Baryons.

[NebulaBilly]

I read a interesting article the other day based on the a symmetry between matter and antimatter and how it is the key to the existence of our universe(i have the article link if anybody wishes to read it),It got me thinking what it would be  like it should have after the big bang there was no imbalance between matter and antimatter and i began to wonder at what time would baryons disappear if there was no imbalance, but i have been unable to either think or find no research, or even if there has been any research done. Any thoughts on the subject i would greatly appreciate.

Thanks.

[George Jones]

36 minutes ago, NebulaBilly said:

I read a interesting article the other day based on the a symmetry between matter and antimatter and how it is the key to the existence of our universe(i have the article link if anybody wishes to read it)

I am a little curious about this.

36 minutes ago, NebulaBilly said:

It got me thinking what it would be  like it should have after the big bang there was no imbalance between matter and antimatter and i began to wonder at what time would baryons disappear if there was no imbalance, but i have been unable to either think or find no research, or even if there has been any research done. Any thoughts on the subject i would greatly appreciate.

Ironically, earlier today I was reading about exactly this.

Consider a more a general situation. Let X be a type of particle an X be the corresponding anti-particle. (Dear algebra, Stop asking me to find your X. She/He is not coming back.)

Suppose the universe is symmetric in X and X. In the small, early universe Xs and Xs would be in close proximity, and would be continually annihilating with each other. As the universe expands, eventually the Xs and Xs will thin out to the point that they will no longer be able to find orther, and thus they no longer be able to annihilate with each other. This is called freeze-out. After freeze-out, there will be residual equal numbers of X and X left over. Expansion of the universe from the freeze-out time to the present time will further thin out the  Xs and Xs.

When freeze-out occurs depends on the mass of X. Taking X to be protons and neutrons (with an equal number of anti-protons and anti-neutrons), and running the number gives that the present density of baryons would be a billion times smaller than the density that is actually measured.

[NebulaBilly]

REMOVED

[NebulaBilly]

10 minutes ago, George Jones said:

I am a little curious about this.

Hi George thanks for showing an interest in my topic, the article i was reading can be found here https://arxiv.org/pdf/1801.10059.pdf.

 

So sorry if i am wrong, but what you are saying is In a universe where there is no imbalance of matter and antimatter, then there would be continued collisions until expansion was great enough that they could no longer collide? causing less and less baryons to be present?

[George Jones]

46 minutes ago, NebulaBilly said:

Hi George thanks for showing an interest in my topic, the article i was reading can be found here https://arxiv.org/pdf/1801.10059.pdf.

Thanks.

 

46 minutes ago, NebulaBilly said:

So sorry if i am wrong, but what you are saying is In a universe where there is no imbalance of matter and antimatter, then there would be continued collisions until expansion was great enough that they could no longer collide?

Yes.

 

47 minutes ago, NebulaBilly said:

causing less and less baryons to be present?

After collisions stopped (and assuming that there are not any physical processes that change the number of baryons) there would be a fixed "number" of baryons, but the density of baryons still decreases because the universe continues to expand.

[NebulaBilly]

16 hours ago, George Jones said:

After collisions stopped (and assuming that there are not any physical processes that change the number of baryons) there would be a fixed "number" of baryons, but the density of baryons still decreases because the universe continues to expand.

Thank for this George, it would explain when the baryons would disappear, also if I was to pose another question, still in the same universe with no imbalance, what time would the last scattering of photons be, I can not be as simple as when the earth is no longer hot enough to ionize matter? or maybe it is that simple I am interested in your thoughts. 

[George Jones]

2 hours ago, NebulaBilly said:

if I was to pose another question, still in the same universe with no imbalance, what time would the last scattering of photons be, I can not be as simple as when the earth is no longer hot enough to ionize matter? or maybe it is that simple I am interested in your thoughts. 

Last scattering occurs, roughly, when the early universe is no longer hot enough to ionize matter (more accurately, last scattering occurs slightly later than this). Our baryon-antibaryon imbalanced universe is about 13.7 billion years old, and last scattering happened about 0.0004 billion years after the Big Bang.

I do not know when last scattering occurs in a baryon-antibaryon universe.

[NebulaBilly]

2 hours ago, George Jones said:

I do not know when last scattering occurs in a baryon-antibaryon universe.

It is a tough one, there seem to be no articles on it, and if it would actualyl occur at all in a balanced universe