Alexander Gelfond

Not to be confused with Israel Gelfand.

Alexander Gelfond
Born	24 October 1906 Saint Petersburg, Russian Empire
Died	7 November 1968 (1968-11-08) (aged 62) Moscow, Soviet Union
Nationality	Soviet Union
Citizenship	Soviet Union
Alma mater	Moscow State University
Known for	Gelfond's theorem
Scientific career
Fields	Mathematics
Institutions	Moscow State University Steklov Mathematical Institute
Doctoral advisor	Alexander Khinchin Vyacheslav Stepanov
Doctoral students	Gregory Freiman

Alexander Osipovich Gelfond (Template:Lang-ru; 24 October 1906 – 7 November 1968) was a Soviet mathematician. Gelfond's theorem is named after him.

Biography

Alexander Gelfond was born in Saint Petersburg, Russian Empire in the family of a professional physician and amateur philosopher Osip Gelfond. He entered the Moscow State University in 1924, started his postgraduate studies there in 1927 and obtained his PhD in 1930. His advisors were Alexander Khinchin and Vyacheslav Stepanov.

In 1930 he stayed for five months in Germany (in Berlin and Göttingen) where he worked with Edmund Landau, Carl Ludwig Siegel and David Hilbert. In 1931 he started teaching as a Professor at the Moscow State University and worked there until the last day of his life. Since 1933 he also worked at the Steklov Institute of Mathematics.

In 1939 he was elected a Corresponding member of the Academy of Sciences of the Soviet Union for his works in the field of Cryptography. According to Vladimir Arnold, during World War II Gelfond was the Chief Cryptographer of the Soviet Navy.

Results

Gelfond obtained important results in several mathematical domains including number theory, analytic functions, integral equations and the history of mathematics, but his most famous result is his eponymous theorem:

If α and β are algebraic numbers (with α≠0 and α≠1), and if β is not a real rational number, then any value of α^β is a transcendental number.

This is the famous 7th Hilbert's problem. Gelfond proved a special case of the theorem in 1929, when he was a postgraduate student and fully proved it in 1934. The same theorem was independently proved by Theodor Schneider and so the theorem is often known as the Gelfond–Schneider theorem. In 1929 Gelfond proposed an extension of the theorem known as the Gelfond's conjecture that was proved by Alan Baker in 1966.

Before Gelfond's works only a few numbers such as e and π were known to be transcendental. After his works an infinite number of transcendentals could be easily obtained. Some of them are named in Gelfond's honor:

• $2^{\sqrt {2}}$ is known as the Gelfond–Schneider constant
• $e^{\pi }\,$ is known as Gelfond's constant.

References

• Gel'fond, A. O. (1960) [1952]. Transcendental and algebraic numbers. Dover Phoenix editions. New York: Dover Publications. ISBN 978-0-486-49526-2. MR 0057921.
• B.V. Levin; N.I. Feldman; A.B. Sidlovsky (January 2010). "Alexander O. Gelfond" (PDF). Acta Arithmetica. 17: 315–336. {{cite journal}}: Check date values in: |year= / |date= mismatch (help)
• O'Connor, John J.; Robertson, Edmund F., "Alexander Gelfond", MacTutor History of Mathematics Archive, University of St Andrews

External links

• Alexander Gelfond at the Mathematics Genealogy Project