Mark Kac (pronounced "kahts",, b. 3 August 1914, Krzemieniec, then in the Russian Empire, now in Ukraine; d. 26 October1984, California, USA) was a Polish and American mathematician of Jewish ancestry. His main interest was probability theory. His question "can you hear the shape of a drum?" set off research into spectral theory, with the idea of understanding the extent to which the spectrum allows one to read back the geometry. Wikipedia
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