Jeffrey Lagarias
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Jeffrey Clark Lagarias (b. November, 1949 in Pittsburgh, Pennsylvania) is a mathematics professor at the University of Michigan.
He was a Putnam Fellow in 1970. He received his Ph.D. in Mathematics from Massachusetts Institute of Technology in 1974. In 1975 he joined AT&T Bell Laboratories and eventually became Distinguished Member of Technical Staff. Since 1995, he has been a Technology Consultant at AT&T Research Laboratories. In 2002 he moved to Michigan to work at the University and settle down with his family.
While his recent work has been in theoretical computer science, his original training was in analytic algebraic number theory. He has since worked in many areas, both pure and applied, and considers himself a mathematical generalist. Among other notable accomplishments, Lagarias discovered an elementary problem that is equivalent to the Riemann Hypothesis, namely whether for all n > 0, we have
with equality only when n = 1. Here Hn is the n-th harmonic number, the sum of the reciprocals of the first n positive integers, and σ(n) is the divisor function, the sum of the positive divisors of n. [1]. Lagarias has also done work on the Collatz Conjecture and Li's criterion.
