Heat content asymptotics of some random Koch type snowflakes

We consider the short time asymptotics of the heat content $E$ of a domain $D$ of $\mathbb{R}^d$. The novelty of this paper is that we consider the situation where $D$ is a domain whose boundary $\partial D$ is a random Koch type curve. When $\partial D$ is spatially homogeneous, we show that we can recover the lower and upper Minkowski dimensions of $\partial D$ from the short time behaviour of $E(s)$. Furthermore, in some situations where the Minkowski dimension exists, finer geometric fluctuations can be recovered and the heat content is controlled by $s^αe^{f(\log(1/s))}$ for small $s$, for some $α\in (0, \infty)$ and some regularly varying function $f$. The function $f$ is not constant is general and carries some geometric information. When $\partial D$ is statistically self-similar, then the Minkowski dimension and content of $\partial D$ typically exist and can be recovered from $E(s)$. Furthermore, the heat content has an almost sure expansion $E(s) = c s^α N_\infty + o(s^α)$ for small $s$, for some $c$ and $α\in (0, \infty)$ and some positive random variable $N_\infty$ with unit expectation arising as the limit of some martingale.

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