Inflation creates both scalar (density) and tensor (gravity wave) metric perturbations. We find that the tensor-mode contribution to the cosmic microwave background anisotropy on large-angular scales can only exceed that of the scalar mode in models where the spectrum of perturbations deviates significantly from scale invariance (e.g., extended and power-law inflation models and extreme versions of chaotic inflation). If the tensor mode dominates at large-angular scales, then the value of ΔT/T predicted on 1° is less than if the scalar mode dominates, and, for cold-dark-matter models, bias factors b>1 can be made consistent with Cosmic Background Explorer Differential Microwave Radiometer results.

• Received 22 June 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.1856