Free boundaries in problems with hysteresis
  In this note we present a survey concerning parabolic free boundary problems involving a discontinuous hysteresis operator. Such problems describe biological and chemical processes "with memory" in which various substances interact according to hysteresis law.   Our main objective is to discuss the structure of the free boundaries and the properties of the so-called "strong solutions" belonging to the anisotropic Sobolev class $W^{2,1}_q$ with sufficiently large $q$. Several open problems in this direction are proposed as well. 
D.E. Apushkinskaya and N.N. Uraltseva
math.AP