Making a thermal analysis in the context of NLO SU(3) Chiral Perturbation Theory we see that isospin breaking (IB) corrections (both electromagnetic and QCD ones) to quark condensates are of order O(e~2) and O(ε), with e the π~o - η mixing angle. However the combination X_(uu) - X_(ud) of flavour breaking susceptibilities, which vanishes in the isospin limit and can be identified essentially with the connected susceptibility, has an order O(1) contribution enhanced with T because of the π~o - η mixing. Finally we present a thermal sum rule that relates quark condensate ratios and the light scalar susceptibility without IB, X (T) - X(0).
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