Excitable medium spiral waves — a simplified model of cardiac and neural dynamics
du/dt = Du∇²u + u − u³/3 − v + I | dv/dt = ε(u + a − bv)
Click to inject local stimulus. "Add Spiral" creates a rotating wave via broken wavefront technique.
This system models excitable tissue: a stimulus can trigger a self-propagating wave that leaves a refractory wake,
preventing back-propagation. Spirals in cardiac tissue cause arrhythmia (ventricular fibrillation).