In this paper, local, global, strongly local and strongly global supportings of subsets in a complete simply connected smooth Riemannian manifold without focal points are defined. Sufficient conditions for convexity of subsets in the same sort of manifolds have been derived in terms of the above mentioned types of supportings.
@article{118601, author = {M. Beltagy}, title = {Sufficient conditions for convexity in manifolds without focal points}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {34}, year = {1993}, pages = {443-449}, zbl = {0797.53034}, mrnumber = {1243076}, language = {en}, url = {http://dml.mathdoc.fr/item/118601} }
Beltagy, M. Sufficient conditions for convexity in manifolds without focal points. Commentationes Mathematicae Universitatis Carolinae, Tome 34 (1993) pp. 443-449. http://gdmltest.u-ga.fr/item/118601/
Foot points and convexity in manifolds without conjugate points, Bull. Calcutta Math. Soc. 82 (1990), 338-348. (1990) | MR 1134214 | Zbl 0749.53033
Geometry of Manifolds, Academic Press, New York, 1964. | MR 0169148 | Zbl 0984.53001
Tight immersion into manifolds without conjugate points, Quart. J. Math. Oxford (2) 23 (1982), 159-267. (1982) | MR 0657122
Sufficient criteria of convexity, J. Soviet Math. (10) 3 (1978), 395-435. (1978) | Zbl 0389.52001
Horospheres and the stable part of the geodesic flow, Math. Z. 153 (1977), 237-251. (1977) | MR 0440605 | Zbl 0332.53028
Manifolds without focal points, J. Diff. Geom. 13 (1978), 341-359. (1978) | MR 0551564 | Zbl 0424.53021
Geometry and convexity, John Wiley & Sons, Inc., New York, 1979. | MR 0534615 | Zbl 0409.52001
Convex Sets, McGraw-Hill, New York, 1964. | MR 0170264 | Zbl 0333.52001