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Glaeser's continuity theorem

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In mathematical analysis, Glaeser's continuity theorem is a characterization of the continuity of the derivative of the square roots of functions of class . It was introduced in 1963 by Georges Glaeser,[1] and was later simplified by Jean Dieudonné.[2]

The theorem states: Let be a function of class in an open set U contained in , then is of class in U if and only if its partial derivatives of first and second order vanish in the zeros of f.

References

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  1. ^ Glaeser, Georges (1963). "Racine carrée d'une fonction différentiable". Annales de l'Institut Fourier. 13 (2): 203–210. doi:10.5802/aif.146.
  2. ^ Dieudonné, Jean (1970). "Sur un théorème de Glaeser". Journal d'Analyse Mathématique. 23: 85–88. doi:10.1007/BF02795491. Zbl 0208.07503.