Extended supersymmetry

In theoretical physics, extended supersymmetry is supersymmetry whose infinitesimal generators Q_i^\alpha carry not only a spinor index \alpha, but also an additional index i=1,2 \dots \mathcal{N} where \mathcal{N} is integer (such as 2 or 4).

Extended supersymmetry is also called \mathcal{N}=2, \mathcal{N}=4 supersymmetry, for example. The more extended supersymmetry is, the more it constrains physical observables and parameters. Only the minimal (un-extended) supersymmetry is a realistic conjecture for particle physics, but extended supersymmetry is very important for analysis of mathematical properties of quantum field theory and superstring theory.

See also supersymmetry algebra, harmonic superspace, projective superspace