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UNITEXT for physics

Variation Method

Tapan Kumar Das

Published Jan 1, 2026• 0 citations
Publisher
DOI
10.1007/978-981-95-4546-9_9

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We expand some approximate free energies in the cluster variation method for random Ising models with respect to exchange interactions, and compare them with the Plefka's expansion. It can be clarified that some approximate free energies in the cluster variation method include all terms relating to specific clusters (or diagrams) in Plefka's expansion. Revealing the relationship between Plefka's expansion and the cluster variation method allows us to understand how the cluster variation method treats correlations among nodes.