[Math] Applications of Brouwer’s fixed point theorem

applicationsbig-listgn.general-topology

I'm presenting Brouwer's fixed point theorem to an audience that knows some point-set topology. Does anyone have any zippy / enlightening / cool applications or consequences of it? So far, I have:

  • Physical realizations: stuff involving maps of my city, crumpled pieces of graph paper, a stationary gin molecule in a cocktail shaker, etc.
  • That every n*n real matrix with all-positive entries has a positive eigenvalue.

Thanks! 🙂

Best Answer

The theorem is equivalent to the determinacy of the Hex game. That's a very famous `application'.

The details can be found in [David Gale (1979). "The Game of Hex and Brouwer Fixed-Point Theorem". The American Mathematical Monthly 86: 818–827], a beautiful paper, which JSTOR serves at http://www.jstor.org/stable/2320146.