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CP Symmetry: Imperfections Keep The Universe Going

4 Dec, 2020 | Prabin Pyakurel |

CP Symmetry: Imperfections Keep The Universe Going

mirror like example of cp symmetry

CP Symmetry ( Charge Parity and Symmetry Parity) problem is one of the greatest mysteries of physics. The standard model of physics predicts that matter and anti-matter should have annihilated each other until nothing remained. Yet the universe exists in all it’s grandeur as is evident with the first breath you take.

Humans judge beauty by symmetry. Studies show that we judge a person of symmetric face to be better looking than one with less symmetry. Interestingly, the case of CP symmetry is just this human bias entering the scientific world. This is not the first time that such a bias has been made in science. “Einstein’s greatest blunder” is another case of the same bias. Here we look at how chasing a perfection in the universe went wrong and the eventual realization that the universe is imperfect.

Interestingly, annihilation happens when a particle hits an antiparticle or matter vs antimatter war. If you are new to our blog, you can read other articles from here to grasp the concepts used in easy language.

However, this requires the particles and anti-particles to be exact opposites in charge, space (parity), and time. So that when they collide nothing remains but energy. However, in our universe, there is the presence of more matter than anti-matter.


So, is that an error 404?

It gives rise to one of the biggest problem of physics which is still not solved. So, why are you waiting, go and try to solve it? The next Nobel Prize in physics can be all yours. The question is “In Observable Universe, why there is the presence of more matter than anti-matter?”

What exactly is CP Symmetry?

Credits Sandbox Studio Chicago

Let’s see what C P Symmetry is all about in physics. Assume that you take a particle of positive charge, charge symmetry implies as per the laws of physics and there is an anti-particle with a negative charge.

And if our positively charged particle exists then, it must have been produced along with its anti-particle at some point in time.

More interesting thing is here now for CP Symmetry.

Here comes time-reversal symmetry just like CP Symmetry. Combined, it is called CPT Symmetry. Imagine you and your twin got separated in childhood. You remained in present and your brother did time travel and went to future. Now, when your twin brother will try to comeback with a completely opposite feature than you. If you guys crash than you will both get annihilated. There will be no existence of both of you.

Time reversal symmetry implies that a particle will behave the same way when it goes backward in time as it does while going forward. Finally, the particle should behave symmetrically in space which is the parity symmetry.

This whole symmetry can be better understood by taking particles that are opposite in charges like electrons and positrons. These two particles are always produced simultaneously and therefore follow time-reversal symmetry. Electron, being a fermion has the parity +1, and positron will have the symmetrically opposite parity of -1.

Therefore, if every particle has an exact opposite. The standard model is unequivocally true and CP symmetry must exist and in more advanced calling CPT Symmetry. The time symmetry is implied during the mathematics of charge and parity symmetry. So the whole thing is usually called CP symmetry.


Violation of CP Symmetry

In 1964 the Scientists named James W. Cronin and Val Logsdon Fitch proved that electrically neutral particles called K-meson which normally was supposed to be decayed by weak force to transform into particles named mesons (3 in number). However, decayed a fraction of the time into only two such particles. It violated CP symmetry.

particles dust
Particle dust in the Universe (Image for representation only)

Implications on the Universe

This violation can solve the long term mystery of why the observable universe has more matter than antimatter. For, your information and general understanding there can be the presence of another universe parallel to us where time moves backward. You can assume that people will be born old and become young in the future. However, this is only for understanding. Although, the theories like that of the Ekpyrotic Model of the Universe

gives us space to think. It suggests a parallel world must be existing with us which has the opposite character thus balancing CP Symmetry also.

There is another picture in the same coin too. Let’s see what it is for CP Symmetry.

As mentioned in this article, such adherence to the theory would mean the end of the universe also. So, will the CP symmetry violation explain the end of the Universe?

We have a situation where we have made an observation and the theory doesn’t go along with it. When something like this crops up, we acknowledge a problem in the theories and work towards correcting it. However, we do need to know what exactly is wrong with the models. Once we know that, we need something to point towards a solution.

Thankfully, Observation of neutrinos provided just this facility. Scientists came to know that neutrinos don’t follow parity symmetry very well. This means that our perfect charge, parity, and time symmetry laws do not really hold. Therefore, it’s this gap in our theories that makes our theories different from reality. Where our theories predict that nothing should have existed. We have billions of galaxies and exotic phenomena in the universe. Whenever we see this gap we say that it is a CP symmetry violation and this is a puzzle to be solved.

Neutrino Detection: Credits Credit : Asahi Shimbun/Getty

There is something, in the universe, that keeps neutral particles from being identical to their anti-particles. This is the essence of the CP-symmetry problem. The solution to this problem will therefore explain the abundance of matter and thereby the existence of the universe itself or maybe the presence of a parallel world.

More curious? Read about anti-particles or neutrinos from the author.