SU(N) gauge theories in the presence of a topological term

Abstract

We review recent results on the θ dependence of the ground-state energy and spectrum of four-dimensional SU(N) gauge theories, where θ is the coefficient of the CP-violating topological term F F in the Lagrangian. In particular, we discuss the results obtained by Monte Carlo simulations of the lattice formulation of QCD, which allow the investigation of θ dependence around θ 0 by determining the moments of the topological charge distribution, and their correlations with other observables. The results for N 3 and larger values of N support the scenario obtained by general large-N scaling arguments. [A longer write-up, along with a full list of references, can be found at [1]] © 2008 IOP Publishing Ltd.