This authoritative book presents recent research results on nonlinear problems with lack of compactness. The topics covered include several nonlinear problems in the Euclidean setting as well as variational problems on manifolds. The combination of deep techniques in nonlinear analysis with applications to a variety of problems make this work an essential source of information for researchers and graduate students working in analysis and PDE's.

These two volumes present the collected works of James Serrin. He did seminal work on a number of the basic tools needed for the study of solutions of partial differential equations. Many of them have been and are being applied to solving problems in science and engineering. Among the areas which he studied are maximum principle methods and related phenomena such as Harnack's inequality, the compact support principle, dead cores and bursts, free boundary problems, phase transitions, the symmetry of solutions, boundary layer theory, singularities and fine regularity properties. The volumes include commentaries by leading mathematicians to indicate the significance of the articles and to discuss further developments along the lines of these articles.

Maximum principles are bedrock results in the theory of second order elliptic equations. This principle, simple enough in essence, lends itself to a quite remarkable number of subtle uses when combined appropriately with other notions. Intended for a wide audience, the book provides a clear and comprehensive explanation of the various maximum principles available in elliptic theory, from their beginning for linear equations to recent work on nonlinear and singular equations.

A conference, to celebrate the 65th birthday of Professor James Serrin, was held at the University of Ferrara from 26 to 30 October 1992, on the occasion of the sixth centenary of the foundation of the university. The dual purpose of this conference was to honor James Serrin and to bring together mathematicians in four main areas of Professor Serrin's research in terests: partial differential equations, variational methods, fluid mechanics, and thermodynamics. These fields, with their significant historical connotation, still remain the object of active research and development, and possess a remarkable degree of interrelation in their pure and applied aspects. Thus the organizing committee, consisting of G. Buttazzo, G.P. Galdi, E. Lanconelli, and P. Pucci, had the opportunity to invite a number of well-known mathematicians and friends of James Serrin to make this meeting a success. An honorary committee was also formed, including Professor A. Rossi, Rector of the University of Ferrara, Professor C. Bighi, President of the Accadernia Scienze di Ferrara, Professor G. Del Piero, Decano of the Faculty of Engineering of the University of Ferrara, and Professor L. Zanghirati, Director of the Department of Mathematics of the University of Ferrara. The conference was further supported by G.N.A.F.A., G.N.F.M., and the Mathematics Committee of the Consiglio Nazionale delle Ricerche, together with the University of Ferrara and the Cassa di Risparrnio of Ferrara, to all of whom the organizing committee expresses their most sincere thanks."

These two volumes present the collected works of James Serrin. He did seminal work on a number of the basic tools needed for the study of solutions of partial differential equations. Many of them have been and are being applied to solving problems in science and engineering. Among the areas which he studied are maximum principle methods and related phenomena such as Harnack's inequality, the compact support principle, dead cores and bursts, free boundary problems, phase transitions, the symmetry of solutions, boundary layer theory, singularities and fine regularity properties. The volumes include commentaries by leading mathematicians to indicate the significance of the articles and to discuss further developments along the lines of these articles.

This book demonstrates the influence of geometry on the qualitative behaviour of solutions of quasilinear PDEs on Riemannian manifolds. Motivated by examples arising, among others, from the theory of submanifolds, the authors study classes of coercive elliptic differential inequalities on domains of a manifold M with very general nonlinearities depending on the variable x, on the solution u and on its gradient. The book highlights the mean curvature operator and its variants, and investigates the validity of strong maximum principles, compact support principles and Liouville type theorems. In particular, it identifies sharp thresholds involving curvatures or volume growth of geodesic balls in M to guarantee the above properties under appropriate Keller-Osserman type conditions, which are investigated in detail throughout the book, and discusses the geometric reasons behind the existence of such thresholds. Further, the book also provides a unified review of recent results in the literature, and creates a bridge with geometry by studying the validity of weak and strong maximum principles at infinity, in the spirit of Omori-Yau's Hessian and Laplacian principles and subsequent improvements.