Why Is Our Universe Primarily Matter and Not Antimatter?

[Zoe-b]

I have done a large amount of research (but being only an A level standard physicist probably not understood a lot of it) into antimatter, and why our universe is made primarily of matter and not antimatter... I think I've bitten off more than I can chew in a way as I seem to find myself trying to explain an awful lot of particle physics along the way.

What I'm after is: An easily understandable explanation of CPT theorem (I have searched the internet and read more than one textbook, but still don't really understand how it would result in asymmetry). If anyone has a link to a good website on the subject hat would be very welcome!

Also if anyone knows of any stranger ideas about matter-antimatter asymmetry, I am looking to include these in my research. (Again a weblink is just as useful). I'm sure I've read about something to do with string theory (or maybe branes??) and antimatter but can't find the book it was in. So far I've written about CPT violation (badly, I fear) and a little about baryon violation.

Thanks in advance,
Zoe

 

[Jhero]

Hello Zoe,

Thank you for sharing your interest in antimatter and the search for explanations for the matter-antimatter asymmetry in our universe. I can understand your struggle with trying to explain complex concepts in a simple and understandable manner.

Firstly, let's start with the CPT theorem. CPT stands for Charge-Parity-Time and it is a fundamental principle in physics that states that the laws of physics should be the same for particles and their antiparticles when charge, parity (a measure of spatial symmetry), and time are all reversed. This means that if we were to take a snapshot of a physical process and reverse the direction of time, switch the charges of all particles involved, and flip the orientation of the system, the process should still behave the same. This principle has been tested and verified in many experiments.

Now, the question is, how does this relate to the matter-antimatter asymmetry in our universe? Well, according to the Big Bang theory, the universe was created with equal amounts of matter and antimatter. However, as the universe cooled and expanded, matter and antimatter particles started to annihilate each other, leaving behind a small amount of matter that we see today. This process is known as baryogenesis.

One possible explanation for this asymmetry is through CPT violation. If the CPT theorem is not perfectly true, then there could be a slight difference in the behavior of matter and antimatter particles, leading to the excess of matter in our universe. However, this is still a theoretical concept and has not been definitively proven.

There are also other theories that attempt to explain the matter-antimatter asymmetry, such as baryon number violation and the role of neutrinos in the early universe. As for the connection to string theory, there are some ideas within the theory that suggest the possibility of CPT violation, but again, this is still a topic of ongoing research.

I hope this helps to clarify the concept of CPT theorem and its potential role in explaining the matter-antimatter asymmetry. As for further reading, I recommend checking out the following resources:

- CERN's explanation of CPT theorem: https://home.cern/science/physics/matter-antimatter-asymmetry
- A comprehensive review of the matter-antimatter asymmetry problem: https://arxiv.org/abs/0801.0905
- A discussion on