“…Firstly, observations of high-redshift supernovae suggest that the universe may possess a small, positive cosmological constant [1]. Theoretically, there has been much interest in the adS/CFT (conformal field theory) cor-respondence (see [2] for a review) and its more recent relative the dS/CFT correspondence (see, for example, [3]). Finally, a negative cosmological constant is a key ingredient of "brane world" scenarios (see, for example, [4]).…”