# Primordial gravitational wave constraints from Planck 2015

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1. Aug 12, 2015

### Garth

In today's Physics ArXiv: New constraints on primordial gravitational waves from Planck 2015.

Authors Luca Pagano, Laura Salvati, and Alessandro Melchiorri of the Physics Department and INFN, Universita di Roma.
Primordial gravitational waves from the universe exiting Inflation get more and more elusive.

Garth

2. Aug 12, 2015

### Chronos

We already know our deuterium counts dont match predictions, so I find it unsurprising to get peculiar results when they are wedged into the mix.

3. Aug 12, 2015

### Garth

Well, they used deuterium to get lowest upper bound - their Table 1 shows the upper bounds without deuterium as well.

Planck + BAO + lensing gives $\Omega_{gw} h^2 < 1.9 \times 10^{-6}$, still rather elusive!

Garth

4. Aug 13, 2015

### bcrowell

Staff Emeritus
How does deuterium relate to any of this?

5. Aug 13, 2015

### Garth

To constrain $\Omega_b$?

Only a guess, but they claim to get a lower upper bound on $\Omega_{gw}h^2$ from 1.9 to 1.7 x 10-6.

As I said that is pretty immaterial as the 1.9 x 10-6 upper limit still leaves any such gws pretty insignificant.

Garth