Pauli Exclusion Principle and its theoretical foundation

TL;DR

This paper critically examines the theoretical foundations of the Pauli Exclusion Principle, questioning the common proofs and arguing that only symmetric and antisymmetric wave functions are physically realizable, thus limiting elementary particles to fermions and bosons.

Contribution

It challenges the traditional proof of the symmetrization postulate, showing that other permutation symmetries lead to contradictions, and argues that only nondegenerate permutation states are physically possible.

Findings

Proofs in textbooks claiming only symmetric and antisymmetric states exist are incorrect.

Permitting arbitrary permutation symmetry leads to contradictions with particle identity.

Only fermions and bosons are expected to be discovered as elementary particles.

Abstract

The modern state of the Pauli Exclusion Principle (PEP) is discussed. PEP can be considered from two viewpoints. On the one hand, it asserts that particles with half-integer spin (fermions) are described by antisymmetric wave functions, and particles with integer spin (bosons) are described by symmetric wave functions. This is the so-called spin-statistics connection (SSC). As we will discuss, the physical reasons why SSC exists are still unknown. On the other hand, according to PEP, the permutation symmetry of the total wave functions can be only of two types: symmetric or antisymmetric, both belong to one-dimensional representations of the permutation group, all other types of permutation symmetry are forbidden; whereas the solution of the Schr\"odinger equation may have any permutation symmetry. It is demonstrated that the proof in some widespread textbooks on quantum mechanics that only symmetric and antisymmetric states (one-dimensional representations of the permutation group) can exist is wrong. However, the scenarios, in which an arbitrary permutation symmetry (degenerate permutation states) is permitted lead to contradictions with the concepts of particle identity and their independence. Thus, the existence in our nature particles only in nondegenerate permutation states (symmetric and antisymmetric) is not accidental and so-called symmetrization postulate may not be considered as a postulate, since all other symmetry options for the total wave function may not be realized. From this an important conclusion follows: we may not expect that in future some unknown elementary particles can be discovered that are not fermions or bosons.