Weinberg developed the "chiral" version of this method to apply it to nucleon-nucleon interactions in QCD, where it can be used to construct an effective Lagrangian.
One extension to this method defines a function Y in terms of two different values of t; that is the method of multiple scales. Weinberg developed the "chiral" version of this method to apply it to nucleon-nucleon interactions in QCD, where it can be used to construct an effective Lagrangian. This approach can be used to find the Rabi formula and the rate of spontaneous emission when applied to a forced two-level system. The interaction representation has to be used alongside this method to calculate the time-propagator when the system is time-dependent. When applying this method to a (*) degenerate state, a re-diagonalization of a certain operator in terms of degenerate states is required to solve the vanishing denominator problem; that method is used when this method is applied to the linear Stark effect. This method involves splitting the Hamiltonian into a "bare" Hamiltonian and another term, V, and then expanding in terms of a power series of some small parameter. For 10 points, name this method of approximating solutions to physical systems by considering the effects of a small namesake external force on the eigenvalues of the Hamiltonian.
One extension to this method defines a function Y in terms of two different values of t; that is the method of multiple scales.
perturbation theory