High-Frequency Instabilities of the Ostrovsky Equation

We study the spectral stability of small-amplitude periodic traveling waves of the Ostrovsky equation. We prove that these waves exhibit spectral instabilities arising from a collision of pair of non-zero eigenvalues on the imaginary axis when subjected to square-integrable perturbations on the whole real line. We also list all such collisions between pairs of eigenvalues on the imaginary axis and do a Krein signature analysis.