Posted: Oct 15, 2019 1:56 pm
by newolder
The 2011-ish claim was that upcoming data on CMBR polarisation and its relation to tensor (gravitational) fluctuation spectra would be a decisive clincher between ekpyrotic (Steinhardt & Turok) and inflationary cosmology models. Since the 2015 paper above, and Steinhardt's earlier warning about how inflationary models may used to predict anything, this is no longer the case.

From Steinhardt's website, his recent work finds the M-theoretic extra dimensions "inessential" to his current ideas on bouncing cosmology.

A. Ijjas, P.J. Steinhardt

Bouncing Cosmology made simple, Class. Quantum Grav. 35 (2018) 135004

An intuitive way to illustrate how cosmological models with a classical (nonsingular) bounce generically resolve fundamental problems in cosmology. (Note that the earliest versions of bouncing cosmology (see Khoury et al. below) were based on colliding branes in extra dimensions; but those elements are inessential in current bouncing cosmology models, which are based on ordinary scalar fields in four space-time dimensions.)

I'm not familiar, yet, with any predictions from this work but from an early read of A new kind of cyclic universe
We emphasize that we do not invoke extra dimensions, branes, and other elements inspired by string theory for this new approach to cyclic cosmology.