Quantum Scalar Fields on Anti-de Sitter Spacetime
  We investigate the propagation of arbitrarily coupled scalar fields on the $N$-dimensional hyperbolic space ${\mathbb H}^N$. Using the $\zeta$-function regularization we compute exactly the one loop effective action. The vacuum expectation value of quadratic field fluctuations and the one loop renormalized stress tensor are then computed using the recently proposed direct $\zeta$-function technique. Our computation tests the validity of this approach in presence of a continuous spectrum. Our results apply as well to the $N$-dimensional anti-de Sitter spacetime, whose appropriate euclidean section is the hyperbolic space ${\mathbb H}^N$. 
Marco M. Caldarelli