Abstract. Topological excitations are prominent candidates for explaining nonperturbative effects in QCD like confinement. In these lectures, I cover both formal treatments and applications of topological objects. The typical phenomena like BPS bounds, topology, the semiclassical approximation and chiral fermions are introduced by virtue of kinks. Then I proceed in higher dimensions with magnetic monopoles and instantons and special emphasis on calorons. Analytical aspects are discussed and an overview over models based on these objects as well as lattice results is given.
AppetiserWhen a lattice gauge configuration is subject to cooling, the result can be as depicted in Fig. 1. Without going into details here, this figure reveals typical aspects of a soliton stabilised by topology. In this lecture I will introduce definitions and properties of these beautiful objects and discuss their relevance for particle physics. Before I come to gauge objects like monopoles and instantons, I will demonstrate the main features by virtue of an example in a scalar theory.
The kinkAs the first model let us take one of the simplest quantum field theoretical systems, a real scalar field φ in a 1+1 dimensional Minkowski space with metric η µν = diag(+1, −1). The Lagrangian,shall contain a potential V (φ) that has several minima of same height, set to V = 0. For definiteness I will choose the famous mexican hat potential ,a