Counterexamples to Hedetniemi's conjecture

@article{Shitov2019CounterexamplesTH,
  title={Counterexamples to Hedetniemi's conjecture},
  author={Yaroslav Shitov},
  journal={Annals of Mathematics},
  year={2019}
}
  • Y. Shitov
  • Published 2019
  • Mathematics
  • Annals of Mathematics
The chromatic number of $G\times H$ can be smaller than the minimum of the chromatic numbers of finite simple graphs $G$ and $H$. 
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