mathlib documentation

topology.algebra.ordered.liminf_limsup

Lemmas about liminf and limsup in an order topology. #

theorem filter.tendsto.is_bounded_under_le {α : Type u} {β : Type v} [semilattice_sup α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} (h : filter.tendsto u f (𝓝 a)) :
theorem filter.tendsto.is_cobounded_under_ge {α : Type u} {β : Type v} [semilattice_sup α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} [f.ne_bot] (h : filter.tendsto u f (𝓝 a)) :
theorem is_bounded_ge_nhds {α : Type u} [semilattice_inf α] [topological_space α] [order_topology α] (a : α) :
theorem filter.tendsto.is_bounded_under_ge {α : Type u} {β : Type v} [semilattice_inf α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} (h : filter.tendsto u f (𝓝 a)) :
theorem filter.tendsto.is_cobounded_under_le {α : Type u} {β : Type v} [semilattice_inf α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} [f.ne_bot] (h : filter.tendsto u f (𝓝 a)) :
theorem lt_mem_sets_of_Limsup_lt {α : Type u} [conditionally_complete_linear_order α] {f : filter α} {b : α} (h : filter.is_bounded has_le.le f) (l : f.Limsup < b) :
∀ᶠ (a : α) in f, a < b
theorem gt_mem_sets_of_Liminf_gt {α : Type u} [conditionally_complete_linear_order α] {f : filter α} {b : α} :
filter.is_bounded ge fb < f.Liminf(∀ᶠ (a : α) in f, b < a)
theorem le_nhds_of_Limsup_eq_Liminf {α : Type u} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] {f : filter α} {a : α} (hl : filter.is_bounded has_le.le f) (hg : filter.is_bounded ge f) (hs : f.Limsup = a) (hi : f.Liminf = a) :
f 𝓝 a

If the liminf and the limsup of a filter coincide, then this filter converges to their common value, at least if the filter is eventually bounded above and below.

theorem Limsup_nhds {α : Type u} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] (a : α) :
(𝓝 a).Limsup = a
theorem Liminf_nhds {α : Type u} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] (a : α) :
(𝓝 a).Liminf = a
theorem Liminf_eq_of_le_nhds {α : Type u} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] {f : filter α} {a : α} [f.ne_bot] (h : f 𝓝 a) :
f.Liminf = a

If a filter is converging, its limsup coincides with its limit.

theorem Limsup_eq_of_le_nhds {α : Type u} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] {f : filter α} {a : α} [f.ne_bot] :
f 𝓝 af.Limsup = a

If a filter is converging, its liminf coincides with its limit.

theorem filter.tendsto.limsup_eq {α : Type u} {β : Type v} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} [f.ne_bot] (h : filter.tendsto u f (𝓝 a)) :
f.limsup u = a

If a function has a limit, then its limsup coincides with its limit.

theorem filter.tendsto.liminf_eq {α : Type u} {β : Type v} [conditionally_complete_linear_order α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} [f.ne_bot] (h : filter.tendsto u f (𝓝 a)) :
f.liminf u = a

If a function has a limit, then its liminf coincides with its limit.

theorem tendsto_of_liminf_eq_limsup {α : Type u} {β : Type v} [complete_linear_order α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} (hinf : f.liminf u = a) (hsup : f.limsup u = a) :

If the liminf and the limsup of a function coincide, then the limit of the function exists and has the same value

theorem tendsto_of_le_liminf_of_limsup_le {α : Type u} {β : Type v} [complete_linear_order α] [topological_space α] [order_topology α] {f : filter β} {u : β → α} {a : α} (hinf : a f.liminf u) (hsup : f.limsup u a) :

If a number a is less than or equal to the liminf of a function f at some filter and is greater than or equal to the limsup of f, then f tends to a along this filter.