Many problems in his books stress this property of perturbation theory.

On the more advanced side, mathematical perturbation theory is also sometimes used.

It is possible to treat the equation using perturbation theory.

Techniques from perturbation theory find ample application in such areas.

Under some circumstances, perturbation theory is an invalid approach to take.

In that case the degenerate perturbation theory must be applied.

The degeneracy must be removed first for higher order perturbation theory.

In practice, some kind of approximation (perturbation theory) is generally required.

Perturbation theory is closely related to methods used in numerical analysis.

The above gives the solution of the eigenvalue to first order in perturbation theory.

The four additional solutions can be found using the methods of singular perturbation theory.

This makes it possible to use perturbation theory to obtain results that would otherwise be extremely difficult to find.

In a similar way as for small perturbations, it is possible to develop a strong perturbation theory.

A short introduction to the perturbation theory of linear operators.

Perturbation theory also looks at deformations, in general of operators.

Elementary perturbation theory shows that it will return periodically to its point of origin.

In perturbation theory, forces are generated by the exchange of virtual particles.

This effect could not be seen in any finite order in perturbation theory.

This case is referred to as singular or degenerate perturbation theory.

He almost asked students to excuse him for the field theory, where only perturbation theory can be offered.

These conditions can only be satisfied perturbatively, but this has to hold at any order of perturbation theory.

This is the standard approach to perturbation theory of general relativity for cosmology.

Perturbation theory methods start with a simplified form of the original problem, which is simple enough to be solved exactly.

The higher-order corrections can be obtained by conventional perturbation theory.

Perturbation theory is the only known approach to manage the quantum field theory.