How to apply a double centralizer property on a faithful module of a self-injective Artin algebra?












4












$begingroup$


Let all considered algebras be Artin algebras and let all considered modules be finitely generated.



Let $A$ be left-QF-3 with minimal faithful left ideal $Ae$. Then the following are equivalent:



$bullet$ $Ae$-dom.dim.$(A)geq 2$



$bullet$ There holds a double centralizer property $A=text{End}(Ae_{eAe})$



(This is theorem 2.10 of http://www.sciencedirect.com/science/article/pii/S002186930098726X#).



Corollary 2.11 of the same paper states:



Let $A$ be a self-injectie algebra, let $M$ be a faithful
$A$-module, and let $B:=text{End}_A(M)$. Then there is a double centralizer property $A=text{End}(M_B)$.



The proof of 2.11 shows that dom.dim.($B$)$geq 2$.



Now my question is:




How to apply 2.10 in order to show 2.11?




It seems that the $M$ in 2.11 is the $Ae$ in 2.10. But why is $M$ projective? and must $M$ be a minimal faithful projective module?



Thanks for the help.










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$endgroup$

















    4












    $begingroup$


    Let all considered algebras be Artin algebras and let all considered modules be finitely generated.



    Let $A$ be left-QF-3 with minimal faithful left ideal $Ae$. Then the following are equivalent:



    $bullet$ $Ae$-dom.dim.$(A)geq 2$



    $bullet$ There holds a double centralizer property $A=text{End}(Ae_{eAe})$



    (This is theorem 2.10 of http://www.sciencedirect.com/science/article/pii/S002186930098726X#).



    Corollary 2.11 of the same paper states:



    Let $A$ be a self-injectie algebra, let $M$ be a faithful
    $A$-module, and let $B:=text{End}_A(M)$. Then there is a double centralizer property $A=text{End}(M_B)$.



    The proof of 2.11 shows that dom.dim.($B$)$geq 2$.



    Now my question is:




    How to apply 2.10 in order to show 2.11?




    It seems that the $M$ in 2.11 is the $Ae$ in 2.10. But why is $M$ projective? and must $M$ be a minimal faithful projective module?



    Thanks for the help.










    share|cite|improve this question









    $endgroup$















      4












      4








      4





      $begingroup$


      Let all considered algebras be Artin algebras and let all considered modules be finitely generated.



      Let $A$ be left-QF-3 with minimal faithful left ideal $Ae$. Then the following are equivalent:



      $bullet$ $Ae$-dom.dim.$(A)geq 2$



      $bullet$ There holds a double centralizer property $A=text{End}(Ae_{eAe})$



      (This is theorem 2.10 of http://www.sciencedirect.com/science/article/pii/S002186930098726X#).



      Corollary 2.11 of the same paper states:



      Let $A$ be a self-injectie algebra, let $M$ be a faithful
      $A$-module, and let $B:=text{End}_A(M)$. Then there is a double centralizer property $A=text{End}(M_B)$.



      The proof of 2.11 shows that dom.dim.($B$)$geq 2$.



      Now my question is:




      How to apply 2.10 in order to show 2.11?




      It seems that the $M$ in 2.11 is the $Ae$ in 2.10. But why is $M$ projective? and must $M$ be a minimal faithful projective module?



      Thanks for the help.










      share|cite|improve this question









      $endgroup$




      Let all considered algebras be Artin algebras and let all considered modules be finitely generated.



      Let $A$ be left-QF-3 with minimal faithful left ideal $Ae$. Then the following are equivalent:



      $bullet$ $Ae$-dom.dim.$(A)geq 2$



      $bullet$ There holds a double centralizer property $A=text{End}(Ae_{eAe})$



      (This is theorem 2.10 of http://www.sciencedirect.com/science/article/pii/S002186930098726X#).



      Corollary 2.11 of the same paper states:



      Let $A$ be a self-injectie algebra, let $M$ be a faithful
      $A$-module, and let $B:=text{End}_A(M)$. Then there is a double centralizer property $A=text{End}(M_B)$.



      The proof of 2.11 shows that dom.dim.($B$)$geq 2$.



      Now my question is:




      How to apply 2.10 in order to show 2.11?




      It seems that the $M$ in 2.11 is the $Ae$ in 2.10. But why is $M$ projective? and must $M$ be a minimal faithful projective module?



      Thanks for the help.







      abstract-algebra ring-theory representation-theory homological-algebra






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      share|cite|improve this question











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      asked Aug 7 '15 at 14:29









      Stein ChenStein Chen

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