fotoneiden
Fotoneiden are hypothetical light-carrying particles proposed in certain beyond-standard-model theories and in science fiction. Unlike ordinary photons, fotoneiden are envisaged to possess either a small but nonzero rest mass, or to interact with matter through additional couplings that are suppressed at low energies. Some models posit hidden sectors in which fotoneiden mix with standard photons, yielding observable effects such as energy-dependent propagation speeds or altered polarization.
In experiments, searches focus on deviations from Coulomb's law, vacuum birefringence, photon regeneration (light-shining-through-walls), and astrophysical
Origins of the idea vary; in science fiction, fotoneiden are often used as plot devices to explore
Related topics include photons, hidden photons, dark photons, axion-like particles, quantum electrodynamics, and spectral distortions.