A New Principle to Determine the Variational Parameter for the Variational-Cumulant Expansion |
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| Authors: | WANG Qing CHEN Tianlun |
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| Affiliation: | 1. Department of Physics, Nankai University, Tianjin 300071, China;2. CCAST (World Laboratory), P. O. Box 8730, Beijing 100080, China |
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| Abstract: | The key point of the variational-cumulant expanhon is the determination of the variational parameter. In this paper, we present the improved mean-field hypothesis (IMFH) which is the bdse to determine the parameter. The new method derived from the IMFH shows advantage over previous methods. The critical temperature and some thermal dynamical functions for the Heisenberg model are calculated with the new method. |
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| Keywords: | VCE improved mean-field hypothesis Heisenberg model |
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