Comparisons of convenient categories for algebraic topology
up vote
11
down vote
favorite
I've heard that there are many convenient categories for algebraic topology. Such categories often have many nice properties like being cartesian closed, complete, cocomplete, the forgetful functor creates limits, containing all "nice" spaces like CW complexes and topological manifolds, et cetera. But the only convenient category for algebraic topologies that I know are the category of compact generated weakly Hausdorff (CGWH) spaces. Can someone briefly summarize other such categories and their advantages and disadvantages when compared to the category of CGWH spaces?
at.algebraic-topology ct.category-theory
add a comment |
up vote
11
down vote
favorite
I've heard that there are many convenient categories for algebraic topology. Such categories often have many nice properties like being cartesian closed, complete, cocomplete, the forgetful functor creates limits, containing all "nice" spaces like CW complexes and topological manifolds, et cetera. But the only convenient category for algebraic topologies that I know are the category of compact generated weakly Hausdorff (CGWH) spaces. Can someone briefly summarize other such categories and their advantages and disadvantages when compared to the category of CGWH spaces?
at.algebraic-topology ct.category-theory
add a comment |
up vote
11
down vote
favorite
up vote
11
down vote
favorite
I've heard that there are many convenient categories for algebraic topology. Such categories often have many nice properties like being cartesian closed, complete, cocomplete, the forgetful functor creates limits, containing all "nice" spaces like CW complexes and topological manifolds, et cetera. But the only convenient category for algebraic topologies that I know are the category of compact generated weakly Hausdorff (CGWH) spaces. Can someone briefly summarize other such categories and their advantages and disadvantages when compared to the category of CGWH spaces?
at.algebraic-topology ct.category-theory
I've heard that there are many convenient categories for algebraic topology. Such categories often have many nice properties like being cartesian closed, complete, cocomplete, the forgetful functor creates limits, containing all "nice" spaces like CW complexes and topological manifolds, et cetera. But the only convenient category for algebraic topologies that I know are the category of compact generated weakly Hausdorff (CGWH) spaces. Can someone briefly summarize other such categories and their advantages and disadvantages when compared to the category of CGWH spaces?
at.algebraic-topology ct.category-theory
at.algebraic-topology ct.category-theory
edited Dec 6 at 0:42
Goldstern
11.1k13260
11.1k13260
asked Dec 6 at 0:03
Rick Sternbach
3119
3119
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
up vote
14
down vote
From the nLab (although I was the author of these words):
A reasonably large class of examples, including the examples of compactly generated spaces and sequential spaces, is given in the article by Escardó, Lawson, and Simpson (ref). These may be outlined as follows. An exponentiable space in $Top$ is a space $X$ such that $X times -: Top to Top$ has a right adjoint. These may be described concretely as core-compact spaces (spaces whose topology is a [[continuous lattice]]). Suppose given a collection $mathcal{C}$ of core-compact spaces, with the property that the product of any two spaces in $mathcal{C}$ is a colimit in $Top$ of spaces in $mathcal{C}$. Such a collection $mathcal{C}$ is called productive. Spaces which are $Top$-colimits of spaces in $mathcal{C}$ are called $mathcal{C}$-generated.
Theorem (Escardó, Lawson, Simpson): If $mathcal{C}$ is a productive class, then the full subcategory of $Top$ whose objects are $mathcal{C}$-generated is a coreflective subcategory of $Top$ (hence complete and cocomplete) that is cartesian closed.
Other convenience conditions, such as inclusion of CW-complexes and closure under closed subspaces, are in practice usually satisfied as well. For example, if closed subspaces of objects of $mathcal{C}$ are $mathcal{C}$-generated, then closed subspaces of $mathcal{C}$-generated spaces are also $mathcal{C}$-generated. If the unit interval $I$ is $mathcal{C}$-generated, then so are all CW-complexes.
A number of examples are scattered throughout the paper.
2
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
add a comment |
up vote
7
down vote
If you want a convenient category of pointed spaces, then the category $mathbf{NG}_0$ of pointed numerically generated spaces, discussed for instance in
Kazuhisa Shimakawa, Kohei Yoshida, Tadayuki Haraguchi, Homology and cohomology via enriched bifunctors Kyushu Journal of Mathematics, 2018, Volume 72, Issue 2, Pages 239-252, doi:10.2206/kyushujm.72.239
is one. The authors say that numerically generated is equivalent to being $Delta$-generated, as discussed in Dan Dugger's Notes on Delta-generated spaces.
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
add a comment |
up vote
4
down vote
One property that one sometimes wants, but which is not satisfied by most of the "usual" convenient categories, is that of being locally cartesian closed, or equivalently that each pullback functor $f^* : mathcal{C}/Y to mathcal{C}/X$ has a right adjoint $f_*$.
However, I don't know of any nontrivial subcategory of the usual category $mathrm{Top}$ of topological spaces that is locally cartesian closed. The closest locally cartesian closed categories to $mathrm{Top}$ that I know of are quasitoposes, such as the category of subsequential spaces (which contains the category of sequential spaces mentioned by Todd, and is locally presentable) or pseudotopological spaces (which contains the entire category $mathrm{Top}$, but is not locally presentable).
Another approach, used by May and Sigurdsson, is to mix two convenient categories to approximate local cartesian closure. As explained in their book, if $mathcal{K}$ denotes the category of not-necessarily-weak-Hausdorff $k$-spaces, then the pullback functor $f^*:mathcal{K}/Yto mathcal{K}/X$ has a right adjoint as long as $X$ and $Y$ are weak Hausdorff.
add a comment |
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: "504"
};
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%2fmathoverflow.net%2fquestions%2f317004%2fcomparisons-of-convenient-categories-for-algebraic-topology%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
14
down vote
From the nLab (although I was the author of these words):
A reasonably large class of examples, including the examples of compactly generated spaces and sequential spaces, is given in the article by Escardó, Lawson, and Simpson (ref). These may be outlined as follows. An exponentiable space in $Top$ is a space $X$ such that $X times -: Top to Top$ has a right adjoint. These may be described concretely as core-compact spaces (spaces whose topology is a [[continuous lattice]]). Suppose given a collection $mathcal{C}$ of core-compact spaces, with the property that the product of any two spaces in $mathcal{C}$ is a colimit in $Top$ of spaces in $mathcal{C}$. Such a collection $mathcal{C}$ is called productive. Spaces which are $Top$-colimits of spaces in $mathcal{C}$ are called $mathcal{C}$-generated.
Theorem (Escardó, Lawson, Simpson): If $mathcal{C}$ is a productive class, then the full subcategory of $Top$ whose objects are $mathcal{C}$-generated is a coreflective subcategory of $Top$ (hence complete and cocomplete) that is cartesian closed.
Other convenience conditions, such as inclusion of CW-complexes and closure under closed subspaces, are in practice usually satisfied as well. For example, if closed subspaces of objects of $mathcal{C}$ are $mathcal{C}$-generated, then closed subspaces of $mathcal{C}$-generated spaces are also $mathcal{C}$-generated. If the unit interval $I$ is $mathcal{C}$-generated, then so are all CW-complexes.
A number of examples are scattered throughout the paper.
2
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
add a comment |
up vote
14
down vote
From the nLab (although I was the author of these words):
A reasonably large class of examples, including the examples of compactly generated spaces and sequential spaces, is given in the article by Escardó, Lawson, and Simpson (ref). These may be outlined as follows. An exponentiable space in $Top$ is a space $X$ such that $X times -: Top to Top$ has a right adjoint. These may be described concretely as core-compact spaces (spaces whose topology is a [[continuous lattice]]). Suppose given a collection $mathcal{C}$ of core-compact spaces, with the property that the product of any two spaces in $mathcal{C}$ is a colimit in $Top$ of spaces in $mathcal{C}$. Such a collection $mathcal{C}$ is called productive. Spaces which are $Top$-colimits of spaces in $mathcal{C}$ are called $mathcal{C}$-generated.
Theorem (Escardó, Lawson, Simpson): If $mathcal{C}$ is a productive class, then the full subcategory of $Top$ whose objects are $mathcal{C}$-generated is a coreflective subcategory of $Top$ (hence complete and cocomplete) that is cartesian closed.
Other convenience conditions, such as inclusion of CW-complexes and closure under closed subspaces, are in practice usually satisfied as well. For example, if closed subspaces of objects of $mathcal{C}$ are $mathcal{C}$-generated, then closed subspaces of $mathcal{C}$-generated spaces are also $mathcal{C}$-generated. If the unit interval $I$ is $mathcal{C}$-generated, then so are all CW-complexes.
A number of examples are scattered throughout the paper.
2
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
add a comment |
up vote
14
down vote
up vote
14
down vote
From the nLab (although I was the author of these words):
A reasonably large class of examples, including the examples of compactly generated spaces and sequential spaces, is given in the article by Escardó, Lawson, and Simpson (ref). These may be outlined as follows. An exponentiable space in $Top$ is a space $X$ such that $X times -: Top to Top$ has a right adjoint. These may be described concretely as core-compact spaces (spaces whose topology is a [[continuous lattice]]). Suppose given a collection $mathcal{C}$ of core-compact spaces, with the property that the product of any two spaces in $mathcal{C}$ is a colimit in $Top$ of spaces in $mathcal{C}$. Such a collection $mathcal{C}$ is called productive. Spaces which are $Top$-colimits of spaces in $mathcal{C}$ are called $mathcal{C}$-generated.
Theorem (Escardó, Lawson, Simpson): If $mathcal{C}$ is a productive class, then the full subcategory of $Top$ whose objects are $mathcal{C}$-generated is a coreflective subcategory of $Top$ (hence complete and cocomplete) that is cartesian closed.
Other convenience conditions, such as inclusion of CW-complexes and closure under closed subspaces, are in practice usually satisfied as well. For example, if closed subspaces of objects of $mathcal{C}$ are $mathcal{C}$-generated, then closed subspaces of $mathcal{C}$-generated spaces are also $mathcal{C}$-generated. If the unit interval $I$ is $mathcal{C}$-generated, then so are all CW-complexes.
A number of examples are scattered throughout the paper.
From the nLab (although I was the author of these words):
A reasonably large class of examples, including the examples of compactly generated spaces and sequential spaces, is given in the article by Escardó, Lawson, and Simpson (ref). These may be outlined as follows. An exponentiable space in $Top$ is a space $X$ such that $X times -: Top to Top$ has a right adjoint. These may be described concretely as core-compact spaces (spaces whose topology is a [[continuous lattice]]). Suppose given a collection $mathcal{C}$ of core-compact spaces, with the property that the product of any two spaces in $mathcal{C}$ is a colimit in $Top$ of spaces in $mathcal{C}$. Such a collection $mathcal{C}$ is called productive. Spaces which are $Top$-colimits of spaces in $mathcal{C}$ are called $mathcal{C}$-generated.
Theorem (Escardó, Lawson, Simpson): If $mathcal{C}$ is a productive class, then the full subcategory of $Top$ whose objects are $mathcal{C}$-generated is a coreflective subcategory of $Top$ (hence complete and cocomplete) that is cartesian closed.
Other convenience conditions, such as inclusion of CW-complexes and closure under closed subspaces, are in practice usually satisfied as well. For example, if closed subspaces of objects of $mathcal{C}$ are $mathcal{C}$-generated, then closed subspaces of $mathcal{C}$-generated spaces are also $mathcal{C}$-generated. If the unit interval $I$ is $mathcal{C}$-generated, then so are all CW-complexes.
A number of examples are scattered throughout the paper.
answered Dec 6 at 1:07
Todd Trimble♦
43.4k5156257
43.4k5156257
2
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
add a comment |
2
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
2
2
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
See also Booth, P.I. and Tillotson, J. Monoidal closed categories and convenient categories of topological spaces Pacific J. Math. {88} (1980) 33--53.
– Ronnie Brown
Dec 6 at 12:39
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
Freely-available pdf link for Booth–Tillotson: msp.org/pjm/1980/88-1/pjm-v88-n1-p03-s.pdf
– David Roberts
Dec 7 at 20:33
add a comment |
up vote
7
down vote
If you want a convenient category of pointed spaces, then the category $mathbf{NG}_0$ of pointed numerically generated spaces, discussed for instance in
Kazuhisa Shimakawa, Kohei Yoshida, Tadayuki Haraguchi, Homology and cohomology via enriched bifunctors Kyushu Journal of Mathematics, 2018, Volume 72, Issue 2, Pages 239-252, doi:10.2206/kyushujm.72.239
is one. The authors say that numerically generated is equivalent to being $Delta$-generated, as discussed in Dan Dugger's Notes on Delta-generated spaces.
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
add a comment |
up vote
7
down vote
If you want a convenient category of pointed spaces, then the category $mathbf{NG}_0$ of pointed numerically generated spaces, discussed for instance in
Kazuhisa Shimakawa, Kohei Yoshida, Tadayuki Haraguchi, Homology and cohomology via enriched bifunctors Kyushu Journal of Mathematics, 2018, Volume 72, Issue 2, Pages 239-252, doi:10.2206/kyushujm.72.239
is one. The authors say that numerically generated is equivalent to being $Delta$-generated, as discussed in Dan Dugger's Notes on Delta-generated spaces.
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
add a comment |
up vote
7
down vote
up vote
7
down vote
If you want a convenient category of pointed spaces, then the category $mathbf{NG}_0$ of pointed numerically generated spaces, discussed for instance in
Kazuhisa Shimakawa, Kohei Yoshida, Tadayuki Haraguchi, Homology and cohomology via enriched bifunctors Kyushu Journal of Mathematics, 2018, Volume 72, Issue 2, Pages 239-252, doi:10.2206/kyushujm.72.239
is one. The authors say that numerically generated is equivalent to being $Delta$-generated, as discussed in Dan Dugger's Notes on Delta-generated spaces.
If you want a convenient category of pointed spaces, then the category $mathbf{NG}_0$ of pointed numerically generated spaces, discussed for instance in
Kazuhisa Shimakawa, Kohei Yoshida, Tadayuki Haraguchi, Homology and cohomology via enriched bifunctors Kyushu Journal of Mathematics, 2018, Volume 72, Issue 2, Pages 239-252, doi:10.2206/kyushujm.72.239
is one. The authors say that numerically generated is equivalent to being $Delta$-generated, as discussed in Dan Dugger's Notes on Delta-generated spaces.
answered Dec 6 at 0:42
David Roberts
16.7k462174
16.7k462174
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
add a comment |
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
An important advantage of $Delta$-generated spaces -- shared with sequential spaces, or any full subcategory of $Top$ which is the colimit-closure of a small subcategory (a la Todd's response) is that they are locally presentable, which simplifies certain infinitary constructions like the small object argument.
– Tim Campion
Dec 7 at 18:15
add a comment |
up vote
4
down vote
One property that one sometimes wants, but which is not satisfied by most of the "usual" convenient categories, is that of being locally cartesian closed, or equivalently that each pullback functor $f^* : mathcal{C}/Y to mathcal{C}/X$ has a right adjoint $f_*$.
However, I don't know of any nontrivial subcategory of the usual category $mathrm{Top}$ of topological spaces that is locally cartesian closed. The closest locally cartesian closed categories to $mathrm{Top}$ that I know of are quasitoposes, such as the category of subsequential spaces (which contains the category of sequential spaces mentioned by Todd, and is locally presentable) or pseudotopological spaces (which contains the entire category $mathrm{Top}$, but is not locally presentable).
Another approach, used by May and Sigurdsson, is to mix two convenient categories to approximate local cartesian closure. As explained in their book, if $mathcal{K}$ denotes the category of not-necessarily-weak-Hausdorff $k$-spaces, then the pullback functor $f^*:mathcal{K}/Yto mathcal{K}/X$ has a right adjoint as long as $X$ and $Y$ are weak Hausdorff.
add a comment |
up vote
4
down vote
One property that one sometimes wants, but which is not satisfied by most of the "usual" convenient categories, is that of being locally cartesian closed, or equivalently that each pullback functor $f^* : mathcal{C}/Y to mathcal{C}/X$ has a right adjoint $f_*$.
However, I don't know of any nontrivial subcategory of the usual category $mathrm{Top}$ of topological spaces that is locally cartesian closed. The closest locally cartesian closed categories to $mathrm{Top}$ that I know of are quasitoposes, such as the category of subsequential spaces (which contains the category of sequential spaces mentioned by Todd, and is locally presentable) or pseudotopological spaces (which contains the entire category $mathrm{Top}$, but is not locally presentable).
Another approach, used by May and Sigurdsson, is to mix two convenient categories to approximate local cartesian closure. As explained in their book, if $mathcal{K}$ denotes the category of not-necessarily-weak-Hausdorff $k$-spaces, then the pullback functor $f^*:mathcal{K}/Yto mathcal{K}/X$ has a right adjoint as long as $X$ and $Y$ are weak Hausdorff.
add a comment |
up vote
4
down vote
up vote
4
down vote
One property that one sometimes wants, but which is not satisfied by most of the "usual" convenient categories, is that of being locally cartesian closed, or equivalently that each pullback functor $f^* : mathcal{C}/Y to mathcal{C}/X$ has a right adjoint $f_*$.
However, I don't know of any nontrivial subcategory of the usual category $mathrm{Top}$ of topological spaces that is locally cartesian closed. The closest locally cartesian closed categories to $mathrm{Top}$ that I know of are quasitoposes, such as the category of subsequential spaces (which contains the category of sequential spaces mentioned by Todd, and is locally presentable) or pseudotopological spaces (which contains the entire category $mathrm{Top}$, but is not locally presentable).
Another approach, used by May and Sigurdsson, is to mix two convenient categories to approximate local cartesian closure. As explained in their book, if $mathcal{K}$ denotes the category of not-necessarily-weak-Hausdorff $k$-spaces, then the pullback functor $f^*:mathcal{K}/Yto mathcal{K}/X$ has a right adjoint as long as $X$ and $Y$ are weak Hausdorff.
One property that one sometimes wants, but which is not satisfied by most of the "usual" convenient categories, is that of being locally cartesian closed, or equivalently that each pullback functor $f^* : mathcal{C}/Y to mathcal{C}/X$ has a right adjoint $f_*$.
However, I don't know of any nontrivial subcategory of the usual category $mathrm{Top}$ of topological spaces that is locally cartesian closed. The closest locally cartesian closed categories to $mathrm{Top}$ that I know of are quasitoposes, such as the category of subsequential spaces (which contains the category of sequential spaces mentioned by Todd, and is locally presentable) or pseudotopological spaces (which contains the entire category $mathrm{Top}$, but is not locally presentable).
Another approach, used by May and Sigurdsson, is to mix two convenient categories to approximate local cartesian closure. As explained in their book, if $mathcal{K}$ denotes the category of not-necessarily-weak-Hausdorff $k$-spaces, then the pullback functor $f^*:mathcal{K}/Yto mathcal{K}/X$ has a right adjoint as long as $X$ and $Y$ are weak Hausdorff.
answered Dec 6 at 17:12
Mike Shulman
35.7k480217
35.7k480217
add a comment |
add a comment |
Thanks for contributing an answer to MathOverflow!
- 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.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- 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.
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%2fmathoverflow.net%2fquestions%2f317004%2fcomparisons-of-convenient-categories-for-algebraic-topology%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