Enhanced Dissipation under Variable Growth: Stochastic $p(x)$-Laplace Equations with Transport Noise

Source abstract

We study dissipation enhancement for stochastic $p(x)$-Laplace equations with divergence-free transport noise on $\mathbb T^d$, $d\ge2$. Under log-Hölder continuity and degenerate subcritical growth, we establish global variational well-posedness and an exact energy identity. For every prescribed positive coefficient, suitable transport noise yields averaged algebraic decay uniformly on bounded zero-mean $L^2$ balls. The noise is independent of the individual initial datum. This uniform enhancement holds despite the absence of homogeneous scaling and the two flux growth regimes associated with the variable exponent. We also identify $p^+$ as the optimal exponent for uniform modular coercivity near zero and obtain a strict averaged comparison with the unperturbed evolution at any prescribed time $T\ge1$ on initial-data shells with bounded gradient modular. For each prescribed decay rate and finite moment order, deterministic stepwise Fourier profiles with fixed intensity and increasing frequency range give exponential decay of the $L^2$ norm in mean square and almost surely. The absolute random prefactors have uniformly bounded moments of the prescribed order throughout the initial-data ball.