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| ==Problem 1: Three Ising spins ==
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| Assume three spins <math> s_1, s_2, s_3 </math> are arranged in an equilateral triangle with each spin interacting with its two neighbors. The energy expression for the Ising model in an external magnetic field <math> H </math> is give by:
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| <math> H=-J(s_1s_2 + s_2 s_3 + s_3 s_1) - F (s_1 + s_2 + s_3) </math>
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| (a) Find canonical partition function for this model.
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| (b) Find average spin <math> \langle s \rangle </math>.
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| (c) Find internal energy <math> E </math>.
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| ==Problem 2: Spin-spin correlation function in the Ising model ==
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| ==Problem 3: Mean-field theory of the Heisenberg model of ferromagnetism ==
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