EXISTENCE OF ENTROPY SOLUTIONS FOR SOME QUASILINEAR ANISOTROPIC ELLIPTIC UNILATERAL PROBLEMS WITH VARIABLE EXPONENTS

In this paper, we shall be concerned with the study of the following quasilinear anisotropic elliptic Dirichlet problems of the type - div a(x, u, backward difference u) = f - div F in omega, (1) where f is an element of L1(omega) and F is an element of pi Ni=1 Lp0i(center dot)(omega), and ai(x, u, xi) are Carathe ' o dory functions from omega x IR x IRN into IR , which satisfy assumptions of growth, coercivity and strict monotonicity. We prove the existence of entropy solutions for the quasilinear elliptic equation associated to the unilateral problem by re-lying on the penalization method, in the anisotropic variable exponent Sobolev spaces. Our approach is also based on the techniques of monotone operators in Banach spaces, the existence of weak solutions, and some approximations methods. The problems of the type (1) are very interesting from the purely mathematical point of view. On the other hand, such equations (1) appear in different contexts, in particular, the mathematical description of motions of the non-newtonien fluids; we quote for instance the electro-rheological fluids; the deformation of membrane constrained by an obstacle, the image processing and other various physical applications.