Analysis of Strong-Coupling Parameters for Superfluid 3He

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Superfluid ³He experiments show strong deviation from the weak-coupling limit of the Ginzburg-Landau theory, and this discrepancy grows with increasing pressure. Strong-coupling contributions to the quasiparticle interactions are known to account for this effect and they are manifest in the five β-coefficients of the fourth order Ginzburg-Landau free energy terms. The Ginzburg-Landau free energy also has a coefficient gz to include magnetic field coupling to the order parameter. From NMR susceptibility experiments, we find the deviation of gz from its weak-coupling value to be negligible at all pressures. New results for the pressure dependence of four different combinations of β-coefficients, β₃₄₅, β₁₂, β₂₄₅, and β₅ are calculated and comparison is made with theory.