Usap, Sasak people. Lombok, 20th century, 46 x 52 cm. From the collection of Dr. Yong Li Lan, Singapore. Photograph by D Dunlop. |

Consider a particle P described by a chronologically ordered chain of events where each orbital cycle $\sf{\Omega}$ can be expressed as a pair of events

$\sf{\Omega} = \left\{ \sf{P}_{\LARGE{\circ}} , \sf{P}_{\LARGE{\bullet}} \vphantom{Q^{2}} \right\}$

that are out of phase with each other so that

$\delta _{\theta} \left( \sf{P}_{\LARGE{\circ}} \right) =- \, \delta _{\theta} \left( \sf{P}_{\LARGE{\bullet}} \right) = \pm \rm{1}$

Then $\sf{P}_{\LARGE{\circ}}$ and $\sf{P}_{\LARGE{\bullet}}$ are called *phase components* of P. If these two sets are composed from the same selection of quarks, then a description of the whole cycle $\sf{\Omega}$ is unaffected if there is any confusion or mix-up about the sign of the phase. This robust indifference to the phase is useful, so we give particles like this a special name: If

$\sf{P}_{\LARGE{\circ}} = \sf{P}_{\LARGE{\bullet}}$

then we say that P has **phase symmetry**. The most important examples of particles with phase symmetry are protons and electrons in their ground-states. So it is possible to make descriptions of protons and electrons that ignore the phase. Alternatively, if $\sf{P}_{\LARGE{\circ}} = \overline{\sf{P} _{\LARGE{\bullet}}}$ then we say that P has **phase anti-symmetry**.

Related WikiMechanics articles.

Summary |

Adjective | Definition | |

Phase Symmetry | $\sf{P}_{\LARGE{\circ}} = \sf{P}_{\LARGE{\bullet}}$ | 6-22 |

Adjective | Definition | |

Phase Anti-Symmetry | $\sf{P}_{\LARGE{\circ}} = \overline{\sf{P} _{\LARGE{\bullet}}}$ | 6-23 |