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In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines classical field theory, special relativity, and quantum mechanics. [1]: xi QFT is used in particle physics to construct physical models of subatomic particles and in condensed matter physics to construct models of quasiparticles.
Quantum mechanics is a fundamental theory that describes the behavior of nature at and below the scale of atoms. [2]: 1.1 It is the foundation of all quantum physics, which includes quantum chemistry, quantum field theory, quantum technology, and quantum information science. Quantum mechanics can describe many systems that classical physics cannot.
The idea of quantum field theory began in the late 1920s with British physicist Paul Dirac, when he attempted to quantize the energy of the electromagnetic field; just as in quantum mechanics the energy of an electron in the hydrogen atom was quantized. Quantization is a procedure for constructing a quantum theory starting from a classical theory.
The quantum theory of fields (vol 2), by S. Weinberg (Cambridge University Press, 1996) ISBN 0-521-55002-5. Quantum Field Theory in a Nutshell (Second Edition), by A. Zee (Princeton University Press, 2010) ISBN 978-1-4008-3532-4. An Introduction to Particle Physics and the Standard Model, by R. Mann (CRC Press, 2010) ISBN 978-1420082982
In quantum theory however there is always an "external" field, namely the source-free or vacuum field E 0 (t). According to our earlier equation for a k λ ( t ) the free field is the only field in existence at t = 0 as the time at which the interaction between the dipole and the field is "switched on".
In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. [ 1 ] [ 2 ] [ 3 ] In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved. [ 2 ]
This is a list of quantum field theories. The first few sections are organized according to their matter content, that is, the types of fields appearing in the theory. This is just one of many ways to organize quantum field theories, but reflects the way the subject is taught pedagogically.
A classical field theory is a physical theory that predicts how one or more fields in physics interact with matter through field equations, without considering effects of quantization; theories that incorporate quantum mechanics are called quantum field theories.