Fotonveld

Fotonveld (photon field) is the quantum field associated with photons, the quanta of the electromagnetic interaction. In quantum field theory, the electromagnetic field is quantized and its excitations are photons. The photon field is a massless, spin-1 gauge field that mediates electromagnetic forces.

In the standard formulation, the dynamics are described by a gauge-invariant Lagrangian, typically written in terms of the field strength tensor Fμν and the vector potential Aμ. The photon field is the mediator of the U(1) gauge symmetry, and its quanta carry no electric charge. Because photons are massless, they have two physical polarization states (helicity ±1) and propagate at the vacuum speed of light.

Quantum mechanically, the photon field is described by field operators that create and annihilate photons. The physical states live in a Fock space, where multi-photon states can be built from the vacuum. Classical electromagnetic waves correspond to coherent states of the photon field, in which the field expectation value behaves like a classical wave.

Photons interact with charged matter through minimal coupling, leading to phenomena described by quantum electrodynamics (QED). While the photons themselves interact very weakly, higher-order processes (such as photon-photon scattering via virtual electron loops) are possible but extremely unlikely. Photons thus act as force carriers for electromagnetism, while also enabling a wide range of technologies in optics and photonics.

Applications and manifestations include coherent light sources, spectroscopy, cosmic microwave background radiation, and various quantum optical experiments that probe the quantum nature of the light field.