Harmonic Approximations of difference operators

For a general class of difference operators <tex>H_\varepsilon = T_\varepsilon + V_\varepsilon</tex> on <tex>\ell^2(\varepsilon\mathbf{Z}^d)</tex>.
where <tex>V_\varepsilon</tex> is a multi-well potential and <tex>\varepsilon</tex> is a small parameter, we analyze the asymptotic behavior as<tex> \varepsilon\to 0</tex> of the (low-lying) eigenvalues and eigenfunctions.

We show that the first n eigenvalues of <tex>H_\varepsilon</tex> converge to the first n eigenvalues of the direct sum of harmonic oscillators on <tex>\mathbf{R}^d</tex> located at the several wells. Our proof is microlocal.