### quantum field theory

**(QFT)**
(reworking of quantum mechanics incorporating fields)

A **quantum field theory** (**QFT**) is a type of modern-physics
theory that treats "everything" as fields, with particles
considered to be fields, or depending upon how you look at it,
particles are an emergent phenomena from the excitation of fields
(i.e., a portion of a field above the ground state).
A QFT can handle the physics problems that quantum mechanics
addresses, and also has the advantage of modeling quantum-scale
(atomic scale and smaller) mechanical phenomena that is taking place
within a field such as an electric field or magnetic field.
They also have the advantages of more ease in handling many particles
and having a well-established, usable way of incorporating the
effects of special relativity.

QFTs vary based upon a quantity called a **coupling constant**.
Different coupling constants are valid for different circumstances,
and a QFT is termed a
**strongly-coupled quantum field theory** (or **strongly-coupled QFT**)
or a **weakly-coupled quantum field theory** (or **weakly-coupled QFT**).
The strong force has a *strong* coupling constant,
a motivation for the terms.

**Quantum electrodynamics** (**QED**) is a particular (kind of) QFT
addressing just one type of field: *electric fields*. QED problems
are generally addressed using a perturbation theory, an
approximation approach that is effective and useful for appropriate
circumstances. **Quantum chromodynamics** (**QCD**) is a particular
QFT that includes the *strong force*.

(*physics,mechanics,atoms*)
**Further reading:**

http://en.wikipedia.org/wiki/Quantum_field_theory

http://en.wikipedia.org/wiki/Coupling_constant

http://en.wikipedia.org/wiki/Quantum_electrodynamics

http://en.wikipedia.org/wiki/Quantum_chromodynamics

**Referenced by pages:**

conformal field theory (CFT)

Chern-Simons gravity

effective field theory (EFT)

fuzzy dark matter (FDM)

quantum fluctuations

quantum mechanics (QM)

Index