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Mathlib.LinearAlgebra.Dimension.Constructions

Rank of various constructions #

Main statements #

For free modules, we have

Lemmas for ranks of submodules and subalgebras are also provided. We have finrank variants for most lemmas as well.

theorem rank_quotient_add_rank_le {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [Nontrivial R] (M' : Submodule R M) :
theorem rank_quotient_le {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] (p : Submodule R M) :
theorem rank_quotient_eq_of_le_torsion {R : Type u_2} {M : Type u_3} [CommRing R] [AddCommGroup M] [Module R M] {M' : Submodule R M} (hN : M' Submodule.torsion R M) :
@[simp]
theorem rank_add_rank_le_rank_prod (R : Type u) (M : Type v) {M₁ : Type v} [Ring R] [AddCommGroup M] [AddCommGroup M₁] [Module R M] [Module R M₁] [Nontrivial R] :
Module.rank R M + Module.rank R M₁ Module.rank R (M × M₁)
@[simp]

If M and M' are free, then the rank of M × M' is (Module.rank R M).lift + (Module.rank R M').lift.

theorem rank_prod' {R : Type u} {M : Type v} {M₁ : Type v} [Ring R] [AddCommGroup M] [AddCommGroup M₁] [Module R M] [Module R M₁] [StrongRankCondition R] [Module.Free R M] [Module.Free R M₁] :
Module.rank R (M × M₁) = Module.rank R M + Module.rank R M₁

If M and M' are free (and lie in the same universe), the rank of M × M' is (Module.rank R M) + (Module.rank R M').

@[simp]

The finrank of M × M' is (finrank R M) + (finrank R M').

theorem rank_finsupp' (R : Type u) (M : Type v) [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] [Module.Free R M] (ι : Type v) :

The rank of (ι →₀ R) is (#ι).lift.

theorem rank_finsupp_self' (R : Type u) [Ring R] [StrongRankCondition R] {ι : Type u} :

If R and ι lie in the same universe, the rank of (ι →₀ R) is # ι.

@[simp]
theorem rank_directSum (R : Type u) [Ring R] [StrongRankCondition R] {ι : Type v} (M : ιType w) [(i : ι) → AddCommGroup (M i)] [(i : ι) → Module R (M i)] [∀ (i : ι), Module.Free R (M i)] :
Module.rank R (DirectSum ι fun (i : ι) => M i) = Cardinal.sum fun (i : ι) => Module.rank R (M i)

The rank of the direct sum is the sum of the ranks.

@[simp]

If m and n are Fintype, the rank of m × n matrices is (#m).lift * (#n).lift.

@[simp]

If m and n are Fintype that lie in the same universe, the rank of m × n matrices is (#n * #m).lift.

theorem rank_matrix'' (R : Type u) [Ring R] [StrongRankCondition R] (m : Type u) (n : Type u) [Finite m] [Finite n] :

If m and n are Fintype that lie in the same universe as R, the rank of m × n matrices is # m * # n.

@[simp]

The finrank of (ι →₀ R) is Fintype.card ι.

@[simp]
theorem FiniteDimensional.finrank_directSum (R : Type u) [Ring R] [StrongRankCondition R] {ι : Type v} [Fintype ι] (M : ιType w) [(i : ι) → AddCommGroup (M i)] [(i : ι) → Module R (M i)] [∀ (i : ι), Module.Free R (M i)] [∀ (i : ι), Module.Finite R (M i)] :
FiniteDimensional.finrank R (DirectSum ι fun (i : ι) => M i) = Finset.sum Finset.univ fun (i : ι) => FiniteDimensional.finrank R (M i)

The finrank of the direct sum is the sum of the finranks.

If m and n are Fintype, the finrank of m × n matrices is (Fintype.card m) * (Fintype.card n).

@[simp]
theorem rank_pi {R : Type u} {η : Type u₁'} {φ : ηType u_1} [Ring R] [StrongRankCondition R] [(i : η) → AddCommGroup (φ i)] [(i : η) → Module R (φ i)] [∀ (i : η), Module.Free R (φ i)] [Finite η] :
Module.rank R ((i : η) → φ i) = Cardinal.sum fun (i : η) => Module.rank R (φ i)

The rank of a finite product of free modules is the sum of the ranks.

The finrank of (ι → R) is Fintype.card ι.

theorem FiniteDimensional.finrank_pi_fintype (R : Type u) [Ring R] [StrongRankCondition R] {ι : Type v} [Fintype ι] {M : ιType w} [(i : ι) → AddCommGroup (M i)] [(i : ι) → Module R (M i)] [∀ (i : ι), Module.Free R (M i)] [∀ (i : ι), Module.Finite R (M i)] :
FiniteDimensional.finrank R ((i : ι) → M i) = Finset.sum Finset.univ fun (i : ι) => FiniteDimensional.finrank R (M i)

The finrank of a finite product is the sum of the finranks.

theorem rank_fun {R : Type u} [Ring R] [StrongRankCondition R] {M : Type u} {η : Type u} [Fintype η] [AddCommGroup M] [Module R M] [Module.Free R M] :
Module.rank R (ηM) = (Fintype.card η) * Module.rank R M
theorem rank_fun_eq_lift_mul {R : Type u} {M : Type v} {η : Type u₁'} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] [Module.Free R M] [Fintype η] :
theorem rank_fun' {R : Type u} {η : Type u₁'} [Ring R] [StrongRankCondition R] [Fintype η] :
Module.rank R (ηR) = (Fintype.card η)
theorem rank_fin_fun {R : Type u} [Ring R] [StrongRankCondition R] (n : ) :
Module.rank R (Fin nR) = n
@[simp]

The vector space of functions on a Fintype ι has finrank equal to the cardinality of ι.

The vector space of functions on Fin n has finrank equal to n.

def finDimVectorspaceEquiv {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] [Module.Free R M] (n : ) (hn : Module.rank R M = n) :
M ≃ₗ[R] Fin nR

An n-dimensional R-vector space is equivalent to Fin n → R.

Equations
Instances For
    @[simp]

    The rank of M ⊗[R] M' is (Module.rank R M).lift * (Module.rank R M').lift.

    theorem rank_tensorProduct' {S : Type u} {M : Type v} {M₁ : Type v} [CommRing S] [AddCommGroup M] [AddCommGroup M₁] [StrongRankCondition S] [Module S M] [Module.Free S M] [Module S M₁] [Module.Free S M₁] :

    If M and M' lie in the same universe, the rank of M ⊗[R] M' is (Module.rank R M) * (Module.rank R M').

    @[simp]

    The finrank of M ⊗[R] M' is (finrank R M) * (finrank R M').

    theorem Submodule.lt_of_le_of_finrank_lt_finrank {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] {s : Submodule R M} {t : Submodule R M} (le : s t) (lt : FiniteDimensional.finrank R s < FiniteDimensional.finrank R t) :
    s < t

    The dimension of a submodule is bounded by the dimension of the ambient space.

    The dimension of a quotient is bounded by the dimension of the ambient space.

    theorem Submodule.finrank_map_le {R : Type u} {M : Type v} {M' : Type v'} [Ring R] [AddCommGroup M] [AddCommGroup M'] [Module R M] [Module R M'] [StrongRankCondition R] (f : M →ₗ[R] M') (p : Submodule R M) [Module.Finite R p] :

    Pushforwards of finite submodules have a smaller finrank.

    theorem rank_span_le {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] (s : Set M) :
    theorem rank_span_finset_le {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] (s : Finset M) :
    Module.rank R (Submodule.span R s) s.card
    noncomputable def Set.finrank (R : Type u) {M : Type v} [Ring R] [AddCommGroup M] [Module R M] (s : Set M) :

    The rank of a set of vectors as a natural number.

    Equations
    Instances For
      theorem finrank_span_finset_le_card {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] (s : Finset M) :
      Set.finrank R s s.card
      theorem finrank_range_le_card {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] {ι : Type u_2} [Fintype ι] (b : ιM) :
      theorem finrank_span_eq_card {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] [Nontrivial R] {ι : Type u_2} [Fintype ι] {b : ιM} (hb : LinearIndependent R b) :
      theorem finrank_span_set_eq_card {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] {s : Set M} [Fintype s] (hs : LinearIndependent (ι := { x : M // x s }) R Subtype.val) :
      theorem finrank_span_finset_eq_card {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] {s : Finset M} (hs : LinearIndependent R Subtype.val) :
      theorem span_lt_of_subset_of_card_lt_finrank {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] {s : Set M} [Fintype s] {t : Submodule R M} (subset : s t) (card_lt : (Set.toFinset s).card < FiniteDimensional.finrank R t) :
      theorem span_lt_top_of_card_lt_finrank {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] [StrongRankCondition R] {s : Set M} [Fintype s] (card_lt : (Set.toFinset s).card < FiniteDimensional.finrank R M) :
      @[simp]
      theorem Subalgebra.rank_toSubmodule {F : Type u_2} {E : Type u_3} [CommRing F] [Ring E] [Algebra F E] (S : Subalgebra F E) :
      Module.rank F (Subalgebra.toSubmodule S) = Module.rank F S
      @[simp]
      theorem Subalgebra.finrank_toSubmodule {F : Type u_2} {E : Type u_3} [CommRing F] [Ring E] [Algebra F E] (S : Subalgebra F E) :
      FiniteDimensional.finrank F (Subalgebra.toSubmodule S) = FiniteDimensional.finrank F S
      theorem Subalgebra.rank_top {F : Type u_2} {E : Type u_3} [CommRing F] [Ring E] [Algebra F E] :
      @[simp]
      theorem Subalgebra.rank_bot {F : Type u_2} {E : Type u_3} [CommRing F] [Ring E] [Algebra F E] [StrongRankCondition F] [NoZeroSMulDivisors F E] [Nontrivial E] :