We derive the effective coarse-grained field equation forthe scalar condensate of the linear sigma model in a simple andstraightforward manner using linear response theory. The dissipativecoefficient is calculated at tree level on the basis of the physicalprocesses of sigma-meson decay and of thermal sigma-mesons and pionsknocking sigma-mesons out of the condensate. The field equation is solvedfor hot matter undergoing either one or three dimensional expansion andcooling in the aftermath of a high energy nuclear collision. The resultsshow that the time constant for returning the scalar condensate tothermal equilibrium is of order 2 fm/c. Comment: 19 pages, 3 figures areembedded at the end. The effect of the time dependence of the condensatev is included in this revised version. Numerical work is redoneaccordingly
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