Contractibility of CW complex without Whitehead











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Suppose I have a CW complex $X$ with skeleta $(X_n)_{nge 0}$ such that $pi_k(X)=0$ for all $kge 0$. I want to conclude that $X$ is contractible without invoking Whitehead's theorem.



It would be enough to see that the identity $X$ is nullhomotopic. My strategy would be the following:




  1. Show that all inclusions $i_n:X_nhookrightarrow X$ are null-homotopic,

  2. Conclude somehow that the limit $varinjlim, (i_n)=mathrm{id}$ is null-homotopic.










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  • What is your question: Whether your strategy is adequate or do you want to see a proof?
    – Paul Frost
    Nov 17 at 23:10










  • I want to have a proof but I thought it is a good idea to tell you what I have so far. If there's a proof using another approach, I would be happy, too.
    – FKranhold
    Nov 18 at 10:50















up vote
0
down vote

favorite












Suppose I have a CW complex $X$ with skeleta $(X_n)_{nge 0}$ such that $pi_k(X)=0$ for all $kge 0$. I want to conclude that $X$ is contractible without invoking Whitehead's theorem.



It would be enough to see that the identity $X$ is nullhomotopic. My strategy would be the following:




  1. Show that all inclusions $i_n:X_nhookrightarrow X$ are null-homotopic,

  2. Conclude somehow that the limit $varinjlim, (i_n)=mathrm{id}$ is null-homotopic.










share|cite|improve this question






















  • What is your question: Whether your strategy is adequate or do you want to see a proof?
    – Paul Frost
    Nov 17 at 23:10










  • I want to have a proof but I thought it is a good idea to tell you what I have so far. If there's a proof using another approach, I would be happy, too.
    – FKranhold
    Nov 18 at 10:50













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Suppose I have a CW complex $X$ with skeleta $(X_n)_{nge 0}$ such that $pi_k(X)=0$ for all $kge 0$. I want to conclude that $X$ is contractible without invoking Whitehead's theorem.



It would be enough to see that the identity $X$ is nullhomotopic. My strategy would be the following:




  1. Show that all inclusions $i_n:X_nhookrightarrow X$ are null-homotopic,

  2. Conclude somehow that the limit $varinjlim, (i_n)=mathrm{id}$ is null-homotopic.










share|cite|improve this question













Suppose I have a CW complex $X$ with skeleta $(X_n)_{nge 0}$ such that $pi_k(X)=0$ for all $kge 0$. I want to conclude that $X$ is contractible without invoking Whitehead's theorem.



It would be enough to see that the identity $X$ is nullhomotopic. My strategy would be the following:




  1. Show that all inclusions $i_n:X_nhookrightarrow X$ are null-homotopic,

  2. Conclude somehow that the limit $varinjlim, (i_n)=mathrm{id}$ is null-homotopic.







homotopy-theory cw-complexes higher-homotopy-groups






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asked Nov 17 at 21:16









FKranhold

1787




1787












  • What is your question: Whether your strategy is adequate or do you want to see a proof?
    – Paul Frost
    Nov 17 at 23:10










  • I want to have a proof but I thought it is a good idea to tell you what I have so far. If there's a proof using another approach, I would be happy, too.
    – FKranhold
    Nov 18 at 10:50


















  • What is your question: Whether your strategy is adequate or do you want to see a proof?
    – Paul Frost
    Nov 17 at 23:10










  • I want to have a proof but I thought it is a good idea to tell you what I have so far. If there's a proof using another approach, I would be happy, too.
    – FKranhold
    Nov 18 at 10:50
















What is your question: Whether your strategy is adequate or do you want to see a proof?
– Paul Frost
Nov 17 at 23:10




What is your question: Whether your strategy is adequate or do you want to see a proof?
– Paul Frost
Nov 17 at 23:10












I want to have a proof but I thought it is a good idea to tell you what I have so far. If there's a proof using another approach, I would be happy, too.
– FKranhold
Nov 18 at 10:50




I want to have a proof but I thought it is a good idea to tell you what I have so far. If there's a proof using another approach, I would be happy, too.
– FKranhold
Nov 18 at 10:50















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