Roger David Nussbaum (born 29 January 1944, in Philadelphia)[1] is an American mathematician, specializing in nonlinear functional analysis and differential equations.
Nussbaum graduated in 1965 with a bachelor's degree from Harvard University.
He received his Ph.D. in 1969 from the University of Chicago with thesis The Fixed Point Index and Fixed Point Theorems for K-Set Contractions supervised by Felix Browder.
He retired there as professor emeritus.
[3] He was elected in 2012 a Fellow of the American Mathematical Society.