| 翻訳と辞書 |
| Faddeev–Popov ghost ： ウィキペディア英語版 |
Faddeev–Popov ghost
In physics, Faddeev–Popov ghosts (also called gauge ghosts or ghost fields) are additional fields which are introduced into gauge quantum field theories to maintain the consistency of the path integral formulation. They are named after Ludvig Faddeev and Victor Popov.〔 L. D. Faddeev and V. N. Popov, (1967). "Feynman Diagrams for the Yang-Mills Field", ''Phys. Lett.'' B25 29.〕〔W. F. Chen. (Quantum Field Theory and Differential Geometry )〕
There is also a more general meaning of the word "ghost" in theoretical physics, which is discussed below (see ''general ghosts in theoretical physics'').
==Overcounting in Feynman path integrals==
The necessity for Faddeev–Popov ghosts follows from the requirement that in the path integral formulation, quantum field theories should yield unambiguous, non-singular solutions. This is not possible when a gauge symmetry is present since there is no procedure for selecting any one solution from a range of physically equivalent solutions, all related by a gauge transformation. The problem stems from the path integrals overcounting field configurations related by gauge symmetries, since those correspond to the same physical state; the measure of the path integrals contains a factor which does not allow obtaining various results directly from the original action using the regular methods (e.g., Feynman diagrams). It is possible, however, to modify the action, such that the regular methods will be applicable by adding some additional fields, which break the gauge symmetry, which are called the ''ghost fields''. This technique is called the "Faddeev–Popov procedure" (see also BRST quantization). The ghost fields are a computational tool in that they do not correspond to any real particles in external states: they ''only'' appear as virtual particles in Feynman diagrams – or as the ''absence'' of some gauge configurations. However they are necessary to preserve unitarity.
The exact form or formulation of ghosts is dependent on the particular gauge chosen, although the same physical results are obtained with all the gauges. The Feynman-'t Hooft gauge is usually the simplest gauge for this purpose, and is assumed for the rest of this article.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Faddeev–Popov ghost」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|