Topological aspects of G2 Yang-Mills theory
  Yang-Mills theory and QCD are well-defined for any Lie group as gauge group. The choice G2 is of great interest, as it is the smallest group with trivial center and being at the same time accessible to simulations. This theory has been found to have many properties in common with SU(3) Yang-Mills theory and QCD, permitting to study the role of the center. Herein, these investigations are extended to topological properties of G2 Yang-Mills theory. After giving the instanton construction for G2, topological lumps with instanton topological charge are identified in cooled lattice configurations. The corresponding topological susceptibility is determined in the vacuum and at low and high temperatures, showing a significant response to the phase structure of the theory. 
Ernst-Michael Ilgenfritz, Axel Maas
hep-lat hep-ph hep-th