Documentation

Mathlib.Topology.Instances.Real

Topological properties of ℝ #

theorem Real.isTopologicalBasis_Ioo_rat :
TopologicalSpace.IsTopologicalBasis (⋃ (a : ℚ), ⋃ (b : ℚ), ⋃ (_ : a < b), {Set.Ioo ↑a ↑b})
@[simp]
theorem Real.cobounded_eq :
Bornology.cobounded ℝ = Filter.atBot ⊔ Filter.atTop
@[simp]
theorem Real.cocompact_eq :
Filter.cocompact ℝ = Filter.atBot ⊔ Filter.atTop
theorem Real.mem_closure_iff {s : Set ℝ} {x : ℝ} :
x ∈ closure s ↔ ∀ ε > 0, ∃ y ∈ s, |y - x| < ε
theorem Real.uniformContinuous_inv (s : Set ℝ) {r : ℝ} (r0 : 0 < r) (H : ∀ x ∈ s, r ≤ |x|) :
UniformContinuous fun (p : ↑s) => (↑p)⁻¹
@[deprecated HasContinuousInv₀.continuousAt_inv₀]
theorem Real.tendsto_inv {r : ℝ} (r0 : r ≠ 0) :
Filter.Tendsto (fun (q : ℝ) => q⁻¹) (nhds r) (nhds r⁻¹)
theorem Real.continuous_inv :
Continuous fun (a : { r : ℝ // r ≠ 0 }) => (↑a)⁻¹
@[deprecated Continuous.inv₀]
theorem Real.Continuous.inv {α : Type u} [TopologicalSpace α] {f : α → ℝ} (h : ∀ (a : α), f a ≠ 0) (hf : Continuous f) :
Continuous fun (a : α) => (f a)⁻¹
theorem Real.uniformContinuous_mul (s : Set (ℝ × ℝ)) {r₁ : ℝ} {r₂ : ℝ} (H : ∀ x ∈ s, |x.1| < r₁ ∧ |x.2| < r₂) :
UniformContinuous fun (p : ↑s) => (↑p).1 * (↑p).2
@[deprecated continuous_mul]
theorem Real.continuous_mul :
Continuous fun (p : ℝ × ℝ) => p.1 * p.2
theorem closure_of_rat_image_lt {q : ℚ} :
closure (Rat.cast '' {x : ℚ | q < x}) = {r : ℝ | ↑q ≤ r}
theorem Function.Periodic.compact_of_continuous {α : Type u} [TopologicalSpace α] {f : ℝ → α} {c : ℝ} (hp : Function.Periodic f c) (hc : c ≠ 0) (hf : Continuous f) :

A continuous, periodic function has compact range.

@[deprecated Function.Periodic.compact_of_continuous]
theorem Function.Periodic.compact_of_continuous' {α : Type u} [TopologicalSpace α] {f : ℝ → α} {c : ℝ} (hp : Function.Periodic f c) (hc : 0 < c) (hf : Continuous f) :
theorem Function.Periodic.isBounded_of_continuous {α : Type u} [PseudoMetricSpace α] {f : ℝ → α} {c : ℝ} (hp : Function.Periodic f c) (hc : c ≠ 0) (hf : Continuous f) :

A continuous, periodic function is bounded.

theorem Int.tendsto_coe_cofinite :
Filter.Tendsto Int.cast Filter.cofinite (Filter.cocompact ℝ)

Under the coercion from ℤ to ℝ, inverse images of compact sets are finite.

theorem Int.tendsto_zmultiplesHom_cofinite {a : ℝ} (ha : a ≠ 0) :
Filter.Tendsto (⇑((zmultiplesHom ℝ) a)) Filter.cofinite (Filter.cocompact ℝ)

For nonzero a, the "multiples of a" map zmultiplesHom from ℤ to ℝ is discrete, i.e. inverse images of compact sets are finite.

The subgroup "multiples of a" (zmultiples a) is a discrete subgroup of ℝ, i.e. its intersection with compact sets is finite.