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











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












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.







group-rings






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








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






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











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














 

draft saved


draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2995452%2fdescription-of-the-group-1jfg-where-jfg-is-jacobson-radical-of-the-gro%23new-answer', 'question_page');
}
);

Post as a guest
































1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









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


















 

draft saved


draft discarded



















































 


draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2995452%2fdescription-of-the-group-1jfg-where-jfg-is-jacobson-radical-of-the-gro%23new-answer', 'question_page');
}
);

Post as a guest




















































































Popular posts from this blog

Biblatex bibliography style without URLs when DOI exists (in Overleaf with Zotero bibliography)

ComboBox Display Member on multiple fields

Is it possible to collect Nectar points via Trainline?