The spectrum of a Harmonic Oscillator Operator Perturbed by Point Interactions

We consider the operator $ L = - (d/dx)^2 + x^2 y + w(x) y , y \in L^2($\mathbb{R}$) $,where$ w(x) = s [ \delta(x - b) - \delta(x + b)], b \neq 0,$real,$s \in $\mathbb{C}$$. This operator has a discrete spectrum: eventually the eigenvalues are simple and $\lambda_n = (2n + 1) + s^2 (\kappa(n) / n) + \rho(n)$,where$ \kappa(n) = \frac{1}{2\pi} [(-1)^{n + 1} \sin ( 2 b \sqrt{2n} ) - \frac{1}{2} \sin ( 4 b \sqrt{2n} ) ]$and$ |\rho(n) | \leq C (\log n) / (n^{3/2})$If$s = i \gamma$,$\gamma$real,thenumber$T(\gamma)$ of non-real eigenvalues is finite, and $T(\gamma) \leq [ C (1 + | \gamma |) \log (e + | \gamma |)]^2.$ The analogue of the above equations is given in the case of any two-point interaction perturbation $w(x) = c_+ \delta(x - b) + c_- \delta(x + b), c_+, c_- \in $\mathbb{C}$. $