Chu's constructions of sum-dominant sets

DefinitionSets given by consecutive differences#✓fully proved

For an integer \(a\) and natural numbers \(g_1, \dots, g_r\), the set \((a \mid g_1, \dots, g_r)\) is the finite set of integers \(\{a, a + g_1, a + g_1 + g_2, \dots, a + g_1 + \dots + g_r\}\); for \(r = 0\) it is \(\{a\}\).

When every \(g_i\) is positive, the differences between consecutive elements of this set, listed from the smallest element to the largest, are \(g_1, \dots, g_r\); a zero gap repeats a partial sum, which the set records once.

public def setOfConsecutiveDifferences : ℤ → List ℕ → Finset ℤ
  | a, [] => {a}
  | a, g :: l => insert a (setOfConsecutiveDifferences (a + g) l)
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 1 (Spohn's notation).
Used by 7

TheoremPrepending a gap#✓fully proved

For an integer \(a\) and natural numbers \(g_1, \dots, g_r\) (\(r \ge 0\)), write \((a \mid g_1, \dots, g_r)\) for the set of partial sums \(\{a, a + g_1, \dots, a + g_1 + \dots + g_r\}\). Then for every natural number \(g\), \((a \mid g, g_1, \dots, g_r) = \{a\} \cup (a + g \mid g_1, \dots, g_r)\).

When \(g > 0\), the new element \(a\) is smaller than every element of \((a + g \mid g_1, \dots, g_r)\).

public theorem setOfConsecutiveDifferences_cons (a : ℤ) (g : ℕ) (l : List ℕ) :
    setOfConsecutiveDifferences a (g :: l) = insert a (setOfConsecutiveDifferences (a + g) l)
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 1 (Spohn's notation).
Uses 1

TheoremAn example of difference notation#✓fully proved

The set with least element \(0\) and consecutive differences \(1, 5, 1, 1, 9, 7\) is \((0 \mid 1, 5, 1, 1, 9, 7) = \{0, 1, 6, 7, 8, 17, 24\}\).

public theorem setOfConsecutiveDifferences_example :
    setOfConsecutiveDifferences 0 [1, 5, 1, 1, 9, 7] = {0, 1, 6, 7, 8, 17, 24}
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 1 (Spohn's notation).
Uses 1

DefinitionChu difference block#✓fully proved

For a natural number \(k\), the difference block \(M^k\) is the list of natural numbers \(1, 4, \ldots, 4, 3\) of length \(k + 2\): a \(1\), then \(k\) copies of \(4\), then a \(3\).

public def chuBlock (k : ℕ) : List ℕ :=
  1 :: List.replicate k 4 ++ [3]
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 1 (definition of M^k).
Used by 7

TheoremThe Chu difference blocks \(M^1\) and \(M^2\)#✓fully proved

The Chu difference block \(M^1\) is the list \(1, 4, 3\), and the Chu difference block \(M^2\) is the list \(1, 4, 4, 3\).

public theorem chuBlock_one_two : chuBlock 1 = [1, 4, 3] ∧ chuBlock 2 = [1, 4, 4, 3]
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 1 (definition of M^k).
Uses 1
Statement usesChu difference block

TheoremA balanced family of Chu et al#●ready to prove

Let \(k\) be a positive integer and let \(A = (0 \mid 1, 1, 2, M^k, M^{k+1}, 1, 1) \subseteq \mathbb{Z}\) be the set of partial sums, starting at \(0\), of the difference sequence formed by \(1, 1, 2\), the Chu difference blocks \(M^k\) and \(M^{k+1}\), and \(1, 1\). Then \(A\) is balanced: \(|A + A| = |A - A|\).

public theorem_wanted chu_family_balanced {k : ℕ} (hk : 0 < k) :
    let A := setOfConsecutiveDifferences 0 ([1, 1, 2] ++ chuBlock k ++ chuBlock (k + 1) ++ [1, 1])
    (A + A).card = (A - A).card
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Theorem 1.
Uses 2

TheoremA difference-dominated family of Chu et al#●ready to prove

Let \(k\) be a positive integer and let \(A = (0 \mid 1, 1, 2, M^k, M^{k+1}, M^{k+1}, 1, 1) \subseteq \mathbb{Z}\) be the set of partial sums, starting at \(0\), of the difference sequence formed by \(1, 1, 2\), the Chu difference blocks \(M^k\), \(M^{k+1}\) and \(M^{k+1}\), and \(1, 1\). Then \(A\) is difference-dominated: \(|A + A| < |A - A|\).

public theorem_wanted chu_family_difference_dominated {k : ℕ} (hk : 0 < k) :
    let A := setOfConsecutiveDifferences 0
      ([1, 1, 2] ++ chuBlock k ++ chuBlock (k + 1) ++ chuBlock (k + 1) ++ [1, 1])
    (A + A).card < (A - A).card
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Theorem 2.
Uses 2

TheoremMSTD sets with \(M^k\) before \(M^{k+1}\) (Theorem 3)#●ready to prove

Let \(k\) be a positive integer, let \(M^n\) denote the block \(1, 4, \dots, 4, 3\) with \(n\) fours, and let \(M_1\) be one of the sequences \((1, 1, 2)\), \((1, 1, 2, 1)\). Let \(A = (0 \mid 1, 1, 2, M^k, M^{k+1}, M_1)\) be the set of partial sums, starting from \(0\), of the concatenated sequence \(1, 1, 2, M^k, M^{k+1}, M_1\). Then \(A\) is sum-dominated: \(|A - A| < |A + A|\).

public theorem_wanted chu_family_mstd_increasing {k : ℕ} (hk : 0 < k) {M₁ : List ℕ}
    (hM₁ : M₁ = [1, 1, 2] ∨ M₁ = [1, 1, 2, 1]) :
    let A := setOfConsecutiveDifferences 0 ([1, 1, 2] ++ chuBlock k ++ chuBlock (k + 1) ++ M₁)
    (A - A).card < (A + A).card
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Theorem 3.
Uses 2

TheoremMSTD sets with \(M^{k+1}\) before \(M^k\) (Theorem 4)#●ready to prove

Let \(k\) be a positive integer, let \(M^n\) denote the block \(1, 4, \dots, 4, 3\) with \(n\) fours, and let \(M_1\) be one of the sequences \((1, 1)\), \((1, 1, 2)\), \((1, 1, 2, 1)\). Let \(A = (0 \mid 1, 1, 2, M^{k+1}, M^k, M_1)\) be the set of partial sums, starting from \(0\), of the concatenated sequence \(1, 1, 2, M^{k+1}, M^k, M_1\). Then \(A\) is sum-dominated: \(|A - A| < |A + A|\).

public theorem_wanted chu_family_mstd_decreasing {k : ℕ} (hk : 0 < k) {M₁ : List ℕ}
    (hM₁ : M₁ = [1, 1] ∨ M₁ = [1, 1, 2] ∨ M₁ = [1, 1, 2, 1]) :
    let A := setOfConsecutiveDifferences 0 ([1, 1, 2] ++ chuBlock (k + 1) ++ chuBlock k ++ M₁)
    (A - A).card < (A + A).card
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Theorem 4.
Uses 2

DefinitionKumar–Mohan–Pandey sets#✓fully proved

For natural numbers \(k\), \(l\), \(t\), let \(M^n\) be the block \(1, 4, \dots, 4, 3\) with \(n\) fours, and let \(D\) be the sequence made of \(t\) copies of the block \(1, 1, 2, M^k, \dots, M^k\) (with \(l\) copies of \(M^k\)) followed by \(1, 1, 2, 1\). The set \(A_{k,l,t}\) is \((0 \mid D)\), the set of partial sums of \(D\) starting from \(0\).

Each block \(1, 1, 2, M^k, \dots, M^k\) has sum \(4(kl + l + 1)\), matching the bounds \(t(kl + l + 1)\) in Lemmas 1-7 of the paper.

public def chuFamilyKLT (k l t : ℕ) : Finset ℤ :=
  setOfConsecutiveDifferences 0
    ((List.replicate t ([1, 1, 2] ++ (List.replicate l (chuBlock k)).flatten)).flatten ++
      [1, 1, 2, 1])
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 3 (the set of Lemmas 1-7 and Theorems 6-7).
Uses 2 · Used by 9

TheoremThe Kumar–Mohan–Pandey set \(A_{1,1,1}\)#✓fully proved

For \(k = l = t = 1\), the Kumar–Mohan–Pandey set \(A_{1,1,1}\), the set of partial sums starting from \(0\) of the sequence \(1, 1, 2, 1, 4, 3, 1, 1, 2, 1\), is \(\{0, 1, 2, 4, 5, 9, 12, 13, 14, 16, 17\}\).

public theorem chuFamilyKLT_one_one_one :
    chuFamilyKLT 1 1 1 = {0, 1, 2, 4, 5, 9, 12, 13, 14, 16, 17}
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Section 3 (the set of Lemmas 1-7 and Theorems 6-7).
Uses 1

TheoremDifferences in the Kumar–Mohan–Pandey sets (Lemma 1)#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers, let \(A = A_{k,l,t}\) be the Kumar–Mohan–Pandey set, and put \(T = t(kl + l + 1)\). Then the difference set \(A - A\) contains \(4i\) and \(1 + 4i\) for every integer \(i\) with \(1 \le i \le 1 + T\), and contains \(3 + 4i\) for every integer \(i\) with \(0 \le i \le T\).

public theorem_wanted chuFamilyKLT_mem_sub {k l t : ℕ} (hk : 0 < k) (hl : 0 < l) (ht : 0 < t) :
    (∀ i : ℕ, 1 ≤ i → i ≤ 1 + t * (k * l + l + 1) →
        4 * (i : ℤ) ∈ chuFamilyKLT k l t - chuFamilyKLT k l t ∧
          1 + 4 * (i : ℤ) ∈ chuFamilyKLT k l t - chuFamilyKLT k l t) ∧
      ∀ i : ℕ, i ≤ t * (k * l + l + 1) →
        3 + 4 * (i : ℤ) ∈ chuFamilyKLT k l t - chuFamilyKLT k l t
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Lemma 1.
Uses 1

TheoremPositive differences of the form 6 + 4m in the Chu family set#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers and let \(A \subseteq \mathbb{Z}\) be the Chu family set with parameters \(k\), \(l\), \(t\). Then exactly \(lt + t\) elements \(d\) of \(A - A\) satisfy \(d \ge 6\) and \(d \equiv 2 \pmod 4\); that is, exactly \(lt + t\) positive differences of \(A\) have the form \(6 + 4m\) with \(m \ge 0\) an integer.

public theorem_wanted chuFamilyKLT_card_sub_six_add_four_mul {k l t : ℕ} (hk : 0 < k)
    (hl : 0 < l) (ht : 0 < t) :
    ((chuFamilyKLT k l t - chuFamilyKLT k l t).filter
        fun d => 6 ≤ d ∧ d % 4 = 2).card = l * t + t
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Lemma 3.
Uses 1

TheoremElements of the Kumar–Mohan–Pandey sets (Lemma 4)#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers, let \(A = A_{k,l,t}\) be the Kumar–Mohan–Pandey set, and put \(T = t(kl + l + 1)\). Then \(1 + 4i \in A\) for every integer \(i\) with \(0 \le i \le 1 + T\), and \(2 + 4T \in A\) and \(4 + 4T \in A\).

public theorem_wanted chuFamilyKLT_mem {k l t : ℕ} (hk : 0 < k) (hl : 0 < l) (ht : 0 < t) :
    (∀ i : ℕ, i ≤ 1 + t * (k * l + l + 1) → 1 + 4 * (i : ℤ) ∈ chuFamilyKLT k l t) ∧
      2 + 4 * ((t * (k * l + l + 1) : ℕ) : ℤ) ∈ chuFamilyKLT k l t ∧
      4 + 4 * ((t * (k * l + l + 1) : ℕ) : ℤ) ∈ chuFamilyKLT k l t
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Lemma 4.
Uses 1

TheoremElements of the sumset of the Chu family set#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers, let \(A \subseteq \mathbb{Z}\) be the Chu family set with parameters \(k\), \(l\), \(t\), and let \(T = t(kl + l + 1)\). Then \(1 + 4i\) and \(2 + 4i\) lie in \(A + A\) for every integer \(i\) with \(0 \le i \le 2 + 2T\), and \(3 + 4i\) lies in \(A + A\) for every integer \(i\) with \(0 \le i \le 1 + 2T\).

public theorem_wanted chuFamilyKLT_mem_add {k l t : ℕ} (hk : 0 < k) (hl : 0 < l) (ht : 0 < t) :
    (∀ i : ℕ, i ≤ 2 + 2 * (t * (k * l + l + 1)) →
        1 + 4 * (i : ℤ) ∈ chuFamilyKLT k l t + chuFamilyKLT k l t ∧
          2 + 4 * (i : ℤ) ∈ chuFamilyKLT k l t + chuFamilyKLT k l t) ∧
      ∀ i : ℕ, i ≤ 1 + 2 * (t * (k * l + l + 1)) →
        3 + 4 * (i : ℤ) ∈ chuFamilyKLT k l t + chuFamilyKLT k l t
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Lemma 5.
Uses 1

TheoremBlock starting points of the Chu family set#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers and let \(A \subseteq \mathbb{Z}\) be the Chu family set with parameters \(k\), \(l\), \(t\). Then \(4 + (4k + 4)i + (4kl + 4l + 4)j \in A\) for all integers \(i\), \(j\) with \(0 \le i \le l\) and \(0 \le j \le t - 1\).

public theorem_wanted chuFamilyKLT_mem_block_starts {k l t : ℕ} (hk : 0 < k) (hl : 0 < l)
    (ht : 0 < t) (i j : ℕ) (hi : i ≤ l) (hj : j < t) :
    4 + (4 * k + 4) * (i : ℤ) + (4 * k * l + 4 * l + 4) * (j : ℤ) ∈ chuFamilyKLT k l t
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Lemma 6.
Uses 1

TheoremSize of the difference set of the Chu family set#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers and let \(A \subseteq \mathbb{Z}\) be the Chu family set with parameters \(k\), \(l\), \(t\). Then \(|A - A| = 11 + 6klt + 8lt + 8t\).

public theorem_wanted chuFamilyKLT_card_sub {k l t : ℕ} (hk : 0 < k) (hl : 0 < l) (ht : 0 < t) :
    (chuFamilyKLT k l t - chuFamilyKLT k l t).card = 11 + 6 * k * l * t + 8 * l * t + 8 * t
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Theorem 6.
Uses 1

TheoremLower bound for the sumset of the Chu family set#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers and let \(A \subseteq \mathbb{Z}\) be the Chu family set with parameters \(k\), \(l\), \(t\). Then \(|A + A| \ge 11 + 6klt + 10lt + 8t\).

Together with \(|A - A| = 11 + 6klt + 8lt + 8t\) (Theorem 6), this shows that \(A\) is sum-dominated (MSTD): \(|A + A| > |A - A|\).

public theorem_wanted chuFamilyKLT_card_add {k l t : ℕ} (hk : 0 < k) (hl : 0 < l) (ht : 0 < t) :
    11 + 6 * k * l * t + 10 * l * t + 8 * t ≤ (chuFamilyKLT k l t + chuFamilyKLT k l t).card
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Theorem 7.
Uses 1

TheoremSix disjoint families in the sumset of the Chu family set#●ready to prove

Let \(k\), \(l\), \(t\) be positive integers, let \(A \subseteq \mathbb{Z}\) be the Chu family set with parameters \(k\), \(l\), \(t\), and let \(P = 8kl + 8l + 8\). Let \(X_1\), \(X_2\), \(X_4\), \(X_5\) be the sets of the integers \(Pj + (4k + 4)i + 4\), \(Pj + (4k + 4)i + 8\), \(Pj + 4kl + 4l + (4k + 4)i + 8\) and \(Pj + 4kl + 4l + (4k + 4)i + 12\) respectively, for \(1 \le i \le l\) and \(0 \le j \le t - 1\), and let \(X_3\), \(X_6\) be the sets of the integers \(Pj + 4kl + 4l + 12\) and \(Pj + 8kl + 8l + 16\) respectively, for \(0 \le j \le t - 1\). Then \(A + A\) contains \(\{0, 4, 8\}\) and each of \(X_1, \ldots, X_6\), and the sets \(X_1, \ldots, X_6\) are pairwise disjoint.

MetaMathlibExt.chuFamilyKLT_add_supset_six_families · 16 lines
public theorem_wanted chuFamilyKLT_add_supset_six_families {k l t : ℕ} (hk : 0 < k) (hl : 0 < l)
    (ht : 0 < t) :
    let P : ℤ := 8 * k * l + 8 * l + 8
    let X₁ := (Finset.Icc 1 l ×ˢ Finset.range t).image fun p : ℕ × ℕ =>
      P * p.2 + (4 * k + 4) * p.1 + 4
    let X₂ := (Finset.Icc 1 l ×ˢ Finset.range t).image fun p : ℕ × ℕ =>
      P * p.2 + (4 * k + 4) * p.1 + 8
    let X₃ := (Finset.range t).image fun j : ℕ => P * j + (4 * k * l + 4 * l) + 12
    let X₄ := (Finset.Icc 1 l ×ˢ Finset.range t).image fun p : ℕ × ℕ =>
      P * p.2 + (4 * k * l + 4 * l) + (4 * k + 4) * p.1 + 8
    let X₅ := (Finset.Icc 1 l ×ˢ Finset.range t).image fun p : ℕ × ℕ =>
      P * p.2 + (4 * k * l + 4 * l) + (4 * k + 4) * p.1 + 12
    let X₆ := (Finset.range t).image fun j : ℕ => P * j + (8 * k * l + 8 * l) + 16
    {0, 4, 8} ∪ X₁ ∪ X₂ ∪ X₃ ∪ X₄ ∪ X₅ ∪ X₆ ⊆ chuFamilyKLT k l t + chuFamilyKLT k l t ∧
      Pairwise fun a b : Fin 6 =>
        Disjoint (![X₁, X₂, X₃, X₄, X₅, X₆] a) (![X₁, X₂, X₃, X₄, X₅, X₆] b)
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Lemma 7.
Uses 1

TheoremTwo families of runs with the same sums (Proposition 1)#●ready to prove

Let \(k\), \(l\), \(t\) be natural numbers, let \(M^k\) be the block \(1, 4, \dots, 4, 3\) with \(k\) fours, and let \(B\) be the concatenation of \(l\) copies of \(M^k\). For \(j \ge 1\) let \(R_1(j)\) be the sequence \(1, 1\) followed by \(j\) copies of \(2, B, 1, 1\), and let \(R_3(j)\) be the sequence \(2\) followed by \(j\) copies of \(B, 1, 1, 2\). Then the sums of the entries of \(R_1(j)\) for \(1 \le j \le t\) form the same set as the sums of the entries of \(R_3(j)\) for \(1 \le j \le t\).

In the paper, \(R_1\) and \(R_3\) are runs of consecutive differences of the set of Lemma 2, so they give the same positive differences of that set. The paper's hypothesis \(k, l, t \ge 1\) is not needed.

public theorem_wanted chuFamilyKLT_run_sums_R1_eq_R3 (k l t : ℕ) :
    (Finset.Icc 1 t).image (fun j =>
        ([1, 1] ++ (List.replicate j
          (2 :: (List.replicate l (chuBlock k)).flatten ++ [1, 1])).flatten).sum) =
      (Finset.Icc 1 t).image (fun j =>
        (2 :: (List.replicate j
          ((List.replicate l (chuBlock k)).flatten ++ [1, 1, 2])).flatten).sum)
Sources
  • Manish Kumar, Mohan and Ram Krishna Pandey, A Conjecture of Chu et al. and a New Family of MSTD Sets, INTEGERS 24 (2024), Article A32, Proposition 1.
Uses 1
Statement usesChu difference block
7 fully proved13 ready to prove

The dependency explorer needs JavaScript and its graph data.

Download the complete graph data.