I thought this paper worthy of a read
That is a good article the data on the last 10 E foldings is interesting
What do they mean by [providing sensitivity to the microphysics of components,
e.g. their sound speed.]
The simple explanation if I'm reading that line correctly is that small historical perturbations will show in the CMB background I.E. perturbations caused by sound, temperature variations etc. The CMB will keep a memory of those past perturbations.
by the way welcome to the forum
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