Leonard Esau Baum (August 23, 1931 – August 14, 2017) was an American mathematician, known for the Baum–Welch algorithm and Baum–Sweet sequence. He graduated Phi Beta Kappa from Harvard University in 1953,[1] and earned a Ph.D. in mathematics from Harvard in 1958, with a dissertation titled Derivations in Commutative Semi-Simple Banach Algebras.[2]
He developed the Baum–Welch Algorithm with Lloyd Welch while working for the Communications Research Division of IDA.[3] It enabled the development of speech recognition and had applications in cryptanalysis and genetics. He coined the motto of the Communications Research Division: "Bad ideas is good, good ideas is terrific, no ideas is terrible."[4][5]
Later, in the late 1970s and early 1980s, Baum used mathematical models for currency trading, working with Monemetrics, a predecessor of hedge fund management company Renaissance Technologies.[6] He left the firm in 1984 amid steep losses.[5] In his later years, he would participate in Go tournaments and work on mathematical problems relating to prime numbers and the Riemann hypothesis.[4] He died at his home in Princeton, New Jersey, on August 14, 2017, at the age of 86.[4]