Generalized London free energy for high-$T_c$ vortex lattices
  We generalize the London free energy to include four-fold anisotropies which could arise from d-wave pairing or other sources in a tetragonal material. We use this simple model to study vortex lattice structure and discuss neutron scattering, STM, Bitter decoration and $\mu$SR experiments. 
Ian Affleck (UBC), Marcel Franz (Johns Hopkins) and M.H. Sharifzadeh   Amin (UBC)