Why Are Neutron-Neutron Interactions Essential for Nuclear Stability?

[Ellispson]

I was recently taught the concept of nuclear forces in school.According to what was taught,nuclear forces were introduced to explain the stability of the nucleus.So,my question is that,can't we say that the nucleus is stable only due to neutron-proton and proton-proton interactions?Why are neutron-neutron interactions necessary?

 

[Orodruin]

The same theory which is used to describe the proton-proton interactions also predicts the proton-neutron as well as the neutron-neutron interaction. In fact, it would be unnatural if it did not. It would be like having a theory of electromagnetism where positive charges interacted with themselves and with negative charges, but negative charges did not interact with each other. Therefore, the question you should ask yourself should be "why would an interaction which results in proton-proton and proton-neutron interactions not also imply neutron-neutron interactions?"

 

[e.bar.goum]

I was recently taught the concept of nuclear forces in school.According to what was taught,nuclear forces were introduced to explain the stability of the nucleus.So,my question is that,can't we say that the nucleus is stable only due to neutron-proton and proton-proton interactions?Why are neutron-neutron interactions necessary?

The strong nuclear force (or 'strong force') acts equally on neutrons and protons. That is, strong n-p, n-n and p-p interactions are all the same. So, somehow, you'd have to figure out a way for the strong force to treat neutrons and protons differently.

 

[mfb]

"why would an interaction which results in proton-proton and proton-neutron interactions not also imply neutron-neutron interactions?"

And even if you could come up with such a theory, I don't see how it could match experimental data. Models with interactions between all combinations of nucleons fit very well.

 

[ChrisVer]

the total interactions between pp, nn, pn are not necessarily the same.
However as long as you keep isospin as a symmetry, they are. That's why proton and neutron can be considered the same particle (within the concept of strong nuclear forces) : the Nucleon.
As a result it's indeed unnatural to expect something different between pp,nn and np (it's nucleon interacting with nucleon).
The differences that occur are either because of the isospin symmetry breaking or coulomb interactions- and as a result these combinations get distinct.

 

[Ellispson]

And even if you could come up with such a theory, I don't see how it could match experimental data. Models with interactions between all combinations of nucleons fit very well.

Oh oh.Experimental data.Now I guess I understand..Thanks
And could tell me names of a few such experiments?So I can look them up myself..

 

[Ellispson]

the total interactions between pp, nn, pn are not necessarily the same.
However as long as you keep isospin as a symmetry, they are. That's why proton and neutron can be considered the same particle (within the concept of strong nuclear forces) : the Nucleon.
As a result it's indeed unnatural to expect something different between pp,nn and np (it's nucleon interacting with nucleon).
The differences that occur are either because of the isospin symmetry breaking or coulomb interactions- and as a result these combinations get distinct.

Umm what do you mean by isospin?

 

[jtbell]

https://en.wikipedia.org/wiki/Isospin

 

[Ellispson]

https://en.wikipedia.org/wiki/Isospin

Thank you,I did get an overview of what it was..

 

[mfb]

Oh oh.Experimental data.Now I guess I understand..Thanks
And could tell me names of a few such experiments?So I can look them up myself..

Nuclear mass measurements. All of them. Plus all measurements of excited states of nucleons and their energy above the ground level. They fit very well to a model where both types of nucleons interact in (nearly) the same way.

In addition, the strong force that leads to the nuclear force can be studied in high-energetic proton-proton and proton-electron collisions. It can be shown that it acts on all quarks, and both protons and neutrons are made out of those quarks.

Particle physics and nuclear physics would have completely different measurements everywhere if neutrons would not interact with neutrons. There is no single experiment that would be special here.