What is standard early inflationary cosmology?

[Naty1]

I am wondering whether discussions of inflationary cosmology in these forums generally includes or explicitly excludes prior Plank era and GUT era dynamics. I never gave it any thought until reading the following.

The Wikipedia article provides a perspective I just don't remember from other sources. If inflationary cosmology excludes Planck and GUT eras, are there some alternative pre inflationary dynamics we are supposed to associate with inflation?


http://en.wikipedia.org/wiki/Chronology_of_the_universe

[my boldface emphasis]

...In modern inflationary cosmology, the traditional grand unification epoch, like the Planck epoch, does not exist, though similar conditions likely would have existed in the universe prior to inflation...

The Planck epoch is an era in traditional (non-inflationary) big bang cosmology...

ok

[again my bold]

...In inflationary cosmology, times before the end of inflation (roughly 10−32 second after the Big Bang) follow not the traditional big bang timeline. The universe before the end of inflation is a very cold near-vacuum and persists for much longer than 10−32 second. Times from the end of inflation are based on the big bang time of the non-inflationary big bang model, not on the actual age of the universe at that time, which cannot be determined in inflationary cosmology. Therefore, inflationary cosmology lacks a traditional Planck epoch--though similar conditions may have prevailed in a pre-inflationary era of the universe.

Why is the age of the universe less certain when we stick in inflation??

 

[sadraj]

In fact the ultimate theory of the Cosmology must consist Planck scale, but in inflationary models we "assume" that the energy scale of inflaton field is far lower than Planck energy scale since in Planck scale the Quantum gravity phenomenons become important which we do not know them well.About the GUT scale the point is that if inflation has occurred before GUT symmetry breaking, we encounter the problem of creation of monopoles , which inflationary scenario is invented to solve ! Symmetry breaking of GUT scale (10^-5 M_{planck}) produces so many monopoles , inflation destroys them by means of expanding the universe.

 

[Naty1]

After doing some reading on the subject since I posted, I've become more certain of what I suspected...the above Wikipedia view is one author's view and I strongly suspect not widely shared.

For the record there is a lot of unknown or uncertain quantum activity within inflation itself, not just at Planck scale. That variety is reflected in at least 70 or more inflation models.

Here is one interesting comment from Alan Guth in Scientific American : [The interview may also be of interest to string theory enthusiasts.]

Interview with Guth
http://blogs.scientificamerican.com/degrees-of-freedom/2011/12/06/alan-guth-interview/

The Man Who Put the “Big” in “Big Bang”: Alan Guth on Inflation
By Davide Castelvecchi | December 6, 2011 |

...Virtually all the cosmologists and astronomers I have talked to seem to think that the next big thing in inflation studies will be to look for traces of primordial gravitational waves in the polarization of the cosmic microwave background. In particular, a pattern called the B-mode …. Yes…..The B-mode, if present, would be the sign that we have found the effect of gravity waves, and not just of density perturbations. Gravity waves would give us a handle on the energy scale at which inflation occurred. One of the big uncertainties in the wide class of inflation theories is that inflation may have at happened at any of a tremendously broad range of possible energies.

 

[sadraj]

For polarization data release of Planck we have to wait about 6 months! I thinks the Alan Guth point of view is that if inflation paradigm is correct , its forecast about tensor perturbation should be consistent with the data as well as scalar perturbation. This can confirm the true energy scale choice of inflaton field( about GUT scale.) Almost all of the models predict small tensor perturbation power with respect to scalar power.

 

[bapowell]

Indeed, we don't know what the energy scale of inflation was: in the absence of a primordial B-mode in the CMB, Planck is only able to place an upper bound on the energy scale, something like 10^16 GeV which is on or about GUT scale. So phenomenologically, inflation can occur at the GUT scale. However, it doesn't need to: it is possible to build inflation models that occur closer to the electroweak scale! This would imply either that, yes, there is some pre-inflationary standard cosmology that passes through the GUT scale, or that the universe simply never passed through a GUT era.

 

[sadraj]

bapowell , I am not sure but doesn't too low energy scale of inflation contradicts with solving horizon problem or amplitude of the power spectrum on the CMB?

 

[bapowell]

It has no direct bearing on the horizon problem, which depends on the amount of inflation which is determined by both how long it takes the inflaton to decay or roll to the true vacuum and the energy density. True, the rate of expansion is higher with greater energy density, so low-scale inflation just takes longer to solve the horizon problem.

As far as the amplitude of the scalar perturbations, this depends on the energy scale of inflation but also on the first derivative of the potential; so one can accommodate low-scale inflation by suitably adjusting the slope of the potential.

 

[Mordred]

.In inflationary cosmology, times before the end of inflation (roughly 10−32 second after the Big Bang) follow not the traditional big bang timeline. The universe before the end of inflation is a very cold near-vacuum and persists for much longer than 10−32 second.

this line in the above post in the wiki article referenced above is also inaccurate prior to inflation the average temperatures is hotter prior to inflation not a very cold near vacuum