Quasicoherent sheaves on the groupoid of vector bundles on a surface












2












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Consider the groupoid $Vect_n(S)$ of rank n-vector bundles over a projective surface $S$. What does it mean to have a sheaf $$mathcal Lin QCoh(Vect_n(S))?$$ A notion of quasicoherent sheaf on a groupoid should be involved, but I guess that the groupoid should have "some topology".



Sorry for the vagueness of the question, but I have been spoken about this and I realise I don't quite understand the notion.



Thank you in advance.










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$endgroup$












  • $begingroup$
    Do you know what is a stack ?
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:22










  • $begingroup$
    Yes. Does this follow from the notion of sheaf on a stack? And if so, how?
    $endgroup$
    – W. Rether
    Dec 9 '18 at 21:33






  • 1




    $begingroup$
    Qiaochu answered for me : $Vect_n(S)$ is a stack and there is a notion of sheaf on a stack which is what is meant here.
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:50
















2












$begingroup$


Consider the groupoid $Vect_n(S)$ of rank n-vector bundles over a projective surface $S$. What does it mean to have a sheaf $$mathcal Lin QCoh(Vect_n(S))?$$ A notion of quasicoherent sheaf on a groupoid should be involved, but I guess that the groupoid should have "some topology".



Sorry for the vagueness of the question, but I have been spoken about this and I realise I don't quite understand the notion.



Thank you in advance.










share|cite|improve this question









$endgroup$












  • $begingroup$
    Do you know what is a stack ?
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:22










  • $begingroup$
    Yes. Does this follow from the notion of sheaf on a stack? And if so, how?
    $endgroup$
    – W. Rether
    Dec 9 '18 at 21:33






  • 1




    $begingroup$
    Qiaochu answered for me : $Vect_n(S)$ is a stack and there is a notion of sheaf on a stack which is what is meant here.
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:50














2












2








2





$begingroup$


Consider the groupoid $Vect_n(S)$ of rank n-vector bundles over a projective surface $S$. What does it mean to have a sheaf $$mathcal Lin QCoh(Vect_n(S))?$$ A notion of quasicoherent sheaf on a groupoid should be involved, but I guess that the groupoid should have "some topology".



Sorry for the vagueness of the question, but I have been spoken about this and I realise I don't quite understand the notion.



Thank you in advance.










share|cite|improve this question









$endgroup$




Consider the groupoid $Vect_n(S)$ of rank n-vector bundles over a projective surface $S$. What does it mean to have a sheaf $$mathcal Lin QCoh(Vect_n(S))?$$ A notion of quasicoherent sheaf on a groupoid should be involved, but I guess that the groupoid should have "some topology".



Sorry for the vagueness of the question, but I have been spoken about this and I realise I don't quite understand the notion.



Thank you in advance.







algebraic-geometry vector-bundles quasicoherent-sheaves






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share|cite|improve this question




share|cite|improve this question










asked Dec 9 '18 at 15:42









W. RetherW. Rether

738417




738417












  • $begingroup$
    Do you know what is a stack ?
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:22










  • $begingroup$
    Yes. Does this follow from the notion of sheaf on a stack? And if so, how?
    $endgroup$
    – W. Rether
    Dec 9 '18 at 21:33






  • 1




    $begingroup$
    Qiaochu answered for me : $Vect_n(S)$ is a stack and there is a notion of sheaf on a stack which is what is meant here.
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:50


















  • $begingroup$
    Do you know what is a stack ?
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:22










  • $begingroup$
    Yes. Does this follow from the notion of sheaf on a stack? And if so, how?
    $endgroup$
    – W. Rether
    Dec 9 '18 at 21:33






  • 1




    $begingroup$
    Qiaochu answered for me : $Vect_n(S)$ is a stack and there is a notion of sheaf on a stack which is what is meant here.
    $endgroup$
    – Nicolas Hemelsoet
    Dec 9 '18 at 21:50
















$begingroup$
Do you know what is a stack ?
$endgroup$
– Nicolas Hemelsoet
Dec 9 '18 at 21:22




$begingroup$
Do you know what is a stack ?
$endgroup$
– Nicolas Hemelsoet
Dec 9 '18 at 21:22












$begingroup$
Yes. Does this follow from the notion of sheaf on a stack? And if so, how?
$endgroup$
– W. Rether
Dec 9 '18 at 21:33




$begingroup$
Yes. Does this follow from the notion of sheaf on a stack? And if so, how?
$endgroup$
– W. Rether
Dec 9 '18 at 21:33




1




1




$begingroup$
Qiaochu answered for me : $Vect_n(S)$ is a stack and there is a notion of sheaf on a stack which is what is meant here.
$endgroup$
– Nicolas Hemelsoet
Dec 9 '18 at 21:50




$begingroup$
Qiaochu answered for me : $Vect_n(S)$ is a stack and there is a notion of sheaf on a stack which is what is meant here.
$endgroup$
– Nicolas Hemelsoet
Dec 9 '18 at 21:50










1 Answer
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$begingroup$

$text{Vect}_n(S)$ is a stack, not a groupoid. Its functor of points sends a commutative ring $R$ to the groupoid of rank $n$ vector bundles on $S times text{Spec } R$. $L$ is a quasicoherent sheaf on this stack.






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    $begingroup$

    $text{Vect}_n(S)$ is a stack, not a groupoid. Its functor of points sends a commutative ring $R$ to the groupoid of rank $n$ vector bundles on $S times text{Spec } R$. $L$ is a quasicoherent sheaf on this stack.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      $text{Vect}_n(S)$ is a stack, not a groupoid. Its functor of points sends a commutative ring $R$ to the groupoid of rank $n$ vector bundles on $S times text{Spec } R$. $L$ is a quasicoherent sheaf on this stack.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        $text{Vect}_n(S)$ is a stack, not a groupoid. Its functor of points sends a commutative ring $R$ to the groupoid of rank $n$ vector bundles on $S times text{Spec } R$. $L$ is a quasicoherent sheaf on this stack.






        share|cite|improve this answer









        $endgroup$



        $text{Vect}_n(S)$ is a stack, not a groupoid. Its functor of points sends a commutative ring $R$ to the groupoid of rank $n$ vector bundles on $S times text{Spec } R$. $L$ is a quasicoherent sheaf on this stack.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 9 '18 at 21:36









        Qiaochu YuanQiaochu Yuan

        279k32588932




        279k32588932






























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