Any spin $M^3$, exists a natural induced $text{Pin}^-$ structure on Poincare dual PD











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It seems that "R. C. Kirby and L. R. Taylor, Pin structures on low-dimensional manifolds (1990)" shows




given a spin structure on $M^3$, the submanifold $text{PD}(a)$ can be given a natural induced $text{Pin}^-$ structure.




$text{PD}(a)$ is a smooth, possibly non-orientable submanifold in $M^3$ representing Poincare dual to $ain H^1(M^3,mathbb{Z}_2)$ (it always exist in codimension 1 case).



Question 1: How do we digest this is always true?



My take is that:




  • (1) The normal bundle to the submanifold $text{PD}(a)equiv N^2subset M^3$ for oriented $M^3$ can be realized as
    determinant line bundle
    $det T{N^2}$, so that $TM^3|_{N^2}=TN^2oplus det TN^2$.


  • (2) For a general vector bundle $V$, there is a natural bijection between Pin$^-$- structures on $V$ and Spin-structures on $Voplus det V$.



Question 2: How can one show that (2) is true?










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    up vote
    2
    down vote

    favorite
    1












    It seems that "R. C. Kirby and L. R. Taylor, Pin structures on low-dimensional manifolds (1990)" shows




    given a spin structure on $M^3$, the submanifold $text{PD}(a)$ can be given a natural induced $text{Pin}^-$ structure.




    $text{PD}(a)$ is a smooth, possibly non-orientable submanifold in $M^3$ representing Poincare dual to $ain H^1(M^3,mathbb{Z}_2)$ (it always exist in codimension 1 case).



    Question 1: How do we digest this is always true?



    My take is that:




    • (1) The normal bundle to the submanifold $text{PD}(a)equiv N^2subset M^3$ for oriented $M^3$ can be realized as
      determinant line bundle
      $det T{N^2}$, so that $TM^3|_{N^2}=TN^2oplus det TN^2$.


    • (2) For a general vector bundle $V$, there is a natural bijection between Pin$^-$- structures on $V$ and Spin-structures on $Voplus det V$.



    Question 2: How can one show that (2) is true?










    share|cite|improve this question
























      up vote
      2
      down vote

      favorite
      1









      up vote
      2
      down vote

      favorite
      1






      1





      It seems that "R. C. Kirby and L. R. Taylor, Pin structures on low-dimensional manifolds (1990)" shows




      given a spin structure on $M^3$, the submanifold $text{PD}(a)$ can be given a natural induced $text{Pin}^-$ structure.




      $text{PD}(a)$ is a smooth, possibly non-orientable submanifold in $M^3$ representing Poincare dual to $ain H^1(M^3,mathbb{Z}_2)$ (it always exist in codimension 1 case).



      Question 1: How do we digest this is always true?



      My take is that:




      • (1) The normal bundle to the submanifold $text{PD}(a)equiv N^2subset M^3$ for oriented $M^3$ can be realized as
        determinant line bundle
        $det T{N^2}$, so that $TM^3|_{N^2}=TN^2oplus det TN^2$.


      • (2) For a general vector bundle $V$, there is a natural bijection between Pin$^-$- structures on $V$ and Spin-structures on $Voplus det V$.



      Question 2: How can one show that (2) is true?










      share|cite|improve this question













      It seems that "R. C. Kirby and L. R. Taylor, Pin structures on low-dimensional manifolds (1990)" shows




      given a spin structure on $M^3$, the submanifold $text{PD}(a)$ can be given a natural induced $text{Pin}^-$ structure.




      $text{PD}(a)$ is a smooth, possibly non-orientable submanifold in $M^3$ representing Poincare dual to $ain H^1(M^3,mathbb{Z}_2)$ (it always exist in codimension 1 case).



      Question 1: How do we digest this is always true?



      My take is that:




      • (1) The normal bundle to the submanifold $text{PD}(a)equiv N^2subset M^3$ for oriented $M^3$ can be realized as
        determinant line bundle
        $det T{N^2}$, so that $TM^3|_{N^2}=TN^2oplus det TN^2$.


      • (2) For a general vector bundle $V$, there is a natural bijection between Pin$^-$- structures on $V$ and Spin-structures on $Voplus det V$.



      Question 2: How can one show that (2) is true?







      algebraic-topology manifolds geometric-topology fiber-bundles spin-geometry






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      asked Nov 16 at 22:48









      wonderich

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