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Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

Nat Weighted Degree add le

GuruswamiSudan.natWeightedDegree_add_le

Plain-language statement

The weighted degree of a sum is at most the maximum of the weighted degrees.

Exact Lean statement

lemma natWeightedDegree_add_le (p q : F[X][Y]) (u v : ℕ) :
    natWeightedDegree (p + q) u v ≤ max (natWeightedDegree p u v) (natWeightedDegree q u v)

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma natWeightedDegree_add_le (p q : F[X][Y]) (u v : ) :    natWeightedDegree (p + q) u v  max (natWeightedDegree p u v) (natWeightedDegree q u v) := by  refine Finset.sup_le fun m hm  ?_  by_cases h : m  p.support <;>  by_cases h' : m  q.support <;>    simp_all only [Polynomial.mem_support_iff, coeff_add, ne_eq, le_sup_iff]  · have h_deg : (p.coeff m + q.coeff m).natDegree         max ((p.coeff m).natDegree) ((q.coeff m).natDegree) :=      natDegree_add_le (p.coeff m) (q.coeff m)    cases max_cases (natDegree (p.coeff m))      (natDegree (q.coeff m)) <;> simp_all only [sup_of_le_left, sup_eq_left, and_self,        natWeightedDegree]    · exact Or.inl (le_trans (add_le_add (mul_le_mul_of_nonneg_left h_deg <|        Nat.zero_le _) le_rfl) <| Finset.le_sup (f := fun m  u * natDegree          (p.coeff m) + v * m) <| by aesop)    · exact Or.inr (le_trans (add_le_add (mul_le_mul_of_nonneg_left h_deg <|        Nat.zero_le _) le_rfl) <| Finset.le_sup        (f := fun m  u * natDegree (q.coeff m) + v * m) <| by aesop)  all_goals simp_all only [not_not, add_zero, zero_add, not_false_eq_true]  · exact Or.inl <| Finset.le_sup (f := fun m  u * natDegree (p.coeff m) + v * m) <| by aesop  · exact Or.inr <| Finset.le_sup (f := fun m  u * natDegree (q.coeff m) + v * m) <| by aesop  · simp at hm
Project
ArkLib
License
Apache-2.0
Commit
fad5cbf80877
Source
ArkLib/Data/CodingTheory/GuruswamiSudan/Basic.lean:477-498

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Project documentation

This lemma proves the final algebraic step in the DG25 Theorem 3.1 proof. It shows that if R > e + 1, then e * (R / (R - 1)) < e + 1. The intuition is that the fraction R / (R - 1) is always greater than 1, but as R gets larger, it gets closer to 1. The hypothesis R > e + 1 provides a strong enough bound to ensure the product e * (fraction) do...

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Project-declaredLean 4.31.0

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Plain-language statement

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cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

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Project-declaredLean 4.31.0

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ArkLib.Lattices.Ajtai.gadgetDecompose_lawful

Plain-language statement

The base-b gadget decomposition is a lawful gadget decomposition.

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

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