Motion by Curvature of Planar Networks

TL;DR

This paper studies the evolution of planar networks of curves with triple junctions under curvature flow, establishing existence, uniqueness, and regularity results relevant for modeling grain boundary growth.

Contribution

It provides the first detailed analysis of curvature flow for networks with multiple junctions, focusing on the case of three curves meeting at a single point.

Findings

Existence and uniqueness of the flow for the network.

Global regularity results for the evolution.

Insights into the behavior of networks with triple junctions.

Abstract

We consider the motion by curvature of a network of smooth curves with multiple junctions in the plane, that is, the geometric gradient flow associated to the length functional. Such a flow represents the evolution of a two--dimensional multiphase system where the energy is simply the sum of the lengths of the interfaces, in particular it is a possible model for the growth of grain boundaries. Moreover, the motion of these networks of curves is the simplest example of curvature flow for sets which are ``essentially'' non regular. As a first step, in this paper we study in detail the case of three curves in the plane concurring at a single triple junction and with the other ends fixed. We show some results about the existence, uniqueness and, in particular, the global regularity of the flow, following the line of analysis carried on in the last years for the evolution by mean curvature of smooth curves and hypersurfaces.