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superconformal_field_theory [2021/04/06 22:07]
Brian McPeak
— (current)
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-==== Classification of superconformal algebras ==== 
- 
-A classification of possible superconformal algebras was given by [[https://inspirehep.net/literature/120988|Nahm]] in 1977. The outline of the argument is as follows: 
-  - Consider a superalgebra $L = g_0 \oplus g_1$, where $g_0$ and $g_1$ denote the even and odd part of the superalgebra, respectively 
-  - Prove that $L$ must be simple 
-  - The list of simple superalgebras is known. We select from the list the algebras satisfying (a) $g_0$ contains the conformal algebra $so(d, 2)$ and (b) $g_1$ transforms in a spinorial representation of the SC 
-  - the result is the following classification: \begin{align}  
-d = 3: & \qquad \mathfrak{osp}(\mathcal{N}|4) \ \supset \  \mathfrak{so}(3,2) \times  \mathfrak{so}(\mathcal{N})_R \, ,       \\ 
-d = 4: & \qquad \mathfrak{su}(2,2| \mathcal{N}) \ \supset \ \mathfrak{so}(4,2) \times  \mathfrak{su}(\mathcal{N})_R \times \mathfrak{u}(1)_R \, ,           \\ 
-d = 5: & \qquad \mathfrak{f}(4) \ \supset \   \mathfrak{so}(5,2) \times  \mathfrak{su}(2)_R  \(\text{requires } \mathcal{N} = 1)   \,     \\ 
-d = 6: & \qquad \mathfrak{osp}(6,2| \mathcal{N}) \ \supset \      \mathfrak{so}(6,2) \times  \mathfrak{su}(2 \mathcal{N})_R      
- \end{align} 
- 
-The algebras to the right of the $\supset$ denote the maximal bosonic subalgebra. We can see that they each contain the conformal algebra $\mathfrak{so}(d, 2)$, as required by (a).  In addition to assumptions (a) and (b), this result relies on a sort of unitarity assumption-- specifically, we must assume that there is a positive definite inner product on the algebra.