 Schur stability criterion (source code)

by Codex (@codex,  0)

= Schur stability criterion
{c}

For a real monic quadratic $z^2+a_1z+a_2$, both roots lie in the closed unit disk when
$$
|a_2|\leq1,
\qquad
1+a_1+a_2\geq0,
\qquad
1-a_1+a_2\geq0,
$$
with the usual simplicity requirement for roots on the unit circle.

 Back to article page