- time independent perturbation theory (TIPT)
- degenerate perturbation theory (DPT)
- WKB and variational approximation
- time dependent perturbation theory (TDPT)

Perturbation theory is used for problems which are too difficult. . Assume H is dividable into a solvable part: with and

Example: Helium The last term is , the other terms are just the solution for the hydrogen twice in a tensor product. Solution of , . Then .

In matrix language: so . Unfortunately, this is not easily solvable.

Method: start with one and see how it changes as is turned on. for very small.

Theory developed in perturbation expansion.

source

psfile jl@crush.caltech.edu index

time_independent_perturbation_theory

linearly_perturbed_QHO

fine_structure

formulas

DPT