Self-duality and long-wavelength behavior of the Landau-level   guiding-center structure function, and the shear modulus of fractional   quantum Hall fluids
  A remarkable self-duality of the "guiding-center" structure function s(q) of particles in a partially-filled 2D Landau level is used to express the long-wavelength collective excitation energy of fractional quantum Hall fluids in terms of a shear modulus. A bound on the small-q behavior of s(q) is given. 
F. D. M. Haldane
cond-mat.str-el