not_Fritz_Argelander

Dr H on the status of inflation

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by , 03-09-2019 at 07:17 PM (344 Views)
Quote Originally Posted by not_Fritz_Argelander View Post
Quote Originally Posted by not_Fritz_Argelander View Post
PS To clarify..... A "plain vanilla" Big Bang is falsified by CMB uniformity and flatness so a Big Bang model with inflation survives the tests. One can also have CMB uniformity and flatness in a Big Bounce cosmology. The Big Bounce is also testable as described in this technical treatment.

https://www.researchgate.net/publica...A_Brief_Review

The tests involve measuring DM mass and interaction cross section and weirdness in the thermal history of same.

In addition I recall but cannot quickly locate a discussion where SMBHs survive the Bounce. So finding SMBHs way too early would indicate Big Bounce rather than Inflationary Big Bang.
This is a charming little paper, which is much easier to read on a laptop than a mobile device.

It’s not brilliant but is quite workmanlike and well done.

The key insight is that the fraction of the universe that is in dark matter has different dependencies on the DM particle interaction cross section and mass.

In the Standard Cosmology (inflation) the interaction cross section is fixed and independent of the DM particle mass. So the interaction cross section is fixed and independent of DM particle mass.

In the Big Bounce without inflation the interaction cross section has to decrease as the inverse mass squared. If the DM particle is sufficiently massive its interaction cross section would have to be too small to be detected with terrestrial experiments. (It eventually gets to be below the cosmic neutrino background and undetectable.)

It is tempting (the authors fail to be tempted, so this is just me) to see the failure of DM searches at the LHC as indicating indirect evidence for Bounce rather than Bang. As the parameter space gets searched more rigorously this firms up.

Anyway a direct laboratory detection of a DM particle would enable deciding between an Inflationary Big Bang and a Big Bounce cosmology. Definitively. So a decision is possible in principle.

One other entertaining feature is that the Big Bounce provides pathways for non-equilibrium production of particles. So, me again, this might provide the time reversal symmetry breaking that can explain the matter-antimatter asymmetry?

I have to leave it there. Love the paper. I’m going to blog it and come back to it later but there is no way to do this justice with the limited time I have available.

Again, "theoretical" is a good thing. The idea that experimental data is superior to theoretical insight is simply false. Everything we know "for sure" is "theoretical". Bad theories get weeded out by Nature. You don't even know what data to collect without a theory.

"Man proposes, Nature disposes".
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