28 January 2025

Obituary of Kjeld Bagger Laursen

Obituary

Associate Professor Emeritus Kjeld Bagger Laursen died on 11 January 2025, aged 83. His research in Banach algebra and operator theory and his contribution to science didactics are described here by Niels Grønbæk.

Kjeld Bagger Laursen
Associate Professor Emeritus Kjeld Bagger Laursen, 8 January 1942 - 11 January 2025

Kjeld was my master's thesis supervisor. From our first meeting in 1975, I had a close relationship with him, first as a professional mentor and later as a friend and colleague. Typical of Kjeld, he did not see his role as a supervisor merely as related to the thesis. He included me in his professional network, mathematically and socially, and took a participatory approach to my life in general. He was a great support in my career and personal life.

Kjeld graduated from high school in 1960 and completed his bachelor's degree in mathematics and physics at Aarhus University in 1963. Instead of taking the beaten path to an MSc. he chose to continue his education in the US with a master's degree (1965) and PhD (1967) in mathematics from the University of Minnesota. In Minnesota, he also met his wife, Virginia. After his PhD, Kjeld returned to a postdoctoral position at Aarhus University. Here he met Bill Bade and Phil Curtis, visiting professors from UC, Berkeley and UCLA respectively. It was the start of a fruitful collaboration and lifelong friendships. After his postdoc at Aarhus University, Kjeld held an adjunct assistant professorship at UCLA (1970-72) before taking up his lectureship at the Department of Mathematics, University of Copenhagen. The collaboration with Bill Bade and Phil Curtis was further consolidated during a sabbatical year at UCLA 1976-77.

Kjeld's research area was Banach algebra and operator theory. His first work was on generalised group algebras, including a gold medal thesis at Aarhus University (1968). His focus changed when he met Bill Bade and Phil Curtis. Their work pioneered the field automatic continuity, which influenced  Banach algebra research for many years, manifested through the conference series Banach Algebra 1974, ..., ..., which is still running (though with a changed scope). Kjeld was involved from the start at UCLA and left his mark on the field in the following years as a researcher and conference organiser.

Along the way, he shifted his focus from Banach algebra to operator theory as reflected in his doctoral thesis Spectral Subspaces and Automatic Continuity (University of Copenhagen, 1991). Local spectral theory is the framework for understanding the so-called decomposable operators that play an important role in automatic continuity. Here too Kjeld made significant contributions, most notably in a series of journal publications with Michael Neumann (Mississippi State University) with whom he also published the monograph An introduction to local spectral theory (London Math. Soc. Monogr. (N.S.), 20, The Clarendon Press, Oxford University Press, New York, 2000), which is considered the authoritative introduction to the subject.

Kjeld Bagger LaursenWith the monograph, Kjeld concluded a significant influence on research mathematics. Throughout his professional life, Kjeld placed great emphasis on teaching and education. He devoted the latter part of his career to didactic aspects, at the Department of Mathematical Sciences as chairman of the study board (1996-2002), but especially at the faculty level as the driving force behind several initiatives to promote university pedagogy and science didactics in general. He was instrumental in the transfer of the Teaching and Learning in Higher Education programme from the Faculty of Humanities to the Faculty of Science and became the University of Copenhagen's representative on the board of the Danish Centre for Science Education (DCN, 1998 - 2001), a national cooperation network between universities to promote initiatives in science and mathematics education at university level. Through Kjeld, DCN instigated and supported a large number of projects at the Faculty of Science that also involved several teachers at the Department of Mathematical Sciences. These initiatives greatly contributed to a growing insight into didactic issues in the Faculty of Science's education programmes.

Kjeld's vision for the DCN initiative was to establish a permanent research and teaching unit in didactics at the Faculty of Science. The Centre for Science Didactics (CND, 2001 - 2006) was the first step in this effort and Kjeld became head of the centre with a 50% leave of absence from his lectureship at the Department of Mathematical Sciences, an impressive work effort that approached two full-time positions. Under Kjeld's leadership, CND built up an administrative and scientific staff, hired several consultants, developed teaching programmes and established contact with the faculty's various departments, including master thesis and PhD supervision. In 2006, CND was transformed into the Department of Science Education (IND), which today has considerable weight nationally and internationally. Kjeld continued his efforts for IND, including teaching and as editor of the IND-based journal MONA, which deals with science didactics at all educational levels.

Kjeld had lymphoma for many years, but as he said, he was going to die with it - not die from it. However, the years of treatment had weakened his immune system, so he did not survive a bout of Covid in the end. He died surrounded by his loved ones and is survived by his wife Virginia, son Michael, grandson Thomas and great-grandchildren Lucas and Olivia.

Niels Grønbæk, Professor Emeritus