Abelian group of prime exponent $p$ is $mathbb{F}_p$-vector space?











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In reading about group cohomological, I came across the following in a statement of a lemma. "Let $p$ be a prime, and let $A$ be an abelian group of exponent dividing $p$..."



Is this just a roundabout way of saying that $A$ is an $mathbb{F}_p$-vector space? At least in the case where $A$ is finite or finitely generated, this seems obvious from the classification of finitely generated abelian groups. According to Exponent of a Group, I am correct, but perhaps I am missing an assumption there.



Are there abelian groups of exponent $p$ that are not $mathbb{F}_p$-vector spaces?










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    up vote
    1
    down vote

    favorite












    In reading about group cohomological, I came across the following in a statement of a lemma. "Let $p$ be a prime, and let $A$ be an abelian group of exponent dividing $p$..."



    Is this just a roundabout way of saying that $A$ is an $mathbb{F}_p$-vector space? At least in the case where $A$ is finite or finitely generated, this seems obvious from the classification of finitely generated abelian groups. According to Exponent of a Group, I am correct, but perhaps I am missing an assumption there.



    Are there abelian groups of exponent $p$ that are not $mathbb{F}_p$-vector spaces?










    share|cite|improve this question
























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      In reading about group cohomological, I came across the following in a statement of a lemma. "Let $p$ be a prime, and let $A$ be an abelian group of exponent dividing $p$..."



      Is this just a roundabout way of saying that $A$ is an $mathbb{F}_p$-vector space? At least in the case where $A$ is finite or finitely generated, this seems obvious from the classification of finitely generated abelian groups. According to Exponent of a Group, I am correct, but perhaps I am missing an assumption there.



      Are there abelian groups of exponent $p$ that are not $mathbb{F}_p$-vector spaces?










      share|cite|improve this question













      In reading about group cohomological, I came across the following in a statement of a lemma. "Let $p$ be a prime, and let $A$ be an abelian group of exponent dividing $p$..."



      Is this just a roundabout way of saying that $A$ is an $mathbb{F}_p$-vector space? At least in the case where $A$ is finite or finitely generated, this seems obvious from the classification of finitely generated abelian groups. According to Exponent of a Group, I am correct, but perhaps I am missing an assumption there.



      Are there abelian groups of exponent $p$ that are not $mathbb{F}_p$-vector spaces?







      abelian-groups positive-characteristic






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      asked Nov 20 at 3:27









      Joshua Ruiter

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          Yes, this is the same thing as an $mathbb{F}_p$-vector space. There is no need to think about any classification theorem; this is instead just immediate from the definitions. Since $mathbb{F}_p$ is the quotient ring $mathbb{Z}/(p)$, an $mathbb{F}_p$-module is the same thing as a $mathbb{Z}$-module in which every element is annihilated by $p$. But a $mathbb{Z}$-module is the same thing as an abelian group, and every element of an abelian group is annihilated by $p$ iff the exponent of the group divides $p$.






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            Yes, this is the same thing as an $mathbb{F}_p$-vector space. There is no need to think about any classification theorem; this is instead just immediate from the definitions. Since $mathbb{F}_p$ is the quotient ring $mathbb{Z}/(p)$, an $mathbb{F}_p$-module is the same thing as a $mathbb{Z}$-module in which every element is annihilated by $p$. But a $mathbb{Z}$-module is the same thing as an abelian group, and every element of an abelian group is annihilated by $p$ iff the exponent of the group divides $p$.






            share|cite|improve this answer

























              up vote
              2
              down vote



              accepted










              Yes, this is the same thing as an $mathbb{F}_p$-vector space. There is no need to think about any classification theorem; this is instead just immediate from the definitions. Since $mathbb{F}_p$ is the quotient ring $mathbb{Z}/(p)$, an $mathbb{F}_p$-module is the same thing as a $mathbb{Z}$-module in which every element is annihilated by $p$. But a $mathbb{Z}$-module is the same thing as an abelian group, and every element of an abelian group is annihilated by $p$ iff the exponent of the group divides $p$.






              share|cite|improve this answer























                up vote
                2
                down vote



                accepted







                up vote
                2
                down vote



                accepted






                Yes, this is the same thing as an $mathbb{F}_p$-vector space. There is no need to think about any classification theorem; this is instead just immediate from the definitions. Since $mathbb{F}_p$ is the quotient ring $mathbb{Z}/(p)$, an $mathbb{F}_p$-module is the same thing as a $mathbb{Z}$-module in which every element is annihilated by $p$. But a $mathbb{Z}$-module is the same thing as an abelian group, and every element of an abelian group is annihilated by $p$ iff the exponent of the group divides $p$.






                share|cite|improve this answer












                Yes, this is the same thing as an $mathbb{F}_p$-vector space. There is no need to think about any classification theorem; this is instead just immediate from the definitions. Since $mathbb{F}_p$ is the quotient ring $mathbb{Z}/(p)$, an $mathbb{F}_p$-module is the same thing as a $mathbb{Z}$-module in which every element is annihilated by $p$. But a $mathbb{Z}$-module is the same thing as an abelian group, and every element of an abelian group is annihilated by $p$ iff the exponent of the group divides $p$.







                share|cite|improve this answer












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                answered Nov 20 at 3:42









                Eric Wofsey

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