A system may look stable when each component is considered alone, yet coupled directions can briefly amplify a disturbance.
KEY SOURCE · Conceptual transfer
Trefethen, L. N., Trefethen, A. E., Reddy, S. C. & Driscoll, T. A. (1993). Hydrodynamic stability without eigenvalues. Science, 261(5121), 578–584.
WHAT THIS SOURCE SUPPORTS
Non-normal linear systems can display large transient growth even when conventional eigenvalue analysis suggests asymptotic stability.
WHAT IT DOES NOT ESTABLISH
That the same equation is a human relapse mechanism, a clinical predictor or a validated risk score.