= Universal specific-heat amplitude ratio
{title2=$A_+/A_-$}
When the singular <free-energy density> has $F_s=A_f|a_tt|^{2-\alpha}\Phi_\pm(0)$, the same thermal and free-energy metric factors multiply the singular <heat capacity> above and below the critical point. Their ratio cancels these factors and depends only on the normalized scaling functions of the <universality class>. This statement concerns singular amplitudes, not regular heat-capacity backgrounds, and needs separate treatment at logarithmic resonances or zero amplitudes. Branch matching constants belong to the fixed-point scaling functions and cannot be chosen as independent nonuniversal parameters.
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