Supplementary Movie 2 (br.mp4): Traveling Wave Evolution in the Beeler-Reuter (BR) Model

The vertical and horizontal scales for the traveling wave (bottom left) have been normalized. The current state is indicated by a blue marker on the dispersion curve.

The pink square denotes a saddle-node bifurcations and green dots denote Hopf bifurcations. As the parameter varies, the fast wave, which initially features a sharp initial upstroke followed by a brief repolarization and a prolonged plateau, shortens in duration and ultimately transitions into a narrow ``sodium spike' along the slow wave branch. Simultaneously, the spectrum panel visualizes the linear stability dynamics, showing the fast wave losing stability through a cascade of Hopf bifurcations, visible as multiple eigenvalues crossing into the right half-plane.