No Imbalance between Matter/AntiMatter

[NebulaBilly]

Hi i have a problem/question. If there was a universal exactly the same as ours where there was no Imbalance between matter/antimatter at what time would baryons disappear and also at what time would the last scattering of photons occur?

I understand that if there is no imbalance then matter/antimatter would just keep colliding and also that the last scattering occurred when the matter was fully ionized. But i can not figure out this question, any help would be great.

 

[fresh_42]

Can you phrase this question a bit clearer? There are so many IFs, that it will be impossible to answer, if you don't define your assumptions and questions better. E.g. do you assume two separated universes, if not, what do you need the balance for? Don't you just asked what the annihilation processes which actually occurred?

 

[NebulaBilly]

Can you phrase this question a bit clearer? There are so many IFs, that it will be impossible to answer, if you don't define your assumptions and questions better. E.g. do you assume two separated universes, if not, what do you need the balance for? Don't you just asked what the annihilation processes which actually occurred?

Fresh 42, The question I pose is how I read it, if I was to try and make it clearer the only word I really missed out was Imagine. So Imagine there was a universe exactly the same as ours but there was no imbalance between matter/antimatter. What time would baryons Disappear and What time would the last scatter of photons occur.

I mentioned the annihilation processes purely based on my own knowledge of if there was no imbalance of matter/antimatter then this would occur continuously until the universe expanded enough, this I understand, I do not however think it answers the question of what time would baryons disappear and the last scattering occur.

 

[kimbyd]

Hi i have a problem/question. If there was a universal exactly the same as ours where there was no Imbalance between matter/antimatter at what time would baryons disappear and also at what time would the last scattering of photons occur?

I understand that if there is no imbalance then matter/antimatter would just keep colliding and also that the last scattering occurred when the matter was fully ionized. But i can not figure out this question, any help would be great.

If there was no Baryon imbalance, the physics in the early universe would be extremely different.

First, nearly all of the normal matter would annihilate, and the remaining gas would be exceedingly diffuse. Thus the surface of last scattering would very likely have occurred close to the time at which electrons became non-relativistic, which would have been, very roughly, at around a billion Kelvin or so. That's roughly a million times the temperature at which the CMB was emitted, and would have happened within the first few minutes of the Big Bang. Protons would have gone non-relativistic at temperatures a thousand times greater, and would already be pretty much gone by this point.

Presumably, there would be some frame of time where not enough of the electrons had annihilated to impede the travel of photons, but eventually they would almost all annihilate.

 

[NebulaBilly]

Hi Kimbyd, i appreciate your answer thanks for helping out in my discussion. Yes that is correct, if there was a balance, the universe would not be here, and it is also fascinating that nobody as of yet can explain how matter and anti matter became imbalanced.

 

[kimbyd]

Hi Kimbyd, i appreciate your answer thanks for helping out in my discussion. Yes that is correct, if there was a balance, the universe would not be here, and it is also fascinating that nobody as of yet can explain how matter and anti matter became imbalanced.

Saying that nobody can explain it is slightly misleading. We do know that the mechanism must rely upon something which is known as "CP violation". CP violation happens if a particle decays into a group of particles where the sum of their charge/parity values is not equal to the parent particle. This kind of thing can occur with weak nuclear force interactions, but happens too rarely to explain the observed imbalance. Thus, the focus is on understanding higher-energy physics which produces a greater degree of CP violation than is observed in weak interactions.

 

[NebulaBilly]

Saying that nobody can explain it is slightly misleading.

My apologises i did not mean to mislead anyone

 

[kimbyd]

My apologises i did not mean to mislead anyone

You're good. I just wanted to clarify the point, which is a common misconception. Typically even when scientists aren't entirely sure of what's going on, they still know a lot about the situation.