AdS/CFT and the cosmological constant problem
  Within the context of the AdS/CFT correspondence we attempt to formulate the cosmological constant problem in the dual conformal field theory. The fine-tuning of the bulk cosmological constant is related to an apparent fine-tuning in the effective description of the CFT in terms of its light operators: while the correlators of single particle operators satisfy a large N expansion, the expansion does not appear to be natural. Individual terms contributing to correlators have parametrically larger value than the one dictated by large N counting. The final 1/N suppression of correlators is achieved via delicate cancellations between such terms. We speculate on the existence of underlying principles which might make the bulk theory (secretly) natural. 
Kyriakos Papadodimas
hep-th hep-ph