Mass in the early universe and the CCC model

[windy miller]

Penrose's CCC model posits a mapping between our big bang and a future one. This is based on the idea than in the far future there will be no mass and at the big bang there was no mass. So in both cases the universe looses track of scale. I am aware that the idea of there being no mass in the far future is a controversial one. But what about the no mass at the big bang, is Penrose on firmer ground there? is that the consensus view?

 

[phinds]

Penrose's CCC model posits a mapping between our big bang and a future one. This is based on the idea than in the far future there will be no mass and at the big bang there was no mass. So in both cases the universe looses track of scale. I am aware that the idea of there being no mass in the far future is a controversial one. But what about the no mass at the big bang, is Penrose on firmer ground there? is that the consensus view?

The "big bang" you refer to is, I assume, what is sometimes called the "big bang singularity", which is just a placeholder name for the phrase "the place where the math model breaks down and we have no idea WHAT is/was going on". The singularity is not part of the Big Bang Theory.

 

[windy miller]

The "big bang" you refer to is, I assume, what is sometimes called the "big bang singularity", which is just a placeholder name for the phrase "the place where the math model breaks down and we have no idea WHAT is/was going on". The singularity is not part of the Big Bang Theory.

Well as I understand it the singularity implies the temperature is infinite. But if we assume there is no singularity then its at least very hot. What Penrose claims is that at sufficiently hot temperatures there can't be any mass and that is what I am asking about.

 

[phinds]

Well as I understand it the singularity implies the temperature is infinite. But if we assume there is no singularity then its at least very hot. What Penrose claims is that at sufficiently hot temperatures there can't be any mass and that is what I am asking about.

No, the singularity does not imply the temperature is infinite, it implies that we don't know WHAT is going on and anything else is speculation. That's what "singularity" means --- the math says weird things that are not to be taken as indications of physical reality.

I think it is correct, however, that at sufficiently high temperatures, everything is energy, not mass.

 

[Arman777]

But what about the no mass at the big bang, is Penrose on firmer ground there? is that the consensus view?

Where did you find that he says such thing ?

 

[Arman777]

He claims that in the infinite future particles will loose their "mass" due to some sort of reverse higgs mechanicsm, but it doesn't imply there will be no mass in the early universe.

 

[George Jones]

Where did you find that he says such thing ?

Penrose has highly speculative ideas.

From section 3.1 "Connecting with infinity" of Penrose's book "Cycles of Time" :

But in the very early universe, when the temperature was so high as to have provided energies greatly in excess of this Higgs value, all particles would then, according to standard ideas, indeed have become effectively massless, like a photon. Massless particles, as we may recall from section 2.3, do not appear to be particularly concerned with the full metric nature of space-time, respecting only its conformal (or null-cone) structure.. ... Maxwell theory is indeed conformally invariant in this strong sense. ... Moreover, exactly the same invariance holds for the Yang-Mill equations that are considered to govern not only the strong interactions ... but also the weak interactions ... Thus, according to standard theory, when that mass-providing ingredient (Higgs mechanism) is removed, at the extremely high temperatures back near the Big Bang ... then full conformal invariance should be restored.Of course, the details of this depend upon our standard theories of these interactions being appropriate ...

 

[Buzz Bloom]

I think it is correct, however, that at sufficiently high temperatures, everything is energy, not mass.

Hi phinds:

I am not sure I understand what this is intended to mean. I would interpret this literally as saying the are no particles which have mass. What is left then? Is it, for example, just photons and gluons? (I recall reading a thread recently that said gluons have no mass.) If this is so, what prevents quarks from being created by all the extremely energetic photons (and maybe also the gluons)?

Another interpretation might be that the ratio of mass density to energy density in the mix is so extremely small that it can for all calculation purposes be assumed to be zero. This of course makes sense with respect to the Friedmann equation.

As a gets very small, Ω_R overwhelmingly dominates the other Ωs, and 1-Ω_R << 1.

Regards,
Buzz

 

[PeterDonis]

I would interpret this literally as saying the are no particles which have mass.

That's true, but ordinary language is ambiguous, so you have to be careful in interpreting what it means.

It means: all of the Standard Model particles (actually quantum fields) are present, but their rest masses are all zero.

It does not mean: the Standard Model particles (fields) don't exist.

 

[phinds]

I am not sure I understand what this is intended to mean. I would interpret this literally as saying the are no particles which have mass.

I believe I mis-spoke, based on the early universe being dominated by radiation (but not to the exclusion of matter)

 

[PeterDonis]

I believe I mis-spoke, based on the early universe being dominated by radiation

It's dominated by "radiation" in the sense that all of the fields present are highly relativistic--their total energy density is much, much larger than their rest energy density. That's true even after the electroweak phase transition that, according to the current Standard Model, gives the fields that have rest mass (fermions and W and Z bosons) their rest mass. It only stops being true once the temperature drops lower than the rest energies of the fields (heuristically--the actual calculations are more complicated and the transition is not instantaneous, it takes time to go from one regime to the other).

 

[PeterDonis]

That's true even after the electroweak phase transition

Just to clarify: before the EW phase transition, all of the Standard Model fields are massless. That is the regime Penrose is talking about. After the EW phase transition, it is no longer the case that all of the fields are massless, so Penrose's condition does not apply; but the universe is still "radiation dominated" in the sense I described, at least for a while.

 

[windy miller]

So it seems that at least then at the beginning Penrose is right to say that there is no mass in the early universe. So is the argument by him that the singularity can be removed because there isn't any mass (and the Penrose Hawking singularity theorems assume that there is mass) a sound one? It seems like his primary assumption then is correct. Of course that won't prove the CCC model is correct because he has to assume that mass will fade away in the far future which even he admits is speculative. But it would mean there is a classical way to avoid the singularity without needing quantum gravity, wouldn't it?

 

[Drakkith]

So it seems that at least then at the beginning Penrose is right to say that there is no mass in the early universe.

My understanding was that even with massless particles you still have mass when talking about a system of them. A box of photons is not massless even though individual photons are. They still have energy after all. Unfortunately I can't say what Penrose is getting at, as I'm not experienced in this area.

 

[PeterDonis]

is the argument by him that the singularity can be removed because there isn't any mass (and the Penrose Hawking singularity theorems assume that there is mass) a sound one?

As I understand it, that's not the argument Penrose is making, because the Penrose-Hawking singularity theorems don't assume that "there is mass". They assume that the stress-energy tensor has certain properties, which are still satisifed, as far as I can tell, by the SET of the contents of the universe before the electroweak phase transition.

The argument Penrose is making, as I understand it, is that you can change the solution of the EFE that describes the universe from a standard FRW metric to an FRW metric times a conformal factor that can be adjusted in the far past (and far future) of the universe in order to make the solution there no longer meet other conditions of the singularity theorems. As I understand the model--and I have not spent a lot of time digging into the details--he main condition that gets changed is that, if you go sufficiently far in the past, the universe is no longer expanding--or, viewed going backwards in time, it is no longer contracting. So this would look something like a "bounce" cosmology, where the scale factor of the universe never gets down to exactly zero, but just approaches that very closely and then "bounces" back. I'm not sure how he accounts for this in terms of what, physically, causes the bounce (or causes the conformal factor to vary the way he proposes).

 

[windy miller]

My understanding is that it is not a bounce. I think he has spoken against that. I thought of it as the universe before the big bang is actually expanding but when it loses its mass its transforms into a new big bang.