It has been known, since the pioneering works by Serre, Hoff, Vaǐgant-Kazhikhov, Lions and Feireisl, among others, the regularizing properties
of the effective viscous flux and its characterization as the function whose gradient is the gradient part in the Hodge decomposition of the Newtonian force of
the fluid, when the shear viscosity of the fluid is constant. In this article, we
explore further the connection between the Hodge decomposition of the Newtonian force and the regularizing properties of its gradient part, by addressing
the problem of the global existence of weak solutions for compressible Navier-Stokes equations with both viscosities depending on a spatial mollification of
the density.
