Vacuous matrix

Hi Guys,

I am reading a papaer, where it is stated that the matrix "A", is vacuous for stable systems. I've never heard the term vacuous in that sense before. Can somebody expalin what it means?

Thanks!

I can't say for certain what it means here, but normally, "vacuus" means "empty". But I don't know what an "empty" matrix would be! Perhaps of "0" order?