Revisiting Fortet's proof of existence of a solution to the Schr\"odinger system

Understand

Since a few years, the Schr\"odinger problem captures the attention of a growing community of mathematicians interested in optimal transport problems.

• The first result of existence of a solution to this problem dates back to 1940, when Fortet published an article on the subject.
• In these notes, Fortet's original proof of existence and uniqueness of a solution to the Schr\"odinger system is revisited.