  A dynamical aspect of quantum gravity on de Sitter spacetime is investigated
by holography or the dS/CFT correspondence. We show that de Sitter spacetime
emerges from a free Sp(N) vector model by complexifying the ghost fields and
flowing them in parallel to the imaginary axis. We confirm that the emergence
of de Sitter spacetime is ensured by conformal symmetry. We also compute the
quantum corrections to the cosmological constant up to the next-to-leading
order of the 1/N expansion in a proposed holographic approach. As a result the
sub-leading corrections have the opposite sign to the classical value.This
implies that a quantum gravity on de Sitter spacetime is perturbatively stable
and quantum effects make the universe flatter and the cosmological constant
smaller.
