The Sattinger iteration method for 1-Laplace type problems and its application to concave-convex nonlinearities

In this paper we extend the classical sub-supersolution Sattinger iteration method to $1$-Laplace type boundary value problems of the form \begin{equation*} \begin{cases} \displaystyle -Δ_1 u = F(x,u) & $\text{in}$;Ω,\ \newline u=0 & $\text{on}$;\partialΩ, \end{cases} \end{equation*} where $\mathrm{\Omega }$ is an open bounded domain of ${\mathbb{R}}^N$ ($N\ge 2$) with Lipschitz boundary and $F(x,s)$ is a Caratheódory function. This goal is achieved through a perturbation method that overcomes structural obstructions arising from the presence of the $1$-Laplacian and by proving a weak comparison principle for these problems. As a significant application of our main result we establish existence and non-existence theorems for the so-called ``concave-convex’’ problem involving the $1$-Laplacian as leading term.