Effective theory of fluctuating circulating currents in high-Tc cuprates
  We derive an effective dissipative quantum field theory for fluctuating orbital currents in clean $CuO_2$ sheets of high-$T_c$ cuprates, based on a three-band model. The Coulomb repulsion term between $Cu$- and $O$-sites is decoupled in terms of current operators representing horizontal and vertical parts of circulating currents within each $CuO_2$ unit cell of the lattice. The model has ordering of currents at finite temperatures. The dissipative kernel in the model is of the form $|\omega|/|{\bf q}|$, indicating Landau damping. Applications of the effective theory to other models are also discussed. 
Kjetil Borkje and Asle Sudbo