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arXiv 0709.0274math.DGmath.AP
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曲率有下界子流形的外内蕴等周分析

Extrinsic Isoperimetric Analysis on Submanifolds with Curvatures Bounded from Below

Steen Markvorsen, Vicente Palmer

摘要:

得到了径向截面曲率有下界的周围空间中子流形的外球的等周向量的上界。子流形本身仅被假定为具有下界的中曲率的径向部分的向量场和上的径向部分的内在单位法线的边界处的外在球,分别。同样,我们也建立了外部球中布朗运动的平均退出时间的下界。在这些情况下,我们可以将我们的分析一直延伸到无穷大,我们应用容量比较技术来获得子流形是抛物的充分条件,即保证任何布朗粒子在整个子流形中自由移动的条件,最终必然以概率1重新访问其起点的任何给定邻域。本文的结果是在一个粗略的意义上的对偶本作者以前得到的类似结果在互补的设置,我们假设的曲率有界从上面。

英文摘要:

We obtain upper bounds for the isoperimetric quotients of extrinsic balls of submanifolds in ambient spaces which have a lower bound on their radial sectional curvatures. The submanifolds are themselves only assumed to have lower bounds on the radial part of the mean curvature vector field and on the radial part of the intrinsic unit normals at the boundaries of the extrinsic spheres, respectively. In the same vein we also establish lower bounds on the mean exit time for Brownian motion in the extrinsic balls. In those cases, where we may extend our analysis to hold all the way to infinity, we apply a capacity comparison technique to obtain a sufficient condition for the submanifolds to be parabolic, i.e. a condition which will guarantee that any Brownian particle, which is free to move around in the whole submanifold, is bound to eventually revisit any given neighborhood of its starting point with probability 1. The results of this paper are in a rough sense dual to similar results obtained previously by the present authors in complementary settings where we assume that the curvatures are bounded from above.

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