diff --git a/properties/P000185.md b/properties/P000185.md index 2315f680a..325c99d54 100644 --- a/properties/P000185.md +++ b/properties/P000185.md @@ -2,8 +2,10 @@ uid: P000185 name: Partition topology refs: - - doi: 10.1007/978-1-4612-6290-9 - name: Counterexamples in Topology +- doi: 10.1007/978-1-4612-6290-9 + name: Counterexamples in Topology +- doi: 10.5186/aasfm.1977.0321 + name: On ultrapseudocompact and related spaces (T. Nieminen) --- Any of the following equivalent properties holds: @@ -14,5 +16,7 @@ Any of the following equivalent properties holds: - The space's Kolmogorov quotient is {P52}. - The space is the disjoint union of a collection of {P129} spaces. +For proof of the equivalences and further characterizations, see section 13 of {{doi:10.5186/aasfm.1977.0321}}. + Defined as example #5 ("Partition Topology") in {{doi:10.1007/978-1-4612-6290-9}}. diff --git a/properties/P000196.md b/properties/P000196.md new file mode 100644 index 000000000..957361c34 --- /dev/null +++ b/properties/P000196.md @@ -0,0 +1,18 @@ +--- +uid: P000196 +name: Hereditarily connected +aliases: +- Totally ordered topology +refs: +- doi: 10.5186/aasfm.1977.0321 + name: On ultrapseudocompact and related spaces (T. Nieminen) +--- + +Any of the following equivalent properties holds: + +- Any subspace is connected. +- The open sets are totally ordered by inclusion. +- The closed sets are totally ordered by inclusion. +- The specialization preorder is total. + +For proof of the equivalences and further characterizations, see section 12 of {{doi:10.5186/aasfm.1977.0321}}. diff --git a/spaces/S000187/properties/P000196.md b/spaces/S000187/properties/P000196.md new file mode 100644 index 000000000..e29f17433 --- /dev/null +++ b/spaces/S000187/properties/P000196.md @@ -0,0 +1,7 @@ +--- +space: S000187 +property: P000196 +value: true +--- + +By construction. diff --git a/spaces/S000199/properties/P000002.md b/spaces/S000199/properties/P000002.md deleted file mode 100644 index e7a65eb1b..000000000 --- a/spaces/S000199/properties/P000002.md +++ /dev/null @@ -1,7 +0,0 @@ ---- -space: S000199 -property: P000002 -value: false ---- - -Every neighborhood of $1$ is a neighborhood of $0$. diff --git a/spaces/S000199/properties/P000014.md b/spaces/S000199/properties/P000014.md deleted file mode 100644 index 4d96693a4..000000000 --- a/spaces/S000199/properties/P000014.md +++ /dev/null @@ -1,10 +0,0 @@ ---- -space: S000199 -property: P000014 -value: true ---- - -The collection of closed sets is a chain under inclusion; -that is, -for each pair of closed sets, one is contained in the other. -Therefore every subspace is vacuously {P13}. diff --git a/spaces/S000199/properties/P000039.md b/spaces/S000199/properties/P000039.md deleted file mode 100644 index 7edff5528..000000000 --- a/spaces/S000199/properties/P000039.md +++ /dev/null @@ -1,9 +0,0 @@ ---- -space: S000199 -property: P000039 -value: true ---- - -The topology is a chain under inclusion; -that is, -for each pair of open sets, one is contained in the other. diff --git a/spaces/S000199/properties/P000051.md b/spaces/S000199/properties/P000051.md new file mode 100644 index 000000000..ef0361c92 --- /dev/null +++ b/spaces/S000199/properties/P000051.md @@ -0,0 +1,7 @@ +--- +space: S000199 +property: P000051 +value: true +--- +Since $\omega$ is well-ordered, a nonempty set $Y\subseteq\omega$ has a least element $\alpha$. +Then $\alpha$ is isolated in $Y$ since $[0,\alpha+1)\cap Y=\{\alpha\}$. diff --git a/spaces/S000199/properties/P000086.md b/spaces/S000199/properties/P000086.md deleted file mode 100644 index 557402636..000000000 --- a/spaces/S000199/properties/P000086.md +++ /dev/null @@ -1,7 +0,0 @@ ---- -space: S000199 -property: P000086 -value: false ---- - -$0$ belongs to every nonempty open set, but $1$ does not belong to $(\leftarrow,0]$. diff --git a/spaces/S000199/properties/P000136.md b/spaces/S000199/properties/P000136.md new file mode 100644 index 000000000..cd74fca5d --- /dev/null +++ b/spaces/S000199/properties/P000136.md @@ -0,0 +1,7 @@ +--- +space: S000199 +property: P000136 +value: true +--- + +Every infinite subspace is homeomorphic to the space itself, and any open cover not containing $\omega$ must be an infinite set of left rays and so cannot have a finite subcover. diff --git a/spaces/S000187/properties/P000039.md b/spaces/S000199/properties/P000181.md similarity index 52% rename from spaces/S000187/properties/P000039.md rename to spaces/S000199/properties/P000181.md index 7d239f6d7..21e3c555e 100644 --- a/spaces/S000187/properties/P000039.md +++ b/spaces/S000199/properties/P000181.md @@ -1,6 +1,6 @@ --- -space: S000187 -property: P000039 +space: S000199 +property: P000181 value: true --- diff --git a/spaces/S000199/properties/P000196.md b/spaces/S000199/properties/P000196.md new file mode 100644 index 000000000..cc091bd9f --- /dev/null +++ b/spaces/S000199/properties/P000196.md @@ -0,0 +1,7 @@ +--- +space: S000199 +property: P000196 +value: true +--- + +By construction. diff --git a/spaces/S000200/properties/P000002.md b/spaces/S000200/properties/P000002.md deleted file mode 100644 index ea4e1784b..000000000 --- a/spaces/S000200/properties/P000002.md +++ /dev/null @@ -1,7 +0,0 @@ ---- -space: S000200 -property: P000002 -value: false ---- - -Every neighborhood of $0$ is a neighborhood of $1$. diff --git a/spaces/S000200/properties/P000014.md b/spaces/S000200/properties/P000014.md deleted file mode 100644 index b48008995..000000000 --- a/spaces/S000200/properties/P000014.md +++ /dev/null @@ -1,10 +0,0 @@ ---- -space: S000200 -property: P000014 -value: true ---- - -The collection of closed sets is a chain under inclusion; -that is, -for each pair of closed sets, one is contained in the other. -Therefore every subspace is vacuously {P13}. diff --git a/spaces/S000200/properties/P000016.md b/spaces/S000200/properties/P000016.md new file mode 100644 index 000000000..fc6e95572 --- /dev/null +++ b/spaces/S000200/properties/P000016.md @@ -0,0 +1,7 @@ +--- +space: S000200 +property: P000016 +value: true +--- + +Any open cover must contain $\omega$. diff --git a/spaces/S000200/properties/P000039.md b/spaces/S000200/properties/P000039.md deleted file mode 100644 index ee8b420d9..000000000 --- a/spaces/S000200/properties/P000039.md +++ /dev/null @@ -1,9 +0,0 @@ ---- -space: S000200 -property: P000039 -value: true ---- - -The topology is a chain under inclusion; -that is, -for each pair of open sets, one is contained in the other. diff --git a/spaces/S000200/properties/P000086.md b/spaces/S000200/properties/P000086.md deleted file mode 100644 index d470218f4..000000000 --- a/spaces/S000200/properties/P000086.md +++ /dev/null @@ -1,8 +0,0 @@ ---- -space: S000200 -property: P000086 -value: false ---- - -$0$ belongs to only one open set $[0,\infty)$, but $1$ belongs to two open sets $[0,\rightarrow)$ -and $[1,\rightarrow)$. diff --git a/spaces/S000187/properties/P000040.md b/spaces/S000200/properties/P000181.md similarity index 52% rename from spaces/S000187/properties/P000040.md rename to spaces/S000200/properties/P000181.md index 86b6aca72..2018d047e 100644 --- a/spaces/S000187/properties/P000040.md +++ b/spaces/S000200/properties/P000181.md @@ -1,6 +1,6 @@ --- -space: S000187 -property: P000040 +space: S000200 +property: P000181 value: true --- diff --git a/spaces/S000200/properties/P000196.md b/spaces/S000200/properties/P000196.md new file mode 100644 index 000000000..d3e2d8cf9 --- /dev/null +++ b/spaces/S000200/properties/P000196.md @@ -0,0 +1,7 @@ +--- +space: S000200 +property: P000196 +value: true +--- + +By construction. diff --git a/theorems/T000546.md b/theorems/T000546.md new file mode 100644 index 000000000..c806a6ee6 --- /dev/null +++ b/theorems/T000546.md @@ -0,0 +1,9 @@ +--- +uid: T000546 +if: + P000196: true +then: + P000039: true +--- + +The open sets are totally ordered by set inclusion and thus no two nonempty ones are disjoint. diff --git a/theorems/T000547.md b/theorems/T000547.md new file mode 100644 index 000000000..3803e584f --- /dev/null +++ b/theorems/T000547.md @@ -0,0 +1,9 @@ +--- +uid: T000547 +if: + P000196: true +then: + P000014: true +--- + +Any {P196} space is trivially {P13} (as there are no disjoint closed sets), so all subspaces are as well. diff --git a/theorems/T000548.md b/theorems/T000548.md new file mode 100644 index 000000000..eb5743d0b --- /dev/null +++ b/theorems/T000548.md @@ -0,0 +1,14 @@ +--- +uid: T000548 +if: + and: + - P000039: true + - P000014: true +then: + P000196: true +refs: +- doi: 10.5186/aasfm.1977.0321 + name: On ultrapseudocompact and related spaces (T. Nieminen) +--- + +See condition (10) of theorem 23 at {{doi:10.5186/aasfm.1977.0321}} (reading $T_5$ as {P14}). diff --git a/theorems/T000549.md b/theorems/T000549.md new file mode 100644 index 000000000..69586ecab --- /dev/null +++ b/theorems/T000549.md @@ -0,0 +1,9 @@ +--- +uid: T000549 +if: + P000196: true +then: + P000174: true +--- + +The topology is totally ordered by inclusion, so the set of open neighborhoods of any point is as well. diff --git a/theorems/T000550.md b/theorems/T000550.md new file mode 100644 index 000000000..3ab1ae577 --- /dev/null +++ b/theorems/T000550.md @@ -0,0 +1,12 @@ +--- +uid: T000550 +if: + and: + - P000193: true + - P000039: true +then: + P000146: true +--- + +In a {P39} space $X$, the closure of every nonempty open set is $X$, so any open cover that admits a shrinking must contain $X$ (as otherwise each of its open sets could only contain the closure of $\varnothing$). +Thus, any such open cover admits an open refinement to the partition $\{X\}$. diff --git a/theorems/T000551.md b/theorems/T000551.md new file mode 100644 index 000000000..1c5774c8a --- /dev/null +++ b/theorems/T000551.md @@ -0,0 +1,12 @@ +--- +uid: T000551 +if: + and: + - P000196: true + - P000093: true + - P000057: false +then: + P000114: true +--- + +By {P93} choose a countable open neighborhood of each point. So $X$ can be covered by a family of countable sets, forming a chain under inclusion by {P196}. And the union of a chain of countable sets has cardinality at most $\aleph_1$ (see {{mathse:342091}} for example). diff --git a/theorems/T000552.md b/theorems/T000552.md new file mode 100644 index 000000000..532f52226 --- /dev/null +++ b/theorems/T000552.md @@ -0,0 +1,11 @@ +--- +uid: T000552 +if: + and: + - P000146: true + - P000036: true + - P000086: true +then: + P000129: true +--- +Any clopen partition of a {P36} space $X$ must contain $X$, so every open cover admitting a clopen partition as refinement must contain $X$. Thus, the union of all open sets except for $X$ cannot equal $X$ (as that would be an open cover not containing $X$), so some points have $X$ as their only neighborhood. By homogeneity, this must then be true of all points, i.e. the space is {P129}. diff --git a/theorems/T000553.md b/theorems/T000553.md new file mode 100644 index 000000000..6d31adfc9 --- /dev/null +++ b/theorems/T000553.md @@ -0,0 +1,9 @@ +--- +uid: T000553 +if: + P000196: true +then: + P000042: true +--- + +Every subset of a {P196} space is {P40}, and {T38}. diff --git a/theorems/T000554.md b/theorems/T000554.md new file mode 100644 index 000000000..fc39050ba --- /dev/null +++ b/theorems/T000554.md @@ -0,0 +1,17 @@ +--- +uid: T000554 +if: + and: + - P000196: true + - P000016: true + - P000073: true + - P000090: true +then: + P000075: true +refs: +- doi: 10.1017/9781316543870 + name: Spectral spaces (Dickmann, Schwartz, Tressl) +--- +Shown in Proposition 1.6.7 of {{doi:10.1017/9781316543870}}. + +Furthermore, if the space is nonempty, its specialization order is order-isomorphic to a successor ordinal $\lambda$ and the space is homeomorphic to $\lambda$ with the left-ray topology having the collection of intervals $[0,\alpha]$ ($\alpha\in\lambda$) as a base. diff --git a/theorems/T000555.md b/theorems/T000555.md new file mode 100644 index 000000000..845d480a0 --- /dev/null +++ b/theorems/T000555.md @@ -0,0 +1,10 @@ +--- +uid: T000555 +if: + and: + - P000196: true + - P000176: true +then: + P000044: false +--- +$X$ has two disjoint subsets, each with at least two points, and each of the subsets is connected. diff --git a/theorems/T000556.md b/theorems/T000556.md new file mode 100644 index 000000000..79a0abbd0 --- /dev/null +++ b/theorems/T000556.md @@ -0,0 +1,10 @@ +--- +uid: T000556 +if: + and: + - P000146: true + - P000036: true +then: + P000020: true +--- +Any clopen partition of a {P36} space $X$ must contain $X$, so to admit clopen refinements every open cover must contain $X$. Thus, the union of all open sets except for $X$ cannot equal $X$ (as that would be an open cover not containing $X$), so any sequence converges to all points outside of that union (whose only neighborhood is $X$). 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.