1. This differential equation is the classic equation of motion of a charged particle in vacuum.

2. The self-adjoint form of the classical equation of motion of the harmonic oscillator is used to derive a Hamiltonian-like equation and the Schrödinger equation in quantum mechanics.

3. A series of size‐consistent Approximations to the equation‐of‐motion coupled cluster method in the singles and doubles approximation (EOM‐CCSD) are developed by subjecting the similarity transformed Hamiltonian H ̄=exp (− T) H exp (T) to a perturbation expansion.