Which two of the following space are homeomorphic to each other?
$begingroup$
Which two of the following space are homeomorphic to each other?
begin{align}
X_1&={(x,y)in mathbb{R}^2:xy=0}\
X_2&={(x,y)in mathbb{R}^2:xy=1}\
X_3&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=0}\
X_4&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=1}
end{align}
I want to use the contentedness property.
Efforts:
$X_1$ and $X_4$ are not homeomorphic as $X_1$ is connected and nd $X_2$ is disconnected(two connected component)
By same logic $X_1$ and $X_4$ are not homeomorphic.
If I remove the origin from $X_1$, there are 4 components, but if we remove the origin from $X_3$, there are three connected component. So $X_1$ and $X_3$ are not homeomorphic.
Am I going in the right direction?
How to proceed after this.
general-topology continuity
$endgroup$
add a comment |
$begingroup$
Which two of the following space are homeomorphic to each other?
begin{align}
X_1&={(x,y)in mathbb{R}^2:xy=0}\
X_2&={(x,y)in mathbb{R}^2:xy=1}\
X_3&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=0}\
X_4&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=1}
end{align}
I want to use the contentedness property.
Efforts:
$X_1$ and $X_4$ are not homeomorphic as $X_1$ is connected and nd $X_2$ is disconnected(two connected component)
By same logic $X_1$ and $X_4$ are not homeomorphic.
If I remove the origin from $X_1$, there are 4 components, but if we remove the origin from $X_3$, there are three connected component. So $X_1$ and $X_3$ are not homeomorphic.
Am I going in the right direction?
How to proceed after this.
general-topology continuity
$endgroup$
1
$begingroup$
$X_4$ is connected.
$endgroup$
– Kavi Rama Murthy
Jan 15 at 9:14
$begingroup$
@KaviRamaMurthy By mistake I wrote "connected", I meant homoeomorphic. Sorry
$endgroup$
– StammeringMathematician
Jan 15 at 9:16
add a comment |
$begingroup$
Which two of the following space are homeomorphic to each other?
begin{align}
X_1&={(x,y)in mathbb{R}^2:xy=0}\
X_2&={(x,y)in mathbb{R}^2:xy=1}\
X_3&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=0}\
X_4&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=1}
end{align}
I want to use the contentedness property.
Efforts:
$X_1$ and $X_4$ are not homeomorphic as $X_1$ is connected and nd $X_2$ is disconnected(two connected component)
By same logic $X_1$ and $X_4$ are not homeomorphic.
If I remove the origin from $X_1$, there are 4 components, but if we remove the origin from $X_3$, there are three connected component. So $X_1$ and $X_3$ are not homeomorphic.
Am I going in the right direction?
How to proceed after this.
general-topology continuity
$endgroup$
Which two of the following space are homeomorphic to each other?
begin{align}
X_1&={(x,y)in mathbb{R}^2:xy=0}\
X_2&={(x,y)in mathbb{R}^2:xy=1}\
X_3&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=0}\
X_4&={(x,y)in mathbb{R}^2: x+ygeq 0 text{ and } xy=1}
end{align}
I want to use the contentedness property.
Efforts:
$X_1$ and $X_4$ are not homeomorphic as $X_1$ is connected and nd $X_2$ is disconnected(two connected component)
By same logic $X_1$ and $X_4$ are not homeomorphic.
If I remove the origin from $X_1$, there are 4 components, but if we remove the origin from $X_3$, there are three connected component. So $X_1$ and $X_3$ are not homeomorphic.
Am I going in the right direction?
How to proceed after this.
general-topology continuity
general-topology continuity
edited Jan 15 at 9:29
José Carlos Santos
177k24138248
177k24138248
asked Jan 15 at 9:10
StammeringMathematicianStammeringMathematician
2,8321324
2,8321324
1
$begingroup$
$X_4$ is connected.
$endgroup$
– Kavi Rama Murthy
Jan 15 at 9:14
$begingroup$
@KaviRamaMurthy By mistake I wrote "connected", I meant homoeomorphic. Sorry
$endgroup$
– StammeringMathematician
Jan 15 at 9:16
add a comment |
1
$begingroup$
$X_4$ is connected.
$endgroup$
– Kavi Rama Murthy
Jan 15 at 9:14
$begingroup$
@KaviRamaMurthy By mistake I wrote "connected", I meant homoeomorphic. Sorry
$endgroup$
– StammeringMathematician
Jan 15 at 9:16
1
1
$begingroup$
$X_4$ is connected.
$endgroup$
– Kavi Rama Murthy
Jan 15 at 9:14
$begingroup$
$X_4$ is connected.
$endgroup$
– Kavi Rama Murthy
Jan 15 at 9:14
$begingroup$
@KaviRamaMurthy By mistake I wrote "connected", I meant homoeomorphic. Sorry
$endgroup$
– StammeringMathematician
Jan 15 at 9:16
$begingroup$
@KaviRamaMurthy By mistake I wrote "connected", I meant homoeomorphic. Sorry
$endgroup$
– StammeringMathematician
Jan 15 at 9:16
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
Actually, $X_4$ is connected (it's a branch of a hyperbola) and therefore your argument fails. But if you remove $(0,0)$ from $X_1$, then what remains has four connected components. This proved that $X_1$ and $X_4$ are not homeomorphic.
On the other hand, $X_3$ and $X_4$ are homeomorphic. Just consider the map$$begin{array}{ccc}X_4&longrightarrow&X_3\(x,y)&mapsto&begin{cases}(0,y-x)&text{ if }ygeqslant x\(x-y,0)&text{ otherwise.}end{cases}end{array}$$
$endgroup$
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
add a comment |
$begingroup$
Yes you are right. In fact the only two homeomorphic sets are $X_3$ and $X_4$ since $X_4$ can be interpreted as a warped version of $X_3$. $X_3$, $X_4$ and $X_1$ are connected and $X_2$ is not. Therefore $X_2$ is not homeomorphic to any of the others. Also removing origin from $X_1$ leaves us with $4$ distinct parts in $X_1$ while leaving us $2$ distinct parts in $X_3$ and $X_4$. Therefore the only homeomorphic sets are $X_3$ and $X_4$.
$endgroup$
add a comment |
Your Answer
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',
autoActivateHeartbeat: false,
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
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3074228%2fwhich-two-of-the-following-space-are-homeomorphic-to-each-other%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Actually, $X_4$ is connected (it's a branch of a hyperbola) and therefore your argument fails. But if you remove $(0,0)$ from $X_1$, then what remains has four connected components. This proved that $X_1$ and $X_4$ are not homeomorphic.
On the other hand, $X_3$ and $X_4$ are homeomorphic. Just consider the map$$begin{array}{ccc}X_4&longrightarrow&X_3\(x,y)&mapsto&begin{cases}(0,y-x)&text{ if }ygeqslant x\(x-y,0)&text{ otherwise.}end{cases}end{array}$$
$endgroup$
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
add a comment |
$begingroup$
Actually, $X_4$ is connected (it's a branch of a hyperbola) and therefore your argument fails. But if you remove $(0,0)$ from $X_1$, then what remains has four connected components. This proved that $X_1$ and $X_4$ are not homeomorphic.
On the other hand, $X_3$ and $X_4$ are homeomorphic. Just consider the map$$begin{array}{ccc}X_4&longrightarrow&X_3\(x,y)&mapsto&begin{cases}(0,y-x)&text{ if }ygeqslant x\(x-y,0)&text{ otherwise.}end{cases}end{array}$$
$endgroup$
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
add a comment |
$begingroup$
Actually, $X_4$ is connected (it's a branch of a hyperbola) and therefore your argument fails. But if you remove $(0,0)$ from $X_1$, then what remains has four connected components. This proved that $X_1$ and $X_4$ are not homeomorphic.
On the other hand, $X_3$ and $X_4$ are homeomorphic. Just consider the map$$begin{array}{ccc}X_4&longrightarrow&X_3\(x,y)&mapsto&begin{cases}(0,y-x)&text{ if }ygeqslant x\(x-y,0)&text{ otherwise.}end{cases}end{array}$$
$endgroup$
Actually, $X_4$ is connected (it's a branch of a hyperbola) and therefore your argument fails. But if you remove $(0,0)$ from $X_1$, then what remains has four connected components. This proved that $X_1$ and $X_4$ are not homeomorphic.
On the other hand, $X_3$ and $X_4$ are homeomorphic. Just consider the map$$begin{array}{ccc}X_4&longrightarrow&X_3\(x,y)&mapsto&begin{cases}(0,y-x)&text{ if }ygeqslant x\(x-y,0)&text{ otherwise.}end{cases}end{array}$$
edited Jan 15 at 9:26
answered Jan 15 at 9:16
José Carlos SantosJosé Carlos Santos
177k24138248
177k24138248
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
add a comment |
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
By mistake I wrote "connected", I meant homoeomorphic. Sorry . I have edited the word in the post.
$endgroup$
– StammeringMathematician
Jan 15 at 9:17
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
I understood what you meant. What do you think about my answer?
$endgroup$
– José Carlos Santos
Jan 15 at 9:19
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
How $X_3$ and $X_4$ are homeomorphic. Can you give some hint. And in the OP, am I right in deducing that removing the origin from $X_3$ leaves us with three connected component. Thanks
$endgroup$
– StammeringMathematician
Jan 15 at 9:21
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
I've added the homeomorphism that I had in mind. And if you remove a point from $X_3$, that will leave you with two connected components.
$endgroup$
– José Carlos Santos
Jan 15 at 9:28
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
$begingroup$
Thanks for the quick reply.
$endgroup$
– StammeringMathematician
Jan 15 at 9:29
add a comment |
$begingroup$
Yes you are right. In fact the only two homeomorphic sets are $X_3$ and $X_4$ since $X_4$ can be interpreted as a warped version of $X_3$. $X_3$, $X_4$ and $X_1$ are connected and $X_2$ is not. Therefore $X_2$ is not homeomorphic to any of the others. Also removing origin from $X_1$ leaves us with $4$ distinct parts in $X_1$ while leaving us $2$ distinct parts in $X_3$ and $X_4$. Therefore the only homeomorphic sets are $X_3$ and $X_4$.
$endgroup$
add a comment |
$begingroup$
Yes you are right. In fact the only two homeomorphic sets are $X_3$ and $X_4$ since $X_4$ can be interpreted as a warped version of $X_3$. $X_3$, $X_4$ and $X_1$ are connected and $X_2$ is not. Therefore $X_2$ is not homeomorphic to any of the others. Also removing origin from $X_1$ leaves us with $4$ distinct parts in $X_1$ while leaving us $2$ distinct parts in $X_3$ and $X_4$. Therefore the only homeomorphic sets are $X_3$ and $X_4$.
$endgroup$
add a comment |
$begingroup$
Yes you are right. In fact the only two homeomorphic sets are $X_3$ and $X_4$ since $X_4$ can be interpreted as a warped version of $X_3$. $X_3$, $X_4$ and $X_1$ are connected and $X_2$ is not. Therefore $X_2$ is not homeomorphic to any of the others. Also removing origin from $X_1$ leaves us with $4$ distinct parts in $X_1$ while leaving us $2$ distinct parts in $X_3$ and $X_4$. Therefore the only homeomorphic sets are $X_3$ and $X_4$.
$endgroup$
Yes you are right. In fact the only two homeomorphic sets are $X_3$ and $X_4$ since $X_4$ can be interpreted as a warped version of $X_3$. $X_3$, $X_4$ and $X_1$ are connected and $X_2$ is not. Therefore $X_2$ is not homeomorphic to any of the others. Also removing origin from $X_1$ leaves us with $4$ distinct parts in $X_1$ while leaving us $2$ distinct parts in $X_3$ and $X_4$. Therefore the only homeomorphic sets are $X_3$ and $X_4$.
answered Jan 15 at 9:29
Mostafa AyazMostafa Ayaz
18.1k31040
18.1k31040
add a comment |
add a comment |
Thanks for contributing an answer to Mathematics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3074228%2fwhich-two-of-the-following-space-are-homeomorphic-to-each-other%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
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
1
$begingroup$
$X_4$ is connected.
$endgroup$
– Kavi Rama Murthy
Jan 15 at 9:14
$begingroup$
@KaviRamaMurthy By mistake I wrote "connected", I meant homoeomorphic. Sorry
$endgroup$
– StammeringMathematician
Jan 15 at 9:16