Big Bang Matter-Antimatter Annihilation

RJ Emery

In as few words as possible, could someone refresh my memory as to why in the Big Bang there was a slight excess of matter that survived the matter-antimatter annihilation?

And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?

hellfire

It is usually assumed that some conditions during baryogenesis lead to this asymmetry. These are known as Sakharov conditions. I cannot expand on this, but only provide you the link to wikipedia: Sakharov conditions.

Baryon asymmetry is the one that has to be explained due to observations. After annihilation a rest of baryons survived and a lot of photons were created. The photon to baryon ratio is about 10⁹. These photons are currently in the cosmic microwave background. For other particle families such as leptons or non-baryonic dark matter the abundances of particles and antiparticles might be equal.

bapowell

As hellfire mentions, the matter/antimatter asymmetry arose during conditions after the big bang. The conditions that would need to exist in order to generate a matter/antimatter asymmetry are known as the Sakharov conditions. In brief, these conditions include particle physics processes that favor matter to antimatter and/or a lack of thermal equilibrium between processes that turn matter into antimatter and processes that turn antimatter into matter. The matter/antimatter asymmetry is seen not only in baryons but also leptons (electrons, neutrinos, etc). It is unknown whether the asymmetry originated in the baryonic sector (and transferred, via interactions) to the leptonic sector or vice versa.

sleinad

The elementry pair particle formation is well documented. The remainder of the answer is like most cosmological theories is speculative. It is my way of responding to the question that makes the most sense to me. I have seen other speculations that posit the existance of the positron as traveling into the past sleinad

BillSaltLake

It would be sufficient if the only matter-over-antimatter excess was of neutrons (although it is not known whether this is the way it actully happened). One excess neutron per ~billion photons would lead to what we see now. The reason for the excess is still not known.

bapowell

You are mistaken. A positron is mathematically equivalent to an electron traveling into the past.

akbmurugan

However, is the expectation to have equal matter and antimatter is hypothetical or a well proven necessity?

BillSaltLake

There is no known mechanism by which the observed imbalance should result. It would be "nice" if an experiment could be done, but it's extraordinarily difficult to replicate conditions at t = 1 microsec. Even if a blackbody cavity at those temperatures could be produced, the walls of the container would destroy many more antiparticles than the signal we would be looking for, causing a false "verification".

sleinad

I would have to say that to say that is the natural state of things. When energy is transformed to matter half the energy become an elementary particle of matter and the other half becomes an elementary particle of anti-matter. Balance is always maintained. That includes equal amounts of matter and anti-matter and, it also maintains the equality of the time associated with the newly formed matter.
As far as expectations are concerned, nothing in cosmology can be lab tested......sleinad

bapowell

Quite the contrary. In cosmology, the universe itself becomes your laboratory. Granted, one does not have the luxury of repeated, controlled experiments. But that's what Bayesian statistics is for. Cosmologists might not be claiming detections at 5 sigma like the particle physics community, but don't be fooled: cosmology is a rigorous science with a sophisticated statistical methodology. We know a tremendous amount about the early universe.

twofish-quant

No one is quite sure. Antimatter/matter asymmetry comes out of some grand unified theories of particle physics, but even then, it looks like someone just added in by hand rather than something nature.

We do know that whatever happened happened before fusion or else elemental abundances would be off. We also know that whatever happened, happened at energies higher than the current particle accelerators, or else we would have seen something at CERN.

We also have lots of limits as to how much antimatter there could be in the observable universe without anyone noticing.

Positrons

sleinad

Thank you for that very interesting response.
In meditating on your response, it has just come to my attention that if you follow the initial energy to matter transformation, no matter what theory you believe in, an elementary particle of matter is always accompanied by it’s antiparticle at transformation. This is the way it always occurs in laboratory particle accelerators. Every particle of matter in our universe had to be transformed in the same manner.
There must be a cosmic balance sheet. In every transformation, every elementary particle is accompanied by it’s antiparticle, every charge is accompanied by it’s opposite and, that must follow for time also since, it is also part of the transformation. If there is such a balance sheet, then, that balance should also operate for annihilations.
Such a balance would not permit any asymmetry to exist between matter and antimatter.
Thank you bapowell for bringing this to my attention.....sleinad

bapowell

Yes, but it is supposed that such a balance sheet is not honored by certain particle interactions. The idea is that grand unified theories include interactions for which particles are not always accompanied by their antiparticle. If these interactions were operative in the early universe before the grand unified symmetry was broken, a matter/anti-matter asymmetry could be generated.

BillSaltLake

It is possible to create two neutrons (= total baryon number of 2) from a system with zero initial baryon number (e.g., an equal # of neutrons & antineutrons, etc.).

sleinad

Is there really a reliable GUT model? I have a hard time accepting data from theories whose interactions cannot be verified. The composition of the present universe has been computed from data gathered by the space telescope. Only 4%of it consists of normal matter with only 1/10 (0.4%) of that total being visible matter like our sun. Most of that, 3.6% consists of is interstellar gas more complex than hydrogen with only 1/10 of that existing as elements more complex than hydrogen. The remainder of the universe is supposedly 73% dark energy and 23% dark matter.
Before the beginning, the universe must have consisted of a limitless space which was evenly permeated with dark energy. After the beginning until now, the universe went from 100% dark energy to the it’s present diversity.
How did the original consistency of the universe get transformed to that of the present? The present distribution does suggest the route that the transformation had to take. First some of the dark energy is transformed into dark matter. This continues until the density of the dark matter reaches a point where some of it can actually interact and be transformed into composite particle of visible matter. This type of step transformation does not suggest something sudden like a Big Bang which would seem to bypass the dark matter stage. What it does suggest, is a slow gradual type of transformation.
Sorry bapowell it takes me more time to extract logical responses these days. Some of data are extracted from ana article previously published in another science forum and which I have just published as a new thread in this forun. It is called “Micro-pops not Big Bang”. You might be interested to seem how I have presented some of my deductions which I do not swear that are completely correct. I am now working on an updated version that tries to bring these deductions up to date relative to the responses I have had.....sleinad

bapowell

Statements like this require substantiation. As it stands, it is pure speculation and against forum rules.

It is good that you are interested in gaining an understanding of the working of the universe, however, this is not the place to present your ideas. We discuss mainstream science here at PF.

sleinad

quote by bapowell
We discuss mainstream science here at PF.

Response
I was so happy that I thought I had been having discusssions with individual in the ionosperic region of the scientific world. Sorry that I have strayed into the lower mainstream regions.....sleinad