In quantum mechanics, a Slater determinant is an expression that describes the wavefunction of a multi-fermionic system that satisfies anti-symmetry requirements and consequently the Pauli exclusion principle by changing sign upon exchange of fermions. It is named for its discoverer, John C. Slater, who published Slater determinants as a means of ensuring the antisymmetry of a wave function through the use of matrices. The Slater determinant arises from the consideration of a wave function for a collection of electrons, each with a wave function known as the spin-orbital, where denotes the position and spin of the singular electron. Two electrons within the same spin orbital result in no wave function.