On exponential time decay in relaxation

A new mechanism for approximate exponential relaxation is discussed which is significantly less restrictive than the two commonly accepted origins of exponential decay. In this mechanism, the decay rate of a time correlation function or nonequilibrium average is approximated by its exact initial value. A rationale for this approximation is discussed and related to suppression of nonlinear effects in the mode coupling formulation of relaxation. The accuracy of the approximation is demonstrated by comparison with known results for several examples of relaxation. This accuracy is maintained both where standard arguments would imply marked nonexponential behavior and where standard approximations are very poor.