Pauli Exclusion Principle
The Pauli exclusion principle, stated by Wolfgang Pauli in 1925, holds that no two identical fermions can occupy the same quantum state simultaneously.
The standard account
Pauli arrived at the rule empirically, as the condition needed to explain why electrons in an atom do not all collapse into the lowest orbit and why the periodic table has the shell structure it has. Its modern form is more general: the total wave function of a system of identical fermions — particles of half-integer Spin such as the Electron, Proton and Neutron — must be antisymmetric under exchange of any two of them, which makes the amplitude for two of them sharing a state vanish identically. Bosons, of integer spin, obey the opposite rule and may share states freely. Pauli himself proved the spin–statistics theorem in 1940, deriving the connection between spin and exchange symmetry from relativistic quantum field theory.
The consequences are structural rather than subtle. Chemistry exists because electrons must stack into successive shells. Ordinary matter resists compression because of degeneracy pressure, which is not electrostatic repulsion but a direct consequence of exclusion. White dwarfs are held up by electron degeneracy pressure, with the Chandrasekhar limit of about 1.4 solar masses marking where it fails; neutron stars are held up by the neutron equivalent.
A point often glossed over in teaching, and worth stating plainly: the exclusion principle is a statement about the symmetry of the wave function, not a force. There is no "exclusion force" in the Hamiltonian. Whether that constitutes a mechanism or merely a rule is the question the alternatives here press on.
On this wiki
- Wladimir Guglinski's Mechanism for Pauli's Exclusion Principle argues that the principle is a consequence of aether participation in the equilibrium of the electron cloud — that Bohr and his successors analysed that equilibrium without accounting for contraction of the medium — and further argues that the quantum-mechanical atom cannot account for diamagnetism.
- Robert A Close derives both the Lorentz force and the exclusion principle from wave interference in his classical bispinor reading of the Dirac Equation; see A Dirac Equation.
- Joseph C Lucas and Charles William Lucas treat electron pairing in Pauli Pairs and Strong Nuclear Force in Terms of 3rd Millenium Physics and in A Model for Free and Pauli-Paired Electrons, within the Common Sense Science ring-particle framework.
- Magic Numbers Derivation from Variable Phase Nuclear Model attempts to recover nuclear shell closures — a direct consequence of exclusion in the standard account — from an alternative model.
- Rati Ram Sharma, Yi-Fang Chang and others in Category:Quantum Theory and Category:Atomic Structure address the principle from further directions.
The common thread is dissatisfaction with a principle that organises the whole of chemistry while remaining, in the standard formulation, a symmetry postulate rather than a physical mechanism. Any replacement, however, has to reproduce the periodic table, degeneracy pressure and the nuclear magic numbers.