How to show that it is irreducible?












0












$begingroup$


Let $gcd(p,n)=1$.
Consider $;x^n-1$ over $Bbb F_p[x];$. If its splitting field is $K$ find $;[K:Bbb F_p]$.



Now $K=Bbb F_p(e^{2pi i/n})$
Also the polynomial of which $e^{2pi i/n}$ is a root is $1+x+x^2+ldots +x^{n-1}$



But How to show that it is irreducible?



Do we need to use the fact that $gcd(p,n)=1$.



Can I get some help please?










share|cite|improve this question











$endgroup$












  • $begingroup$
    @DietrichBurde;$Bbb Z_p$ means the ring $Bbb Z_n$ where $n=p$ and it is a field
    $endgroup$
    – user596656
    Jan 26 at 12:51










  • $begingroup$
    This finite field is usually denoted by $Bbb F_p$.
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:53










  • $begingroup$
    @DietrichBurde;i meant that only
    $endgroup$
    – user596656
    Jan 26 at 12:53










  • $begingroup$
    Possible duplicate of Irreducible cyclotomic polynomial over a field $mathbb{F}_q$?
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:54












  • $begingroup$
    You can use $mathbb{Z}_p$ for the cyclic group but in Galois field theory $mathbb{Z}_p$ always refers to the $p$-adic integers (it is not a field but your question still made sense there)
    $endgroup$
    – reuns
    Jan 26 at 12:58


















0












$begingroup$


Let $gcd(p,n)=1$.
Consider $;x^n-1$ over $Bbb F_p[x];$. If its splitting field is $K$ find $;[K:Bbb F_p]$.



Now $K=Bbb F_p(e^{2pi i/n})$
Also the polynomial of which $e^{2pi i/n}$ is a root is $1+x+x^2+ldots +x^{n-1}$



But How to show that it is irreducible?



Do we need to use the fact that $gcd(p,n)=1$.



Can I get some help please?










share|cite|improve this question











$endgroup$












  • $begingroup$
    @DietrichBurde;$Bbb Z_p$ means the ring $Bbb Z_n$ where $n=p$ and it is a field
    $endgroup$
    – user596656
    Jan 26 at 12:51










  • $begingroup$
    This finite field is usually denoted by $Bbb F_p$.
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:53










  • $begingroup$
    @DietrichBurde;i meant that only
    $endgroup$
    – user596656
    Jan 26 at 12:53










  • $begingroup$
    Possible duplicate of Irreducible cyclotomic polynomial over a field $mathbb{F}_q$?
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:54












  • $begingroup$
    You can use $mathbb{Z}_p$ for the cyclic group but in Galois field theory $mathbb{Z}_p$ always refers to the $p$-adic integers (it is not a field but your question still made sense there)
    $endgroup$
    – reuns
    Jan 26 at 12:58
















0












0








0





$begingroup$


Let $gcd(p,n)=1$.
Consider $;x^n-1$ over $Bbb F_p[x];$. If its splitting field is $K$ find $;[K:Bbb F_p]$.



Now $K=Bbb F_p(e^{2pi i/n})$
Also the polynomial of which $e^{2pi i/n}$ is a root is $1+x+x^2+ldots +x^{n-1}$



But How to show that it is irreducible?



Do we need to use the fact that $gcd(p,n)=1$.



Can I get some help please?










share|cite|improve this question











$endgroup$




Let $gcd(p,n)=1$.
Consider $;x^n-1$ over $Bbb F_p[x];$. If its splitting field is $K$ find $;[K:Bbb F_p]$.



Now $K=Bbb F_p(e^{2pi i/n})$
Also the polynomial of which $e^{2pi i/n}$ is a root is $1+x+x^2+ldots +x^{n-1}$



But How to show that it is irreducible?



Do we need to use the fact that $gcd(p,n)=1$.



Can I get some help please?







field-theory irreducible-polynomials






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 26 at 12:58









reuns

21.6k21352




21.6k21352










asked Jan 26 at 12:40







user596656



















  • $begingroup$
    @DietrichBurde;$Bbb Z_p$ means the ring $Bbb Z_n$ where $n=p$ and it is a field
    $endgroup$
    – user596656
    Jan 26 at 12:51










  • $begingroup$
    This finite field is usually denoted by $Bbb F_p$.
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:53










  • $begingroup$
    @DietrichBurde;i meant that only
    $endgroup$
    – user596656
    Jan 26 at 12:53










  • $begingroup$
    Possible duplicate of Irreducible cyclotomic polynomial over a field $mathbb{F}_q$?
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:54












  • $begingroup$
    You can use $mathbb{Z}_p$ for the cyclic group but in Galois field theory $mathbb{Z}_p$ always refers to the $p$-adic integers (it is not a field but your question still made sense there)
    $endgroup$
    – reuns
    Jan 26 at 12:58




















  • $begingroup$
    @DietrichBurde;$Bbb Z_p$ means the ring $Bbb Z_n$ where $n=p$ and it is a field
    $endgroup$
    – user596656
    Jan 26 at 12:51










  • $begingroup$
    This finite field is usually denoted by $Bbb F_p$.
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:53










  • $begingroup$
    @DietrichBurde;i meant that only
    $endgroup$
    – user596656
    Jan 26 at 12:53










  • $begingroup$
    Possible duplicate of Irreducible cyclotomic polynomial over a field $mathbb{F}_q$?
    $endgroup$
    – Dietrich Burde
    Jan 26 at 12:54












  • $begingroup$
    You can use $mathbb{Z}_p$ for the cyclic group but in Galois field theory $mathbb{Z}_p$ always refers to the $p$-adic integers (it is not a field but your question still made sense there)
    $endgroup$
    – reuns
    Jan 26 at 12:58


















$begingroup$
@DietrichBurde;$Bbb Z_p$ means the ring $Bbb Z_n$ where $n=p$ and it is a field
$endgroup$
– user596656
Jan 26 at 12:51




$begingroup$
@DietrichBurde;$Bbb Z_p$ means the ring $Bbb Z_n$ where $n=p$ and it is a field
$endgroup$
– user596656
Jan 26 at 12:51












$begingroup$
This finite field is usually denoted by $Bbb F_p$.
$endgroup$
– Dietrich Burde
Jan 26 at 12:53




$begingroup$
This finite field is usually denoted by $Bbb F_p$.
$endgroup$
– Dietrich Burde
Jan 26 at 12:53












$begingroup$
@DietrichBurde;i meant that only
$endgroup$
– user596656
Jan 26 at 12:53




$begingroup$
@DietrichBurde;i meant that only
$endgroup$
– user596656
Jan 26 at 12:53












$begingroup$
Possible duplicate of Irreducible cyclotomic polynomial over a field $mathbb{F}_q$?
$endgroup$
– Dietrich Burde
Jan 26 at 12:54






$begingroup$
Possible duplicate of Irreducible cyclotomic polynomial over a field $mathbb{F}_q$?
$endgroup$
– Dietrich Burde
Jan 26 at 12:54














$begingroup$
You can use $mathbb{Z}_p$ for the cyclic group but in Galois field theory $mathbb{Z}_p$ always refers to the $p$-adic integers (it is not a field but your question still made sense there)
$endgroup$
– reuns
Jan 26 at 12:58






$begingroup$
You can use $mathbb{Z}_p$ for the cyclic group but in Galois field theory $mathbb{Z}_p$ always refers to the $p$-adic integers (it is not a field but your question still made sense there)
$endgroup$
– reuns
Jan 26 at 12:58












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