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I was watching this https://www.youtube.com/watch?v=Iz2ie3i1Gh0 about Ads/CFT. Very nice video from the master himself. I got confused though about what he calls $N$. Basically he says $N$ is the number of fields and that it should be $N >> 1$ for AdS/CFT to work.

I thought $N$ in this context usually means the number of super symmetries. Is he just being confusing? Sloppy? Or what's going on?

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In Maldacena’s original paper two different “n”’s are mentioned in the abstract - $N$ and $\cal{N}$. As Prahar says in the comments, $N$ represents the rank of $SU(N)$ and $\cal{N}$ represents the number of super-symmetries.

Throughout the paper, Maldacena notes that "for large $N$" such and such happens - and, early on in the introduction, "Therefore the solutions can be trusted as long as N is large". This explains the mention of the need for $N >> 1$. Also see section 7 in this for an explanation of the constraints on $N$ and $\cal{N}$.

Hope this helps!

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