The stochastic terms 4 , 5 , and 6 in Eqs. ͑20a͒-͑20c͒ are still additive Gaussian noise processes. However, Eqs. ͑21a͒-͑21c͒ show how the transformation has acted on the original stochastic terms 1 , 2 , and 3 to create new noise processes, which have a variance different from that of the original noise processes. Also note that we have suppressed the argument of 4 , 5 , and 6 in Eqs. ͑20a͒-͑20c͒. The time scaling means that these noise terms should be evaluated at .