= Perturbation problem beyond all orders
{wiki=Perturbation_problem_beyond_all_orders}
The perturbation problem beyond all orders typically refers to the study of perturbative expansions in quantum field theory and other areas of physics where interactions are treated as small corrections to a solvable system. The standard approach to perturbation theory involves expanding a physical quantity (such as an energy level or transition amplitude) in a series in terms of a small parameter (often associated with the coupling constant of the theory).
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