Are there prominent examples of operads in schemes?












16














There is an abundance of examples of operads in topological spaces, chain complexes, and simplicial sets. However, there are very few (if any) examples of operads in algebraic geometric objects, even in $mathbb A^{1}$-homotopy theory.



My question is twofold:




  • Are there useful examples of operads in algebraic geometry?


  • Is there some intrinsic property of schemes which makes them incompatible with operatic structures? What about (higher) stacks?



For context, my main interest is in the $E_{n}$ operads. For instance, one would naïvely imagine that the moduli space $M_{0,n}$ of genus-zero marked curves could be an algebraic geometric counterpart of the space of little disks, but there seems to be no way to define the operadic composition without passing to the Deligne–Mumford compactification of the moduli space.










share|cite|improve this question
























  • What's wrong with passing to the Deligne-Mumford compactification of the moduli space?
    – Will Sawin
    Dec 22 at 13:06










  • The homotopy type of the (complex points) of the DM compactification is not equivalent to the space of little disks, so the operad structure is not a model of $E_{n}$.
    – Patrick Elliott
    Dec 22 at 13:54






  • 3




    Sure, but this seems to contradict your earlier claim that there are very few (if any) examples of operads in algebraic geometry. There's an example in your question, and more examples can be constructed from it.
    – Will Sawin
    Dec 22 at 16:09
















16














There is an abundance of examples of operads in topological spaces, chain complexes, and simplicial sets. However, there are very few (if any) examples of operads in algebraic geometric objects, even in $mathbb A^{1}$-homotopy theory.



My question is twofold:




  • Are there useful examples of operads in algebraic geometry?


  • Is there some intrinsic property of schemes which makes them incompatible with operatic structures? What about (higher) stacks?



For context, my main interest is in the $E_{n}$ operads. For instance, one would naïvely imagine that the moduli space $M_{0,n}$ of genus-zero marked curves could be an algebraic geometric counterpart of the space of little disks, but there seems to be no way to define the operadic composition without passing to the Deligne–Mumford compactification of the moduli space.










share|cite|improve this question
























  • What's wrong with passing to the Deligne-Mumford compactification of the moduli space?
    – Will Sawin
    Dec 22 at 13:06










  • The homotopy type of the (complex points) of the DM compactification is not equivalent to the space of little disks, so the operad structure is not a model of $E_{n}$.
    – Patrick Elliott
    Dec 22 at 13:54






  • 3




    Sure, but this seems to contradict your earlier claim that there are very few (if any) examples of operads in algebraic geometry. There's an example in your question, and more examples can be constructed from it.
    – Will Sawin
    Dec 22 at 16:09














16












16








16


5





There is an abundance of examples of operads in topological spaces, chain complexes, and simplicial sets. However, there are very few (if any) examples of operads in algebraic geometric objects, even in $mathbb A^{1}$-homotopy theory.



My question is twofold:




  • Are there useful examples of operads in algebraic geometry?


  • Is there some intrinsic property of schemes which makes them incompatible with operatic structures? What about (higher) stacks?



For context, my main interest is in the $E_{n}$ operads. For instance, one would naïvely imagine that the moduli space $M_{0,n}$ of genus-zero marked curves could be an algebraic geometric counterpart of the space of little disks, but there seems to be no way to define the operadic composition without passing to the Deligne–Mumford compactification of the moduli space.










share|cite|improve this question















There is an abundance of examples of operads in topological spaces, chain complexes, and simplicial sets. However, there are very few (if any) examples of operads in algebraic geometric objects, even in $mathbb A^{1}$-homotopy theory.



My question is twofold:




  • Are there useful examples of operads in algebraic geometry?


  • Is there some intrinsic property of schemes which makes them incompatible with operatic structures? What about (higher) stacks?



For context, my main interest is in the $E_{n}$ operads. For instance, one would naïvely imagine that the moduli space $M_{0,n}$ of genus-zero marked curves could be an algebraic geometric counterpart of the space of little disks, but there seems to be no way to define the operadic composition without passing to the Deligne–Mumford compactification of the moduli space.







ag.algebraic-geometry homotopy-theory operads algebraic-stacks






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 21 at 17:06









Pedro Tamaroff

453414




453414










asked Dec 21 at 12:50









Patrick Elliott

1634




1634












  • What's wrong with passing to the Deligne-Mumford compactification of the moduli space?
    – Will Sawin
    Dec 22 at 13:06










  • The homotopy type of the (complex points) of the DM compactification is not equivalent to the space of little disks, so the operad structure is not a model of $E_{n}$.
    – Patrick Elliott
    Dec 22 at 13:54






  • 3




    Sure, but this seems to contradict your earlier claim that there are very few (if any) examples of operads in algebraic geometry. There's an example in your question, and more examples can be constructed from it.
    – Will Sawin
    Dec 22 at 16:09


















  • What's wrong with passing to the Deligne-Mumford compactification of the moduli space?
    – Will Sawin
    Dec 22 at 13:06










  • The homotopy type of the (complex points) of the DM compactification is not equivalent to the space of little disks, so the operad structure is not a model of $E_{n}$.
    – Patrick Elliott
    Dec 22 at 13:54






  • 3




    Sure, but this seems to contradict your earlier claim that there are very few (if any) examples of operads in algebraic geometry. There's an example in your question, and more examples can be constructed from it.
    – Will Sawin
    Dec 22 at 16:09
















What's wrong with passing to the Deligne-Mumford compactification of the moduli space?
– Will Sawin
Dec 22 at 13:06




What's wrong with passing to the Deligne-Mumford compactification of the moduli space?
– Will Sawin
Dec 22 at 13:06












The homotopy type of the (complex points) of the DM compactification is not equivalent to the space of little disks, so the operad structure is not a model of $E_{n}$.
– Patrick Elliott
Dec 22 at 13:54




The homotopy type of the (complex points) of the DM compactification is not equivalent to the space of little disks, so the operad structure is not a model of $E_{n}$.
– Patrick Elliott
Dec 22 at 13:54




3




3




Sure, but this seems to contradict your earlier claim that there are very few (if any) examples of operads in algebraic geometry. There's an example in your question, and more examples can be constructed from it.
– Will Sawin
Dec 22 at 16:09




Sure, but this seems to contradict your earlier claim that there are very few (if any) examples of operads in algebraic geometry. There's an example in your question, and more examples can be constructed from it.
– Will Sawin
Dec 22 at 16:09










3 Answers
3






active

oldest

votes


















11














Mikhail Kapranov's invited lecture at the 1998 ICM was about exactly this:




Mikhail Kapranov, Operads and algebraic geometry. Documenta Mathematica Extra Volume ICM II (1998), 277-286. (PDF of the whole volume here.)




Abstract:




The study (motivated by mathematical physics) of algebraic varieties related to the moduli spaces of curves, helped to uncover important connections with the abstract algebraic theory of operads. This interaction led to new developments in both theories, and the purpose of the talk is to discuss some of them.







share|cite|improve this answer





























    10














    The homology of $M_{0,n}$ is an operad in a natural way that is compatible with AG structure (like weights). The construction uses the operad structure on the compactification plus Gysin maps-- it is general enough that one would expect it to work in the stable $mathbb A^1$ homotopy category. In fact, there you can likely define it as the Koszul dual operad to the homology of the compactification. I'm not well-informed enough to know whether/where this has been done, or whether the construction should work unstably as well.



    The same goes for the Fulton Macpherson compactification of configuration space in affine space which is closer to the $E_d$ operad.






    share|cite|improve this answer























    • In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
      – Patrick Elliott
      Dec 22 at 12:56






    • 2




      @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
      – Phil Tosteson
      Dec 22 at 23:17





















    10














    I recommend reading the paper Mixed Hodge structures and formality of symmetric monoidal functors by Cirici and Horel. They give several examples, and the paper is a great motivation for why one would be interested in getting operads in schemes (because under good circumstances, they are formal).



    Among the examples they give, you have: the noncommutative associative operad; self maps of the projective line; (actually, a variant of the little disks operad given by parenthesized braids and the gravity operad aren't examples, thanks to Dan Petersen for the clarification).



    (I am not sure that you will be able to view $E_n$ for $n > 2$ as an operad in schemes, but I would be happy if it were the case.)






    share|cite|improve this answer



















    • 3




      Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
      – Dan Petersen
      Dec 21 at 16:34






    • 1




      @Dan Ah, you're probably right. I reread the paper a bit quickly.
      – Najib Idrissi
      Dec 21 at 17:56











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    3 Answers
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    3 Answers
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    active

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    11














    Mikhail Kapranov's invited lecture at the 1998 ICM was about exactly this:




    Mikhail Kapranov, Operads and algebraic geometry. Documenta Mathematica Extra Volume ICM II (1998), 277-286. (PDF of the whole volume here.)




    Abstract:




    The study (motivated by mathematical physics) of algebraic varieties related to the moduli spaces of curves, helped to uncover important connections with the abstract algebraic theory of operads. This interaction led to new developments in both theories, and the purpose of the talk is to discuss some of them.







    share|cite|improve this answer


























      11














      Mikhail Kapranov's invited lecture at the 1998 ICM was about exactly this:




      Mikhail Kapranov, Operads and algebraic geometry. Documenta Mathematica Extra Volume ICM II (1998), 277-286. (PDF of the whole volume here.)




      Abstract:




      The study (motivated by mathematical physics) of algebraic varieties related to the moduli spaces of curves, helped to uncover important connections with the abstract algebraic theory of operads. This interaction led to new developments in both theories, and the purpose of the talk is to discuss some of them.







      share|cite|improve this answer
























        11












        11








        11






        Mikhail Kapranov's invited lecture at the 1998 ICM was about exactly this:




        Mikhail Kapranov, Operads and algebraic geometry. Documenta Mathematica Extra Volume ICM II (1998), 277-286. (PDF of the whole volume here.)




        Abstract:




        The study (motivated by mathematical physics) of algebraic varieties related to the moduli spaces of curves, helped to uncover important connections with the abstract algebraic theory of operads. This interaction led to new developments in both theories, and the purpose of the talk is to discuss some of them.







        share|cite|improve this answer












        Mikhail Kapranov's invited lecture at the 1998 ICM was about exactly this:




        Mikhail Kapranov, Operads and algebraic geometry. Documenta Mathematica Extra Volume ICM II (1998), 277-286. (PDF of the whole volume here.)




        Abstract:




        The study (motivated by mathematical physics) of algebraic varieties related to the moduli spaces of curves, helped to uncover important connections with the abstract algebraic theory of operads. This interaction led to new developments in both theories, and the purpose of the talk is to discuss some of them.








        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 21 at 16:31









        Tom Leinster

        19.2k475127




        19.2k475127























            10














            The homology of $M_{0,n}$ is an operad in a natural way that is compatible with AG structure (like weights). The construction uses the operad structure on the compactification plus Gysin maps-- it is general enough that one would expect it to work in the stable $mathbb A^1$ homotopy category. In fact, there you can likely define it as the Koszul dual operad to the homology of the compactification. I'm not well-informed enough to know whether/where this has been done, or whether the construction should work unstably as well.



            The same goes for the Fulton Macpherson compactification of configuration space in affine space which is closer to the $E_d$ operad.






            share|cite|improve this answer























            • In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
              – Patrick Elliott
              Dec 22 at 12:56






            • 2




              @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
              – Phil Tosteson
              Dec 22 at 23:17


















            10














            The homology of $M_{0,n}$ is an operad in a natural way that is compatible with AG structure (like weights). The construction uses the operad structure on the compactification plus Gysin maps-- it is general enough that one would expect it to work in the stable $mathbb A^1$ homotopy category. In fact, there you can likely define it as the Koszul dual operad to the homology of the compactification. I'm not well-informed enough to know whether/where this has been done, or whether the construction should work unstably as well.



            The same goes for the Fulton Macpherson compactification of configuration space in affine space which is closer to the $E_d$ operad.






            share|cite|improve this answer























            • In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
              – Patrick Elliott
              Dec 22 at 12:56






            • 2




              @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
              – Phil Tosteson
              Dec 22 at 23:17
















            10












            10








            10






            The homology of $M_{0,n}$ is an operad in a natural way that is compatible with AG structure (like weights). The construction uses the operad structure on the compactification plus Gysin maps-- it is general enough that one would expect it to work in the stable $mathbb A^1$ homotopy category. In fact, there you can likely define it as the Koszul dual operad to the homology of the compactification. I'm not well-informed enough to know whether/where this has been done, or whether the construction should work unstably as well.



            The same goes for the Fulton Macpherson compactification of configuration space in affine space which is closer to the $E_d$ operad.






            share|cite|improve this answer














            The homology of $M_{0,n}$ is an operad in a natural way that is compatible with AG structure (like weights). The construction uses the operad structure on the compactification plus Gysin maps-- it is general enough that one would expect it to work in the stable $mathbb A^1$ homotopy category. In fact, there you can likely define it as the Koszul dual operad to the homology of the compactification. I'm not well-informed enough to know whether/where this has been done, or whether the construction should work unstably as well.



            The same goes for the Fulton Macpherson compactification of configuration space in affine space which is closer to the $E_d$ operad.







            share|cite|improve this answer














            share|cite|improve this answer



            share|cite|improve this answer








            edited Dec 21 at 15:19

























            answered Dec 21 at 13:44









            Phil Tosteson

            853158




            853158












            • In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
              – Patrick Elliott
              Dec 22 at 12:56






            • 2




              @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
              – Phil Tosteson
              Dec 22 at 23:17




















            • In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
              – Patrick Elliott
              Dec 22 at 12:56






            • 2




              @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
              – Phil Tosteson
              Dec 22 at 23:17


















            In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
            – Patrick Elliott
            Dec 22 at 12:56




            In what sense is the Fulton Macpherson compactifticaion of configuration space on affine space related to the $E_{d}$ operad? Obviously the spaces are homotopy equivalent, but to my knowledge there is no operad structure (as schemes) on the FM-compactified configuration spaces.
            – Patrick Elliott
            Dec 22 at 12:56




            2




            2




            @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
            – Phil Tosteson
            Dec 22 at 23:17






            @Patrick By the Fulton Macpherson compactification, I meant the complex version, not the real one. Unless I'm missing something, this is still an operad in schemes, even though it's not cyclic. However the relationship of the complex version to $E_d$ is not as clear, so it's good you asked.
            – Phil Tosteson
            Dec 22 at 23:17













            10














            I recommend reading the paper Mixed Hodge structures and formality of symmetric monoidal functors by Cirici and Horel. They give several examples, and the paper is a great motivation for why one would be interested in getting operads in schemes (because under good circumstances, they are formal).



            Among the examples they give, you have: the noncommutative associative operad; self maps of the projective line; (actually, a variant of the little disks operad given by parenthesized braids and the gravity operad aren't examples, thanks to Dan Petersen for the clarification).



            (I am not sure that you will be able to view $E_n$ for $n > 2$ as an operad in schemes, but I would be happy if it were the case.)






            share|cite|improve this answer



















            • 3




              Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
              – Dan Petersen
              Dec 21 at 16:34






            • 1




              @Dan Ah, you're probably right. I reread the paper a bit quickly.
              – Najib Idrissi
              Dec 21 at 17:56
















            10














            I recommend reading the paper Mixed Hodge structures and formality of symmetric monoidal functors by Cirici and Horel. They give several examples, and the paper is a great motivation for why one would be interested in getting operads in schemes (because under good circumstances, they are formal).



            Among the examples they give, you have: the noncommutative associative operad; self maps of the projective line; (actually, a variant of the little disks operad given by parenthesized braids and the gravity operad aren't examples, thanks to Dan Petersen for the clarification).



            (I am not sure that you will be able to view $E_n$ for $n > 2$ as an operad in schemes, but I would be happy if it were the case.)






            share|cite|improve this answer



















            • 3




              Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
              – Dan Petersen
              Dec 21 at 16:34






            • 1




              @Dan Ah, you're probably right. I reread the paper a bit quickly.
              – Najib Idrissi
              Dec 21 at 17:56














            10












            10








            10






            I recommend reading the paper Mixed Hodge structures and formality of symmetric monoidal functors by Cirici and Horel. They give several examples, and the paper is a great motivation for why one would be interested in getting operads in schemes (because under good circumstances, they are formal).



            Among the examples they give, you have: the noncommutative associative operad; self maps of the projective line; (actually, a variant of the little disks operad given by parenthesized braids and the gravity operad aren't examples, thanks to Dan Petersen for the clarification).



            (I am not sure that you will be able to view $E_n$ for $n > 2$ as an operad in schemes, but I would be happy if it were the case.)






            share|cite|improve this answer














            I recommend reading the paper Mixed Hodge structures and formality of symmetric monoidal functors by Cirici and Horel. They give several examples, and the paper is a great motivation for why one would be interested in getting operads in schemes (because under good circumstances, they are formal).



            Among the examples they give, you have: the noncommutative associative operad; self maps of the projective line; (actually, a variant of the little disks operad given by parenthesized braids and the gravity operad aren't examples, thanks to Dan Petersen for the clarification).



            (I am not sure that you will be able to view $E_n$ for $n > 2$ as an operad in schemes, but I would be happy if it were the case.)







            share|cite|improve this answer














            share|cite|improve this answer



            share|cite|improve this answer








            edited Dec 22 at 12:56

























            answered Dec 21 at 15:18









            Najib Idrissi

            1,6791027




            1,6791027








            • 3




              Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
              – Dan Petersen
              Dec 21 at 16:34






            • 1




              @Dan Ah, you're probably right. I reread the paper a bit quickly.
              – Najib Idrissi
              Dec 21 at 17:56














            • 3




              Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
              – Dan Petersen
              Dec 21 at 16:34






            • 1




              @Dan Ah, you're probably right. I reread the paper a bit quickly.
              – Najib Idrissi
              Dec 21 at 17:56








            3




            3




            Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
            – Dan Petersen
            Dec 21 at 16:34




            Neither the gravity operad nor the paranthesized braid operad come from an operad in schemes. In both cases the operad structure exists only on the level of homology, as in Phil's answer.
            – Dan Petersen
            Dec 21 at 16:34




            1




            1




            @Dan Ah, you're probably right. I reread the paper a bit quickly.
            – Najib Idrissi
            Dec 21 at 17:56




            @Dan Ah, you're probably right. I reread the paper a bit quickly.
            – Najib Idrissi
            Dec 21 at 17:56


















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