GAUSSIAN APPROXIMATION FOR ISING MODEL. VARIATIONAL APPROACH
Author(s): V.S.Yanishevsky (Ivan Franko Drogobych State Pedagogical University, 24 I.Franko Str., 293720 Drogobych, Lviv Region, Ukraine)
A variant of a Gaussian approximation in Ising model of phase transition is suggested. The method of functional integration with the application of a variational method is put in the basis of the approach. The Hamiltonian (the functional) is presented which in the method of functional integration produces the known results of a two-tails approximation obtained by a diagram method. The application of a variational method eliminates a principal demerit of the two-tails approximation -- incorrect description of the phase transition order. The results of numerical calculations for two and three-dimensional lattices are presented.
Comments: Figs. 2, Refs. 18, Tabs. 0.
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