Analysis of Floquet formulation of time-dependent density-functional theory

Floquet formulation of time-dependent density-functional theory is revisited in light of its recent criticism [N.T. Maitra, K. Burke, Chem. Phys. Lett. 359 (2002) 237]. It is shown that Floquet theory is well founded and its criticism has overlooked important points of both the Runge–Gross formalism and Floquet formulation itself. We substantiate our analysis by examples similar to that considered by Maitra and Burke.