The next phrase mentions that this theory is testable
>Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions.
I'm very curious to know how.
>Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions.
I'm very curious to know how.
Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especially given that bulk temperature is so close (i.e. ∼ 20% of) the 5D Planck temperature. In the context of our model, the red tilt of the cosmological power spectrum implies that the amplitude of 5D bulk graviton propagator, which enters in Eq. (4.8), is getting stronger in the IR, suggesting gradual unfreezing of additional polarizations of graviton.
But that's the point, innit. Who's to say we don't discover magic quantum carbon nanotubes or something thing that makes it feasible to setup a graviton detector at some point in the future. And who's to say it won't be useful, either.
I'm serious; the Higgs-Boson was theorized to exist in 1964, and was proven to exist only after great expense in 2012, utilizing many cutting edge technologies.
General Relativity was theorized in 1915, but not really tested in 1959, and now I use it almost every day in the form of GPS.
As per Einstein, it's true that accurate measurements of his GR effects didn't come along for decades, but he was answering known physical problems. And the crude measurements of his day aligned with his predictions, they just weren't accurate yet.
I bet you there are a lot of efforts made right now to find a way to measure them!
Saying a scientific hypothesis is untestable "in principle" is a deathknell while untestable "in practice" is not.