Comparisons of convenient categories for algebraic topology
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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
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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
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up vote
2
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favorite
up vote
2
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 2 hours ago
Goldstern
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asked 2 hours ago
Rick Sternbach
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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.
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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.
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2 Answers
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2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
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.
add a comment |
up vote
3
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.
add a comment |
up vote
3
down vote
up vote
3
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 1 hour ago
Todd Trimble♦
43.2k5156256
43.2k5156256
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up vote
2
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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.
add a comment |
up vote
2
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.
add a comment |
up vote
2
down vote
up vote
2
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 2 hours ago
David Roberts
16.5k462173
16.5k462173
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