Seong-lae Cho해석적으로 풀 수 없는 문제의 해를 매우 작다고 여길 수 있는 매개변수들의 테일러 급수로 나타내는 이론
Perturbation theory
In mathematics and applied mathematics, perturbation theory comprises methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem.[1][2] A critical feature of the technique is a middle step that breaks the problem into "solvable" and "perturbative" parts.[3] In perturbation theory, the solution is expressed as a power series in a small parameter
ε
{\displaystyle \varepsilon }
.[1][2] The first term is the known solution to the solvable problem. Successive terms in the series at higher powers of
ε
{\displaystyle \varepsilon }
usually become smaller. An approximate 'perturbation solution' is obtained by truncating the series, usually by keeping only the first two terms, the solution to the known problem and the 'first order' perturbation correction.
https://en.wikipedia.org/wiki/Perturbation_theory
Perturbation theory (quantum mechanics)
In quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one. The idea is to start with a simple system for which a mathematical solution is known, and add an additional "perturbing" Hamiltonian representing a weak disturbance to the system. If the disturbance is not too large, the various physical quantities associated with the perturbed system (e.g. its energy levels and eigenstates) can be expressed as "corrections" to those of the simple system. These corrections, being small compared to the size of the quantities themselves, can be calculated using approximate methods such as asymptotic series. The complicated system can therefore be studied based on knowledge of the simpler one. In effect, it is describing a complicated unsolved system using a simple, solvable system.
https://en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics)