If $M$ is a finitely generated torsion module over a PID which is not a field then $M$ is Artinian.











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If $M$ is a finitely generated torsion module over a PID which is not a field then $M$ is Artinian.



Is contradiction the way to go? How does $M$ being torsion help us? Any hints on how to prove?










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  • @Youngsu Well, $mathbb Z/2mathbb Ztimes mathbb Z/2mathbb Z$ is a counterexample to that... but nevertheless, using the structure theorem is the right way to go...
    – rschwieb
    Nov 22 at 19:48










  • You are absolutely right. I should've said product of those. Thank you for pointing it out.
    – Youngsu
    Nov 22 at 20:24















up vote
1
down vote

favorite












If $M$ is a finitely generated torsion module over a PID which is not a field then $M$ is Artinian.



Is contradiction the way to go? How does $M$ being torsion help us? Any hints on how to prove?










share|cite|improve this question
























  • @Youngsu Well, $mathbb Z/2mathbb Ztimes mathbb Z/2mathbb Z$ is a counterexample to that... but nevertheless, using the structure theorem is the right way to go...
    – rschwieb
    Nov 22 at 19:48










  • You are absolutely right. I should've said product of those. Thank you for pointing it out.
    – Youngsu
    Nov 22 at 20:24













up vote
1
down vote

favorite









up vote
1
down vote

favorite











If $M$ is a finitely generated torsion module over a PID which is not a field then $M$ is Artinian.



Is contradiction the way to go? How does $M$ being torsion help us? Any hints on how to prove?










share|cite|improve this question















If $M$ is a finitely generated torsion module over a PID which is not a field then $M$ is Artinian.



Is contradiction the way to go? How does $M$ being torsion help us? Any hints on how to prove?







linear-algebra






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edited Nov 22 at 20:00









Bernard

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117k637109










asked Nov 22 at 19:15









UserA

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  • @Youngsu Well, $mathbb Z/2mathbb Ztimes mathbb Z/2mathbb Z$ is a counterexample to that... but nevertheless, using the structure theorem is the right way to go...
    – rschwieb
    Nov 22 at 19:48










  • You are absolutely right. I should've said product of those. Thank you for pointing it out.
    – Youngsu
    Nov 22 at 20:24


















  • @Youngsu Well, $mathbb Z/2mathbb Ztimes mathbb Z/2mathbb Z$ is a counterexample to that... but nevertheless, using the structure theorem is the right way to go...
    – rschwieb
    Nov 22 at 19:48










  • You are absolutely right. I should've said product of those. Thank you for pointing it out.
    – Youngsu
    Nov 22 at 20:24
















@Youngsu Well, $mathbb Z/2mathbb Ztimes mathbb Z/2mathbb Z$ is a counterexample to that... but nevertheless, using the structure theorem is the right way to go...
– rschwieb
Nov 22 at 19:48




@Youngsu Well, $mathbb Z/2mathbb Ztimes mathbb Z/2mathbb Z$ is a counterexample to that... but nevertheless, using the structure theorem is the right way to go...
– rschwieb
Nov 22 at 19:48












You are absolutely right. I should've said product of those. Thank you for pointing it out.
– Youngsu
Nov 22 at 20:24




You are absolutely right. I should've said product of those. Thank you for pointing it out.
– Youngsu
Nov 22 at 20:24










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How does M being torsion help us?




I assume you are learning about the fundamental structure theorem on f.g. modules over a PID?



The fact that the module is f.g. and torsion implies $Mcong oplus_{i=1}^n R/(p_i^{e_i})$ for some primes $p_i$ in $R$ and exponents $e_i$.




Any hints on how to prove?




You can check that each of these factors has finite composition length, and so the finite product of the factors has finite composition length.






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    1 Answer
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    up vote
    0
    down vote



    accepted











    How does M being torsion help us?




    I assume you are learning about the fundamental structure theorem on f.g. modules over a PID?



    The fact that the module is f.g. and torsion implies $Mcong oplus_{i=1}^n R/(p_i^{e_i})$ for some primes $p_i$ in $R$ and exponents $e_i$.




    Any hints on how to prove?




    You can check that each of these factors has finite composition length, and so the finite product of the factors has finite composition length.






    share|cite|improve this answer

























      up vote
      0
      down vote



      accepted











      How does M being torsion help us?




      I assume you are learning about the fundamental structure theorem on f.g. modules over a PID?



      The fact that the module is f.g. and torsion implies $Mcong oplus_{i=1}^n R/(p_i^{e_i})$ for some primes $p_i$ in $R$ and exponents $e_i$.




      Any hints on how to prove?




      You can check that each of these factors has finite composition length, and so the finite product of the factors has finite composition length.






      share|cite|improve this answer























        up vote
        0
        down vote



        accepted







        up vote
        0
        down vote



        accepted







        How does M being torsion help us?




        I assume you are learning about the fundamental structure theorem on f.g. modules over a PID?



        The fact that the module is f.g. and torsion implies $Mcong oplus_{i=1}^n R/(p_i^{e_i})$ for some primes $p_i$ in $R$ and exponents $e_i$.




        Any hints on how to prove?




        You can check that each of these factors has finite composition length, and so the finite product of the factors has finite composition length.






        share|cite|improve this answer













        How does M being torsion help us?




        I assume you are learning about the fundamental structure theorem on f.g. modules over a PID?



        The fact that the module is f.g. and torsion implies $Mcong oplus_{i=1}^n R/(p_i^{e_i})$ for some primes $p_i$ in $R$ and exponents $e_i$.




        Any hints on how to prove?




        You can check that each of these factors has finite composition length, and so the finite product of the factors has finite composition length.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 22 at 19:53









        rschwieb

        104k1299241




        104k1299241






























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