> short version is that the Pauli exclusion principle forbids fermions I'd like to point out (for others following along) that the Pauli exclusion principle is

> short version is that the Pauli exclusion principle forbids fermions I'd like to point out (for others following along) that the Pauli exclusion principle isn't actually a separate rule (That is, something you'd have to apply after you do 'normal' physics). What is happening with the PEP is that if you start off with a wavefunction that has fermionic symmetry (that is, interchange of two particle swaps the sign of the wavefunction), the evolution via the Schroedinger equation will preserve that (much like it preserves the Integral(|psi|^2)=1 relation). Same for bosons. So if you're writing a Quantum physics simulator, you don't need to put in a "Pauli Exclusion Rule" step.[1] [1] Though depending on your representation you may toss one in for numerical stability.