theorem
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term proof
hpOperator_eigenvector_neg
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formal statement (Lean)
79theorem hpOperator_eigenvector_neg (q : ℕ) (a : ℤ) :
80 (hpOperator q a).mulVec ![1, -1] = (-frobeniusAngle q a) • ![1, -1] := by
proof body
Term-mode proof.
81 ext i
82 fin_cases i <;>
83 simp [hpOperator, Matrix.mulVec, Matrix.cons_val', Matrix.empty_val',
84 Matrix.cons_val_fin_one, Matrix.cons_val_zero, Matrix.cons_val_one,
85 Matrix.head_cons, Matrix.head_fin_const,
86 Matrix.cons_dotProduct, Matrix.dotProduct_empty, Fin.sum_univ_two] <;>
87 ring
88
89/-! ## Hasse bound implies real spectrum
90
91For the angle `θ` to be a real number representing a meaningful spectral
92quantity, we need `arccos`'s argument to lie in `[-1, 1]`. This is the
93content of the Hasse--Weil bound. -/
94
95/-- If the Hasse bound `a^2 ≤ 4q` holds, then `a / (2√q) ∈ [-1, 1]`. -/