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Anharmonic oscillator as a test of the coupled-cluster method
Phys. Rev. D 33, 3658 – Published 15 June, 1986
DOI: https://doi.org/10.1103/PhysRevD.33.3658
Abstract
Recent applications of the coupled-cluster method to the ( quantum field theory showed the necessity of a detailed analysis of its convergence behavior. The anharmonic oscillator has always served as a good test case for different approximation schemes. We treat the model both in the maximum-overlap condition and in the Hartree approximation. The ground-state energy is reproduced very well for all values of the coupling strength and already for a low-order truncation scheme. The expansion in correlation amplitudes can be carried out in extremely high order and shows a divergent tendency of the amplitudes. Introducing temperature dependence allows us to select the stable ground state out of a variety of solutions of the hierarchy of equations.
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