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In this note, the author says:

But I don't understand how that can be true. All the evidence for the cojecture arises from string theory: Similarity of Large N expansion and the perturbative expansion of a string theory and the equivalent low energy description of N coinciding branes in terms of SUGRA and ##\mathcal N=4 ## SYM(which are both low energy limits of a string theory).

So, how can the author claim that this correspondence is between

Thanks

with the following footnote:The AdS/CFT correspondence is the an exact relationship between any theory of quantum gravity in asymptotically ##AdS_{d+1}## spacetime and an ordinary ##CFT_d## ,without gravity.

Some people might obect to the word ‘any’ here. To be safe, we could say ‘any theory that we

know how to define in the UV and acts like ordinary gravity+QFT in the IR.’

But I don't understand how that can be true. All the evidence for the cojecture arises from string theory: Similarity of Large N expansion and the perturbative expansion of a string theory and the equivalent low energy description of N coinciding branes in terms of SUGRA and ##\mathcal N=4 ## SYM(which are both low energy limits of a string theory).

So, how can the author claim that this correspondence is between

**any**theory of QG and a CFT?Thanks

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