Charles Herbert Clemens Jr. (born 15 August 1939)[1] is an American mathematician specializing in complex algebraic geometry.
[2] Clemens received his bachelor's degree from College of the Holy Cross in 1961 and in 1966 his Ph.D. from the University of California, Berkeley, under Phillip Griffiths with thesis Picard–Lefschetz Theorem for Families of Algebraic Varieties Acquiring Certain Singularities.
[5] He was an invited speaker at the International Congress of Mathematicians in 1976 at Vancouver and in 1986 at Berkeley and gave a talk Curves on higher dimensional complex projective manifolds.
In 1972 Clemens and Griffiths proved that a cubic three-fold is in general not a rational variety, providing an example for three dimensions that unirationality does not imply rationality.
In 1986 Clemens was an editor of the Pacific Journal of Mathematics.