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Durham University

Department of Mathematical Sciences


Publication details for Wilhelm Klingenberg

Guilfoyle, Brendan & Klingenberg, Wilhelm (2016). A Converging Lagrangian Flow in the Space of Oriented Line. Kyushu Journal of Mathematics 70(2): 343-351.

Author(s) from Durham


Under mean radius of curvature flow, a closed convex surface in Euclidean space is known to expand exponentially to infinity. In the three-dimensional case we prove that the oriented normals to the flowing surface converge to the oriented normals of a round sphere whose centre is the Steiner point of the initial surface, which remains constant under the flow.
To prove this we show that the oriented normal lines, considered as a surface in the space of all oriented lines, evolve by a parabolic flow which preserves the Lagrangian condition.Moreover, this flow converges to a holomorphic Lagrangian section, which forms the set of oriented lines through a point.
The coordinates of the Steiner point are projections of the support function into the first non-zero eigenspace of the spherical Laplacian and are given by explicit integrals of initial surface data.