From bd051f85ece898083235e54186087ff979cf2d19 Mon Sep 17 00:00:00 2001 From: Patrick Rabau <70125716+prabau@users.noreply.github.com> Date: Tue, 3 Feb 2026 18:50:18 -0500 Subject: [PATCH 1/6] alpha_i preserved by finite products --- properties/P000210.md | 3 +++ properties/P000211.md | 3 +++ properties/P000212.md | 3 +++ properties/P000213.md | 3 +++ properties/P000214.md | 3 +++ spaces/S000078/README.md | 3 ++- spaces/S000078/properties/P000081.md | 3 ++- spaces/S000078/properties/P000210.md | 8 ++++++++ spaces/S000091/properties/P000210.md | 9 +++++++++ spaces/S000191/properties/P000210.md | 8 ++++++++ spaces/S000218/properties/P000210.md | 8 ++++++++ 11 files changed, 52 insertions(+), 2 deletions(-) create mode 100644 spaces/S000078/properties/P000210.md create mode 100644 spaces/S000091/properties/P000210.md create mode 100644 spaces/S000191/properties/P000210.md create mode 100644 spaces/S000218/properties/P000210.md diff --git a/properties/P000210.md b/properties/P000210.md index 7ae5540a4a..305f30f4fb 100644 --- a/properties/P000210.md +++ b/properties/P000210.md @@ -10,6 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) + - mathse: 5122756 + name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -35,3 +37,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- This property is preserved by finite products (see {{mathse:5122756}}). diff --git a/properties/P000211.md b/properties/P000211.md index 45bdf65186..f358bce0b8 100644 --- a/properties/P000211.md +++ b/properties/P000211.md @@ -8,6 +8,8 @@ refs: name: Arhangel'skii sheaf amalgamations in topological groups (Tsaban & Zdomskyy) - zb: "0774.54019" name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) + - mathse: 5122756 + name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? --- For every $x\in X$ and every sequence of pairwise disjoint countably infinite sets @@ -34,3 +36,4 @@ This property was introduced by Nyikos in {{zb:0774.54019}}. #### Meta-properties - This property is hereditary. +- This property is preserved by finite products (see {{mathse:5122756}}). diff --git a/properties/P000212.md b/properties/P000212.md index 0489e2f72f..5a77e7cc44 100644 --- a/properties/P000212.md +++ b/properties/P000212.md @@ -10,6 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) + - mathse: 5122756 + name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -34,3 +36,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- This property is preserved by finite products (see {{mathse:5122756}}). diff --git a/properties/P000213.md b/properties/P000213.md index 8e5da280e1..6bce164dcf 100644 --- a/properties/P000213.md +++ b/properties/P000213.md @@ -10,6 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) + - mathse: 5122756 + name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -34,3 +36,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- This property is preserved by finite products (see {{mathse:5122756}}). diff --git a/properties/P000214.md b/properties/P000214.md index 47a4b1e41b..a529833ba2 100644 --- a/properties/P000214.md +++ b/properties/P000214.md @@ -10,6 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) + - mathse: 5122756 + name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -34,3 +36,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- This property is preserved by finite products (see {{mathse:5122756}}). diff --git a/spaces/S000078/README.md b/spaces/S000078/README.md index c63c3adda2..eba30e4fc6 100644 --- a/spaces/S000078/README.md +++ b/spaces/S000078/README.md @@ -9,7 +9,8 @@ refs: name: Tychonoff plank on Wikipedia --- -The space $[0,\omega_1] \times [0,\omega]$ where each factor has the order topology. +The space $[0,\omega_1] \times [0,\omega]$ where each factor has the order topology; +that is, the product of {S36} and {S20}. Defined as counterexample #86 ("Tychonoff Plank") in {{zb:0386.54001}}. diff --git a/spaces/S000078/properties/P000081.md b/spaces/S000078/properties/P000081.md index 8b6847144e..8b002b025f 100644 --- a/spaces/S000078/properties/P000081.md +++ b/spaces/S000078/properties/P000081.md @@ -7,4 +7,5 @@ refs: name: Counterexamples in Topology --- -{P81} is a hereditary property. The space contains as a subspace a copy of {S36}, which is not {P81}. +{S36} is homeomorphic to a subspace of $X$ +and {S36|P81}. diff --git a/spaces/S000078/properties/P000210.md b/spaces/S000078/properties/P000210.md new file mode 100644 index 0000000000..cdc82fba96 --- /dev/null +++ b/spaces/S000078/properties/P000210.md @@ -0,0 +1,8 @@ +--- +space: S000078 +property: P000210 +value: true +--- + +{S36|P210} and {S20|P210}, +hence so is their product. diff --git a/spaces/S000091/properties/P000210.md b/spaces/S000091/properties/P000210.md new file mode 100644 index 0000000000..545a3b93ce --- /dev/null +++ b/spaces/S000091/properties/P000210.md @@ -0,0 +1,9 @@ +--- +space: S000091 +property: P000210 +value: true +--- + +{S154|P210} and +{S20|P210}, +hence so is their product, which contains $X$ as a homeomorphic subspace. diff --git a/spaces/S000191/properties/P000210.md b/spaces/S000191/properties/P000210.md new file mode 100644 index 0000000000..ec450685bf --- /dev/null +++ b/spaces/S000191/properties/P000210.md @@ -0,0 +1,8 @@ +--- +space: S000191 +property: P000210 +value: true +--- + +{S155|P210} and {S20|P210}, +hence so is their product. diff --git a/spaces/S000218/properties/P000210.md b/spaces/S000218/properties/P000210.md new file mode 100644 index 0000000000..e8c9f3b448 --- /dev/null +++ b/spaces/S000218/properties/P000210.md @@ -0,0 +1,8 @@ +--- +space: S000218 +property: P000210 +value: true +--- + +{S35|P210} and {S36|P210}, +hence so is their product. From b98191eaf92bb2e498e2d1823516747e99b86426 Mon Sep 17 00:00:00 2001 From: Patrick Rabau <70125716+prabau@users.noreply.github.com> Date: Wed, 4 Feb 2026 01:16:08 -0500 Subject: [PATCH 2/6] alpha_4 not preserved by products --- properties/P000214.md | 3 --- 1 file changed, 3 deletions(-) diff --git a/properties/P000214.md b/properties/P000214.md index a529833ba2..47a4b1e41b 100644 --- a/properties/P000214.md +++ b/properties/P000214.md @@ -10,8 +10,6 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - - mathse: 5122756 - name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -36,4 +34,3 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. -- This property is preserved by finite products (see {{mathse:5122756}}). From f5c87213c7820423ee5804ef27a8d937b37571e8 Mon Sep 17 00:00:00 2001 From: Patrick Rabau <70125716+prabau@users.noreply.github.com> Date: Mon, 9 Feb 2026 02:33:46 -0500 Subject: [PATCH 3/6] preserved by disjoint unions --- properties/P000210.md | 1 + properties/P000211.md | 1 + properties/P000212.md | 1 + properties/P000213.md | 1 + properties/P000214.md | 1 + 5 files changed, 5 insertions(+) diff --git a/properties/P000210.md b/properties/P000210.md index 305f30f4fb..a371af8414 100644 --- a/properties/P000210.md +++ b/properties/P000210.md @@ -38,3 +38,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). - This property is hereditary. - This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000211.md b/properties/P000211.md index f358bce0b8..6e7147b500 100644 --- a/properties/P000211.md +++ b/properties/P000211.md @@ -37,3 +37,4 @@ This property was introduced by Nyikos in {{zb:0774.54019}}. - This property is hereditary. - This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000212.md b/properties/P000212.md index 5a77e7cc44..08c4068626 100644 --- a/properties/P000212.md +++ b/properties/P000212.md @@ -37,3 +37,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). - This property is hereditary. - This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000213.md b/properties/P000213.md index 6bce164dcf..d42d82e5f6 100644 --- a/properties/P000213.md +++ b/properties/P000213.md @@ -37,3 +37,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). - This property is hereditary. - This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000214.md b/properties/P000214.md index 47a4b1e41b..8e56fc5d09 100644 --- a/properties/P000214.md +++ b/properties/P000214.md @@ -34,3 +34,4 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- This property is preserved by arbitrary disjoint unions. From 8837c58a47bac00c4e500a32f4b6d2603579e0d6 Mon Sep 17 00:00:00 2001 From: Patrick Rabau <70125716+prabau@users.noreply.github.com> Date: Sun, 15 Feb 2026 19:38:31 -0500 Subject: [PATCH 4/6] metaprop for Kolmogorov quotient --- properties/P000210.md | 1 + properties/P000211.md | 1 + properties/P000212.md | 1 + properties/P000213.md | 1 + properties/P000214.md | 1 + 5 files changed, 5 insertions(+) diff --git a/properties/P000210.md b/properties/P000210.md index a371af8414..6326f39e9a 100644 --- a/properties/P000210.md +++ b/properties/P000210.md @@ -37,5 +37,6 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000211.md b/properties/P000211.md index 6e7147b500..780e51f547 100644 --- a/properties/P000211.md +++ b/properties/P000211.md @@ -36,5 +36,6 @@ This property was introduced by Nyikos in {{zb:0774.54019}}. #### Meta-properties - This property is hereditary. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000212.md b/properties/P000212.md index 08c4068626..286ef9318b 100644 --- a/properties/P000212.md +++ b/properties/P000212.md @@ -36,5 +36,6 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000213.md b/properties/P000213.md index d42d82e5f6..e0d5ca8210 100644 --- a/properties/P000213.md +++ b/properties/P000213.md @@ -36,5 +36,6 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000214.md b/properties/P000214.md index 8e56fc5d09..dd25d3dbda 100644 --- a/properties/P000214.md +++ b/properties/P000214.md @@ -34,4 +34,5 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. - This property is preserved by arbitrary disjoint unions. From 66e2fedbf6cdd4d0b3bd5b7a4a847aefdcbc193c Mon Sep 17 00:00:00 2001 From: Patrick Rabau <70125716+prabau@users.noreply.github.com> Date: Sun, 15 Feb 2026 23:16:30 -0500 Subject: [PATCH 5/6] refs for Kolmogorov quotient --- properties/P000210.md | 4 +++- properties/P000211.md | 4 +++- properties/P000212.md | 4 +++- properties/P000213.md | 4 +++- properties/P000214.md | 4 +++- 5 files changed, 15 insertions(+), 5 deletions(-) diff --git a/properties/P000210.md b/properties/P000210.md index 6326f39e9a..0479367145 100644 --- a/properties/P000210.md +++ b/properties/P000210.md @@ -12,6 +12,8 @@ refs: name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - mathse: 5122756 name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5123855 + name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -37,6 +39,6 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. -- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000211.md b/properties/P000211.md index 780e51f547..454ba409f7 100644 --- a/properties/P000211.md +++ b/properties/P000211.md @@ -10,6 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - mathse: 5122756 name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5123855 + name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- For every $x\in X$ and every sequence of pairwise disjoint countably infinite sets @@ -36,6 +38,6 @@ This property was introduced by Nyikos in {{zb:0774.54019}}. #### Meta-properties - This property is hereditary. -- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000212.md b/properties/P000212.md index 286ef9318b..bb6888a7a8 100644 --- a/properties/P000212.md +++ b/properties/P000212.md @@ -12,6 +12,8 @@ refs: name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - mathse: 5122756 name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5123855 + name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -36,6 +38,6 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. -- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000213.md b/properties/P000213.md index e0d5ca8210..870038a99e 100644 --- a/properties/P000213.md +++ b/properties/P000213.md @@ -12,6 +12,8 @@ refs: name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - mathse: 5122756 name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5123855 + name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -36,6 +38,6 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. -- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). - This property is preserved by finite products (see {{mathse:5122756}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000214.md b/properties/P000214.md index dd25d3dbda..44ffd0b3fd 100644 --- a/properties/P000214.md +++ b/properties/P000214.md @@ -10,6 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) + - mathse: 5123855 + name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- For every $x\in X$ and every sequence of countably infinite sets $S_1,S_2,\dots\subseteq X$ with @@ -34,5 +36,5 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). #### Meta-properties - This property is hereditary. -- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does. +- $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). - This property is preserved by arbitrary disjoint unions. From c85a91a07444d75cbd7b0d7f217a21189b36dcde Mon Sep 17 00:00:00 2001 From: Patrick Rabau <70125716+prabau@users.noreply.github.com> Date: Wed, 4 Mar 2026 02:39:42 -0500 Subject: [PATCH 6/6] countable products; and S181 trait --- properties/P000210.md | 6 +++--- properties/P000211.md | 6 +++--- properties/P000212.md | 6 +++--- properties/P000213.md | 6 +++--- spaces/S000181/properties/P000210.md | 8 ++++++++ 5 files changed, 20 insertions(+), 12 deletions(-) create mode 100644 spaces/S000181/properties/P000210.md diff --git a/properties/P000210.md b/properties/P000210.md index 0479367145..ef0ab1984b 100644 --- a/properties/P000210.md +++ b/properties/P000210.md @@ -10,8 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - - mathse: 5122756 - name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5127008 + name: Answer to "Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products?" - mathse: 5123855 name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- @@ -40,5 +40,5 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). - This property is hereditary. - $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). -- This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by countable products (see {{mathse:5127008}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000211.md b/properties/P000211.md index 454ba409f7..26f257abc3 100644 --- a/properties/P000211.md +++ b/properties/P000211.md @@ -8,8 +8,8 @@ refs: name: Arhangel'skii sheaf amalgamations in topological groups (Tsaban & Zdomskyy) - zb: "0774.54019" name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - - mathse: 5122756 - name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5127008 + name: Answer to "Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products?" - mathse: 5123855 name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- @@ -39,5 +39,5 @@ This property was introduced by Nyikos in {{zb:0774.54019}}. - This property is hereditary. - $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). -- This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by countable products (see {{mathse:5127008}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000212.md b/properties/P000212.md index bb6888a7a8..01dbae50b7 100644 --- a/properties/P000212.md +++ b/properties/P000212.md @@ -10,8 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - - mathse: 5122756 - name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5127008 + name: Answer to "Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products?" - mathse: 5123855 name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- @@ -39,5 +39,5 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). - This property is hereditary. - $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). -- This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by countable products (see {{mathse:5127008}}). - This property is preserved by arbitrary disjoint unions. diff --git a/properties/P000213.md b/properties/P000213.md index 870038a99e..4d5b72ac66 100644 --- a/properties/P000213.md +++ b/properties/P000213.md @@ -10,8 +10,8 @@ refs: name: Subsets of ${}^\omega\omega$ and the Fréchet-Urysohn and $\alpha_i$-properties (P. Nyikos) - zb: "0275.54004" name: The frequency spectrum of a topological space and the classification of spaces (A. V. Arkhangel'skii) - - mathse: 5122756 - name: Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products? + - mathse: 5127008 + name: Answer to "Are the Arkhangel'skii $\alpha_i$ properties preserved by finite products?" - mathse: 5123855 name: Does the Arkhangel'skii $\alpha_1$ property hold for $X$ if it holds for its Kolmogorov quotient? --- @@ -39,5 +39,5 @@ are due to Arkhangel'skii ({{zb:0275.54004}}). - This property is hereditary. - $X$ satisfies this property iff its Kolmogorov quotient $\text{Kol}(X)$ does (see {{mathse:5123855}}). -- This property is preserved by finite products (see {{mathse:5122756}}). +- This property is preserved by countable products (see {{mathse:5127008}}). - This property is preserved by arbitrary disjoint unions. diff --git a/spaces/S000181/properties/P000210.md b/spaces/S000181/properties/P000210.md new file mode 100644 index 0000000000..a40f9cd4dd --- /dev/null +++ b/spaces/S000181/properties/P000210.md @@ -0,0 +1,8 @@ +--- +space: S000181 +property: P000210 +value: true +--- + +$X$ is a subspace of a countable product of {P210} spaces, +since {S36|P210}.