Non-perturbative Isospectrality for Quasi-periodic Gasymov-Type Potentials
摘要
For quasi-periodic Schrödinger operators with small Gasymov-type potentials and arbitrary irrational frequencies, we establish a complete spectral characterization: the spectrum coincides with that of the discrete free Laplacian. Our result is non-perturbative in the sense that the smallness condition is independent of the frequency. Furthermore, we prove the absence of both residual and point spectra, thereby establishing purely continuous spectrum. The proof combines Avila’s global theory, non-perturbative almost reducibility, and Green’s function estimates.