Posted: Oct 15, 2019 8:08 am
by newolder
Just a cautionary note to add that Paul Steinhardt is of the opinion that inflationary cosmology is equivalent to the end of science because models of inflation can be built to satisfy any set of observations - predicting everything is akin to predicting nothing - to paraphrase*.

For example, Inflation in scale-invariant theories of gravity (published as: Phys. Rev. D 91, 123527 (2015)) shows how these m-theoretic considerations of tensor (gravitational) fluctuation spectra can be reproduced by a model of inflation even if scale invariance is a real feature of early time.

* See, for example, the first minutes of, The unmitigated disaster: