A Test for Inflation:

[beecee]

https://phys.org/news/2019-03-big.html

What happened before the Big Bang?

March 26, 2019, Harvard-Smithsonian Center for Astrophysics:

A team of scientists has proposed a powerful new test for inflation, the theory that the universe dramatically expanded in size in a fleeting fraction of a second right after the Big Bang. Their goal is to give insight into a long-standing question: what was the universe like before the Big Bang?

Although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the universe, other very different theories can also explain these mysteries. In some of these theories, the state of the universe preceding the Big Bang – the so-called primordial universe – was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.

To help decide between inflation and these other ideas, the issue of falsifiability – that is, whether a theory can be tested to potentially show it is false – has inevitably arisen. Some researchers, including Avi Loeb of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Mass., have raised concerns about inflation, suggesting that its seemingly endless adaptability makes it all but impossible to properly test.

Read more at: https://phys.org/news/2019-03-big.html#jCp

the paper:

https://arxiv.org/pdf/1809.02603.pdf

17 Feb 2019

Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum:

Massive fields in the primordial Universe function as standard clocks and imprint clock signals in the density perturbations that directly record the scale factor of the primordial Universe as a function of time, a(t). A measurement of such signals would identify the specific scenario of the primordial Universe in a model-independent fashion. In this Letter, we introduce a new mechanism through which quantum fluctuations of massive fields function as standard clocks. The clock signals appear as scale-dependent oscillatory signals in the power spectrum of alternative scenarios to inflation.

[QuantumT]

3 hours ago, beecee said:

Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum:

Massive fields in the primordial Universe function as standard clocks and imprint clock signals in the density perturbations that directly record the scale factor of the primordial Universe as a function of time, a(t). A measurement of such signals would identify the specific scenario of the primordial Universe in a model-independent fashion. In this Letter, we introduce a new mechanism through which quantum fluctuations of massive fields function as standard clocks. The clock signals appear as scale-dependent oscillatory signals in the power spectrum of alternative scenarios to inflation.

Sorry, I got lost in technical terms and loanwords. Can anyone translate it to "normal" english, or will I have to break it down word by word on my own?

Edited March 27, 2019 by QuantumT

[beecee]

19 hours ago, QuantumT said:

Sorry, I got lost in technical terms and loanwords. Can anyone translate it to "normal" english, or will I have to break it down word by word on my own?

I wouldn't really attempt to "translate" for you, other then overall it is a method of possibly falsifying Inflation as we understand it, from other possible scenarios via an energy scale at before the "horizon" which I assume is the quantum/Planck level at t+10-43 seconds? One of those scenarios is whether the BB was possibly part of a "Big Bounce"?

I echo your requests though, and would ask someone more attuned to the technical terms used to explain more fully.

extract:

We conclude by making the following interesting comparison between the inflation and alternative scenarios. The energy scale of horizon during inflation is roughly a constant. Particles with a mass around or below this scale are created quantum mechanically and leave their imprints in the shapes of non-Gaussianities of the density perturbations. In this sense, inflation works like a particle collider with a fixed energy scale [29–45]. In contrast, the energy scale of the horizon in alternative scenarios increases with time. Fields with a mass much larger than the horizon scale (and hence more difficult to create spontaneously) may eventually become lighter (hence easier to create). These are the fields of interest here. We have shown that with some generic assumptions on the initial state, they leave imprints in the density perturbations in terms of scale-dependent oscillatory signals. These signals appear in wave numbers that satisfy condition (4) or (10) for contraction or expansion scenarios, respectively (see Fig. 4). Therefore, the alternative scenarios are more like particle scanners – they scan over a tower of massive fields one by one and display each of them as a pulse of signals at different length scales in the density perturbations. Besides particle spectra, clock signals from both types of particle detectors also carry direct information about a(t), and therefore are predictions which can be used to falsify competing primordial Universe scenarios in a model-independent fashion.

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I also checked on the defining of the title of the paper, Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum" 

https://ned.ipac.caltech.edu/level5/Sept02/Kinney/Kinney4_6.html

Primordial Power Spectrum:

and this..........https://arxiv.org/pdf/1406.4827.pdf

Primordial power spectrum from Planck: 

Abstract.

Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near ` ∼ 750 − 850 represents the most prominent feature in the data. Feature near ` ∼ 1800 − 2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ∼ 2.5%. In this context low-` and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

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https://en.wikipedia.org/wiki/Primordial_fluctuations

Request still stands.

Edited March 27, 2019 by beecee