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oink
Punatic

USA
2688 Posts

Posted - 01/12/2018 :  22:01:17  Show Profile  Reply with Quote
quote:
"By comparing the Bayesian evidence for the models, we find that (Lambda)CDM does a better job globally, while the holographic models provide a (marginally) better fit to data without very low multipoles (i.e. l<=30), where the dual QFT becomes non-perturbative."

Say what?

Pua`a
S. FL
Big Islander to be.
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TomK
Punatic

USA
6328 Posts

Posted - 01/12/2018 :  22:29:42  Show Profile  Visit TomK's Homepage  Reply with Quote
As I said, it was written by a cosmologist. That's actually the "easiest" sentence to understand, you're fortunate I didn't quote the whole abstract, which says:

"We test a class of holographic models for the very early universe against cosmological observations and find that they are competitive to the standard (Lambda)CDM model of cosmology. These models are based on three dimensional perturbative super-renormalizable Quantum Field Theory (QFT), and while they predict a different power spectrum from the standard power-law used in (Lambda)CDM, they still provide an excellent fit to data (within their regime of validity). By comparing the Bayesian evidence for the models, we find that (Lambda)CDM does a better job globally, while the holographic models provide a (marginally) better fit to data without very low multipoles (i.e. l<=30), where the dual QFT becomes non-perturbative. Observations can be used to exclude some QFT models, while we also find models satisfying all phenomenological constraints: the data rules out the dual theory being Yang-Mills theory coupled to fermions only, but allows for Yang-Mills theory coupled to non-minimal scalars with quartic interactions. Lattice simulations of 3d QFT's can provide non-perturbative predictions for large-angle statistics of the cosmic microwave background, and potentially explain its apparent anomalies."

Maybe that's a little clearer? ;)

Personally, I prefer not being a cosmologist, I think it can do harm to your mental health...
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TomK
Punatic

USA
6328 Posts

Posted - 01/13/2018 :  02:02:17  Show Profile  Visit TomK's Homepage  Reply with Quote
This should clear things up.

Bzowksi et al, 2012:

"We provide a precise and quantitative holographic description of a class of inflationary slow-roll models. The dual QFT is a deformation of a three-dimensional CFT by a nearly marginal operator, which, in the models we consider, generates an RG flow to a nearby IR fixed point. These models describe hilltop inflation, where the inflaton rolls from a local maximum of the potential in the infinite past (corresponding to the IR fixed point of the dual QFT) to reach a nearby local minimum in the infinite future (corresponding to the UV of the dual QFT). Through purely holographic means, we compute the spectra and bispectra of scalar and tensor cosmological perturbations. The QFT correlators to which these observables map holographically may be calculated using conformal perturbation theory, even when the dual QFT is strongly coupled. Both the spectra and the bispectra may be expressed this way in terms of CFT correlators that are fixed, up to a few constants, by conformal invariance. The form of slow-roll inflationary correlators is thus determined by the perturbative breaking of the de Sitter isometries away from the fixed point. Setting the constants to their values obtained by AdS/CFT at the fixed point, we find exact agreement with known expressions for the slow-roll power spectra and non-Gaussianities."

QED. Any questions?
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oink
Punatic

USA
2688 Posts

Posted - 01/13/2018 :  05:50:47  Show Profile  Reply with Quote
Thanks for taking time for such a through response, I think. I only have one thing to say. Uncle!

Pua`a
S. FL
Big Islander to be.
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