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Homogenization of a generalized Stefan Problem in the context of ergodic algebras

We address the deterministic homogenization, in the general context of ergodic algebras, of a doubly nonlinear problem which generalizes the well known Stefan model, and includes the classical porous medium equation. It may be represented by the differential inclusion, for a real-valued function $u(x,t)$, $$ \frac{\partial}{\partial t}\partial_u Ψ(x/\ve,x,u)-\nabla_x\cdot \nabla_ηψ( x/\ve,x,t,u,\nabla u) \ni f(x/\ve,x,t, u), $$ on a bounded domain $\Om\subset \R^n$, $t\in(0,T)$, together with initial-boundary conditions, where $Ψ(z,x,\cdot)$ is strictly convex and $ψ(z,x,t,u,\cdot)$ is a $C^1$ convex function, both with quadratic growth, satisfying some additional technical hypotheses. As functions of the oscillatory variable, $Ψ(\cdot,x,u),ψ(\cdot,x,t,u,η)$ and $f(\cdot,x,t,u)$ belong to the generalized Besicovitch space $\BB^2$ associated with an arbitrary ergodic algebra $Å$. The periodic case was addressed by Visintin (2007), based on the two-scale convergence technique. Visintin's analysis for the periodic case relies heavily on the possibility of reducing two-scale convergence to the usual $L^2$ convergence in the cartesian product $Π\X\R^n$, where $Π$ is the periodic cell. This reduction is no longer possible in the case of a general ergodic algebra. To overcome this difficulty, we make essential use of the concept of two-scale Young measures for algebras with mean value, associated with bounded sequences in $L^2$.