Sean Declan McCartan  BSc, MSc, PhD (died 14 August 2023)

The death has taken place of Dr Sean Declan McCartan, a long-time member of academic staff of the Pure Mathematics Department in the School of Mathematics and Physics at Queen’s University Belfast (QUB).

Declan was born in Ballyshannon, Co. Donegal, to where his family had been evacuated during that phase of the War in which Belfast was subjected to the attentions of the Luftwaffe, but he was essentially a Belfast man by upbringing and through all manner of social and family connections. Graduating from QUB with a BSc in Mathematics, he stayed on for postgraduate study with the legendary Derek Burgess, and in 1964 was appointed as a Temporary Assistant Lecturer – and seldom can that designation have been less prophetic. He was promoted to Assistant Lecturer in 1965, to Lecturer in 1967 and to Senior Lecturer in 1978, a status which he retained until his retirement in 2005.

In early career he spent a year as an Assistant Professor in Northern Illinois at DeKalb. At the time the Vietnam War was raging, and any undergraduate who failed to proceed to the next year of study was at serious risk of being conscripted. From this period we get a revealing insight into Declan’s attitude towards teaching and, more generally, towards the fostering of young lives; at his own initiative, and in his own time, he established additional revision classes leading up to each assessment, aimed at saving the less well prepared students from the perils of failure. These sessions – which in all probability saved numerous lives – were so well appreciated by students that Declan’s wife Margaret eventually had to refuse to accept any more gifts of flowers and chocolates from them, arguing that neither space nor appetite could take the strain. 

This commitment to the educational side of university life and, in particular, to the support of the transition from School to Undergraduate Mathematics remained a consistent feature of Declan’s career throughout. He served as Examiner and Moderator on the GCE/GCSE exam boards for many years, was heavily involved in the development of Access, Mature Entrants, and other non-standard pathways into University Maths, organised ‘Drop-In’ clinics for students long before they were fashionable, and was a skilled practitioner of research-led teaching before it became University policy, through fruitful cross-fertilization between the work of the seven postgraduates whom he supervised (several of whom remained in contact with him ever after) and the higher-level modules on topology and order that he pioneered.

His research interests – published in the Proceedings of the American Mathematical Society, the Pacific Journal of Mathematics, the Journal of the London Mathematical Society and the Mathematical Proceedings of the Cambridge Philosophical Society amongst others – concentrated on connections between topological and order-theoretic structures, especially on extremal behaviour in the lattice of topologies and on applications to theoretical computer science. The administrative pinnacle of his career was undoubtedly his time as Head of Teaching of the Pure Mathematics Department.

Declan is survived by his wife Margaret, his sons Charles, Joseph and Martin, his daughters-in-law Liz, Sandra and Sinead, his six grandchildren, and the many generations of mathematical graduates (and, indeed, of young football players whom he coached in his ‘other burning passion’) whose careers he nurtured and advanced.