  We have numerically studied the dynamic correlation functions in
thermodynamic equilibrium of two-dimensional O(2)-symmetry models with either
bond (RSJ) or site (TDGL) dissipation as a function of temperature T. We find
that above the critical temperature the frequency dependent flux noise
$S_{\Phi}(\omega)\sim \vert 1+ {(\omega/\Omega)}^2\vert^{-\alpha (T)/2}$, with
$0.85\leq \alpha (TDGL)(T)\leq 0.95$ and $1.17 \leq \alpha (RSJ)(T) \leq 1.27$,
while the dynamic critical exponents $z(TDGL)\sim 2.0$ and $z(RSJ)\sim 0.9$.
Contrary to expectation the TDGL results are in closer agreement with the
experiments in Josephson-junction arrays by Shaw et al., than those from the
RSJ model. We find that these results are related to anomalous vortex diffusion
through vortex clusters.
