George L. O’Brien, professor emeritus in York University’s Department of Mathematics and Statistics in the Faculty of Science, passed away on Aug. 4. His death followed a long and courageous battle with early-onset Alzheimer’s, the illness that led him to retire early from York in 2008.
Born Sept. 19, 1944 in Northern Ireland, O’Brien was the son of a military doctor, so moved frequently as a child. His academic studies took him to Queen’s University, where he earned a BSc in 1966 and an MSc in 1968. In 1969 he earned an AM from Dartmouth College, and then PhD in 1971 under the supervision of John Lamperti. Following this he moved to York University, becoming full professor in 1982.
O’Brien’s research spanned a broad range of topics including probability theory, but with special attention paid to stochastic inequalities, and to stationary or self-similar stochastic processes. In the 1990s his attention turned to an approach to the theory of large deviations based on capacities and sup-measures, about which he wrote multiple papers, many co-authored with Wim Vervaat.
He served York University in multiple roles, notable among these were terms as departmental graduate program director, department chair, and as associate dean of the Faculty of Arts.
Outside York, he served on the Natural Sciences and Engineering Research Council of Canada (NSERC) grant selection committee for Statistics, the boards of directors of both the Canadian Mathematical Society and the Fields Institute, and as associate editor for the Canadian Journal of Statistics. He organized two major international meetings at York – the fourth and 21st Conference on Stochastic Processes and their Applications, held in 1974 and 1992 respectively. He was recognized by appointment as both a Fields Institute Fellow, and a Fellow of the Institute of Mathematical Statistics.
O’Brien will be remembered as a generous friend, a colleague of great integrity, and a valued mentor to his younger colleagues in probability. He was an avid runner, meeting regularly with friends to run in the ravines near York. But most of all, he enjoyed spending time with friends and family, especially at their cottage on the Muskoka river. He is survived by his wife Beth, his children Liam (Nina) and Katie, his sister Deirdre, and his brother Brian (Barbara). His daughter Meg and his sister Ruth predeceased him.