  The Fisher-Kolmogorov-Petrovsky-Piskunov (FKPP) equation provides a
mean-field theory of out-of-time-ordered commutators in locally interacting
quantum chaotic systems at high energy density; in the systems with power-law
interactions, the corresponding fractional-derivative FKPP equation provides an
analogous mean-field theory. However, the fractional FKPP description is
potentially subject to strong quantum fluctuation effects, so it is not clear a
priori if it provides a suitable effective description for generic chaotic
systems with power-law interactions. Here we study this problem using a model
of coupled quantum dots with interactions decaying as $\frac{1}{r^{\alpha}}$,
where each dot hosts $N$ degrees of freedom. The large $N$ limit corresponds to
the mean-field description, while quantum fluctuations contributing to the OTOC
can be modeled by $\frac{1}{N}$ corrections consisting of a cutoff function and
noise. Within this framework, we show that the parameters of the effective
theory can be chosen to reproduce the butterfly light cone scalings that we
previously found for $N=1$ and generic finite $N$. In order to reproduce these
scalings, the fractional index $\mu$ in the FKPP equation needs to be shifted
from the na\"ive value of $\mu = 2\alpha - 1$ to a renormalized value $\mu =
2\alpha - 2$. We provide supporting analytic evidence for the cutoff model and
numerical confirmation for the full fractional FKPP equation with cutoff and
noise.
