The sequence , three sumfree classes covering , and four sumfree sets covering
DefinitionClassicalSchurValuesThis bundle records the explicit finite objects of the note from which the lower bounds and are obtained.
- The sequence (Lean
seqW) of length and sum , displayed below (note, §2). - Three finite sets of positive integers (Lean
classesW, indexed by ; note, Lemma 2): , and . - Four subsets of (Lean
partitionZ7Z7, indexed by ; called in Theorem 5 of the note), each with elements, listed in the table.
| set | elements |
|---|---|
| (0,2) (0,5) (1,4) (2,3) (2,4) (3,2) (3,3) (4,4) (4,5) (5,3) (5,4) (6,3) | |
| (1,1) (1,3) (1,5) (1,6) (3,0) (3,5) (4,0) (4,2) (6,1) (6,2) (6,4) (6,6) | |
| (0,3) (0,4) (1,0) (1,2) (2,1) (2,6) (3,4) (4,3) (5,1) (5,6) (6,0) (6,5) | |
| (0,1) (0,6) (2,0) (2,2) (2,5) (3,1) (3,6) (4,1) (4,6) (5,0) (5,2) (5,5) |
The sequence and, by Lemma 1 of the note, its set of block sums are
where ; so has elements. In the note, are sumfree and partition (Lemma 2), so ; and are sumfree in and partition its nonzero elements (Theorem 5).
The sequence with the classes is the witness for . The four sets , through the lift of the Lift bundle, give .
Formalization Note The classes are Lean Finsets indexed by Fin 3 and Fin 4. The bundle contains only the data. The facts that the mission uses (the sumfree property of and their cover of , the bound on the sum of the first entries of for , and the sumfree property of the in the group and their cover of the nonzero elements) are proved inside the proofs of the theorems that use them. The disjointness of the classes, which the note also states, is not needed there.
-- Generated from lean/ClassicalSchur/Values.lean by skeleton
-- subtraction: every declaration except the def-material below is deleted,
-- and project imports are rewritten to their platform Definitions bundles.
import Mathlib
namespace ClassicalSchur
/-- The sequence `W` of the note: length 15, sum 31. -/
def seqW : List ℕ := [1, 1, 1, 6, 1, 1, 1, 7, 1, 1, 1, 6, 1, 1, 1]
/-- The classes `C₀, C₁, C₂` of Lemma 2 of the note. -/
def classesW : Fin 3 → Finset ℕ :=
![{1, 3, 8, 12, 18, 22, 28}, {2, 6, 7, 10, 11, 25, 26, 29, 30},
{9, 13, 16, 17, 19, 20, 21, 27, 31}]
/-- The four sets of Theorem 5 of the note: a partition of the nonzero
elements of `ℤ₇ × ℤ₇` into sets that are sumfree in the group. -/
def partitionZ7Z7 : Fin 4 → Finset (ZMod 7 × ZMod 7) :=
![{(0, 2), (0, 5), (1, 4), (2, 3), (2, 4), (3, 2), (3, 3), (4, 4), (4, 5), (5, 3), (5, 4),
(6, 3)},
{(1, 1), (1, 3), (1, 5), (1, 6), (3, 0), (3, 5), (4, 0), (4, 2), (6, 1), (6, 2), (6, 4),
(6, 6)},
{(0, 3), (0, 4), (1, 0), (1, 2), (2, 1), (2, 6), (3, 4), (4, 3), (5, 1), (5, 6), (6, 0),
(6, 5)},
{(0, 1), (0, 6), (2, 0), (2, 2), (2, 5), (3, 1), (3, 6), (4, 1), (4, 6), (5, 0), (5, 2),
(5, 5)}]
end ClassicalSchur