Geometry deals with quantitative properties of space, such as distance and curvature on manifolds. Topology deals with more qualitative properties of space, namely those that remain unchanged under bending and stretching. (For this reason, topology is often called "the geometry of rubber sheets".) The two subjects are closely related and play a central role in many other fields such as Algebraic Geometry, Dynamical Systems, and Physics. At McMaster research focuses on Algebraic Topology (homotopy theory, K-theory, surgery), Geometric Topology (group actions on manifolds, gauge theory, knot theory), and Differential Geometry (curvature, Dirac operators, Einstein equations, and general relativity).