Instantons in two-dimensional noncommutative U(1) gauge theory on the lattice

Full text: Theories with noncommutative space-time coordinates represent alternative candidates of grand unified theories.We discuss U(1) gauge theory in 2 dimensions on a lattice with N sites. The mapping to a U(N) one-plaquette model in the sense of Eguchi and Kawai can be used for computer simulations. We are discussing the confinement mechanism and the formulation of topological objects.We performed quantum Monte Carlo simulations and calculated the topological charge for different matrix sizes and several values of the coupling constant. We constructed classical gauge field configurations with large topological charge and used them to initialize quantum simulations. It turned out that the value of the topological charge is decreasing during a Monte Carlo history. Our results show that the topological charge is in general supressed. The situation is similar to lattice QCD where quantum gauge field configurations are topologically trivial and one needs to apply some cooling procedure on the gauge fields to unhide the integer number of the instantons.We are trying simple cooling methods for the twisted Eguchi-Kawai model. (author)