Double-trace operators and one-loop vacuum energy in AdS/CFT

We perform a one-loop calculation of the vacuum energy of a tachyon field in anti-de Sitter space with boundary conditions corresponding to the presence of a double-trace operator in the dual field theory. Such an operator can lead to a renormalization group flow between two different conformal field theories related to each other by a Legendre transformation in the large N limit. The calculation of the one-loop vacuum energy enables us to verify the holographic c theorem one step beyond the classical supergravity approximation.