Reference request for K-Theory linearization












7














I posted this question on math.se here:https://math.stackexchange.com/q/2996787/482732, but I think it may be more appropriate here, sorry if I am wrong about that.



In Waldhausen's paper Algebraic K theory of Spaces(the long one) he proves the following:



$$A(X)simeq mathbb{Z}times Bwidehat{Gl}(Omega^{infty}Sigma^infty |G|)$$



Where $|G|$ is a loop group of $X$. My problem is that to apply $B$ we need $widehat{Gl}(Omega^{infty}Sigma^infty |G|)$ to be $A^infty$, but since $Omega^{infty}Sigma^infty |G|$ is only a ring up to homotopy this isn't obvious to me. Waldhausen just brushes past this point, so I was hoping to get a reference to somewhere that shows this in detail. Thanks.










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  • 1




    Uh, I might be a bit confused, but $Omega^inftySigma^infty_+ |G|$ is certainly an $A_infty$-ring
    – Denis Nardin
    Nov 13 at 15:49










  • @DenisNardin I understand why both operations separately are $A^infty$, I just don't understand the distributivity I suppose.
    – Noah Riggenbach
    Nov 13 at 15:57
















7














I posted this question on math.se here:https://math.stackexchange.com/q/2996787/482732, but I think it may be more appropriate here, sorry if I am wrong about that.



In Waldhausen's paper Algebraic K theory of Spaces(the long one) he proves the following:



$$A(X)simeq mathbb{Z}times Bwidehat{Gl}(Omega^{infty}Sigma^infty |G|)$$



Where $|G|$ is a loop group of $X$. My problem is that to apply $B$ we need $widehat{Gl}(Omega^{infty}Sigma^infty |G|)$ to be $A^infty$, but since $Omega^{infty}Sigma^infty |G|$ is only a ring up to homotopy this isn't obvious to me. Waldhausen just brushes past this point, so I was hoping to get a reference to somewhere that shows this in detail. Thanks.










share|cite|improve this question




















  • 1




    Uh, I might be a bit confused, but $Omega^inftySigma^infty_+ |G|$ is certainly an $A_infty$-ring
    – Denis Nardin
    Nov 13 at 15:49










  • @DenisNardin I understand why both operations separately are $A^infty$, I just don't understand the distributivity I suppose.
    – Noah Riggenbach
    Nov 13 at 15:57














7












7








7


1





I posted this question on math.se here:https://math.stackexchange.com/q/2996787/482732, but I think it may be more appropriate here, sorry if I am wrong about that.



In Waldhausen's paper Algebraic K theory of Spaces(the long one) he proves the following:



$$A(X)simeq mathbb{Z}times Bwidehat{Gl}(Omega^{infty}Sigma^infty |G|)$$



Where $|G|$ is a loop group of $X$. My problem is that to apply $B$ we need $widehat{Gl}(Omega^{infty}Sigma^infty |G|)$ to be $A^infty$, but since $Omega^{infty}Sigma^infty |G|$ is only a ring up to homotopy this isn't obvious to me. Waldhausen just brushes past this point, so I was hoping to get a reference to somewhere that shows this in detail. Thanks.










share|cite|improve this question















I posted this question on math.se here:https://math.stackexchange.com/q/2996787/482732, but I think it may be more appropriate here, sorry if I am wrong about that.



In Waldhausen's paper Algebraic K theory of Spaces(the long one) he proves the following:



$$A(X)simeq mathbb{Z}times Bwidehat{Gl}(Omega^{infty}Sigma^infty |G|)$$



Where $|G|$ is a loop group of $X$. My problem is that to apply $B$ we need $widehat{Gl}(Omega^{infty}Sigma^infty |G|)$ to be $A^infty$, but since $Omega^{infty}Sigma^infty |G|$ is only a ring up to homotopy this isn't obvious to me. Waldhausen just brushes past this point, so I was hoping to get a reference to somewhere that shows this in detail. Thanks.







reference-request homotopy-theory kt.k-theory-and-homology






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edited Nov 13 at 15:54

























asked Nov 13 at 15:41









Noah Riggenbach

1385




1385








  • 1




    Uh, I might be a bit confused, but $Omega^inftySigma^infty_+ |G|$ is certainly an $A_infty$-ring
    – Denis Nardin
    Nov 13 at 15:49










  • @DenisNardin I understand why both operations separately are $A^infty$, I just don't understand the distributivity I suppose.
    – Noah Riggenbach
    Nov 13 at 15:57














  • 1




    Uh, I might be a bit confused, but $Omega^inftySigma^infty_+ |G|$ is certainly an $A_infty$-ring
    – Denis Nardin
    Nov 13 at 15:49










  • @DenisNardin I understand why both operations separately are $A^infty$, I just don't understand the distributivity I suppose.
    – Noah Riggenbach
    Nov 13 at 15:57








1




1




Uh, I might be a bit confused, but $Omega^inftySigma^infty_+ |G|$ is certainly an $A_infty$-ring
– Denis Nardin
Nov 13 at 15:49




Uh, I might be a bit confused, but $Omega^inftySigma^infty_+ |G|$ is certainly an $A_infty$-ring
– Denis Nardin
Nov 13 at 15:49












@DenisNardin I understand why both operations separately are $A^infty$, I just don't understand the distributivity I suppose.
– Noah Riggenbach
Nov 13 at 15:57




@DenisNardin I understand why both operations separately are $A^infty$, I just don't understand the distributivity I suppose.
– Noah Riggenbach
Nov 13 at 15:57










1 Answer
1






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9














I claim that for every $A_infty$-space $A$, there is a canonical $A_infty$-ring structure on $Omega^inftySigma^infty_+A$.



First, $Sigma^infty_+$ from spaces to spectra is symmetric monoidal. So it sends an $A_infty$-space $A$ to an $A_infty$-algebra in spectra $Sigma^infty_+A$, that is an $A_infty$-ring spectrum. The fact that $Sigma^infty_+$ is symmetric monoidal (at the model category/∞-category level) can be found in any modern book treating the smash product of spectra (e.g. it is proposition 4.7 in Elmendorf-May-Kriz-Mandell and corollary 4.8.2.19 in Lurie's Higher Algebra).



Secondly I claim that if $E$ is an $A_infty$-ring spectrum, then $Omega^infty E$ has a canonical $A_infty$-ring space structure. Exactly how this works will depend on your preferred definition of $A_infty$-ring space, but it can be proven, e.g., with the same technique that May uses to prove the analogous statement for $E_infty$-ring spaces (Corollary 7.5 in May's What precisely are $E_infty$-ring spaces and $E_infty$-ring spectra).





If all you care for is a construction of the $A_infty$-structure on $GL_1(Sigma^infty_+A)$, I particularly like the approach in




Matthew Ando, Andrew J. Blumberg, David Gepner, Michael J. Hopkins, Charles Rezk An ∞-categorical approach to R-line bundles, R-module Thom spectra, and twisted R-homology




where they identify $GL_1(R)$ with the automorphism group of $R$ as an $R$-module (and so it has an $A_infty$-structure, since all automorphism groups in an ∞-category "trivially" do).






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    9














    I claim that for every $A_infty$-space $A$, there is a canonical $A_infty$-ring structure on $Omega^inftySigma^infty_+A$.



    First, $Sigma^infty_+$ from spaces to spectra is symmetric monoidal. So it sends an $A_infty$-space $A$ to an $A_infty$-algebra in spectra $Sigma^infty_+A$, that is an $A_infty$-ring spectrum. The fact that $Sigma^infty_+$ is symmetric monoidal (at the model category/∞-category level) can be found in any modern book treating the smash product of spectra (e.g. it is proposition 4.7 in Elmendorf-May-Kriz-Mandell and corollary 4.8.2.19 in Lurie's Higher Algebra).



    Secondly I claim that if $E$ is an $A_infty$-ring spectrum, then $Omega^infty E$ has a canonical $A_infty$-ring space structure. Exactly how this works will depend on your preferred definition of $A_infty$-ring space, but it can be proven, e.g., with the same technique that May uses to prove the analogous statement for $E_infty$-ring spaces (Corollary 7.5 in May's What precisely are $E_infty$-ring spaces and $E_infty$-ring spectra).





    If all you care for is a construction of the $A_infty$-structure on $GL_1(Sigma^infty_+A)$, I particularly like the approach in




    Matthew Ando, Andrew J. Blumberg, David Gepner, Michael J. Hopkins, Charles Rezk An ∞-categorical approach to R-line bundles, R-module Thom spectra, and twisted R-homology




    where they identify $GL_1(R)$ with the automorphism group of $R$ as an $R$-module (and so it has an $A_infty$-structure, since all automorphism groups in an ∞-category "trivially" do).






    share|cite|improve this answer


























      9














      I claim that for every $A_infty$-space $A$, there is a canonical $A_infty$-ring structure on $Omega^inftySigma^infty_+A$.



      First, $Sigma^infty_+$ from spaces to spectra is symmetric monoidal. So it sends an $A_infty$-space $A$ to an $A_infty$-algebra in spectra $Sigma^infty_+A$, that is an $A_infty$-ring spectrum. The fact that $Sigma^infty_+$ is symmetric monoidal (at the model category/∞-category level) can be found in any modern book treating the smash product of spectra (e.g. it is proposition 4.7 in Elmendorf-May-Kriz-Mandell and corollary 4.8.2.19 in Lurie's Higher Algebra).



      Secondly I claim that if $E$ is an $A_infty$-ring spectrum, then $Omega^infty E$ has a canonical $A_infty$-ring space structure. Exactly how this works will depend on your preferred definition of $A_infty$-ring space, but it can be proven, e.g., with the same technique that May uses to prove the analogous statement for $E_infty$-ring spaces (Corollary 7.5 in May's What precisely are $E_infty$-ring spaces and $E_infty$-ring spectra).





      If all you care for is a construction of the $A_infty$-structure on $GL_1(Sigma^infty_+A)$, I particularly like the approach in




      Matthew Ando, Andrew J. Blumberg, David Gepner, Michael J. Hopkins, Charles Rezk An ∞-categorical approach to R-line bundles, R-module Thom spectra, and twisted R-homology




      where they identify $GL_1(R)$ with the automorphism group of $R$ as an $R$-module (and so it has an $A_infty$-structure, since all automorphism groups in an ∞-category "trivially" do).






      share|cite|improve this answer
























        9












        9








        9






        I claim that for every $A_infty$-space $A$, there is a canonical $A_infty$-ring structure on $Omega^inftySigma^infty_+A$.



        First, $Sigma^infty_+$ from spaces to spectra is symmetric monoidal. So it sends an $A_infty$-space $A$ to an $A_infty$-algebra in spectra $Sigma^infty_+A$, that is an $A_infty$-ring spectrum. The fact that $Sigma^infty_+$ is symmetric monoidal (at the model category/∞-category level) can be found in any modern book treating the smash product of spectra (e.g. it is proposition 4.7 in Elmendorf-May-Kriz-Mandell and corollary 4.8.2.19 in Lurie's Higher Algebra).



        Secondly I claim that if $E$ is an $A_infty$-ring spectrum, then $Omega^infty E$ has a canonical $A_infty$-ring space structure. Exactly how this works will depend on your preferred definition of $A_infty$-ring space, but it can be proven, e.g., with the same technique that May uses to prove the analogous statement for $E_infty$-ring spaces (Corollary 7.5 in May's What precisely are $E_infty$-ring spaces and $E_infty$-ring spectra).





        If all you care for is a construction of the $A_infty$-structure on $GL_1(Sigma^infty_+A)$, I particularly like the approach in




        Matthew Ando, Andrew J. Blumberg, David Gepner, Michael J. Hopkins, Charles Rezk An ∞-categorical approach to R-line bundles, R-module Thom spectra, and twisted R-homology




        where they identify $GL_1(R)$ with the automorphism group of $R$ as an $R$-module (and so it has an $A_infty$-structure, since all automorphism groups in an ∞-category "trivially" do).






        share|cite|improve this answer












        I claim that for every $A_infty$-space $A$, there is a canonical $A_infty$-ring structure on $Omega^inftySigma^infty_+A$.



        First, $Sigma^infty_+$ from spaces to spectra is symmetric monoidal. So it sends an $A_infty$-space $A$ to an $A_infty$-algebra in spectra $Sigma^infty_+A$, that is an $A_infty$-ring spectrum. The fact that $Sigma^infty_+$ is symmetric monoidal (at the model category/∞-category level) can be found in any modern book treating the smash product of spectra (e.g. it is proposition 4.7 in Elmendorf-May-Kriz-Mandell and corollary 4.8.2.19 in Lurie's Higher Algebra).



        Secondly I claim that if $E$ is an $A_infty$-ring spectrum, then $Omega^infty E$ has a canonical $A_infty$-ring space structure. Exactly how this works will depend on your preferred definition of $A_infty$-ring space, but it can be proven, e.g., with the same technique that May uses to prove the analogous statement for $E_infty$-ring spaces (Corollary 7.5 in May's What precisely are $E_infty$-ring spaces and $E_infty$-ring spectra).





        If all you care for is a construction of the $A_infty$-structure on $GL_1(Sigma^infty_+A)$, I particularly like the approach in




        Matthew Ando, Andrew J. Blumberg, David Gepner, Michael J. Hopkins, Charles Rezk An ∞-categorical approach to R-line bundles, R-module Thom spectra, and twisted R-homology




        where they identify $GL_1(R)$ with the automorphism group of $R$ as an $R$-module (and so it has an $A_infty$-structure, since all automorphism groups in an ∞-category "trivially" do).







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 13 at 16:48









        Denis Nardin

        7,92223158




        7,92223158






























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