The lowest multipole moments of the cosmic microwave background (CMB) are smaller than expected for a scale-invariant power spectrum. One possible explanation is a cutoff in the primordial power spectrum below a comoving scale of $k_c\simeq 5.0\times {10}^{-4}{\mathrm{M}\mathrm{p}\mathrm{c}}^{-1}$. Such a cutoff would increase significantly the cross correlation between the large-angle CMB and cosmic-shear patterns. The cross correlation may be detectable at $>2\sigma$ which, combined with the low CMB moments, may tilt the balance between a $2\sigma$ result and a firm detection of a large-scale power-spectrum cutoff. The cutoff also increases the large-angle cross correlation between the CMB and the low-redshift tracers of the mass distribution.

• Received 27 June 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.221302