A maximum principle for the $p$-Laplacian, an eigenvalue estimate and a stabilization phenomenon for the large-$p$ regime

We establish an explicit maximum principle for the Dirichlet problem associated with the $p$-Laplacian ($p>1$), where the constant depends on both $p$ and the geometry of the domain. From this result we derive two main applications. First, we obtain a new lower bound for the first nontrivial eigenvalue of the $p$-Laplacian, which improves upon existing estimates in certain parameter regimes and for thin domains. Second, we prove an existence theorem for nonlinear boundary value problems of the form $$-\Delta_p u = \lambda f(u) \quad \text{in } \Omega, \qquad u=0 \quad \text{on } \partial \Omega,$$ with $f$ nonnegative, continuous and nondecreasing. A striking consequence is the emergence of a \emph{stabilization phenomenon}: for every such nonlinearity there exists a threshold $p_0 \colon = p_0(f,\lambda,\Omega)$ such that for all $p \geq p_0$ solutions exist. To our knowledge, this stabilization effect with respect to $p$, that apparently has not been observed before, suggests a connection to the $\infty$-Laplacian.