Mike Yates (1939-2020)

*Obituary for Mike Yates* by Jeff Paris

Professor C.E.M. Yates, Mike to all who knew him, died on the 21st of December 2020 in Bangor, North Wales, at the age of 81. He achieved a first class honours degree in Mathematics at Manchester University, remaining there for a doctorate on the topic of Turing Degrees of Unsolvability. Formally his supervisor and general mentor was Robin Gandy, though in fact the direction of his studies was wholly initiated by John Shepherdson along with distant mentoring by Martin Davis. Robin did however put him in touch with Gerald Sacks with whom he worked closely for many years. After receiving his doctorate in 1963 he held a Fulbright Scholarship for a year at Cornell and then another at the Institute of Advanced Study at Princeton. He then returned to Manchester as a lecturer and in rapid steps rose to a full professorship in 1978. He remained at Manchester until 1989 during which time he was highly instrumental in building up the Logic Group to one of the best in the country.

Over the course of this period his research continued to focus very largely on Recursion Theory, in particular he wrote seminal papers on recursively enumerable degrees, initial segments of the degrees of unsolvability and the application of the priority method. He is probably best known for his Minimal Pairs Theorem (proved independently by Alistair Lachlan). He later (2001) made a further, highly significant as it was to turn out, contribution to this and the wider area by editing with Robin Gandy the final fourth volume of Turing's *Complete Works.*

After leaving Manchester he spent periods at Leeds Metropolitan University and Liverpool John Moores University where he developed a keen interest in Computer Assisted Learning. This led to his working at the multimedia company Amaze Ltd in Liverpool until 1999 and subsequently contributing to the Centre for the Popularisation of Mathematics being promoted by Ronald Brown at Bangor.

Outside of mathematics he was a distinguished rock climber, even as a student being a team member of several first climbs in the Lake District.

Mike will be remembered with affection by all who knew him: caring, generous and greatly supportive of his students and colleagues and the discipline.