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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -1,14 +1,9 @@ | ||
--- | ||
uid: T000553 | ||
if: | ||
and: | ||
- P000001: true | ||
- P000090: true | ||
- P000027: true | ||
P000196: true | ||
then: | ||
P000057: true | ||
P000042: true | ||
--- | ||
|
||
In an {P90} space, the smallest basis is the set of smallest neighborhoods of points. | ||
When it is also {P1}, these are all distinct, so they are in bijection with the set of points. | ||
Thus, such a space has a countable basis iff it is countable. | ||
Every subset of a {P196} space is {P40}, and {T38}. |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,11 @@ | ||
--- | ||
uid: T000555 | ||
if: | ||
and: | ||
- P000196: true | ||
- P000176: true | ||
then: | ||
P000044: false | ||
--- | ||
|
||
Since any subset is connected, any partition into non-singletons suffices. |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,12 @@ | ||
--- | ||
uid: T000556 | ||
if: | ||
and: | ||
- P000196: true | ||
- P000016: true | ||
then: | ||
P000146: true | ||
--- | ||
If a {P196} space is {P16}, then it must have a second largest open set | ||
(otherwise, $\mathcal T_X\setminus\{X\}$ would be totally ordered with no upper bound and therefore an open cover with no finite subcover). | ||
Thus, any open cover must contain $X$, so it admits a refinement containing $X$ as the only nonempty set. |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,14 @@ | ||
--- | ||
uid: T000557 | ||
if: | ||
and: | ||
- P000001: true | ||
- P000090: true | ||
- P000027: true | ||
then: | ||
P000057: true | ||
--- | ||
|
||
In an {P90} space, the smallest basis is the set of smallest neighborhoods of points. | ||
When it is also {P1}, these are all distinct, so they are in bijection with the set of points. | ||
Thus, such a space has a countable basis iff it is countable. |