2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/137789We propose a method for finding gaps in the spectrum of a differential operator. When applied to the one-dimensional Hamiltonian of the quartic oscillator, a simple algebraic algorithm is proposed that, step by step, separates with a remarkable precision all the energies even for a double-well configuration in a tunnelling regime. Our strategy may be refined and generalised to a large class of 1d-problems.Quantum PhysicsMathematical Physicstext