Professor Hofstra grew up in the Netherlands, where he studied piano from age 3. He did his graduate work at the University of Utrecht, getting a master’s degree in Philosophy and then a PhD in Mathematics. In 2003, Prof. Hofstra came to the University of Ottawa for a postdoctoral fellowship with the categorical logic group. From 2005-2007 he was a postdoctoral fellow in the Calgary Computer Science Department, and then returned to Ottawa in 2007 to take up a full-time position in the Department of Mathematics and Statistics.
Let us mention just a few of Prof. Hofstra’s major scientific works. His PhD thesis was in category theory and abstract recursion theory. He went on to publish a series of increasingly influential papers from his thesis on the foundations of so-called Realizability Toposes. In Calgary, he began a collaboration with Prof. Robin Cockett on a category-theoretic approach to computability and complexity theory called Turing Categories, which resulted in a series of important papers laying a new foundation for the subject.
Starting over 10 years ago, Prof. Hofstra, with Prof. Jonathan Funk (CCNY), introduced a new concept: isotropy groups of toposes. This work led to an extensive and influential literature, with contributions by many colleagues and graduate students. Another series of papers in the Funk-Hofstra collaboration examines the foundations of inverse semigroups, groupoids and pseudo-groups via Grothendieck topos theory. Prof. Hofstra was also interested in higher dimensional categories as well as the developments surrounding Voevodsky's Homotopy Type Theory; in the latter area, he wrote papers with two of the fundamental developers of the subject, Michael Warren and Steve Awodey.
A skilled poker player, for many years Prof. Hofstra taught an extremely popular first-year course called Poker 101, which attracted a large audience from all areas of the university. He illustrated the mathematical foundations of such games using vivid real-time presentations; this course led many students from other departments to major in mathematics. He was a lively and appealing lecturer, who the students adored. His exceptional teaching skills were rewarded with the 2013-14 University of Ottawa Excellence in Education prize.
Prof. Hofstra was remarkably gifted in many areas. Among his diverse interests, he maintained a love for serious mountaineering throughout his life. He had a photographic memory and could remember details of long discussions without taking notes. He continued music throughout his life, mostly jazz piano and guitar, earning extra money playing jazz in night clubs during his graduate studies.
More than all of these fine attributes, Prof. Pieter Hofstra was a dear friend who will be missed terribly.
Richard Blute and Philip Scott
Department of Mathematics and Statistics
