John Paul Hempel (October 14, 1935 – January 13, 2022[1]) was an American mathematician specialising in geometric topology, in particular the topology of 3-manifolds and associated algebraic problems, mainly in group theory.
[2] Hempel was born in Salt Lake City, Utah.
[4] In 2013, Hempel was elected a fellow of the American Mathematical Society.
[5] Hempel showed that the fundamental groups of 2-manifolds are residually finite.
[6] He also introduced the study of the curve complex into 3-manifold topology.