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Title: Solitons of geometric flows and their applications
Author: Helmensdorfer, Sebastian
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2012
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In this thesis we construct solitons of geometric flows with applications in three different settings. The first setting is related to nonuniqueness for geometric heat flows. We show that certain double cones in Euclidean space have several self-expanding evolutions under mean curvature flow. The construction of the associated self-expanding solitons leads to an application in fluid dynamics. We present a new model for the behaviour of oppositely charged droplets of fluid, based on the mean curvature flow of double cones. If two oppositely charged droplets of fluid are close to each other, they start attracting each other and touch eventually. Surprisingly, experiments have shown, that if the strength of the charges is high enough, then the droplets are repelled from each other, after making short contact. The constructed self-expanders can be used to correctly predict the experimental results, using our theoretical model. Secondly we employ space-time solitons of the mean curvature flow to give a geometric proof of Hamilton's Harnack estimate for the mean curvature flow. This proof is based on the observation that the associated Harnack quantity is the second fundamental form of a space-time self-expander. Moreover the self-expander is asymptotic to a cone over the convex initial hypersurface. Hence the self-expander can be seen as the mean curvature evolution of a convex cone, which we exploit to show that preservation of convexity directly implies the Harnack estimate. In the last chapter we study solutions of the mean curvature flow in a Ricci flow backgound. We show that the space-time track of such a solution can be seen as a soliton. Moreover the second fundamental form of this soliton matches the evolution of a functional, which is the analogue of G. Perelman's F-functional for the Ricci flow on a manifold with boundary and which also has relations to quantum gravity. Furthermore our construction provides a link between the Harnack estimate for the mean curvature flow and the Harnack estimate for the Ricci flow.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QA Mathematics ; QC Physics