#### nrqed

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"Typically the number of copies of a supersymmetry is a power of 2, i.e. 1, 2, 4, 8. In four dimensions, a spinor has four degrees of freedom and thus the minimal number of supersymmetry generators is four in four dimensions and having eight copies of supersymmetry means that there are 32 supersymmetry generators."

Why is that we consider only powers of 2? I don't see why this follows from the basic definition of the algebra.

Also, a simple question: does anyone know the origin of the term "R symmetry"? Why is it called this way? A wild guess would be that the R stands for "rotation" as it implements a kind of rotation between the fields but I am only guessing here, I would appreciate knowing for sure where it comes from.

Thanks