Two sided ideals are maximal right ideal iff they are maximal left ideal.












3












$begingroup$


Let $R$ be a ring with unity and $I$ be a two-sided ideal in $R$. Then $I$ is a maximal right ideal if and only if it is a maximal left ideal.



Would anyone give me an idea to prove the statement? Thanks.










share|cite|improve this question









$endgroup$

















    3












    $begingroup$


    Let $R$ be a ring with unity and $I$ be a two-sided ideal in $R$. Then $I$ is a maximal right ideal if and only if it is a maximal left ideal.



    Would anyone give me an idea to prove the statement? Thanks.










    share|cite|improve this question









    $endgroup$















      3












      3








      3


      1



      $begingroup$


      Let $R$ be a ring with unity and $I$ be a two-sided ideal in $R$. Then $I$ is a maximal right ideal if and only if it is a maximal left ideal.



      Would anyone give me an idea to prove the statement? Thanks.










      share|cite|improve this question









      $endgroup$




      Let $R$ be a ring with unity and $I$ be a two-sided ideal in $R$. Then $I$ is a maximal right ideal if and only if it is a maximal left ideal.



      Would anyone give me an idea to prove the statement? Thanks.







      abstract-algebra ring-theory maximal-and-prime-ideals






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 22 at 8:03









      bozcanbozcan

      26518




      26518






















          2 Answers
          2






          active

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          $begingroup$

          Suppose $R/I$ only has trivial right ideals. Then it has only trivial left ideals. For if $x$ is a nonzero member of $R/I$, $x(R/I)=R/I$, and $x$ is right invertible, say by element $y$ similarly $y$ is right invertible, say by element $z$, but it is any easy exercise to prove $x=z$, so $x$ is a unit and $R/I$ is a division ring, and therefore only has trivial left and right ideals.



          By a symmetric argument, the words left and right can be interchanged.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
            $endgroup$
            – bozcan
            Jan 22 at 13:22










          • $begingroup$
            @bozcan Literally everything I wrote is dedicated to proving that.
            $endgroup$
            – rschwieb
            Jan 22 at 13:57












          • $begingroup$
            If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
            $endgroup$
            – rschwieb
            Jan 22 at 14:23



















          0












          $begingroup$

          Hint: Never mind. As rschweib points out in the comments below, this doesn't appear to lead anywhere. The only somewhat dubious advantage to be gained from trying it would appear to be in showing you that you're better off trying something else. Apologies to anyone whom I sent off on a wild goose chase.



          If $ J $ is a one-sided ideal in $ R $ containing $ I $, let $ j $ be an arbirary member of $ J $, and consider the set $ K=left{,x in J mid,j,x,j in J,right} $.




          • Is $ j in K $?

          • Can you determine whether $ K $ is any sort of ideal ?

          • Can you determine what the intersection $ Kcap I $ is ?






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
            $endgroup$
            – rschwieb
            Jan 22 at 10:20










          • $begingroup$
            Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
            $endgroup$
            – lonza leggiera
            Jan 22 at 21:33











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          2 Answers
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          2 Answers
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          $begingroup$

          Suppose $R/I$ only has trivial right ideals. Then it has only trivial left ideals. For if $x$ is a nonzero member of $R/I$, $x(R/I)=R/I$, and $x$ is right invertible, say by element $y$ similarly $y$ is right invertible, say by element $z$, but it is any easy exercise to prove $x=z$, so $x$ is a unit and $R/I$ is a division ring, and therefore only has trivial left and right ideals.



          By a symmetric argument, the words left and right can be interchanged.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
            $endgroup$
            – bozcan
            Jan 22 at 13:22










          • $begingroup$
            @bozcan Literally everything I wrote is dedicated to proving that.
            $endgroup$
            – rschwieb
            Jan 22 at 13:57












          • $begingroup$
            If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
            $endgroup$
            – rschwieb
            Jan 22 at 14:23
















          2












          $begingroup$

          Suppose $R/I$ only has trivial right ideals. Then it has only trivial left ideals. For if $x$ is a nonzero member of $R/I$, $x(R/I)=R/I$, and $x$ is right invertible, say by element $y$ similarly $y$ is right invertible, say by element $z$, but it is any easy exercise to prove $x=z$, so $x$ is a unit and $R/I$ is a division ring, and therefore only has trivial left and right ideals.



          By a symmetric argument, the words left and right can be interchanged.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
            $endgroup$
            – bozcan
            Jan 22 at 13:22










          • $begingroup$
            @bozcan Literally everything I wrote is dedicated to proving that.
            $endgroup$
            – rschwieb
            Jan 22 at 13:57












          • $begingroup$
            If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
            $endgroup$
            – rschwieb
            Jan 22 at 14:23














          2












          2








          2





          $begingroup$

          Suppose $R/I$ only has trivial right ideals. Then it has only trivial left ideals. For if $x$ is a nonzero member of $R/I$, $x(R/I)=R/I$, and $x$ is right invertible, say by element $y$ similarly $y$ is right invertible, say by element $z$, but it is any easy exercise to prove $x=z$, so $x$ is a unit and $R/I$ is a division ring, and therefore only has trivial left and right ideals.



          By a symmetric argument, the words left and right can be interchanged.






          share|cite|improve this answer











          $endgroup$



          Suppose $R/I$ only has trivial right ideals. Then it has only trivial left ideals. For if $x$ is a nonzero member of $R/I$, $x(R/I)=R/I$, and $x$ is right invertible, say by element $y$ similarly $y$ is right invertible, say by element $z$, but it is any easy exercise to prove $x=z$, so $x$ is a unit and $R/I$ is a division ring, and therefore only has trivial left and right ideals.



          By a symmetric argument, the words left and right can be interchanged.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Jan 22 at 13:59

























          answered Jan 22 at 10:06









          rschwiebrschwieb

          107k12102251




          107k12102251












          • $begingroup$
            Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
            $endgroup$
            – bozcan
            Jan 22 at 13:22










          • $begingroup$
            @bozcan Literally everything I wrote is dedicated to proving that.
            $endgroup$
            – rschwieb
            Jan 22 at 13:57












          • $begingroup$
            If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
            $endgroup$
            – rschwieb
            Jan 22 at 14:23


















          • $begingroup$
            Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
            $endgroup$
            – bozcan
            Jan 22 at 13:22










          • $begingroup$
            @bozcan Literally everything I wrote is dedicated to proving that.
            $endgroup$
            – rschwieb
            Jan 22 at 13:57












          • $begingroup$
            If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
            $endgroup$
            – rschwieb
            Jan 22 at 14:23
















          $begingroup$
          Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
          $endgroup$
          – bozcan
          Jan 22 at 13:22




          $begingroup$
          Why is "$R/I$ only has trivial right ideals implies that it has the only trivial left ideals" true?
          $endgroup$
          – bozcan
          Jan 22 at 13:22












          $begingroup$
          @bozcan Literally everything I wrote is dedicated to proving that.
          $endgroup$
          – rschwieb
          Jan 22 at 13:57






          $begingroup$
          @bozcan Literally everything I wrote is dedicated to proving that.
          $endgroup$
          – rschwieb
          Jan 22 at 13:57














          $begingroup$
          If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
          $endgroup$
          – rschwieb
          Jan 22 at 14:23




          $begingroup$
          If there is any further question about that, there are numerous posts to read about it, such as math.stackexchange.com/questions/1151319/…
          $endgroup$
          – rschwieb
          Jan 22 at 14:23











          0












          $begingroup$

          Hint: Never mind. As rschweib points out in the comments below, this doesn't appear to lead anywhere. The only somewhat dubious advantage to be gained from trying it would appear to be in showing you that you're better off trying something else. Apologies to anyone whom I sent off on a wild goose chase.



          If $ J $ is a one-sided ideal in $ R $ containing $ I $, let $ j $ be an arbirary member of $ J $, and consider the set $ K=left{,x in J mid,j,x,j in J,right} $.




          • Is $ j in K $?

          • Can you determine whether $ K $ is any sort of ideal ?

          • Can you determine what the intersection $ Kcap I $ is ?






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
            $endgroup$
            – rschwieb
            Jan 22 at 10:20










          • $begingroup$
            Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
            $endgroup$
            – lonza leggiera
            Jan 22 at 21:33
















          0












          $begingroup$

          Hint: Never mind. As rschweib points out in the comments below, this doesn't appear to lead anywhere. The only somewhat dubious advantage to be gained from trying it would appear to be in showing you that you're better off trying something else. Apologies to anyone whom I sent off on a wild goose chase.



          If $ J $ is a one-sided ideal in $ R $ containing $ I $, let $ j $ be an arbirary member of $ J $, and consider the set $ K=left{,x in J mid,j,x,j in J,right} $.




          • Is $ j in K $?

          • Can you determine whether $ K $ is any sort of ideal ?

          • Can you determine what the intersection $ Kcap I $ is ?






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
            $endgroup$
            – rschwieb
            Jan 22 at 10:20










          • $begingroup$
            Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
            $endgroup$
            – lonza leggiera
            Jan 22 at 21:33














          0












          0








          0





          $begingroup$

          Hint: Never mind. As rschweib points out in the comments below, this doesn't appear to lead anywhere. The only somewhat dubious advantage to be gained from trying it would appear to be in showing you that you're better off trying something else. Apologies to anyone whom I sent off on a wild goose chase.



          If $ J $ is a one-sided ideal in $ R $ containing $ I $, let $ j $ be an arbirary member of $ J $, and consider the set $ K=left{,x in J mid,j,x,j in J,right} $.




          • Is $ j in K $?

          • Can you determine whether $ K $ is any sort of ideal ?

          • Can you determine what the intersection $ Kcap I $ is ?






          share|cite|improve this answer











          $endgroup$



          Hint: Never mind. As rschweib points out in the comments below, this doesn't appear to lead anywhere. The only somewhat dubious advantage to be gained from trying it would appear to be in showing you that you're better off trying something else. Apologies to anyone whom I sent off on a wild goose chase.



          If $ J $ is a one-sided ideal in $ R $ containing $ I $, let $ j $ be an arbirary member of $ J $, and consider the set $ K=left{,x in J mid,j,x,j in J,right} $.




          • Is $ j in K $?

          • Can you determine whether $ K $ is any sort of ideal ?

          • Can you determine what the intersection $ Kcap I $ is ?







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Jan 23 at 20:47

























          answered Jan 22 at 9:12









          lonza leggieralonza leggiera

          97728




          97728












          • $begingroup$
            Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
            $endgroup$
            – rschwieb
            Jan 22 at 10:20










          • $begingroup$
            Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
            $endgroup$
            – lonza leggiera
            Jan 22 at 21:33


















          • $begingroup$
            Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
            $endgroup$
            – rschwieb
            Jan 22 at 10:20










          • $begingroup$
            Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
            $endgroup$
            – lonza leggiera
            Jan 22 at 21:33
















          $begingroup$
          Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
          $endgroup$
          – rschwieb
          Jan 22 at 10:20




          $begingroup$
          Is there a typo? Because as written, $J=K$ and the hint doesn’t seem to go anywhere.
          $endgroup$
          – rschwieb
          Jan 22 at 10:20












          $begingroup$
          Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
          $endgroup$
          – lonza leggiera
          Jan 22 at 21:33




          $begingroup$
          Not a typo. A blunder, rather, in my supposed proof that $ K $ had to be two-sided. The idea was to find a description of $ J $ which it was not too difficult to show to be two-sided. If such a thing is possible, it appears to be much more difficult than I had initially hoped, and $ K $ certainly doesn't qualify.
          $endgroup$
          – lonza leggiera
          Jan 22 at 21:33


















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