Khovanov homology and gauge theory

In these notes, I will sketch a new approach to Khovanov homology of knots and links based on counting the solutions of certain elliptic partial differential equations in four and five dimensions.The equations are formulated on four and five-dimensional manifolds with boundary, with a rather subtle boundary condition that encodes the knots and links.The construction is formally analogous to Floer and Donaldson theory in three and four dimensions.It was discovered using quantum field theory arguments but can be described and understood purely in terms of classical gauge theory.