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Ising model and auxiliary fields

Ising model and auxiliary fields

Ising model and auxiliary fields

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L<strong>and</strong>au Theory IIThe critical behavior is determined by G 2 (T,P)By definition we haveG 2 (T,P) = 0,if T = T cAgain, we exp<strong>and</strong> ...G 2 (T,P) = g 2 (P)(T − T c ) + h.o.t.,<strong>and</strong> put G 4 (T,P) ≈ G(T c ,P) = g 4 (P)L<strong>and</strong>au function with “magnetic field” HG(T,P,φ) = g 2 (P)(T − T c )φ 2 + g 4 (P)φ 4 + HφThe phase is determined by the minimum conditiondGdφ = 0

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