Pauli Exclusion — Fermi Gas

Fermi-Dirac statistics: quantum state occupancy at finite temperature
f(E) = 1 / (e(E−μ)/kBT + 1)  ·  E_F = (ℏ²/2m)(3π²n)^(2/3)

Gas Parameters

T/T_F = 0.050
N = 20

Fermi Gas Properties

Fermi energy E_F
Chemical potential μ
Temperature T
Thermal smearing 4k_BT
Average energy ⟨E⟩/E_F
Zero-pt pressure P₀

The Pauli exclusion principle forbids two fermions from occupying the same quantum state. At T=0, electrons fill all states up to the Fermi energy E_F — a sharp step function. As temperature increases, states are thermally excited above E_F while states below E_F are vacated, smearing the distribution over a range ~4k_BT. Even at T=0, the Fermi gas has non-zero kinetic energy (zero-point pressure), which stabilizes white dwarf stars against gravitational collapse.