Documentation

Mathlib.Analysis.Normed.Group.Continuity

Continuity of the norm on (semi)groups #

Tags #

normed group

theorem tendsto_iff_norm_div_tendsto_zero {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {f : αE} {a : Filter α} {b : E} :
Filter.Tendsto f a (nhds b) Filter.Tendsto (fun (e : α) => f e / b) a (nhds 0)
theorem tendsto_iff_norm_sub_tendsto_zero {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {f : αE} {a : Filter α} {b : E} :
Filter.Tendsto f a (nhds b) Filter.Tendsto (fun (e : α) => f e - b) a (nhds 0)
theorem tendsto_one_iff_norm_tendsto_zero {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {f : αE} {a : Filter α} :
Filter.Tendsto f a (nhds 1) Filter.Tendsto (fun (x : α) => f x) a (nhds 0)
theorem tendsto_zero_iff_norm_tendsto_zero {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {f : αE} {a : Filter α} :
Filter.Tendsto f a (nhds 0) Filter.Tendsto (fun (x : α) => f x) a (nhds 0)
theorem squeeze_one_norm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {f : αE} {a : α} {t₀ : Filter α} (h : ∀ᶠ (n : α) in t₀, f n a n) (h' : Filter.Tendsto a t₀ (nhds 0)) :
Filter.Tendsto f t₀ (nhds 1)

Special case of the sandwich theorem: if the norm of f is eventually bounded by a real function a which tends to 0, then f tends to 1 (neutral element of SeminormedGroup). In this pair of lemmas (squeeze_one_norm' and squeeze_one_norm), following a convention of similar lemmas in Topology.MetricSpace.Basic and Topology.Algebra.Order, the ' version is phrased using "eventually" and the non-' version is phrased absolutely.

theorem squeeze_zero_norm' {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {f : αE} {a : α} {t₀ : Filter α} (h : ∀ᶠ (n : α) in t₀, f n a n) (h' : Filter.Tendsto a t₀ (nhds 0)) :
Filter.Tendsto f t₀ (nhds 0)

Special case of the sandwich theorem: if the norm of f is eventually bounded by a real function a which tends to 0, then f tends to 0. In this pair of lemmas (squeeze_zero_norm' and squeeze_zero_norm), following a convention of similar lemmas in Topology.MetricSpace.Pseudo.Defs and Topology.Algebra.Order, the ' version is phrased using "eventually" and the non-' version is phrased absolutely.

theorem squeeze_one_norm {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {f : αE} {a : α} {t₀ : Filter α} (h : ∀ (n : α), f n a n) :
Filter.Tendsto a t₀ (nhds 0)Filter.Tendsto f t₀ (nhds 1)

Special case of the sandwich theorem: if the norm of f is bounded by a real function a which tends to 0, then f tends to 1.

theorem squeeze_zero_norm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {f : αE} {a : α} {t₀ : Filter α} (h : ∀ (n : α), f n a n) :
Filter.Tendsto a t₀ (nhds 0)Filter.Tendsto f t₀ (nhds 0)

Special case of the sandwich theorem: if the norm of f is bounded by a real function a which tends to 0, then f tends to 0.

theorem tendsto_norm_div_self {E : Type u_5} [SeminormedGroup E] (x : E) :
Filter.Tendsto (fun (a : E) => a / x) (nhds x) (nhds 0)
theorem tendsto_norm_sub_self {E : Type u_5} [SeminormedAddGroup E] (x : E) :
Filter.Tendsto (fun (a : E) => a - x) (nhds x) (nhds 0)
theorem tendsto_norm_div_self_nhdsGE {E : Type u_5} [SeminormedGroup E] (x : E) :
Filter.Tendsto (fun (a : E) => a / x) (nhds x) (nhdsWithin 0 (Set.Ici 0))
theorem tendsto_norm_sub_self_nhdsGE {E : Type u_5} [SeminormedAddGroup E] (x : E) :
Filter.Tendsto (fun (a : E) => a - x) (nhds x) (nhdsWithin 0 (Set.Ici 0))
theorem tendsto_norm' {E : Type u_5} [SeminormedGroup E] {x : E} :
Filter.Tendsto (fun (a : E) => a) (nhds x) (nhds x)
theorem tendsto_norm {E : Type u_5} [SeminormedAddGroup E] {x : E} :
Filter.Tendsto (fun (a : E) => a) (nhds x) (nhds x)
theorem tendsto_norm_one {E : Type u_5} [SeminormedGroup E] :
Filter.Tendsto (fun (a : E) => a) (nhds 1) (nhds 0)

See tendsto_norm_one for a version with pointed neighborhoods.

theorem tendsto_norm_zero {E : Type u_5} [SeminormedAddGroup E] :
Filter.Tendsto (fun (a : E) => a) (nhds 0) (nhds 0)

See tendsto_norm_zero for a version with pointed neighborhoods.

theorem continuous_norm' {E : Type u_5} [SeminormedGroup E] :
Continuous fun (a : E) => a
theorem continuous_norm {E : Type u_5} [SeminormedAddGroup E] :
Continuous fun (a : E) => a
theorem continuous_nnnorm' {E : Type u_5} [SeminormedGroup E] :
Continuous fun (a : E) => a‖₊
theorem continuous_nnnorm {E : Type u_5} [SeminormedAddGroup E] :
Continuous fun (a : E) => a‖₊
theorem continuous_enorm' {E : Type u_5} [SeminormedGroup E] :
Continuous fun (a : E) => a‖ₑ
theorem continuous_enorm {E : Type u_5} [SeminormedAddGroup E] :
Continuous fun (a : E) => a‖ₑ
theorem Inseparable.norm_eq_norm' {E : Type u_5} [SeminormedGroup E] {u v : E} (h : Inseparable u v) :
theorem Inseparable.norm_eq_norm {E : Type u_5} [SeminormedAddGroup E] {u v : E} (h : Inseparable u v) :
theorem closure_one_eq {E : Type u_5} [SeminormedGroup E] :
closure {1} = {x : E | x = 0}
theorem Filter.Tendsto.norm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {a : E} {l : Filter α} {f : αE} (h : Tendsto f l (nhds a)) :
Tendsto (fun (x : α) => f x) l (nhds a)
theorem Filter.Tendsto.norm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {a : E} {l : Filter α} {f : αE} (h : Tendsto f l (nhds a)) :
Tendsto (fun (x : α) => f x) l (nhds a)
theorem Filter.Tendsto.nnnorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {a : E} {l : Filter α} {f : αE} (h : Tendsto f l (nhds a)) :
Tendsto (fun (x : α) => f x‖₊) l (nhds a‖₊)
theorem Filter.Tendsto.nnnorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {a : E} {l : Filter α} {f : αE} (h : Tendsto f l (nhds a)) :
Tendsto (fun (x : α) => f x‖₊) l (nhds a‖₊)
theorem Filter.Tendsto.enorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {a : E} {l : Filter α} {f : αE} (h : Tendsto f l (nhds a)) :
Tendsto (fun (x : α) => f x‖ₑ) l (nhds a‖ₑ)
theorem Filter.Tendsto.enorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {a : E} {l : Filter α} {f : αE} (h : Tendsto f l (nhds a)) :
Tendsto (fun (x : α) => f x‖ₑ) l (nhds a‖ₑ)
theorem Continuous.norm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} :
Continuous fContinuous fun (x : α) => f x
theorem Continuous.norm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} :
Continuous fContinuous fun (x : α) => f x
theorem Continuous.nnnorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} :
Continuous fContinuous fun (x : α) => f x‖₊
theorem Continuous.nnnorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} :
Continuous fContinuous fun (x : α) => f x‖₊
theorem Continuous.enorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} :
Continuous fContinuous fun (x : α) => f x‖ₑ
theorem Continuous.enorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} :
Continuous fContinuous fun (x : α) => f x‖ₑ
theorem ContinuousAt.norm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {a : α} (h : ContinuousAt f a) :
ContinuousAt (fun (x : α) => f x) a
theorem ContinuousAt.norm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {a : α} (h : ContinuousAt f a) :
ContinuousAt (fun (x : α) => f x) a
theorem ContinuousAt.nnnorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {a : α} (h : ContinuousAt f a) :
ContinuousAt (fun (x : α) => f x‖₊) a
theorem ContinuousAt.nnnorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {a : α} (h : ContinuousAt f a) :
ContinuousAt (fun (x : α) => f x‖₊) a
theorem ContinuousAt.enorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {a : α} (h : ContinuousAt f a) :
ContinuousAt (fun (x : α) => f x‖ₑ) a
theorem ContinuousAt.enorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {a : α} (h : ContinuousAt f a) :
ContinuousAt (fun (x : α) => f x‖ₑ) a
theorem ContinuousWithinAt.norm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {s : Set α} {a : α} (h : ContinuousWithinAt f s a) :
ContinuousWithinAt (fun (x : α) => f x) s a
theorem ContinuousWithinAt.norm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {s : Set α} {a : α} (h : ContinuousWithinAt f s a) :
ContinuousWithinAt (fun (x : α) => f x) s a
theorem ContinuousWithinAt.nnnorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {s : Set α} {a : α} (h : ContinuousWithinAt f s a) :
ContinuousWithinAt (fun (x : α) => f x‖₊) s a
theorem ContinuousWithinAt.nnnorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {s : Set α} {a : α} (h : ContinuousWithinAt f s a) :
ContinuousWithinAt (fun (x : α) => f x‖₊) s a
theorem ContinuousWithinAt.enorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {s : Set α} {a : α} (h : ContinuousWithinAt f s a) :
ContinuousWithinAt (fun (x : α) => f x‖ₑ) s a
theorem ContinuousWithinAt.enorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {s : Set α} {a : α} (h : ContinuousWithinAt f s a) :
ContinuousWithinAt (fun (x : α) => f x‖ₑ) s a
theorem ContinuousOn.norm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {s : Set α} (h : ContinuousOn f s) :
ContinuousOn (fun (x : α) => f x) s
theorem ContinuousOn.norm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {s : Set α} (h : ContinuousOn f s) :
ContinuousOn (fun (x : α) => f x) s
theorem ContinuousOn.nnnorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {s : Set α} (h : ContinuousOn f s) :
ContinuousOn (fun (x : α) => f x‖₊) s
theorem ContinuousOn.nnnorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {s : Set α} (h : ContinuousOn f s) :
ContinuousOn (fun (x : α) => f x‖₊) s
theorem ContinuousOn.enorm' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] [TopologicalSpace α] {f : αE} {s : Set α} (h : ContinuousOn f s) :
ContinuousOn (fun (x : α) => f x‖ₑ) s
theorem ContinuousOn.enorm {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] [TopologicalSpace α] {f : αE} {s : Set α} (h : ContinuousOn f s) :
ContinuousOn (fun (x : α) => f x‖ₑ) s
theorem eventually_ne_of_tendsto_norm_atTop' {α : Type u_2} {E : Type u_5} [SeminormedGroup E] {l : Filter α} {f : αE} (h : Filter.Tendsto (fun (y : α) => f y) l Filter.atTop) (x : E) :
∀ᶠ (y : α) in l, f y x

If ‖y‖ → ∞, then we can assume y ≠ x for any fixed x.

theorem eventually_ne_of_tendsto_norm_atTop {α : Type u_2} {E : Type u_5} [SeminormedAddGroup E] {l : Filter α} {f : αE} (h : Filter.Tendsto (fun (y : α) => f y) l Filter.atTop) (x : E) :
∀ᶠ (y : α) in l, f y x

If ‖y‖→∞, then we can assume y≠x for any fixed x

theorem SeminormedCommGroup.mem_closure_iff {E : Type u_5} [SeminormedGroup E] {s : Set E} {a : E} :
a closure s ∀ (ε : ), 0 < εbs, a / b < ε
theorem SeminormedAddCommGroup.mem_closure_iff {E : Type u_5} [SeminormedAddGroup E] {s : Set E} {a : E} :
a closure s ∀ (ε : ), 0 < εbs, a - b < ε
theorem SeminormedGroup.tendstoUniformlyOn_one {ι : Type u_3} {κ : Type u_4} {G : Type u_7} [SeminormedGroup G] {f : ικG} {s : Set κ} {l : Filter ι} :
TendstoUniformlyOn f 1 l s ε > 0, ∀ᶠ (i : ι) in l, xs, f i x < ε
theorem SeminormedAddGroup.tendstoUniformlyOn_zero {ι : Type u_3} {κ : Type u_4} {G : Type u_7} [SeminormedAddGroup G] {f : ικG} {s : Set κ} {l : Filter ι} :
TendstoUniformlyOn f 0 l s ε > 0, ∀ᶠ (i : ι) in l, xs, f i x < ε
theorem SeminormedGroup.uniformCauchySeqOnFilter_iff_tendstoUniformlyOnFilter_one {ι : Type u_3} {κ : Type u_4} {G : Type u_7} [SeminormedGroup G] {f : ικG} {l : Filter ι} {l' : Filter κ} :
UniformCauchySeqOnFilter f l l' TendstoUniformlyOnFilter (fun (n : ι × ι) (z : κ) => f n.1 z / f n.2 z) 1 (l ×ˢ l) l'
theorem SeminormedAddGroup.uniformCauchySeqOnFilter_iff_tendstoUniformlyOnFilter_zero {ι : Type u_3} {κ : Type u_4} {G : Type u_7} [SeminormedAddGroup G] {f : ικG} {l : Filter ι} {l' : Filter κ} :
UniformCauchySeqOnFilter f l l' TendstoUniformlyOnFilter (fun (n : ι × ι) (z : κ) => f n.1 z - f n.2 z) 0 (l ×ˢ l) l'
theorem SeminormedGroup.uniformCauchySeqOn_iff_tendstoUniformlyOn_one {ι : Type u_3} {κ : Type u_4} {G : Type u_7} [SeminormedGroup G] {f : ικG} {s : Set κ} {l : Filter ι} :
UniformCauchySeqOn f l s TendstoUniformlyOn (fun (n : ι × ι) (z : κ) => f n.1 z / f n.2 z) 1 (l ×ˢ l) s
theorem SeminormedAddGroup.uniformCauchySeqOn_iff_tendstoUniformlyOn_zero {ι : Type u_3} {κ : Type u_4} {G : Type u_7} [SeminormedAddGroup G] {f : ικG} {s : Set κ} {l : Filter ι} :
UniformCauchySeqOn f l s TendstoUniformlyOn (fun (n : ι × ι) (z : κ) => f n.1 z - f n.2 z) 0 (l ×ˢ l) s
theorem controlled_prod_of_mem_closure {E : Type u_5} [SeminormedCommGroup E] {a : E} {s : Subgroup E} (hg : a closure s) {b : } (b_pos : ∀ (n : ), 0 < b n) :
∃ (v : E), Filter.Tendsto (fun (n : ) => iFinset.range (n + 1), v i) Filter.atTop (nhds a) (∀ (n : ), v n s) v 0 / a < b 0 ∀ (n : ), 0 < nv n < b n
theorem controlled_sum_of_mem_closure {E : Type u_5} [SeminormedAddCommGroup E] {a : E} {s : AddSubgroup E} (hg : a closure s) {b : } (b_pos : ∀ (n : ), 0 < b n) :
∃ (v : E), Filter.Tendsto (fun (n : ) => iFinset.range (n + 1), v i) Filter.atTop (nhds a) (∀ (n : ), v n s) v 0 - a < b 0 ∀ (n : ), 0 < nv n < b n
theorem controlled_prod_of_mem_closure_range {E : Type u_5} {F : Type u_6} [SeminormedCommGroup E] [SeminormedCommGroup F] {j : E →* F} {b : F} (hb : b closure j.range) {f : } (b_pos : ∀ (n : ), 0 < f n) :
∃ (a : E), Filter.Tendsto (fun (n : ) => iFinset.range (n + 1), j (a i)) Filter.atTop (nhds b) j (a 0) / b < f 0 ∀ (n : ), 0 < nj (a n) < f n
theorem controlled_sum_of_mem_closure_range {E : Type u_5} {F : Type u_6} [SeminormedAddCommGroup E] [SeminormedAddCommGroup F] {j : E →+ F} {b : F} (hb : b closure j.range) {f : } (b_pos : ∀ (n : ), 0 < f n) :
∃ (a : E), Filter.Tendsto (fun (n : ) => iFinset.range (n + 1), j (a i)) Filter.atTop (nhds b) j (a 0) - b < f 0 ∀ (n : ), 0 < nj (a n) < f n

See tendsto_norm_one for a version with full neighborhoods.

See tendsto_norm_zero for a version with full neighborhoods.

@[deprecated tendsto_norm_nhdsNE_zero (since := "2024-12-22")]

Alias of tendsto_norm_nhdsNE_zero.


See tendsto_norm_zero for a version with full neighborhoods.

@[deprecated tendsto_norm_nhdsNE_one (since := "2024-12-22")]

Alias of tendsto_norm_nhdsNE_one.


See tendsto_norm_one for a version with full neighborhoods.

@[deprecated tendsto_norm_nhdsNE_zero (since := "2024-12-22")]

Alias of tendsto_norm_nhdsNE_zero.


See tendsto_norm_zero for a version with full neighborhoods.

@[deprecated tendsto_norm_nhdsNE_one (since := "2024-12-22")]

Alias of tendsto_norm_nhdsNE_one.


See tendsto_norm_one for a version with full neighborhoods.

theorem tendsto_norm_div_self_nhdsNE {E : Type u_5} [NormedGroup E] (a : E) :
Filter.Tendsto (fun (x : E) => x / a) (nhdsWithin a {a}) (nhdsWithin 0 (Set.Ioi 0))
theorem tendsto_norm_sub_self_nhdsNE {E : Type u_5} [NormedAddGroup E] (a : E) :
Filter.Tendsto (fun (x : E) => x - a) (nhdsWithin a {a}) (nhdsWithin 0 (Set.Ioi 0))
@[deprecated tendsto_norm_sub_self_nhdsNE (since := "2024-12-22")]
theorem tendsto_norm_sub_self_punctured_nhds {E : Type u_5} [NormedAddGroup E] (a : E) :
Filter.Tendsto (fun (x : E) => x - a) (nhdsWithin a {a}) (nhdsWithin 0 (Set.Ioi 0))

Alias of tendsto_norm_sub_self_nhdsNE.

@[deprecated tendsto_norm_div_self_nhdsNE (since := "2024-12-22")]
theorem tendsto_norm_div_self_punctured_nhds {E : Type u_5} [NormedGroup E] (a : E) :
Filter.Tendsto (fun (x : E) => x / a) (nhdsWithin a {a}) (nhdsWithin 0 (Set.Ioi 0))

Alias of tendsto_norm_div_self_nhdsNE.

A version of comap_norm_nhdsGT_zero for a multiplicative normed group.

@[deprecated comap_norm_nhdsGT_zero (since := "2024-12-22")]

Alias of comap_norm_nhdsGT_zero.

@[deprecated comap_norm_nhdsGT_zero' (since := "2024-12-22")]

Alias of comap_norm_nhdsGT_zero'.


A version of comap_norm_nhdsGT_zero for a multiplicative normed group.