected number of Dice throws
- Quantum Matters
- Gil's Collegial Quantum Supremacy Skepticism FAQ
- To Cheer you up in Difficult Times 8: Nathan Keller and Ohad Klein Proved Tomaszewski's Conjecture on Randomly Signed Sums
- Answer: Lord Kelvin, The Age of the Earth, and the Age of the Sun
- A sensation in the morning news - Yaroslav Shitov: Counterexamples to Hedetniemi's conjecture.
- Elchanan Mossel's Amazing Dice Paradox (your answers to TYI 30)
- Extremal Combinatorics IV: Shifting
- Are Natural Mathematical Problems Bad Problems?
Tag Archives: Borsuk’s conjecture
Borsuk asked in 1933 if every bounded set K of diameter 1 in can be covered by d+1 sets of smaller diameter. A positive answer was referred to as the “Borsuk Conjecture,” and it was disproved by Jeff Kahn and me in 1993. … Continue reading
The news in brief Andriy V. Bondarenko proved in his remarkable paper The Borsuk Conjecture for two-distance sets that the Borsuk’s conjecture is false for all dimensions greater than 65. This is a substantial improvement of the earlier record (all dimensions … Continue reading
Problem: Let P be a polytope in with n facets. Is it always true that P can be covered by n sets of smaller diameter? I also asked this question over mathoverflow, with some background and motivation.
Greetings to all! Karol Borsuk conjectured in 1933 that every bounded set in can be covered by sets of smaller diameter. In a previous post I described the counterexample found by Jeff Kahn and me. I will devote a few posts … Continue reading
Cocycles Definition: A -cocycle is a collection of -subsets such that every -set contains an even number of sets in the collection. Alternative definition: Start with a collection of -sets and consider all -sets that contain an odd number of members … Continue reading
Andrei Raigorodskii (This post follows an email by Aicke Hinrichs.) In a previous post we discussed the following problem: Problem: Let be a measurable subset of the -dimensional sphere . Suppose that does not contain two orthogonal vectors. How large … Continue reading
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