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  2. Perturbation theory - Wikipedia

    en.wikipedia.org/wiki/Perturbation_theory

    An approximate 'perturbation solution' is obtained by truncating the series, often keeping only the first two terms, the solution to the known problem and the 'first order' perturbation correction. Perturbation theory is used in a wide range of fields and reaches its most sophisticated and advanced forms in quantum field theory.

  3. Perturbation theory (quantum mechanics) - Wikipedia

    en.wikipedia.org/wiki/Perturbation_theory...

    6.1 Example of first-order perturbation theory – ground-state energy of the quartic oscillator 6.2 Example of first- and second-order perturbation theory – quantum pendulum 6.3 Potential energy as a perturbation

  4. Singular perturbation - Wikipedia

    en.wikipedia.org/wiki/Singular_perturbation

    Singular perturbation theory is a rich and ongoing area of exploration for mathematicians, physicists, and other researchers. The methods used to tackle problems in this field are many. The more basic of these include the method of matched asymptotic expansions and WKB approximation for spatial problems, and in time, the Poincaré–Lindstedt ...

  5. Poincaré–Lindstedt method - Wikipedia

    en.wikipedia.org/wiki/Poincaré–Lindstedt_method

    In perturbation theory, the Poincaré–Lindstedt method or Lindstedt–Poincaré method is a technique for uniformly approximating periodic solutions to ordinary differential equations, when regular perturbation approaches fail.

  6. Perturbation (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Perturbation_(astronomy)

    In astronomy, perturbation is the complex motion of a massive body subjected to forces other than the gravitational attraction of a single other massive body. [1] The other forces can include a third (fourth, fifth, etc.) body, resistance , as from an atmosphere , and the off-center attraction of an oblate or otherwise misshapen body.

  7. Fermi's golden rule - Wikipedia

    en.wikipedia.org/wiki/Fermi's_golden_rule

    In quantum physics, Fermi's golden rule is a formula that describes the transition rate (the probability of a transition per unit time) from one energy eigenstate of a quantum system to a group of energy eigenstates in a continuum, as a result of a weak perturbation.

  8. Eigenvalue perturbation - Wikipedia

    en.wikipedia.org/wiki/Eigenvalue_perturbation

    In mathematics, an eigenvalue perturbation problem is that of finding the eigenvectors and eigenvalues of a system = that is perturbed from one with known eigenvectors and eigenvalues =. This is useful for studying how sensitive the original system's eigenvectors and eigenvalues x 0 i , λ 0 i , i = 1 , … n {\displaystyle x_{0i},\lambda _{0i ...

  9. Degenerate energy levels - Wikipedia

    en.wikipedia.org/wiki/Degenerate_energy_levels

    Some examples of two-dimensional electron systems achieved experimentally include MOSFET, two-dimensional superlattices of Helium, Neon, Argon, Xenon etc. and surface of liquid Helium. The presence of degenerate energy levels is studied in the cases of Particle in a box and two-dimensional harmonic oscillator , which act as useful mathematical ...