Interface behavior for the solutions of a mass conserving free boundary problem modelling cell polarization

Abstract

We consider a parabolic nonlocal free boundary problem that has been derived as a limit of a bulk-surface reaction-diffusion system which models cell polarization. In previous papers Logioti, Niethammer, Röger, Velázquez (2021, 2023) we have established well-posedness of this problem and derived conditions on the initial data that imply continuity of the free boundary as $t\to 0$. In this paper we extend the qualitative study of the free boundary by considering axisymmetric data. Under additional monotonicity assumptions on the data we prove global continuity of the free boundary. On the other hand, if the initial data violate a “no-fattening” condition we show that the free boundary can oscillate as $t\to 0$.