General Prerequisites:
B3.5 Topology and Groups (MT) and C3.1 Algebraic Topology (MT) are essential.
B3.2 Geometry of Surfaces (MT) and C3.3 Differentiable Manifolds (MT) are useful but not essential.
Course Term: Hilary
Course Lecture Information: 16 lectures
Course Overview:
Low-dimensional topology is the study of 3- and 4-manifolds and knots. The classification of manifolds in higher dimensions can be reduced to algebraic topology. These methods fail in dimensions 3 and 4. Dimension 3 is geometric in nature, and techniques from group theory have also been very successful. In dimension 4, gauge-theoretic techniques dominate.
This course provides an overview of the rich world of low-dimensional topology that draws on many areas of mathematics. We will explain why higher dimensions are in some sense easier to understand, and review some basic results in 3- and 4-manifold topology and knot theory.
Course Synopsis:
The definition of topological and smooth manifolds. Morse theory, handle decompositions, surgery. Every group can be the fundamental group of a manifold in dimension greater than three. The h-cobordism theorem, outline of proof and the Whitney trick. Application: The generalized Poincare conjecture.
Knots and links: Reidemeister moves, Seifert surface and genus, Alexander polynomial, fibred knots, Jones polynomial, prime decomposition, 4-ball genus
3-manifolds: Heegaard decompositions, unique prime decomposition, Dehn lemma, lens spaces, Dehn surgery, branched double cover
4-manifolds: Kirby calculus, the intersection form, Freedman’s and Donaldson’s theorems (without proof)