Decoupling

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In physics, decoupling is the general phenomenon in which the interactions between some physical objects (such as elementary particles) disappear.

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.

In physical cosmology, the term "decoupling" is often used for the moment during recombination when the rate of compton scattering became slower than the expansion of the universe, producing Cosmic Microwave Background as we know it.

In electronics, decoupling refers to the practice of connecting localized capacitors close to the power leads of integrated circuits to act as a small localized energy reservoir, which supplies the circuit with current during transient, high current demand periods. See decoupling capacitor.

In rail transport, decoupling is the separation of two railroad cars by manipulation of their couplers

In Inventory Management, "decoupling" allows economy of scale within a single facility and permits each process to operate at maximum efficiency rather than having the speed of the entire process constrained by the slowest.

In the underground nuclear testing (the testing of nuclear weapons), decoupling refers to the attempt to prevent some of the bomb's energy from transmitting as seismic waves. This makes it more difficult for outside observers to estimate the nuclear yield of the weapon being tested.