Introduction

The mathematical interests of Prof. Daniel B. Henry extended over a broad area of the field of Differential Equations. His first works dealt with the theory of Linear Functional Differential Equations, starting with his PhD Thesis, written under the supervision of Prof. Jack K. Hale at Brown University. Prof. Henry became worldwide known, however, after the publication of his seminal book 'Geometric Theory of Semilinear Parabolic Equations' in which he not only masterfully reviewed what was known about the subject but also made fundamental new contributions in many directions. This book became a classic in the area and an almost mandatory reference for most of the subsequent work in the field of infinite dimensional dynamical systems. As an additional evidence of its importance, the book, first published in the 'Lecture notes' of Springer-Verlag in 1981, has been translated into Russian and Chinese.

The subsequent works of Dan Henry also have had a great impact in the field and contributed to consolidate his reputation in the mathematical community. This recognition is even more remarkable for anyone who knew his lack of disposition to travel and his reluctance to publish anything ranked (by his very high standards) as less than important and completely polished material. These personal characteristics prevented a more widespread knowledge of his research and made it difficult to appreciate the real importance and amplitude of his work.

The recent publication of the book 'Perturbation of the boundary for boundary-value problems of partial differential equations' by Academic Press, containing the results of many years of his research on the effects of the variation of the domain on the solutions of boundary value problems, will certainly contribute to a better divulgation of a significant part of his work. However, many of Prof. Henry's writings remain unpublished, despite considerable encouragement and persistent appeals from his colleagues, friends and students. Prof. Henry often chose to keep his work in handwritten form, often handed out as notes during his lectures and classes. Due to their high quality the interest for Prof. Henry's manuscripts reached a much larger public than originally intended. However still comparatively few privileged have had access to these manuscripts and have thus been able to enjoy their insightfulness and elegance (and occasionally Prof Henry's peculiar sense of humor).

After his untimely death in May 2002, some of his friends decided to render a last homage to this great man and his passion for the Mathematical Science by compiling and digitalizing all his available manuscripts. In this way they hope to make them accessible to anyone who shares, at least in part, Prof Henry's lifelong passion for the subject. Both research works and class notes have been included. Some papers already published have also been included to give a better idea of the diversity of his interests.

The primary purpose of the organizers is the homage but, in addition, they believe this collection also represents a significant contribution to the research in the area.

As a kind of 'bonus' some texts written under the pseudonymous of 'Lor Martinelli' and referred to as 'my science-fiction texts' by Prof. Henry have also been included. They contain a very personal vision of the future of the human race and its incursions in the outer space. It is the organizer's belief that these writings, besides representing an interesting counterpoint, also show clearly Prof. Henry's intellectual integrity and his firm belief in the power of human reason. These convictions extended far beyond the strict mathematical scope and we have witnessed he keeping them till the end, never accepting any possible comfort from any source that he considered illusory, even in the darkest moments of his long illness.

To conclude, the organizers would like to thank all friends and colleagues who contributed in a way or another to this project and to encourage workers in the field to use its content. They are convinced that this is the best possible tribute one could render to Prof. Henry's memory.

Sergio Oliva
Antonio Luiz Pereira
February 2006