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Theorem List for Metamath Proof Explorer - 31701-31800   *Has distinct variable group(s)
TypeLabelDescription
Statement

Theoremsubfacval 31701* The subfactorial is defined as the number of derangements (see derangval 31695) of the set (1...𝑁). (Contributed by Mario Carneiro, 21-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑁 ∈ ℕ0 → (𝑆𝑁) = (𝐷‘(1...𝑁)))

Theoremderangen2 31702* Write the derangement number in terms of the subfactorial. (Contributed by Mario Carneiro, 22-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝐴 ∈ Fin → (𝐷𝐴) = (𝑆‘(♯‘𝐴)))

Theoremsubfacf 31703* The subfactorial is a function from nonnegative integers to nonnegative integers. (Contributed by Mario Carneiro, 19-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       𝑆:ℕ0⟶ℕ0

Theoremsubfaclefac 31704* The subfactorial is less than the factorial. (Contributed by Mario Carneiro, 19-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑁 ∈ ℕ0 → (𝑆𝑁) ≤ (!‘𝑁))

Theoremsubfac0 31705* The subfactorial at zero. (Contributed by Mario Carneiro, 19-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑆‘0) = 1

Theoremsubfac1 31706* The subfactorial at one. (Contributed by Mario Carneiro, 19-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑆‘1) = 0

Theoremsubfacp1lem1 31707* Lemma for subfacp1 31714. The set 𝐾 together with {1, 𝑀} partitions the set 1...(𝑁 + 1). (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}    &   (𝜑𝑁 ∈ ℕ)    &   (𝜑𝑀 ∈ (2...(𝑁 + 1)))    &   𝑀 ∈ V    &   𝐾 = ((2...(𝑁 + 1)) ∖ {𝑀})       (𝜑 → ((𝐾 ∩ {1, 𝑀}) = ∅ ∧ (𝐾 ∪ {1, 𝑀}) = (1...(𝑁 + 1)) ∧ (♯‘𝐾) = (𝑁 − 1)))

Theoremsubfacp1lem2a 31708* Lemma for subfacp1 31714. Properties of a bijection on 𝐾 augmented with the two-element flip to get a bijection on 𝐾 ∪ {1, 𝑀}. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}    &   (𝜑𝑁 ∈ ℕ)    &   (𝜑𝑀 ∈ (2...(𝑁 + 1)))    &   𝑀 ∈ V    &   𝐾 = ((2...(𝑁 + 1)) ∖ {𝑀})    &   𝐹 = (𝐺 ∪ {⟨1, 𝑀⟩, ⟨𝑀, 1⟩})    &   (𝜑𝐺:𝐾1-1-onto𝐾)       (𝜑 → (𝐹:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ (𝐹‘1) = 𝑀 ∧ (𝐹𝑀) = 1))

Theoremsubfacp1lem2b 31709* Lemma for subfacp1 31714. Properties of a bijection on 𝐾 augmented with the two-element flip to get a bijection on 𝐾 ∪ {1, 𝑀}. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}    &   (𝜑𝑁 ∈ ℕ)    &   (𝜑𝑀 ∈ (2...(𝑁 + 1)))    &   𝑀 ∈ V    &   𝐾 = ((2...(𝑁 + 1)) ∖ {𝑀})    &   𝐹 = (𝐺 ∪ {⟨1, 𝑀⟩, ⟨𝑀, 1⟩})    &   (𝜑𝐺:𝐾1-1-onto𝐾)       ((𝜑𝑋𝐾) → (𝐹𝑋) = (𝐺𝑋))

Theoremsubfacp1lem3 31710* Lemma for subfacp1 31714. In subfacp1lem6 31713 we cut up the set of all derangements on 1...(𝑁 + 1) first according to the value at 1, and then by whether or not (𝑓‘(𝑓‘1)) = 1. In this lemma, we show that the subset of all 𝑁 + 1 derangements that satisfy this for fixed 𝑀 = (𝑓‘1) is in bijection with 𝑁 − 1 derangements, by simply dropping the 𝑥 = 1 and 𝑥 = 𝑀 points from the function to get a derangement on 𝐾 = (1...(𝑁 − 1)) ∖ {1, 𝑀}. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}    &   (𝜑𝑁 ∈ ℕ)    &   (𝜑𝑀 ∈ (2...(𝑁 + 1)))    &   𝑀 ∈ V    &   𝐾 = ((2...(𝑁 + 1)) ∖ {𝑀})    &   𝐵 = {𝑔𝐴 ∣ ((𝑔‘1) = 𝑀 ∧ (𝑔𝑀) = 1)}    &   𝐶 = {𝑓 ∣ (𝑓:𝐾1-1-onto𝐾 ∧ ∀𝑦𝐾 (𝑓𝑦) ≠ 𝑦)}       (𝜑 → (♯‘𝐵) = (𝑆‘(𝑁 − 1)))

Theoremsubfacp1lem4 31711* Lemma for subfacp1 31714. The function 𝐹, which swaps 1 with 𝑀 and leaves all other elements alone, is a bijection of order 2, i.e. it is its own inverse. (Contributed by Mario Carneiro, 19-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}    &   (𝜑𝑁 ∈ ℕ)    &   (𝜑𝑀 ∈ (2...(𝑁 + 1)))    &   𝑀 ∈ V    &   𝐾 = ((2...(𝑁 + 1)) ∖ {𝑀})    &   𝐵 = {𝑔𝐴 ∣ ((𝑔‘1) = 𝑀 ∧ (𝑔𝑀) ≠ 1)}    &   𝐹 = (( I ↾ 𝐾) ∪ {⟨1, 𝑀⟩, ⟨𝑀, 1⟩})       (𝜑𝐹 = 𝐹)

Theoremsubfacp1lem5 31712* Lemma for subfacp1 31714. In subfacp1lem6 31713 we cut up the set of all derangements on 1...(𝑁 + 1) first according to the value at 1, and then by whether or not (𝑓‘(𝑓‘1)) = 1. In this lemma, we show that the subset of all 𝑁 + 1 derangements with (𝑓‘(𝑓‘1)) ≠ 1 for fixed 𝑀 = (𝑓‘1) is in bijection with derangements of 2...(𝑁 + 1), because pre-composing with the function 𝐹 swaps 1 and 𝑀 and turns the function into a bijection with (𝑓‘1) = 1 and (𝑓𝑥) ≠ 𝑥 for all other 𝑥, so dropping the point at 1 yields a derangement on the 𝑁 remaining points. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}    &   (𝜑𝑁 ∈ ℕ)    &   (𝜑𝑀 ∈ (2...(𝑁 + 1)))    &   𝑀 ∈ V    &   𝐾 = ((2...(𝑁 + 1)) ∖ {𝑀})    &   𝐵 = {𝑔𝐴 ∣ ((𝑔‘1) = 𝑀 ∧ (𝑔𝑀) ≠ 1)}    &   𝐹 = (( I ↾ 𝐾) ∪ {⟨1, 𝑀⟩, ⟨𝑀, 1⟩})    &   𝐶 = {𝑓 ∣ (𝑓:(2...(𝑁 + 1))–1-1-onto→(2...(𝑁 + 1)) ∧ ∀𝑦 ∈ (2...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}       (𝜑 → (♯‘𝐵) = (𝑆𝑁))

Theoremsubfacp1lem6 31713* Lemma for subfacp1 31714. By induction, we cut up the set of all derangements on 𝑁 + 1 according to the 𝑁 possible values of (𝑓‘1) (since (𝑓‘1) ≠ 1), and for each set for fixed 𝑀 = (𝑓‘1), the subset of derangements with (𝑓𝑀) = 1 has size 𝑆(𝑁 − 1) (by subfacp1lem3 31710), while the subset with (𝑓𝑀) ≠ 1 has size 𝑆(𝑁) (by subfacp1lem5 31712). Adding it all up yields the desired equation 𝑁(𝑆(𝑁) + 𝑆(𝑁 − 1)) for the number of derangements on 𝑁 + 1. (Contributed by Mario Carneiro, 22-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))    &   𝐴 = {𝑓 ∣ (𝑓:(1...(𝑁 + 1))–1-1-onto→(1...(𝑁 + 1)) ∧ ∀𝑦 ∈ (1...(𝑁 + 1))(𝑓𝑦) ≠ 𝑦)}       (𝑁 ∈ ℕ → (𝑆‘(𝑁 + 1)) = (𝑁 · ((𝑆𝑁) + (𝑆‘(𝑁 − 1)))))

Theoremsubfacp1 31714* A two-term recurrence for the subfactorial. This theorem allows us to forget the combinatorial definition of the derangement number in favor of the recursive definition provided by this theorem and subfac0 31705, subfac1 31706. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑁 ∈ ℕ → (𝑆‘(𝑁 + 1)) = (𝑁 · ((𝑆𝑁) + (𝑆‘(𝑁 − 1)))))

Theoremsubfacval2 31715* A closed-form expression for the subfactorial. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑁 ∈ ℕ0 → (𝑆𝑁) = ((!‘𝑁) · Σ𝑘 ∈ (0...𝑁)((-1↑𝑘) / (!‘𝑘))))

Theoremsubfaclim 31716* The subfactorial converges rapidly to 𝑁! / e. This is part of Metamath 100 proof #88. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑁 ∈ ℕ → (abs‘(((!‘𝑁) / e) − (𝑆𝑁))) < (1 / 𝑁))

Theoremsubfacval3 31717* Another closed form expression for the subfactorial. The expression ⌊‘(𝑥 + 1 / 2) is a way of saying "rounded to the nearest integer". (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))    &   𝑆 = (𝑛 ∈ ℕ0 ↦ (𝐷‘(1...𝑛)))       (𝑁 ∈ ℕ → (𝑆𝑁) = (⌊‘(((!‘𝑁) / e) + (1 / 2))))

Theoremderangfmla 31718* The derangements formula, which expresses the number of derangements of a finite nonempty set in terms of the factorial. The expression ⌊‘(𝑥 + 1 / 2) is a way of saying "rounded to the nearest integer". This is part of Metamath 100 proof #88. (Contributed by Mario Carneiro, 23-Jan-2015.)
𝐷 = (𝑥 ∈ Fin ↦ (♯‘{𝑓 ∣ (𝑓:𝑥1-1-onto𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) ≠ 𝑦)}))       ((𝐴 ∈ Fin ∧ 𝐴 ≠ ∅) → (𝐷𝐴) = (⌊‘(((!‘(♯‘𝐴)) / e) + (1 / 2))))

20.5.4  The Erdős-Szekeres theorem

Theoremerdszelem1 31719* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
𝑆 = {𝑦 ∈ 𝒫 (1...𝐴) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝐴𝑦)}       (𝑋𝑆 ↔ (𝑋 ⊆ (1...𝐴) ∧ (𝐹𝑋) Isom < , 𝑂 (𝑋, (𝐹𝑋)) ∧ 𝐴𝑋))

Theoremerdszelem2 31720* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
𝑆 = {𝑦 ∈ 𝒫 (1...𝐴) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝐴𝑦)}       ((♯ “ 𝑆) ∈ Fin ∧ (♯ “ 𝑆) ⊆ ℕ)

Theoremerdszelem3 31721* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐾 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))       (𝐴 ∈ (1...𝑁) → (𝐾𝐴) = sup((♯ “ {𝑦 ∈ 𝒫 (1...𝐴) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝐴𝑦)}), ℝ, < ))

Theoremerdszelem4 31722* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐾 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑂 Or ℝ       ((𝜑𝐴 ∈ (1...𝑁)) → {𝐴} ∈ {𝑦 ∈ 𝒫 (1...𝐴) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝐴𝑦)})

Theoremerdszelem5 31723* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐾 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑂 Or ℝ       ((𝜑𝐴 ∈ (1...𝑁)) → (𝐾𝐴) ∈ (♯ “ {𝑦 ∈ 𝒫 (1...𝐴) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝐴𝑦)}))

Theoremerdszelem6 31724* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐾 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑂 Or ℝ       (𝜑𝐾:(1...𝑁)⟶ℕ)

Theoremerdszelem7 31725* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐾 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑂 Or ℝ    &   (𝜑𝐴 ∈ (1...𝑁))    &   (𝜑𝑅 ∈ ℕ)    &   (𝜑 → ¬ (𝐾𝐴) ∈ (1...(𝑅 − 1)))       (𝜑 → ∃𝑠 ∈ 𝒫 (1...𝑁)(𝑅 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , 𝑂 (𝑠, (𝐹𝑠))))

Theoremerdszelem8 31726* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐾 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , 𝑂 (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑂 Or ℝ    &   (𝜑𝐴 ∈ (1...𝑁))    &   (𝜑𝐵 ∈ (1...𝑁))    &   (𝜑𝐴 < 𝐵)       (𝜑 → ((𝐾𝐴) = (𝐾𝐵) → ¬ (𝐹𝐴)𝑂(𝐹𝐵)))

Theoremerdszelem9 31727* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐼 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , < (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝐽 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , < (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑇 = (𝑛 ∈ (1...𝑁) ↦ ⟨(𝐼𝑛), (𝐽𝑛)⟩)       (𝜑𝑇:(1...𝑁)–1-1→(ℕ × ℕ))

Theoremerdszelem10 31728* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐼 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , < (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝐽 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , < (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑇 = (𝑛 ∈ (1...𝑁) ↦ ⟨(𝐼𝑛), (𝐽𝑛)⟩)    &   (𝜑𝑅 ∈ ℕ)    &   (𝜑𝑆 ∈ ℕ)    &   (𝜑 → ((𝑅 − 1) · (𝑆 − 1)) < 𝑁)       (𝜑 → ∃𝑚 ∈ (1...𝑁)(¬ (𝐼𝑚) ∈ (1...(𝑅 − 1)) ∨ ¬ (𝐽𝑚) ∈ (1...(𝑆 − 1))))

Theoremerdszelem11 31729* Lemma for erdsze 31730. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   𝐼 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , < (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝐽 = (𝑥 ∈ (1...𝑁) ↦ sup((♯ “ {𝑦 ∈ 𝒫 (1...𝑥) ∣ ((𝐹𝑦) Isom < , < (𝑦, (𝐹𝑦)) ∧ 𝑥𝑦)}), ℝ, < ))    &   𝑇 = (𝑛 ∈ (1...𝑁) ↦ ⟨(𝐼𝑛), (𝐽𝑛)⟩)    &   (𝜑𝑅 ∈ ℕ)    &   (𝜑𝑆 ∈ ℕ)    &   (𝜑 → ((𝑅 − 1) · (𝑆 − 1)) < 𝑁)       (𝜑 → ∃𝑠 ∈ 𝒫 (1...𝑁)((𝑅 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠))) ∨ (𝑆 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠)))))

Theoremerdsze 31730* The Erdős-Szekeres theorem. For any injective sequence 𝐹 on the reals of length at least (𝑅 − 1) · (𝑆 − 1) + 1, there is either a subsequence of length at least 𝑅 on which 𝐹 is increasing (i.e. a < , < order isomorphism) or a subsequence of length at least 𝑆 on which 𝐹 is decreasing (i.e. a < , < order isomorphism, recalling that < is the "greater than" relation). This is part of Metamath 100 proof #73. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑁 ∈ ℕ)    &   (𝜑𝐹:(1...𝑁)–1-1→ℝ)    &   (𝜑𝑅 ∈ ℕ)    &   (𝜑𝑆 ∈ ℕ)    &   (𝜑 → ((𝑅 − 1) · (𝑆 − 1)) < 𝑁)       (𝜑 → ∃𝑠 ∈ 𝒫 (1...𝑁)((𝑅 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠))) ∨ (𝑆 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠)))))

Theoremerdsze2lem1 31731* Lemma for erdsze2 31733. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑅 ∈ ℕ)    &   (𝜑𝑆 ∈ ℕ)    &   (𝜑𝐹:𝐴1-1→ℝ)    &   (𝜑𝐴 ⊆ ℝ)    &   𝑁 = ((𝑅 − 1) · (𝑆 − 1))    &   (𝜑𝑁 < (♯‘𝐴))       (𝜑 → ∃𝑓(𝑓:(1...(𝑁 + 1))–1-1𝐴𝑓 Isom < , < ((1...(𝑁 + 1)), ran 𝑓)))

Theoremerdsze2lem2 31732* Lemma for erdsze2 31733. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑅 ∈ ℕ)    &   (𝜑𝑆 ∈ ℕ)    &   (𝜑𝐹:𝐴1-1→ℝ)    &   (𝜑𝐴 ⊆ ℝ)    &   𝑁 = ((𝑅 − 1) · (𝑆 − 1))    &   (𝜑𝑁 < (♯‘𝐴))    &   (𝜑𝐺:(1...(𝑁 + 1))–1-1𝐴)    &   (𝜑𝐺 Isom < , < ((1...(𝑁 + 1)), ran 𝐺))       (𝜑 → ∃𝑠 ∈ 𝒫 𝐴((𝑅 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠))) ∨ (𝑆 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠)))))

Theoremerdsze2 31733* Generalize the statement of the Erdős-Szekeres theorem erdsze 31730 to "sequences" indexed by an arbitrary subset of , which can be infinite. This is part of Metamath 100 proof #73. (Contributed by Mario Carneiro, 22-Jan-2015.)
(𝜑𝑅 ∈ ℕ)    &   (𝜑𝑆 ∈ ℕ)    &   (𝜑𝐹:𝐴1-1→ℝ)    &   (𝜑𝐴 ⊆ ℝ)    &   (𝜑 → ((𝑅 − 1) · (𝑆 − 1)) < (♯‘𝐴))       (𝜑 → ∃𝑠 ∈ 𝒫 𝐴((𝑅 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠))) ∨ (𝑆 ≤ (♯‘𝑠) ∧ (𝐹𝑠) Isom < , < (𝑠, (𝐹𝑠)))))

20.5.5  The Kuratowski closure-complement theorem

Theoremkur14lem1 31734 Lemma for kur14 31744. (Contributed by Mario Carneiro, 17-Feb-2015.)
𝐴𝑋    &   (𝑋𝐴) ∈ 𝑇    &   (𝐾𝐴) ∈ 𝑇       (𝑁 = 𝐴 → (𝑁𝑋 ∧ {(𝑋𝑁), (𝐾𝑁)} ⊆ 𝑇))

Theoremkur14lem2 31735 Lemma for kur14 31744. Write interior in terms of closure and complement: 𝑖𝐴 = 𝑐𝑘𝑐𝐴 where 𝑐 is complement and 𝑘 is closure. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋       (𝐼𝐴) = (𝑋 ∖ (𝐾‘(𝑋𝐴)))

Theoremkur14lem3 31736 Lemma for kur14 31744. A closure is a subset of the base set. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋       (𝐾𝐴) ⊆ 𝑋

Theoremkur14lem4 31737 Lemma for kur14 31744. Complementation is an involution on the set of subsets of a topology. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋       (𝑋 ∖ (𝑋𝐴)) = 𝐴

Theoremkur14lem5 31738 Lemma for kur14 31744. Closure is an idempotent operation in the set of subsets of a topology. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋       (𝐾‘(𝐾𝐴)) = (𝐾𝐴)

Theoremkur14lem6 31739 Lemma for kur14 31744. If 𝑘 is the complementation operator and 𝑘 is the closure operator, this expresses the identity 𝑘𝑐𝑘𝐴 = 𝑘𝑐𝑘𝑐𝑘𝑐𝑘𝐴 for any subset 𝐴 of the topological space. This is the key result that lets us cut down long enough sequences of 𝑐𝑘𝑐𝑘... that arise when applying closure and complement repeatedly to 𝐴, and explains why we end up with a number as large as 14, yet no larger. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋    &   𝐵 = (𝑋 ∖ (𝐾𝐴))       (𝐾‘(𝐼‘(𝐾𝐵))) = (𝐾𝐵)

Theoremkur14lem7 31740 Lemma for kur14 31744: main proof. The set 𝑇 here contains all the distinct combinations of 𝑘 and 𝑐 that can arise, and we prove here that applying 𝑘 or 𝑐 to any element of 𝑇 yields another elemnt of 𝑇. In operator shorthand, we have 𝑇 = {𝐴, 𝑐𝐴, 𝑘𝐴 , 𝑐𝑘𝐴, 𝑘𝑐𝐴, 𝑐𝑘𝑐𝐴, 𝑘𝑐𝑘𝐴, 𝑐𝑘𝑐𝑘𝐴, 𝑘𝑐𝑘𝑐𝐴, 𝑐𝑘𝑐𝑘𝑐𝐴, 𝑘𝑐𝑘𝑐𝑘𝐴, 𝑐𝑘𝑐𝑘𝑐𝑘𝐴, 𝑘𝑐𝑘𝑐𝑘𝑐𝐴, 𝑐𝑘𝑐𝑘𝑐𝑘𝑐𝐴}. From the identities 𝑐𝑐𝐴 = 𝐴 and 𝑘𝑘𝐴 = 𝑘𝐴, we can reduce any operator combination containing two adjacent identical operators, which is why the list only contains alternating sequences. The reason the sequences don't keep going after a certain point is due to the identity 𝑘𝑐𝑘𝐴 = 𝑘𝑐𝑘𝑐𝑘𝑐𝑘𝐴, proved in kur14lem6 31739. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋    &   𝐵 = (𝑋 ∖ (𝐾𝐴))    &   𝐶 = (𝐾‘(𝑋𝐴))    &   𝐷 = (𝐼‘(𝐾𝐴))    &   𝑇 = ((({𝐴, (𝑋𝐴), (𝐾𝐴)} ∪ {𝐵, 𝐶, (𝐼𝐴)}) ∪ {(𝐾𝐵), 𝐷, (𝐾‘(𝐼𝐴))}) ∪ ({(𝐼𝐶), (𝐾𝐷), (𝐼‘(𝐾𝐵))} ∪ {(𝐾‘(𝐼𝐶)), (𝐼‘(𝐾‘(𝐼𝐴)))}))       (𝑁𝑇 → (𝑁𝑋 ∧ {(𝑋𝑁), (𝐾𝑁)} ⊆ 𝑇))

Theoremkur14lem8 31741 Lemma for kur14 31744. Show that the set 𝑇 contains at most 14 elements. (It could be less if some of the operators take the same value for a given set, but Kuratowski showed that this upper bound of 14 is tight in the sense that there exist topological spaces and subsets of these spaces for which all 14 generated sets are distinct, and indeed the real numbers form such a topological space.) (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋    &   𝐵 = (𝑋 ∖ (𝐾𝐴))    &   𝐶 = (𝐾‘(𝑋𝐴))    &   𝐷 = (𝐼‘(𝐾𝐴))    &   𝑇 = ((({𝐴, (𝑋𝐴), (𝐾𝐴)} ∪ {𝐵, 𝐶, (𝐼𝐴)}) ∪ {(𝐾𝐵), 𝐷, (𝐾‘(𝐼𝐴))}) ∪ ({(𝐼𝐶), (𝐾𝐷), (𝐼‘(𝐾𝐵))} ∪ {(𝐾‘(𝐼𝐶)), (𝐼‘(𝐾‘(𝐼𝐴)))}))       (𝑇 ∈ Fin ∧ (♯‘𝑇) ≤ 14)

Theoremkur14lem9 31742* Lemma for kur14 31744. Since the set 𝑇 is closed under closure and complement, it contains the minimal set 𝑆 as a subset, so 𝑆 also has at most 14 elements. (Indeed 𝑆 = 𝑇, and it's not hard to prove this, but we don't need it for this proof.) (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝐼 = (int‘𝐽)    &   𝐴𝑋    &   𝐵 = (𝑋 ∖ (𝐾𝐴))    &   𝐶 = (𝐾‘(𝑋𝐴))    &   𝐷 = (𝐼‘(𝐾𝐴))    &   𝑇 = ((({𝐴, (𝑋𝐴), (𝐾𝐴)} ∪ {𝐵, 𝐶, (𝐼𝐴)}) ∪ {(𝐾𝐵), 𝐷, (𝐾‘(𝐼𝐴))}) ∪ ({(𝐼𝐶), (𝐾𝐷), (𝐼‘(𝐾𝐵))} ∪ {(𝐾‘(𝐼𝐶)), (𝐼‘(𝐾‘(𝐼𝐴)))}))    &   𝑆 = {𝑥 ∈ 𝒫 𝒫 𝑋 ∣ (𝐴𝑥 ∧ ∀𝑦𝑥 {(𝑋𝑦), (𝐾𝑦)} ⊆ 𝑥)}       (𝑆 ∈ Fin ∧ (♯‘𝑆) ≤ 14)

Theoremkur14lem10 31743* Lemma for kur14 31744. Discharge the set 𝑇. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝐽 ∈ Top    &   𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝑆 = {𝑥 ∈ 𝒫 𝒫 𝑋 ∣ (𝐴𝑥 ∧ ∀𝑦𝑥 {(𝑋𝑦), (𝐾𝑦)} ⊆ 𝑥)}    &   𝐴𝑋       (𝑆 ∈ Fin ∧ (♯‘𝑆) ≤ 14)

Theoremkur14 31744* Kuratowski's closure-complement theorem. There are at most 14 sets which can be obtained by the application of the closure and complement operations to a set in a topological space. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑋 = 𝐽    &   𝐾 = (cls‘𝐽)    &   𝑆 = {𝑥 ∈ 𝒫 𝒫 𝑋 ∣ (𝐴𝑥 ∧ ∀𝑦𝑥 {(𝑋𝑦), (𝐾𝑦)} ⊆ 𝑥)}       ((𝐽 ∈ Top ∧ 𝐴𝑋) → (𝑆 ∈ Fin ∧ (♯‘𝑆) ≤ 14))

20.5.6  Retracts and sections

Syntaxcretr 31745 Extend class notation with the retract relation.
class Retr

Definitiondf-retr 31746* Define the set of retractions on two topological spaces. We say that 𝑅 is a retraction from 𝐽 to 𝐾. or 𝑅 ∈ (𝐽 Retr 𝐾) iff there is an 𝑆 such that 𝑅:𝐽𝐾, 𝑆:𝐾𝐽 are continuous functions called the retraction and section respectively, and their composite 𝑅𝑆 is homotopic to the identity map. If a retraction exists, we say 𝐽 is a retract of 𝐾. (This terminology is borrowed from HoTT and appears to be nonstandard, although it has similaries to the concept of retract in the category of topological spaces and to a deformation retract in general topology.) Two topological spaces that are retracts of each other are called homotopy equivalent. (Contributed by Mario Carneiro, 11-Feb-2015.)
Retr = (𝑗 ∈ Top, 𝑘 ∈ Top ↦ {𝑟 ∈ (𝑗 Cn 𝑘) ∣ ∃𝑠 ∈ (𝑘 Cn 𝑗)((𝑟𝑠)(𝑗 Htpy 𝑗)( I ↾ 𝑗)) ≠ ∅})

20.5.7  Path-connected and simply connected spaces

Syntaxcpconn 31747 Extend class notation with the class of path-connected topologies.
class PConn

Syntaxcsconn 31748 Extend class notation with the class of simply connected topologies.
class SConn

Definitiondf-pconn 31749* Define the class of path-connected topologies. A topology is path-connected if there is a path (a continuous function from the closed unit interval) that goes from 𝑥 to 𝑦 for any points 𝑥, 𝑦 in the space. (Contributed by Mario Carneiro, 11-Feb-2015.)
PConn = {𝑗 ∈ Top ∣ ∀𝑥 𝑗𝑦 𝑗𝑓 ∈ (II Cn 𝑗)((𝑓‘0) = 𝑥 ∧ (𝑓‘1) = 𝑦)}

Definitiondf-sconn 31750* Define the class of simply connected topologies. A topology is simply connected if it is path-connected and every loop (continuous path with identical start and endpoint) is contractible to a point (path-homotopic to a constant function). (Contributed by Mario Carneiro, 11-Feb-2015.)
SConn = {𝑗 ∈ PConn ∣ ∀𝑓 ∈ (II Cn 𝑗)((𝑓‘0) = (𝑓‘1) → 𝑓( ≃ph𝑗)((0[,]1) × {(𝑓‘0)}))}

Theoremispconn 31751* The property of being a path-connected topological space. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑋 = 𝐽       (𝐽 ∈ PConn ↔ (𝐽 ∈ Top ∧ ∀𝑥𝑋𝑦𝑋𝑓 ∈ (II Cn 𝐽)((𝑓‘0) = 𝑥 ∧ (𝑓‘1) = 𝑦)))

Theorempconncn 31752* The property of being a path-connected topological space. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑋 = 𝐽       ((𝐽 ∈ PConn ∧ 𝐴𝑋𝐵𝑋) → ∃𝑓 ∈ (II Cn 𝐽)((𝑓‘0) = 𝐴 ∧ (𝑓‘1) = 𝐵))

Theorempconntop 31753 A simply connected space is a topology. (Contributed by Mario Carneiro, 11-Feb-2015.)
(𝐽 ∈ PConn → 𝐽 ∈ Top)

Theoremissconn 31754* The property of being a simply connected topological space. (Contributed by Mario Carneiro, 11-Feb-2015.)
(𝐽 ∈ SConn ↔ (𝐽 ∈ PConn ∧ ∀𝑓 ∈ (II Cn 𝐽)((𝑓‘0) = (𝑓‘1) → 𝑓( ≃ph𝐽)((0[,]1) × {(𝑓‘0)}))))

Theoremsconnpconn 31755 A simply connected space is path-connected. (Contributed by Mario Carneiro, 11-Feb-2015.)
(𝐽 ∈ SConn → 𝐽 ∈ PConn)

Theoremsconntop 31756 A simply connected space is a topology. (Contributed by Mario Carneiro, 11-Feb-2015.)
(𝐽 ∈ SConn → 𝐽 ∈ Top)

Theoremsconnpht 31757 A closed path in a simply connected space is contractible to a point. (Contributed by Mario Carneiro, 11-Feb-2015.)
((𝐽 ∈ SConn ∧ 𝐹 ∈ (II Cn 𝐽) ∧ (𝐹‘0) = (𝐹‘1)) → 𝐹( ≃ph𝐽)((0[,]1) × {(𝐹‘0)}))

Theoremcnpconn 31758 An image of a path-connected space is path-connected. (Contributed by Mario Carneiro, 24-Mar-2015.)
𝑌 = 𝐾       ((𝐽 ∈ PConn ∧ 𝐹:𝑋onto𝑌𝐹 ∈ (𝐽 Cn 𝐾)) → 𝐾 ∈ PConn)

Theorempconnconn 31759 A path-connected space is connected. (Contributed by Mario Carneiro, 11-Feb-2015.)
(𝐽 ∈ PConn → 𝐽 ∈ Conn)

Theoremtxpconn 31760 The topological product of two path-connected spaces is path-connected. (Contributed by Mario Carneiro, 12-Feb-2015.)
((𝑅 ∈ PConn ∧ 𝑆 ∈ PConn) → (𝑅 ×t 𝑆) ∈ PConn)

Theoremptpconn 31761 The topological product of a collection of path-connected spaces is path-connected. The proof uses the axiom of choice. (Contributed by Mario Carneiro, 17-Feb-2015.)
((𝐴𝑉𝐹:𝐴⟶PConn) → (∏t𝐹) ∈ PConn)

Theoremindispconn 31762 The indiscrete topology (or trivial topology) on any set is path-connected. (Contributed by Mario Carneiro, 7-Jul-2015.) (Revised by Mario Carneiro, 14-Aug-2015.)
{∅, 𝐴} ∈ PConn

Theoremconnpconn 31763 A connected and locally path-connected space is path-connected. (Contributed by Mario Carneiro, 7-Jul-2015.)
((𝐽 ∈ Conn ∧ 𝐽 ∈ 𝑛-Locally PConn) → 𝐽 ∈ PConn)

Theoremqtoppconn 31764 A quotient of a path-connected space is path-connected. (Contributed by Mario Carneiro, 24-Mar-2015.)
𝑋 = 𝐽       ((𝐽 ∈ PConn ∧ 𝐹 Fn 𝑋) → (𝐽 qTop 𝐹) ∈ PConn)

Theorempconnpi1 31765 All fundamental groups in a path-connected space are isomorphic. (Contributed by Mario Carneiro, 12-Feb-2015.)
𝑋 = 𝐽    &   𝑃 = (𝐽 π1 𝐴)    &   𝑄 = (𝐽 π1 𝐵)    &   𝑆 = (Base‘𝑃)    &   𝑇 = (Base‘𝑄)       ((𝐽 ∈ PConn ∧ 𝐴𝑋𝐵𝑋) → 𝑃𝑔 𝑄)

Theoremsconnpht2 31766 Any two paths in a simply connected space with the same start and end point are path-homotopic. (Contributed by Mario Carneiro, 12-Feb-2015.)
(𝜑𝐽 ∈ SConn)    &   (𝜑𝐹 ∈ (II Cn 𝐽))    &   (𝜑𝐺 ∈ (II Cn 𝐽))    &   (𝜑 → (𝐹‘0) = (𝐺‘0))    &   (𝜑 → (𝐹‘1) = (𝐺‘1))       (𝜑𝐹( ≃ph𝐽)𝐺)

Theoremsconnpi1 31767 A path-connected topological space is simply connected iff its fundamental group is trivial. (Contributed by Mario Carneiro, 12-Feb-2015.)
𝑋 = 𝐽       ((𝐽 ∈ PConn ∧ 𝑌𝑋) → (𝐽 ∈ SConn ↔ (Base‘(𝐽 π1 𝑌)) ≈ 1o))

Theoremtxsconnlem 31768 Lemma for txsconn 31769. (Contributed by Mario Carneiro, 9-Mar-2015.)
(𝜑𝑅 ∈ Top)    &   (𝜑𝑆 ∈ Top)    &   (𝜑𝐹 ∈ (II Cn (𝑅 ×t 𝑆)))    &   𝐴 = ((1st ↾ ( 𝑅 × 𝑆)) ∘ 𝐹)    &   𝐵 = ((2nd ↾ ( 𝑅 × 𝑆)) ∘ 𝐹)    &   (𝜑𝐺 ∈ (𝐴(PHtpy‘𝑅)((0[,]1) × {(𝐴‘0)})))    &   (𝜑𝐻 ∈ (𝐵(PHtpy‘𝑆)((0[,]1) × {(𝐵‘0)})))       (𝜑𝐹( ≃ph‘(𝑅 ×t 𝑆))((0[,]1) × {(𝐹‘0)}))

Theoremtxsconn 31769 The topological product of two simply connected spaces is simply connected. (Contributed by Mario Carneiro, 12-Feb-2015.)
((𝑅 ∈ SConn ∧ 𝑆 ∈ SConn) → (𝑅 ×t 𝑆) ∈ SConn)

Theoremcvxpconn 31770* A convex subset of the complex numbers is path-connected. (Contributed by Mario Carneiro, 12-Feb-2015.)
(𝜑𝑆 ⊆ ℂ)    &   ((𝜑 ∧ (𝑥𝑆𝑦𝑆𝑡 ∈ (0[,]1))) → ((𝑡 · 𝑥) + ((1 − 𝑡) · 𝑦)) ∈ 𝑆)    &   𝐽 = (TopOpen‘ℂfld)    &   𝐾 = (𝐽t 𝑆)       (𝜑𝐾 ∈ PConn)

Theoremcvxsconn 31771* A convex subset of the complex numbers is simply connected. (Contributed by Mario Carneiro, 12-Feb-2015.)
(𝜑𝑆 ⊆ ℂ)    &   ((𝜑 ∧ (𝑥𝑆𝑦𝑆𝑡 ∈ (0[,]1))) → ((𝑡 · 𝑥) + ((1 − 𝑡) · 𝑦)) ∈ 𝑆)    &   𝐽 = (TopOpen‘ℂfld)    &   𝐾 = (𝐽t 𝑆)       (𝜑𝐾 ∈ SConn)

Theoremblsconn 31772 An open ball in the complex numbers is simply connected. (Contributed by Mario Carneiro, 12-Feb-2015.)
𝐽 = (TopOpen‘ℂfld)    &   𝑆 = (𝑃(ball‘(abs ∘ − ))𝑅)    &   𝐾 = (𝐽t 𝑆)       ((𝑃 ∈ ℂ ∧ 𝑅 ∈ ℝ*) → 𝐾 ∈ SConn)

Theoremcnllysconn 31773 The topology of the complex numbers is locally simply connected. (Contributed by Mario Carneiro, 2-Mar-2015.)
𝐽 = (TopOpen‘ℂfld)       𝐽 ∈ Locally SConn

Theoremresconn 31774 A subset of is simply connected iff it is connected. (Contributed by Mario Carneiro, 9-Mar-2015.)
𝐽 = ((topGen‘ran (,)) ↾t 𝐴)       (𝐴 ⊆ ℝ → (𝐽 ∈ SConn ↔ 𝐽 ∈ Conn))

Theoremioosconn 31775 An open interval is simply connected. (Contributed by Mario Carneiro, 9-Mar-2015.)
((topGen‘ran (,)) ↾t (𝐴(,)𝐵)) ∈ SConn

Theoremiccsconn 31776 A closed interval is simply connected. (Contributed by Mario Carneiro, 9-Mar-2015.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((topGen‘ran (,)) ↾t (𝐴[,]𝐵)) ∈ SConn)

Theoremretopsconn 31777 The real numbers are simply connected. (Contributed by Mario Carneiro, 9-Mar-2015.)
(topGen‘ran (,)) ∈ SConn

Theoremiccllysconn 31778 A closed interval is locally simply connected. (Contributed by Mario Carneiro, 10-Mar-2015.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((topGen‘ran (,)) ↾t (𝐴[,]𝐵)) ∈ Locally SConn)

Theoremrellysconn 31779 The real numbers are locally simply connected. (Contributed by Mario Carneiro, 10-Mar-2015.)
(topGen‘ran (,)) ∈ Locally SConn

Theoremiisconn 31780 The unit interval is simply connected. (Contributed by Mario Carneiro, 9-Mar-2015.)
II ∈ SConn

Theoremiillysconn 31781 The unit interval is locally simply connected. (Contributed by Mario Carneiro, 10-Mar-2015.)
II ∈ Locally SConn

Theoremiinllyconn 31782 The unit interval is locally connected. (Contributed by Mario Carneiro, 6-Jul-2015.)
II ∈ 𝑛-Locally Conn

20.5.8  Covering maps

Syntaxccvm 31783 Extend class notation with the class of covering maps.
class CovMap

Definitiondf-cvm 31784* Define the class of covering maps on two topological spaces. A function 𝑓:𝑐𝑗 is a covering map if it is continuous and for every point 𝑥 in the target space there is a neighborhood 𝑘 of 𝑥 and a decomposition 𝑠 of the preimage of 𝑘 as a disjoint union such that 𝑓 is a homeomorphism of each set 𝑢𝑠 onto 𝑘. (Contributed by Mario Carneiro, 13-Feb-2015.)
CovMap = (𝑐 ∈ Top, 𝑗 ∈ Top ↦ {𝑓 ∈ (𝑐 Cn 𝑗) ∣ ∀𝑥 𝑗𝑘𝑗 (𝑥𝑘 ∧ ∃𝑠 ∈ (𝒫 𝑐 ∖ {∅})( 𝑠 = (𝑓𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝑓𝑢) ∈ ((𝑐t 𝑢)Homeo(𝑗t 𝑘)))))})

Theoremfncvm 31785 Lemma for covering maps. (Contributed by Mario Carneiro, 13-Feb-2015.)
CovMap Fn (Top × Top)

Theoremcvmscbv 31786* Change bound variables in the set of even coverings. (Contributed by Mario Carneiro, 17-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       𝑆 = (𝑎𝐽 ↦ {𝑏 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑏 = (𝐹𝑎) ∧ ∀𝑐𝑏 (∀𝑑 ∈ (𝑏 ∖ {𝑐})(𝑐𝑑) = ∅ ∧ (𝐹𝑐) ∈ ((𝐶t 𝑐)Homeo(𝐽t 𝑎))))})

Theoremiscvm 31787* The property of being a covering map. (Contributed by Mario Carneiro, 13-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})    &   𝑋 = 𝐽       (𝐹 ∈ (𝐶 CovMap 𝐽) ↔ ((𝐶 ∈ Top ∧ 𝐽 ∈ Top ∧ 𝐹 ∈ (𝐶 Cn 𝐽)) ∧ ∀𝑥𝑋𝑘𝐽 (𝑥𝑘 ∧ (𝑆𝑘) ≠ ∅)))

Theoremcvmtop1 31788 Reverse closure for a covering map. (Contributed by Mario Carneiro, 11-Feb-2015.)
(𝐹 ∈ (𝐶 CovMap 𝐽) → 𝐶 ∈ Top)

Theoremcvmtop2 31789 Reverse closure for a covering map. (Contributed by Mario Carneiro, 13-Feb-2015.)
(𝐹 ∈ (𝐶 CovMap 𝐽) → 𝐽 ∈ Top)

Theoremcvmcn 31790 A covering map is a continuous function. (Contributed by Mario Carneiro, 13-Feb-2015.)
(𝐹 ∈ (𝐶 CovMap 𝐽) → 𝐹 ∈ (𝐶 Cn 𝐽))

Theoremcvmcov 31791* Property of a covering map. In order to make the covering property more manageable, we define here the set 𝑆(𝑘) of all even coverings of an open set 𝑘 in the range. Then the covering property states that every point has a neighborhood which has an even covering. (Contributed by Mario Carneiro, 13-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})    &   𝑋 = 𝐽       ((𝐹 ∈ (𝐶 CovMap 𝐽) ∧ 𝑃𝑋) → ∃𝑥𝐽 (𝑃𝑥 ∧ (𝑆𝑥) ≠ ∅))

Theoremcvmsrcl 31792* Reverse closure for an even covering. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       (𝑇 ∈ (𝑆𝑈) → 𝑈𝐽)

Theoremcvmsi 31793* One direction of cvmsval 31794. (Contributed by Mario Carneiro, 13-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       (𝑇 ∈ (𝑆𝑈) → (𝑈𝐽 ∧ (𝑇𝐶𝑇 ≠ ∅) ∧ ( 𝑇 = (𝐹𝑈) ∧ ∀𝑢𝑇 (∀𝑣 ∈ (𝑇 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑈))))))

Theoremcvmsval 31794* Elementhood in the set 𝑆 of all even coverings of an open set in 𝐽. 𝑆 is an even covering of 𝑈 if it is a nonempty collection of disjoint open sets in 𝐶 whose union is the preimage of 𝑈, such that each set 𝑢𝑆 is homeomorphic under 𝐹 to 𝑈. (Contributed by Mario Carneiro, 13-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       (𝐶𝑉 → (𝑇 ∈ (𝑆𝑈) ↔ (𝑈𝐽 ∧ (𝑇𝐶𝑇 ≠ ∅) ∧ ( 𝑇 = (𝐹𝑈) ∧ ∀𝑢𝑇 (∀𝑣 ∈ (𝑇 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑈)))))))

Theoremcvmsss 31795* An even covering is a subset of the topology of the domain (i.e. a collection of open sets). (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       (𝑇 ∈ (𝑆𝑈) → 𝑇𝐶)

Theoremcvmsn0 31796* An even covering is nonempty. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       (𝑇 ∈ (𝑆𝑈) → 𝑇 ≠ ∅)

Theoremcvmsuni 31797* An even covering of 𝑈 has union equal to the preimage of 𝑈 by 𝐹. (Contributed by Mario Carneiro, 11-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       (𝑇 ∈ (𝑆𝑈) → 𝑇 = (𝐹𝑈))

Theoremcvmsdisj 31798* An even covering of 𝑈 is a disjoint union. (Contributed by Mario Carneiro, 13-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       ((𝑇 ∈ (𝑆𝑈) ∧ 𝐴𝑇𝐵𝑇) → (𝐴 = 𝐵 ∨ (𝐴𝐵) = ∅))

Theoremcvmshmeo 31799* Every element of an even covering of 𝑈 is homeomorphic to 𝑈 via 𝐹. (Contributed by Mario Carneiro, 13-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       ((𝑇 ∈ (𝑆𝑈) ∧ 𝐴𝑇) → (𝐹𝐴) ∈ ((𝐶t 𝐴)Homeo(𝐽t 𝑈)))

Theoremcvmsf1o 31800* 𝐹, localized to an element of an even covering of 𝑈, is a bijection. (Contributed by Mario Carneiro, 14-Feb-2015.)
𝑆 = (𝑘𝐽 ↦ {𝑠 ∈ (𝒫 𝐶 ∖ {∅}) ∣ ( 𝑠 = (𝐹𝑘) ∧ ∀𝑢𝑠 (∀𝑣 ∈ (𝑠 ∖ {𝑢})(𝑢𝑣) = ∅ ∧ (𝐹𝑢) ∈ ((𝐶t 𝑢)Homeo(𝐽t 𝑘))))})       ((𝐹 ∈ (𝐶 CovMap 𝐽) ∧ 𝑇 ∈ (𝑆𝑈) ∧ 𝐴𝑇) → (𝐹𝐴):𝐴1-1-onto𝑈)

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78 7701-7800 79 7801-7900 80 7901-8000 81 8001-8100 82 8101-8200 83 8201-8300 84 8301-8400 85 8401-8500 86 8501-8600 87 8601-8700 88 8701-8800 89 8801-8900 90 8901-9000 91 9001-9100 92 9101-9200 93 9201-9300 94 9301-9400 95 9401-9500 96 9501-9600 97 9601-9700 98 9701-9800 99 9801-9900 100 9901-10000 101 10001-10100 102 10101-10200 103 10201-10300 104 10301-10400 105 10401-10500 106 10501-10600 107 10601-10700 108 10701-10800 109 10801-10900 110 10901-11000 111 11001-11100 112 11101-11200 113 11201-11300 114 11301-11400 115 11401-11500 116 11501-11600 117 11601-11700 118 11701-11800 119 11801-11900 120 11901-12000 121 12001-12100 122 12101-12200 123 12201-12300 124 12301-12400 125 12401-12500 126 12501-12600 127 12601-12700 128 12701-12800 129 12801-12900 130 12901-13000 131 13001-13100 132 13101-13200 133 13201-13300 134 13301-13400 135 13401-13500 136 13501-13600 137 13601-13700 138 13701-13800 139 13801-13900 140 13901-14000 141 14001-14100 142 14101-14200 143 14201-14300 144 14301-14400 145 14401-14500 146 14501-14600 147 14601-14700 148 14701-14800 149 14801-14900 150 14901-15000 151 15001-15100 152 15101-15200 153 15201-15300 154 15301-15400 155 15401-15500 156 15501-15600 157 15601-15700 158 15701-15800 159 15801-15900 160 15901-16000 161 16001-16100 162 16101-16200 163 16201-16300 164 16301-16400 165 16401-16500 166 16501-16600 167 16601-16700 168 16701-16800 169 16801-16900 170 16901-17000 171 17001-17100 172 17101-17200 173 17201-17300 174 17301-17400 175 17401-17500 176 17501-17600 177 17601-17700 178 17701-17800 179 17801-17900 180 17901-18000 181 18001-18100 182 18101-18200 183 18201-18300 184 18301-18400 185 18401-18500 186 18501-18600 187 18601-18700 188 18701-18800 189 18801-18900 190 18901-19000 191 19001-19100 192 19101-19200 193 19201-19300 194 19301-19400 195 19401-19500 196 19501-19600 197 19601-19700 198 19701-19800 199 19801-19900 200 19901-20000 201 20001-20100 202 20101-20200 203 20201-20300 204 20301-20400 205 20401-20500 206 20501-20600 207 20601-20700 208 20701-20800 209 20801-20900 210 20901-21000 211 21001-21100 212 21101-21200 213 21201-21300 214 21301-21400 215 21401-21500 216 21501-21600 217 21601-21700 218 21701-21800 219 21801-21900 220 21901-22000 221 22001-22100 222 22101-22200 223 22201-22300 224 22301-22400 225 22401-22500 226 22501-22600 227 22601-22700 228 22701-22800 229 22801-22900 230 22901-23000 231 23001-23100 232 23101-23200 233 23201-23300 234 23301-23400 235 23401-23500 236 23501-23600 237 23601-23700 238 23701-23800 239 23801-23900 240 23901-24000 241 24001-24100 242 24101-24200 243 24201-24300 244 24301-24400 245 24401-24500 246 24501-24600 247 24601-24700 248 24701-24800 249 24801-24900 250 24901-25000 251 25001-25100 252 25101-25200 253 25201-25300 254 25301-25400 255 25401-25500 256 25501-25600 257 25601-25700 258 25701-25800 259 25801-25900 260 25901-26000 261 26001-26100 262 26101-26200 263 26201-26300 264 26301-26400 265 26401-26500 266 26501-26600 267 26601-26700 268 26701-26800 269 26801-26900 270 26901-27000 271 27001-27100 272 27101-27200 273 27201-27300 274 27301-27400 275 27401-27500 276 27501-27600 277 27601-27700 278 27701-27800 279 27801-27900 280 27901-28000 281 28001-28100 282 28101-28200 283 28201-28300 284 28301-28400 285 28401-28500 286 28501-28600 287 28601-28700 288 28701-28800 289 28801-28900 290 28901-29000 291 29001-29100 292 29101-29200 293 29201-29300 294 29301-29400 295 29401-29500 296 29501-29600 297 29601-29700 298 29701-29800 299 29801-29900 300 29901-30000 301 30001-30100 302 30101-30200 303 30201-30300 304 30301-30400 305 30401-30500 306 30501-30600 307 30601-30700 308 30701-30800 309 30801-30900 310 30901-31000 311 31001-31100 312 31101-31200 313 31201-31300 314 31301-31400 315 31401-31500 316 31501-31600 317 31601-31700 318 31701-31800 319 31801-31900 320 31901-32000 321 32001-32100 322 32101-32200 323 32201-32300 324 32301-32400 325 32401-32500 326 32501-32600 327 32601-32700 328 32701-32800 329 32801-32900 330 32901-33000 331 33001-33100 332 33101-33200 333 33201-33300 334 33301-33400 335 33401-33500 336 33501-33600 337 33601-33700 338 33701-33800 339 33801-33900 340 33901-34000 341 34001-34100 342 34101-34200 343 34201-34300 344 34301-34400 345 34401-34500 346 34501-34600 347 34601-34700 348 34701-34800 349 34801-34900 350 34901-35000 351 35001-35100 352 35101-35200 353 35201-35300 354 35301-35400 355 35401-35500 356 35501-35600 357 35601-35700 358 35701-35800 359 35801-35900 360 35901-36000 361 36001-36100 362 36101-36200 363 36201-36300 364 36301-36400 365 36401-36500 366 36501-36600 367 36601-36700 368 36701-36800 369 36801-36900 370 36901-37000 371 37001-37100 372 37101-37200 373 37201-37300 374 37301-37400 375 37401-37500 376 37501-37600 377 37601-37700 378 37701-37800 379 37801-37900 380 37901-38000 381 38001-38100 382 38101-38200 383 38201-38300 384 38301-38400 385 38401-38500 386 38501-38600 387 38601-38700 388 38701-38800 389 38801-38900 390 38901-39000 391 39001-39100 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