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Kevin Reilly

Barry Cooper

Colleagues will be sorry to learn of the death, on 26 October 2015, of Professor Stuart Barry Cooper, Professor of Mathematical Logic, aged 72.  The following obituary has been contributed by Richard Elwes, Dugald MacPherson, Andrew Lewis and Stan Wainer.

Raised in Bognor Regis, Barry was educated at Chichester High School for Boys and then Oxford, from which he graduated in 1966. He studied for a PhD under Reuben Goodstein at Leicester, but worked mainly in Manchester with Mike Yates, the only established UK researcher in Barry's chosen field: the structure-theory of the Turing degrees, an exciting emerging field, then largely confined to North America. Barry was appointed to the University of Leeds as a Lecturer in 1969, and remained here throughout his career, excepting regular sabbaticals and invited visits abroad. The years 1971-73, which he spent at the University of California, Berkeley, were especially formative for his research career, and his left-wing politics found common ground with student activism and the civil rights movement. He became a Professor in 1996 at the University of Leeds. He was awarded an Honorary Degree from Sofia University in 2011.

Barry’s research focus, in Mathematical Logic, was always Computability, the study of the theoretical limits of the power of computers (or Turing machines). In the latter decades of the twentieth century, this blossomed into a mathematical discipline of astonishing beauty and profundity, a programme in which Barry played a prominent international role, publishing numerous important papers, a monograph ("Computability Theory", Chapman-Hall/CRC, 2003), and various edited collections. Enviably successful at securing research funding, he supervised many successful PhD students, several of whom are now well-established mathematicians. He was also founder and President of Computability in Europe, a flourishing association of now over a thousand members and a major annual conference. It was born in unpromising circumstances at a meeting to discuss a rejected European funding application.

Within computability, Barry was known for his deep and technically complex research, particularly with regard to the Turing and enumeration degree structures. He defined the jump classes, which have become a central object of study in the Turing degrees and all degree structures permitting a jump operation. His theorem, that every degree computably enumerable in and above ‘0’ is the jump of a minimal degree, is now regarded as one of the classics of the area. Over the years he did much to champion the study of the enumeration degrees, proving many of the fundamental theorems and defining the appropriate notion of jump for that structure. Always one with an eye for real world applications, in recent years Barry had been particularly concerned with the practical significance of the limits of computability, and their implications for our understanding of the scientific process.

Barry’s achievements extended well beyond mathematics. Having played rugby for England Under-16s, he became a keen long-distance runner, with a personal best marathon time of 2hrs 48mins. Another passion was jazz, and more generally, experimental music. He co-founded the Leeds Jazz non-profit organisation in 1984, and helped attract top artists, including Art Blakey and the Art Ensemble of Chicago.

A committed left-wing political activist, Barry was involved in various campaigns, notably the Chile Solidarity Campaign for refugees from 1973, and the Miners’ Strikes of 1984-85.

The year 2012 was the centenary of the birth of Alan Turing, an anniversary which might have passed largely unnoticed. As it was, the celebration’s global impact did much to bring Turing the public appreciation he deserves, culminating in his 2013 Royal pardon. This success was largely due to Barry, who invested his seemingly boundless energy in the Alan Turing Year of 2012 (which overflowed into the ongoing Alan Turing Years). He became the celebration’s spokesman on Twitter and in the media, including in the Guardians’ Northerner column. One outcome was Alan Turing: His Work and Impact, edited by Barry and Jan van Leeuwen, a hefty and definitive volume which won the Association of American Publishers’ prestigious R.R. Hawkins Award.

Barry’s intense research, teaching, and PhD supervision, as well as his role with the Turing Years, Computability in Europe, and on EU funding panels, continued to the end of his life. When he learned in October of his diagnosis, his response was to try to accelerate his efforts to set his PhD students on a good course, conclude major research projects, and complete several papers and books. He invited two colleagues to Leeds to work on one of the major open problems in the area. Sadly, they arrived too late to work with him, but will continue to tackle the question on which he had worked for many years.

Barry was popular with undergraduates as an outstanding and charismatic teacher. He was deeply concerned about his undergraduate and postgraduate students and their futures. He generated intellectual activity well beyond the obvious academic structures, for example running in recent years an informal reading group around themes in Logic and the Philosophy of Science. He was always quick to encourage and support junior colleagues, or junior members of the national and international research community.

Barry died peacefully after a short illness. He is survived by his wife Kate and their sons Evan and Mark, and by his daughters Carrie and Shirin with his former partner Sue Buckle.

The funeral service will be held at St Chad's Church, Otley Road, Leeds LS16 5JT at 11.45am on Thursday the 12th November, on which day the flag on the Parkinson Building will be flown at half-mast in Barry’s memory.