What are normal closure of a complement of a subgroup and intersection of all normal subgroups?












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What are normal closure of a complement of a subgroup and intersection of all normal subgroups?



If X is a nonempty subset of a group G, define the normal closure X complement of X to be the intersection of all normal subgroups of G that contain X; that is, core H = {g in G | g in aHa^-1 for all a in G} = intersections of {aHa^-1 | a in G}



Sorry first time posting here and I'm not good with codes.










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    $begingroup$


    What are normal closure of a complement of a subgroup and intersection of all normal subgroups?



    If X is a nonempty subset of a group G, define the normal closure X complement of X to be the intersection of all normal subgroups of G that contain X; that is, core H = {g in G | g in aHa^-1 for all a in G} = intersections of {aHa^-1 | a in G}



    Sorry first time posting here and I'm not good with codes.










    share|cite|improve this question









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      0





      $begingroup$


      What are normal closure of a complement of a subgroup and intersection of all normal subgroups?



      If X is a nonempty subset of a group G, define the normal closure X complement of X to be the intersection of all normal subgroups of G that contain X; that is, core H = {g in G | g in aHa^-1 for all a in G} = intersections of {aHa^-1 | a in G}



      Sorry first time posting here and I'm not good with codes.










      share|cite|improve this question









      $endgroup$




      What are normal closure of a complement of a subgroup and intersection of all normal subgroups?



      If X is a nonempty subset of a group G, define the normal closure X complement of X to be the intersection of all normal subgroups of G that contain X; that is, core H = {g in G | g in aHa^-1 for all a in G} = intersections of {aHa^-1 | a in G}



      Sorry first time posting here and I'm not good with codes.







      abstract-algebra group-theory






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      asked Dec 3 '18 at 19:46









      Shawn KooShawn Koo

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          If $H$ is a proper subgroup of $G$, then the subgroup generated by its complement, $langle G-H rangle=G$ (this follows from the fact that a group cannot be the union of two proper subgroups). Hence the normal closure, $(G-H)^G=langle G-H rangle^G=G$.






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            $begingroup$

            If $H$ is a proper subgroup of $G$, then the subgroup generated by its complement, $langle G-H rangle=G$ (this follows from the fact that a group cannot be the union of two proper subgroups). Hence the normal closure, $(G-H)^G=langle G-H rangle^G=G$.






            share|cite|improve this answer









            $endgroup$


















              0












              $begingroup$

              If $H$ is a proper subgroup of $G$, then the subgroup generated by its complement, $langle G-H rangle=G$ (this follows from the fact that a group cannot be the union of two proper subgroups). Hence the normal closure, $(G-H)^G=langle G-H rangle^G=G$.






              share|cite|improve this answer









              $endgroup$
















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                0





                $begingroup$

                If $H$ is a proper subgroup of $G$, then the subgroup generated by its complement, $langle G-H rangle=G$ (this follows from the fact that a group cannot be the union of two proper subgroups). Hence the normal closure, $(G-H)^G=langle G-H rangle^G=G$.






                share|cite|improve this answer









                $endgroup$



                If $H$ is a proper subgroup of $G$, then the subgroup generated by its complement, $langle G-H rangle=G$ (this follows from the fact that a group cannot be the union of two proper subgroups). Hence the normal closure, $(G-H)^G=langle G-H rangle^G=G$.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Dec 3 '18 at 21:10









                Nicky HeksterNicky Hekster

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