Solution

ID: past-exam-of-the-phase-transitions-and-collective-phenomena-course-of-the-university-of-cambridge/2012/paper-1/1/c/solution

At fixed zero field, . Therefore, away from on either branch,
Thus the singular heat capacity has exponent . An arbitrary analytic background must be added to obtain the full heat capacity. Vanishing branch amplitudes or the marginal case need care: a finite jump is compatible with this power counting, while a logarithmic singularity requires a logarithmic refinement of the assumed homogeneous form.

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