“parity”的概念、定义、翻译、参考文献-科学参考

parity

Physics

Symbol P. The property of a wave function that determines its behaviour when all its spatial coordinates are reversed in direction, i.e. when x,y,z are replaced by −x,−y,−z. If a wave function ψ‎ satisfies the equation ψ‎(x,y,z)=ψ‎(−x,−y,−z) it is said to have even parity; if it satisfies ψ‎(x,y,z)=−ψ‎(−x,−y,−z) it has odd parity. In general, ψ‎(x,y,z)=Pψ‎(−x,−y,−z), where P is a quantum number called parity that can have the value +1 or −1. The principle of conservation of parity (or space-reflection symmetry) would hold if all physical laws could be stated in a coordinate system independent of left- or right-handedness. If parity was conserved there would therefore be no fundamental way of distinguishing between left and right. In electromagnetic and strong interactions, parity is, in fact, conserved. In 1956, however, it was suggested and subsequently shown that parity is not conserved in weak interactions. In the beta decay of cobalt–60, for example, the electrons from the decay are emitted preferentially in a direction opposite to that of the cobalt spin. This experiment provides a fundamental distinction between left and right. It is not known why parity is violated in the weak interactions but not in the strong or electromagnetic interactions.

Mathematics

The attribute of an integer of being even or odd. Thus, it can be said that 6 and 14 have the same parity (both are even), whereas 7 and 12 have opposite parity. The term also relates to even permutations and odd permutations.

Chemistry

A quantum-mechanical symmetry of a system under inversion (see centrosymmetric molecule). The operation of parity on a quantum state is associated with the parity quantum number P, which has two eigenvalues: +1 and −1, with +1 being said to have even parity, denoted g for gerade, and −1 being said to have odd parity, denoted u for ungerade. Parity is conserved in electromagnetic interactions but not in weak interactions, such as beta decay. The concept of parity was proposed by Eugene Wigner in 1927 and enabled him to explain the Laporte selection rule.

Computer

A function that is computed to provide a check on a group of binary values (e.g. a word, byte, or character) by forming the modulo-2 sum of the bits in the group. The generated sum, a redundant value, is called the parity bit. The parity bit is 0 if the number of 1s in the original group was even. The parity bit is 1 if the number of 1s in the original group was odd.
The parity computation just defined will cause the augmented group of binary values (the original group plus the parity bit) to have an even number of 1s; this is called even parity. In some cases, hardware considerations make it desirable to have an odd number of 1s in the augmented group, and the parity bit is selected to cause the total number of 1s to be odd; this is called odd parity. See also parity check.

Electronics and Electrical Engineering

A count of the number of 1₂ bits (see binary notation) in a data unit, such as a word or message. The parity is odd if there is an odd number of 1₂ bits and even if there is an even number of 1₂ bits. For example, the parity of 101110₂ is even. See also parity check.

单词	parity
释义	parity Physics Symbol P. The property of a wave function that determines its behaviour when all its spatial coordinates are reversed in direction, i.e. when x,y,z are replaced by −x,−y,−z. If a wave function ψ‎ satisfies the equation ψ‎(x,y,z)=ψ‎(−x,−y,−z) it is said to have even parity; if it satisfies ψ‎(x,y,z)=−ψ‎(−x,−y,−z) it has odd parity. In general, ψ‎(x,y,z)=Pψ‎(−x,−y,−z), where P is a quantum number called parity that can have the value +1 or −1. The principle of conservation of parity (or space-reflection symmetry) would hold if all physical laws could be stated in a coordinate system independent of left- or right-handedness. If parity was conserved there would therefore be no fundamental way of distinguishing between left and right. In electromagnetic and strong interactions, parity is, in fact, conserved. In 1956, however, it was suggested and subsequently shown that parity is not conserved in weak interactions. In the beta decay of cobalt–60, for example, the electrons from the decay are emitted preferentially in a direction opposite to that of the cobalt spin. This experiment provides a fundamental distinction between left and right. It is not known why parity is violated in the weak interactions but not in the strong or electromagnetic interactions. Mathematics The attribute of an integer of being even or odd. Thus, it can be said that 6 and 14 have the same parity (both are even), whereas 7 and 12 have opposite parity. The term also relates to even permutations and odd permutations. Chemistry A quantum-mechanical symmetry of a system under inversion (see centrosymmetric molecule). The operation of parity on a quantum state is associated with the parity quantum number P, which has two eigenvalues: +1 and −1, with +1 being said to have even parity, denoted g for gerade, and −1 being said to have odd parity, denoted u for ungerade. Parity is conserved in electromagnetic interactions but not in weak interactions, such as beta decay. The concept of parity was proposed by Eugene Wigner in 1927 and enabled him to explain the Laporte selection rule. Computer A function that is computed to provide a check on a group of binary values (e.g. a word, byte, or character) by forming the modulo-2 sum of the bits in the group. The generated sum, a redundant value, is called the parity bit. The parity bit is 0 if the number of 1s in the original group was even. The parity bit is 1 if the number of 1s in the original group was odd. The parity computation just defined will cause the augmented group of binary values (the original group plus the parity bit) to have an even number of 1s; this is called even parity. In some cases, hardware considerations make it desirable to have an odd number of 1s in the augmented group, and the parity bit is selected to cause the total number of 1s to be odd; this is called odd parity. See also parity check. Electronics and Electrical Engineering A count of the number of 1₂ bits (see binary notation) in a data unit, such as a word or message. The parity is odd if there is an odd number of 1₂ bits and even if there is an even number of 1₂ bits. For example, the parity of 101110₂ is even. See also parity check.
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