Paritet

Paritet, or parity, is a term used across disciplines to denote equality or symmetry under a transformation. In physics and mathematics it often refers to invariance under spatial inversion or sign changes; in economics it relates to price or exchange-rate relationships; in information technology it can describe a simple error-detection bit. The precise meaning depends on the context, but the core idea is a reference to balance or equivalence between two states.

In physics, parity describes how a physical system behaves under spatial inversion, x becomes -x. The parity operator P acts on a wavefunction and yields an eigenvalue of +1 or -1, indicating even or odd parity. Parity is a conserved quantity in strong and electromagnetic interactions, meaning the physics does not change under inversion. Parity is violated in weak interactions, a discovery that helped establish the V-A structure of the weak force and the Wu experiment. Parity considerations also influence selection rules in nuclear and atomic transitions and play a role in CP violation studies.

In mathematics, parity classifies integers as even or odd, and extends to the sign of a permutation, where even and odd permutations determine the permutation’s parity. These ideas underpin many counting and symmetry arguments in combinatorics and number theory.

In information technology and communications, parity describes a parity bit used for error detection. Even parity means the total number of 1s is even, odd parity means it is odd. Parity checks are simple but limited against burst errors, motivating more robust error-correcting codes.

In economics and finance, parity denotes exchange-rate or price-level relationships between currencies or goods. Purchasing power parity (PPP) and interest rate parity describe conditions under which arbitrage would be eliminated, guiding comparisons of global prices and investment flows.