**Franz Rellich** was an Austrian-German mathematician who made important contributions in mathematical physics, particular in quantum mechanics.

- Rellich entered the Gymnasium in Graz in 1916, studying there until 1924.
- Of course the Nazi party destroyed the remarkable mathematical school at Göttingen but, before we look at how Rellich was affected by this, we need to explain his connection with that outstanding mathematician van der Waerden.
- As well as being Courant's student, Rellich was also his assistant at Göttingen, and he habilitated there in 1933.
- Rellich was a staunch opponent of National Socialism and, as a consequence, he suffered considerable problems throughout the early part of his academic career.
- Rellich had only a low-level appointment and ...
- Furthermore, in mid-December, Rellich was ordered to report on January 7 for ten weeks to a field-sports camp near Berlin.
- This was, in fact, a mistake, since Rellich, as an Austrian citizen, was not subject to such forced training regimens.
- However, on December 27, the Curator had, after some hesitation, replaced Rellich with Werner Weber as acting director of the Mathematical Institute.
- Rellich himself would lose his position at Gottingen six months later, on June 18.
- During the years 1933-34 at Göttingen, Rellich has taught courses on Integral Equations and Spectral Theory (1933) and Partial Differential Equations (1934).
- After being dismissed from Göttingen, Rellich was appointed as a privatdozent at the University of Marburg in 1934.
- In that year Rellich was appointed to a full Professorship to fill Siegel's chair.
- As director of the Mathematical Institute Rellich was deeply interested in creating a wide, stable base for scientific development.
- Rellich made many important research contributions, particularly significant being his work on perturbation theory of linear operators on a Hilbert space.
- Like much of Rellich's work, this was an abstract piece of mathematics motivated by questions in physics.
- He is also known for Rellich's theorem on entire solutions of differential equations which he proved in 1940.
- They show the fruitful interplay, characteristic for Rellich, of abstract operator theory with penetrating investigations of significant particular examples.
- A course which Rellich delivered at Göttingen in the winter semester of 1952-53, Eigenwerttheorie partieller Differentialgleichungen Ⓣ(Eigenvalue theory of partial differential equations), formed a major part of the book Eigenwerttheorie gewöhnlicher Differentialgleichungen Ⓣ(Eigenvalue theory of ordinary differential equations) published in 1976.
- The additional material in the book is written by Konrad Jörgens, who studied for his doctorate in Göttingen advised by Rellich around the time he gave the course.
- While we are mentioning Rellich's students, we must record that Jürgen Moser was one of Rellich's students.

Born 14 September 1906, Tramin, South Tirol, Austro-Hungarian Empire (now Italy). Died 25 September 1955, Göttingen, Germany.

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Origin Italy

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive