What is a Weil-Deligne representation?












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Can anyone explain (or give reference) Weil-Deligne representations, and how they are linked with Galois representations of p-adic field (on l-adic vector spaces or else) ?










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    4












    $begingroup$


    Can anyone explain (or give reference) Weil-Deligne representations, and how they are linked with Galois representations of p-adic field (on l-adic vector spaces or else) ?










    share|cite|improve this question









    $endgroup$















      4












      4








      4


      5



      $begingroup$


      Can anyone explain (or give reference) Weil-Deligne representations, and how they are linked with Galois representations of p-adic field (on l-adic vector spaces or else) ?










      share|cite|improve this question









      $endgroup$




      Can anyone explain (or give reference) Weil-Deligne representations, and how they are linked with Galois representations of p-adic field (on l-adic vector spaces or else) ?







      reference-request representation-theory galois-theory






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      asked Sep 1 '11 at 21:48









      user10676user10676

      6,29021737




      6,29021737






















          1 Answer
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          $begingroup$

          The canonical reference is Tate's "Number Theoretic Background" in the Corvallis volume. He discusses the Weil-Deligne group in Section 4. Here is a brief description:



          Fix a local field $K$ with perfect residue field of characteristic $pneqell$, and let $W_K$ be the Weil group of $K$ (this is $phi^{-1}(mathbb{Z})$ where $phi:G_Krightarrowhat{mathbb{Z}}$ is the unramified quotient). A Weil-Deligne representation is a pair



          $(V,N)$



          where $V$ is a char. $0$ representation of $W_K$ on a discrete vector space and $N:Vrightarrow V(-1)$ is a morphism of representations. One important fact is that the category of $ell$-adic representations of $G_K$ embeds fully faithfully into the category of Weil-Deligne representations.



          Anyway, to get the full story, you should probably read Tate's article.



          EDIT: Another nice reference is Chapter 1 of (the current draft of) a book by Fontaine and Ouyang.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
            $endgroup$
            – Matt E
            Sep 2 '11 at 1:25










          • $begingroup$
            Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
            $endgroup$
            – Kevin Ventullo
            Sep 2 '11 at 2:44











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          1 Answer
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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          6












          $begingroup$

          The canonical reference is Tate's "Number Theoretic Background" in the Corvallis volume. He discusses the Weil-Deligne group in Section 4. Here is a brief description:



          Fix a local field $K$ with perfect residue field of characteristic $pneqell$, and let $W_K$ be the Weil group of $K$ (this is $phi^{-1}(mathbb{Z})$ where $phi:G_Krightarrowhat{mathbb{Z}}$ is the unramified quotient). A Weil-Deligne representation is a pair



          $(V,N)$



          where $V$ is a char. $0$ representation of $W_K$ on a discrete vector space and $N:Vrightarrow V(-1)$ is a morphism of representations. One important fact is that the category of $ell$-adic representations of $G_K$ embeds fully faithfully into the category of Weil-Deligne representations.



          Anyway, to get the full story, you should probably read Tate's article.



          EDIT: Another nice reference is Chapter 1 of (the current draft of) a book by Fontaine and Ouyang.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
            $endgroup$
            – Matt E
            Sep 2 '11 at 1:25










          • $begingroup$
            Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
            $endgroup$
            – Kevin Ventullo
            Sep 2 '11 at 2:44
















          6












          $begingroup$

          The canonical reference is Tate's "Number Theoretic Background" in the Corvallis volume. He discusses the Weil-Deligne group in Section 4. Here is a brief description:



          Fix a local field $K$ with perfect residue field of characteristic $pneqell$, and let $W_K$ be the Weil group of $K$ (this is $phi^{-1}(mathbb{Z})$ where $phi:G_Krightarrowhat{mathbb{Z}}$ is the unramified quotient). A Weil-Deligne representation is a pair



          $(V,N)$



          where $V$ is a char. $0$ representation of $W_K$ on a discrete vector space and $N:Vrightarrow V(-1)$ is a morphism of representations. One important fact is that the category of $ell$-adic representations of $G_K$ embeds fully faithfully into the category of Weil-Deligne representations.



          Anyway, to get the full story, you should probably read Tate's article.



          EDIT: Another nice reference is Chapter 1 of (the current draft of) a book by Fontaine and Ouyang.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
            $endgroup$
            – Matt E
            Sep 2 '11 at 1:25










          • $begingroup$
            Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
            $endgroup$
            – Kevin Ventullo
            Sep 2 '11 at 2:44














          6












          6








          6





          $begingroup$

          The canonical reference is Tate's "Number Theoretic Background" in the Corvallis volume. He discusses the Weil-Deligne group in Section 4. Here is a brief description:



          Fix a local field $K$ with perfect residue field of characteristic $pneqell$, and let $W_K$ be the Weil group of $K$ (this is $phi^{-1}(mathbb{Z})$ where $phi:G_Krightarrowhat{mathbb{Z}}$ is the unramified quotient). A Weil-Deligne representation is a pair



          $(V,N)$



          where $V$ is a char. $0$ representation of $W_K$ on a discrete vector space and $N:Vrightarrow V(-1)$ is a morphism of representations. One important fact is that the category of $ell$-adic representations of $G_K$ embeds fully faithfully into the category of Weil-Deligne representations.



          Anyway, to get the full story, you should probably read Tate's article.



          EDIT: Another nice reference is Chapter 1 of (the current draft of) a book by Fontaine and Ouyang.






          share|cite|improve this answer











          $endgroup$



          The canonical reference is Tate's "Number Theoretic Background" in the Corvallis volume. He discusses the Weil-Deligne group in Section 4. Here is a brief description:



          Fix a local field $K$ with perfect residue field of characteristic $pneqell$, and let $W_K$ be the Weil group of $K$ (this is $phi^{-1}(mathbb{Z})$ where $phi:G_Krightarrowhat{mathbb{Z}}$ is the unramified quotient). A Weil-Deligne representation is a pair



          $(V,N)$



          where $V$ is a char. $0$ representation of $W_K$ on a discrete vector space and $N:Vrightarrow V(-1)$ is a morphism of representations. One important fact is that the category of $ell$-adic representations of $G_K$ embeds fully faithfully into the category of Weil-Deligne representations.



          Anyway, to get the full story, you should probably read Tate's article.



          EDIT: Another nice reference is Chapter 1 of (the current draft of) a book by Fontaine and Ouyang.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 30 '18 at 3:34

























          answered Sep 1 '11 at 22:50









          Kevin VentulloKevin Ventullo

          2,16411422




          2,16411422












          • $begingroup$
            Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
            $endgroup$
            – Matt E
            Sep 2 '11 at 1:25










          • $begingroup$
            Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
            $endgroup$
            – Kevin Ventullo
            Sep 2 '11 at 2:44


















          • $begingroup$
            Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
            $endgroup$
            – Matt E
            Sep 2 '11 at 1:25










          • $begingroup$
            Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
            $endgroup$
            – Kevin Ventullo
            Sep 2 '11 at 2:44
















          $begingroup$
          Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
          $endgroup$
          – Matt E
          Sep 2 '11 at 1:25




          $begingroup$
          Dear Kevin, Note that if $ell neq p$, then every $ell$-adic representation of $G_K$ is "potentially semi-stable", and so corresponds to a Weil--Deligne representation. Regards,
          $endgroup$
          – Matt E
          Sep 2 '11 at 1:25












          $begingroup$
          Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
          $endgroup$
          – Kevin Ventullo
          Sep 2 '11 at 2:44




          $begingroup$
          Dear Matt, Thank you for your comment. I started out trying to write about an arbitrary complete DVF but changed my mind and ended up with some garbage. I have edited to reflect your remark.
          $endgroup$
          – Kevin Ventullo
          Sep 2 '11 at 2:44


















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