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import OAI.Computability.FourierCircuit.SymmetricLaplacian
namespace OAI
section
namespace ExactFourier
open scoped BigOperators
variable {α : Type} [Fintype α] [DecidableEq α]
noncomputable def diagonalBlocks {t : ℕ} (A : Fin t → Matrix α α ℂ) :
Matrix (Fin t × α) (Fin t × α) ℂ :=
fun i j => if i.1=j.1 then A i.1 i.2 j.2 else 0
namespace MatrixPrice
theorem diagonal_blocks (p : MatrixPrice) (t : ℕ) (A : Fin t → Matrix α α ℂ)
(hA : ∀ i, IsUnit (A i)) :
IsUnit (diagonalBlocks A) ∧ p.value (diagonalBlocks A)=∑ i, p.value (A i) := by
have hu := (p.blocks_lower t (diagonalBlocks A) A hA
(by intros; simp [diagonalBlocks])
(by intro i j a b hij; simp [diagonalBlocks,ne_of_lt hij])).1
refine ⟨hu,?_⟩
induction t with
| zero =>
have he : diagonalBlocks A=1 := by ext i j; exact Fin.elim0 i.1
rw [he,p.one]; simp
| succ t ih =>
have hD : IsUnit (diagonalBlocks (fun i : Fin t => A i.succ)) :=
(p.blocks_lower t _ _ (fun i => hA i.succ)
(by intros; simp [diagonalBlocks])
(by intro i j a b hij; simp [diagonalBlocks,ne_of_lt hij])).1
have he : Matrix.reindex (timeSplit t α) (timeSplit t α) (diagonalBlocks A)=
Matrix.fromBlocks (A 0) 0 0 (diagonalBlocks (fun i : Fin t => A i.succ)) := by
ext i j
rcases i with a|⟨i,a⟩ <;> rcases j with b|⟨j,b⟩ <;>
simp [Matrix.reindex_apply,Matrix.submatrix_apply,timeSplit,diagonalBlocks,
Ne.symm (Fin.succ_ne_zero _)]
rw [← p.reindex (timeSplit t α) _ hu,he,p.directSum _ _ (hA 0) hD,
ih _ (fun i => hA i.succ) hD,Fin.sum_univ_succ]
end MatrixPrice
end ExactFourier
end
section
namespace ExactFourier.RootEvaluation
open Polynomial
open scoped BigOperators Kronecker
noncomputable def fourier (t : ℕ) (ω : ℂ) : Matrix (Fin t) (Fin t) ℂ :=
fun i j => ω^(i.val*j.val)
@[simp] theorem fourier_mulVec (t : ℕ) (ω : ℂ) (x : Fin t → ℂ) :
(fourier t ω).mulVec x=RadixTwo.eval t ω x := rfl
theorem fourier_unit (t : ℕ) (ht : 0<t) (ω : ℂ) (hω : IsPrimitiveRoot ω t) :
IsUnit (fourier t ω) := by
apply Matrix.mulVec_injective_iff_isUnit.mp
intro x y h
rw [fourier_mulVec,fourier_mulVec] at h
have hh := congrArg (RadixTwo.eval t ω⁻¹) h
rw [RadixTwo.eval_inverse ht ω hω,RadixTwo.eval_inverse ht ω hω] at hh
funext i
exact mul_left_cancel₀ (by exact_mod_cast Nat.ne_of_gt ht : (t:ℂ)≠0) (congrFun hh i)
theorem fourier_price (p : MatrixPrice) (j : ℕ) (ω : ℂ)
(hω : IsPrimitiveRoot ω (2^j)) :
p.value (fourier (2^j) ω) ≤ (26/Real.log 2)*(2^j:ℝ)*Real.log (2*2^j) := by
obtain ⟨C,hC,hE⟩ := RadixTwo.exists_fft_dag j ω hω
have hu := fourier_unit (2^j) (by positivity) ω hω
have hprice := (p.le_shear _ hu).trans (p.rectangularShear_bound C _ hE)
have hsize : (C.size:ℝ)≤3*(j:ℝ)*2^j := by exact_mod_cast hC
have hlog : Real.log (2*2^j) = ((j:ℝ)+1)*Real.log 2 := by
rw [← pow_succ',Real.log_pow]
push_cast; ring
rw [hlog]
have hlog0 : Real.log 2≠0 := ne_of_gt (Real.log_pos (by norm_num))
have he : (26/Real.log 2)*(2^j:ℝ)*(((j:ℝ)+1)*Real.log 2)=26*2^j*((j:ℝ)+1) := by field_simp
rw [he]
push_cast at hprice
nlinarith [pow_pos (by norm_num : (0:ℝ)<2) j]
noncomputable def matrix (t : ℕ) (ω a : ℂ) : Matrix (Fin t) (Fin t) ℂ :=
fun i j => (a*ω^i.val)^j.val
theorem matrix_eq (t : ℕ) (ω a : ℂ) :
matrix t ω a=fourier t ω*Matrix.diagonal (fun j : Fin t => a^j.val) := by
ext i j
simp [matrix,fourier,Matrix.mul_diagonal,mul_pow,pow_mul,mul_comm]
theorem matrix_unit (t : ℕ) (ht : 0<t) (ω a : ℂ)
(hω : IsPrimitiveRoot ω t) (ha : a≠0) : IsUnit (matrix t ω a) := by
rw [matrix_eq]
exact (fourier_unit t ht ω hω).mul
(Matrix.isUnit_diagonal.mpr (Pi.isUnit_iff.mpr (fun j => isUnit_iff_ne_zero.mpr (pow_ne_zero _ ha))))
theorem matrix_price (p : MatrixPrice) (j : ℕ) (ω a : ℂ)
(hω : IsPrimitiveRoot ω (2^j)) (ha : a≠0) :
p.value (matrix (2^j) ω a)≤(26/Real.log 2)*(2^j:ℝ)*Real.log (2*2^j) := by
rw [matrix_eq,← one_mul (fourier (2^j) ω),p.monomial _ _ _
(fourier_unit _ (by positivity) ω hω) MonomialMatrix.one
(MonomialMatrix.diagonal _ (fun i => pow_ne_zero _ ha))]
exact fourier_price p j ω hω
end ExactFourier.RootEvaluation
end
section
namespace ExactFourier.RootEvaluation
open Polynomial
open scoped Kronecker BigOperators
theorem coefficient_sum (t : ℕ) (ω a : ℂ) (f : Polynomial ℂ)
(hf : f.natDegree<t) (i : Fin t) :
f.eval (a*ω^i.val)=∑ j : Fin t, matrix t ω a i j*f.coeff j.val := by
conv_lhs => rw [f.as_sum_range_C_mul_X_pow' hf]
simp only [eval_finsetSum,eval_mul,eval_C,eval_pow,eval_X]
rw [← Fin.sum_univ_eq_sum_range]
apply Finset.sum_congr rfl
intro j _
simp only [matrix,mul_comm]
theorem eval_remainder (ℓ f : Polynomial ℂ) (s : ℂ) (hs : ℓ.eval s=0) :
(f%ₘℓ).eval s=f.eval s := by
rw [modByMonic_eq_sub_mul_div,eval_sub,eval_mul,hs,zero_mul,sub_zero]
variable {α : Type} [Fintype α] [DecidableEq α]
theorem intertwine (t : ℕ) (ht : 0<t) (ω a : ℂ) (ℓ : Polynomial ℂ)
(hℓ : ℓ.Monic) (hℓt : ℓ.natDegree=t) (hs : ∀ i : Fin t,ℓ.eval (a*ω^i.val)=0)
(G : Matrix α α (Polynomial ℂ)) :
(matrix t ω a ⊗ₖ (1 : Matrix α α ℂ))*Boundary.modulusMatrix t ℓ G =
diagonalBlocks (fun i : Fin t => G.map (eval (a*ω^i.val)))*
(matrix t ω a ⊗ₖ (1 : Matrix α α ℂ)) := by
ext ⟨ai,aj⟩ ⟨bi,bj⟩
simp only [Matrix.mul_apply,Fintype.sum_prod_type,Matrix.kronecker_apply,Matrix.one_apply,
diagonalBlocks,ite_mul,mul_ite,mul_one,mul_zero,zero_mul]
simp only [Finset.sum_ite_eq,Finset.mem_univ,ite_true]
have hne : ℓ≠1 := by
intro he
have hh := congrArg Polynomial.natDegree he
rw [hℓt] at hh
simp only [natDegree_one] at hh
omega
have hd := natDegree_modByMonic_lt (G aj bj*X^bi.val) hℓ hne
rw [hℓt] at hd
simp only [Boundary.modulusMatrix,Finset.sum_ite_irrel,Finset.sum_const_zero,
Finset.sum_ite_eq,Finset.sum_ite_eq',Finset.mem_univ,ite_true]
rw [← coefficient_sum t ω a _ hd ai,eval_remainder _ _ _ (hs ai)]
simp [eval_mul,eval_pow,eval_X,matrix,mul_comm]
theorem root_modulus (t : ℕ) (ht : 0<t) (ω a : ℂ) (hω : IsPrimitiveRoot ω t)
(i : Fin t) : (X^t-C (a^t) : Polynomial ℂ).eval (a*ω^i.val)=0 := by
obtain ⟨size, rfl⟩ := Nat.exists_eq_succ_of_ne_zero (Nat.ne_of_gt ht)
simp only [eval_sub,eval_pow,eval_X,eval_C,mul_pow,← pow_mul]
rw [Nat.mul_comm i.val size.succ,pow_mul,hω.pow_eq_one,one_pow,mul_one,sub_self]
end ExactFourier.RootEvaluation
end
section
namespace ExactFourier.RootEvaluation
open Polynomial TensorAxis
open scoped Kronecker BigOperators
variable {α : Type} [Fintype α] [DecidableEq α]
theorem modulus_upper (p : MatrixPrice) (j : ℕ) (ω a : ℂ)
(hω : IsPrimitiveRoot ω (2^j)) (ha : a≠0)
(G : Matrix α α (Polynomial ℂ))
(hG : ∀ i : Fin (2^j),IsUnit (G.map (eval (a*ω^i.val)))) :
IsUnit (Boundary.modulusMatrix (2^j) (X^(2^j)-C (a^(2^j))) G) ∧
p.value (Boundary.modulusMatrix (2^j) (X^(2^j)-C (a^(2^j))) G) ≤
(∑ i : Fin (2^j),p.value (G.map (eval (a*ω^i.val))))+
2*(Fintype.card α:ℝ)*(26/Real.log 2)*(2^j:ℝ)*Real.log (2*2^j) := by
let t : ℕ := 2^j
have ht : 0<t := by dsimp [t]; positivity
let ℓ : Polynomial ℂ := X^t-C (a^t)
have hℓ : ℓ.Monic := monic_X_pow_sub_C _ (Nat.ne_of_gt ht)
have hℓt : ℓ.natDegree=t := natDegree_X_pow_sub_C
let P := matrix t ω a ⊗ₖ (1 : Matrix α α ℂ)
let W := Boundary.modulusMatrix t ℓ G
let D := diagonalBlocks (fun i : Fin t => G.map (eval (a*ω^i.val)))
have hP : IsUnit P := TensorTools.unit_tensor _ _ (matrix_unit t ht ω a hω ha) isUnit_one
obtain ⟨hDu,hDp⟩ := p.diagonal_blocks t _ hG
change IsUnit D at hDu
change p.value D=_ at hDp
have he : P*W=D*P := intertwine t ht ω a ℓ hℓ hℓt (root_modulus t ht ω a hω) G
have hW : IsUnit W := by
have hh : IsUnit (P*W) := by rw [he]; exact hDu.mul hP
have hd := (Matrix.isUnit_iff_isUnit_det _).mp hh
rw [Matrix.det_mul] at hd
exact (Matrix.isUnit_iff_isUnit_det _).mpr
(isUnit_iff_ne_zero.mpr (mul_ne_zero_iff.mp (isUnit_iff_ne_zero.mp hd)).2)
refine ⟨hW,?_⟩
have hconj : P*W*P⁻¹=D := by
rw [he,Matrix.mul_assoc,Matrix.mul_nonsing_inv _ ((Matrix.isUnit_iff_isUnit_det _).mp hP),mul_one]
have hprice := p.le_conjugate P W hP hW
rw [hconj,hDp] at hprice
have hp : p.value P=(Fintype.card α:ℝ)*p.value (matrix t ω a) := by
rw [p.tensor _ _ (matrix_unit t ht ω a hω ha) isUnit_one,p.one,mul_zero,add_zero]
rw [hp] at hprice
have hv := matrix_price p j ω a hω ha
have hv' := mul_le_mul_of_nonneg_left hv (show (0:ℝ)≤Fintype.card α by positivity)
change p.value W≤_
dsimp only [t] at hprice
nlinarith only [hprice,hv']
end ExactFourier.RootEvaluation
end
section
namespace ExactFourier.RootEvaluation
theorem exists_dilation (t : ℕ) (ω : ℂ) (hω : ω≠0) (E : Finset ℂ) :
∃ a : ℂ, a≠0 ∧ ∀ i : Fin t, a*ω^i.val ∉ E := by
classical
let F : Finset ℂ := insert 0 (Finset.univ.biUnion (fun i : Fin t => E.image (fun s => s/ω^i.val)))
obtain ⟨a,ha⟩ := F.exists_notMem
refine ⟨a,?_,?_⟩
· intro he
apply ha
simp [F,he]
· intro i hi
apply ha
apply Finset.mem_insert_of_mem
apply Finset.mem_biUnion.mpr
refine ⟨i,Finset.mem_univ _,Finset.mem_image.mpr ⟨a*ω^i.val,hi,?_⟩⟩
exact mul_div_cancel_right₀ _ (pow_ne_zero _ hω)
end ExactFourier.RootEvaluation
end
section
namespace ExactFourier
open Filter Topology
theorem exists_dyadic_between (b : ℕ) (hb : 0<b) : ∃ j : ℕ, b≤2^j ∧ 2^j≤2*b := by
refine ⟨Nat.log 2 b+1,(Nat.lt_pow_succ_log_self (by decide : 1<2) b).le,?_⟩
have hh := Nat.pow_log_le_self 2 (Nat.ne_of_gt hb)
rw [pow_succ]
omega
theorem fixed_price_of_dyadic_boundary (x y C : ℝ) (hC : 0≤C)
(h : ∀ k j : ℕ, 0<k →
(2^j:ℝ)*k*(x-y) ≤ C*((2^j:ℝ)*Real.log (2*2^j)+(k+1:ℝ)^6)) : x≤y := by
have he (m : ℕ) : x-y ≤ (2*C)*boundaryError m := by
let b : ℕ := (m+2)^8
have hb : 0<b := by dsimp [b]; positivity
obtain ⟨j,hlo,hhi⟩ := exists_dyadic_between b hb
let T : ℕ := 2^j
have hTr : 0<(T:ℝ) := by exact_mod_cast (pow_pos (by decide : 0<2) j)
have hbr : (b:ℝ)=((m:ℝ)+2)^8 := by dsimp [b]; push_cast; rfl
have hk : 0<(m:ℝ)+1 := by positivity
have hb1 : (1:ℝ)≤b := by exact_mod_cast (hb : 1≤b)
have hloR : (b:ℝ)≤T := by exact_mod_cast hlo
have hhiR : (T:ℝ)≤2*b := by exact_mod_cast hhi
have hln : Real.log (2*(T:ℝ)) ≤ 2*Real.log (2*b) := by
have harg : 2*(T:ℝ)≤(2*(b:ℝ))^2 := by nlinarith
have hh := Real.log_le_log (by positivity : (0:ℝ)<2*T) harg
simpa only [Real.log_pow,Nat.cast_ofNat] using hh
have hln0 : 0≤Real.log (2*(b:ℝ)) := Real.log_nonneg (by linarith)
have hr : ((m:ℝ)+2)^6 / ((T:ℝ)*((m:ℝ)+1)) ≤
((m:ℝ)+2)^6 / ((b:ℝ)*((m:ℝ)+1)) := by
apply div_le_div_of_nonneg_left (by positivity) (by positivity)
exact mul_le_mul_of_nonneg_right hloR hk.le
have hlog : Real.log (2*(T:ℝ))/((m:ℝ)+1) ≤
2*Real.log (2*(b:ℝ))/((m:ℝ)+1) := by exact div_le_div_of_nonneg_right hln hk.le
have herr : Real.log (2*(T:ℝ))/((m:ℝ)+1)+
((m:ℝ)+2)^6/((T:ℝ)*((m:ℝ)+1)) ≤2*boundaryError m := by
have hfrac : 0≤((m:ℝ)+2)^6/((b:ℝ)*((m:ℝ)+1)) := by positivity
dsimp only [boundaryError]
rw [← hbr]
rw [mul_div_assoc] at hlog
nlinarith only [hr,hlog,hfrac]
have hh := h (m+1) j (by omega)
have hTR : (2^j:ℝ)=(T:ℝ) := by dsimp [T]; norm_cast
rw [hTR] at hh
push_cast at hh
have hnorm : x-y ≤ C*(Real.log (2*(T:ℝ))/((m:ℝ)+1)+
((m:ℝ)+2)^6/((T:ℝ)*((m:ℝ)+1))) := by
have hn : x-y ≤ (C*((T:ℝ)*Real.log (2*T)+((m:ℝ)+2)^6))/((T:ℝ)*((m:ℝ)+1)) :=
(le_div_iff₀ (mul_pos hTr hk)).mpr (by nlinarith only [hh])
convert hn using 1 ; field_simp
calc
x-y ≤ _ := hnorm
_ ≤ C*(2*boundaryError m) := mul_le_mul_of_nonneg_left herr hC
_ = (2*C)*boundaryError m := by ring
have hh := ge_of_tendsto (boundaryError_tendsto.const_mul (2*C)) (Filter.Eventually.of_forall he)
have : x-y≤0 := by simpa using hh
linarith
end ExactFourier
end
section
namespace ExactFourier.MatrixPrice
open TensorAxis Polynomial CoefficientTime
open scoped BigOperators
variable {α : Type} [Fintype α] [DecidableEq α]
theorem specialize_polynomial_zero (p : MatrixPrice) (G : Matrix α α (Polynomial ℂ))
(hG0 : IsUnit (G.map (eval 0))) (E : Finset ℂ) (C0 : ℝ)
(hG : ∀ s : ℂ, s∉E → IsUnit (G.map (eval s)) ∧ p.value (G.map (eval s))≤C0) :
p.value (G.map (eval 0))≤C0 := by
classical
obtain ⟨s,hs⟩ := E.exists_notMem
have hC0 : 0≤C0 := (p.nonneg _ (hG s hs).1).trans (hG s hs).2
by_cases hn : Fintype.card α=0
· have : IsEmpty α := Fintype.card_eq_zero_iff.mp hn
have he : G.map (eval 0)=1 := by ext i; exact isEmptyElim i
rw [he,p.one]
exact hC0
have hcoeff : (fun f : Polynomial ℂ => f.coeff 0)=evalRingHom 0 := by
funext f; exact coeff_zero_eq_eval_zero f
have hGu0 : IsUnit (G.map (fun f => f.coeff 0)) := by
rw [hcoeff,coe_evalRingHom]; exact hG0
obtain ⟨CB,hCB,hboundary⟩ := Boundary.exists_boundary_bound p G hGu0
let C : ℝ := CB+52/Real.log 2
have hC : 0≤C := by dsimp [C]; positivity
apply fixed_price_of_dyadic_boundary (p.value (G.map (eval 0))) C0
(C*Fintype.card α) (by positivity)
intro k j hk
let t : ℕ := 2^j
have ht : 0<t := by dsimp [t]; positivity
let ω := zeta t
have hω : IsPrimitiveRoot ω t := Complex.isPrimitiveRoot_exp _ (Nat.ne_of_gt ht)
obtain ⟨a,ha,had⟩ := RootEvaluation.exists_dilation t ω (hω.ne_zero (Nat.ne_of_gt ht)) E
let ℓ : Polynomial ℂ := X^t-Polynomial.C (a^t)
have hℓ : ℓ.Monic := monic_X_pow_sub_C _ (Nat.ne_of_gt ht)
have hℓt : ℓ.natDegree=t := natDegree_X_pow_sub_C
have hℓ0 : ℓ.coeff 0≠0 := by simp [ℓ,coeff_zero_eq_eval_zero,Nat.ne_of_gt ht,ha]
have hmap (s : ℂ) : (power G k).map (eval s)=power (G.map (eval s)) k := by
rw [← coe_evalRingHom]
exact map_power (evalRingHom s) G k
have hroots (i : Fin t) : IsUnit ((power G k).map (eval (a*ω^i.val))) := by
rw [hmap]; exact unit_power _ (hG _ (had i)).1 k
obtain ⟨hWu,hupper⟩ := RootEvaluation.modulus_upper p j ω a hω ha (power G k) hroots
have hblocks : (∑ i : Fin t,p.value ((power G k).map (eval (a*ω^i.val))))≤
(t:ℝ)*Fintype.card (Fibers α k)*C0 := by
calc
_ ≤ ∑ i : Fin t,(Fintype.card (Fibers α k):ℝ)*C0 := by
apply Finset.sum_le_sum
intro i hi
rw [hmap,price_power p _ (hG _ (had i)).1]
exact mul_le_mul_of_nonneg_left (hG _ (had i)).2 (by positivity)
_ = _ := by simp; ring
have hb := hboundary k t hk ht ℓ hℓ hℓt hℓ0 hWu
have hconst : (Boundary.seriesMatrix (power G k)).map PowerSeries.constantCoeff=
power (G.map (eval 0)) k := by
have he : (Boundary.seriesMatrix (power G k)).map PowerSeries.constantCoeff=
(power G k).map (eval 0) := by ext i l; simp [coeff_zero_eq_eval_zero]
rw [he,hmap]
have hlow := p.trunc_lower_bound t (Boundary.seriesMatrix (power G k))
(by rw [hconst]; exact unit_power _ hG0 k)
rw [hconst,price_power p _ hG0,← Boundary.timeMatrix_eq_trunc] at hlow
rw [card_space] at hupper
push_cast at hupper
have hN : 0<(Fintype.card α:ℝ)^k := pow_pos (by exact_mod_cast Nat.pos_of_ne_zero hn) k
have herror : (t:ℝ)*Fintype.card (Fibers α k)*(p.value (G.map (eval 0))-C0)≤
C*(Fintype.card α:ℝ)^k*((t:ℝ)*Real.log (2*t)+(k+1:ℝ)^6) := by
have hb' := (abs_le.mp hb).1
have hextra : 0≤(52/Real.log 2)*(Fintype.card α:ℝ)^k*(k+1:ℝ)^6 := by positivity
dsimp only [ℓ,t] at hb' hblocks hlow ⊢
push_cast at hb' hblocks hlow ⊢
dsimp only [C]
simp only [div_eq_mul_inv] at hupper hextra ⊢
nlinarith only [hb',hupper,hlow,hblocks,hextra]
have hrel : (Fintype.card (Fibers α k):ℝ)*Fintype.card α=(k:ℝ)*(Fintype.card α:ℝ)^k := by
have hh := Triangular.calls_card_relation (β := α) k
change Fintype.card (Fibers α k)*Fintype.card α=k*Fintype.card (Space α k) at hh
rw [card_space] at hh
exact_mod_cast hh
have hm := mul_le_mul_of_nonneg_right herror (Nat.cast_nonneg (Fintype.card α) : (0:ℝ)≤_)
apply (mul_le_mul_iff_right₀ hN).mp
have ha := congrArg (fun v : ℝ => (t:ℝ)*v*(p.value (G.map (eval 0))-C0)) hrel
dsimp only [t] at hm ha
push_cast at hm ha
nlinarith only [hm,ha]
end ExactFourier.MatrixPrice
end
end OAI