**Leon Lichtenstein** was a Polish-born mathematician, who made contributions to the areas of differential equations, conformal mapping, potential theory, hydrodynamics and astronomy.

- Leon attended Mr Pankiewicz's High School in Warsaw, then attended the supplementary classes for science in the state-owned school in Jezuicka Street, graduating in 1894.
- In 1903, a year after Lichtenstein joined the company, it merged part of its activities with Schuckert and Co. of Nuremberg and became Siemens and Schuckert.
- Lichtenstein spent three years as an electrical engineer in the research laboratory of Siemens which made electrical motors, followed by a year as a theorist in the electric railway department.
- From the time he began working at Siemens, Lichtenstein began to study mathematics.
- Along with Constantin Carathéodory, Gerhard Hessenberg and Edmund Landau, Lichtenstein was an editor of Mathematische Abhandlungen Hermann Amandus Schwarz which was being published by Springer Verlag.
- Before this work was published (it appeared in 1914) Ferdinand Springer discussed with Lichtenstein about publishing work on the theory of boundary value problems.
- Lichtenstein replied suggesting publication of a complete survey of mathematics, split into twelve subject areas.
- It was not only Ferdinand Springer who had to undertake war work, for so did Lichtenstein.
- Lichtenstein's war work included testing power cables and doing aerodynamic calculations for the Air Force.
- However, by the summer of 1917, Lichtenstein's ideas for a new mathematical journal were taking shape and a contract was signed with Springer Verlag for the new journal Mathematische Zeitschrift with Lichtenstein as executive editor and the other editors being Konrad Knopp, Erhard Schmidt and Issai Schur.
- In 1919, after the war had ended, Lichtenstein became a full honorary professor at the Technische Hochschule in Berlin-Charlottenburg.
- Emil Lampe (1840-1918) had been the editor of the Jahrbuch since 1885 but he died in 1918 and, after Arthur Korn (1870-1945) stood in for a year as a temporary editor, in early 1919 Lichtenstein took over as editor.
- The war had made publication of the Jahrbuch a very hard task and Lichtenstein took over in the most difficult of circumstances.
- In 1920 David Hilbert named Felix Hausdorff, Ludwig Bieberbach and Leon Lichtenstein as suitable candidates for the 2nd and 3rd position in the appointments list in Kiel.
- Lichtenstein was not appointed but, in the same year, he was appointed as a full professor at the Westfälische Wilhelms-Universität in Münster.
- We should now look at Lichtenstein's mathematical contributions.
- The so-called "Schauder bounds" in the theory of elliptic differential equations can already be found quite precisely, for the two-dimensional case, in Lichtenstein's encyclopaedia articles.
- Lichtenstein's optimal theorem on the introduction of conformal parameters is well-known.
- includes many of Lichtenstein's original results, especially in the chapter "Existenzsätze" Ⓣ(Existence theorems).
- Lichtenstein's methods have therefore contributed significantly to the development of non-linear functional analysis.
- In 1929 Lichtenstein published Grundlagen der Hydromechanik Ⓣ(Fundamentals of hydromechanics).
- For many years following its publication insufficient knowledge led to these ideas not finding favour but recent work on topology and knot theory have shown that Lichtenstein laid the foundation for new developments in the qualitative study of fluid mechanics.
- Lichtenstein published the monograph Vorlesungen über einige Klassen nichtlinearer Integralgleichungen und Integrodifferentialgleichungen nebst Anwendungen Ⓣ(Lectures on some classes of nonlinear integral equations and integrals with applications) in 1931.
- In 1933 Lichtenstein published Gleichgewichtsfiguren rotierender Flüssigkeiten Ⓣ(Equilibrium figures of rotating liquids) in which he collected all the work that he had done on the theory of rotating fluids since 1918.
- Lichtenstein spent the rest of his career at Leipzig where he supervised several students who became leading mathematicians.
- In 1928 Lichtenstein had resigned from his role as editor-in-chief of the Jahrbuchs über die Fortschritte der Mathematik Ⓣ(Yearbook on the progress of mathematics).
- The events of 1933 were devastating for the Jewish Lichtenstein.

Born 16 May 1878, Warsaw, Russian Empire (now Poland). Died 21 August 1933, Zakopane, Poland.

View full biography at MacTutor

Origin Poland

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