It is theorized that during inflation gravitational waves are produced. See this article by Guzzetti, Bartolo, Liguori, and Matarrese (Cornell University). Or this one by Liu, Guo, Cai, and Shiu (Cornell University). Primordial gravitational waves are produced and proven to exist
Recent observation of B mode polarizations encoded in CMB anisotropy has indicated the presence of primordial gravity waves.
I'm not sure if this is caused by inflation or if they were already present before inflation started (in an eternal inflation scenario these waves had to co-exist with inflation).
My question is:
What, in theory, determines the frequency of the produced waves. One has to know the mechanism for calculating this, I guess. But what's the key feature?