If $X times X$ is normal, then is $X times X times X$ normal?











up vote
4
down vote

favorite
1












I am looking at some topological dimension theory for product spaces, and in trying to construct a certain type of counterexample it's become relevant to consider the question in the title above. I am interested in finding a normal space $X$ whose products with itself is eventually non-normal, but not immediately.



It's not actually important for my application that it happens in three steps as opposed to more. An alternative question would be: Is there a normal space $X$ with $X times X = Y$ normal, but $Y times Y$ is not normal?



The original problem is here:



https://mathoverflow.net/questions/315657/if-textdimx-times-x-2-textdimx-does-textdimxn-n-textdim



Thanks for any help!



As mentioned in a comment below, if we assume that $X$ is a compact Hausdorff space and that $X times X times X$ is completely normal, then $X$ is metrizable. Thus it stands to reason that a compact counterexample may be harder (if not impossible) to construct. The author in the linked paper wonders aloud if the complete normality of $X times X$ is sufficient for the metrizability of $X$, so it may also be advisable to avoid cases where $X times X$ is completely normal.










share|cite|improve this question




















  • 1




    This is not an answer, but somehow related: math.stackexchange.com/q/2872102
    – Paul Frost
    Nov 21 at 8:57










  • Interesting result, I will mention it in an edit.
    – John Samples
    Nov 21 at 10:00















up vote
4
down vote

favorite
1












I am looking at some topological dimension theory for product spaces, and in trying to construct a certain type of counterexample it's become relevant to consider the question in the title above. I am interested in finding a normal space $X$ whose products with itself is eventually non-normal, but not immediately.



It's not actually important for my application that it happens in three steps as opposed to more. An alternative question would be: Is there a normal space $X$ with $X times X = Y$ normal, but $Y times Y$ is not normal?



The original problem is here:



https://mathoverflow.net/questions/315657/if-textdimx-times-x-2-textdimx-does-textdimxn-n-textdim



Thanks for any help!



As mentioned in a comment below, if we assume that $X$ is a compact Hausdorff space and that $X times X times X$ is completely normal, then $X$ is metrizable. Thus it stands to reason that a compact counterexample may be harder (if not impossible) to construct. The author in the linked paper wonders aloud if the complete normality of $X times X$ is sufficient for the metrizability of $X$, so it may also be advisable to avoid cases where $X times X$ is completely normal.










share|cite|improve this question




















  • 1




    This is not an answer, but somehow related: math.stackexchange.com/q/2872102
    – Paul Frost
    Nov 21 at 8:57










  • Interesting result, I will mention it in an edit.
    – John Samples
    Nov 21 at 10:00













up vote
4
down vote

favorite
1









up vote
4
down vote

favorite
1






1





I am looking at some topological dimension theory for product spaces, and in trying to construct a certain type of counterexample it's become relevant to consider the question in the title above. I am interested in finding a normal space $X$ whose products with itself is eventually non-normal, but not immediately.



It's not actually important for my application that it happens in three steps as opposed to more. An alternative question would be: Is there a normal space $X$ with $X times X = Y$ normal, but $Y times Y$ is not normal?



The original problem is here:



https://mathoverflow.net/questions/315657/if-textdimx-times-x-2-textdimx-does-textdimxn-n-textdim



Thanks for any help!



As mentioned in a comment below, if we assume that $X$ is a compact Hausdorff space and that $X times X times X$ is completely normal, then $X$ is metrizable. Thus it stands to reason that a compact counterexample may be harder (if not impossible) to construct. The author in the linked paper wonders aloud if the complete normality of $X times X$ is sufficient for the metrizability of $X$, so it may also be advisable to avoid cases where $X times X$ is completely normal.










share|cite|improve this question















I am looking at some topological dimension theory for product spaces, and in trying to construct a certain type of counterexample it's become relevant to consider the question in the title above. I am interested in finding a normal space $X$ whose products with itself is eventually non-normal, but not immediately.



It's not actually important for my application that it happens in three steps as opposed to more. An alternative question would be: Is there a normal space $X$ with $X times X = Y$ normal, but $Y times Y$ is not normal?



The original problem is here:



https://mathoverflow.net/questions/315657/if-textdimx-times-x-2-textdimx-does-textdimxn-n-textdim



Thanks for any help!



As mentioned in a comment below, if we assume that $X$ is a compact Hausdorff space and that $X times X times X$ is completely normal, then $X$ is metrizable. Thus it stands to reason that a compact counterexample may be harder (if not impossible) to construct. The author in the linked paper wonders aloud if the complete normality of $X times X$ is sufficient for the metrizability of $X$, so it may also be advisable to avoid cases where $X times X$ is completely normal.







general-topology examples-counterexamples dimension-theory separation-axioms product-space






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 21 at 10:04

























asked Nov 21 at 5:36









John Samples

1,081516




1,081516








  • 1




    This is not an answer, but somehow related: math.stackexchange.com/q/2872102
    – Paul Frost
    Nov 21 at 8:57










  • Interesting result, I will mention it in an edit.
    – John Samples
    Nov 21 at 10:00














  • 1




    This is not an answer, but somehow related: math.stackexchange.com/q/2872102
    – Paul Frost
    Nov 21 at 8:57










  • Interesting result, I will mention it in an edit.
    – John Samples
    Nov 21 at 10:00








1




1




This is not an answer, but somehow related: math.stackexchange.com/q/2872102
– Paul Frost
Nov 21 at 8:57




This is not an answer, but somehow related: math.stackexchange.com/q/2872102
– Paul Frost
Nov 21 at 8:57












Interesting result, I will mention it in an edit.
– John Samples
Nov 21 at 10:00




Interesting result, I will mention it in an edit.
– John Samples
Nov 21 at 10:00










1 Answer
1






active

oldest

votes

















up vote
4
down vote



accepted










A construction can be found in (or weaned from)





  • Przymusinski, Teodor C., Normality and paracompactness in finite and countable Cartesian products, Fundam. Math. 105, 87-104 (1980). ZBL0438.54021.


wherein the following remarkable result is proved:




Theorem 1. For every $k$ and $m$ such that $1 leq k leq m leq omega$ there exists a separable and first coutnable space $X = X(k,m)$ such that





  1. $X^n$ is paracompact (Lindelöf, subparacompact) if and only if $n < k$,


  2. $X^n$ is normal (collectionwise normal) if and only if $n < m$.




In particular, we can construct a (normal) space such that the failure of normality of its powers happens first at any prescribed finite power.






share|cite|improve this answer





















  • Wow, what a result!
    – John Samples
    Nov 21 at 10:06











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














 

draft saved


draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3007308%2fif-x-times-x-is-normal-then-is-x-times-x-times-x-normal%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
4
down vote



accepted










A construction can be found in (or weaned from)





  • Przymusinski, Teodor C., Normality and paracompactness in finite and countable Cartesian products, Fundam. Math. 105, 87-104 (1980). ZBL0438.54021.


wherein the following remarkable result is proved:




Theorem 1. For every $k$ and $m$ such that $1 leq k leq m leq omega$ there exists a separable and first coutnable space $X = X(k,m)$ such that





  1. $X^n$ is paracompact (Lindelöf, subparacompact) if and only if $n < k$,


  2. $X^n$ is normal (collectionwise normal) if and only if $n < m$.




In particular, we can construct a (normal) space such that the failure of normality of its powers happens first at any prescribed finite power.






share|cite|improve this answer





















  • Wow, what a result!
    – John Samples
    Nov 21 at 10:06















up vote
4
down vote



accepted










A construction can be found in (or weaned from)





  • Przymusinski, Teodor C., Normality and paracompactness in finite and countable Cartesian products, Fundam. Math. 105, 87-104 (1980). ZBL0438.54021.


wherein the following remarkable result is proved:




Theorem 1. For every $k$ and $m$ such that $1 leq k leq m leq omega$ there exists a separable and first coutnable space $X = X(k,m)$ such that





  1. $X^n$ is paracompact (Lindelöf, subparacompact) if and only if $n < k$,


  2. $X^n$ is normal (collectionwise normal) if and only if $n < m$.




In particular, we can construct a (normal) space such that the failure of normality of its powers happens first at any prescribed finite power.






share|cite|improve this answer





















  • Wow, what a result!
    – John Samples
    Nov 21 at 10:06













up vote
4
down vote



accepted







up vote
4
down vote



accepted






A construction can be found in (or weaned from)





  • Przymusinski, Teodor C., Normality and paracompactness in finite and countable Cartesian products, Fundam. Math. 105, 87-104 (1980). ZBL0438.54021.


wherein the following remarkable result is proved:




Theorem 1. For every $k$ and $m$ such that $1 leq k leq m leq omega$ there exists a separable and first coutnable space $X = X(k,m)$ such that





  1. $X^n$ is paracompact (Lindelöf, subparacompact) if and only if $n < k$,


  2. $X^n$ is normal (collectionwise normal) if and only if $n < m$.




In particular, we can construct a (normal) space such that the failure of normality of its powers happens first at any prescribed finite power.






share|cite|improve this answer












A construction can be found in (or weaned from)





  • Przymusinski, Teodor C., Normality and paracompactness in finite and countable Cartesian products, Fundam. Math. 105, 87-104 (1980). ZBL0438.54021.


wherein the following remarkable result is proved:




Theorem 1. For every $k$ and $m$ such that $1 leq k leq m leq omega$ there exists a separable and first coutnable space $X = X(k,m)$ such that





  1. $X^n$ is paracompact (Lindelöf, subparacompact) if and only if $n < k$,


  2. $X^n$ is normal (collectionwise normal) if and only if $n < m$.




In particular, we can construct a (normal) space such that the failure of normality of its powers happens first at any prescribed finite power.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Nov 21 at 9:53









1-3-7-Trimethylxanthine

4,388927




4,388927












  • Wow, what a result!
    – John Samples
    Nov 21 at 10:06


















  • Wow, what a result!
    – John Samples
    Nov 21 at 10:06
















Wow, what a result!
– John Samples
Nov 21 at 10:06




Wow, what a result!
– John Samples
Nov 21 at 10:06


















 

draft saved


draft discarded



















































 


draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3007308%2fif-x-times-x-is-normal-then-is-x-times-x-times-x-normal%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Wiesbaden

Marschland

Dieringhausen