# Parabolic equations for curves on surfaces Part I. Curves with $p$-integrable curvature

### Abstract

This is the first of a two-part paper in which we develop a theory of parabolic equations for curves on surfaces which can be applied to the so-called curve shortening of flow-by-mean-curvature problem, as well as to a number of models for phase transitions in two dimensions. We introduce a class of equations for which the initial value problem is solvable for initial data with $p$-integrable curvature, and we also give estimates for the rate at which the $p$-norms of the curvature must blow up, if the curve becomes singular in finite time. A detailed discussion of the way in which solutions can become singular and a method for “continuing the solution through a singularity” will be the subject of the second part.

Sigurd Angenent