Joel Hass at Berkeley in 1987

Joel Hass is an American mathematician and a professor of mathematics and at the University of California, Davis.[1] His work focuses on geometric and topological problems in dimension 3.


Hass received his Ph.D. from the University of California, Berkeley in 1981 under the supervision of Robion Kirby.[2] He joined the Davis faculty in 1988.[1]

In 2012 he became a fellow of the American Mathematical Society.[3] From 2010 to 2014 he served as the chair of the UC Davis mathematics department.[4]

Research contributions

Hass is known for proving the equal-volume special case of the double bubble conjecture,[5] for proving that the unknotting problem is in NP,[6] and for giving an exponential bound on the number of Reidemeister moves needed to reduce the unknot to a circle.[7]

Selected publications

Research papers

2004: Student Solutions Manual, Maurice D. Weir, Joel Hass, George B. Thomas, Frank R Giordano