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Pauli exclusion in the declared finite-mode occupation readout, with the bosonic contrast
The conditional exclusion statement of the declared finite-mode occupation model: in the adopted antisymmetric sector of P6 the joint occupation law is supported on configurations of occupations at most one, so the probability of reading two particles in one declared mode is zero in every declared sector preparation, while in the symmetric sector every occupation configuration of total n occurs. The statement is conditional on the declared sector and the finite-mode idealization; it asserts no measured occupancy, no apparatus claim and no derivation of a species' statistics.
Statement
Adopt the observable and probability postulate P2 (Observable and probability postulate P2: self-adjoint observables, spectral probability and finite unsharp outcomes) and the identical-particle and spin postulate P6 (Identical-particle and spin assignments P6: permutation sectors and finite-spin representations) in the readings of Declared species sectors and their preparations: the framework's reading of P6 and The declared finite-mode model and its occupation readouts, and assume the Axiom of Countable Choice and the Axiom of Choice (The Axiom of Countable Choice (), The Axiom of Choice). Declare a finite-mode model as in The declared finite-mode model and its occupation readouts with declared modes , particles and statistics choice , with sector space , occupation readouts , joint projections and joint law . Then for every declared sector preparation :
(a) fermionic exclusion: if , then and the joint law is supported on the occupation configurations with entries in :
(b) no restriction in the symmetric sector: if , then for every the projection is nonzero, and for the pure declared sector preparation of the ray of the joint law gives weight one to ; in particular for and any the configuration with occurs;
(c) total occupation: in either sector , so the total occupation has the degenerate law and every outcome of the joint readout satisfies .
The exclusion in (a) is a conditional consequence of the adopted antisymmetric sector and of the declared finite-mode readout; the theorem asserts no measured occupancy, no detector behaviour and no derivation of the statistics of any species.
Facts & Assumptions
Given: A declared finite-mode model with modes, particles, statistics choice , sector space, occupation readouts, joint projections and a declared sector preparation .
Sector readouts. is -dimensional with orthonormal basis ; the operators of the occupation theorem are bounded self-adjoint, commute pairwise, satisfy and preserve both sector spaces, with and , and the joint eigenspaces inside are the lines (indexed by -element subsets , eigenvalue vector ) and inside the lines (indexed by , eigenvalue vector ) (Slater and symmetric occupation-number bases of the finite-dimensional permutation sectors clauses (b)-(d), The declared finite-mode model and its occupation readouts clauses (c)-(d)).
Observable reading. An assigned sharp observable has a unique spectral projection-valued measure and the outcome law ; if a projection-valued measure satisfies , then (Assigned sharp observables and the outcome law of the framework clauses (a),(b), Observable and probability postulate P2: self-adjoint observables, spectral probability and finite unsharp outcomes).
Joint projectors. In the declared finite-mode model, the finite family consists of mutually orthogonal projections, sums to the identity of the sector, and satisfies (The declared finite-mode model and its occupation readouts clause (d)).
Laws and traces. For a preparation and projections with the numbers are nonnegative and sum to one; a pure preparation of the unit ray of a vector gives weight to an orthogonal projection (Density operators and scalar spectral probability clauses (a),(b), The state space of the framework: preparations, pure rays and density operators).
Configuration counts. No fermionic configuration has an entry ; for the antisymmetric sector is ; every is a bosonic configuration, including the configuration with for any (Finite-mode occupation configurations: fermionic exclusion counts, bosonic counts and truncated dimensions clauses (a),(c)).
Proof
Given: The data of the statement and [F1]-[F5].
[Sector restrictions are self-adjoint] By [F1] the operator preserves , and both the Slater family and the family consist of eigenvectors of with real eigenvalues and form a basis of the respective sector; a linear endomorphism of a finite-dimensional Hilbert space that is diagonal in an orthogonal basis with real eigenvalues is self-adjoint. Hence each is a bounded self-adjoint endomorphism of , which is the readout declared in clauses (c)-(d) of the model.
[Finite spectral measures and laws] Fix and . By [F3], the finite family of projections is a projection-valued measure: and because the sum to ; each is an orthogonal projection; intersections satisfy because the are mutually orthogonal; and countable additivity is strong since only finitely many occur and the Borel sets in a disjoint sequence contain each eigenvalue at most once. Its scalar measures are finite and supported on the finite set , hence regular: for every Borel , the compact set and an open set with give . Its spectral integral is the finite sum Thus is the spectral PVM of by uniqueness of the spectral PVM in [F2]. The outcome law in is therefore . In the fermionic sector [F1] restricts the joint eigenvalue vectors to , so this spectral measure is supported on ; in the symmetric sector it groups the lines by the value . This identifies the readout laws of clauses (c)-(d) of the model.
[Exclusion] Assume . By step 2.1 the spectral measure of is supported on , so and ; moreover on the sector because the operator vanishes on the Slater basis by [F1], so its expectation is zero. For the joint law, [F1] shows that the joint eigenspaces with an entry do not occur among the lines , so the sum of the corresponding projections is zero and . This proves (a).
[Bosonic contrast] Assume . For every the vector is nonzero and spans the joint eigenspace for by [F1], so ; for the pure preparation of the ray of the weight is for any unit representative of that ray by [F4]. By [F5] the configurations with lie in , so they occur; this proves (b).
[Total occupation] By [F1] one has on the whole tensor power, hence on the sector, and therefore ; since the total occupation is the constant operator , its outcome law assigns probability one to in every preparation, and applying the joint law of [F1] gives for every configuration of the support; this is (c).
[Assembly and scope] Step 3.1 proves (a), step 3.2 proves (b) and step 3.3 proves (c). The proof is conditional on the declared sector of P6, the declared finite-mode readout and the cited spectral mathematics; no measured occupancy, no apparatus behaviour and no derivation of a species' statistics is asserted.
Remarks
- The precise content of "exclusion". The theorem states the vanishing of the probability of reading an occupation in each declared mode and the vanishing of the expectation of the double-occupation operator ; it is a statement about the declared readout in every declared sector preparation, not a statement about particles avoiding each other in space.
- Finite modes. The statement uses the finite-dimensional mode model of the definition; the counting facts for the index sets are those of the finite-mode count theorem. No infinite mode family and no continuum occupancy is treated.
Depends on
The declared finite-mode model and its occupation readouts
Declared species sectors and their preparations: the framework's reading of P6
Assigned sharp observables and the outcome law of the framework
Slater and symmetric occupation-number bases of the finite-dimensional permutation sectors
Finite-mode occupation configurations: fermionic exclusion counts, bosonic counts and truncated dimensions
Density operators and scalar spectral probability
The state space of the framework: preparations, pure rays and density operators
The state space: density operators, pure and mixed states, and purity
Observable and probability postulate P2: self-adjoint observables, spectral probability and finite unsharp outcomes
Identical-particle and spin assignments P6: permutation sectors and finite-spin representations
The Hilbert orthogonal projection onto a closed subspace
The Axiom of Countable Choice ()
The Axiom of Choice
Dependency tree · 2 levels
Sources
- J. Binney and D. Skinner, The Physics of Quantum Mechanics, Section 10.1.1 printed pages 227-228 (PDF pages 235-236): antisymmetry of the fermion pair wavefunction and the Pauli exclusion principle, with the vanishing amplitude for a repeated single-particle state
- F. H. L. Essler, Advanced Quantum Theory (Oxford lecture notes, 2017/18), Chapter 1 Sections 1.2-1.3 pp. 5-9: occupation-number states with fermionic occupations in {0,1} and no such restriction for bosons