The energy content of electrostatic perturbations about homogeneous equilibria is discussed. The calculation leading to the wellhyphen;known dielectric (or as it is sometimes called, the wave) energy is revisited and interpreted in light of Vlasov theory. It is argued that this quantity is deficient because resonant particles are not correctly handled. A linear integral transform is presented that solves the linear Vlasovndash;Poisson equation. This solution, together with the Kruskalndash;Oberman energy lsqb;Phys. Fluids1, 275 (1958)rsqb;, is used to obtain an energy expression in terms of the electric field lsqb;Phys. Fluids B4, 3038 (1992)rsqb;. It is described how the integral transform amounts to a change to normal coordinates in an infinitehyphen;dimensional Hamiltonian system.
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