Was there a maximum speed during Inflation?

[geordief]

Were there any processes occurring in the Inflation epoque  ?

If there were ,was there a maximum speed limit different to c? 

I am guessing that there were no processes we know of and ,if there were the speed limit would have been c.

 

btw ,did the Inflationary period precede the BB or (as I think ) come after it?

[Genady]

1 hour ago, geordief said:

did the Inflationary period precede the BB or (as I think ) come after it?

Preceded. The BB starts with an almost uniform, hot, dense, expanding state. Inflation is a brief "prequel" (how Alan Guth calls it) that dynamically creates the BB's initial conditions.

[geordief]

3 minutes ago, Genady said:

Preceded. The BB starts with an almost uniform, hot, dense, expanding state. Inflation is a brief "prequel" (how Alan Guth calls it) that dynamically creates the BB's initial conditions.

What does the oft repeated T^-43 seconds refer to ? From when Inflation started?(I always thought it was the start of BB)

 

Was ,perhaps the duration of Inflation too short for any processes to occur?

[Genady]

5 minutes ago, geordief said:

What does the oft repeated T^-43 seconds refer to ?

After the "singularity", a point on the time axis where the scale factor would be zero.

 

6 minutes ago, geordief said:

From when Inflation started?

There is only a low estimate for its duration. It could be as long as eternity as well.

PS. If it was at all.

[geordief]

17 minutes ago, Genady said:

After the "singularity", a point on the time axis where the scale factor would be zero

So btw the "singularity" and the supposed beginning of Inflation  there is a gap of T^-43 seconds that we know nothing of?

 

And we have no idea what might have been going in during Inflation apart from the extreme stretching of  distances in a very short time? (viewed from another frame of reference?)

[Genady]

8 minutes ago, geordief said:

So btw the "singularity" and the supposed beginning of Inflation  there is a gap of T^-43 seconds that we know nothing of?

 

And we have no idea what might have been going in during Inflation apart from the extreme stretching of  distances in a very short time? (viewed from another frame of reference?)

This is correct AFAIK. Alternatively, one could say that we have tons of different ideas, which is also a problem.

[geordief]

9 minutes ago, Genady said:

This is correct AFAIK. Alternatively, one could say that we have tons of different ideas, which is also a problem.

To gain the general acceptance which I assumed it had, the Inflation model  must have made some (or an) experimentally confirmed prediction(s).

 

Was it the observed homogeneity of today  that  has made it the leading theory?

[Genady]

1 minute ago, geordief said:

To gain the general acceptance which I assumed it had, the Inflation model  must have made some (or an) experimentally confirmed prediction(s).

 

Was it the observed homogeneity of today  that  has made it the leading theory?

No, it was not a prediction. Homogeneity was an assumption long before the inflation idea. Inflation retrospectively explains it. It also retrospectively explains flatness, small non-uniformities, the absence of magnetic monopoles, and the power spectrum of CMB, IIRC.

I am not aware of any experimentally confirmed predictions of it.

[geordief]

3 minutes ago, Genady said:

No, it was not a prediction. Homogeneity was an assumption long before the inflation idea. Inflation retrospectively explains it. It also retrospectively explains flatness, small non-uniformities, the absence of magnetic monopoles, and the power spectrum of CMB, IIRC.

I am not aware of any experimentally confirmed predictions of it.

Yes I should have written "retrospectively explains" 

 

I am in no position to either  question or accept the validity of Inflation,of course

[Mordred]

24 minutes ago, Genady said:

No, it was not a prediction. Homogeneity was an assumption long before the inflation idea. Inflation retrospectively explains it. It also retrospectively explains flatness, small non-uniformities, the absence of magnetic monopoles, and the power spectrum of CMB, IIRC.

I am not aware of any experimentally confirmed predictions of it.

Afiak which is extensive with regards to BBN and inflation all pieces of evidence for inflation are indirect in so far as predicting the correct metalicity with regards to the CMB. Hydrogen, lithium, deuterium etc. We simply cannot see far enough due to the dark ages prior to recombination

[Markus Hanke]

On 5/8/2023 at 5:33 PM, geordief said:

To gain the general acceptance which I assumed it had

I think the best way to put it is that the idea of inflation is widely favoured within the cosmology community, but by no means generally accepted. There are in fact serious and unresolved problems with the notion - the two main ones being that 1) you need extremely specific initial conditions to make it work in the way we want it to, and 2) the inflaton field needed for this process is difficult or impossible to reconcile with the rest of the Standard Model, and there is no evidence whatsoever for its existence. Furthermore, there are very many possible inflation models, and selecting the 'right' one essentially boils down to an ad-hoc selection of the values of certain parameters. Once you do those things then yes, it produces results that match closely to what we observe...but the whole thing feels very ad-hoc.

I'm generally very much of a mainstream guy, but this is one area I am quite uncomfortable with. Just my own personal opinion.

[Mordred]

4 hours ago, Markus Hanke said:

I think the best way to put it is that the idea of inflation is widely favoured within the cosmology community, but by no means generally accepted. There are in fact serious and unresolved problems with the notion - the two main ones being that 1) you need extremely specific initial conditions to make it work in the way we want it to, and 2) the inflaton field needed for this process is difficult or impossible to reconcile with the rest of the Standard Model, and there is no evidence whatsoever for its existence. Furthermore, there are very many possible inflation models, and selecting the 'right' one essentially boils down to an ad-hoc selection of the values of certain parameters. Once you do those things then yes, it produces results that match closely to what we observe...but the whole thing feels very ad-hoc.

I'm generally very much of a mainstream guy, but this is one area I am quite uncomfortable with. Just my own personal opinion.

I too had issues with the inflaton or using any of the quasi particles such as the curvaton (Coleman) etc. However the Higgs inflation models produce the same scalar equation of state as the inflaton so as such has been gaining a wide spread popularity including Inflationary Encyclopedadia which examines the most likely Inflationary models for best fit.

 I also found a couple of papers from Alen Guth who has also switched to Higgs inflation from the inflaton. .

 I decided to examine how the equation of state for Higgs was derived as well as its Breit Weigner cross sections, Saha equation and Bose Einstein statistics to further examine the feasibility. The formulas I have posted on the thread I have in the BB nucleosynthesis thread in Speculations. As I rarely take any papers on verbatim. I couldn't find any reason to doubt the feasibility not yet anyways lol. The Higgs inflation model can produce a number of E-folds in the required range to satisfy observation data.

 When one considers the kinetic energy terms vs the potential energy terms via the scalar field equations of state along with the critical density associations it becomes readily apparent that the initial conditions are ripe for an Inflationary expansion.

However despite my personal research that is still just my opinion on the topic lmao. Regardless the Higgs inflation model has become my personal choice as to the most likely of the inflation models.

 

[MigL]

IIRC, A Guth's initial inflation model came in the 80s, right after Electroweak unification, and originally used theHiggs mechanism due to symmetry break, and drop from false zero point energy to account for inflation.
I still have his book, somewhere.

The problems without inflation are much greater than those introduced by inflation.
How do you account for isotropy and homogeneity unless, at some point, the universe was small enough for information to travel across it and establish an equilibrium , ie causal contact ?
That is impossible if the universe expanded linearly from a smaller size; only an exponential size increase makes sense.

The Planck era is at 10^-43; before that period quantum foam without geometry would have prevailed, and that is considered to be the start of the Big Bang.
According to A Guth's initial conjecture ,inflation would have been caused by Electroweak dissociation, and the energies involved would put this at about 10^-35 to 10^-32 sec .

Edited May 10, 2023 by MigL

[geordief]

14 minutes ago, MigL said:

 

The problems without inflation are much greater than those introduced by inflation.
How do you account for isotropy and homogeneity unless, at some point, the universe was small enough for information to travel across it and establish an equilibrium , ie causal contact ?
That is impossible if the universe expanded linearly from a smaller size; only an exponential size increase makes sense.

The Planck era is at 10^-43; before that period quantum foam without geometry would have prevailed, and that is considered to be the start of the Big Bang.
According to A Guth's initial conjecture ,inflation would have been caused by Electroweak dissociation, and the energies involved would put this at about 10^-35 to 10^-32 sec .

Can I deduce from (my bolded in your quote) that the maximum speed (of  information  transfer et al) during the proposed inflationary  period would have been c?

Edited May 10, 2023 by geordief

[MigL]

Correct.
Before Elecroweak dissociation, electrons/neutrinos/quarks and W/Z bosons hadn't aquired mass yet; everything moved at c .

[Mordred]

1 hour ago, MigL said:

 

The problems without inflation are much greater than those introduced by inflation.
How do you account for isotropy and homogeneity unless, at some point, the universe was small enough for information to travel across it and establish an equilibrium , ie causal contact ?
That is impossible if the universe expanded linearly from a smaller size; only an exponential size increase makes sense.

 

The small size made prior to inflation made any anistropy trivial even any plausible curvature would be trivial. Your time frames above for symmetry break are within estimated values. I had a copy of his original paper on inflation. Might still have it in my archives he did at one time utilize the inflaton. May have changed it when he published his book.

Prior to thr symmetry breaking one can accurately describe the universe via its temperature exclusively with the volume as all particles were in thermal equilibrium. So would only need the Bose Einstein statistics to calculate the number density of photons. This doesn't mean photons were the only particle but rather one couldn't distinguish any particular particle species at this point in time.

Edited May 10, 2023 by Mordred

[Genady]

1 hour ago, MigL said:

Correct.
Before Elecroweak dissociation, electrons/neutrinos/quarks and W/Z bosons hadn't aquired mass yet; everything moved at c .

Yes, I've read it before, but I still try to understand the meaning of it. If everything moved with c, relative to what did everything move?

[Mordred]

1 hour ago, Genady said:

Yes, I've read it before, but I still try to understand the meaning of it. If everything moved with c, relative to what did everything move?

In the FLRW metric they use what's called a fundamental observer. That is in essence an observer situated on the global mean average Mass potential.

This link has a half decent explanation 

https://people.ast.cam.ac.uk/~pettini/Intro Cosmology/Lecture01.pdf

Edited May 10, 2023 by Mordred

[Genady]

25 minutes ago, Mordred said:

In the FLRW metric they use what's called a fundamental observer. That is in essence an observer situated on the global mean average Mass potential.

This link has a half decent explanation 

https://people.ast.cam.ac.uk/~pettini/Intro Cosmology/Lecture01.pdf

P.1 defines:

Quote

An observer at rest with respect to the substratum is a fundamental observer

However, we are in the situation where the substratum moves with c. Thus, there is no observer at rest with respect to it. How do we fix this?

[Mordred]

Ask yourself is any object in the universe today or then truly at rest. Under GR all observers are inertial. Under SR the observer is always considered at rest even if they are in actuality in motion.

  The fundamental problem with that is velocity c isn't considered a valid inertial reference frame. 

 It's a very good question that may be a point where relativity breaks down to not being useful.

[Genady]

54 minutes ago, Mordred said:

Ask yourself is any object in the universe today or then truly at rest. Under GR all observers are inertial. Under SR the observer is always considered at rest even if they are in actuality in motion.

  The fundamental problem with that is velocity c isn't considered a valid inertial reference frame. 

 It's a very good question that may be a point where relativity breaks down to not being useful.

I got the solution, relativity is safe. Phew . 

The answer, by MTW, is "a three-dimensional spacelike hypersurface of homogeneity and isotropy." At each event on such hypersurface, the density, pressure, and curvature are the same, and the radiation is isotropic. The fundamental observer is an observer at rest relative to such hypersurface. His worldline is orthogonal to the hypersurface.

So, everything else can be moving with c relative to this observer with no problem.

[Mordred]

Glad you found a workable solution. That solution works well for me. Lol you had me really thinking on that one. It's definitely a scenario I really hadn't thought of before tbh.

Edited May 10, 2023 by Mordred

[MigL]

Maybe I should have just left it as "all particles were massless during the radiation era", and avoided the confusion.

Two other problems 'solved' by inflation, the horizon and the flatness problems.
PBS SpaceTime does a better job of explaining these issues than I could.
With graphics even.

 

[Mordred]

7 minutes ago, MigL said:

Maybe I should have just left it as "all particles were massless during the radiation era", and avoided the confusion.

Nah in this case it brought up an interesting thought experiment.

[geordief]

Did the fact that there were no massive particles  contribute to the speed of inflation?

 

It seems intuitively like it should..