PX284 - L2 - pauli exclusion principle

|ψ⟩=|ϕ⟩|ϕ⟩P^12|ψ⟩=−|ψ⟩|ϕ⟩|ϕ⟩=−|ϕ⟩|ϕ⟩|ϕ⟩|ϕ⟩=0
pauli exclusion principle

two identical fermions cannot coexist in the same quantum state