MathBB

MathBB Commons

A collection of mathematical writing shared by the MathBB community — explainers, short articles, notes on open problems, and more.

Welcome to MathBB

Help notebook with an overview of what you can do with MathBB and demo pages
knowledge base

The four color theorem

Talk slides: The four color theorem and reducibility as a two-player game Delivered at the MathFest 2026 session: Fifty years of the four color theorem
talk slidescombinatorics

The moving sofa problem

A talk on the famous moving sofa problem and the milestones that led to its solution in 2024 by Jineon Baek
talk slidesgeometry

An animated introduction to Plancherel measure

A talk on Plancherel measure, Young tableaux, jeu de taquin forests and more Delivered at Permutation Patterns 2026
talk slidesprobabilitycombinatorics

Jeu de taquin forests and the infinite RSK correspondence

A combinatorics talk given at the SIAM Conference on Discrete Mathematics, UC San Diego, July 2026
talk slidesprobabilitycombinatorics

The sphere packing problem

A short article explaining the *sphere packing problem*: a famous geometry problem that was solved in 2, 3, 8, and 24 Euclidean dimensions but is still open in all other dimensions
open problemsgeometry

The Basel problem

Two easy proofs of Euler's famous series infinite evaluation $$1 + \frac14 + \frac19 + \frac{1}{16} + \frac{1}{25} + \ldots = \frac{\pi^2}{6},$$ and a discussion of some of the far-reaching mathematics this identity relates to.
cool proofs

The Brouwer fixed point theorem

An explainer article about Brouwer's fixed point theorem. Includes a proof in the two-dimensional case using Sperner's lemma, a well-known combinatorial fact, and a discussion of the equivalence between Brouwer's fixed point theorem and other important facts such as the no retract theorem and the existence of a Nash equilibrium in two-player games.
cool proofsexplainersgeometry