Documentation

Mathlib.GroupTheory.GroupAction.SubMulAction

Sets invariant to a MulAction #

In this file we define SubMulAction R M; a subset of a MulAction R M which is closed with respect to scalar multiplication.

For most uses, typically Submodule R M is more powerful.

Main definitions #

Tags #

submodule, mul_action

class SMulMemClass (S : Type u_1) (R : outParam (Type u_2)) (M : Type u_3) [SMul R M] [SetLike S M] :
  • smul_mem : ∀ {s : S} (r : R) {m : M}, m sr m s

    Multiplication by a scalar on an element of the set remains in the set.

SMulMemClass S R M says S is a type of subsets s ≤ M that are closed under the scalar action of R on M.

Note that only R is marked as an outParam here, since M is supplied by the SetLike class instead.

Instances
    class VAddMemClass (S : Type u_1) (R : outParam (Type u_2)) (M : Type u_3) [VAdd R M] [SetLike S M] :
    • vadd_mem : ∀ {s : S} (r : R) {m : M}, m sr +ᵥ m s

      Addition by a scalar with an element of the set remains in the set.

    VAddMemClass S R M says S is a type of subsets s ≤ M that are closed under the additive action of R on M.

    Note that only R is marked as an outParam here, since M is supplied by the SetLike class instead.

    Instances

      Not registered as an instance because R is an outParam in SMulMemClass S R M.

      Not registered as an instance because R is an outParam in SMulMemClass S R M.

      instance SetLike.vadd {S : Type u'} {R : Type u} {M : Type v} [VAdd R M] [SetLike S M] [hS : VAddMemClass S R M] (s : S) :
      VAdd R { x // x s }

      A subset closed under the additive action inherits that action.

      Equations
      theorem SetLike.vadd.proof_1 {S : Type u_2} {R : Type u_3} {M : Type u_1} [VAdd R M] [SetLike S M] [hS : VAddMemClass S R M] (s : S) (r : R) (x : { x // x s }) :
      r +ᵥ x s
      instance SetLike.smul {S : Type u'} {R : Type u} {M : Type v} [SMul R M] [SetLike S M] [hS : SMulMemClass S R M] (s : S) :
      SMul R { x // x s }

      A subset closed under the scalar action inherits that action.

      Equations
      theorem SMulMemClass.ofIsScalarTower (S : Type u_1) (M : Type u_2) (N : Type u_3) (α : Type u_4) [SetLike S α] [SMul M N] [SMul M α] [Monoid N] [MulAction N α] [SMulMemClass S N α] [IsScalarTower M N α] :

      This can't be an instance because Lean wouldn't know how to find N, but we can still use this to manually derive SMulMemClass on specific types.

      instance SetLike.instIsScalarTower {S : Type u'} {R : Type u} {M : Type v} [SMul R M] [SetLike S M] [hS : SMulMemClass S R M] [Mul M] [MulMemClass S M] [IsScalarTower R M M] (s : S) :
      IsScalarTower R { x // x s } { x // x s }
      Equations
      instance SetLike.instSMulCommClass {S : Type u'} {R : Type u} {M : Type v} [SMul R M] [SetLike S M] [hS : SMulMemClass S R M] [Mul M] [MulMemClass S M] [SMulCommClass R M M] (s : S) :
      SMulCommClass R { x // x s } { x // x s }
      Equations
      @[simp]
      theorem SetLike.val_vadd {S : Type u'} {R : Type u} {M : Type v} [VAdd R M] [SetLike S M] [hS : VAddMemClass S R M] (s : S) (r : R) (x : { x // x s }) :
      ↑(r +ᵥ x) = r +ᵥ x
      @[simp]
      theorem SetLike.val_smul {S : Type u'} {R : Type u} {M : Type v} [SMul R M] [SetLike S M] [hS : SMulMemClass S R M] (s : S) (r : R) (x : { x // x s }) :
      ↑(r x) = r x
      @[simp]
      theorem SetLike.mk_vadd_mk {S : Type u'} {R : Type u} {M : Type v} [VAdd R M] [SetLike S M] [hS : VAddMemClass S R M] (s : S) (r : R) (x : M) (hx : x s) :
      r +ᵥ { val := x, property := hx } = { val := r +ᵥ x, property := (_ : r +ᵥ x s) }
      @[simp]
      theorem SetLike.mk_smul_mk {S : Type u'} {R : Type u} {M : Type v} [SMul R M] [SetLike S M] [hS : SMulMemClass S R M] (s : S) (r : R) (x : M) (hx : x s) :
      r { val := x, property := hx } = { val := r x, property := (_ : r x s) }
      theorem SetLike.vadd_def {S : Type u'} {R : Type u} {M : Type v} [VAdd R M] [SetLike S M] [hS : VAddMemClass S R M] (s : S) (r : R) (x : { x // x s }) :
      r +ᵥ x = { val := ↑(r +ᵥ x), property := (_ : r +ᵥ x s) }
      theorem SetLike.smul_def {S : Type u'} {R : Type u} {M : Type v} [SMul R M] [SetLike S M] [hS : SMulMemClass S R M] (s : S) (r : R) (x : { x // x s }) :
      r x = { val := ↑(r x), property := (_ : r x s) }
      @[simp]
      theorem SetLike.forall_smul_mem_iff {R : Type u_1} {M : Type u_2} {S : Type u_3} [Monoid R] [MulAction R M] [SetLike S M] [SMulMemClass S R M] {N : S} {x : M} :
      (∀ (a : R), a x N) x N
      structure SubMulAction (R : Type u) (M : Type v) [SMul R M] :
      • carrier : Set M

        The underlying set of a SubMulAction.

      • smul_mem' : ∀ (c : R) {x : M}, x s.carrierc x s.carrier

        The carrier set is closed under scalar multiplication.

      A SubMulAction is a set which is closed under scalar multiplication.

      Instances For
        instance SubMulAction.instSetLikeSubMulAction {R : Type u} {M : Type v} [SMul R M] :
        Equations
        • SubMulAction.instSetLikeSubMulAction = { coe := SubMulAction.carrier, coe_injective' := (_ : ∀ (p q : SubMulAction R M), p.carrier = q.carrierp = q) }
        @[simp]
        theorem SubMulAction.mem_carrier {R : Type u} {M : Type v} [SMul R M] {p : SubMulAction R M} {x : M} :
        x p.carrier x p
        theorem SubMulAction.ext {R : Type u} {M : Type v} [SMul R M] {p : SubMulAction R M} {q : SubMulAction R M} (h : ∀ (x : M), x p x q) :
        p = q
        def SubMulAction.copy {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) (s : Set M) (hs : s = p) :

        Copy of a sub_mul_action with a new carrier equal to the old one. Useful to fix definitional equalities.

        Equations
        Instances For
          @[simp]
          theorem SubMulAction.coe_copy {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) (s : Set M) (hs : s = p) :
          ↑(SubMulAction.copy p s hs) = s
          theorem SubMulAction.copy_eq {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) (s : Set M) (hs : s = p) :
          instance SubMulAction.instBotSubMulAction {R : Type u} {M : Type v} [SMul R M] :
          Equations
          • SubMulAction.instBotSubMulAction = { bot := { carrier := , smul_mem' := (_ : R∀ (h : M), ¬h ) } }
          Equations
          • SubMulAction.instInhabitedSubMulAction = { default := }
          theorem SubMulAction.smul_mem {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) {x : M} (r : R) (h : x p) :
          r x p
          Equations
          @[simp]
          theorem SubMulAction.val_smul {R : Type u} {M : Type v} [SMul R M] {p : SubMulAction R M} (r : R) (x : { x // x p }) :
          ↑(r x) = r x
          def SubMulAction.subtype {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) :
          { x // x p } →[R] M

          Embedding of a submodule p to the ambient space M.

          Equations
          Instances For
            @[simp]
            theorem SubMulAction.subtype_apply {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) (x : { x // x p }) :
            ↑(SubMulAction.subtype p) x = x
            theorem SubMulAction.subtype_eq_val {R : Type u} {M : Type v} [SMul R M] (p : SubMulAction R M) :
            ↑(SubMulAction.subtype p) = Subtype.val
            instance SubMulAction.SMulMemClass.toMulAction {R : Type u} {M : Type v} [Monoid R] [MulAction R M] {A : Type u_1} [SetLike A M] [hA : SMulMemClass A R M] (S' : A) :
            MulAction R { x // x S' }

            A SubMulAction of a MulAction is a MulAction.

            Equations
            def SubMulAction.SMulMemClass.subtype {R : Type u} {M : Type v} [Monoid R] [MulAction R M] {A : Type u_1} [SetLike A M] [hA : SMulMemClass A R M] (S' : A) :
            { x // x S' } →[R] M

            The natural MulActionHom over R from a SubMulAction of M to M.

            Equations
            Instances For
              @[simp]
              theorem SubMulAction.SMulMemClass.coeSubtype {R : Type u} {M : Type v} [Monoid R] [MulAction R M] {A : Type u_1} [SetLike A M] [hA : SMulMemClass A R M] (S' : A) :
              theorem SubMulAction.smul_of_tower_mem {S : Type u'} {R : Type u} {M : Type v} [Monoid R] [MulAction R M] [SMul S R] [SMul S M] [IsScalarTower S R M] (p : SubMulAction R M) (s : S) {x : M} (h : x p) :
              s x p
              instance SubMulAction.smul' {S : Type u'} {R : Type u} {M : Type v} [Monoid R] [MulAction R M] [SMul S R] [SMul S M] [IsScalarTower S R M] (p : SubMulAction R M) :
              SMul S { x // x p }
              Equations
              instance SubMulAction.isScalarTower {S : Type u'} {R : Type u} {M : Type v} [Monoid R] [MulAction R M] [SMul S R] [SMul S M] [IsScalarTower S R M] (p : SubMulAction R M) :
              IsScalarTower S R { x // x p }
              Equations
              instance SubMulAction.isScalarTower' {S : Type u'} {R : Type u} {M : Type v} [Monoid R] [MulAction R M] [SMul S R] [SMul S M] [IsScalarTower S R M] (p : SubMulAction R M) {S' : Type u_1} [SMul S' R] [SMul S' S] [SMul S' M] [IsScalarTower S' R M] [IsScalarTower S' S M] :
              IsScalarTower S' S { x // x p }
              Equations
              @[simp]
              theorem SubMulAction.val_smul_of_tower {S : Type u'} {R : Type u} {M : Type v} [Monoid R] [MulAction R M] [SMul S R] [SMul S M] [IsScalarTower S R M] (p : SubMulAction R M) (s : S) (x : { x // x p }) :
              ↑(s x) = s x
              @[simp]
              theorem SubMulAction.smul_mem_iff' {R : Type u} {M : Type v} [Monoid R] [MulAction R M] (p : SubMulAction R M) {G : Type u_1} [Group G] [SMul G R] [MulAction G M] [IsScalarTower G R M] (g : G) {x : M} :
              g x p x p
              instance SubMulAction.mulAction' {S : Type u'} {R : Type u} {M : Type v} [Monoid R] [MulAction R M] [Monoid S] [SMul S R] [MulAction S M] [IsScalarTower S R M] (p : SubMulAction R M) :
              MulAction S { x // x p }

              If the scalar product forms a MulAction, then the subset inherits this action

              Equations
              instance SubMulAction.mulAction {R : Type u} {M : Type v} [Monoid R] [MulAction R M] (p : SubMulAction R M) :
              MulAction R { x // x p }
              Equations
              theorem SubMulAction.val_image_orbit {R : Type u} {M : Type v} [Monoid R] [MulAction R M] {p : SubMulAction R M} (m : { x // x p }) :
              Subtype.val '' MulAction.orbit R m = MulAction.orbit R m

              Orbits in a SubMulAction coincide with orbits in the ambient space.

              Stabilizers in monoid SubMulAction coincide with stabilizers in the ambient space

              theorem SubMulAction.stabilizer_of_subMul {R : Type u} {M : Type v} [Group R] [MulAction R M] {p : SubMulAction R M} (m : { x // x p }) :

              Stabilizers in group SubMulAction coincide with stabilizers in the ambient space

              theorem SubMulAction.zero_mem {R : Type u} {M : Type v} [Semiring R] [AddCommMonoid M] [Module R M] (p : SubMulAction R M) (h : Set.Nonempty p) :
              0 p

              If the scalar product forms a Module, and the SubMulAction is not , then the subset inherits the zero.

              Equations
              • One or more equations did not get rendered due to their size.
              theorem SubMulAction.neg_mem {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] (p : SubMulAction R M) {x : M} (hx : x p) :
              -x p
              @[simp]
              theorem SubMulAction.neg_mem_iff {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] (p : SubMulAction R M) {x : M} :
              -x p x p
              @[simp]
              theorem SubMulAction.val_neg {R : Type u} {M : Type v} [Ring R] [AddCommGroup M] [Module R M] (p : SubMulAction R M) (x : { x // x p }) :
              ↑(-x) = -x
              theorem SubMulAction.smul_mem_iff {S : Type u'} {R : Type u} {M : Type v} [GroupWithZero S] [Monoid R] [MulAction R M] [SMul S R] [MulAction S M] [IsScalarTower S R M] (p : SubMulAction R M) {s : S} {x : M} (s0 : s 0) :
              s x p x p