OPERATOR PRODUCT EXPANSION AND ITS THERMAL AVERAGE

QCD sum rules at finite temperature, like the ones at zero temperature , require the coefficients of local operators, which arise in the shor t distance expansion of the thermal average of two-point functions of currents. We extend the configuration space method, applied earlier at zero temperature, to the case at finite temperature. We find that, up to dimension four, two new operators arise, in addition to the two app earing already in the vacuum correlation functions. It is argued that the new operators would contribute substantially to the sum rules, whe n the temperature is not too low..