Laughlin’s wave functions, Coulomb gases and expansions of the discriminant

Laughlin's wave functions, Coulomb gases and expansions of the discriminant. In the context of the fractional quantum Hall effect, we investigate Laughlin's celebrated ansatz for the ground state wave function at fractional filling of the lowest Landau level. Interpreting its normalization in terms of a one component plasma, we find the effect of an additional quadrupolar field on the free energy, and derive estimates for the ther-modynamically equivalent spherical plasma. In a second part, we present various methods for expanding the wave function in terms of Slater determinants, and obtain sum rules for the coefficients. We also address the apparently simpler question of counting the number of such Slater states using the theory of integral polytopes. 06/93 * Laboratoire de la Direction des Sciences de laMatì ere du Commissariatà l'Energie Atomique.