Max Order of an Isogeny Class of Rational Elliptic Curves is 8?For which composite $N$ does $X_0(N)$ possess a non-cuspidal rational point?About isogeny theorem for elliptic curvesElliptic Curves over Global Function FieldsElliptic curves with arbitrarily large conductorMust the $j$-invariant of an elliptic curve with an isogeny be integral?$j$-invariants of elliptic curves over finite fieldstwists of elliptic curves over finite fieldsDeuring's result on elliptic curves. Any proof reference

Max Order of an Isogeny Class of Rational Elliptic Curves is 8?


For which composite $N$ does $X_0(N)$ possess a non-cuspidal rational point?About isogeny theorem for elliptic curvesElliptic Curves over Global Function FieldsElliptic curves with arbitrarily large conductorMust the $j$-invariant of an elliptic curve with an isogeny be integral?$j$-invariants of elliptic curves over finite fieldstwists of elliptic curves over finite fieldsDeuring's result on elliptic curves. Any proof reference













5












$begingroup$


I am looking for a reference for the proof of the following question following Theorem 5 in Mazur's Rational Isogenies of Prime Degree.



Theorem 5 There is a constant $C$ such that every elliptic curve $E_/mathbbQ$ is isogenous (over $mathbbQ$) to at most $C$ (mutually nonisomorphic) elliptic curves.



"Can one take $C=8$?"



Has this question been proven? And if so, what is a reference to the proof of the result.










share|cite|improve this question









$endgroup$


















    5












    $begingroup$


    I am looking for a reference for the proof of the following question following Theorem 5 in Mazur's Rational Isogenies of Prime Degree.



    Theorem 5 There is a constant $C$ such that every elliptic curve $E_/mathbbQ$ is isogenous (over $mathbbQ$) to at most $C$ (mutually nonisomorphic) elliptic curves.



    "Can one take $C=8$?"



    Has this question been proven? And if so, what is a reference to the proof of the result.










    share|cite|improve this question









    $endgroup$
















      5












      5








      5


      1



      $begingroup$


      I am looking for a reference for the proof of the following question following Theorem 5 in Mazur's Rational Isogenies of Prime Degree.



      Theorem 5 There is a constant $C$ such that every elliptic curve $E_/mathbbQ$ is isogenous (over $mathbbQ$) to at most $C$ (mutually nonisomorphic) elliptic curves.



      "Can one take $C=8$?"



      Has this question been proven? And if so, what is a reference to the proof of the result.










      share|cite|improve this question









      $endgroup$




      I am looking for a reference for the proof of the following question following Theorem 5 in Mazur's Rational Isogenies of Prime Degree.



      Theorem 5 There is a constant $C$ such that every elliptic curve $E_/mathbbQ$ is isogenous (over $mathbbQ$) to at most $C$ (mutually nonisomorphic) elliptic curves.



      "Can one take $C=8$?"



      Has this question been proven? And if so, what is a reference to the proof of the result.







      reference-request elliptic-curves






      share|cite|improve this question













      share|cite|improve this question











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      asked 10 hours ago









      ABarriosABarrios

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          $begingroup$

          M. Kenku, On the number of Q-isomorphism classes of elliptic curves in each Q-isogeny
          class, J. Number Theory 15, 199 (1982):
          It is shown that there are at most eight $Q$-isomorphism classes of elliptic curves in each $Q$-isogeny class.






          share|cite|improve this answer









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          • $begingroup$
            Thank you, Carlo!
            $endgroup$
            – ABarrios
            10 hours ago













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          1 Answer
          1






          active

          oldest

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          oldest

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          active

          oldest

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          8












          $begingroup$

          M. Kenku, On the number of Q-isomorphism classes of elliptic curves in each Q-isogeny
          class, J. Number Theory 15, 199 (1982):
          It is shown that there are at most eight $Q$-isomorphism classes of elliptic curves in each $Q$-isogeny class.






          share|cite|improve this answer









          $endgroup$














          • $begingroup$
            Thank you, Carlo!
            $endgroup$
            – ABarrios
            10 hours ago















          8












          $begingroup$

          M. Kenku, On the number of Q-isomorphism classes of elliptic curves in each Q-isogeny
          class, J. Number Theory 15, 199 (1982):
          It is shown that there are at most eight $Q$-isomorphism classes of elliptic curves in each $Q$-isogeny class.






          share|cite|improve this answer









          $endgroup$














          • $begingroup$
            Thank you, Carlo!
            $endgroup$
            – ABarrios
            10 hours ago













          8












          8








          8





          $begingroup$

          M. Kenku, On the number of Q-isomorphism classes of elliptic curves in each Q-isogeny
          class, J. Number Theory 15, 199 (1982):
          It is shown that there are at most eight $Q$-isomorphism classes of elliptic curves in each $Q$-isogeny class.






          share|cite|improve this answer









          $endgroup$



          M. Kenku, On the number of Q-isomorphism classes of elliptic curves in each Q-isogeny
          class, J. Number Theory 15, 199 (1982):
          It is shown that there are at most eight $Q$-isomorphism classes of elliptic curves in each $Q$-isogeny class.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 10 hours ago









          Carlo BeenakkerCarlo Beenakker

          86k9 gold badges204 silver badges309 bronze badges




          86k9 gold badges204 silver badges309 bronze badges














          • $begingroup$
            Thank you, Carlo!
            $endgroup$
            – ABarrios
            10 hours ago
















          • $begingroup$
            Thank you, Carlo!
            $endgroup$
            – ABarrios
            10 hours ago















          $begingroup$
          Thank you, Carlo!
          $endgroup$
          – ABarrios
          10 hours ago




          $begingroup$
          Thank you, Carlo!
          $endgroup$
          – ABarrios
          10 hours ago

















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