cochains and homotopy theorymmandell/talks/fields100831.talk.pdf · overview cochains and homotopy...
TRANSCRIPT
![Page 1: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/1.jpg)
Cochains and Homotopy Theory
Michael A. Mandell
Indiana University
Fields Institute Conferenceon Homotopy Theory and Derived Algebraic Geometry
August 31, 2010
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 1 / 24
![Page 2: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/2.jpg)
Overview
Cochains and Homotopy Theory
AbstractIt is known that the E-infinity algebra structure on the cochain complexof a space contains all the homotopy theoretic information about thespace, but for partial information, less structure is needed. I willdiscuss some ideas and preliminary work in this direction.
Outline1 Distinguishing homotopy types2 Homotopy algebras and operadic algebras3 Formality in characteristic p4 Generalizing AHAH
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 2 / 24
![Page 3: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/3.jpg)
Overview
Cochains and Homotopy Theory
AbstractIt is known that the E-infinity algebra structure on the cochain complexof a space contains all the homotopy theoretic information about thespace, but for partial information, less structure is needed. I willdiscuss some ideas and preliminary work in this direction.
Outline1 Distinguishing homotopy types2 Homotopy algebras and operadic algebras3 Formality in characteristic p4 Generalizing AHAH
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 2 / 24
![Page 4: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/4.jpg)
Distinguishing Homotopy Types
Distinguishing Homotopy Types
Explanation through examples
Example (1st Semester Algebraic Topology)
Can distinguish CP2 and S4 though homology.
Example (2nd Semester Algebraic Topology)
Cannot distinguish CP2 and S2 ∨ S4 just through homology, but candistinguish them through their cohomology with cup product.
Example (3rd or 4th Semester Algebraic Topology)
Can classify homotopy types of all simply connected spaces withhomology like CP2 or S2 ∨ S4 their cohomology with cup product.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 3 / 24
![Page 5: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/5.jpg)
Distinguishing Homotopy Types
Distinguishing Homotopy Types
Explanation through examples
Example (1st Semester Algebraic Topology)
Can distinguish CP2 and S4 though homology.
Example (2nd Semester Algebraic Topology)
Cannot distinguish CP2 and S2 ∨ S4 just through homology, but candistinguish them through their cohomology with cup product.
Example (3rd or 4th Semester Algebraic Topology)
Can classify homotopy types of all simply connected spaces withhomology like CP2 or S2 ∨ S4 their cohomology with cup product.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 3 / 24
![Page 6: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/6.jpg)
Distinguishing Homotopy Types
Distinguishing Homotopy Types
Explanation through examples
Example (1st Semester Algebraic Topology)
Can distinguish CP2 and S4 though homology.
Example (2nd Semester Algebraic Topology)
Cannot distinguish CP2 and S2 ∨ S4 just through homology, but candistinguish them through their cohomology with cup product.
Example (3rd or 4th Semester Algebraic Topology)
Can classify homotopy types of all simply connected spaces withhomology like CP2 or S2 ∨ S4 their cohomology with cup product.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 3 / 24
![Page 7: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/7.jpg)
Distinguishing Homotopy Types
Distinguishing Homotopy Types
Explanation through examples
Example (1st Semester Algebraic Topology)
Can distinguish CP2 and S4 though homology.
Example (2nd Semester Algebraic Topology)
Cannot distinguish CP2 and S2 ∨ S4 just through homology, but candistinguish them through their cohomology with cup product.
Example (3rd or 4th Semester Algebraic Topology)
Can classify homotopy types of all simply connected spaces withhomology like CP2 or S2 ∨ S4 their cohomology with cup product.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 3 / 24
![Page 8: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/8.jpg)
Distinguishing Homotopy Types
Example (4th Semester Algebraic Topology)
Cannot distinguish ΣCP2 and S3 ∨ S5 through their cohomology justwith cup product, but can distinguish them using the Sq2
Steenrod operation
These are the only 2 homotopy types of simply connected spaces withthis homology.
Example (Advanced Graduate Algebraic Topology)
Homotopy types of spaces with homology like Sn ∨ Sn+r can bedistinguished and classified using higher cohomology operations“named” by the E2-term of the unstable Adams spectral sequence.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 4 / 24
![Page 9: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/9.jpg)
Distinguishing Homotopy Types
Example (4th Semester Algebraic Topology)
Cannot distinguish ΣCP2 and S3 ∨ S5 through their cohomology justwith cup product, but can distinguish them using the Sq2
Steenrod operation
These are the only 2 homotopy types of simply connected spaces withthis homology.
Example (Advanced Graduate Algebraic Topology)
Homotopy types of spaces with homology like Sn ∨ Sn+r can bedistinguished and classified using higher cohomology operations“named” by the E2-term of the unstable Adams spectral sequence.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 4 / 24
![Page 10: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/10.jpg)
Distinguishing Homotopy Types
Example (4th Semester Algebraic Topology)
Cannot distinguish ΣCP2 and S3 ∨ S5 through their cohomology justwith cup product, but can distinguish them using the Sq2
Steenrod operation
These are the only 2 homotopy types of simply connected spaces withthis homology.
Example (Advanced Graduate Algebraic Topology)
Homotopy types of spaces with homology like Sn ∨ Sn+r can bedistinguished and classified using higher cohomology operations“named” by the E2-term of the unstable Adams spectral sequence.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 4 / 24
![Page 11: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/11.jpg)
Distinguishing Homotopy Types
Cohomology and Homotopy Types
Question: Is there some kind of structure of higher operations thatdistinguishes all simply connected homotopy types?
Answer: Yes.
Question: Well, can you be more specific about the structure?Answer: Operations generalizing cup and cup-i products
McClure–Smith, “Multivariable Cochain Operations and Littlen-Cubes”, 2003
Fit together into the sequence operad S
Defines an E∞ algebra structure on C∗X
Simply connected homotopy types are distinguished by the E∞structure on the cochains.
Mandell, “Cochains and Homotopy Type”, 2006
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 5 / 24
![Page 12: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/12.jpg)
Distinguishing Homotopy Types
Cohomology and Homotopy Types
Question: Is there some kind of structure of higher operations thatdistinguishes all simply connected homotopy types?Answer: Yes.
Question: Well, can you be more specific about the structure?Answer: Operations generalizing cup and cup-i products
McClure–Smith, “Multivariable Cochain Operations and Littlen-Cubes”, 2003
Fit together into the sequence operad S
Defines an E∞ algebra structure on C∗X
Simply connected homotopy types are distinguished by the E∞structure on the cochains.
Mandell, “Cochains and Homotopy Type”, 2006
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 5 / 24
![Page 13: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/13.jpg)
Distinguishing Homotopy Types
Cohomology and Homotopy Types
Question: Is there some kind of structure of higher operations thatdistinguishes all simply connected homotopy types?Answer: Yes.
Question: Well, can you be more specific about the structure?
Answer: Operations generalizing cup and cup-i products
McClure–Smith, “Multivariable Cochain Operations and Littlen-Cubes”, 2003
Fit together into the sequence operad S
Defines an E∞ algebra structure on C∗X
Simply connected homotopy types are distinguished by the E∞structure on the cochains.
Mandell, “Cochains and Homotopy Type”, 2006
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 5 / 24
![Page 14: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/14.jpg)
Distinguishing Homotopy Types
Cohomology and Homotopy Types
Question: Is there some kind of structure of higher operations thatdistinguishes all simply connected homotopy types?Answer: Yes.
Question: Well, can you be more specific about the structure?Answer: Operations generalizing cup and cup-i products
McClure–Smith, “Multivariable Cochain Operations and Littlen-Cubes”, 2003
Fit together into the sequence operad S
Defines an E∞ algebra structure on C∗X
Simply connected homotopy types are distinguished by the E∞structure on the cochains.
Mandell, “Cochains and Homotopy Type”, 2006
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 5 / 24
![Page 15: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/15.jpg)
Distinguishing Homotopy Types
Cohomology and Homotopy Types
Question: Is there some kind of structure of higher operations thatdistinguishes all simply connected homotopy types?Answer: Yes.
Question: Well, can you be more specific about the structure?Answer: Operations generalizing cup and cup-i products
McClure–Smith, “Multivariable Cochain Operations and Littlen-Cubes”, 2003
Fit together into the sequence operad S
Defines an E∞ algebra structure on C∗X
Simply connected homotopy types are distinguished by the E∞structure on the cochains.
Mandell, “Cochains and Homotopy Type”, 2006
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 5 / 24
![Page 16: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/16.jpg)
Distinguishing Homotopy Types
Cohomology and Homotopy Types
Question: Is there some kind of structure of higher operations thatdistinguishes all simply connected homotopy types?Answer: Yes.
Question: Well, can you be more specific about the structure?Answer: Operations generalizing cup and cup-i products
McClure–Smith, “Multivariable Cochain Operations and Littlen-Cubes”, 2003
Fit together into the sequence operad S
Defines an E∞ algebra structure on C∗X
Simply connected homotopy types are distinguished by the E∞structure on the cochains.
Mandell, “Cochains and Homotopy Type”, 2006
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 5 / 24
![Page 17: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/17.jpg)
Distinguishing Homotopy Types
Older Work
Rational Homotopy Theory
Serre, 1950’sQuillen, 1969Sullivan, 1973-1977
p-adic Homotopy Theory
Adams, Mass. Inst. of Topology, 1958-1972Kriz, 1993Goerss, 1995Mandell, 2001
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 6 / 24
![Page 18: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/18.jpg)
Distinguishing Homotopy Types
Older Work
Rational Homotopy TheorySerre, 1950’s
Quillen, 1969Sullivan, 1973-1977
p-adic Homotopy TheoryAdams, Mass. Inst. of Topology, 1958-1972
Kriz, 1993Goerss, 1995Mandell, 2001
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 6 / 24
![Page 19: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/19.jpg)
Distinguishing Homotopy Types
Older Work
Rational Homotopy TheorySerre, 1950’sQuillen, 1969Sullivan, 1973-1977
p-adic Homotopy TheoryAdams, Mass. Inst. of Topology, 1958-1972
Kriz, 1993Goerss, 1995Mandell, 2001
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 6 / 24
![Page 20: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/20.jpg)
Distinguishing Homotopy Types
Older Work
Rational Homotopy TheorySerre, 1950’sQuillen, 1969Sullivan, 1973-1977
p-adic Homotopy TheoryAdams, Mass. Inst. of Topology, 1958-1972Kriz, 1993Goerss, 1995Mandell, 2001
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 6 / 24
![Page 21: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/21.jpg)
Distinguishing Homotopy Types
Practical Remarks
Rational Homotopy Theory
Objects: Rational commutative differential graded algebrasStandard form: Minimal modelMinimal model is easy to work withFor “formal” spaces, practical to find minimal model
p-Adic Homotopy Theory
Objects: E∞ algebrasStandard form: Cofibrant modelCofibrant model still very big, not always easy to work withFor spaces close to K (π,n)’s, practical to find cofibrant modelNo notion of “formal” space
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 7 / 24
![Page 22: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/22.jpg)
Distinguishing Homotopy Types
Practical Remarks
Rational Homotopy TheoryObjects: Rational commutative differential graded algebras
Standard form: Minimal modelMinimal model is easy to work withFor “formal” spaces, practical to find minimal model
p-Adic Homotopy TheoryObjects: E∞ algebras
Standard form: Cofibrant modelCofibrant model still very big, not always easy to work withFor spaces close to K (π,n)’s, practical to find cofibrant modelNo notion of “formal” space
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 7 / 24
![Page 23: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/23.jpg)
Distinguishing Homotopy Types
Practical Remarks
Rational Homotopy TheoryObjects: Rational commutative differential graded algebrasStandard form: Minimal model
Minimal model is easy to work withFor “formal” spaces, practical to find minimal model
p-Adic Homotopy TheoryObjects: E∞ algebrasStandard form: Cofibrant model
Cofibrant model still very big, not always easy to work withFor spaces close to K (π,n)’s, practical to find cofibrant modelNo notion of “formal” space
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 7 / 24
![Page 24: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/24.jpg)
Distinguishing Homotopy Types
Practical Remarks
Rational Homotopy TheoryObjects: Rational commutative differential graded algebrasStandard form: Minimal modelMinimal model is easy to work with
For “formal” spaces, practical to find minimal model
p-Adic Homotopy TheoryObjects: E∞ algebrasStandard form: Cofibrant modelCofibrant model still very big, not always easy to work with
For spaces close to K (π,n)’s, practical to find cofibrant modelNo notion of “formal” space
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 7 / 24
![Page 25: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/25.jpg)
Distinguishing Homotopy Types
Practical Remarks
Rational Homotopy TheoryObjects: Rational commutative differential graded algebrasStandard form: Minimal modelMinimal model is easy to work withFor “formal” spaces, practical to find minimal model
p-Adic Homotopy TheoryObjects: E∞ algebrasStandard form: Cofibrant modelCofibrant model still very big, not always easy to work with
For spaces close to K (π,n)’s, practical to find cofibrant modelNo notion of “formal” space
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 7 / 24
![Page 26: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/26.jpg)
Distinguishing Homotopy Types
Practical Remarks
Rational Homotopy TheoryObjects: Rational commutative differential graded algebrasStandard form: Minimal modelMinimal model is easy to work withFor “formal” spaces, practical to find minimal model
p-Adic Homotopy TheoryObjects: E∞ algebrasStandard form: Cofibrant modelCofibrant model still very big, not always easy to work withFor spaces close to K (π,n)’s, practical to find cofibrant modelNo notion of “formal” space
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 7 / 24
![Page 27: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/27.jpg)
Distinguishing Homotopy Types
Further Directions
Explanatory examples show that you do not need to keep track of thewhole E∞ structure to say interesting things about classification ofhomotopy types.
Approach: Constrain the spacesPut a constraint on the class of spaces and determine what algebrastructure classifies them. For example, limit connectivity, dimension,number and dimension of cells, etc.
Lots of work in this direction by Baues and collaborators
Approach: Weaken the algebraic structureLook at an algebraic structure weaker than E∞ and see whatinformation is left.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 8 / 24
![Page 28: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/28.jpg)
Distinguishing Homotopy Types
Further Directions
Explanatory examples show that you do not need to keep track of thewhole E∞ structure to say interesting things about classification ofhomotopy types.
Approach: Constrain the spacesPut a constraint on the class of spaces and determine what algebrastructure classifies them.
For example, limit connectivity, dimension,number and dimension of cells, etc.
Lots of work in this direction by Baues and collaborators
Approach: Weaken the algebraic structureLook at an algebraic structure weaker than E∞ and see whatinformation is left.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 8 / 24
![Page 29: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/29.jpg)
Distinguishing Homotopy Types
Further Directions
Explanatory examples show that you do not need to keep track of thewhole E∞ structure to say interesting things about classification ofhomotopy types.
Approach: Constrain the spacesPut a constraint on the class of spaces and determine what algebrastructure classifies them. For example, limit connectivity, dimension,number and dimension of cells, etc.
Lots of work in this direction by Baues and collaborators
Approach: Weaken the algebraic structureLook at an algebraic structure weaker than E∞ and see whatinformation is left.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 8 / 24
![Page 30: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/30.jpg)
Distinguishing Homotopy Types
Further Directions
Explanatory examples show that you do not need to keep track of thewhole E∞ structure to say interesting things about classification ofhomotopy types.
Approach: Constrain the spacesPut a constraint on the class of spaces and determine what algebrastructure classifies them. For example, limit connectivity, dimension,number and dimension of cells, etc.
Lots of work in this direction by Baues and collaborators
Approach: Weaken the algebraic structureLook at an algebraic structure weaker than E∞ and see whatinformation is left.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 8 / 24
![Page 31: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/31.jpg)
Distinguishing Homotopy Types
Further Directions
Explanatory examples show that you do not need to keep track of thewhole E∞ structure to say interesting things about classification ofhomotopy types.
Approach: Constrain the spacesPut a constraint on the class of spaces and determine what algebrastructure classifies them. For example, limit connectivity, dimension,number and dimension of cells, etc.
Lots of work in this direction by Baues and collaborators
Approach: Weaken the algebraic structureLook at an algebraic structure weaker than E∞ and see whatinformation is left.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 8 / 24
![Page 32: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/32.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod Operations
Look at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 33: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/33.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 34: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/34.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 35: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/35.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 36: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/36.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 37: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/37.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod Operations
McClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 38: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/38.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 39: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/39.jpg)
Homotopy Algebras and Operadic Algebras
Algebraic Structures
Example: Steenrod OperationsLook at H∗X as an unstable algebra over the Steenrod algebra.
This is equivalent to looking at C∗X as an H∞ algebra.
Can formulate this (±) in terms of the structure of an algebra over anoperad that maps into the McClure–Smith sequence operad.
We should look at operads mapping in to the sequence operad.
Example: Limited Steenrod OperationsMcClure–Smith show that sub-operad Sn coming from first (i.e., last)bunch of Steenrod operations is an En operad.
What information is left when we view C∗X as an En algebra?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 9 / 24
![Page 40: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/40.jpg)
Homotopy Algebras and Operadic Algebras
What is left in the En Structure?
The En−1 structure on a homotopy pullback
:Can compute En−1-structure on C∗(Y ×X Z ) asTorC∗X (C∗Y ,C∗Z ).
Cohomology of ΩmX for m ≤ n.
Cohomology of based mapping space X M+with domain M a
framed manifold of dimension m ≤ n.
Beilinson–Drinfeld / Lurie: “Chiral homology with coefficients inC∗X ”
An approach to formality in characteristic p.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 10 / 24
![Page 41: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/41.jpg)
Homotopy Algebras and Operadic Algebras
What is left in the En Structure?
The En−1 structure on a homotopy pullback:Can compute En−1-structure on C∗(Y ×X Z ) asTorC∗X (C∗Y ,C∗Z ).
Cohomology of ΩmX for m ≤ n.
Cohomology of based mapping space X M+with domain M a
framed manifold of dimension m ≤ n.
Beilinson–Drinfeld / Lurie: “Chiral homology with coefficients inC∗X ”
An approach to formality in characteristic p.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 10 / 24
![Page 42: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/42.jpg)
Homotopy Algebras and Operadic Algebras
What is left in the En Structure?
The En−1 structure on a homotopy pullback:Can compute En−1-structure on C∗(Y ×X Z ) asTorC∗X (C∗Y ,C∗Z ).
Cohomology of ΩmX for m ≤ n.
Cohomology of based mapping space X M+with domain M a
framed manifold of dimension m ≤ n.
Beilinson–Drinfeld / Lurie: “Chiral homology with coefficients inC∗X ”
An approach to formality in characteristic p.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 10 / 24
![Page 43: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/43.jpg)
Homotopy Algebras and Operadic Algebras
What is left in the En Structure?
The En−1 structure on a homotopy pullback:Can compute En−1-structure on C∗(Y ×X Z ) asTorC∗X (C∗Y ,C∗Z ).
Cohomology of ΩmX for m ≤ n.
Cohomology of based mapping space X M+with domain M a
framed manifold of dimension m ≤ n.
Beilinson–Drinfeld / Lurie: “Chiral homology with coefficients inC∗X ”
An approach to formality in characteristic p.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 10 / 24
![Page 44: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/44.jpg)
Homotopy Algebras and Operadic Algebras
What is left in the En Structure?
The En−1 structure on a homotopy pullback:Can compute En−1-structure on C∗(Y ×X Z ) asTorC∗X (C∗Y ,C∗Z ).
Cohomology of ΩmX for m ≤ n.
Cohomology of based mapping space X M+with domain M a
framed manifold of dimension m ≤ n.
Beilinson–Drinfeld / Lurie: “Chiral homology with coefficients inC∗X ”
An approach to formality in characteristic p.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 10 / 24
![Page 45: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/45.jpg)
Formality in Characteristic p
Formality in Characteristic Zero
DefinitionA commutative differential graded Q-algebra is formal if it isquasi-isomorphic to its cohomology though maps of commutativedifferential graded algebras.
ExamplesA Q-CDGA with zero differential is formalA Q-CDGA whose cohomology is a free gr. com. algebra is formalA Q-CDGA whose cohomology is an exterior algebra is formal
DefinitionA space is rationally formal if its polynomial De Rham complex is aformal Q-CDGA.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 11 / 24
![Page 46: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/46.jpg)
Formality in Characteristic p
Formality in Characteristic Zero
DefinitionA commutative differential graded Q-algebra is formal if it isquasi-isomorphic to its cohomology though maps of commutativedifferential graded algebras.
ExamplesA Q-CDGA with zero differential is formalA Q-CDGA whose cohomology is a free gr. com. algebra is formalA Q-CDGA whose cohomology is an exterior algebra is formal
DefinitionA space is rationally formal if its polynomial De Rham complex is aformal Q-CDGA.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 11 / 24
![Page 47: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/47.jpg)
Formality in Characteristic p
Formality in Characteristic Zero
DefinitionA commutative differential graded Q-algebra is formal if it isquasi-isomorphic to its cohomology though maps of commutativedifferential graded algebras.
ExamplesA Q-CDGA with zero differential is formalA Q-CDGA whose cohomology is a free gr. com. algebra is formalA Q-CDGA whose cohomology is an exterior algebra is formal
DefinitionA space is rationally formal if its polynomial De Rham complex is aformal Q-CDGA.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 11 / 24
![Page 48: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/48.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 49: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/49.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 50: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/50.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 51: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/51.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 52: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/52.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 53: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/53.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 54: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/54.jpg)
Formality in Characteristic p
Examples of Rationally Formal Spaces
Spheres
Cohomology is an exterior algebra.
Lie Groups / H-Spaces
Milnor-Moore: Cohomology is a free gr. comm. algebra.
Wedges and Products of Formal Spaces
Complex Algebraic Varieties
Deligne-Griffiths-Morgan-Sullivan / Morgan
Mixed Hodge structure on cohomology gives a mixed Hodgestructure on the De Rham complex. Limits possibilities fordifferentials.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 12 / 24
![Page 55: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/55.jpg)
Formality in Characteristic p
Formality for E∞ Algebras
DefinitionAn E∞ algebra is formal if it is quasi-isomorphic to its cohomologythough maps of E∞ algebras.
Cohomology of an E∞ algebra has E∞ algebra from its gradedcommutative algebra structure.
In characteristic p, cohomology of E∞ algebras have Steenrod /Dyer-Lashof operations. For commutative algebras, all but the p-thpower operation are zero.
For spaces, the zeroth operation is the identity.
The cochain algebra of a space cannot be formal unless thespace has contractible components.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 13 / 24
![Page 56: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/56.jpg)
Formality in Characteristic p
Formality for E∞ Algebras
DefinitionAn E∞ algebra is formal if it is quasi-isomorphic to its cohomologythough maps of E∞ algebras.
Cohomology of an E∞ algebra has E∞ algebra from its gradedcommutative algebra structure.
In characteristic p, cohomology of E∞ algebras have Steenrod /Dyer-Lashof operations. For commutative algebras, all but the p-thpower operation are zero.
For spaces, the zeroth operation is the identity.
The cochain algebra of a space cannot be formal unless thespace has contractible components.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 13 / 24
![Page 57: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/57.jpg)
Formality in Characteristic p
Formality for E∞ Algebras
DefinitionAn E∞ algebra is formal if it is quasi-isomorphic to its cohomologythough maps of E∞ algebras.
Cohomology of an E∞ algebra has E∞ algebra from its gradedcommutative algebra structure.
In characteristic p, cohomology of E∞ algebras have Steenrod /Dyer-Lashof operations. For commutative algebras, all but the p-thpower operation are zero.
For spaces, the zeroth operation is the identity.
The cochain algebra of a space cannot be formal unless thespace has contractible components.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 13 / 24
![Page 58: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/58.jpg)
Formality in Characteristic p
Formality for E∞ Algebras
DefinitionAn E∞ algebra is formal if it is quasi-isomorphic to its cohomologythough maps of E∞ algebras.
Cohomology of an E∞ algebra has E∞ algebra from its gradedcommutative algebra structure.
In characteristic p, cohomology of E∞ algebras have Steenrod /Dyer-Lashof operations. For commutative algebras, all but the p-thpower operation are zero.
For spaces, the zeroth operation is the identity.
The cochain algebra of a space cannot be formal unless thespace has contractible components.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 13 / 24
![Page 59: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/59.jpg)
Formality in Characteristic p
En Algebras
En algebras have operations on x ∈ H∗A
Sqmx ,Sqm−1x , . . . ,Sqm−n+1x p = 2, |x | = m
Pmx ,Pm−1x , . . . ,Pm−b(n−1)/2cx p > 2, |x | = 2m
Pmx ,Pm−1x , . . . ,Pm−bn/2cx p > 2, |x | = 2m + 1,n > 1
For |x | ≥ n, Sq0/P0 not an En algebra operation on x .
If X is an (n − 1)-connected space, no Sq0/P0 operation in Enstructure on cochains
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 14 / 24
![Page 60: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/60.jpg)
Formality in Characteristic p
En Algebras
En algebras have operations on x ∈ H∗A
Sqmx ,Sqm−1x , . . . ,Sqm−n+1x p = 2, |x | = m
Pmx ,Pm−1x , . . . ,Pm−b(n−1)/2cx p > 2, |x | = 2m
Pmx ,Pm−1x , . . . ,Pm−bn/2cx p > 2, |x | = 2m + 1,n > 1
For |x | ≥ n, Sq0/P0 not an En algebra operation on x .
If X is an (n − 1)-connected space, no Sq0/P0 operation in Enstructure on cochains
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 14 / 24
![Page 61: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/61.jpg)
Formality in Characteristic p
En Algebras
En algebras have operations on x ∈ H∗A
Sqmx ,Sqm−1x , . . . ,Sqm−n+1x p = 2, |x | = m
Pmx ,Pm−1x , . . . ,Pm−b(n−1)/2cx p > 2, |x | = 2m
Pmx ,Pm−1x , . . . ,Pm−bn/2cx p > 2, |x | = 2m + 1,n > 1
For |x | ≥ n, Sq0/P0 not an En algebra operation on x .
If X is an (n − 1)-connected space, no Sq0/P0 operation in Enstructure on cochains
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 14 / 24
![Page 62: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/62.jpg)
Formality in Characteristic p
En Algebras
En algebras have operations on x ∈ H∗A
Sqmx ,Sqm−1x , . . . ,Sqm−n+1x p = 2, |x | = m
Pmx ,Pm−1x , . . . ,Pm−b(n−1)/2cx p > 2, |x | = 2m
Pmx ,Pm−1x , . . . ,Pm−bn/2cx p > 2, |x | = 2m + 1,n > 1
For |x | ≥ n, Sq0/P0 not an En algebra operation on x .
If X is an (n − 1)-connected space, no Sq0/P0 operation in Enstructure on cochains
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 14 / 24
![Page 63: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/63.jpg)
Formality in Characteristic p
Formal En Algebras
DefinitionAn En algebra is formal if it is quasi-isomorphic to its gradedcohomology ring though maps of En algebras.
Cohomology of En algebras have (−n + 1)-Poisson structure, but Enstructure bracket is trivial for En+1 algebras.
Which (n − 1)-connected spaces are En formal?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 15 / 24
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Formality in Characteristic p
Formal En Algebras
DefinitionAn En algebra is formal if it is quasi-isomorphic to its gradedcohomology ring though maps of En algebras.
Cohomology of En algebras have (−n + 1)-Poisson structure, but Enstructure bracket is trivial for En+1 algebras.
Which (n − 1)-connected spaces are En formal?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 15 / 24
![Page 65: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/65.jpg)
Formality in Characteristic p
Formal En Algebras
DefinitionAn En algebra is formal if it is quasi-isomorphic to its gradedcohomology ring though maps of En algebras.
Cohomology of En algebras have (−n + 1)-Poisson structure, but Enstructure bracket is trivial for En+1 algebras.
Which (n − 1)-connected spaces are En formal?
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 15 / 24
![Page 66: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/66.jpg)
Formality in Characteristic p
Loops and Suspension
Recall: For any space X , Ωn is an En space.
If X is an En−1-space, ΩX is an En space.
Because C∗ is contravariant, C∗ΣX is “like” loops of C∗X .(Think HZΣX ∼= ΩHZX )
TheoremThe En−1 structure on C∗X determines the En structure on C∗ΣX.
Consequence
For any X , ΣnX is En formal.Sn is En-formal but not En+1 formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 16 / 24
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Formality in Characteristic p
Loops and Suspension
Recall: For any space X , Ωn is an En space.
If X is an En−1-space, ΩX is an En space.
Because C∗ is contravariant, C∗ΣX is “like” loops of C∗X .(Think HZΣX ∼= ΩHZX )
TheoremThe En−1 structure on C∗X determines the En structure on C∗ΣX.
Consequence
For any X , ΣnX is En formal.Sn is En-formal but not En+1 formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 16 / 24
![Page 68: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/68.jpg)
Formality in Characteristic p
Loops and Suspension
Recall: For any space X , Ωn is an En space.
If X is an En−1-space, ΩX is an En space.
Because C∗ is contravariant, C∗ΣX is “like” loops of C∗X .(Think HZΣX ∼= ΩHZX )
TheoremThe En−1 structure on C∗X determines the En structure on C∗ΣX.
Consequence
For any X , ΣnX is En formal.Sn is En-formal but not En+1 formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 16 / 24
![Page 69: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/69.jpg)
Formality in Characteristic p
Loops and Suspension
Recall: For any space X , Ωn is an En space.
If X is an En−1-space, ΩX is an En space.
Because C∗ is contravariant, C∗ΣX is “like” loops of C∗X .(Think HZΣX ∼= ΩHZX )
TheoremThe En−1 structure on C∗X determines the En structure on C∗ΣX.
Consequence
For any X , ΣnX is En formal.Sn is En-formal but not En+1 formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 16 / 24
![Page 70: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/70.jpg)
Formality in Characteristic p
Loops and Suspension
Recall: For any space X , Ωn is an En space.
If X is an En−1-space, ΩX is an En space.
Because C∗ is contravariant, C∗ΣX is “like” loops of C∗X .(Think HZΣX ∼= ΩHZX )
TheoremThe En−1 structure on C∗X determines the En structure on C∗ΣX.
Consequence
For any X , ΣnX is En formal.Sn is En-formal but not En+1 formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 16 / 24
![Page 71: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/71.jpg)
Formality in Characteristic p
Toward Formality
Let X be an n-connected space X of the homotopy type of a finite CWcomplex.
ConjectureAfter inverting finitely many primes, C∗X is quasi-isomorphic as an Enalgebra to a commutative differential graded algebra.
Conjecture (Formality)If X is rationally formal, then after inverting finitely many primes, C∗Xis En formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 17 / 24
![Page 72: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/72.jpg)
Formality in Characteristic p
Toward Formality
Let X be an n-connected space X of the homotopy type of a finite CWcomplex.
ConjectureAfter inverting finitely many primes, C∗X is quasi-isomorphic as an Enalgebra to a commutative differential graded algebra.
Conjecture (Formality)If X is rationally formal, then after inverting finitely many primes, C∗Xis En formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 17 / 24
![Page 73: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/73.jpg)
Formality in Characteristic p
Toward Formality
Let X be an n-connected space X of the homotopy type of a finite CWcomplex.
ConjectureAfter inverting finitely many primes, C∗X is quasi-isomorphic as an Enalgebra to a commutative differential graded algebra.
Conjecture (Formality)If X is rationally formal, then after inverting finitely many primes, C∗Xis En formal.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 17 / 24
![Page 74: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/74.jpg)
Generalizing AHAH
Relationship to AHAH
Anick, “Hopf Algebras up to Homotopy”, 1989
Theorem (Anick)
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional CW complex. Then the Adams-Hilton model of X withcoefficients in R is the universal enveloping algebra of a Lie algebra.
Koszul dual translation (?)
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For a 2-connected space, after inverting finitely many primes, C∗(X ) isquasi-isomorphic as an E2-algebra to a commutative differentialgraded algebra.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 18 / 24
![Page 75: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/75.jpg)
Generalizing AHAH
Relationship to AHAH
Anick, “Hopf Algebras up to Homotopy”, 1989
Theorem (Anick)
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional CW complex. Then the Adams-Hilton model of X withcoefficients in R is the universal enveloping algebra of a Lie algebra.
Koszul dual translation (?)
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For a 2-connected space, after inverting finitely many primes, C∗(X ) isquasi-isomorphic as an E2-algebra to a commutative differentialgraded algebra.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 18 / 24
![Page 76: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/76.jpg)
Generalizing AHAH
Relationship to AHAH
Anick, “Hopf Algebras up to Homotopy”, 1989
Theorem (Anick)
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional CW complex. Then the Adams-Hilton model of X withcoefficients in R is the universal enveloping algebra of a Lie algebra.
Koszul dual translation (?)
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For a 2-connected space, after inverting finitely many primes, C∗(X ) isquasi-isomorphic as an E2-algebra to a commutative differentialgraded algebra.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 18 / 24
![Page 77: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/77.jpg)
Generalizing AHAH
Relationship to AHAH
Anick, “Hopf Algebras up to Homotopy”, 1989
Theorem (Anick)
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional CW complex. Then the Adams-Hilton model of X withcoefficients in R is the universal enveloping algebra of a Lie algebra.
Koszul dual translation (?)
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For a 2-connected space, after inverting finitely many primes, C∗(X ) isquasi-isomorphic as an E2-algebra to a commutative differentialgraded algebra.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 18 / 24
![Page 78: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/78.jpg)
Generalizing AHAH
Relationship to AHAH
Anick, “Hopf Algebras up to Homotopy”, 1989
Theorem (Anick)
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional CW complex. Then the Adams-Hilton model of X withcoefficients in R is the universal enveloping algebra of a Lie algebra.
Koszul dual translation (?)
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For a 2-connected space, after inverting finitely many primes, C∗(X ) isquasi-isomorphic as an E2-algebra to a commutative differentialgraded algebra.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 18 / 24
![Page 79: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/79.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For an r -reduced simplicial set, p-th tensor power of any reducedcochain is in dimension ≥ p(r + 1).
Instead of looking at operad Com, we can look at a truncatedcommutative algebras: Use Com′ with Com′(k) = 0 for k ≥ p.
For k < p, Com′(k) is Σk -projective.
Can do homotopy theory with Com′ algebras.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 19 / 24
![Page 80: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/80.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For an r -reduced simplicial set, p-th tensor power of any reducedcochain is in dimension ≥ p(r + 1).
Instead of looking at operad Com, we can look at a truncatedcommutative algebras: Use Com′ with Com′(k) = 0 for k ≥ p.
For k < p, Com′(k) is Σk -projective.
Can do homotopy theory with Com′ algebras.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 19 / 24
![Page 81: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/81.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For an r -reduced simplicial set, p-th tensor power of any reducedcochain is in dimension ≥ p(r + 1).
Instead of looking at operad Com, we can look at a truncatedcommutative algebras: Use Com′ with Com′(k) = 0 for k ≥ p.
For k < p, Com′(k) is Σk -projective.
Can do homotopy theory with Com′ algebras.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 19 / 24
![Page 82: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/82.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For an r -reduced simplicial set, p-th tensor power of any reducedcochain is in dimension ≥ p(r + 1).
Instead of looking at operad Com, we can look at a truncatedcommutative algebras: Use Com′ with Com′(k) = 0 for k ≥ p.
For k < p, Com′(k) is Σk -projective.
Can do homotopy theory with Com′ algebras.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 19 / 24
![Page 83: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/83.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
For an r -reduced simplicial set, p-th tensor power of any reducedcochain is in dimension ≥ p(r + 1).
Instead of looking at operad Com, we can look at a truncatedcommutative algebras: Use Com′ with Com′(k) = 0 for k ≥ p.
For k < p, Com′(k) is Σk -projective.
Can do homotopy theory with Com′ algebras.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 19 / 24
![Page 84: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/84.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
The McClure–Smith sequence E2 operad S2 has
dimS2(k) = k − 1
So if X is r -reduced, the operations on reduced cochains
S2(k)⊗ (C∗X )⊗k → C∗X
land in degrees k(r + 1)− (k − 1) = kr + 1 and above.
Under Anick’s hypothesis, C∗X is an algebra over the truncated operadS ′2 with S ′2(k) = 0 for k ≥ p.
We can look at obstruction theory for the S ′2-structure to extend to aCom′-structure.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 20 / 24
![Page 85: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/85.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
The McClure–Smith sequence E2 operad S2 has
dimS2(k) = k − 1
So if X is r -reduced, the operations on reduced cochains
S2(k)⊗ (C∗X )⊗k → C∗X
land in degrees k(r + 1)− (k − 1) = kr + 1 and above.
Under Anick’s hypothesis, C∗X is an algebra over the truncated operadS ′2 with S ′2(k) = 0 for k ≥ p.
We can look at obstruction theory for the S ′2-structure to extend to aCom′-structure.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 20 / 24
![Page 86: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/86.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
The McClure–Smith sequence E2 operad S2 has
dimS2(k) = k − 1
So if X is r -reduced, the operations on reduced cochains
S2(k)⊗ (C∗X )⊗k → C∗X
land in degrees k(r + 1)− (k − 1) = kr + 1 and above.
Under Anick’s hypothesis, C∗X is an algebra over the truncated operadS ′2 with S ′2(k) = 0 for k ≥ p.
We can look at obstruction theory for the S ′2-structure to extend to aCom′-structure.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 20 / 24
![Page 87: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/87.jpg)
Generalizing AHAH
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedpr-dimensional simplicial complex. Then C∗(X ; R) is quasi-isomorphicas an E2-algebra to a commutative differential graded algebra.
The McClure–Smith sequence E2 operad S2 has
dimS2(k) = k − 1
So if X is r -reduced, the operations on reduced cochains
S2(k)⊗ (C∗X )⊗k → C∗X
land in degrees k(r + 1)− (k − 1) = kr + 1 and above.
Under Anick’s hypothesis, C∗X is an algebra over the truncated operadS ′2 with S ′2(k) = 0 for k ≥ p.
We can look at obstruction theory for the S ′2-structure to extend to aCom′-structure.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 20 / 24
![Page 88: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/88.jpg)
Generalizing AHAH
The Linearity Hypothesis
Hypothesis. There exists and En operad E that acts on cochaincomplexes and satisfies the dimension bound
dim E(k) = (k − 1)(n − 1).
Highest chain-level k -ary operation occurs in degree (k − 1)(n − 1).
Notes.This is the same degree as highest non-zero homology group.The standard En operads satisfy this bound for k = 2.Standard E1 and E2 operads satisfy this bound for all n, k .Standard configuration space models satisfy this bound for all n, k(but don’t fit together into operads).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 21 / 24
![Page 89: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/89.jpg)
Generalizing AHAH
The Linearity Hypothesis
Hypothesis. There exists and En operad E that acts on cochaincomplexes and satisfies the dimension bound
dim E(k) = (k − 1)(n − 1).
Highest chain-level k -ary operation occurs in degree (k − 1)(n − 1).
Notes.This is the same degree as highest non-zero homology group.The standard En operads satisfy this bound for k = 2.Standard E1 and E2 operads satisfy this bound for all n, k .Standard configuration space models satisfy this bound for all n, k(but don’t fit together into operads).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 21 / 24
![Page 90: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/90.jpg)
Generalizing AHAH
A Weaker Linearity Hypothesis
At the cost of weakening the conjectures, the hypothesis can beweakened to a linearity hypothesis
dim E(k) = a(k − 1)(n − 1) for k 0
The little n-cubes operad of spaces has k -th space a non-compactmanifold with boundary, dimension k(n + 1).
Hypothesis can be weakened further: Operad does not have to be zeroin high dimensions, just act by zero on simplices of a given dimension.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 22 / 24
![Page 91: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/91.jpg)
Generalizing AHAH
A Weaker Linearity Hypothesis
At the cost of weakening the conjectures, the hypothesis can beweakened to a linearity hypothesis
dim E(k) = a(k − 1)(n − 1) for k 0
The little n-cubes operad of spaces has k -th space a non-compactmanifold with boundary, dimension k(n + 1).
Hypothesis can be weakened further: Operad does not have to be zeroin high dimensions, just act by zero on simplices of a given dimension.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 22 / 24
![Page 92: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/92.jpg)
Generalizing AHAH
A Weaker Linearity Hypothesis
At the cost of weakening the conjectures, the hypothesis can beweakened to a linearity hypothesis
dim E(k) = a(k − 1)(n − 1) for k 0
The little n-cubes operad of spaces has k -th space a non-compactmanifold with boundary, dimension k(n + 1).
Hypothesis can be weakened further: Operad does not have to be zeroin high dimensions, just act by zero on simplices of a given dimension.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 22 / 24
![Page 93: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/93.jpg)
Generalizing AHAH
Consequences of the Linearity Hypothesis
Let X be r -reduced dimension d , so C∗X = 0 for ∗ ≤ r and ∗ > d
Look at En action.E(k)⊗ (C∗X )⊗k → C∗X .
Left side is non-zero in range k(r + 1)− (k − 1)(n − 1) to kd .Right side is non-zero in range r + 1 to d .
k(r +1)−(k−1)(n−1) = k(r +1−(n−1))+(n−1) = k(r−n+2)+n−1
So if k(r − n + 2) + n − 1 > d the map must be zero.
Limit dimension to p(r − n + 2)− n − 2 or even p(r − n + 2).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 23 / 24
![Page 94: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/94.jpg)
Generalizing AHAH
Consequences of the Linearity Hypothesis
Let X be r -reduced dimension d , so C∗X = 0 for ∗ ≤ r and ∗ > d
Look at En action.E(k)⊗ (C∗X )⊗k → C∗X .
Left side is non-zero in range k(r + 1)− (k − 1)(n − 1) to kd .Right side is non-zero in range r + 1 to d .
k(r +1)−(k−1)(n−1) = k(r +1−(n−1))+(n−1) = k(r−n+2)+n−1
So if k(r − n + 2) + n − 1 > d the map must be zero.
Limit dimension to p(r − n + 2)− n − 2 or even p(r − n + 2).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 23 / 24
![Page 95: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/95.jpg)
Generalizing AHAH
Consequences of the Linearity Hypothesis
Let X be r -reduced dimension d , so C∗X = 0 for ∗ ≤ r and ∗ > d
Look at En action.E(k)⊗ (C∗X )⊗k → C∗X .
Left side is non-zero in range k(r + 1)− (k − 1)(n − 1) to kd .Right side is non-zero in range r + 1 to d .
k(r +1)−(k−1)(n−1) = k(r +1−(n−1))+(n−1) = k(r−n+2)+n−1
So if k(r − n + 2) + n − 1 > d the map must be zero.
Limit dimension to p(r − n + 2)− n − 2 or even p(r − n + 2).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 23 / 24
![Page 96: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/96.jpg)
Generalizing AHAH
Consequences of the Linearity Hypothesis
Let X be r -reduced dimension d , so C∗X = 0 for ∗ ≤ r and ∗ > d
Look at En action.E(k)⊗ (C∗X )⊗k → C∗X .
Left side is non-zero in range k(r + 1)− (k − 1)(n − 1) to kd .Right side is non-zero in range r + 1 to d .
k(r +1)−(k−1)(n−1) = k(r +1−(n−1))+(n−1) = k(r−n+2)+n−1
So if k(r − n + 2) + n − 1 > d the map must be zero.
Limit dimension to p(r − n + 2)− n − 2 or even p(r − n + 2).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 23 / 24
![Page 97: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/97.jpg)
Generalizing AHAH
Consequences of the Linearity Hypothesis
Let X be r -reduced dimension d , so C∗X = 0 for ∗ ≤ r and ∗ > d
Look at En action.E(k)⊗ (C∗X )⊗k → C∗X .
Left side is non-zero in range k(r + 1)− (k − 1)(n − 1) to kd .Right side is non-zero in range r + 1 to d .
k(r +1)−(k−1)(n−1) = k(r +1−(n−1))+(n−1) = k(r−n+2)+n−1
So if k(r − n + 2) + n − 1 > d the map must be zero.
Limit dimension to p(r − n + 2)− n − 2 or even p(r − n + 2).
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 23 / 24
![Page 98: Cochains and Homotopy Theorymmandell/talks/Fields100831.talk.pdf · Overview Cochains and Homotopy Theory Abstract It is known that the E-infinity algebra structure on the cochain](https://reader033.vdocuments.site/reader033/viewer/2022050605/5fac18a6175d14214a0dffab/html5/thumbnails/98.jpg)
Generalizing AHAH
Generalizing Anick’s HAH Theorem
Conjecture
Let R be a ring containing 1/m for m < p and let X be an r-connectedp(r − n + d)-dimensional simplicial complex. Then C∗(X ; R) isquasi-isomorphic as an En-algebra to a commutative differentialgraded algebra.
M.A.Mandell (IU) Cochains and Homotopy Theory Aug 31 24 / 24