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]

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]

Research papers

• Freedman, Michael; Hass, Joel; Scott, Peter (1983), "Least area incompressible surfaces in 3-manifolds" (PDF), Inventiones Mathematicae, 71 (3): 609–642, Bibcode:1983InMat..71..609F, doi:10.1007/BF02095997, hdl:2027.42/46610, MR 0695910, S2CID 42502819.
• Hass, Joel; Lagarias, Jeffrey C.; Pippenger, Nicholas (1999), "The computational complexity of knot and link problems", Journal of the ACM, 46 (2): 185–211, arXiv:math/9807016, doi:10.1145/301970.301971, S2CID 125854.
• Hass, Joel; Schlafly, Roger (2000), "Double bubbles minimize", Annals of Mathematics, Second Series, 151 (2): 459–515, arXiv:math/0003157, Bibcode:2000math......3157H, doi:10.2307/121042, JSTOR 121042, MR 1765704, S2CID 15663910.
• Hass, Joel; Lagarias, Jeffrey C. (2001), "The number of Reidemeister moves needed for unknotting", Journal of the American Mathematical Society, 14 (2): 399–428, arXiv:math/9807012, doi:10.1090/S0894-0347-01-00358-7, MR 1815217, S2CID 15654705.

Books

• Adams, Colin; Hass, Joel; Thompson, Abigail (1998), How to Ace Calculus: The Streetwise Guide, New York: W.H. Freeman and Company, ISBN 0-7167-3160-6.
• Adams, Colin; Hass, Joel; Thompson, Abigail (2001), How to Ace the Rest of Calculus: The Streetwise Guide, New York: W.H. Freeman and Company, ISBN 0-7167-4174-1.

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

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• Google scholar profile