diff --git a/properties/P000185.md b/properties/P000185.md index 540e00090..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: @@ -14,7 +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 further characterizations, see theorem 25 of https://www.acadsci.fi/mathematica/Vol03/vol03pp185-205.pdf. +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 index 16ef0f188..957361c34 100644 --- a/properties/P000196.md +++ b/properties/P000196.md @@ -4,14 +4,15 @@ name: Hereditarily connected aliases: - Totally ordered topology refs: -- zb: "0396.54009" +- 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 set inclusion. +- The open sets are totally ordered by inclusion. +- The closed sets are totally ordered by inclusion. - The specialization preorder is total. -For further characterizations, see theorem 22 of https://www.acadsci.fi/mathematica/Vol03/vol03pp185-205.pdf. +For proof of the equivalences and further characterizations, see section 12 of {{doi:10.5186/aasfm.1977.0321}}. diff --git a/theorems/T000547.md b/theorems/T000547.md index 75dec4a9d..3803e584f 100644 --- a/theorems/T000547.md +++ b/theorems/T000547.md @@ -6,4 +6,4 @@ then: P000014: true --- -Any {P196} space is trivially {P13} (as there are no disoint closed sets), and the property is hereditary, so all subspaces are as well. +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 index ecdd9e1fa..eb5743d0b 100644 --- a/theorems/T000548.md +++ b/theorems/T000548.md @@ -7,8 +7,8 @@ if: then: P000196: true refs: -- zb: "0396.54009" +- doi: 10.5186/aasfm.1977.0321 name: On ultrapseudocompact and related spaces (T. Nieminen) --- -See theorem 23 at https://www.acadsci.fi/mathematica/Vol03/vol03pp185-205.pdf (reading $T_5$ as {P14}). +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 index eccf8b6c1..69586ecab 100644 --- a/theorems/T000549.md +++ b/theorems/T000549.md @@ -6,4 +6,4 @@ then: P000174: true --- -The topology is totally ordered by set inclusion, so the set of open neighborhoods of any point is as well. +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 index 25e614d9e..5ae939464 100644 --- a/theorems/T000550.md +++ b/theorems/T000550.md @@ -2,10 +2,10 @@ uid: T000550 if: and: - - P000196: true - - P000057: true + - P000193: true + - P000039: true then: - P000027: true + P000146: true --- -There can be no more open sets in a {P196} space than there are points. +In a {P39} space $X$, every nonempty open set is dense, so to admit a shrinking, every open cover must contain $X$. Thus, any open cover admits a clopen refinement. diff --git a/theorems/T000555.md b/theorems/T000555.md index 4f896a3e8..845d480a0 100644 --- a/theorems/T000555.md +++ b/theorems/T000555.md @@ -7,5 +7,4 @@ if: then: P000044: false --- - -Since any subset is connected, any partition into non-singletons suffices. +$X$ 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 index 6d869685f..905ffc09a 100644 --- a/theorems/T000556.md +++ b/theorems/T000556.md @@ -2,11 +2,9 @@ uid: T000556 if: and: - - P000196: true - - P000016: true + - P000146: true + - P000036: true then: - P000146: true + P000016: 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. +Any clopen partition of a {P36} space $X$ must contain $X$, so to admit clopen refinements every open cover must contain $X$. Thus, $\{X\}$ is a finite subcover. diff --git a/theorems/T000558.md b/theorems/T000558.md new file mode 100644 index 000000000..0cdd2f179 --- /dev/null +++ b/theorems/T000558.md @@ -0,0 +1,10 @@ +--- +uid: T000558 +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/T000559.md b/theorems/T000559.md new file mode 100644 index 000000000..1027c0504 --- /dev/null +++ b/theorems/T000559.md @@ -0,0 +1,8 @@ +--- +uid: T000558 +if: + P000040: true +then: + P000088: true +--- +In an {P40} space, since any two nonempty closed sets intersect, any discrete family of closed sets can only contain one nonempty set (which is contained in the open set $X$).