An Observational Test of Quantum Cosmology

We compute the tensor CMB anisotropy power spectrum for singular and non-singular instantons describing the beginning of the universe according to the no boundary proposal. For the non-singular instantons we use gently sloping potentials with a sharp negative false vacuum added. The surfaces of constant density break the O(4,1) symmetry of perfect de Sitter space. In the nonsingular instantons this breaking is small, but in singular instantons the singularity makes the breaking much stronger. The effect of the singularity is to suppress long wavelength tensor fluctuations usually called bubble wall fluctuation modes. This alleviates the problem of the large low $l$ $C_l$'s which plagues open inflation theories. Thus singular instantons are observationally favoured over non-singular Coleman De Luccia instantons arising from an equivalent potential but with a sharp false vacuum superposed.