# A simple proof of Kotake–Narasimhan theorem in some classes of ultradifferentiable functions

@article{Boiti2016ASP, title={A simple proof of Kotake–Narasimhan theorem in some classes of ultradifferentiable functions}, author={Chiara Boiti and David Jornet}, journal={Journal of Pseudo-Differential Operators and Applications}, year={2016}, volume={8}, pages={297-317} }

We give a simple proof of a general theorem of Kotake–Narasimhan for elliptic operators in the setting of ultradifferentiable functions in the sense of Braun, Meise and Taylor. We follow the ideas of Komatsu. Based on an example of Métivier, we also show that the ellipticity is a necessary condition for the theorem to be true.

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