English
If a and b are self-adjoint and commute in A, then expUnitary(a) and expUnitary(b) commute.
Русский
Если a и b — самоприводные и коммутируют в A, то expUnitary(a) и expUnitary(b) commute.
LaTeX
$$$$\operatorname{Commute}(\expUnitary(a), \expUnitary(b))$$$$
Lean4
theorem expUnitary {a b : selfAdjoint A} (h : Commute (a : A) (b : A)) : Commute (expUnitary a) (expUnitary b) :=
calc
selfAdjoint.expUnitary a * selfAdjoint.expUnitary b = selfAdjoint.expUnitary b * selfAdjoint.expUnitary a := by
rw [← h.expUnitary_add, ← h.symm.expUnitary_add, add_comm]