A typical result of the paper is the following. Let $H_\gamma=H_0 +\gamma V$ where $H_0$ is multiplication by $|x|^{2l}$ and $V$ is an integral operator with kernel $\cos<x,y\rang le$ in the space $L_2(R^d)$. If $l=d/2+ 2k$ for some $k= 0,1,...$, then the operator $H_\gamma$ has infinite number of negative eigenvalues for any coupling constant $\gamma\neq 0$. For other values of $l$, the negative spectrum of $H_\gamma$ is infinite for $|\gamma|>\sigma_l$ where $\sigma_l$ is some explicit… Expand

We show that total multiplicities of negative and positive spectra of a self-adjoint Hankel operator $H$ with kernel $h(t)$ and of an operator of multiplication by some real function $s(x)$ coincide.… Expand

We show that all Hankel operators H realized as integral operators with kernels h(t + s) in L2(R+) can be quasi-diagonalized as H = L*ΣL. Here L is the Laplace transform, Σ is the operator of… Expand