Jorge Sotomayor Tello

He passed away on 7 January 2022, at the age of 79.

He was a recipient of Brazil's National Order of Scientific Merit in mathematics. From 1994 until his death in early 2022, he was a member of the Brazilian Academy of Sciences. He also was a Fellow of John Simon Guggenheim Memorial Foundation (1983).

He is also author of the books Lines of Curvature and Umbilical Points on Surfaces, 18 CBM, Publicações Matemáticas, IMPA,(1991) with Carlos Gutierrez, reprinted and updated as Structurally Configurations of Lines of Curvature and Umbilic Points on Surfaces, Lima, Monografias del IMCA, (1998) and Differential Equations of Classical Differential Geometry, a Qualitative Theory, 27 CBM, Publicações Matemáticas,IMPA, (2009) with Ronaldo Garcia.

Introduced, with Carlos Gutierrez, the concept of ``principal configuration`` of curvature lines on surfaces. See Structurally Stable Configurations of Lines of Principal Curvature", Astérisque, França, v. 98–99, p. 195–215, (1982). The ideas leading to his work in this subject—traced back to the classical work of G. Monge, C. Dupin and G. Darboux—are discussed in his essay Monge's Ellipsoid. This research has been elaborared and extended in several directions by Sotomayor and his collaborators to include a large class of the differential equations of classical geometry (for example, the asymptotic lines, the axial curvature lines, the lines of mean curvature) and other classes of manifolds (for example, algebraic surfaces in 3 and 4 four dimensional Euclidean spaces).

In 1982 Sotomayor, together with C. Gutierrez put the concept of structurally stability in the study of the foliation determined by the lines of principal curvature of an ordinary surface in R.

Sotomayor is the author of the textbooks Lições de Equações Diferenciais Ordinárias, IMPA, Projeto Euclides, (1979), Singularidades de Aplicações Diferenciáveis, ELAM (1976) and Curvas Definidas por Equações Diferenciais no Plano, 13 Colóquio Brasileiro de Matemática, IMPA, (1981). He also translated essays of Henri Poincaré into Portuguese, which were published in a book under the title Um Poeta, um Matemático e um Físico: Três Ensaios Biográficos por Henri Poincaré, EDUSP,(2008).

Sotomayor visited the University of California at Berkeley during 1966–1968, where he witnessed the great developments in dynamical systems of that period which took place under the leardship of Stephen Smale.

Sotomayor earned his Ph.D. from the IMPA in 1964 under the supervision of Maurício Peixoto at the age of 22 years.

``It is a pleasure to say a few words in this occasion, commemorating the 60th birthday of Sotomayor. He was my student and got his PhD at IMPA in 1964. At the same time two other IMPA students of mine, Ivan Kupka and Aristides Barreto, also got their doctorates. These were the first doctorates awarded by IMPA. The theses of Sotomayor and Kupka got quick international recognition and were initial steps in the direction of establishing IMPA as a mathematical research institution, strong in Dynamical Systems. Both Sotomayor and Kupka came to IMPA from Peru, Sotomayor through the shortest geodesic and Kupka through an arc with origin in Strasbourg (France). In the wake of Sotomayor a number of Peruvians got their doctorates at IMPA. Among them, Carlos Gutierrez and Cesar Camacho became distinguished mathematicians and professors at IMPA. Currently Camacho is the Director of IMPA.

Jorge Manuel Sotomayor Tello (25 March 1942 – 7 January 2022) was a Peruvian-born Brazilian mathematician who worked on differential equations., bifurcation theory, differential equations of classical geometry.