| 摘要: |
In the measurements of cosmic microwave background polarizations, three frequency channels are necessary for discriminating the primordial B-modes from the polarized dust and the synchrotron emission. We carry out an optimistic estimate on the sensitivity to the detection of primordial gravitational waves using the cosmic microwave background B-modes only, and explore how to reach the thresholds for the tensor-to-scalar ratio r in the theoretically well-motivated inflation models. For example, Lyth bound implies r similar or equal to 2 x 10(-3) , a corrected Lyth bound shows r similar or equal to 7 x 10(-4), and some typical inflation models gives r similar or equal to 4 x 10(-5). Taking into account the up-to-date constraints on r, i.e. r(0.05) < 0.07 at 95 per cent confidence, we find that the consistency relation n(t) = -r/8 in the canonical single-field slow-roll inflation cannot be distinguished from the scale invariance, due to the cosmic variance in the power spectrum of cosmic microwave background B modes. The cosmic variance places an inevitable limit on the measurements of the tensor spectral index, i.e. sigma(nt) similar or equal to 0.01 for 2 <= l <= l(max) = 300. |
