Abstract data for counterexamples at every base size #
This module contains the explicit binary permutation-module seed, arbitrary base-array criterion, a quotient-independent finite tuple-colour interface with canonical quotient realizations, symbolic colour growth, and the affine exact-base-size successor bridge used by the obstruction construction.
Faithfulness and irreducibility are intentionally absent from
EveryBaseSeed: they are used only later to prove primitivity and are not
needed for the obstruction.
Arbitrary-length base arrays #
Two tuples lie in the same orbit under the diagonal action of H.
Equations
- SaxlCounterexamples.EveryBase.SameTupleOrbit H x y = ∃ (h : H), ∀ (j : Fin n), h • x j = y j
Instances For
The tuple rows distinguish every nonidentity element of the top group.
Equations
- SaxlCounterexamples.EveryBase.TupleRowsDistinguishing H Q rows = ∀ (q : Q), (∀ (i : ι), SaxlCounterexamples.EveryBase.SameTupleOrbit H (rows (q⁻¹ • i)) (rows i)) → q = 1
Instances For
A complete finite coding of the H-orbits of base tuples.
- colour : (Fin n → V) → C
The colour assigned to a tuple.
- colour_eq_iff_sameOrbit {x y : Fin n → V} : Saxl.IsBaseTuple H V x → Saxl.IsBaseTuple H V y → (self.colour x = self.colour y ↔ SameTupleOrbit H x y)
- hits (c : C) : ∃ (x : Fin n → V), Saxl.IsBaseTuple H V x ∧ self.colour x = c
Instances For
Explicit binary permutation-module seed interface #
Exactly the data used by the abstract obstruction. Faithfulness and irreducibility are deliberately absent because the cycle-sum proof does not use them.
- Ω : Type u_1
The finite coordinate set.
- H : Type u_2
The seed group.
- V : Type u_3
The seed module.
- decidableEqOmega : DecidableEq self.Ω
- addCommGroupV : AddCommGroup self.V
- actionHV : DistribMulAction self.H self.V
- omega0 : self.Ω
The distinguished coordinate.
- u : self.V
The vector vanishing exactly at the distinguished coordinate.
- regular_exists : ∃ (v : self.V), Saxl.IsRegularVector self.H self.V v
The equivariant coordinate map into the binary permutation module.
- avoidingCycle (h : self.H) : AvoidingCycle self.H self.Ω h self.omega0
An avoiding cycle for every group element.
Instances For
Sum the binary coordinates of v over L.
Equations
- SaxlCounterexamples.EveryBase.cycleSum S L v = ∑ ω ∈ L, S.coord v ω
Instances For
Reindex an avoiding cycle by the action of its group element.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Finite regular-tuple colours and orbit profiles #
A finite colour system for the tail + 1-tuples used in a generalized
neighbourhood. firstColour is not extra mathematics: its compatibility
field says exactly that it records the ordinary orbit of the first tuple
entry. Keeping it explicit avoids quotient choice in executable files.
- C : Type u_1
Colours for regular tuples of length
tail + 1. - D : Type u_2
Colours for vector orbits.
- decidableEqC : DecidableEq self.C
- tupleCode : TupleColourCode S.H S.V (tail + 1) self.C
The regular-tuple orbit code.
- vectorCode : VectorOrbitCode S.H S.V self.D
The vector-orbit code.
Project a tuple colour to the colour of its first vector.
- firstColour_compat (x : Fin (tail + 1) → S.V) : Saxl.IsBaseTuple S.H S.V x → self.vectorCode.colour (x 0) = self.firstColour (self.tupleCode.colour x)
Instances For
Concrete finite types of all positive-length regular tuple orbits. Index
t records colours of tuples of length t + 1. Positive indexing is
essential: for a nontrivial group there are no regular zero-tuples, so a total
colour map at length zero cannot exist.
The colour type for each positive tuple length.
Finiteness of every colour type.
The orbit code at each positive tuple length.
Instances For
The number of regular-tuple colours at level n.
Equations
- T.card n = Fintype.card (T.C n)
Instances For
Choose a base-tuple representative of a colour.
Equations
- T.representative n c = Classical.choose ⋯
Instances For
Append a vector to a representative and return the resulting colour.
Equations
- T.appendColour n cv = (T.code (n + 1)).colour (Fin.snoc (T.representative n cv.1) cv.2)
Instances For
The permutation-wreath group associated to level n.
Equations
- T.LinearGroup n = Saxl.PermWreath S.H (Equiv.Perm (T.C n)) (T.C n)
Instances For
The product module associated to level n.
Equations
- T.LinearSpace n = (T.C n → S.V)
Instances For
The canonical base rows formed from all chosen representatives.
Equations
- T.baseRows n j c = T.representative n c j
Instances For
Canonical finite quotient colours #
These constructions show that the positive-length colour-tower interface is inhabited for every finite seed. Nonbase tuples receive the colour of a fixed constant regular tuple; on base tuples the colour is the actual diagonal orbit quotient.
A regular tuple of positive length n + 1.
Equations
Instances For
Orbit equivalence on regular tuples.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The quotient colour type of regular tuples under the diagonal action.
Equations
Instances For
Equations
- SaxlCounterexamples.EveryBase.regularTupleRelDecidable S n x✝¹ x✝ = Classical.propDecidable ((fun (x1 x2 : SaxlCounterexamples.EveryBase.RegularTuple S n) => x1 ≈ x2) x✝¹ x✝)
A default constant regular tuple, used to colour nonbase tuples.
Equations
- SaxlCounterexamples.EveryBase.defaultRegularTuple S n = ⟨fun (x : Fin (n + 1)) => Classical.choose ⋯, ⋯⟩
Instances For
Colour a tuple by its orbit, using the default colour when it is not a base.
Equations
- SaxlCounterexamples.EveryBase.regularTupleColour S n x = if hx : Saxl.IsBaseTuple S.H S.V x then ⟦⟨x, hx⟩⟧ else ⟦SaxlCounterexamples.EveryBase.defaultRegularTuple S n⟧
Instances For
The canonical orbit code for regular tuples of length n + 1.
Equations
- SaxlCounterexamples.EveryBase.regularTupleCode S n = { colour := SaxlCounterexamples.EveryBase.regularTupleColour S n, colour_eq_iff_sameOrbit := ⋯, hits := ⋯ }
Instances For
The canonical, genuinely inhabited positive regular-colour tower.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Orbit equivalence on vectors in the seed module.
Equations
Instances For
The quotient colour type of vector orbits.
Equations
Instances For
Equations
- SaxlCounterexamples.EveryBase.vectorOrbitRelDecidable S x✝¹ x✝ = Classical.propDecidable ((fun (x1 x2 : S.V) => x1 ≈ x2) x✝¹ x✝)
The canonical quotient code for vector orbits.
Equations
- SaxlCounterexamples.EveryBase.quotientVectorOrbitCode S = { colour := Quotient.mk (SaxlCounterexamples.EveryBase.vectorOrbitSetoid S), colour_eq_iff_sameOrbit := ⋯ }
Instances For
Project a regular-tuple colour to the orbit colour of its first vector.
Equations
- SaxlCounterexamples.EveryBase.firstVectorOrbitColour S tail = Quotient.lift (fun (x : SaxlCounterexamples.EveryBase.RegularTuple S tail) => ⟦↑x 0⟧) ⋯
Instances For
Canonical finite tuple/vector orbit colours used by the profile argument.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Exact tuple size and the affine successor bridge #
A technically convenient strengthening of Saxl.ExactBaseSize: smaller
ordered tuples are excluded even before imposing injectivity.
Equations
- SaxlCounterexamples.EveryBase.ExactTupleBaseSize G X n = ((∃ (x : Fin n → X), Saxl.IsBaseTuple G X x) ∧ ∀ m < n, ¬∃ (x : Fin m → X), Saxl.IsBaseTuple G X x)