When you try to put two electrons or neutrons close together (e.g. in a white dwarf or a neutron star), these spin-$\frac{1}{2}$ particles, by the Fermi principle, tend to push each other apart.

For the electrons the quantum field involved is the one for electrons, which happens to carry charge, but degeneracy pressure is not an electric repulsion, but a quantum-mechanical effect of two particles not wanting to be in the same state.

So we cannot say it's the electromagnetic force pushing them apart. But it sure looks force-like, but it's not one of the four fundamental forces that's responsible.

I'm confused. What's going on here?

  • $\begingroup$ Okay, thanks for the pointer -- should have found it myself! It's similar enough, and the answer there is good. $\endgroup$
    – Travis Lee
    Aug 23, 2018 at 8:05