MiS Preprint Repository

We are interested in the thin-film equation with zero-contact angle and quadratic mobility, modeling the spreading of a thin liquid film, driven by capillarity and limited by viscosity in conjunction with a Navier-slip condition at the substrate. This degenerate fourth-order parabolic equation has the contact line as a free boundary. From the analysis of the self-similar source-type solution, one expects that the solution is smooth only as a function of two variables $(x,x^{\beta })$ (where $x$ denotes the distance from the contact line) with $\beta =\frac{\sqrt{13}-1}{4}\approx 0.6514$ irrational. Therefore, the well-posedness theory is more subtle than in case of linear mobility (coming from Darcy dynamics) or in case of the second-order counterpart (the porous medium equation).

Here, we prove global existence and uniqueness for one-dimensional initial data that are close to traveling waves. The main ingredients are maximal regularity estimates in weighted $L^2$-spaces for the linearized evolution, after suitable subtraction of $a(t)+b(t)x^{\beta }$-terms.