In high school, I learnt that the strong force held the nucleus together. It had a very short range and was repulsive at small separation distances to prevent the nucleons from collapsing.

Now I am doing a course on nuclear physics and I have realised that the strong force acts on quarks too.

Suppose the strong force becomes repulsive at a critical separation $r_c$.Then the first question I thought was this:

The strong force is repulsive between nucleons separated by a distance $r$ with $r<r_c$. I expect that the distance between quarks within a nucleon is smaller than the value of $r_c$. So why does the strong force not result in the quarks repelling and cause a complete disintegration of the nucleon?

And that is my question.


1 Answer 1


There is some confusion here between the strong nuclear force , and the strong force as modeled in particle physics with quantum chromodynamics.

The nuclear force is a spill over force from the bound states of the protons and neutrons in the nucleus. See this article to get a feeling for description of a proton ( also all hadrons). Quantum chromodynamics which models the strong force and binds the quarks, and the sea of quarks and antiquarks by the gluons is the standard model for protons and neutrons.

The spill over strong force is similar to the spill over electromagnetic force from neutral atoms that builds up solids into lattices. It builds the periodic table.

The strong nuclear force is not repulsive, the repulsive component comes from the charge of the protons which is positive and repulsive and a bit from the Pauli exclusion principle which does not allow two same fermions to occupy the same energy level. It is all about quantum mechanics at this level, and simplistic models of distances fail.

The range of the strong force is within the size of a nucleus. The range of the strong nuclear force is larger, as it needs at least two nucleons to be expressed. Here is another link for the colored strong force that is full of links.


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