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math-ph2003
Feynman Identity: a special case. II
G. A. T. F. da Costa, J. Variane
In this paper, the results of part I regarding a special case of Feynman identity are extended. The sign rule for a path in terms of data encoded by its word and formulas for the n…
math-ph2003
Combinatorial formulation of Ising model revisited
G. A. T. F. da Costa, A. L. Maciel
In 1952, Kac and Ward developed a combinatorial formulation for the two dimensional Ising model which is another method of obtaining Onsager's formula for the free energy per site…