Confinement and particles

The idea that fundamental fields are just that, fields and not particles, runs into a problem at some point. If I pick up a tennis ball and bounces it a few times then I am basically handling a particle. So, somewhere between the tiny scales of fundamental physics and the larger scales of everyday life, particles need to appear.

If the fundamental fields are just fields interacting at points, then any combinations of such field would still be fields, even though they may be interacting with one another. No, particles! Then there would also not be atoms consisting of nuclei and electron bound to them in different orbitals.

So, at some point, or some scale, a transition needs to happen where particles are created. How would that happen? It seems that if there are no fundamental particles, the universe would be condemned to exist as a soup of fields at all scales.

Then it occurred to me that there is a process that may be able to introduce particles. Confinement to the rescue! The highly nonlinear dynamics of the strong force, which is modeled by quantum chromodynamics (QCD) is believed to introduce a special scale (the QCD scale) where the force becomes so strong that it confines itself to regions with a restricted volume. The size of this volume is believed to determine the size of protons and neutrons.

Proton model (with fundamental particles), from Desy

So, although the fundamental fields are just fields with no particles, the mechanism of confinement may be responsible for adding particles in our universe. As a result, the constituents of the nucleus of the atom are particles in the true sense of the word. The nuclei can now act as the sources of the potentials that bind the electrons to form atoms.

If confinement is the reason why we have real particles in this universe, then the process of confinement is very important. The funny thing is that it is not yet a solved problem in theoretical physics. In fact, there is an outstanding Millennium Problem of the Clay Mathematics Institute about the mass gap in Yang-Mills theories, which is related to the problem of confinement. Perhaps it is something that theoreticians in fundamental physics can focus on.

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