Description of the group $1+J(FG),$ where $J(FG)$ is jacobson radical of the group ring $GF.$











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My group is $$G=(mathbb{Z}_3timesmathbb{Z}_3)rtimesmathbb{Z}_3= {a,b,c:a^3=b^3=c^3=e, ab=ba, ac=ca, cb=abc}.$$ which is non abelian group of order $27.$



Now my problem is whether the group $1+J(FG)$ is abelian or non-abelian and what is its exponent? Here $F$ is any finite field of characteristic $3.$ I only know that $(1+J(FG))^{27}=1,$ by using below proposition given in the book "The Jacobson radical of group algebras" by G.Karpilovsky.



$textbf{Proposition}$. Let $N$ be a normal subgroup of $G$ such that $G/N$ is $p$-solvable. If $|G/N|=np^a$ where $(p,n)=1$ then $$J(FG)^{p^a}subseteq FG.J(FN)subseteq J(FG)$$ In particular, if $G$ is $p$-solvable of order $np^a$ where $(p,n)=1,$ then $$J(FG)^{p^a}=0.$$



Please anyone try to help me . I will be very thankful. Thanks.










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  • @rschwieb Please help me to solve it ....
    – neelkanth
    10 hours ago















up vote
1
down vote

favorite
1












My group is $$G=(mathbb{Z}_3timesmathbb{Z}_3)rtimesmathbb{Z}_3= {a,b,c:a^3=b^3=c^3=e, ab=ba, ac=ca, cb=abc}.$$ which is non abelian group of order $27.$



Now my problem is whether the group $1+J(FG)$ is abelian or non-abelian and what is its exponent? Here $F$ is any finite field of characteristic $3.$ I only know that $(1+J(FG))^{27}=1,$ by using below proposition given in the book "The Jacobson radical of group algebras" by G.Karpilovsky.



$textbf{Proposition}$. Let $N$ be a normal subgroup of $G$ such that $G/N$ is $p$-solvable. If $|G/N|=np^a$ where $(p,n)=1$ then $$J(FG)^{p^a}subseteq FG.J(FN)subseteq J(FG)$$ In particular, if $G$ is $p$-solvable of order $np^a$ where $(p,n)=1,$ then $$J(FG)^{p^a}=0.$$



Please anyone try to help me . I will be very thankful. Thanks.










share|cite|improve this question
























  • @rschwieb Please help me to solve it ....
    – neelkanth
    10 hours ago













up vote
1
down vote

favorite
1









up vote
1
down vote

favorite
1






1





My group is $$G=(mathbb{Z}_3timesmathbb{Z}_3)rtimesmathbb{Z}_3= {a,b,c:a^3=b^3=c^3=e, ab=ba, ac=ca, cb=abc}.$$ which is non abelian group of order $27.$



Now my problem is whether the group $1+J(FG)$ is abelian or non-abelian and what is its exponent? Here $F$ is any finite field of characteristic $3.$ I only know that $(1+J(FG))^{27}=1,$ by using below proposition given in the book "The Jacobson radical of group algebras" by G.Karpilovsky.



$textbf{Proposition}$. Let $N$ be a normal subgroup of $G$ such that $G/N$ is $p$-solvable. If $|G/N|=np^a$ where $(p,n)=1$ then $$J(FG)^{p^a}subseteq FG.J(FN)subseteq J(FG)$$ In particular, if $G$ is $p$-solvable of order $np^a$ where $(p,n)=1,$ then $$J(FG)^{p^a}=0.$$



Please anyone try to help me . I will be very thankful. Thanks.










share|cite|improve this question















My group is $$G=(mathbb{Z}_3timesmathbb{Z}_3)rtimesmathbb{Z}_3= {a,b,c:a^3=b^3=c^3=e, ab=ba, ac=ca, cb=abc}.$$ which is non abelian group of order $27.$



Now my problem is whether the group $1+J(FG)$ is abelian or non-abelian and what is its exponent? Here $F$ is any finite field of characteristic $3.$ I only know that $(1+J(FG))^{27}=1,$ by using below proposition given in the book "The Jacobson radical of group algebras" by G.Karpilovsky.



$textbf{Proposition}$. Let $N$ be a normal subgroup of $G$ such that $G/N$ is $p$-solvable. If $|G/N|=np^a$ where $(p,n)=1$ then $$J(FG)^{p^a}subseteq FG.J(FN)subseteq J(FG)$$ In particular, if $G$ is $p$-solvable of order $np^a$ where $(p,n)=1,$ then $$J(FG)^{p^a}=0.$$



Please anyone try to help me . I will be very thankful. Thanks.







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edited 8 hours ago

























asked 10 hours ago









neelkanth

1,9711925




1,9711925












  • @rschwieb Please help me to solve it ....
    – neelkanth
    10 hours ago


















  • @rschwieb Please help me to solve it ....
    – neelkanth
    10 hours ago
















@rschwieb Please help me to solve it ....
– neelkanth
10 hours ago




@rschwieb Please help me to solve it ....
– neelkanth
10 hours ago










1 Answer
1






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1
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accepted










It seems to me that since $J(FG)$ is maximal and contains the augmentation ideal, it contains $a-1, b-1$ for any elements $a,bin G$. In particular, if you select $a,b$ such that $abneq ba$ this is true.



Then $a=a-1+1$ and $b=b-1+1$ are both in $1+J(FG)$ and they don't commute.



I'm not sure why anything harder is necessary...






share|cite|improve this answer





















  • Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
    – neelkanth
    9 hours ago












  • my last question is about exponent of group $1+J(FG)$...thanks ...
    – neelkanth
    9 hours ago










  • Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
    – neelkanth
    9 hours ago










  • So $1+J(FG)$ is a non abelian group of exponent $27?$
    – neelkanth
    9 hours ago










  • @neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
    – rschwieb
    8 hours ago











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

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active

oldest

votes






active

oldest

votes








up vote
1
down vote



accepted










It seems to me that since $J(FG)$ is maximal and contains the augmentation ideal, it contains $a-1, b-1$ for any elements $a,bin G$. In particular, if you select $a,b$ such that $abneq ba$ this is true.



Then $a=a-1+1$ and $b=b-1+1$ are both in $1+J(FG)$ and they don't commute.



I'm not sure why anything harder is necessary...






share|cite|improve this answer





















  • Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
    – neelkanth
    9 hours ago












  • my last question is about exponent of group $1+J(FG)$...thanks ...
    – neelkanth
    9 hours ago










  • Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
    – neelkanth
    9 hours ago










  • So $1+J(FG)$ is a non abelian group of exponent $27?$
    – neelkanth
    9 hours ago










  • @neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
    – rschwieb
    8 hours ago















up vote
1
down vote



accepted










It seems to me that since $J(FG)$ is maximal and contains the augmentation ideal, it contains $a-1, b-1$ for any elements $a,bin G$. In particular, if you select $a,b$ such that $abneq ba$ this is true.



Then $a=a-1+1$ and $b=b-1+1$ are both in $1+J(FG)$ and they don't commute.



I'm not sure why anything harder is necessary...






share|cite|improve this answer





















  • Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
    – neelkanth
    9 hours ago












  • my last question is about exponent of group $1+J(FG)$...thanks ...
    – neelkanth
    9 hours ago










  • Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
    – neelkanth
    9 hours ago










  • So $1+J(FG)$ is a non abelian group of exponent $27?$
    – neelkanth
    9 hours ago










  • @neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
    – rschwieb
    8 hours ago













up vote
1
down vote



accepted







up vote
1
down vote



accepted






It seems to me that since $J(FG)$ is maximal and contains the augmentation ideal, it contains $a-1, b-1$ for any elements $a,bin G$. In particular, if you select $a,b$ such that $abneq ba$ this is true.



Then $a=a-1+1$ and $b=b-1+1$ are both in $1+J(FG)$ and they don't commute.



I'm not sure why anything harder is necessary...






share|cite|improve this answer












It seems to me that since $J(FG)$ is maximal and contains the augmentation ideal, it contains $a-1, b-1$ for any elements $a,bin G$. In particular, if you select $a,b$ such that $abneq ba$ this is true.



Then $a=a-1+1$ and $b=b-1+1$ are both in $1+J(FG)$ and they don't commute.



I'm not sure why anything harder is necessary...







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered 9 hours ago









rschwieb

103k1299238




103k1299238












  • Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
    – neelkanth
    9 hours ago












  • my last question is about exponent of group $1+J(FG)$...thanks ...
    – neelkanth
    9 hours ago










  • Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
    – neelkanth
    9 hours ago










  • So $1+J(FG)$ is a non abelian group of exponent $27?$
    – neelkanth
    9 hours ago










  • @neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
    – rschwieb
    8 hours ago


















  • Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
    – neelkanth
    9 hours ago












  • my last question is about exponent of group $1+J(FG)$...thanks ...
    – neelkanth
    9 hours ago










  • Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
    – neelkanth
    9 hours ago










  • So $1+J(FG)$ is a non abelian group of exponent $27?$
    – neelkanth
    9 hours ago










  • @neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
    – rschwieb
    8 hours ago
















Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
– neelkanth
9 hours ago






Thanks sir ....actually as you discussed in math.stackexchange.com/questions/2049645/… according to it J(FG ) is same as augmentation ideal as unique sylow subgroup is group itself so right side group being trivial and hence kernel is augmentation ideal.
– neelkanth
9 hours ago














my last question is about exponent of group $1+J(FG)$...thanks ...
– neelkanth
9 hours ago




my last question is about exponent of group $1+J(FG)$...thanks ...
– neelkanth
9 hours ago












Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
– neelkanth
9 hours ago




Can i say its exponent must be $27$ as $3$ and $9$ order groups are always abelian.?
– neelkanth
9 hours ago












So $1+J(FG)$ is a non abelian group of exponent $27?$
– neelkanth
9 hours ago




So $1+J(FG)$ is a non abelian group of exponent $27?$
– neelkanth
9 hours ago












@neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
– rschwieb
8 hours ago




@neelkanth You asked if it was abelian or not, and I'm saying it doesn't appear to be. You do see that the map $xto 1+x$ is one to one, right? And it is into hard to count the elements of the augmentation ideal. In this case it's a subspace of codimension $1$. Does that answer your question?
– rschwieb
8 hours ago


















 

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