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Activities in 1990-1991

From the Report for Academic Year 1990-1991 of the Institute for Advanced Study PIET HUT has conducted research in stellar and cometary dynamics. In the first area, he has studied the effects of primordial binaries on the evolution of globular clusters. Working with Roger Romani and Steve McMillan, a number of observational consequences of the dynamical evolution were worked out for the recently discovered millisecond pulsars in these clusters. Another application was a study of the nucleus of the nearby galaxy M33, for which a dynamical model was constructed in analogy with globular cluster dynamics, in a collaboration with Lars Hernquist and John Kormendy. A more theoretical project in stellar dynamics focused on an analytical and semi-numerical investigation of the exponential growth of errors in N-body calculations, carried out with Jeremy Goodman and Douglas Heggie.

In the second area, that of cometary dynamics, Professor Hut constructed models for the formation of multiple impacts during the geological period of the Cretaceous-Tertiary boundary, some 66 million years ago. Stimulated by the recent identification of a huge crater in the Yucatan peninsula, with a diameter of 180 km diameter, for which the age was determined to be compatible with being 66 million years, Hut embarked on a collaboration with Walter Alvarez, Gene Shoemaker, and Sandro Montanari. Their conclusion was that the mass extinction at that time may have been triggered by multiple cometary impacts during the Northern hemisphere summer.

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