The membrane at the end of the (de Sitter) universe

Abstract The original membrane at the end of the universe corresponds to a probe M2-brane of signature ( 2 , 1 ) occupying the S 2 × S 1 boundary of the ( 10 , 1 ) spacetime AdS 4 × S 7 , and is described by an OSp ( 4 / 8 ) SCFT. However, it was subsequently generalized to other worldvolume signatures ( s , t ) and other spacetime signatures ( S , T ) . An interesting special case is provided by the ( 3 , 0 ) brane at the end of the de Sitter universe dS 4 which has recently featured in the dS/CFT correspondence. The resulting CFT contains the one recently proposed as the holographic dual of a four-dimensional de Sitter cosmology. Supersymmetry restricts S, T, s, t by requiring that the corresponding bosonic symmetry O ( s + 1 , t + 1 ) × O ( S − s , T − t ) be a subgroup of a superconformal group. The case of dS 4 × AdS 7 is ‘doubly holographic’ and may be regarded as the near horizon geometry of N 2 M2-branes or equivalently, under interchange of conformal and R-symmetry, of N 5 M5-branes, provided N 2 = 2 N 5 2 . The same correspondence holds in the pp-wave limit of conventional M-theory.