Why does the Pauli exclusion principle create pressure in white dwarfs?

[EricLG]

I’ve been trying to wrap my head around how the Pauli exclusion principle actually prevents two fermions from occupying the same quantum state. My confusion comes from picturing it in a practical scenario, like in a white dwarf star where electron degeneracy pressure is what stops gravitational collapse. I don’t quite get how the prohibition on identical states translates into that macroscopic outward pressure.

[JasonG]

I tried a tiny box model with a handful of fermions. When I crammed more particles in, they kept occupying higher momentum states because the same state can’t be shared. That raised their average kinetic energy, so the simulated pressure went up even without any temperature change.

[Eric63]

In a white dwarf sense, electrons fill up to a Fermi level at essentially zero temperature. Gravity pushes the system to squeeze, so electrons have to jump to higher momenta. The pressure you feel is not from collisions, but from the quantum statistics forcing the occupancy of higher energy levels.

[Kenneth.G]

So is the punchline that the antisymmetric wavefunction makes identical particles avoid the same quantum numbers, and that constraint shows up as a rising energy when you compress, which we call degeneracy pressure?

[Chloe_W]

I remember building a lecture demo and someone said it’s like trying to fit more people in a room than there are chairs, but then you realize the chairs correspond to momentum states, not spots. We laughed, then realized it didn’t fully capture gravity pulling it all together.