Introduction. The holomorphic self-homeomorphisms (automorphisms) of the open unit ball B, in ~L TM have long been known [1] - they are given by certain rational functions which are holomorphic on a neighborhood of Bn and induce a homeomorphism of the boundary, bB,, of the ball. Our first result can be viewed as a local characterization of these automorphisms: For n > 1, a nonconstant holomorphic mapping into ~ which is defined in a neighborhood of a point of bB, and which maps bB, into itself is necessarily an automorphism, or, more precisely, extends to be an automorphism. We apply this to obtain some information on the as yet unsettled question as to whether every proper holomorphic self-mapping of Bn is an automorphism. In particular, we recover (Cor. 1.1) a result of Pelles ([3, 5]). In the second part, we consider holomorphic mappings from polydiscs. According to a classical theorem of Poincar6, there exists no biholomorphism from the polydisc U z in C 2 with the ball B2. We obtain some integral formulas which yield a quantitative explanation of this phenomenon, Finally I wish to acknowledge that the above characterization of automorphisms may have been known to the late Professor L6wner, at least for two complex variables. I want to thank Professors L. Bers and C. Titus for this information on their oral communication with L6wner.
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