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Immersions isométriques elliptiques et courbes pseudo-holomorphes. (Elliptic isometric immersions and pseudo-holomorphic curves). (French) Zbl 0682.53063
In this article result of A. V. Pogorelov [from “Extrinsic geometry of convex surfaces”, translated from the Russian by Israel Program for Scientific Translations, translations of Mathematical Monographs, Am. Math. Soc. VI (1973; Zbl 0311.53067)] are generalized and some of the proofs are shortened.
Let S and M be oriented Riemannian manifolds of dimension 2 and 3, respectively. Then a suitable open part O of the 1-jet-bundle of isometric immersions f: $$S\to M$$ can be equipped with a canonical almost complex structure J. If f is elliptic $$(=locally$$ convex), i.e. the determinant of its shape operator is strictly positive, then its 1-jet is a pseudo-holomorphic curve in (O,J). Using Gromov’s generalization of Schwarz’s Lemma the author derives theorems on the convergence of sequences of pseudo-holomorphic maps which, applied to elliptic isometric immersions, give the basic tool of the article. First he can simplify the proof of Pogorelov’s theorem which states: If the sectional curvature $$K_ S$$ and $$K_ M$$ of S and M satisfy $$K_ M\leq K_ 0<K_ S$$ with some $$K_ 0\in {\mathbb{R}}$$ and S is homeomorphic to a sphere, then S can isometrically be immersed into M. Next he generalizes this result in the case that M is simply connected and S is metrically complete and homeomorphic to an open part of a sphere; under the same curvature condition then even S can isometrically be embedded into M.
Using pseudo-holomorphic curves the author can also shorten the proof of Pogorelov’s theorem on the infinitesimal rigidity of elliptic isometric immersions f: $$S\to M$$ with compact S.
Reviewer: H.Reckziegel

##### MSC:
 53C40 Global submanifolds 53C45 Global surface theory (convex surfaces à la A. D. Aleksandrov) 53C55 Global differential geometry of Hermitian and Kählerian manifolds
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