Correlation Functions in the Fully Frustrated 2D XY Model.

We present a detailed analysis of the critical properties of the two-dimensional XY model at full frustration. We calculate U(1) and Z 2 gauge-invariant correlation functions, as well as the chiral magnetization and susceptibility, by using extensive Monte Carlo simulations in lattices up to 240×240. These novel results are quantitatively different from those expected for separate 2D XY and 2D Ising models