The bifurcation diagram of an elliptic Kirchhoff-type equation with respect to the stiffness of the material

We study a superlinear and subcritical Kirchhoff-type equation which is variational and depends upon a real parameter $\lambda$. The nonlocal term forces some of the fiber maps associated with the energy functional to have two critical points. This suggests multiplicity of solutions, and indeed, we show the existence of a local minimum and a mountain pass-type solution. We characterize the first parameter ${\lambda }_0^{\ast }$ for which the local minimum has nonnegative energy when $\lambda \ge {\lambda }_0^{\ast }$. Moreover, we characterize the extremal parameter ${\lambda }^{\ast }$ for which if $\lambda >{\lambda }^{\ast }$; then, the only solution to the Kirchhoff equation is the zero function. In fact, ${\lambda }^{\ast }$ can be characterized in terms of the best constant of Sobolev embeddings. We also study the asymptotic behavior of the solutions when $\lambda \downarrow 0$.