Spectral properties of integrable Schrodinger operators with singular potentials

The integrable Schrödinger operators often have a singularity on the real line, which creates problems for their spectral analysis. A classical example is the Lamé operator L = −d^2/dx^2 + m(m + 1)℘(x), where ℘(z) is the classical Weierstrass elliptic function. We study the spectral properties of its complex regularisations of the form L = −d^2/dx^2 + m(m + 1)ω^2 ℘(ωx + z_0 ), z_0 ∈ C, where ω is one of the half-periods of ℘(z). In several particular cases we show that all closed gaps lie on the infinite spectral arc. In the second part we develop a theory of complex exceptional orthogonal polynomials corresponding to integrable rational and trigonometric Schrödinger operators, which may have a singularity on the real line. In particular, we study the properties of the corresponding complex exceptional Hermite polynomials related to Darboux transformations of the harmonic oscillator, and exceptional Laurent orthogonal polynomials related to trigonometric monodromy-free operators

On the spectra of real and complex Lame operators

On the spectra of real and complex Lame operator