- Rademacher's theorem
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In mathematical analysis, Rademacher's theorem, named after Hans Rademacher, states the following: If U is an open subset of Rn and
- f : U → Rm
is Lipschitz continuous, then f is Fréchet-differentiable almost everywhere in U (i.e. the points in U at which f is not differentiable form a set of Lebesgue measure zero).
Generalizations
There is a version of Rademacher's theorem that holds for Lipschitz functions from a Euclidean space into an arbitrary metric space in terms of metric differentials instead of the usual derivative.
References
- Juha Heinonen, Lectures on Lipschitz Analysis, Lectures at the 14th Jyväskylä Summer School in August 2004. (Rademacher's theorem with a proof is on page 18 and further.)
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