On bifurcating time-periodic flow of a Navier-Stokes liquid past a cylinder (Q303708)

According to the abstract of the paper, the author provides general sufficient conditions for the existence and uniqueness of branching out of a time-periodic family of solutions from steady-state solutions to the 2D Navier-Stokes equations in the exterior of a cylinder. Be separating the time-independent averaged component of the velocity field from its oscillatory one, the problem can be formulated as a coupled elliptic-parabolic nonlinear system in appropriate and distinct function spaces, with the property that the relevant linearized operators become Fredholm of order \(0\). In this functional setting, the notorious difficulty of \(0\) being in the essential spectrum disappears.