paritychanging

Paritychanging is the notion of changing the parity of a system or state, where parity is the property of an object or a mathematical state under inversion. In physics, parity refers to how a wavefunction or an arrangement behaves when spatial coordinates are inverted through the origin. A parity-changing process maps a state with a given parity to a state of opposite parity.

In quantum mechanics, a process that does not conserve parity is called parity-violating or parity-changing. The weak nuclear force does not respect parity, leading to observed parity violation in certain decays. Classic experiments, such as the Wu experiment on cobalt-60 beta decay, demonstrated that angular distributions depend on spin orientation, signaling parity nonconservation. Parity-changing transitions also occur in certain nuclear and particle processes where selection rules permit a flip of parity between initial and final states.

In spectroscopy and molecular physics, many electric-dipole transitions require a change in parity. For atoms and centrosymmetric molecules, transitions between states of the same parity are often forbidden, while transitions with opposite parity are allowed, reflecting a parity change in the transition. The concept is used in selection rules and in interpreting spectra.

In information technology and data transmission, parity refers to a simple redundancy check. A parity-changing operation flips a parity bit to convert data into a form suitable for error detection, or to correct errors by authentication with a parity scheme. In mathematics, parity describes even or odd properties; parity-changing mappings toggle between these classes. See also parity violation, parity operator, and error-detection schemes.