Abstract
Jean-Pierre Hansen was born on 10 May 1942 in Luxembourg, into a family of civil servants and engineers. He grew up in Differdange, close to the imposing steel-works, where his father was in charge of Europe's largest rolling mill. In the 50s he attended the Athénée Grand-Ducal de Luxembourg, and enjoyed massive injections of Latin and Mathematics. His early passions were Astronomy and History of Art, but he followed paternal advice and went up to the Université de Liège in Belgium to take a degree in Engineering. After two years, under the influence of the leading astrophysicist Paul Ledoux, he switched to Physics and graduated in July 1964 with highest honours. Despite an offer from Cambridge, JPH decided to move to Paris for his PhD. He went to the recently created Orsay Campus of the University of Paris to obtain a `Doctorat de Troisième Cycle' under the guidance of Bernard Jancovici and Dominique Levesque, with whom he wrote his first paper on a quantum Monte Carlo study of solid He3 and He4. He then became a student of Loup Verlet and prepared his PhD (Doctorat d'Etat) under Verlet's masterful guidance, and defended his thesis entitled Contribution à l'Etude des Systèmes de Lennard-Jones classiques et quantiques in June 1969; his thesis examination committee was presided over by Jacques Yvon. In 1967, JPH had been appointed attaché de recherche at the Centre National de la Recherche Scientifique (CNRS) and he was duly promoted to chargé de recherche upon obtaining his PhD. Philippe Nozières had been designated JPH's mentor (parrain) at CNRS, and was to have a lasting influence throughout the latter's career in France.
JPH spent the academic year 1970-71 as a postdoctoral research associate at Cornell University, where he interacted with Neil Ashcroft, Geoffrey Chester, Jim Krumhansl, Mark Nelkin, Roy Pollock and Ben Widom among others. He also learned the meaning of `Upper New York State winters'. Attending various conferences in the USA, including the 11th Statistical Mechanics Conference in Chicago and the Liquids Gordon Conference in New Hampshire, he met many of the founding fathers of modern liquid state theory including Lars Onsager, Berni Alder, Joel Lebowitz, Jerry Percus and Bob Zwanzig, as well as some of his contemporaries who shared similar interests and who were to become life-long friends, particularly David Chandler, Mike Klein, Roy Pollock and Eduardo Waisman.
Upon returning to France, JPH turned his interest to high density (or strongly coupled) plasmas, with astrophysical applications. In 1973 he was appointed Professor of Physics at Université de Paris 6 (now Pierre et Marie Curie), where he joined the small Laboratoire de Physique Théorique des Liquides headed by Savo Bratos. They started the post-graduate course on liquids, which is now very popular with students from all over Paris. JPH ran a small but lively research group on liquids, attracting excellent students (the first two to obtain their PhD were Patrick Vieillefosse and Bernard Bernu) and eminent visitors (Mike Klein, Ian McDonald, Yasha Rosenfeld and Lennard Sjögren in the early days). He joined forces with Ian McDonald to produce two editions of Theory of Simple Liquids. JPH later spent a very successful sabbatical year 1980-81 with Philippe Nozière's theory group at the European neutron scattering facility ILL in Grenoble, where he met Herbert Capellman, Duncan Haldane, Alan Griffin, and John Hayter, who stimulated JPH's interest in colloidal systems. Upon returning to Paris he became scientific adviser at the Limeil Centre of the Commissariat à l'Energie Atomique, where he supervised the PhD work of Gilles Zerah and others, and had a long-lasting collaboration with Jean Clérouin, in a joint project with Philippe Choquard's group in Lausanne.
In the early 80s, JPH had his arm sufficiently twisted by Philippe Nozières and others to agree to move to Lyon and help create the new Ecole Normale Supérieure. In the French context, creating a major Grande Ecole outside Paris was considered a risky business, and volunteers from the `establishment' were in short supply. JPH moved to Lyon in 1987 with a handful of daring young scientists (Claude Laroche and JPH being the only senior members), including Jean-Louis Barrat and Stephan Fauve, to create the Laboratoire de Physique de l'Ecole Normale Supérieure de Lyon, now one of the most thriving Physics Departments in France. With Bernard Bigot, JPH also served for five years as Deputy to the first Director of the Ecole, Guy Aubert. The success of the Ecole has gone beyond the wildest expectations, and now regularly diverts some of the best science students in France from rival Schools in Paris. In a `conspiracy' with Giovanni Ciccotti and others, JPH helped in transferring CECAM from Paris to Lyon.
JPH's group at ENS-Lyon thrived, and enjoyed collaborations with numerous visitors, including David Chandler, Mike Klein, Hartmut Löwen, Paul Madden, Jarek Piasecki and Hiroo Totsuji, in work on the glass transition, Brownian motion, dense plasmas and colloidal dispersions.
In 1990 the First Liquid Matter Conference took place at ENS-Lyon, attracting an unexpected 600 participants (and requiring the hasty installation of large tents for parallel sessions). The same year JPH was awarded the Grand Prix de l'Etat of the Académie des Sciences, and in 1992 he was elected to the Institut Universitaire de France. During spring of 1991 he spent several fruitful and sunny weeks with David Chandler's group in Berkeley, where he had been appointed Miller Visiting Professor. In 1994-95 he spent a productive and pleasant sabbatical year at Oxford with Mark Child, David Logan, Paul Madden and John Rowlinson, on a Visiting Fellowship at Balliol College. This visit stimulated his interest both in clay dispersions, and in the Oxbridge Collegiate system.
Having served ten eventful years in Lyon, JPH decided that it was time to move on. In 1996 he was elected to the 1968 Chair of Chemistry at Cambridge, previously held by John Lennard-Jones, Christopher Longuet-Higgins and David Buckingham. He moved to Cambridge in 1997 as Head of the Theoretical Chemistry Sector of the Department. His own group started off with his first Cambridge student, David Goulding, and first postdoc, Ard Louis; it has grown to a respectable (but reasonable) size, including distinguished Schlumberger Visiting Fellows, working on Statistical Mechanics of complex fluids and biomolecular assemblies. The Société Française de Physique awarded him in 1998 the Prix Spécial, in recognition of the scientific work he carried out in France over a period of 33 years. JPH is a Fellow of one of Cambridge's oldest Colleges, Corpus Christi, and serves as Deputy Head of the Department of Chemistry. JPH considers the life of a Physicist in a Chemistry Department to be stimulating and pleasant, and March 2002 saw the inauguration by the Vice Chancellor of the Cambridge University Centre for Computational Chemistry, created by JPH and his Theoretical Chemistry colleagues. On 9 May 2002, one day prior to his 60th birthday, JPH was elected Fellow of The Royal Society.
Outside of science, JPH enjoys visiting art exhibitions and Italian architectural marvels with his wife Martine, swimming and cycling with their grandson Gregory at their sea-side retreat in Port-Navalo (Southern Britanny), as well as listening to music by Mozart, Purcell and other great composers.
Occasionally he returns to his native Luxembourg (of which he has faithfully remained a citizen) to visit his brother and admire one of Europe's most remarkable and little-known medieval cities.