Instantons on $S^4$ and $\cpbar $, rank stabilization, and Bott periodicity

Abstract

We study the large rank limit of the moduli spaces of framed bundles on the projective plane and the blown-up projective plane. These moduli spaces are identified with various instanton moduli spaces on the 4-sphere and $\cpbar $, the projective plane with the reverse orientation. We show that in the direct limit topology, these moduli spaces are homotopic to classifying spaces. For example, the moduli space of $Sp(\infty )$ or $SO(\infty )$ instantons on $\cpbar $ has the homotopy type of $BU(k)$ where $k$ is the charge of the instantons. We use our results along with Taubes' result concerning the $k\to \infty$ limit to obtain a novel proof of the homotopy equivalences in the eight-fold Bott periodicity spectrum. We give explicit constructions for these moduli spaces.

20 pages, keywords: instantons, holomorphic bundles, Bott periodicity LaTeX2e