Lánczos, Cornelius (Kornél) (1893–1974), theoretical physicist, was born 2 February 1893 in Székesfehérvár, Hungary, eldest of five children of Carolus Löwy, lawyer, and Adél Hahn. During the early 1900s the family changed their name to Lánczos, a Hungarian form of the Jewish name Löwy. After attending the local Cistercian catholic gymnasium he entered the University of Budapest (1911–16), where he studied physics and mathematics. He spent four years as an assistant at the Polytechnical University of Budapest before carrying out his Ph.D. (1921) at the University of Szeged, also in Budapest. After the first anti-Semitic law was passed in Hungary (1920), he moved to the University of Freiburg, Germany (lecturer 1921–4), and then to the University of Frankfurt (lecturer 1924–31). There he published a paper (1926) on an interpretation of quantum mechanics on a continuum basis in terms of integral equations, the earliest continuum-theoretic formalism of quantum mechanics, which preceded a paper by Erwin Schrödinger (qv) on his partial differential equation by about four weeks.
On the personal invitation of Einstein, he collaborated with him on the theory of relativity at the University of Berlin (1928–9) and they corresponded until Einstein's death (1955). Around this time (1928) he married his first wife, Maria Rupp, a German. As the political situation in Germany deteriorated he was first offered a visiting professorship (1931) and then the chair of mathematical physics and of aeronautical engineering at Purdue University, Indiana, USA (1932), a position he retained until 1946 on a part-time basis. In 1939, after his wife's death from tuberculosis, he brought his son to the USA just before the outbreak of the second world war. Most of the rest of his family – his mother, brother, sister, and most of their families – died in Auschwitz in 1945. As part of the war effort he took a year's leave of absence to spend time (1943–4) at the USA National Bureau of Standards, working on the Mathematical Tables Project.
Up until the war most of his work was concerned with relativity theory and quantum theory. However, before he arrived in the USA he became interested in numerical analysis, and during his time there he turned to applied mathematics. By 1946 he was appointed senior research engineer with the Boeing Airplane Company in Seattle, lecturing at the same time at the University of Washington, Seattle (1947). In 1949 he moved again, this time to the National Bureau of Standards, Institute for Numerical Analysis, University of California (UCLA), where he remained for four years (1949–53). However, the charged political climate and the security investigations of the McCarthy era forced the resignation of the institute's director. On the invitation of Schrödinger, now director of the Dublin Institute of Advanced Studies, Lánczos came to DIAS as a visiting professor (1952–3). During that year he was accused of disloyalty in the USA for having given refuge to an unapproved exile. He returned to America to clear his name and took up a position with North American Aviation, Los Angeles, as a specialist in computing (1953–4). However, they did not offer him a permanent position and he gratefully accepted the post of senior professor in the school of theoretical physics at DIAS (1955).
After his first year he almost left Dublin and wrote to Albert Einstein of his difficulties in working with Schrödinger, whom he described as the most arrogant person he had ever met. Einstein persuaded him to stay, and he retained this position until his retirement (1968). He and his new wife, Ilse Hildebrande (m. 1955), lived at 54 Northumberland Road, Ballsbridge, and became part of Dublin society and cultural life. He entered what was said to be a very special period of his life and returned to work on his first love, the study of the theory of relativity. The old-world atmosphere of DIAS, with its stimulating tea-time discussions and weekly seminars, which Éamon de Valera (qv) sometimes attended, offered a conducive environment for research. During his years in Dublin he published several books: Applied analysis (1956), Linear differential operators (1961), Albert Einstein and the cosmic world order (1965), Discourse on Fourier series (1966), Numbers without end (1968), and Space through the ages (1970). Outside mathematics he wrote on a range of topics: ‘The inspired guess in the history of physics’, ‘Science and society’, ‘Science as a kind of art’, and ‘Rationalism and the physical world’ among others. He loved lecturing and one of his principles was to say ‘yes’ to any offered opportunity, with the result that he continued to travel widely, receiving invitations to give lectures from all over the world and spending considerable periods of time in the USA on visiting professorships. In all, he wrote 100 papers on a wide array of disciplines: relativity theory, quantum mechanics, classical mechanics, electromagnetism, scientific computations, and numerical analysis. Much of his work had a profound influence on twentieth-century science and continues to have relevance for physics and applied mathematical research.
During his life he received many honours: MRIA (1957) and the honorary degrees Sc.D., TCD (1962), D.Sc., NUI (1970), Dr.Nat.Phil., Johann Wolfgang Goethe University, Frankfurt (1972), and D.Sc., University of Lancaster (1972). He received the Chauvenet prize (1960) from the Mathematical Association of America for his theorem on the decomposition of an arbitrary matrix. He continued his researches after his retirement from DIAS in 1968. In the latter part of his life he renewed contact with Hungary and its scientists. However, on his second trip to Budapest he died 25 June 1974 of a heart attack, and was buried in the Jewish cemetery in Farkasret, not far from his birthplace. A major review of his life and work is found in Cornelius Lanczos: collected published papers with commentaries (1998). An attractive charcoal drawing of Lánczos by Chirnside (1973) hangs in the library of the RIA and was presented by the mathematics department of Manchester Institute of Science and Technology (1976).