Fluctuating topological defects in 2D liquids: heterogeneous motion and noise.

We measure the defect density as a function of time at different temperatures in simulations of a two-dimensional system of interacting particles. Just above the solid to liquid transition temperature, the power spectrum of the defect fluctuations shows a 1/f signature, which crosses over to a white noise signature at higher temperatures. When 1/f noise is present, the 5-7 defects predominantly form stringlike structures, and the particle trajectories show a 1D correlated motion that follows the defect strings. At higher temperatures this heterogeneous motion is lost.