Small-ε behavior of the Non-Hermitian PT-Symmetric Hamiltonian H=p²+x²(ix)^ε

The energy eigenvalues of the class of non-Hermitian PT-symmetric Hamiltonians $H=p^2+x^2(ix)^\epsilon$ ($\epsilon\geq0$) are real, positive, and discrete. The behavior of these eigenvalues has been studied perturbatively for small $\epsilon$. However, until now no other features of $H$ have been examined perturbatively. In this paper the small-$\epsilon$ expansion of the C operator and the equivalent isospectral Dirac-Hermitian Hamiltonian $h$ are derived.