We prove the existence and pointwise bounds of the Green functions for stationary Stokes systems with measurable coefficients in two dimensional domains. We also establish pointwise bounds of the derivatives of the Green functions under a regularity assumption on the $L_1$-mean oscillations of the coefficients.
We study the stationary Stokes system with Dini mean oscillation coefficients in a domain having $C^{1,rm{Dini}}$ boundary. We prove that if $(u, p)$ is a weak solution of the system with zero Dirichlet boundary condition, then $(Du,p)$ is continuous
up to the boundary. We also prove a weak type-$(1,1)$ estimate for $(Du, p)$.
We study Green functions for the pressure of stationary Stokes systems in a (possibly unbounded) domain $Omegasubset mathbb{R}^d$, where $dge 2$. We construct the Green function when coefficients are merely measurable in one direction and have Dini m
ean oscillation in the other directions, and $Omega$ is such that the divergence equation is solvable there. We also establish global pointwise bounds for the Green function and its derivatives when coefficients have Dini mean oscillation and $Omega$ has a $C^{1,rm{Dini}}$ boundary. Green functions for the flow velocity of Stokes systems are also considered.
We study Green functions for stationary Stokes systems satisfying the conormal derivative boundary condition. We establish existence, uniqueness, and various estimates for the Green function under the assumption that weak solutions of the Stokes syst
em are continuous in the interior of the domain. Also, we establish the global pointwise bound for the Green function under the additional assumption that weak solutions of the conormal derivative problem for the Stokes system are locally bounded up to the boundary. We provide some examples satisfying such continuity and boundedness properties.
We study stationary Stokes systems in divergence form with piecewise Dini mean oscillation coefficients and data in a bounded domain containing a finite number of subdomains with $C^{1,rm{Dini}}$ boundaries. We prove that if $(u, p)$ is a weak soluti
on of the system, then $(Du, p)$ is bounded and piecewise continuous. The corresponding results for stationary Navier-Stokes systems are also established, from which the Lipschitz regularity of the stationary $H^1$-weak solution in dimensions $d=2,3,4$ is obtained.
This paper is devoted to establishing the uniform estimates and asymptotic behaviors of the Greens functions $(G_varepsilon,Pi_varepsilon)$ (and fundamental solutions $(Gamma_varepsilon, Q_varepsilon)$) for the Stokes system with periodically oscilla
ting coefficients (including a system of linear incompressible elasticity). Particular emphasis will be placed on the new oscillation estimates for the pressure component $Pi_varepsilon$. Also, for the first time we prove the textit{adjustable} uniform estimates (i.e., Lipschitz estimate for velocity and oscillation estimate for pressure) by making full use of the Greens functions. Via these estimates, we establish the asymptotic expansions of $G_varepsilon, abla G_varepsilon, Pi_varepsilon$ and more, with a tiny loss on the errors. Some estimates obtained in this paper are new even for Stokes system with constant coefficients, and possess potential applications in homogenization of Stokes or elasticity system.