Tensor products of graphs can require fewer colors than their factors:

This short new preprint by Yaroslav Shitov gives counterexamples to Hedetniemi’s conjecture ( from 1966. In a new blog post ( Gil Kalai explains the construction.

Sign in to participate in the conversation

The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!