In this paper, by using the theory of integral bordism groups in PDE's, previously introduced by Prastaro, we give a new interpretation of the concept of (un)stability in the framework of the geometric theory of PDE's. A geometric criterium to identify stable PDE's and stable solutions of PDE's is given.
"(Un)stability and bordism groups in PDE's." Banach J. Math. Anal. 1 (1) 139 - 147, 2007. https://doi.org/10.15352/bjma/1240321564