How does the Big Bang Theory explain the creation of matter from energy?

[Naty1]

bapowell:

..All spacetimes have a particle horizon, on account of the finite speed of light.

Based on post #29, you and Chalnoth seem to agree on that, but he says:

And just to be clear, if we're talking about particle creation, we're talking about an event horizon specifically.

which suggests something unique. What does that added 'qualifiation' imply...Does the Hubble sphere meet that criteria??

I checked Wikipedia and it says:

The particle horizon is the maximum distance from which particles could have traveled to the observer in the age of the universe

and that sounds correct, right?? but I don't know if the current Hubble Sphere meets all your requirements??

I'll have to reread this thread tomorrow because something is bugging me: It seems like when I am sitting 'still', say at a great distance from a black hole, pretty much inertial rather than strongly accelerating I assume, here on earth, I don't detect particle creation...let's call it Hawking radiation [I'm talking theoretical here, not practical detection]. . But when I get close and accelerate to keep just outside that horizon, now I supposedly get irradiated to death, almost instantaneously...loads of radiation appears with strong acceleration...but NOT if I am inertial there [free falling] so somehow acceleration seems to affect a particle horizon in some way so as to stimulate particle creation...to increase radiation. Are 'accelerated' particle horizons much closer??..smaller?? than 'cosmological'...that would fit the inverse temperature to area relationship of a black hole, for example...In a given spacetime, does increased acceleration bring in 'particle horizons' real close?? And that's what Unruh effect does to: accelerate right next to an inertial observer, and voila, I have 'created' particles in the form of radiation...

If so, such effects would seem to be another reason no mass can never reach light speed: we'd be irradiated to death!

 

[bapowell]

Can you site sources on that?

Almost any GR textbook should talk about this; it has to do with the lack of a globally defined sense of time in general relativity (since the Hamiltonian generates time translations). See also: http://www.scientificamerican.com/article.cfm?id=is-the-universe-leaking-energy

 

[bapowell]

I am not so sure: if appropriate conditions [ such as the cosmological energy density during the period of expansion, that roughly 10^-35 seconds] remained constant...

and I was also alluding back to Marcus post #12...

Yes, this is sort of a complicated issue. It is true that any particles hanging around at the start of inflation were most certainly redshifted away, exponentially diluted by inflation. However, it's not this simple, because if there are particles present at the start of inflation, then the fluctuations are not born in the vacuum as per the standard density perturbation calculation. If the initial state was thermal rather than vacuum (known as the Bunch-Davies vacuum), then the perturbations are affected; in particular, power is suppressed on large scales (see http://arxiv.org/abs/hep-ph/0508070). Non-vacuum initial states can also generate non-Gaussian temperature fluctuations: http://arxiv.org/abs/0710.1302.

Now, the reference that Marcus linked to is to my knowledge rather novel, having to do with the stimulated generation of quanta during inflation on account of the presence of particles at the beginning. So, even though the original particles are redshifted away, their presence induces measurable effects on the evolution of perturbations.

If the negative gravitational pressure of inflation 'got stuck' briefly on an energy plateau, why not other factors conducive to particle production..like,maybe, virtual particles of the vacuum??...antimatter?? were NOT diluted...

The virtual particles are not diluted because they are continuously being created!

Glad you mentioned that; I am unsure of the implications and have been rather unsuccessful so far in distinguishing between different 'horizons' and different spacetimes effects on particle production... Unruh, de Sitter, Rindler,etc, have me confused because of apparently different 'accelerations'...

Indeed it's a zoo. One important distinction is that the de Sitter horizon is fundamental to the spacetime, while the Rindler horizon is observer dependent.

 

[bapowell]

Based on post #29, you and Chalnoth seem to agree on that, but he says:
which suggests something unique. What does that added 'qualifiation' imply...Does the Hubble sphere meet that criteria??

Good catch, and it's an important one. I set up the case where the wavelength of the Fourier mode is larger than the particle horizon, and I chose this horizon because it marks the limit of causal separation. Now, in non-accelerating spacetimes, what happens? The Fourier mode increases in length less quickly than the particle horizon -- if it was once superhorizon, it eventually falls into the horizon: hardly a prescription for particle creation! What we need is to not only push the modes out of the particle horizon, we need to keep them out!. This can only be done if the horizon is shrinking in comoving units, i.e. an accelerating spacetime. In this case, we have an event horizon as well, and this is key to ensuring that the once the fluctuation becomes acausal, it will remain so, becoming a real quantum. So, I admit I didn't give you the full story! All spacetimes have a particle horizon, and this distance is important for determining whether the fluctuation becomes acausal; but we also need an event horizon to ensure that it stays that way! Of course, inflation does eventually end, and so this event horizon does eventually go away. This is key to enabling the real perturbations to eventually re-enter the horizon as I described above. Once inside the horizon, causality is restored to these perturbation and they can begin to evolve into the rich assortment of galaxy clusters, and clusters of clusters, that we observe today.

I checked Wikipedia and it says:
and that sounds correct, right?? but I don't know if the current Hubble Sphere meets all your requirements??

During inflation, the Hubble sphere effectively satisfies all criteria. During slow roll inflation, in particular, the Hubble sphere and the event horizon are almost coincident, making any distinction between them, especially over the long course of inflation, unimportant.

 

[Chalnoth]

I checked Wikipedia and it says:

The particle horizon is the maximum distance from which particles could have traveled to the observer in the age of the universe

and that sounds correct, right?? but I don't know if the current Hubble Sphere meets all your requirements??

Yes, this is correct. So no, the current Hubble Sphere does not work here, because particles beyond the horizon can never arrive, meaning that it depends upon the entire future expansion.

 

[Naty1]

This has been a great discussion...I appreciate the feedback; have some reading to do...
[but only after I get some ground prepared and grass seed spread to calm my wife...]
bapowell:

Indeed it's a zoo. One important distinction is that the de Sitter horizon is fundamental to the spacetime, while the Rindler horizon is observer dependent

oboy, that is a helpful insight...it confirms part of my own source difficulty sorting the aspects 'accelerating particle production' out: Between space and time and energy not having global definitions in GR, different models having different assumptions and how they approximate the real universe, what is coordinate dependent and what isn't, and what appears to me to be different kinds of 'acceleration, it is difficult to sort thru...well, very detailed anyway...

Two final questions:

Brian: in your description above, do you distinguish between different 'types' of acceleration and if so how does that affect results and horizons...for example 'local' acceleration versus cosmologicallly accelerated [Hubble type] expansion...'local' versus 'global'...Do we have to pick particular models to understand different types??

These posts, just posted, seem contradictory...are they?:

Chalnoth:

...So no, the current Hubble Sphere does not work here, because particles beyond the horizon can never arrive, meaning that it depends upon the entire future expansion.

bapowell:

...the Hubble sphere effectively satisfies all criteria...

And any related insights into 'entire future' and 'entire past' would be appreciated. Is there terminology that applies ..like maybe 'causality' ...so I could read more...I get in a general sense how that would relate to the Hubble sphere , I think, since the 'Hubble constant' isn't really constant over time...the expansion rate has varied...and I have read that Unruh radiation 'takes time' to develop...is such a feature of all the situations [spacetimes and models]...

 

[Naty1]

john15 posts:

do we know what quarks are made of? do they have mass or are they just energy? From what I understand singly they decay rapidly yet in groups of 3 they basicaly make up the protons and neutrons and protons seem to be virtually eternal, I have found it strange that they should decay rapidly when single yet be stable in 3's. Presumably they were all created in the early stages.
It is strange that certain things like electrons are stable and others not, is there a reason why certain configurations are stable and others not?

Here is a rough overview...enough for some perspective if not an up to date detailed answer:
lots of science there...lots not fully understood...In general I think more energetic fundamental particles are likely to decay faster...that is, have shorter liftimes...
I don't know what QM says about the 'configuration', if anything, about fundamental particles...supposedly they have no finer material structure...but we have been fooled about that many times before with regard to other particles...like atoms, neutrons and protons...I'm guessing it's related at least in part to phase space and real and imaginary components in QM...yes, here is some stuff, but I don't know the details of quantum mechanics on this issue:

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

You can also check out 'Standard Model' of particle physics...a hodge podge [grouping] of all our generally accepted ideas about all particles...relativistic QM included.

The heaviest...highest energy...fundamental particles don't exist in everyday elements around us but have been briefly observed in high energy colliders...and so they are taken to have likely existed shortly after [or maybe during] the big bang.,.in that high energy but unstable environment...

Apparently the high energy [theoretical so far, never observed] Higgs field back then went thru a phase transition to a lower energy level and consequently lost symmetry...so everything began to 'precipiate' out...radiation, particles, and so forth. Space and time existed at that point. The particles that first appeared were really high energy and subsequenetly disappeared... and yet the vacuum expectation value..and virtual particles...remain today...go figure! So the Higgs field, or its remnants, are present throughout the universe...

from Brian Greene's FABRIC OF THE COSMOS: [beginning pg 251]

... The process of a Higgs field assuming a non zero value throughout space...is called spontaneous symmetry breaking...it interacts with quarks and electrons...and resists their ACCELERATIONS...[its] what gives an object its inertia...The Higgs field resists only ACCELERATED motion...The Higgs field gives fundamental particles their mass...but when these particles combine into composite particles like protons, neutrons and atoms, other sources of mass come into play...the variety of masses [result because]...different particles interact more or less strongly with the Higgs field...Above 10¹⁵ degrees when the Higgs field had yet to condense, not only were all species of fundamental particles massless, but without the resistive drag of the Higgs field, all force particles were massless as well.,...all particles were essentially identical... the electromagnetic force and the weak nuclear force, responsible for radioactive decay, appear so different in the world around us ..because the underlying symmetry..is obscured by the non-zero Higgs field...the vacuum, nothingness, plays a central role in making things appear as they do...

Capitalized 'ACCELERATION' is mine:
I never before associated the Higgs mechanism [it's current affect on the mass of particles via acceleration] and the acceleration of Big Bang, de Sitter space, and all the rest we have been discussing here. What a 'coincidence' !

 

[alexg]

Above 10¹⁵ degrees when the Higgs field had yet to condense, not only were all species of fundamental particles massless, but without the resistive drag of the Higgs field, all force particles were massless as well.,...all particles were essentially identical...

If the fundamental particles were massless, doesn't that imply they were moving at c?

 

[Naty1]

If the fundamental particles were massless, doesn't that imply they were moving at c?

yes, that is what 'radiation' does!

 

[alexg]

yes, that is what 'radiation' does!

Alpha radiation doesn't. Neither does Beta particles.

But we're talking about fundamental particles being massless before the Higgs field. If they suddenly acquire mass, they must instantly drop below the speed of light.

 

[bapowell]

Brian: in your description above, do you distinguish between different 'types' of acceleration and if so how does that affect results and horizons...for example 'local' acceleration versus cosmologicallly accelerated [Hubble type] expansion...'local' versus 'global'...Do we have to pick particular models to understand different types??

Yeah, I guess that's a fine way to look at it. Observers who are locally accelerating are Rindler observers; these guys measure an Unruh temperature. They are distinct from observers who are locally at rest in an accelerating spacetime; these guys measure a de Sitter temperature.

These posts, just posted, seem contradictory...are they?

I think we need to be clear on what we mean by "satisfy requirements" -- I have a feeling Chalnoth and I have different things in mind. My statement was that during inflation (especially slow roll inflation), the Hubble radius and the event horizon can be more or less taken to coincide. The actual distinction turns out to be of no practical importance, because the calculation of the primordial power spectrum requires that fluctuations are evaluated in the long wavelength limit: $k/aH \rightarrow 0$. So the fluctuation is born in the inflationary vacuum and is evolved out to superhorizon scales where it becomes a classical perturbation (this transition is formally identical to the gravitational production of particles, and constitutes the de Sitter temperature). So, the actual calculation is concerned with the perturbation when it is way outside both the event horizon and the Hubble radius, making distinguishing between them unimportant. As a computational approximation that's very good during slow roll, often people simply evaluate the fluctuation at horizon (Hubble radius) crossing (when $k=aH$) rather than following it all the way out to the long wavelength limit (this is OK because during slow roll the amplitude of the fluctuations really does freeze in). Implicit in this calculation is that an event horizon exists (somewhere between the Hubble radius and the long wavelength limit) which it certainly does during inflation; but exactly where it is is not particularly relevant to the calculation. It only significantly differs from the Hubble radius as inflation is ending; during inflation it probably differs by terms of order the slow roll parameters ($\sim \dot{H}/H^2$), but I've not worked this out. You can see that during de Sitter expansion, they exactly coincide.

 

[Naty1]

Originally Posted by Naty1

yes, that is what 'radiation' does!

Alpha radiation doesn't. Neither does Beta particles.

At 10¹⁵ degrees they 'do'...and before that there is yet another Higgs type field...even hotter...

 

[Naty1]

bapowell...great insights...thanks...

Happy Easter to all...

 

[John15]

Lots of interesting disscussion but it still leaves me no further forward.
Mass and energy are equivalent. Energy as I understand it is massless ripples through spacetime. How do you get from massless ripples to say an electron. If the BB theory is correct then all that could be there to start is massless energy.

 

[John15]

Have looked at particle decay on wiki. No mention of quarks.
Why does a neutron decay when on its own and not when part of an atomic neucleus?

 

[Chalnoth]

Have looked at particle decay on wiki. No mention of quarks.
Why does a neutron decay when on its own and not when part of an atomic neucleus?

Because a proton, electron, and neutrino/anti-neutrino pair is a lower-energy state than a neutron.

 

[Mark M]

Lots of interesting disscussion but it still leaves me no further forward.
Mass and energy are equivalent. Energy as I understand it is massless ripples through spacetime. How do you get from massless ripples to say an electron. If the BB theory is correct then all that could be there to start is massless energy.

Particle pair production. Particles of radiation, called photons, can emit a particle, and an anti-particle. Through the processes of baryogenesis and leptogenesis, matter gained a slight edge over anti-matter resulting in a stew of particles.