K. Loskot et al., FURTHER COMMENTS ON VECTOR NORMS AS LYAPUNOV FUNCTIONS FOR LINEAR-SYSTEMS, IEEE transactions on automatic control, 43(2), 1998, pp. 289-291
This paper deals with the conditions for a vector norm to be a Lyapuno
v function for a linear time-invariant system. An error in the proof o
f the related theorem given in [5] is pointed out, and a counterexampl
e proving that this theorem is generally false is provided. It is demo
nstrated that the considered problem is related to the one of extendin
g a linear operator without increasing its norm.