Semiclassical structure of Hamiltonians

Abstract
The structure of few-body Hamiltonian matrices is studied in the semiclassical regime. Given (A^1(q^,p^),A^2 (q^,p^)), a pair of operators, it can be shown that, under quite general conditions, A^2 takes the form of a banded matrix in the ordered eigenrepresentation of A^1. Moreover, the bandwidth depends only on ħ and certain generalized microcanonical averages. In particular, if H=H0+εV, this implies that the perturbed Hamiltonian is banded in the appropriately ordered unperturbed basis.