Multiplet
In physics, multiplet can mean:
- A group of related spectral lines
- A group of related subatomic particles
The best known example is a spin multiplet, which is a group representation of an SU(2) subgroup of the Lorentz algebra. For example, a spin singlet is a trivial representation, a spin doublet is a fundamental representation and a spin triplet is a vector representation.
In other cases, the term multiplet usually refers to the fundamental representation of a gauge algebra. For example, in QCD, quarks are in a multiplet of SU(3).