We propose an iterative method to find pointwise growth exponential growth rates in linear problems posed on essentially one-dimensional domains. Such pointwise growth rates capture pointwise stability and instability in extended systems and arise as spectral values of a family of matrices that depends analytically on a spectral parameter, obtained via a scattering-type problem. Different from methods in the literature that rely on computing determinants of this nonlinear matrix pencil, we propose and analyze an inverse power method that allows one to locate robustly the closest spectral value to a given reference point in the complex plane. The method finds branch points, eigenvalues, and resonance poles without a priori knowledge.2 Pointwise nonlinear eigenvalue problems from linearization at heteroclinic profiles
First-order ODEs from eigenvalue problemsWe consider eigenvalues problems that arise in the linearization at traveling waves, of the formwith matrix coefficients A(x; λ) ∈ C N ×N , continuous in x and analytic in λ. We focus on the simplest case of asymptotically constant coefficients lim x→±∞ A(x; λ) = A ± (λ).