Karl Stein (1 January 1913 in

Hamm Hamm may refer to: Places ;Germany: * Hamm, North Rhine-Westphalia, a city north-east of Dortmund * Hamm (Sieg), a municipality in the eponymous ''Verbandsgemeinde'' in the district of Altenkirchen, Rhineland-Palatinate * Hamm, Bitburg-Prüm, part ...

Westphalia Westphalia (; ; ) is a region of northwestern Germany and one of the three historic parts of the state of North Rhine-Westphalia. It has an area of and 7.9 million inhabitants. The territory of the region is almost identical with the h ...

– 19 October 2000) was a

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

. He is well known for

complex analysis Complex analysis, traditionally known as the theory of functions of a complex variable, is the branch of mathematical analysis that investigates functions of complex numbers. It is helpful in many branches of mathematics, including algebraic ...

and

cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

Stein manifold In mathematics, in the theory of several complex variables and complex manifolds, a Stein manifold is a complex submanifold of the vector space of ''n'' complex dimensions. They were introduced by and named after . A Stein space is similar to a Stei ...

s and

Stein factorization In algebraic geometry, the Stein factorization, introduced by for the case of complex spaces, states that a proper morphism of schemes can be factorized as a composition of a finite mapping and a proper morphism with connected fibers. Roughly s ...

are named after him.

Career

Karl Stein received his

doctorate A doctorate (from Latin ''doctor'', meaning "teacher") or doctoral degree is a postgraduate academic degree awarded by universities and some other educational institutions, derived from the ancient formalism '' licentia docendi'' ("licence to teach ...

with his dissertation on the topic ''Zur Theorie der Funktionen mehrerer komplexer Veränderlichen; Die Regularitätshüllen niederdimensionaler Mannigfaltigkeiten'' at the

University of Münster The University of Münster (, until 2023 , WWU) is a public research university located in the city of Münster, North Rhine-Westphalia in Germany. With more than 43,000 students and over 120 fields of study in 15 departments, it is Germany's ...

under the supervision of

Heinrich Behnke Heinrich Adolph Louis Behnke (9 October 1898 in Horn – 10 October 1979 in Münster) was a German mathematician and rector at the University of Münster. Life and career He was born into a Lutheran family in Horn, a suburb of Hamburg. He att ...

in 1937. Karl Stein was conscripted into the

Wehrmacht The ''Wehrmacht'' (, ) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the German Army (1935–1945), ''Heer'' (army), the ''Kriegsmarine'' (navy) and the ''Luftwaffe'' (air force). The designation "''Wehrmac ...

sometime before 1942, and trained as a

cryptographer Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adversarial behavior. More gen ...

to work at OKW/Chi, the

Cipher Department of the High Command of the Wehrmacht The Cipher Department of the High Command of the Wehrmacht () (also ''Oberkommando der Wehrmacht Chiffrierabteilung'' or ''Chiffrierabteilung of the High Command of the Wehrmacht'' or ''Chiffrierabteilung of the OKW'' or ''OKW/Chi'' or ''Chi'') ...

. He was assigned to manage the OKW/Chi IV, Subsection a, which was a unit responsible for security of own processes, cipher devices testing, and invention of new cipher devices. He managed a staff of 11 In 1955, he became professor at the

Ludwig Maximilian University of Munich The Ludwig Maximilian University of Munich (simply University of Munich, LMU or LMU Munich; ) is a public university, public research university in Munich, Bavaria, Germany. Originally established as the University of Ingolstadt in 1472 by Duke ...

and emeritated in 1981. In 1990, he received the first Cantor medal.

Students

Stein's doctoral students included ,

Otto Forster Otto Forster (born 8 July 1937 in Munich) is a German mathematician. Education and career Forster received his ''Diplom'' in 1960 from Ludwig Maximilian University of Munich. There he received in 1961 his doctorate. His thesis ''Banachalgebren st ...

, Ivo Schneider,

Gunther Schmidt Gunther Schmidt (born 1939, Rüdersdorf) is a Germans, German mathematician who works also in informatics. Life Schmidt began studying Mathematics in 1957 at Göttingen University. His academic teachers were in particular Kurt Reidemeister, W ...

and Martin Schottenloher.

References

* * {{DEFAULTSORT:Stein, Karl 1913 births 2000 deaths People from Hamm 20th-century German mathematicians University of Münster alumni Academic staff of the Ludwig Maximilian University of Munich German cryptographers Presidents of the German Mathematical Society