Real Taylor shifts and simultaneous approximation

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AbstractWe are interested in the Taylor shift operator acting on the space of infinitely differentiable functions. In particular if we choose a countable family of centers of Taylor expansion, we prove that the associated family of real Taylor shifts fulfills the approximation of any given family of infinitely differentiable functions with a common subsequence of iterates applied on a common vector. We obtain similar conclusions in the context of universal series improving recent statements. Finally we introduce the notion of doubly universal Taylor shift. All these results give new and natural examples of disjoint universality.