 WKB approximation

For a large-parameter second-order ODE, WKB separates a rapidly varying exponential phase from a slowly varying transport amplitude.

The WKB approximation, short for the Wentzel-Kramers-Brillouin approximation, is a mathematical technique used primarily in quantum mechanics to find approximate solutions to the Schrödinger equation in the semiclassical limit, where quantum effects can be approximated by classical trajectories. The WKB method arises when studying quantum systems with a potential that varies slowly compared to the wavelength of the particle.