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Dietrich Burde
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Such fields are related to real-closed fields, which satisfy even a stronger property. A field $K$ is called real-closed, if it is formally real, i.e., $-1$ is a sum of squares in $K$, and no proper algebraic extension is formally real. Then we have the following result:

Theorem: In a real-closed field, every polynomial of odd degree $>1$ has a root.

As a consequence, in a real-closed field, every polynomial splits into linear and quadratic factors. Of course, "cubically closed fields" are more general than real-closed fields, but nevertheless this might give a direction to search for characterisations, and there is a large literature on real-closed fields.

Dietrich Burde
  • 12.1k
  • 1
  • 33
  • 66