Theo Willem Jan Marie Janssen (13 August 1936 – 29 September 2017), better known as Ted Janssen, was a Dutch physicist and Full Professor of Theoretical Physics at the Radboud University Nijmegen. Together with Pim de Wolff and Aloysio Janner, he was one of the founding fathers of N-dimensional superspace approach in crystal structure analysis for the description of quasi periodic crystals and modulated structures. For this work he received the Aminoff Prize of the Royal Swedish Academy of Sciences (together with de Wolff and Janner) in 1988 and the Ewald Prize of the International Union of Crystallography (with Janner) in 2014. These achievements were merit of his unique talent, combining a deep knowledge of physics with a rigorous mathematical approach. Their theoretical description of the structure and symmetry of incommensurate crystals using higher dimensional superspace groups also included the quasicrystals that were discovered in 1982 by Dan Schechtman, who received the Nobel Prize in Chemistry in 2011. The Swedish Academy of Sciences explicitly mentioned their work at this occasion.
Early life and education Ted Janssen was born on August 13, 1936, in Vught, near 's-Hertogenbosch in the Netherlands. Already as a young boy he was fascinated by the sciences. He built radios, set up a chemistry lab in the attic of his parental home, was an avid bird watcher and he built his own telescopes. He remembered high school as ‘not very inspiring’ and he passed all exams without much effort, but viewed it as a time that truly formed him. Instead of spending time on homework he studied the history and philosophy of science and was very interested in astronomy and astrophysics. During his high school years he also developed a deep appreciation of literature and music. Later he added the visual arts, ballet, and architecture to that list. The enjoyment of the arts was vital to Ted. He called it essential components of life. He started playing the piano, harpsichord and cello in his early twenties. Too late to become an accomplished musician, but it brought him great joy. In 1954 he started college in Utrecht, studying mathematics and physics with minors in chemistry and astronomy. He again showed his interest in a wide variety of topics by attending lectures in ethics, philosophy, music and sculpture. After his candidate degree he concentrated on theoretical physics, but always included a deep understanding of mathematics in his work. After studying theoretical physics in Utrecht University Ted graduated under Leon van Hove with his doctoral dissertation ‘the classical limit of quantum mechanical diagram expansions’ and he was offered the opportunity to present it at an international conference in Utrecht on ‘Many-body Problems’. No less than six Nobel laureates (Yang, Lee, Prigogine, Anderson, Cooper and Schrieffer) were in the audience for Ted’s first presentation, which led to his first publication as well: ’On the classical limit of the diagram expansion in quantum statistics’ by T.W.J.M. Janssen. All his later publications were published as T. Janssen or Ted Janssen. After his doctoral exam in 1960 Ted worked for several years with professors Theo Ruijgrok, Tini Veltman, and John Tjon in Utrecht. Earlier he developed a friendship with co-student and co-worker Geert Fast. Geert’s promotor van Hove moved from Utrecht to CERN in Geneva and Geert asked Ted to keep an eye on his little sister, Loes Fast, who was studying veterinary medicine in Utrecht. Ted quickly developed strong feelings for Loes and in 1965 they got married. In 1965, he became the first PhD student of Aloysio Janner at the Catholic University Nijmegen and started on the work that resulted in his PhD thesis, Crystallographic Groups in Space and Time, in 1968, thereby already providing the theoretical basis of what would become the superspace approach.
… excerpt ends here. Continue reading the full article.
