I have a question: can the mechanism behind Pauli's exclusion principle be considered a fundamental force, like gravitational, electromagnetic, nuclear weak or strong? Why?
No, it's a fundamental restriction on the states that are available. Calling it a force would be like saying there's some force that pushes a particle into states with integer angular momentum. Same thing - states with integer angular momentum simply happen to be the only ones available!I have a question: can the mechanism behind Pauli's exclusion principle be considered a fundamental force, like gravitational, electromagnetic, nuclear weak or strong?
I suspect it may be, as I think Dyson first showed, that solidity is in fact a result of the Pauli Exclusion principle. Since many of the forces that occur in the everyday world are reaction forces due to this solidity in a sense it could be considered a fundamental force.No. Are you thinking of degeneracy pressure?
I think a tricky thing about it is that from a bottom up approach they certainly look different as they arise from different things, as was already mentioned in this thread. However, from a top down approach, looking at the effects of them they look very much the same.I suspect it may be, as I think Dyson first showed, that solidity is in fact a result of the Pauli Exclusion principle. Since many of the forces that occur in the everyday world are reaction forces due to this solidity in a sense it could be considered a fundamental force.
I don't agree with that view, but understand some may look at it that way.
States are states. How the restriction happens is the mechanics I was asking about.Bill_K said:No, it's a fundamental restriction on the states that are available.
That's probably because fermions' inability to occupy the same quantum state leads to inability to occupy the same space, which sets balance against fundamental forces. And the forces can intuitivelly be understood as reactions toHeavyMetal said:I've seen that question on here before a few times. It has come up relatively frequent. Interesting how everyone keeps coming to that conclusion!
on the states that are available
And forces are forces. You asked if the Pauli exclusion principle can be considered a force, and the answer is no, it cannot.
It's a build-in mechanism.States are states. How the restriction happens is the mechanics I was asking about.
http://en.wikipedia.org/wiki/Electron_magnetic_dipole_momentNo, and therefore
Yes, it stems from the uncertainty principle, if you like. The states always behave like that, but in a classical gas, the states are sparsely populated, so the particle behaviors are not constrained by what the states are doing, if you move around heat. In a degenerate gas, they are, so you have less freedom to move heat around. Yet either way, if you move no heat around, then both the classical and degenerate gases will have their particles follow the changes in their respective states, they follow the behavior of the state they are in-- the state that the particles in are "adiabatic invariants", so adiabatic compression of a degenerate gas is just like adiabatic compression of an ideal gas. Differences between "degeneracy pressure" and "ideal gas pressure" are often overstated.
Neutron has no charge and yet it has magnetic moment. Can you name a particle with 1/2 spin which has no magnetic moment? What other physical property there is to spin beside magnetic moment?Fermions have half-integer spin, but they don't have to have charge so they don't have to have a magnetic dipole moment.
Wouldn't magnetic dipole force between two electrons overcome their electric repulsion if they came close enough together?Moreover, since electrons have charge, they experience electrostatic forces, but that also has nothing to do with the PEP.
http://en.wikipedia.org/wiki/Electron_magnetic_dipole_momentSpin is a purely quantum mechanical property and there is no classical analogue.
They don't repel one another per say. The effect is quite easy to understand. Consider a degenerate Fermi gas e.g. say we have a gas of Fermions and we lower the temperature to ##T = 0##.Anyone? Do paired neutrons repel each other, and if so, is this the basis of degeneracy pressure in neutron stars?