COMPARISON OF SOME VARIATIONAL STRATEGIES USED IN FIELD-THEORY

Recently two variational strategies have been applied to the standard and linear delta expansions for quantum field theories. These strategies, both of which improve the accuracy of the expansions, have the property that for N self-interacting fields at large N the lowest-order delta expansion improved by the variational strategy gives the exact large-N result. In this article, we study, in the context of supersymmetric quantum mechanics, the numerical accuracy of the improved delta expansions when calculated to large order in delta and compare them with the accuracy of the large-N expansion. We find that the usual delta expansion is the most accurate, followed by the linear delta expansion. The large-N expansion, analytically continued to N = 1, is the least accurate method of the three.