English

The Gauss-Lucas Theorem

Complex Variables 2021-12-02 v1

Abstract

The Gauss-Lucas theorem says that for any complex polynomial PP, the roots of the derivative PP' lie in the convex hull of the roots of PP. In other words, the roots of PP' lie inside the smallest convex subset of the complex plane containing all the roots of PP. This theorem is not hard to prove, but is there an intuitive explanation? In fact there is, using physics -- or more precisely, electrostatics in 2-dimensional space

Cite

@article{arxiv.2112.00110,
  title  = {The Gauss-Lucas Theorem},
  author = {John C. Baez},
  journal= {arXiv preprint arXiv:2112.00110},
  year   = {2021}
}

Comments

2 pages, one picture by Greg Egan

R2 v1 2026-06-24T07:58:40.011Z