Temperature dependence of electric and magnetic gluon condensates

The contribution of Lorentz nonscalar operators to finite temperature correlation functions is discussed. Using the local duality approach for the one-pion matrix element of a product of two vector currents, the temperature dependence of the average gluonic stress tensor is estimated in the chiral limit to be ${〈{\mathrm{E}}^2+{\mathrm{B}}^2〉}_T=\left(\frac{{\pi }^2}{10}\right)b{T}^4$. At a normalization point $\mu =0.5\mathrm{}$ GeV we obtain $b\approx 1.1$. Together with the known temperature dependence of the Lorentz scalar gluon condensate we are able to infer ${〈{\mathrm{E}}^2〉}_T$ and ${〈{\mathrm{B}}^2〉}_T$ separately in the low-temperature hadronic phase.