 In his 1952 hidden-variables paper, Bohm arrived at his theory by writing the wave function in the polar form \(\psi = R\)exp\((iS/\hslash)\), where \(S\) and \(R\) are real, with \(R\) nonnegative, and rewriting Schrödinger’s equation in terms of these new variables to obtain a pair of coupled evolution equations: the continuity equation for \(\varrho = R^2\) and a modified Hamilton-Jacobi equation for \(S\). This differs from the usual classical Hamilton-Jacobi equation only by the appearance of an extra term, the quantum potential   \[ U = {-}\sum_k (\hslash^2 /2m_k) (\partial_{k}^2 R / R ), \]   alongside the classical potential energy term. 