Tensor products of graphs can require fewer colors than their factors: arxiv.org/abs/1905.02167

This short new preprint by Yaroslav Shitov gives counterexamples to Hedetniemi’s conjecture (en.wikipedia.org/wiki/Hedetnie) from 1966. In a new blog post (gilkalai.wordpress.com/2019/05) Gil Kalai explains the construction.

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.

Use $ and $ for inline LaTeX, and $ and $ for display mode.