# Hans Duistermaat

J.J. (Hans) Duistermaat (1942-2010) studied mathematics at Utrecht University from 1959-65 and obtained his PhD degree there in 1968. After a postdoctoral year 1969-70 in Lund (Sweden), where he learned Fourier integral operators from Hörmander, he went in 1971-74 to Nijmegen, where he became full professor in 1972. In 1974 he returned to Utrecht on the chair of professor Freudenthal, where he stayed until his death in 2010.

He became member of the KNAW (Royal Dutch Academy of Arts and Sciences) in 1982, and Academy Professor in 2004.

He was the `promotor’ of 17 PhD students, 10 of which as the main thesis advior. Several of these were NWO projects, and one was research paid by Shell.

Duistermaat’s interests included classical mechanics, symplectic differential geometry, high-frequency asymptotics of solutions of linear partial differential equations, the differential geometric theory of arbitrarily nonlinear partial differential equations, and stochastically perturbed dynamical systems. Apart from 43 articles in refereed international journals, he wrote 7 books, of which probably the introduction to Fourier integral operators is the most well known. His best known research is probably his article with Guillemin on spectra of elliptic operators and periodic bicharacteristics, his article with Heckman on the Duistermaat-Heckman formula, and his article with Grünbaum on the bispectral problem.

His main editing task in 2010 was as coordinating editor of Indagationes Mathematicae, the mathematics journal of the KNAW.

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