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giann_tee
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I am not sure if I am reading well the following article about KT phase transition in spin systems.
http://www.itp.uzh.ch/~llucas/projects/proseminar.pdf
Page 5 quotes a theory regarding the Helmholtz free energy function. The curve surrounding a spin site or an atom looks like everyone's best guess on the shape of potential energy.
Are they saying that Ising spin model with 2 possible spin states or Potts model with several states would have greater free energy?
http://www.itp.uzh.ch/~llucas/projects/proseminar.pdf
Page 5 quotes a theory regarding the Helmholtz free energy function. The curve surrounding a spin site or an atom looks like everyone's best guess on the shape of potential energy.
The Free Energy in the xy-Model
Considering Ginzburg-Landau theory, we find that, in the ordered phase of the xy-model, the free energy F has the shape of the bottom of a champagne bottle (Fig. 1). Its minimum is achieved on a circle on the base of the bottle. Points on this circle are depicted by the angle θ and the radius specified by the magnitude of the order parameter. Rotations around the circle correspond to spatially uniform changes in θ, and thus do not alter the free energy. However, spatially nonuniform changes in θ increase the free energy.
Are they saying that Ising spin model with 2 possible spin states or Potts model with several states would have greater free energy?
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