diff --git a/FormalConjectures/Wikipedia/EulerBrick.lean b/FormalConjectures/Wikipedia/EulerBrick.lean index c74a2867c..ba1a504f2 100644 --- a/FormalConjectures/Wikipedia/EulerBrick.lean +++ b/FormalConjectures/Wikipedia/EulerBrick.lean @@ -13,7 +13,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. -/ - import FormalConjectures.Util.ProblemImports /-! @@ -22,6 +21,7 @@ import FormalConjectures.Util.ProblemImports *References:* - [Wikipedia](https://en.wikipedia.org/wiki/Euler_brick) - [stackexchange](https://math.stackexchange.com/questions/2264401/euler-bricks-and-the-4th-dimension) +- [Sh12] Shapirov, Ruslan. Perfect cuboids and irreducible polynomials. https://arxiv.org/abs/1108.5348 -/ namespace EulerBrick @@ -30,42 +30,112 @@ namespace EulerBrick An **Euler brick** is a rectangular cuboid where all edges and face diagonals have integer lengths. -/ def IsEulerBrick (a b c : ℕ+) : Prop := - IsSquare (a^2 + b^2) ∧ IsSquare (a^2 + c^2) ∧ IsSquare (b^2 + c^2) +IsSquare (a^2 + b^2) ∧ IsSquare (a^2 + c^2) ∧ IsSquare (b^2 + c^2) /-- A **perfect cuboid** is an Euler brick with an integer space diagonal. -/ def IsPerfectCuboid (a b c : ℕ+) : Prop := - IsEulerBrick a b c ∧ IsSquare (a^2 + b^2 + c^2) +IsEulerBrick a b c ∧ IsSquare (a^2 + b^2 + c^2) /-- Generalization of an Euler brick to $n$-dimensional space. -/ def IsEulerHyperBrick (n : ℕ) (sides : Fin n → ℕ+) : Prop := - Pairwise fun i j ↦ IsSquare ((sides i)^2 + (sides j)^2) +Pairwise fun i j ↦ IsSquare ((sides i)^2 + (sides j)^2) /-- Is there a perfect Euler brick? -/ @[category research open, AMS 11] theorem perfect_euler_brick_existence : - answer(sorry) ↔ ∃ a b c : ℕ+, IsPerfectCuboid a b c := by - sorry +answer(sorry) ↔ ∃ a b c : ℕ+, IsPerfectCuboid a b c := by +sorry /-- Is there an Euler brick in $4$-dimensional space? -/ @[category research open, AMS 11] theorem four_dim_euler_brick_existence : - answer(sorry) ↔ ∃ sides : Fin 4 → ℕ+, IsEulerHyperBrick 4 sides:= by - sorry +answer(sorry) ↔ ∃ sides : Fin 4 → ℕ+, IsEulerHyperBrick 4 sides:= by +sorry /-- Is there an Euler brick in $n$-dimensional space for any $n > 3$? -/ @[category research open, AMS 11] theorem n_dim_euler_brick_existence : - answer(sorry) ↔ ∀ n > 3, ∃ sides : Fin n → ℕ+, IsEulerHyperBrick n sides := by +answer(sorry) ↔ ∀ n > 3, ∃ sides : Fin n → ℕ+, IsEulerHyperBrick n sides := by +sorry + +section Cuboid + +open Polynomial + +/-! **Cuboid conjectures**: +The three Cuboid conjectures ask if certain families of polynomials are always irreducible. +If all hold, this implies the nonexistence of a perfect Euler brick. +-/ + +/-- Pairs of natural numbers for which the first Cuboid polynomial is irreducible. -/ +def CuboidOneFor (a b : ℤ) : Prop := + Irreducible (X ^ 8 + C (6 * (a ^ 2 - b ^ 2)) * X ^ 6 + + C (b ^ 4 - 4 * a ^ 2 * b ^ 2 + a ^ 4) * X ^ 4 + - C (6 * a ^ 2 * b ^ 2 * (a ^ 2 - b ^ 2)) * X ^ 2 + C (a ^ 4 * b ^ 4)) + +/-- *First Cuboid conjecture*: For all positive coprime integers $a$, $b$ with $a ≠ b$, +the polynomial of the first Cuboid polynomial is irreducible. -/ +def CuboidOne : Prop := ∀ ⦃a b : ℤ⦄, gcd a b = 1 → 0 < a → 0 < b → a ≠ b → CuboidOneFor a b + +/-- The first Cuboid conjecture -/ +@[category research open, AMS 12] +theorem cuboidOne : CuboidOne := by sorry + +/-- Pairs of natural numbers for which the second Cuboid polynomial is irreducible. -/ +def CuboidTwoFor (a b : ℤ) : Prop := + Irreducible (X ^ 10 + C ((2 * b ^ 2 + a ^ 2) * (3 * b ^ 2 - 2 * a ^ 2)) * X ^ 8 + + C ((b ^ 8 + 10 * a ^ 2 * b ^ 6 + 4 * a ^ 4 * b ^ 4 - 14 * a ^ 6 * b ^ 2 + a ^ 8)) * X ^ 6 + - C (a ^ 2 * b ^ 2 * (b ^ 8 - 14 * a ^ 2 * b ^ 6 + + 4 * a ^ 4 * b ^ 4 + 10 * a ^ 6 * b ^ 2 + a ^ 8)) + * X ^ 4 - C (a ^ 6 * b ^ 6 * (b ^ 2 + 2 * a ^ 2) * (-2 * b ^ 2 + 3 * a ^ 2)) + * X ^ 2 - C (b ^ 10 * a ^ 10)) + +/-- *Second Cuboid conjecture*: For all positive coprime integers $a$, $b$ with $a ≠ b$, +the polynomial of the second Cuboid polynomial is irreducible. -/ +def CuboidTwo : Prop := ∀ ⦃a b : ℕ⦄, a.Coprime b → 0 < a → 0 < b → a ≠ b → CuboidTwoFor a b + +/-- The second Cuboid conjecture -/ +@[category research open, AMS 12] +theorem cuboidTwo : CuboidTwo := by sorry + +/-- Triplets of natural numbers for which the third Cuboid polynomial is irreducible. -/ +def CuboidThreeFor (a b c : ℤ) : Prop := + Irreducible (X ^ 12 + C (6 * c ^ 2 - 2 * a ^ 2 - 2 * b ^ 2) * X ^ 10 + + C (c ^ 4 + b ^ 4 + a ^ 4 + 4 * a ^ 2 * c ^ 2 + 4 * b ^ 2 * c ^ 2 - 12 * b ^ 2 * a ^ 2) + * X ^ 8 + C (6 * a ^ 4 * c ^ 2 + 6 * c ^ 2 * b ^ 4 - 8 * a ^ 2 * b ^ 2 * c ^ 2 + - 2 * c ^ 4 * a ^ 2 - 2 * c ^ 4 * b ^ 2 - 2 * a ^ 4 * b ^ 2 - 2 * b ^ 4 * a ^ 2) + * X ^ 6 + C (4 * c ^ 2 * b ^ 4 * a ^ 2 + 4 * a ^ 4 * c ^ 2 * b ^ 2 + - 12 * c ^ 4 * a ^ 2 * b ^ 2 + c ^ 4 * a ^ 4 + c ^ 4 * b ^ 4 + a ^ 4 * b ^ 4) * X ^ 4 + + C (6 * a ^ 4 * c ^ 2 * b ^ 4 - 2 * c ^ 4 * a ^ 4 * b ^ 2 - 2 * c ^ 4 * a ^ 2 * b ^ 4) + * X ^ 2 + C (c ^ 4 * a ^ 4 * b ^ 4)) + +/-- *Third Cuboid conjecture*: +For all positive, pairwise different coprime integers $a, b, c$ with $b * c ≠ a ^ 2$ +and $a * c ≠ b ^ 2$, the polynomial of the third Cuboid polynomial is irreducible. -/ +def CuboidThree : Prop := ∀ ⦃a b c : ℤ⦄, gcd a (gcd b c) = 1 → 0 < a → 0 < b → + 0 < c → a ≠ b → b ≠ c → c ≠ a → b * c ≠ a ^ 2 → a * c ≠ b ^ 2 → CuboidThreeFor a b c + +/-- The third Cuboid conjecture -/ +@[category research open, AMS 12] +theorem cuboidThree : CuboidThree := by sorry + +/-- In [Sh12], Ruslan notes that a perfect Euler brick does not exist +if all three Cuboid conjectures hold. -/ +@[category research solved, AMS 12] +theorem cuboid_perfect_euler_brick (h₁ : CuboidOne) (h₂ : CuboidTwo) (h₃ : CuboidThree) : + ¬ ∃ a b c : ℕ+, IsPerfectCuboid a b c := by sorry +end Cuboid + end EulerBrick