In physics, decoupling is the general phenomenon in which the interactions between some physical objects (such as elementary particles) disappear. Physics (from the Greek, φυσικός (phusikos), natural, and φύσις (phusis), nature) is the science of nature in the broadest sense. ... Generally, an interaction is a kind of action which occurs as two or more objects have an effect upon one another. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ...

The term "decoupling" is used in many different contexts.

In gauge theories, there are unobserved polarizations of elementary particles, such as the longitudinal photon. The experiments as well as theoretical consistency dictates that these polarizations cannot be produced by collisions of other particles. Consequently, their interactions with other (physical) particles must be equal to zero, and quantum electrodynamics confirms this expectation: decoupling is a consequence of gauge symmetry. Gauge theories are a class of physical theories based on the idea that symmetry transformations can be performed locally as well as globally. ... This article treats polarization in electrodynamics. ... The term, longitudinal means front-to-back or top-to-bottom as opposed to transverse which means side-to-side. In automotive engineering, the term, longitudinal refers to an engine in which the crankshaft is oriented along the long axis of the vehicle, front to back. ... In physics, the photon (from Greek φοτος, meaning light) is a quantum of excitation of the quantised electromagnetic field and is one of the elementary particles studied by quantum electrodynamics (QED) which is the oldest part of the Standard Model of particle physics. ... Consistency has three technical meanings: In mathematics and logic, as well as in theoretical physics, it refers to the proposition that a formal theory or a physical theory contains no contradictions. ... Quantum electrodynamics (QED) is a quantum field theory of electromagnetism. ... Gauge theories are a class of physical theories based on the idea that symmetry transformations can be performed locally as well as globally. ...

In cosmology, the term "decoupling" is often used for the moment of recombination when electrons became bound to atomic nuclei, producing Cosmic Microwave Background as we know it. Cosmology is the study of the large-scale structure and history of the universe. ... Recombination usually denotes a genetic event that occurs during the formation of sperm and egg cells (especially in areas of study of biology topics). ... Properties The electron (sometimes called negatron; commonly represented as e−) is a subatomic particle. ... The nucleus (atomic nucleus) is the center of an atom. ... WMAP image of the CMB anisotropy,Cosmic microwave background radiation(June 2003) The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe. ...