On the absolutely continuous spectrum of the Laplace-Beltrami operator acting on p-forms for a class of warped product metrics

We explicitely compute the absolutely continuous spectrum of the Laplace-Beltrami operator for $p$-forms for the class of warped product metrics $d{\sigma }^2=y^{2a}d{y}^2+y^{2b}d{\theta }_{{\text{Sphere}}^{N-1}}^2$, where $y$ is a boundary defining function on the unit ball B(0,1) in ${\text{Real}}^N$.