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renumbering the theorems
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prabau committed Mar 4, 2025
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9 changes: 7 additions & 2 deletions theorems/T000615.md
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@@ -1,9 +1,14 @@
---
uid: T000615
if:
P000053: true
and:
- P000110: true
- P000001: true
then:
P000102: true
refs:
- mathse: 5041858
name: Is every developable space semimetrizable?
---

Every metric is a semi-metric.
See {{mathse:5041858}}.
10 changes: 4 additions & 6 deletions theorems/T000711.md
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Expand Up @@ -4,11 +4,9 @@ if:
P000110: true
then:
P000135: true
refs:
- mathse: 5041859
name: Answer to "Is every developable space semimetrizable?"
---

Let $x,y\in X$ and let $U$ be an open set such that $x\in U$ and $y\notin U$.
If $(\mathscr U_n)_{n\ge 1}$ is a development for $X$,
there is some $n$ such that $\operatorname{st}(x,\mathscr U_n)\subseteq U$,
and therefore $y\notin\operatorname{st}(x,\mathscr U_n)$.
Thus no member of $\mathscr U_n$ contains both $x$ and $y$.
Any open set $V\in\mathscr U_n$ with $y\in V$ will then satisfy $x\notin V$.
See Lemma in {{mathse:5041859}}.
9 changes: 3 additions & 6 deletions theorems/T000712.md
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@@ -1,12 +1,9 @@
---
uid: T000712
if:
and:
- P000110: true
- P000002: true
P000121: true
then:
P000102: true
P000110: true
---

writing mathse post ...

Letting $\mathscr U_n$ be the collection of all open balls of radius $1/n$ gives a development for $X$.
19 changes: 16 additions & 3 deletions theorems/T000713.md
Original file line number Diff line number Diff line change
@@ -1,9 +1,22 @@
---
uid: T000713
if:
P000121: true
and:
- P000088: true
- P000110: true
then:
P000110: true
P000121: true
refs:
- zb: "0684.54001"
name: General Topology (Engelking, 1989)
---

Letting $\mathscr U_n$ be the collection of all open balls of radius $1/n$ gives a development for $X$.
This is essentially one of Bing's metrization theorems.

Suppose $X$ satisfies the hypotheses.
Since {T711}, we can add {P135} to the hypotheses.

Passing to the Kolmogorov quotient, it is equivalent to show that
{P88} {P110} {P2} spaces are {P53}.
This is exactly Theorem 5.4.1 in {{zb:0684.54001}},
which assumes {P2} as part of the definition of {P88}.
18 changes: 5 additions & 13 deletions theorems/T000714.md
Original file line number Diff line number Diff line change
Expand Up @@ -2,21 +2,13 @@
uid: T000714
if:
and:
- P000088: true
- P000018: true
- P000110: true
then:
P000121: true
P000027: true
refs:
- zb: "0684.54001"
name: General Topology (Engelking, 1989)
- mathse: 148565
name: Lindelof developable spaces are second countable
---

This is essentially one of Bing's metrization theorems.

Suppose $X$ satisfies the hypotheses.
Since {T711}, we can add {P135} to the hypotheses.

Passing to the Kolmogorov quotient, it is equivalent to show that
{P88} {P110} {P2} spaces are {P53}.
This is exactly Theorem 5.4.1 in {{zb:0684.54001}},
which assumes {P2} as part of the definition of {P88}.
See {{mathse:148565}}.
11 changes: 3 additions & 8 deletions theorems/T000715.md
Original file line number Diff line number Diff line change
@@ -1,14 +1,9 @@
---
uid: T000715
if:
and:
- P000018: true
- P000110: true
P000113: true
then:
P000027: true
refs:
- mathse: 148565
name: Lindelof developable spaces are second countable
P000110: true
---

See {{mathse:148565}}.
By definition.
2 changes: 1 addition & 1 deletion theorems/T000716.md
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Expand Up @@ -3,7 +3,7 @@ uid: T000716
if:
P000113: true
then:
P000110: true
P000005: true
---

By definition.
6 changes: 4 additions & 2 deletions theorems/T000717.md
Original file line number Diff line number Diff line change
@@ -1,9 +1,11 @@
---
uid: T000717
if:
P000113: true
and:
- P000110: true
- P000005: true
then:
P000005: true
P000113: true
---

By definition.
11 changes: 0 additions & 11 deletions theorems/T000718.md

This file was deleted.

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