Carl Ludwig Siegel

Carl Ludwig Siegel was born on December 31, 1896 in Berlin, Germany. His father, whose name remains unknown, was a postal worker. Nothing else is known about his family background or his early childhood.

Although we know nothing about his schooling, he must have had a thorough education, as we would later find that he could read the works of ancient mathematicians in their original language. He must have also been a good student, entering Humboldt University with astronomy, mathematics and physics in 1915.

In those days, professors at Humboldt University conducted the beginners’ classes themselves. This way, they could pick out the gifted students at the very beginning and direct their career accordingly.

Although Siegel entered the Humboldt University with the intention of studying astronomy, he was soon picked up by theoretical physicist Max Karl Ernst Ludwig Planck and mathematician Ferdinand Georg Frobenius. Very soon, under the influence of Frobenius, Siegel gave up astronomy, becoming more interested in number theory.

In 1917, as the First World War progressed, Siegel was conscripted in the army. An antimilitarist, he could not adjust to the army life. For some time, he was also committed to a psychiatric institute; but nothing could change him. Ultimately, he was discharged from the army.

In 1922, Carl Ludwig Siegel moved to Frankfurt am Main, beginning his career as a Professor of Mathematics at Johann Wolfgang Goethe-Universität. By then, many eminent mathematicians such as Ernst Hellinger, Otto Szász, Paul Epstein and Max Dehn were already employed at the same department, creating a vibrant atmosphere.

Soon after joining his new position Siegel formed a close relationship with his new colleagues, working together without the thought of personal ambition. They would meet every Thursday afternoon, from four o’clock to six o’clock, talking about various matters.

Very soon, Siegel, Hellinger, Epstein, and Dehn began to collaborate on various matters. The seminar on the history of mathematics, started in 1922, was one such event. It continued for thirteen years and in later years, Siegel often looked back at them as the happiest memories of his life.

The participants at the seminar were required to study the works of ancient mathematicians in their original language. Yet, the number of participant was never less than six and together they studied the works of Euclid, Archimedes, Fibonacci, Cardan, Stevin, Viète, Kepler, Desargues, Descartes, Fermat, Huygens, Barrow and Gregory.

Siegel was also a dedicated teacher. In the beginning, he had few students; in the advanced courses there were only two. One day both of them were delayed and reaching late in class, they found that Siegel had already started teaching, having filled up a whole section of the blackboard.

On 30 January 1933, Hitler came to power in Germany and on 7 April 1933 the Civil Service Law was promulgated, removing Jewish teachers from the universities. Although Siegel was not affected by it, his friend, Otto Szász, was dismissed from service and Siegel found that very much disturbing.

From January 1935 to June 1935, he spent six-month sabbatical leave at the Institute for Advanced Study at Princeton, USA. On his return he found that Epstein, Hellinger and Dehn had been dismissed from their post. Sometime in the same year, he corrected an error in the Smith-Minkowski formula.

In 1936, he went to Oslo, Norway to attend International Congress of Mathematics on the invitation of the International Mathematical Union. It was a great honor for him because being invited to speak at ICM is almost like being inducted into the hall fame.

In 1937, he was invited to join University of Göttingen. Accepting the position towards the end of the year, he moved to Göttingen in early 1938. Here too he found that life, both inside and outside the campus, was highly influenced by Nazi policies.

Disturbed by the political atmosphere Siegel led a somewhat retired life in Göttingen. However, it did not stop him from pursuing his academic interest. In 1939, he started working on what later came to be known as ‘Siegel Modular Form’. In the same year, he also introduced ‘Siegel upper half-space’.