Alexander Oppenheim (1902 – 1995) was a British mathematician notable for his work in the theory of quadratic forms and for formulating the Oppenheim conjecture. He was born on 31 August 1902 in Manchester, England, and earned his undergraduate degree at the University of Manchester before completing a Ph.D. under the supervision of Louis J. Mordell at the University of Cambridge.
Oppenheim held academic positions at several institutions, including the University of Leeds, where he served as a lecturer and later as a professor of mathematics. He contributed to the development of number theory, particularly through research on indefinite quadratic forms. The conjecture bearing his name, proposed in 1929, concerns the values taken by indefinite rational quadratic forms at integer points and was proven in 1986 by Gregory Margulis using techniques from ergodic theory.
In addition to his research, Oppenheim was active in mathematical education and administration. He played a role in establishing and promoting mathematical societies in the United Kingdom and was involved in organizing conferences that fostered collaboration among mathematicians.
Alexander Oppenheim passed away on 29 September 1995. His contributions continue to be recognized in the fields of number theory and the history of mathematics.
