On some nonlinear elliptic Dirichlet problems with lower order terms

This Ph.D. Thesis is devoted to boundary value problems associated to some classes of second order nonlinear elliptic PDEs in bounded open subsets of R^N. More precisely, we consider, first, two classes of noncoercive Dirichlet problems and we study the regularizing effect of a lower order term of power type on the summability properties of solutions. Then, for one class, we investigate the asymptotic behaviour of solutions as the power goes to infinity, while, for the other, we analyse local properties of solutions depending on local properties of data (with and without the lower order term of power type). Finally, the last topic is also studied for a class of nonlinear elliptic Dirichlet problems with a singular nonlinearity.