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Stefan Banach (; 30 March 1892 – 31 August 1945) was a Polish mathematician who is generally considered one of the world's most important and influential 20th-century mathematicians. He was one of the founders of modern functional analysis, and an original member of the Lwów School of Mathematics. His major work was the 1932 book, ''Théorie des opérations linéaires'' (Theory of Linear Operations), the first monograph on the general theory of functional analysis. Born in Kraków, Banach attended Henryk Sienkiewicz Gymnasium, a secondary school, and worked on mathematics problems with his friend Witold Wiłkosz. After graduating in 1910, Banach and Wiłkosz moved to Lwów. However, during World War I Banach returned to Kraków, where he befriended Hugo Steinhaus. After Banach solved some mathematics problems which Steinhaus considered difficult, they published their first joint work. In 1919, with several other mathematicians, Banach formed a mathematical society. In 1920 he received an assistantship at the Jagiellonian University. He soon became a professor at the Lwów Polytechnic, and a member of the Polish Academy of Learning. He organized the "Lwów School of Mathematics". Around 1929 he began writing his ''Théorie des opérations linéaires''. After the outbreak of World War II, in September 1939, Lwów was taken over by the Soviet Union. Banach became a member of the Academy of Sciences of Ukraine and was dean of Lwów University's Department of Mathematics and Physics. In 1941, when the Germans took over Lwów, all institutions of higher education were closed to Poles. As a result, Banach was forced to earn a living as a feeder of lice at Rudolf Weigl's Institute for Study of Typhus and Virology. While the job carried the risk of infection with typhus, it protected him from being sent to slave labor in Germany and from other forms of repression. When the Soviets recaptured Lwów in 1944, Banach reestablished the University. However, because the Soviets were removing Poles from Soviet-annexed formerly-Polish territories, Banach prepared to return to Kraków. Before he could do so, he died in August 1945, having been diagnosed seven months earlier with lung cancer. Some of the notable mathematical concepts that bear Banach's name include Banach spaces, Banach algebras, the Banach–Tarski paradox, the Hahn–Banach theorem, the Banach–Steinhaus theorem, the Banach-Mazur game, the Banach–Alaoglu theorem, and the Banach fixed-point theorem. ==Life== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Stefan Banach」の詳細全文を読む スポンサード リンク
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