Activities in 1997-1998

From the Report for Academic Year 1997-1998
of the Institute for Advanced Study

PIET HUT continued his work on large-scale computer simulations, using the GRAPE-4, a special-purpose computer developed by a group of astrophysicists at Tokyo University, headed by Jun Makino. His research centered on algorithmic developments aimed at refining the treatment of simultaneous local interactions in dense stellar systems, as well as including a host of non-gravitational effects. As an example of the latter, perturbations of the stellar evolution of double stars, due to interactions with other single and double stars, were modeled with increasing accuracy, in a collaborative project with Simon Portegies Zwart, from Tokyo, and Steve McMillan, from Drexel. Applying these methods to globular star clusters, Hut and coworkers have uncovered interesting and largely unexpected differences between simulations based on N-body methods and on Fokker-Planck methods.

Picking up again an old interest of his, tidal evolution in binary star systems, Hut engaged in a collaboration with Peter Eggleton and Ludmila Kiseleva, from Cambridge, UK. They made a considerable improvement upon the standard tidal bulge lag model, by deriving from first principles equations governing the quadrupole tensor of a star distorted by both rotation and the presence of a companion in a possibly eccentric orbit, together with equations governing the rates of change of the magnitude and direction of the stellar rotation, and the orbital period and eccentricity, based on the concept of the Laplace-Runge-Lenz vector.

Professor Hut was co-organizer of a Symposium on `Supercomputing: New Horizons in Computational Science', held in Tokyo in September 1997. He also organized a workshop on `Recent Developments in N-Body Simulations', held at Amsterdam University in January 1998, together with colleagues from the Astronomy and Computer Science Departments there, in order to explore and compare possibilities for constructing special-purpose hardware for simulations in a variety of fields, from astrophysics to quantum chemistry, molecular dynamics and plasma physics.

During a visit at the Santa Fe Institute, Hut continued his work in the general area of the study of limits to scientific knowledge through a collaboration with theoretical biologists Brian Goodwin and Stuart Kauffman. He presented the results in a session on `Modeling Modeling' that he chaired at the Conference on Complex Systems, organized by the New England Complex Systems Institute at Nashua, NH, in September 1997.

Professor Hut continued his interdisciplinary collaborations with cognitive psychologist Roger Shepard, from Stanford, philosopher of science Bas van Fraassen, from Princeton University, physicist Arthur Zajonc, from Amherst College, and writer Steven Tainer, from Berkeley. In December 1997, they established the Kira Institute (web site: <;), to study the relation between science and human values. Their first activities resulted in a series of bimonthly workshops, sponsored by the Fetzer Institute, which were held throughout the academic year, in Berkeley, Concord, Kalamazoo, and Princeton.