Generalised continuation by means of right limits

Several theories have been proposed to generalise the concept of analytic continuation to holomorphic functions of the disc for which the circle is a natural boundary. Elaborating on Breuer-Simon's work on "right limits" of power series, Baladi-Marmi-Sauzin recently introduced the notion of "renascent right limit" and "rrl-continuation". We discuss a few examples and consider particularly the classical example of "Poincar{é} simple pole series" in this light. These functions are represented in the disc as series of infinitely many simple poles located on the circle; they appear for instance in small divisor problems in dynamics. We prove that any such function admits a unique rrl-continuation, which coincides with the function obtained outside the disc by summing the simple pole expansion. We also discuss the relation with monogenic regularity in the sense of Borel.

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