On testing and extending the inflationary consistency relation for tensor modes

TL;DR

This paper discusses testing the inflationary consistency relation for tensor modes using future CMB polarization experiments and extends the relation to solar system scales to improve early universe insights.

Contribution

It proposes methods to verify the inflationary consistency relation across different scales, including CMB and solar system measurements, enhancing tests of early universe models.

Findings

Future CMB experiments can confirm the negative tensor spectral index prediction.

Extending the relation to solar system scales allows for more stringent tests.

Proposes using gravitational wave density measurements for early universe insights.

Abstract

If observations confirm BICEP2's claim of a tensor-scalar ratio $r\approx 0.2$ on CMB scales, then the inflationary consistency relation $n_{t}=-r/8$ predicts a small negative value for the tensor spectral index $n_t$. We show that future CMB polarization experiments should be able to confirm this prediction at several sigma. We also show how to properly extend the consistency relation to solar system scales, where the primordial gravitational wave density $\Omega_{gw}$ could be measured by proposed experiments such as the Big Bang Observer. This would provide a far more stringent test of the consistency relation and access much more detailed information about the early universe.