The krull dimension of $BbbZ$ and artinian rings The Next CEO of Stack OverflowWhy are Artinian rings of Krull dimension 0?Krull DimensionWhy do Artinian rings have dimension 0 and not 1?Artinian rings have finite lengthKrull Dimension of Direct Limits of Zero-Dimensional RingsPreservation of Krull dimension under inverse limitlocal-global rings and its examplesWhy is this a corollary of [Noetherian of Krull dimension 0 iff Artinian]?Why intermediate rings of Krull have dimension $leq 1$?On “homogeneous” height and “homogeneous” Krull-dimension?

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The krull dimension of $BbbZ$ and artinian rings



The Next CEO of Stack OverflowWhy are Artinian rings of Krull dimension 0?Krull DimensionWhy do Artinian rings have dimension 0 and not 1?Artinian rings have finite lengthKrull Dimension of Direct Limits of Zero-Dimensional RingsPreservation of Krull dimension under inverse limitlocal-global rings and its examplesWhy is this a corollary of [Noetherian of Krull dimension 0 iff Artinian]?Why intermediate rings of Krull have dimension $leq 1$?On “homogeneous” height and “homogeneous” Krull-dimension?










1












$begingroup$


On page thirty of Matsumura, it says that $BbbZ$ has krull dimension 1 because every prime ideal is maximal. I understand this because for any prime p you have $0 subset p$.



However, for artinian rings, it says that the dimesion is zero because every prime ideal is maximal. This is where I'm confused. As above, we have $0 subset p$ for any nonzero prime ideal...but then why isn't he dimension 1?










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    "...because every nonzero prime ideal is maximal..."
    $endgroup$
    – Orest Bucicovschi
    Oct 15 '14 at 15:24






  • 1




    $begingroup$
    Note that $mathbbZ$ is not artinian. See Thomas Andrews' answer below.
    $endgroup$
    – anomaly
    Oct 15 '14 at 15:37















1












$begingroup$


On page thirty of Matsumura, it says that $BbbZ$ has krull dimension 1 because every prime ideal is maximal. I understand this because for any prime p you have $0 subset p$.



However, for artinian rings, it says that the dimesion is zero because every prime ideal is maximal. This is where I'm confused. As above, we have $0 subset p$ for any nonzero prime ideal...but then why isn't he dimension 1?










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    "...because every nonzero prime ideal is maximal..."
    $endgroup$
    – Orest Bucicovschi
    Oct 15 '14 at 15:24






  • 1




    $begingroup$
    Note that $mathbbZ$ is not artinian. See Thomas Andrews' answer below.
    $endgroup$
    – anomaly
    Oct 15 '14 at 15:37













1












1








1


1



$begingroup$


On page thirty of Matsumura, it says that $BbbZ$ has krull dimension 1 because every prime ideal is maximal. I understand this because for any prime p you have $0 subset p$.



However, for artinian rings, it says that the dimesion is zero because every prime ideal is maximal. This is where I'm confused. As above, we have $0 subset p$ for any nonzero prime ideal...but then why isn't he dimension 1?










share|cite|improve this question









$endgroup$




On page thirty of Matsumura, it says that $BbbZ$ has krull dimension 1 because every prime ideal is maximal. I understand this because for any prime p you have $0 subset p$.



However, for artinian rings, it says that the dimesion is zero because every prime ideal is maximal. This is where I'm confused. As above, we have $0 subset p$ for any nonzero prime ideal...but then why isn't he dimension 1?







abstract-algebra ring-theory commutative-algebra






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Oct 15 '14 at 15:07









ArtusArtus

452612




452612







  • 1




    $begingroup$
    "...because every nonzero prime ideal is maximal..."
    $endgroup$
    – Orest Bucicovschi
    Oct 15 '14 at 15:24






  • 1




    $begingroup$
    Note that $mathbbZ$ is not artinian. See Thomas Andrews' answer below.
    $endgroup$
    – anomaly
    Oct 15 '14 at 15:37












  • 1




    $begingroup$
    "...because every nonzero prime ideal is maximal..."
    $endgroup$
    – Orest Bucicovschi
    Oct 15 '14 at 15:24






  • 1




    $begingroup$
    Note that $mathbbZ$ is not artinian. See Thomas Andrews' answer below.
    $endgroup$
    – anomaly
    Oct 15 '14 at 15:37







1




1




$begingroup$
"...because every nonzero prime ideal is maximal..."
$endgroup$
– Orest Bucicovschi
Oct 15 '14 at 15:24




$begingroup$
"...because every nonzero prime ideal is maximal..."
$endgroup$
– Orest Bucicovschi
Oct 15 '14 at 15:24




1




1




$begingroup$
Note that $mathbbZ$ is not artinian. See Thomas Andrews' answer below.
$endgroup$
– anomaly
Oct 15 '14 at 15:37




$begingroup$
Note that $mathbbZ$ is not artinian. See Thomas Andrews' answer below.
$endgroup$
– anomaly
Oct 15 '14 at 15:37










3 Answers
3






active

oldest

votes


















2












$begingroup$

Hint: Is $0$ a prime ideal in all rings? If $0$ is a prime ideal, and it is maximal, is there any other prime ideal?






share|cite|improve this answer









$endgroup$




















    3












    $begingroup$

    Every prime ideal $mathfrak p$ in an Artinian ring $R$ is maximal. To see this, let $x in R / mathfrak p$, $x ne 0$. Consider the descending chain $(x) supset (x^2) supset cdots$ to show that $x$ is invertible.



    On the other hand, $mathbb Z$ is a principal ideal domain. Every nonzero prime ideal in a PID is maximal. The word "nonzero" here is the crucial difference.



    It follows that $mathbb Z$ has dimension $1$ whereas Artinian rings have dimension $0$.






    share|cite|improve this answer









    $endgroup$




















      0












      $begingroup$

      Fields are obviously artinian, as they have only trivial ideals.



      Suppose $R$ is an artinian ring which is not artinian and let $xin R$ an element which is neither $0$ nor invertible. Consider the descending chain of ideals
      $$
      (x)supset(x^2)supsetcdotssupset(x^n)supset(x^n+1)supset cdots.
      $$

      The chain stabilizes by assumption.



      If $(x^n)=(0)$ eventually, $x$ is a nilpotent element.



      If $(x^n)=(x^n+1)neq(0)$ eventually, we can write $x^n=yx^n+1$ for some $yin R$ from which we get $x^n(xy-1)=0$, i.e. $x$ is a $0$-divisor.



      In either case $R$ is not a domain, hence the ideal $(0)$ isn't prime.






      share|cite|improve this answer









      $endgroup$













        Your Answer





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        3 Answers
        3






        active

        oldest

        votes








        3 Answers
        3






        active

        oldest

        votes









        active

        oldest

        votes






        active

        oldest

        votes









        2












        $begingroup$

        Hint: Is $0$ a prime ideal in all rings? If $0$ is a prime ideal, and it is maximal, is there any other prime ideal?






        share|cite|improve this answer









        $endgroup$

















          2












          $begingroup$

          Hint: Is $0$ a prime ideal in all rings? If $0$ is a prime ideal, and it is maximal, is there any other prime ideal?






          share|cite|improve this answer









          $endgroup$















            2












            2








            2





            $begingroup$

            Hint: Is $0$ a prime ideal in all rings? If $0$ is a prime ideal, and it is maximal, is there any other prime ideal?






            share|cite|improve this answer









            $endgroup$



            Hint: Is $0$ a prime ideal in all rings? If $0$ is a prime ideal, and it is maximal, is there any other prime ideal?







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered Oct 15 '14 at 15:13









            Thomas AndrewsThomas Andrews

            130k12147298




            130k12147298





















                3












                $begingroup$

                Every prime ideal $mathfrak p$ in an Artinian ring $R$ is maximal. To see this, let $x in R / mathfrak p$, $x ne 0$. Consider the descending chain $(x) supset (x^2) supset cdots$ to show that $x$ is invertible.



                On the other hand, $mathbb Z$ is a principal ideal domain. Every nonzero prime ideal in a PID is maximal. The word "nonzero" here is the crucial difference.



                It follows that $mathbb Z$ has dimension $1$ whereas Artinian rings have dimension $0$.






                share|cite|improve this answer









                $endgroup$

















                  3












                  $begingroup$

                  Every prime ideal $mathfrak p$ in an Artinian ring $R$ is maximal. To see this, let $x in R / mathfrak p$, $x ne 0$. Consider the descending chain $(x) supset (x^2) supset cdots$ to show that $x$ is invertible.



                  On the other hand, $mathbb Z$ is a principal ideal domain. Every nonzero prime ideal in a PID is maximal. The word "nonzero" here is the crucial difference.



                  It follows that $mathbb Z$ has dimension $1$ whereas Artinian rings have dimension $0$.






                  share|cite|improve this answer









                  $endgroup$















                    3












                    3








                    3





                    $begingroup$

                    Every prime ideal $mathfrak p$ in an Artinian ring $R$ is maximal. To see this, let $x in R / mathfrak p$, $x ne 0$. Consider the descending chain $(x) supset (x^2) supset cdots$ to show that $x$ is invertible.



                    On the other hand, $mathbb Z$ is a principal ideal domain. Every nonzero prime ideal in a PID is maximal. The word "nonzero" here is the crucial difference.



                    It follows that $mathbb Z$ has dimension $1$ whereas Artinian rings have dimension $0$.






                    share|cite|improve this answer









                    $endgroup$



                    Every prime ideal $mathfrak p$ in an Artinian ring $R$ is maximal. To see this, let $x in R / mathfrak p$, $x ne 0$. Consider the descending chain $(x) supset (x^2) supset cdots$ to show that $x$ is invertible.



                    On the other hand, $mathbb Z$ is a principal ideal domain. Every nonzero prime ideal in a PID is maximal. The word "nonzero" here is the crucial difference.



                    It follows that $mathbb Z$ has dimension $1$ whereas Artinian rings have dimension $0$.







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered Oct 15 '14 at 17:13









                    Ayman HouriehAyman Hourieh

                    31.3k466119




                    31.3k466119





















                        0












                        $begingroup$

                        Fields are obviously artinian, as they have only trivial ideals.



                        Suppose $R$ is an artinian ring which is not artinian and let $xin R$ an element which is neither $0$ nor invertible. Consider the descending chain of ideals
                        $$
                        (x)supset(x^2)supsetcdotssupset(x^n)supset(x^n+1)supset cdots.
                        $$

                        The chain stabilizes by assumption.



                        If $(x^n)=(0)$ eventually, $x$ is a nilpotent element.



                        If $(x^n)=(x^n+1)neq(0)$ eventually, we can write $x^n=yx^n+1$ for some $yin R$ from which we get $x^n(xy-1)=0$, i.e. $x$ is a $0$-divisor.



                        In either case $R$ is not a domain, hence the ideal $(0)$ isn't prime.






                        share|cite|improve this answer









                        $endgroup$

















                          0












                          $begingroup$

                          Fields are obviously artinian, as they have only trivial ideals.



                          Suppose $R$ is an artinian ring which is not artinian and let $xin R$ an element which is neither $0$ nor invertible. Consider the descending chain of ideals
                          $$
                          (x)supset(x^2)supsetcdotssupset(x^n)supset(x^n+1)supset cdots.
                          $$

                          The chain stabilizes by assumption.



                          If $(x^n)=(0)$ eventually, $x$ is a nilpotent element.



                          If $(x^n)=(x^n+1)neq(0)$ eventually, we can write $x^n=yx^n+1$ for some $yin R$ from which we get $x^n(xy-1)=0$, i.e. $x$ is a $0$-divisor.



                          In either case $R$ is not a domain, hence the ideal $(0)$ isn't prime.






                          share|cite|improve this answer









                          $endgroup$















                            0












                            0








                            0





                            $begingroup$

                            Fields are obviously artinian, as they have only trivial ideals.



                            Suppose $R$ is an artinian ring which is not artinian and let $xin R$ an element which is neither $0$ nor invertible. Consider the descending chain of ideals
                            $$
                            (x)supset(x^2)supsetcdotssupset(x^n)supset(x^n+1)supset cdots.
                            $$

                            The chain stabilizes by assumption.



                            If $(x^n)=(0)$ eventually, $x$ is a nilpotent element.



                            If $(x^n)=(x^n+1)neq(0)$ eventually, we can write $x^n=yx^n+1$ for some $yin R$ from which we get $x^n(xy-1)=0$, i.e. $x$ is a $0$-divisor.



                            In either case $R$ is not a domain, hence the ideal $(0)$ isn't prime.






                            share|cite|improve this answer









                            $endgroup$



                            Fields are obviously artinian, as they have only trivial ideals.



                            Suppose $R$ is an artinian ring which is not artinian and let $xin R$ an element which is neither $0$ nor invertible. Consider the descending chain of ideals
                            $$
                            (x)supset(x^2)supsetcdotssupset(x^n)supset(x^n+1)supset cdots.
                            $$

                            The chain stabilizes by assumption.



                            If $(x^n)=(0)$ eventually, $x$ is a nilpotent element.



                            If $(x^n)=(x^n+1)neq(0)$ eventually, we can write $x^n=yx^n+1$ for some $yin R$ from which we get $x^n(xy-1)=0$, i.e. $x$ is a $0$-divisor.



                            In either case $R$ is not a domain, hence the ideal $(0)$ isn't prime.







                            share|cite|improve this answer












                            share|cite|improve this answer



                            share|cite|improve this answer










                            answered Mar 19 at 9:10









                            Andrea MoriAndrea Mori

                            20.1k13466




                            20.1k13466



























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