query: Who created differential equations?
passage: Differential equation
Differential equations first came into existence with the invention of calculus by Newton and Leibniz. In Chapter 2 of his 1671 work "Methodus fluxionum et Serierum Infinitarum",[1] Isaac Newton listed three kinds of differential equations:
passage: Causal perturbation theory
When developing quantum electrodynamics in the 1940s, Shin'ichiro Tomonaga, Julian Schwinger,
Richard Feynman, and Freeman Dyson discovered that, in perturbative calculations, problems with divergent
integrals abounded. The divergences appeared in calculations involving Feynman diagrams with closed loops of virtual particles. It is an important observation that in perturbative quantum field theory, time-ordered products of distributions arise in a natural way and may lead to ultraviolet divergences in the corresponding calculations.
From the mathematical point of view, the problem of divergences is rooted in the fact that the theory of
distributions is a purely linear theory, in the sense that the product of two distributions cannot consistently be defined (in general), as was proved by Laurent Schwartz in the 1950s.