Search for "Perturbation theory" in article titles:

1. 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. A critical feature of the technique is a middle step that breaks ... (Physics) [100%] 2023-12-30 [Perturbation theory] [Concepts in physics]...
2. Perturbation theory: A group of methods for studying various problems employed in many branches of mathematics, mechanics, physics, and technology. In this article the principal ideas of perturbation theory are given from a general point of view. (Mathematics) [100%] 2023-10-24
3. 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 ... (Physics) [70%] 2022-10-27 [Perturbation theory] [Quantum mechanics]...
4. 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 ... (Quantum mechanics) [70%] 2023-12-29 [Perturbation theory] [Mathematical physics]...
5. Perturbation theory (dynamical systems): The principle of perturbation theory is to study dynamical systems that are small perturbations of `simple' systems. Here simple may refer to `linear' or `integrable' or `normal form truncation', etc. (Dynamical systems) [70%] 2021-12-24 [Bifurcations] [Celestial mechanics]...
6. Chiral perturbation theory: Chiral perturbation theory (ChPT) is an effective field theory constructed with a Lagrangian consistent with the (approximate) chiral symmetry of quantum chromodynamics (QCD), as well as the other symmetries of parity and charge conjugation. ChPT is a theory which allows ... (Effective field theory of quantum chromodynamics) [81%] 2023-12-30 [Quantum chromodynamics]
7. Causal perturbation theory: Causal perturbation theory is a mathematically rigorous approach to renormalization theory, which makes it possible to put the theoretical setup of perturbative quantum field theory on a sound mathematical basis. It goes back to a seminal work by Henri Epstein ... (Mathematically rigorous approach to renormalization theory) [81%] 2023-12-29 [Renormalization group]
8. Chiral perturbation theory: $ \newcommand{\qbar}{\bar{q}} \newcommand{\ubar}{\bar{u}} \newcommand{\dbar}{\bar{d}} \newcommand{\sbar}{\bar{s}} \newcommand{\lvac}{\langle 0|\,} \newcommand{\rvac}{\,|0\rangle} \newcommand{\be}{\begin{equation}} \newcommand{\ee}{\end{equation}} \newcommand{\bdm}{\begin{displaymath}} \newcommand{\edm}{\end{displaymath ... [81%] 2021-12-24
9. Singular perturbation theory: Singular perturbation theory concerns the study of problems featuring a parameter for which the solutions of the problem at a limiting value of the parameter are different in character from the limit of the solutions of the general problem; namely ... [81%] 2021-12-24 [Dynamical Systems] [Applied Mathematics]...
10. Causal perturbation theory: Causal perturbation theory is a mathematically rigorous approach to renormalization theory, which makes it possible to put the theoretical setup of perturbative quantum field theory on a sound mathematical basis. It goes back to a seminal work by Henri Epstein ... (Physics) [81%] 2023-12-29 [Renormalization group]
11. Cavity perturbation theory: In mathematics and electronics, Cavity perturbation theory describes methods for derivation of perturbation formulae for performance changes of a cavity resonator. These performance changes are assumed to be caused by either introduction of a small foreign object into the cavity ... [81%] 2023-12-31 [Electromagnetism] [Electrical engineering]...
12. Cavity perturbation theory: In mathematics and electronics, Cavity perturbation theory describes methods for derivation of perturbation formulae for performance changes of a cavity resonator. These performance changes are assumed to be caused by either introduction of a small foreign object into the cavity ... (Physics) [81%] 2023-12-30 [Electromagnetism] [Electrical engineering]...
13. Homological perturbation theory: A theory concerning itself with a collection of techniques for deriving chain complexes which are both smaller and chain homotopy equivalent to a given chain complex (cf. also Complex (in homological algebra)). (Mathematics) [81%] 2023-12-30
14. Chiral perturbation theory: Chiral perturbation theory (ChPT) is an effective field theory constructed with a Lagrangian consistent with the (approximate) chiral symmetry of quantum chromodynamics (QCD), as well as the other symmetries of parity and charge conjugation. ChPT is a theory which allows ... (Physics) [81%] 2023-11-12 [Quantum chromodynamics]
15. Cosmological perturbation theory: In physical cosmology, cosmological perturbation theory is the theory by which the evolution of structure is understood in the Big Bang model. Cosmological perturbation theory may be broken into two categories: Newtonian or general relativistic. (Astronomy) [81%] 2024-12-19 [Physical cosmology] [General relativity]...
16. Møller–Plesset perturbation theory: Møller–Plesset perturbation theory (MP) is one of several quantum chemistry post–Hartree–Fock ab initio methods in the field of computational chemistry. It improves on the Hartree–Fock method by adding electron correlation effects by means of Rayleigh–Schrödinger ... (Chemistry) [70%] 2023-12-14 [Computational chemistry] [Theoretical chemistry]...
17. Symmetry-adapted perturbation theory: Symmetry-adapted perturbation theory or SAPT is a methodology in electronic structure theory developed to describe non-covalent interactions between atoms and/or molecules. SAPT is a member of the family of methods known as energy decomposition analysis (EDA). (Physics) [70%] 2023-09-12 [Molecular physics] [Quantum chemistry]...
18. Møller–Plesset perturbation theory: Møller–Plesset perturbation theory (MP) is one of several quantum chemistry post-Hartree–Fock ab initio methods in the field of computational chemistry. It improves on the Hartree–Fock method by adding electron correlation effects by means of Rayleigh–Schrödinger ... (Method in ab initio Quantum Chemistry) [70%] 2024-10-04 [Computational chemistry] [Post-Hartree–Fock methods]...
19. Complete active space perturbation theory: Complete active space perturbation theory (CASPTn) is a multireference electron correlation method for computational investigation of molecular systems, especially for those with heavy atoms such as transition metals, lanthanides, and actinides. It can be used, for instance, to describe electronic ... [63%] 2022-11-14 [Electronic structure methods]
20. Heavy baryon chiral perturbation theory: Heavy baryon chiral perturbation theory (HBChPT) is an effective quantum field theory used to describe the interactions of pions and nucleons/baryons. It is somewhat an extension of chiral perturbation theory (ChPT) which just describes the low-energy interactions of ... (Effective theory for baryons) [63%] 2025-03-02 [Quantum chromodynamics]
21. N-electron valence state perturbation theory: In quantum chemistry, n-electron valence state perturbation theory (NEVPT) is a perturbative treatment applicable to multireference CASCI-type wavefunctions. It can be considered as a generalization of the well-known second-order Møller–Plesset perturbation theory to multireference Complete ... (Chemistry) [57%] 2023-09-18 [Electron states] [Computational chemistry]...