Henri Berestycki 
Perspectives in Nonlinear Partial Differential Equations 

In celebration of Haim Brezis’s 60th birthday, a conference was held at the Ecole Polytechnique in Paris, with a program testifying to Brezis’s wide-ranging influence on nonlinear analysis and partial differential equations. The articles in this volume are primarily from that conference. They present a rare view of the state of the art of many aspects of nonlinear PDEs, as well as describe new directions that are being opened up in this field. The articles, written by mathematicians at the center of current developments, provide somewhat more personal views of the important developments and challenges. In his own work, Brezis has been a seminal influence in many important areas: critical growth in semi-linear equations, variational analysis of functionals in borderline compactness cases, vector valued equations, the Ginzburg-Landau theory, as well as generalized degree theory and fine properties of Sobolev spaces. This same breadth is reflected in the mathematics in this collection. Researchers in nonlinear partial differential equations will find much of interest in this volume.