Large Deviations for the Two-Dimensional Dean-Kawasaki Equation with Coulomb Interactions
We establish global well-posedness and a small-noise large deviation principle for the two-dimensional Dean-Kawasaki equation with Coulomb interaction $\partial_tρ^\varepsilon=Δρ^\varepsilon-\nabla\cdot(ρ^\varepsilon(V*ρ^\varepsilon))-\sqrt{\varepsilon}\nabla\cdot(\sqrt{ρ^\varepsilon}\circξ^{K(\varepsilon)})$, where $V=λ_V(\cos(α_V)\nabla G+\sin(α_V)J\nabla G)$. Here $λ_V\geq0$ is the interaction strength, $α_V$ is the interaction angle, $G$ is the mean-zero Green function of $-Δ$ on $\mathbb{T}^2$, $J$ is rotation by $π/2$, and $ξ^K$ is a finite-mode approximation of space-time white noise. For finite-entropy initial data of mass $M$ satisfying $λ_V\max\{\cos(α_V),0\}M<8π$, the equation with the exact square-root coefficient is globally pathwise well posed at every finite Fourier cutoff in the class of stochastic kinetic solutions. Following Fehrman and Gess (arXiv:1910.11860), we prove a large deviation principle on $L^1((0,T)\times\mathbb{T}^2)$ under the scaling $K(\varepsilon)\to\infty$ and $\varepsilon K(\varepsilon)^4\to0$, with good rate function given by the quadratic control problem for the skeleton equation.