Fourier levels and almost sure bounds on higher-order derivatives in first-passage percolation

The variance of first-passage percolation admits a decomposition into Fourier levels indexed by the order of environment derivatives. These Fourier levels capture how local perturbations of different orders contribute to global fluctuations. In this paper, we investigate higher-order environment derivatives and their Fourier-level structure. We prove that derivatives of orders $k\in\{2,3,4\}$ are almost surely bounded below by $-\binom{k-2}{\lceil\frac{k-2}2\rceil}$ and above by $\binom{k-2}{\lceil\frac{k-2}2\rceil}$. We conjecture that these are the correct bounds for all $k$, and we construct explicit environments showing that these extreme values can indeed be attained.