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10 changes: 5 additions & 5 deletions Archive/Wiedijk100Theorems/SolutionOfCubicQuartic.lean
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Expand Up @@ -23,14 +23,14 @@ terms of a quantity that is a root of a particular cubic equation.
## Main statements

- `cubic_eq_zero_iff`: gives the roots of the cubic equation
where the discriminant `p = 3 * a * c - b^2` is nonzero.
where the discriminant `p = 3 * a * c - b^2` is nonzero.
- `cubic_eq_zero_iff_of_p_eq_zero`: gives the roots of the cubic equation
where the discriminant equals zero.
where the discriminant equals zero.
- `quartic_eq_zero_iff`: gives the roots of the quartic equation
where the quantity `b^3 - 4 * a * b * c + 8 * a^2 * d` is nonzero, in terms of a root `u`
to a cubic resolvent.
where the quantity `b^3 - 4 * a * b * c + 8 * a^2 * d` is nonzero, in terms of a root `u`
to a cubic resolvent.
- `quartic_eq_zero_iff_of_q_eq_zero`: gives the roots of the quartic equation
where the quantity `b^3 - 4 * a * b * c + 8 * a^2 * d` equals zero.
where the quantity `b^3 - 4 * a * b * c + 8 * a^2 * d` equals zero.

## Proof outline

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6 changes: 3 additions & 3 deletions Counterexamples/NowhereDifferentiable.lean
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Expand Up @@ -24,7 +24,7 @@ which is the original bound given by Karl Weierstrass. There is a better bound $
## References

* [Weierstrass, Karl, *Über continuirliche Functionen eines reellen Arguments, die für keinen Werth
des letzeren einen bestimmten Differentialquotienten besitzen*][weierstrass1895]
des letzeren einen bestimmten Differentialquotienten besitzen*][weierstrass1895]
* [G. H. Hardy, *Weierstrass's Non-Differentiable Function*][hardyweierstrass]

-/
Expand Down Expand Up @@ -77,8 +77,8 @@ theorem uniformContinuous_weierstrass {a : ℝ} (ha : a ∈ Set.Ioo 0 1) (b :
To show that Weierstrass function $f(x)$ is not differentiable at any $x$, we choose a sequence
$\{x_m\}$ such that, as $m\to\infty$
- $\{x_m\}$ converges to $x$
- The slope $(f(x_m) - f(x)) / (x_m - x)$ grows unbounded
which means the derivative $f'(x)$ cannot exist.
- The slope $(f(x_m) - f(x)) / (x_m - x)$ grows unbounded,
which means the derivative $f'(x)$ cannot exist.
-/

/-- The approximating sequence `seq` is defined as $x_m = \lfloor b^m x + 3/2 \rfloor / b^m$ -/
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4 changes: 2 additions & 2 deletions Mathlib/Combinatorics/HalesJewett.lean
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Expand Up @@ -51,10 +51,10 @@ allows us to work directly with `α`, `Option α`, `(ι → α) → κ`, and `ι
## TODO

- Prove a finitary version of Van der Waerden's theorem (either by compactness or by modifying the
current proof).
current proof).

- One could reformulate the proof of Hales-Jewett to give explicit upper bounds on the number of
coordinates needed.
coordinates needed.

## Tags

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8 changes: 4 additions & 4 deletions Mathlib/Combinatorics/Quiver/Arborescence.lean
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Expand Up @@ -20,12 +20,12 @@ that for every `b : V` there is a unique path from `root` to `b`.
- `Quiver.Arborescence V`: a typeclass asserting that `V` is an arborescence
- `arborescenceMk`: a convenient way of proving that a quiver is an arborescence
- `RootedConnected r`: a typeclass asserting that there is at least one path from `r` to `b` for
every `b`.
every `b`.
- `geodesicSubtree r`: given `[RootedConnected r]`, this is a subquiver of `V` which contains
just enough edges to include a shortest path from `r` to `b` for every `b`.
just enough edges to include a shortest path from `r` to `b` for every `b`.
- `geodesicArborescence : Arborescence (geodesicSubtree r)`: an instance saying that the geodesic
subtree is an arborescence. This proves the directed analogue of 'every connected graph has a
spanning tree'. This proof avoids the use of Zorn's lemma.
subtree is an arborescence. This proves the directed analogue of 'every connected graph has a
spanning tree'. This proof avoids the use of Zorn's lemma.
-/

@[expose] public section
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2 changes: 1 addition & 1 deletion Mathlib/Combinatorics/Quiver/ConnectedComponent.lean
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Expand Up @@ -20,7 +20,7 @@ We define:
* `Quiver.IsStronglyConnected V`: every pair of vertices is connected by a (possibly empty) path.
* `Quiver.IsSStronglyConnected V`: every pair of vertices is connected by a path of positive length.
* `Quiver.StronglyConnectedComponent V`: the quotient by the equivalence relation “paths in both
directions”.
directions”.

These concepts relate strong and weak connectivity and let us reason about strongly connected
components in directed graphs.
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16 changes: 8 additions & 8 deletions Mathlib/GroupTheory/GroupAction/Iwasawa.lean
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Expand Up @@ -11,9 +11,9 @@ public import Mathlib.GroupTheory.Subgroup.Simple

/-! # Iwasawa criterion for simplicity

- `IwasawaStructure` : the structure underlying the Iwasawa criterion
For a group `G`, this consists of an action of `G` on a type `α` and,
for every `a : α`, of a subgroup `T a`, such that the following properties hold:
- `IwasawaStructure` : the structure underlying the Iwasawa criterion.
For a group `G`, this consists of an action of `G` on a type `α` and,
for every `a : α`, of a subgroup `T a`, such that the following properties hold:
- for all `a`, `T a` is commutative
- for all `g : G` and `a : α`, `T (g • a) = MulAut.conj g • T a`
- the subgroups `T a` generate `G`
Expand All @@ -22,12 +22,12 @@ We then prove two versions of the Iwasawa criterion when
there is an Iwasawa structure.

- `IwasawaStructure.commutator_le` asserts that if the action of `G` on `α`
is quasiprimitive, then every normal subgroup that acts nontrivially
contains `commutator G`
is quasiprimitive, then every normal subgroup that acts nontrivially
contains `commutator G`.

- `IwasawaStructure.isSimpleGroup` : the Iwasawa criterion for simplicity
If the action of `G` on `α` is quasiprimitive and faithful,
and `G` is nontrivial and perfect, then `G` is simple.
- `IwasawaStructure.isSimpleGroup` : the Iwasawa criterion for simplicity.
If the action of `G` on `α` is quasiprimitive and faithful,
and `G` is nontrivial and perfect, then `G` is simple.

## TODO

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12 changes: 6 additions & 6 deletions Mathlib/GroupTheory/GroupAction/MultiplePrimitivity.lean
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Expand Up @@ -13,9 +13,9 @@ public import Mathlib.GroupTheory.GroupAction.SubMulAction.OfFixingSubgroup
Let `G` be a group acting on a type `α`.

* `MulAction.IsMultiplyPreprimitive` :
The action is said to be `n`-primitive if, for every subset `s :
Set α` with `n` elements, the actions f `stabilizer G s` on the
complement of `s` is primitive.
The action is said to be `n`-primitive if, for every subset `s :
Set α` with `n` elements, the actions f `stabilizer G s` on the
complement of `s` is primitive.

* `MulAction.is_zero_preprimitive` : any action is 0-primitive

Expand All @@ -30,9 +30,9 @@ complement of `s` is primitive.
ofFixingSubgroup.isMultiplyPreprimitive

* `MulAction.ofFixingSubgroup.isMultiplyPreprimitive`:
If an action is `s.ncard + m`-primitive, then
the action of `FixingSubgroup G s` on the complement of `s`
is `m`-primitive.
If an action is `s.ncard + m`-primitive, then
the action of `FixingSubgroup G s` on the complement of `s`
is `m`-primitive.

-/

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52 changes: 26 additions & 26 deletions Mathlib/GroupTheory/GroupAction/SubMulAction/OfFixingSubgroup.lean
Original file line number Diff line number Diff line change
Expand Up @@ -17,51 +17,51 @@ public import Mathlib.Tactic.Group

Given a `MulAction` of `G` on `α` and `s : Set α`,

* `SubMulAction.ofFixingSubgroup` is the action
- `SubMulAction.ofFixingSubgroup` is the action
of `FixingSubgroup G s` on the complement `sᶜ` of `s`.

- We define equivariant maps that relate various of these `SubMulAction`s
and permit to manipulate them in a relatively smooth way:
and permit to manipulate them in a relatively smooth way:

* `SubMulAction.ofFixingSubgroup_equivariantMap`:
the identity map from `sᶜ` to `α`, as an equivariant map
relative to the injection of `FixingSubgroup G s` into `G`.
the identity map from `sᶜ` to `α`, as an equivariant map
relative to the injection of `FixingSubgroup G s` into `G`.

* `SubMulAction.fixingSubgroupInsertEquiv M a s` : the
multiplicative equivalence between `fixingSubgroup M (insert a s)`
and `fixingSubgroup (stabilizer M a) s`
* `SubMulAction.fixingSubgroupInsertEquiv M a s`: the
multiplicative equivalence between `fixingSubgroup M (insert a s)`
and `fixingSubgroup (stabilizer M a) s`

* `SubMulAction.ofFixingSubgroup_insert_map` : the equivariant
map between `SubMulAction.ofFixingSubgroup M (Set.insert a s)`
and `SubMulAction.ofFixingSubgroup (MulAction.stabilizer M a) s`.
* `SubMulAction.ofFixingSubgroup_insert_map`: the equivariant
map between `SubMulAction.ofFixingSubgroup M (Set.insert a s)`
and `SubMulAction.ofFixingSubgroup (MulAction.stabilizer M a) s`.

* `SubMulAction.fixingSubgroupEquivFixingSubgroup`:
the multiplicative equivalence between `SubMulAction.ofFixingSubgroup M s`
and `SubMulAction.ofFixingSubgroup M t` induced by `g : M`
such that `g • t = s`.
the multiplicative equivalence between `SubMulAction.ofFixingSubgroup M s`
and `SubMulAction.ofFixingSubgroup M t` induced by `g : M`
such that `g • t = s`.

* `SubMulAction.conjMap_ofFixingSubgroup`:
the equivariant map between `SubMulAction.ofFixingSubgroup M t`
and `SubMulAction.ofFixingSubgroup M s`
induced by `g : M` such that `g • t = s`.
the equivariant map between `SubMulAction.ofFixingSubgroup M t`
and `SubMulAction.ofFixingSubgroup M s`
induced by `g : M` such that `g • t = s`.

* `SubMulAction.ofFixingSubgroup_of_inclusion`:
the identity from `SubMulAction.ofFixingSubgroup M s`
to `SubMulAction.ofFixingSubgroup M t`, when `t ⊆ s`,
as an equivariant map.
the identity from `SubMulAction.ofFixingSubgroup M s`
to `SubMulAction.ofFixingSubgroup M t`, when `t ⊆ s`,
as an equivariant map.

* `SubMulAction.ofFixingSubgroup_of_singleton`:
the identity map from `SubMulAction.ofStabilizer M a`
to `SubMulAction.ofFixingSubgroup M {a}`.
the identity map from `SubMulAction.ofStabilizer M a`
to `SubMulAction.ofFixingSubgroup M {a}`.

* `SubMulAction.ofFixingSubgroup_of_eq`:
the identity from `SubMulAction.ofFixingSubgroup M s`
to `SubMulAction.ofFixingSubgroup M t`, when `s = t`,
as an equivariant map.
the identity from `SubMulAction.ofFixingSubgroup M s`
to `SubMulAction.ofFixingSubgroup M t`, when `s = t`,
as an equivariant map.

* `SubMulAction.ofFixingSubgroup.append`: appends
an enumeration of `ofFixingSubgroup M s` at the end
of an enumeration of `s`, as an equivariant map.
an enumeration of `ofFixingSubgroup M s` at the end
of an enumeration of `s`, as an equivariant map.

-/

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6 changes: 3 additions & 3 deletions Mathlib/GroupTheory/PushoutI.lean
Original file line number Diff line number Diff line change
Expand Up @@ -26,10 +26,10 @@ in the diagram are injective).

- `Monoid.PushoutI.NormalWord`: a normal form for words in the pushout
- `Monoid.PushoutI.of_injective`: if all the maps in the diagram are injective in a pushout of
groups then so is `of`
groups then so is `of`
- `Monoid.PushoutI.Reduced.eq_empty_of_mem_range`: For any word `w` in the coproduct,
if `w` is reduced (i.e none its letters are in the image of the base monoid), and nonempty, then
`w` itself is not in the image of the base monoid.
if `w` is reduced (i.e none its letters are in the image of the base monoid), and nonempty, then
`w` itself is not in the image of the base monoid.

## References

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2 changes: 1 addition & 1 deletion Mathlib/LinearAlgebra/AffineSpace/Simplex/Centroid.lean
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Expand Up @@ -28,7 +28,7 @@ of the simplex.
* `centroid` is the centroid of a simplex, defined via `Finset.univ.centroid` on its vertices.

* `faceOppositeCentroid` is the centroid of the facet obtained by removing one vertex from the
simplex.
simplex.

* `median` is the line connecting a vertex to the corresponding faceOppositeCentroid.

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4 changes: 2 additions & 2 deletions Mathlib/LinearAlgebra/Dual/BaseChange.lean
Original file line number Diff line number Diff line change
Expand Up @@ -17,10 +17,10 @@ public import Mathlib.RingTheory.TensorProduct.IsBaseChangeHom
If `f : Module.Dual R V` and `Algebra R A`, then

* `Module.Dual.baseChange A f` is the element
of `Module.Dual A (A ⊗[R] V)` deduced by base change.
of `Module.Dual A (A ⊗[R] V)` deduced by base change.

* `Module.Dual.baseChangeHom` is the `R`-linear map
given by `Module.Dual.baseChange`.
given by `Module.Dual.baseChange`.

* `IsBaseChange.dual` : for finite free modules, taking dual commutes with base change.

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4 changes: 2 additions & 2 deletions Mathlib/LinearAlgebra/Finsupp/Pi.lean
Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,9 @@ public import Mathlib.Algebra.Order.Group.Nat

* `Finsupp.linearEquivFunOnFinite`: `α →₀ β` and `a → β` are equivalent if `α` is finite
* `FunOnFinite.map`: the map `(X → M) → (Y → M)` induced by a map `f : X ⟶ Y` when
`X` and `Y` are finite.
`X` and `Y` are finite.
* `FunOnFinite.linearMmap`: the linear map `(X → M) →ₗ[R] (Y → M)` induced
by a map `f : X ⟶ Y` when `X` and `Y` are finite.
by a map `f : X ⟶ Y` when `X` and `Y` are finite.

## Tags

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2 changes: 1 addition & 1 deletion Mathlib/LinearAlgebra/Transvection.lean
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ public import Mathlib.LinearAlgebra.Dual.BaseChange
* `LinearMap.transvections R V`: the set of transvections.

* `LinearEquiv.dilatransvections R V`: the set of linear equivalences
whose associated linear map is of the form `LinearMap.transvection f v`.
whose associated linear map is of the form `LinearMap.transvection f v`.

* `LinearEquiv.transvection.det` shows that it has determinant `1`.

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4 changes: 2 additions & 2 deletions Mathlib/RepresentationTheory/FinGroupCharZero.lean
Original file line number Diff line number Diff line change
Expand Up @@ -24,9 +24,9 @@ then every object of `Rep k G` (resp. `FDRep k G`) is injective and projective.
We also give two simpleness criteria for an object `V` of `FDRep k G`, when `k` is
an algebraically closed field in which the order of `G` is invertible:
* `FDRep.simple_iff_end_is_rank_one`: `V` is simple if and only `V ⟶ V` is a `k`-vector
space of dimension `1`.
space of dimension `1`.
* `FDRep.simple_iff_char_is_norm_one`: when `k` is characteristic zero, `V` is simple
if and only if `∑ g : G, V.character g * V.character g⁻¹ = Fintype.card G`.
if and only if `∑ g : G, V.character g * V.character g⁻¹ = Fintype.card G`.

-/

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