If all the eigenvalues of a real matrix
have real parts, then to an arbitrary negative definite
quadratic form
with
there corresponds a positive definite quadratic form
such that if one takes
then
and
satisfy
If all the eigenvalues of a real matrix
have real parts, then to an arbitrary negative definite
quadratic form
with
there corresponds a positive definite quadratic form
such that if one takes
then
and
satisfy
Weisstein, Eric W. "Lyapunov's Second Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/LyapunovsSecondTheorem.html