Temperature dependence of instantons in QCD

We investigate the temperature dependence of the instanton content of gluon fields, using unquenched lattice QCD and the cooling method. The topological susceptibility arising from instantons decreases rapidly below the phase-transition temperature T-c (approximate to 150 MeV), becoming practically zero at T approximate toT(c). The dominant caloron size parameter deduced from the correlation function decreases from about 0.9 fm below T-c to 0.4 fm at 1.3T(c). The instanton charge distribution is Poissonian above T-c with deviations at low temperature.