Big Bang Theory and Matter

John15

How does the BB theory allow for the creation of matter. Bt this I mean the sub atomic particles that make up atoms i.e. the quarks and electrons. From what I have read it seems to assume that they already pre-existed and condensed out of the fireball to form atoms.

bapowell

The big bang model does not address the origin of matter/energy in the universe.

phinds

There was no actual fireBALL.

"Big Bang" really mean two different things

(1) the singularity / t=0 / the "big bang event" --- this is the place where our theories totally break down and current science has no idea what happened here.

(2) The evolution of the universe starting one Plank Time AFTER the singularity. At this starting point, the universe was WAY more dense and hot than it is now, although that does NOT imply that it was finite. Lots of stuff happened. Over time, energy coalesced into matter. I commend to your reading "The First Three Minutes" by Weinberg.

zhermes

Regardless of the `big-band model' per se, the idea is that the energy density in the early universe was high enough for spontaneous creation of particles. If you're familiar with electron-positron annihilation to produce 2 photons, then you won't be surprised that the opposite can happen---if two photons have enough energy, they will react to form an electron and positron pair. The same type of thing can happen with all particles. This topic is referred to as leptogenesis and baryogenesis (for leptons and baryons respectively), which both focus on how/why 'normal' particles dominate over anti-matter particles---still an unresolved issue.

bapowell

Right, but this has nothing necessarily to do with the origin of energy in the universe; after all, these are vacuum fluctuations -- virtual particles. How do you suppose they become real? Now, particle production via changing gravitational fields and expansion is a real phenomenon, and might be relevant to the origin of matter. In fact, one can invoke this kind of particle creation to (sort of) reheat the universe after inflation. But you still need to start with a gravitational field for this to work....
In what way are you saying that the processes of lepto- and baryogenesis are related to vacuum fluctuations? They are the mechanisms by which particles come to dominate over antiparticles, as you say, but this usually done through out-of-equilibrium, beyond-the-standard model particle interactions.

zhermes

I agree, this has nothing to do with the origin of energy, in general, I supposed the existence of energy density, and tried to motivate how it can become equipartitioned with matter. As soon as there is energy, it's not just vacuum fluctuations and virtual particles.

I'm not. You brought up vacuum fluctuations :)

I wasn't talking about virtual particle production (i.e. vacuum fluctuations) at all, just boring old particle physics.

bapowell

I see. My confusion then was over your statement regarding the spontaneous creation of particles but I see now that you were referring to real particles. My apologies for misreading your post.

Mark M

Hi John,

The original big bang theory formulated by Lemaitre and Friedman did indeed assert that all of the matter had being compressed into a singularity, but today we've improved upon this.

The standard model of the origin of the universe is known as inflation. In very simple terms, inflation speculates that the universe is filled with an inflaton field. This field would have been at a very high energy at the beginning of the universe, violently fluctuating between different values. Eventually, it would fall down into a false vacuum. In order to reach a true vacuum, it would need to exert a huge force, resulting in an enormous negative pressure. In general relativity, negative pressures result in repulsive gravity, expanding the universe by a factor near 100¹⁰⁰, for about 10^-35 seconds.

Now, imagine a car trying to drive, but it is held back by an extraordinarily tense rubber band. As it continued to try to break free, it would pass it's energy to the rubber band holding it in place. Similarly, imagine a rocket trying to escape from a huge gravitational field. The gravity would build up huge amounts of energy.

During inflation, something similar happened with gravity. It built up enormous emounts of energy, and then at the end of inflation, dumped large amounts of energy into the universe. Since energy and mass are related through E=mc², we know this energy would eventually manifest as matter.

Chalnoth

The general picture goes as follows:

1. Our universe, at very early times, was incredibly, unbelievably hot (as in hotter than the temperatures available in the collisions at the LHC). This extremely high temperature meant that particles were continuously colliding with one another, producing new matter/anti-matter particle pairs. So the universe was this giant jumble of matter and anti-matter.
2. One or more of the heavier particles that existed at this time tended to decay just a little bit more into matter than anti-matter. This meant that at very early times, there was a teeny tiny bit more matter than anti-matter (around one part in a billion, if memory serves).
3. As our universe cooled, the matter and anti-matter annihilated, eventually leaving behind the tiny excess of normal matter that built up when our universe was much hotter.

Please understand that step (2) here is not currently known in detail. If we're lucky, the LHC will shed some light on this issue.

John15

A couple of points regarding answers.
Mark if gravity was involved at the start then at the singularity it would have been infinite re black holes so how could anything escape?.
Regarding baryogenisis 1 billion antimatter + 1 billion and 1 matter = 2 billion and 1 universes coming out of the BB (2 billion anhilated) that is a lot to come out of a singularity.
The obvious other question is is it reasonable to think that all that temperature and energy spontainiously came into being.
Has anyone ever tried to create matter out of energy, we create energy from matter in neuclear reactions but is it possible to reverse the process?

bapowell

Exactly. Trying to understand the physics of the singularity invariably leads to nonsense. For this reason singularities are not to be interpreted physically -- they instead signify the breakdown or inapplicability of the physical theory.
Why are you associating single matter/antimatter particles with entire universes? There is a single universe, and early on there was a tiny asymmetry between matter and antimatter within that single universe. That's all.
These ideas are not addressed under the standard hot big bang model. This model considers instead the evolution of the universe from about the Planck time onwards.

marcus

Brian, you bring up a very interesting point---particle realization via changing geometry to give it a sloppy paraphrase.

Did you happen to see this paper of Leonard Parker and a PhD student of his named Ivan Agullo? If so I'd really like to know what you think about it. There's an earlier more technical account in Physical Review D, but this is their essay for wider audience:

http://arxiv.org/abs/1106.4240
Stimulated creation of quanta during inflation and the observable universe
Ivan Agullo, Leonard Parker
(Submitted on 21 Jun 2011)
Inflation provides a natural mechanism to account for the origin of cosmic structures. The generation of primordial inhomogeneities during inflation can be understood via the spontaneous creation of quanta from the vacuum. We show that when the corresponding stimulated creation of quanta is considered, the characteristics of the state of the universe at the onset of inflation are not diluted by the inflationary expansion and can be imprinted in the spectrum of primordial inhomogeneities. The non-gaussianities (particularly in the so-called squeezed configuration) in the cosmic microwave background and galaxy distribution can then tell us about the state of the universe that existed at the time when quantum field theory in curved spacetime first emerged as a plausible effective theory.
Comments: Awarded with the First Prize in the Gravity Research Foundation Essay Competition 2011

We're familiar with other cases where geometric circumstances create real (not virtual) particles e.g. Hawking radiation at BH horizon and Unruh radiation caused by acceleration or felt by an accelerated observer. So it seems that expansion of geometry itself, especially inflation, can produce matter. And Leonard Parker seems to consider this significant.

Ivan Agullo is giving an invited talk about this next week at the Atlanta APS meeting. So I'm kind of excited and would be interested if you have a comment.

bapowell

Thanks Marcus. I will happily check it out. You mention that
I would also agree that it is significant, and it is the generally accepted way that primordial perturbations arise (although, history kind of confuses things here...in the early investigations of Parker, Ford, Fulling, Davies, and others, the phenomenon was termed "cosmological particle production", but in recent parlance we talk about the generation of "fluctuations" instead of particles, but the formalism and physical mechanisms at work are identical.) The evolution of quantum fluctuations, from their birth in the inflationary vacuum and their subsequent journey out to superhorizon scales where they become real life perturbations, is perhaps my favorite calculation in physics.

Mark M

Singularity is a mathematical anomaly, not meant to be taken literally. The universe was very hot, and very dense, that is all we know.

DaveC426913

His point is that, since that tiny imbalance has resulted in the entire universe we see today, then the original amounts of both matter and antimatter before mutual annihilation must have been staggeringly large.

i.e. if the imbalance was on the order of 1/100th of a %, and that left behind a universe of 10⁶⁰ particles, then the original number of particles must have been 2x10⁶⁴.

Chalnoth

If I recall, this can be directly calculated, in a way, through the relationship between matter energy density and radiation energy density (since the energy from all those annihilations would have been dumped into radiation). I believe the true imbalance was of the order of one part in a billion.

marcus

Thanks for commenting! As you point out this topic goes back a ways (Parker's thesis Harvard 1966) But there could also be something new! I'll fetch the abstract of Agullo's talk:
http://meetings.aps.org/Meeting/APR12/Event/170160
Beyond the standard inflationary paradigm
The inflationary paradigm provides a compelling argument to account for the origin of the cosmic inhomogeneities that we observe in the CMB and galaxy distribution. In this talk we introduce a completion of the inflationary paradigm from a (loop) quantum gravity point of view, by addressing gravitational issues that have been open both for the background geometry and perturbations. These include a quantum gravity treatment of the Planck regime from which inflation arises, and a clarification of what the trans-Planckian problems are and what they are not. In addition, this approach provides examples of effects that may have observational implications, that may provide a window to test the basic quantum gravity principles employed here.
=========
This abstract leaves me puzzled. But the same research is the subject of a recorded online talk by William Nelson. It's about a paper by Ashtekar, Agullo, Nelson that has not come out yet. It uses the Parker and Agullo results about *stimulated* fluctuations. I get the impression their idea is that inflation does not wipe the slate clean. Somehow earlier inhomogeneities might come through. So I'm puzzled, but also excited by what I'm hearing about.: