QUASI-STEADY STATE AND NEARLY INVARIANT SETS

We propose the notion of nearly invariant set for an ordinary differential equation to give a clear mathematical meaning to the notion of quasi-steady state (QSS) in equations describing chemically reacting systems. We show that this approach is sensible in view of the intended applications. Moreover, the approach leads to a heuristic for finding small parameters to satisfy a QSS assumption. The results are illustrated by several examples.