On the spectrum of almost periodic solution of second-order differential equations with piecewise constant argument Original Research Article

We study the spectrum containment of almost periodic solution to second order differential equations with piecewise constant argument. Some known (periodic, quasi-periodic) results would be expanded. As a corollary, it is shown that such equations with periodic perturbations possess a quasi-periodic solution and no periodic solution. This phenomena is due to the piecewise constant argument. The results are extended to nonlinear equations.