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The metric projection onto the soul
Authors:Luis Guijarro  Gerard Walschap
Institution:Department of Mathematics, University of Pennsylvania, Philadelphia, Pennsylvania 19104 ; Department of Mathematics, University of Oklahoma, Norman, Oklahoma 73019
Abstract:We study geometric properties of the metric projection $\pi :M\to S$ of an open manifold $M$ with nonnegative sectional curvature onto a soul $S$. $\pi $ is shown to be $C^{\infty }$ up to codimension 3. In arbitrary codimensions, small metric balls around a soul turn out to be convex, so that the unit normal bundle of $S$ also admits a metric of nonnegative curvature. Next we examine how the horizontal curvatures at infinity determine the geometry of $M$, and study the structure of Sharafutdinov lines. We conclude with regularity properties of the cut and conjugate loci of $M$.

Keywords:Sharafutdinov retraction  soul  pseudosoul  convexity
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