Fritz John
Fritz John  

Born  Berlin, Germany 
14 June 1910
Died  10 February 1994 New York, USA 
(aged 83)
Nationality  United States 
Fields  Mathematics 
Institutions  University of Kentucky Ballistic Research Laboratory New York University 
Alma mater  University of Göttingen 
Doctoral students  Clifford Gardner Sergiu Klainerman 
Known for  John's equation John ellipsoid 
Notable awards  Birkhoff Prize (1973) Steele Prize (1982) 
Fritz John (14 June 1910 – 10 February 1994) was a Germanborn mathematician specialising in partial differential equations and illposed problems. His early work was on the Radon transform and he is remembered for John's equation.
Contents
Life and career
John was born in Berlin, Imperial Germany, the son of Hedwig (née Bürgel) and Hermann JacobsonJohn.^{1} He studied mathematics from 1929 to 1933 in Göttingen where he was influenced by Richard Courant among others. With Hitler's rise to power in 1933 "nonaryans" were being expelled from teaching posts, and John emigrated from Germany and immigrated to England.
John published his first paper in 1934 on Morse theory. He was awarded his doctorate in 1934 with a thesis entitled Determining a function from its integrals over certain manifolds from Göttingen. With Richard Courant's assistance he spent a year at St John's College, Cambridge. During this time he published papers on the Radon transform, a theme to which he would return.
John was appointed an assistant professor at the University of Kentucky in 1935 and he emigrated to the United States becoming naturalised in 1941. He stayed at Kentucky until 1946 apart from 1943 to 1945 during which he did war service for the Ballistic Research Laboratory at the Aberdeen Proving Ground, Maryland. In 1946 he moved to New York University where he remained.
Throughout the 1940s and 1950s he continued to work on the Radon transform in particular its application to linear partial differential equations, convex geometry, and the mathematical theory of water waves. He also wrote on numerical analysis and illposed problems. His textbook on partial differential equations was much influential and was reedited many times.
From the mid1950s he started working on the theory of equilibrium nonlinear elasticity. He retired in 1981 but continued to work on nonlinear waves.
Honors
He received many awards during his career including the Birkhoff Prize in Applied Mathematics in 1973 and the Steele Prize in 1982. On the 5th of May 1985, jointly with Olga Arsenievna Oleinik,^{2} he was awarded the laurea honoris causa in mathematics by the Sapienza University of Rome.^{3}
Publications
All John's published works, excluding monographs and textbooks, are collected in references (John 1985) and (John 1985a) with remarks and corrections by himself and commentaries by Sigurdur Helgason, Lars Hörmander, Sergiu Klainerman, Warner T. Koiter, HeinzOtto Kreiss, Harold W. Kuhn, Peter Lax, Louis Nirenberg and Fritz Ursell.
 John, Fritz (1955), Plane waves and spherical means applied to partial differential equations, Interscience Tracts in Pure and Applied Mathematics 2 (1st ed.), New York: Interscience Publishers, pp. VIII+172, MR 0075429, Zbl 0067.32101. John's famous monograph on the Radon transform and its application to partial differential equations.
 John, Fritz (1985), Moser, Jürgen, ed., Collected Papers. Volume 1, Contemporary Mathematicians (in English and German), Boston – Basel – Stuttgart: Birkhäuser Verlag, p. 648, ISBN 0817632662, MR 0809786, Zbl 0584.01025.
 John, Fritz (1985a), Moser, Jürgen, ed., Collected Papers. Volume 2, Contemporary Mathematicians (in English and German), Boston – Basel – Stuttgart: Birkhäuser Verlag, p. 758, ISBN 0817632670, MR 0809787, Zbl 0584.01025.
See also
References
 ^ According to its biography by O'Connor, John J.; Robertson, Edmund F., "Fritz John", MacTutor History of Mathematics archive, University of St Andrews..
 ^ See the relevant entry for further details and information.
 ^ The complete documentation is collected and commented in reference (VernacchiaGalli 1986).
Biographical references
 Klainerman, S. (1998). "On the work and legacy of Fritz John, 1934–1991. Dedicated to the memory of Fritz John". Communications on Pure and Applied Mathematics 51 (9–10): 991–1017.
 Moser, Jürgen (1995). "Fritz John, 1910–1994". Notices of the AMS 42 (1): 256–257.
 VernacchiaGalli, Jole (1986), "Fritz John", Regesto delle lauree honoris causa dal 1944 al 1985, Studi e Fonti per la storia dell'Università di Roma (in Italian) 10, Roma: Edizioni Dell'Ateneo, pp. 823–844. The "regest of honoris causa degrees from 1944 to 1985" (English translation of the title) is a detailed and carefully commented regest of all the documents of the official archive of the Sapienza University of Rome pertaining to the honoris causa degrees, awarded or not. It includes all the awarding proposals submitted during the considered period, detailed presentations of the work of the candidate, if available, and precise references to related articles published on Italian newspapers and magazines, if the laurea was awarded.
Further reading
 O'Connor, John J.; Robertson, Edmund F. (September 2001), "Fritz John", MacTutor History of Mathematics archive, University of St Andrews.
External links

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