Critical group estimates for nonregular critical points of functionals associated with quasilinear elliptic equations

We consider a class of quasilinear elliptic equations whose principal part includes the p-area and the p-Laplace operators, when p lies in a suitable left neighborhood of 2. For the critical points of the associated functional, we provide estimates of the corresponding critical groups, under assumptions that do not guarantee any further regularity of the critical point