diff --git a/theorems/T000552.md b/theorems/T000552.md index 2834aee9a..4c3be64db 100644 --- a/theorems/T000552.md +++ b/theorems/T000552.md @@ -8,7 +8,6 @@ if: then: P000129: 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). To be {P86}, no points can lie in this second-largest set, so the space is {P129}. diff --git a/theorems/T000553.md b/theorems/T000553.md index 7d6bf90ad..6d31adfc9 100644 --- a/theorems/T000553.md +++ b/theorems/T000553.md @@ -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}. diff --git a/theorems/T000554.md b/theorems/T000554.md index e2f808bc1..487604d1c 100644 --- a/theorems/T000554.md +++ b/theorems/T000554.md @@ -12,4 +12,4 @@ refs: - doi: 10.1017/9781316543870 name: Spectral spaces (Dickmann, Schwartz, Tressl) --- -Shown in Proposition 1.6.7 of {{doi:10.1017/9781316543870}}. +Shown in Proposition 1.6.7 of {{doi:10.1017/9781316543870}}. In particular, it follows that the specialization order is order-isomorphic to a non-limit ordinal. diff --git a/theorems/T000555.md b/theorems/T000555.md new file mode 100644 index 000000000..4f896a3e8 --- /dev/null +++ b/theorems/T000555.md @@ -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. diff --git a/theorems/T000556.md b/theorems/T000556.md new file mode 100644 index 000000000..6d869685f --- /dev/null +++ b/theorems/T000556.md @@ -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. diff --git a/theorems/T000557.md b/theorems/T000557.md new file mode 100644 index 000000000..bd802b06c --- /dev/null +++ b/theorems/T000557.md @@ -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.