Leonard E. Baum

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Leonard Esau Baum (August 23, 1931 – August 14, 2017) was an American mathematician, known for the Baum–Welch algorithm. 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 entitled Derivations in Commutative Semi-Simple Banach Algebras.[2] He developed the Baum-Welch Algorithm with Lloyd Welch while working for the Institute for Defense Analyses (IDA) in Princeton, New Jersey,[3] which enabled the development of speech recognition and had applications in cryptanalysis and genetics. He coined the motto of IDA: "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]


  1. ^ "PBK Chooses Sixteen from Class of '53", The Harvard Crimson, November 24, 1952.
  2. ^ Harvard Mathematics Dissertations Archived 2019-04-04 at the Wayback Machine, accessed 2013-01-13.
  3. ^ Rabiner, Lawrence R., First-Hand:The Hidden Markov Model, IEEE Global History Network, retrieved 2013-01-13.
  4. ^ a b c "In Memoriam: Leonard Baum « American Go E-Journal". Retrieved 2020-01-30.
  5. ^ a b Zuckerman, Gregory (2019-11-05). The Man Who Solved the Market: How Jim Simons Launched the Quant Revolution. Penguin. p. 25. ISBN 978-0-7352-1799-7.
  6. ^ Teitelbaum, Richard (2008-10-27), Simons at Renaissance Cracks Code, Doubling Assets, Bloomberg, archived from the original on 2007-12-02, retrieved 2009-06-02