| 单词 | parity |
| 释义 | parity 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 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 |
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