mathlib3 documentation

topology.metric_space.antilipschitz

Antilipschitz functions #

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We say that a map f : α → β between two (extended) metric spaces is antilipschitz_with K, K ≥ 0, if for all x, y we have edist x y ≤ K * edist (f x) (f y). For a metric space, the latter inequality is equivalent to dist x y ≤ K * dist (f x) (f y).

Implementation notes #

The parameter K has type ℝ≥0. This way we avoid conjuction in the definition and have coercions both to and ℝ≥0∞. We do not require 0 < K in the definition, mostly because we do not have a posreal type.

def antilipschitz_with {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] (K : nnreal) (f : α β) :
Prop

We say that f : α → β is antilipschitz_with K if for any two points x, y we have edist x y ≤ K * edist (f x) (f y).

Equations
theorem antilipschitz_with.edist_lt_top {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} (h : antilipschitz_with K f) (x y : α) :
theorem antilipschitz_with.edist_ne_top {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} (h : antilipschitz_with K f) (x y : α) :
theorem antilipschitz_with_iff_le_mul_nndist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} :
theorem antilipschitz_with.le_mul_nndist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} :

Alias of the forward direction of antilipschitz_with_iff_le_mul_nndist.

theorem antilipschitz_with.of_le_mul_nndist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} :
( (x y : α), has_nndist.nndist x y K * has_nndist.nndist (f x) (f y)) antilipschitz_with K f

Alias of the reverse direction of antilipschitz_with_iff_le_mul_nndist.

theorem antilipschitz_with_iff_le_mul_dist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} :
antilipschitz_with K f (x y : α), has_dist.dist x y K * has_dist.dist (f x) (f y)
theorem antilipschitz_with.le_mul_dist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} :
antilipschitz_with K f (x y : α), has_dist.dist x y K * has_dist.dist (f x) (f y)

Alias of the forward direction of antilipschitz_with_iff_le_mul_dist.

theorem antilipschitz_with.of_le_mul_dist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} :
( (x y : α), has_dist.dist x y K * has_dist.dist (f x) (f y)) antilipschitz_with K f

Alias of the reverse direction of antilipschitz_with_iff_le_mul_dist.

theorem antilipschitz_with.mul_le_nndist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (x y : α) :
theorem antilipschitz_with.mul_le_dist {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (x y : α) :
@[protected, nolint]
def antilipschitz_with.K {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) :

Extract the constant from hf : antilipschitz_with K f. This is useful, e.g., if K is given by a long formula, and we want to reuse this value.

Equations
  • hf.K = K
@[protected]
theorem antilipschitz_with.injective {α : Type u_1} {β : Type u_2} [emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) :
theorem antilipschitz_with.mul_le_edist {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (x y : α) :
theorem antilipschitz_with.ediam_preimage_le {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (s : set β) :
theorem antilipschitz_with.le_mul_ediam_image {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (s : set α) :
@[protected]
theorem antilipschitz_with.comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} [pseudo_emetric_space α] [pseudo_emetric_space β] [pseudo_emetric_space γ] {Kg : nnreal} {g : β γ} (hg : antilipschitz_with Kg g) {Kf : nnreal} {f : α β} (hf : antilipschitz_with Kf f) :
antilipschitz_with (Kf * Kg) (g f)
theorem antilipschitz_with.restrict {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (s : set α) :
theorem antilipschitz_with.cod_restrict {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) {s : set β} (hs : (x : α), f x s) :
theorem antilipschitz_with.to_right_inv_on' {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} {s : set α} (hf : antilipschitz_with K (s.restrict f)) {g : β α} {t : set β} (g_maps : set.maps_to g t s) (g_inv : set.right_inv_on g f t) :
theorem antilipschitz_with.to_right_inv_on {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) {g : β α} {t : set β} (h : set.right_inv_on g f t) :
theorem antilipschitz_with.to_right_inverse {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) {g : β α} (hg : function.right_inverse g f) :
@[protected]
@[protected]
theorem antilipschitz_with.uniform_embedding {α : Type u_1} {β : Type u_2} [emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) (hfc : uniform_continuous f) :
theorem antilipschitz_with.closed_embedding {α : Type u_1} {β : Type u_2} [emetric_space α] [emetric_space β] {K : nnreal} {f : α β} [complete_space α] (hf : antilipschitz_with K f) (hfc : uniform_continuous f) :
@[protected]
theorem antilipschitz_with.subsingleton {α : Type u_1} {β : Type u_2} [emetric_space α] [pseudo_emetric_space β] {f : α β} (h : antilipschitz_with 0 f) :

If f : α → β is 0-antilipschitz, then α is a subsingleton.

theorem antilipschitz_with.bounded_preimage {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [pseudo_metric_space β] {K : nnreal} {f : α β} (hf : antilipschitz_with K f) {s : set β} (hs : metric.bounded s) :
@[protected]
theorem antilipschitz_with.proper_space {β : Type u_2} [pseudo_metric_space β] {α : Type u_1} [metric_space α] {K : nnreal} {f : α β} [proper_space α] (hK : antilipschitz_with K f) (f_cont : continuous f) (hf : function.surjective f) :

The image of a proper space under an expanding onto map is proper.

theorem lipschitz_with.to_right_inverse {α : Type u_1} {β : Type u_2} [pseudo_emetric_space α] [pseudo_emetric_space β] {K : nnreal} {f : α β} (hf : lipschitz_with K f) {g : β α} (hg : function.right_inverse g f) :
@[protected]
theorem lipschitz_with.proper_space {α : Type u_1} {β : Type u_2} [pseudo_metric_space α] [metric_space β] [proper_space β] {K : nnreal} {f : α ≃ₜ β} (hK : lipschitz_with K f) :

The preimage of a proper space under a Lipschitz homeomorphism is proper.