theorem
proved
boson_symmetric
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IndisputableMonolith.QFT.SpinStatistics on GitHub at line 144.
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141
142/-- **THEOREM (Boson Phase)**: Integer spin particles acquire +1
143 under the full 8-tick cycle (2π rotation). -/
144theorem boson_symmetric (s : Spin) (h : s.isInteger) :
145 cyclePhase s = 1 := by
146 unfold cyclePhase Spin.value Spin.isInteger at *
147 -- s.twice is even, so s.twice % 2 = 0
148 have heven : s.twice % 2 = 0 := h
149 -- Get k such that s.twice = 2k
150 have ⟨k, hk⟩ := Int.even_iff.mpr heven
151 -- The phase is exp(2πi × (twice/2)) = exp(2πi × k) = 1
152 have h_rewrite : 2 * π * I * (s.twice / 2 : ℝ) = (k : ℂ) * (2 * π * I) := by
153 rw [hk]
154 push_cast
155 ring
156 rw [h_rewrite, Complex.exp_int_mul_two_pi_mul_I]
157
158/-! ## Particle Statistics Classification -/
159
160/-- Particle statistics type. -/
161inductive Statistics where
162 | fermiDirac
163 | boseEinstein
164deriving DecidableEq, Repr
165
166/-- Determine statistics from spin. -/
167def statisticsFromSpin (s : Spin) : Statistics :=
168 if s.isHalfInteger then Statistics.fermiDirac else Statistics.boseEinstein
169
170/-- **THEOREM (Spin-Statistics)**: Half-integer spin implies Fermi-Dirac statistics. -/
171theorem spin_statistics_fermion (s : Spin) (h : s.isHalfInteger) :
172 statisticsFromSpin s = Statistics.fermiDirac := by
173 simp [statisticsFromSpin, h]
174