Pauli Exclusion Force

Hello! A Physics professor once told me that I shouldn't go around saying that matter is solid (i.e. one can't simply pass through a the floor) simply because of the 'electric repulsion' between the electrons from the most outer layer of my skin and those in the floor. Rather, one should explain the issue with 'electron degeneracy pressure' and the Pauli exclusion principle. There is also a 'neutron degeneracy pressure', and thus this is not an EM interaction (i.e. related to the exchange of photons). I do understand that, but my question is, what is the force that balances out my weight (let's say I'm standing still, and thus the overall sum of forces around me must be zero). If it is not an EM interaction then it is not a EM force, and to the best of my understanding it couldn't be gravity, the strong nuclear force, or the weak one. What is the nature of that force then, if it is not one of the fundamental ones? I have googled this question before but I keep finding answers that are not entirely satisfying. Some argue that one can't call that "Pauli interaction" a force in the classical sense, because there is no carrier boson involved on it). Some people also say that you don't need a force to define a pressure in the first place because you can define that 'Pauli pressure' in a more fundamental way as simply the change of energy over a volumne (dU/dV). That makes sense but leaves me with a bitter aftertaste because my weight is totally 'real' (right?), and thus there must be another 'real' force canceling it out ... or have I reached a bad limit of my intuition? I hope someone can solve this mini-existential crisis of mine. Best wishes, Eddy
- Eddy (age 23)
Urbana, Illinois, US

The saying "...you can define that 'Pauli pressure' in a more fundamental way as simply the change of energy over a volume (dU/dV) " is right on the button, except for a missing minus sign. In fact, along exactly the same lines you can go ahead and define the Pauli force as -dU/dh, where h is the height of (say) the bottom of your shoe. And this force is plenty real!

Mike W.

p.s. Great question!

(published on 01/24/2017)