Liouville's theorem (bounded entire functions)

Every entire function (holomorphic on the whole complex plane) that is bounded must be constant, so its derivative is zero. It is a standard tool in complex analysis for proving results such as the fundamental theorem of algebra.

\forall f\in\mathcal O(\mathbb C,\mathbb C)\colon\left(\sup_{z\in\mathbb C}|f(z)|<\infty\implies f'=0\right)

What the symbols mean

an entire function from the complex plane to the complex numbers
the set of holomorphic (entire) functions from the complex plane to the complex numbers
a complex number in the domain of f
the derivative of f
the supremum of the absolute value of f over the whole complex plane

About this formula

  • FieldMathematics
  • TopicComplex analysis
  • LevelUniversity
  • Also calledLiouville's boundedness theorem, bounded entire function is constant, entire function bounded implies constant, Liouville theorem complex analysis
  • SourceWikidata Q576478

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