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In particle physics, the history of quantum field theory starts with its creation by Paul Dirac, when he attempted to quantize the electromagnetic field in the late 1920s. Major advances in the theory were made in the 1950s, and led to the introduction of quantum electrodynamics (QED). QED was so successful and "natural" that efforts were made to use the same basic concepts for the other forces of nature. These efforts were successful in the application of gauge theory to the strong nuclear force and weak nuclear force, producing the modern standard model of particle physics. Efforts to describe gravity using the same techniques have, to date, failed. The study of quantum field theory is alive and flourishing, as are applications of this method to many physical problems. It remains one of the most vital areas of theoretical physics today, providing a common language to many branches of physics. == History == Quantum field theory originated in the 1920s from the problem of creating a quantum mechanical theory of the electromagnetic field. In particular, de Broglie in 1924 introduced the idea of a wave description of elementary systems in the following way: "we proceed in this work from the assumption of the existence of a certain periodic phenomenon of a yet to be determined character, which is to be attributed to each and every isolated energy parcel".〔Recherches sur la theorrie des quanta (ann. de Phys., 10, III, 1925; translation by A. F. Kracklauer)〕 In 1925, Werner Heisenberg, Max Born, and Pascual Jordan constructed just such a theory by expressing the field's internal degrees of freedom as an infinite set of harmonic oscillators, and by then utilizing the canonical quantization procedure to these oscillators.〔Todorov, Ivan (2012). "Quantization is a mystery", ''Bulg. J. Phys.'' 39 (2012) 107–149 ; arXiv: 1206.3116 ()〕〔 The paper was received on 16 November 1925. (translation in: )〕 This theory assumed that no electric charges or currents were present and today would be called a free field theory. The first reasonably complete theory of quantum electrodynamics, which included both the electromagnetic field and electrically charged matter (specifically, electrons) as quantum mechanical objects, was created by Paul Dirac in 1927.〔Dirac, P.A.M. (1927). ''The Quantum Theory of the Emission and Absorption of Radiation'', Proceedings of the Royal Society of London, Series A, Vol. 114, p. 243.〕 This quantum field theory could be used to model important processes such as the emission of a photon by an electron dropping into a quantum state of lower energy, a process in which the ''number of particles changes''—one atom in the initial state becomes an atom plus a photon in the final state. It is now understood that the ability to describe such processes is one of the most important features of quantum field theory. The final crucial step was Enrico Fermi's theory of ''β''-decay (1934).〔Chen Ning Yang (2012). "Fermi's β-decay Theory", ''Asia Pac. Phys. Newslett.'' 01, p 27 . doi: 10.1142/S2251158X12000045 (online )〕〔Fermi, E. (1934). "Versuch einer Theorie der -Strahlen", ''Z. Phys.'' 88 161–177, doi: 10.1007/BF01351864〕 In it, fermion species nonconservation was shown to follow from second quantization: creation and annihilation of fermions came to the fore and quantum field theory was seen to describe particle decays. 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「History of quantum field theory」の詳細全文を読む スポンサード リンク
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