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RESEARCH PRODUCT

The <FONT FACE=Symbol>d</font> Expansion and the Principle of Minimal Sensitivity

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The d-expansion is a nonperturbative approach for field theoretic models wich combines the techniques of perturbation theory and the variational principle. Different ways of implemeting the principle of minimal sensitivity to the d-expansion produce in general different results for observables. For illustration we use the Nambu- Jona-Lasinio model for chiral symmetry restoration at finite density and compare results with those obtained with the Hartree-Fock approximation.