A delayed interior area-to-height estimate for the Curve Shortening Flow

Abstract: In (Sobnack & Topping; 2024a, 2024b), Topping & the author proposed the principle of 'delayed parabolic regularity' for the Curve Shortening Flow; in (Sobnack & Topping, 2024a), they provided a handful of proper graphical situations in which their delayed regularity framework is valid. In this paper, we show that there holds an interior graphical estimate for the Curve Shortening Flow in the spirit of the proposed framework. More precisely, we show the following $ \mathrm{L}^1_\mathrm{loc} $-to-$ \mathrm{L}^\infty_\mathrm{loc} $ estimate: If a smooth Graphical Curve Shortening Flow $ u : (-1, 1) \times [0, T) \mapsto \mathbb{R} $ starts from a function $ u_0 := u( \, \cdot \, , 0) : (-1, 1) \mapsto \mathbb{R} $ with $ \mathrm{L}^1(!(-1,1)!) $ norm strictly less than $ \pi T $, then after waiting for the 'magic time' $ t_\star : = | u_0 |{\mathrm{L}^1(!(-1,1)!)} / \pi $, the size $ |u(0, t)| $ of $ u( \, \cdot \, , t) $ at the origin at any time $ t \in (t\star, T) $ is controlled purely in terms of $ | u_0 |{\mathrm{L}^1(!(-1,1)!)} $ and $ t - t\star $. We apply our estimate to construct Graphical Curve Shortening Flows starting weakly from Radon measures without point masses.