Computing contractions of ideals in Macaulay2












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Does Macaulay2 compute contractions of ideals under ring homomorphisms. Specifically, if $Rsubseteq S$ is a ring extension (say polynomial rings over $mathbb{Q}$ which can be specified in M2) and $I$ is an ideal in $S$ given by generators, is there a command to compute $Icap R$?



EDIT: The eliminate command is supposed to do what I want, except when I use it the output is an ideal in the original ring.










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    6












    $begingroup$


    Does Macaulay2 compute contractions of ideals under ring homomorphisms. Specifically, if $Rsubseteq S$ is a ring extension (say polynomial rings over $mathbb{Q}$ which can be specified in M2) and $I$ is an ideal in $S$ given by generators, is there a command to compute $Icap R$?



    EDIT: The eliminate command is supposed to do what I want, except when I use it the output is an ideal in the original ring.










    share|cite|improve this question











    $endgroup$















      6












      6








      6


      0



      $begingroup$


      Does Macaulay2 compute contractions of ideals under ring homomorphisms. Specifically, if $Rsubseteq S$ is a ring extension (say polynomial rings over $mathbb{Q}$ which can be specified in M2) and $I$ is an ideal in $S$ given by generators, is there a command to compute $Icap R$?



      EDIT: The eliminate command is supposed to do what I want, except when I use it the output is an ideal in the original ring.










      share|cite|improve this question











      $endgroup$




      Does Macaulay2 compute contractions of ideals under ring homomorphisms. Specifically, if $Rsubseteq S$ is a ring extension (say polynomial rings over $mathbb{Q}$ which can be specified in M2) and $I$ is an ideal in $S$ given by generators, is there a command to compute $Icap R$?



      EDIT: The eliminate command is supposed to do what I want, except when I use it the output is an ideal in the original ring.







      abstract-algebra commutative-algebra math-software symbolic-computation macaulay2






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      edited Dec 8 '18 at 14:05









      Rodrigo de Azevedo

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      asked Jan 4 '12 at 18:02









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          You could set f=map(S/I,R) and obtain the intersection as ker(f).






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            Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
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            – t.b.
            Jan 7 '12 at 17:29












          • $begingroup$
            actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
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            – Marc Olschok
            Jan 9 '12 at 20:47












          • $begingroup$
            The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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            I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
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            – t.b.
            Jan 10 '12 at 10:45





















          0












          $begingroup$

          More generally there is also the function preimage which takes $f$ a function from $R$ to $S$ and $I$ an ideal in $S$ and outputs $I^c$ in $R$ http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6/share/doc/Macaulay2/Macaulay2Doc/html/_preimage.html






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            2 Answers
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            2 Answers
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            active

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            0












            $begingroup$

            You could set f=map(S/I,R) and obtain the intersection as ker(f).






            share|cite|improve this answer









            $endgroup$









            • 1




              $begingroup$
              Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
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              – t.b.
              Jan 7 '12 at 17:29












            • $begingroup$
              actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
              $endgroup$
              – Marc Olschok
              Jan 9 '12 at 20:47












            • $begingroup$
              The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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              – t.b.
              Jan 9 '12 at 20:55












            • $begingroup$
              I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
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              – t.b.
              Jan 10 '12 at 10:45


















            0












            $begingroup$

            You could set f=map(S/I,R) and obtain the intersection as ker(f).






            share|cite|improve this answer









            $endgroup$









            • 1




              $begingroup$
              Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
              $endgroup$
              – t.b.
              Jan 7 '12 at 17:29












            • $begingroup$
              actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
              $endgroup$
              – Marc Olschok
              Jan 9 '12 at 20:47












            • $begingroup$
              The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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              – t.b.
              Jan 9 '12 at 20:55












            • $begingroup$
              I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
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              – t.b.
              Jan 10 '12 at 10:45
















            0












            0








            0





            $begingroup$

            You could set f=map(S/I,R) and obtain the intersection as ker(f).






            share|cite|improve this answer









            $endgroup$



            You could set f=map(S/I,R) and obtain the intersection as ker(f).







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered Jan 7 '12 at 16:35









            Marc OlschokMarc Olschok

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            1,12666








            • 1




              $begingroup$
              Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
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              – t.b.
              Jan 7 '12 at 17:29












            • $begingroup$
              actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
              $endgroup$
              – Marc Olschok
              Jan 9 '12 at 20:47












            • $begingroup$
              The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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              – t.b.
              Jan 9 '12 at 20:55












            • $begingroup$
              I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
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              – t.b.
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            • 1




              $begingroup$
              Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
              $endgroup$
              – t.b.
              Jan 7 '12 at 17:29












            • $begingroup$
              actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
              $endgroup$
              – Marc Olschok
              Jan 9 '12 at 20:47












            • $begingroup$
              The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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              – t.b.
              Jan 9 '12 at 20:55












            • $begingroup$
              I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
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              – t.b.
              Jan 10 '12 at 10:45










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            $begingroup$
            Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
            $endgroup$
            – t.b.
            Jan 7 '12 at 17:29






            $begingroup$
            Marc, if intend to continue to contribute regularly to this site, it would be nice if you registered your account (it takes only a minute to do that). This way it would be easier for the software to recognize you (and it's the third time I ask the moderators to merge your older account into a newly created one).
            $endgroup$
            – t.b.
            Jan 7 '12 at 17:29














            $begingroup$
            actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
            $endgroup$
            – Marc Olschok
            Jan 9 '12 at 20:47






            $begingroup$
            actually I want to register (I meanwhile have an OPen ID), but cannot find the link for this. I also registerd with the same name but a newer account.
            $endgroup$
            – Marc Olschok
            Jan 9 '12 at 20:47














            $begingroup$
            The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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            – t.b.
            Jan 9 '12 at 20:55






            $begingroup$
            The account you used for writing your last comment is registered. If you want to add other registration information like Open ID, then you should go to your user profile here (this page is accessible by clicking on your name at the top middle at the top of each page). Adding registration information can be done here (this page can be reached by clicking "my logins" on the user profile page).
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            – t.b.
            Jan 9 '12 at 20:55














            $begingroup$
            I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
            $endgroup$
            – t.b.
            Jan 10 '12 at 10:45






            $begingroup$
            I've located the following earlier accounts of yours: math.stackexchange.com/users/15341, math.stackexchange.com/users/15825, math.stackexchange.com/users/16790, math.stackexchange.com/users/19253, math.stackexchange.com/users/20407, math.stackexchange.com/users/21246. If you want to merge them into your current registered account, please flag for moderator attention (at the bottom of your answer you have the "flag" link. Click it and explain the situation briefly in the "other" field.)
            $endgroup$
            – t.b.
            Jan 10 '12 at 10:45













            0












            $begingroup$

            More generally there is also the function preimage which takes $f$ a function from $R$ to $S$ and $I$ an ideal in $S$ and outputs $I^c$ in $R$ http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6/share/doc/Macaulay2/Macaulay2Doc/html/_preimage.html






            share|cite|improve this answer









            $endgroup$


















              0












              $begingroup$

              More generally there is also the function preimage which takes $f$ a function from $R$ to $S$ and $I$ an ideal in $S$ and outputs $I^c$ in $R$ http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6/share/doc/Macaulay2/Macaulay2Doc/html/_preimage.html






              share|cite|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                More generally there is also the function preimage which takes $f$ a function from $R$ to $S$ and $I$ an ideal in $S$ and outputs $I^c$ in $R$ http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6/share/doc/Macaulay2/Macaulay2Doc/html/_preimage.html






                share|cite|improve this answer









                $endgroup$



                More generally there is also the function preimage which takes $f$ a function from $R$ to $S$ and $I$ an ideal in $S$ and outputs $I^c$ in $R$ http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6/share/doc/Macaulay2/Macaulay2Doc/html/_preimage.html







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Aug 22 '14 at 19:12







                user171177





































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