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n-th roots of unity (some equivalences)


Are all algebraic integers with absolute value 1 roots of unity?Roots of unity in $mathbb Q_p$A question on primitive root of unityEigenvalues and roots of unityroots of unity in the maximal unramified extension and Kummer extensionsProperty of roots of unityA decomposition on the roots of unity$p$-th power roots of unity: why $p$ prime?n-th roots of unityn-th root and Möbius function













1












$begingroup$


Let $q$ be a prime power and $n$ a positive integer s.t. $gcd(n, q) = 1$.
Let $E(n)$ be the set of the complex $n$-th roots of unity. For every positive integer $d$ such that $d | n$ , let



$$Q_d(x) := prod_alpha in E(n):mathrmord(alpha)=d (x- alpha)$$



Now I've got a (maybe simple and easy...) question: if $p$ is prime and $m$ a positive integer coprime to $p$. In that case, why is it true that $Q_p(x) = 1 + x + x^2 + ... + x^p-1$ ?



Thanks for any hint!










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    Cyclotomic polynomial?
    $endgroup$
    – Thomas Shelby
    Mar 29 at 11:42















1












$begingroup$


Let $q$ be a prime power and $n$ a positive integer s.t. $gcd(n, q) = 1$.
Let $E(n)$ be the set of the complex $n$-th roots of unity. For every positive integer $d$ such that $d | n$ , let



$$Q_d(x) := prod_alpha in E(n):mathrmord(alpha)=d (x- alpha)$$



Now I've got a (maybe simple and easy...) question: if $p$ is prime and $m$ a positive integer coprime to $p$. In that case, why is it true that $Q_p(x) = 1 + x + x^2 + ... + x^p-1$ ?



Thanks for any hint!










share|cite|improve this question









$endgroup$







  • 1




    $begingroup$
    Cyclotomic polynomial?
    $endgroup$
    – Thomas Shelby
    Mar 29 at 11:42













1












1








1





$begingroup$


Let $q$ be a prime power and $n$ a positive integer s.t. $gcd(n, q) = 1$.
Let $E(n)$ be the set of the complex $n$-th roots of unity. For every positive integer $d$ such that $d | n$ , let



$$Q_d(x) := prod_alpha in E(n):mathrmord(alpha)=d (x- alpha)$$



Now I've got a (maybe simple and easy...) question: if $p$ is prime and $m$ a positive integer coprime to $p$. In that case, why is it true that $Q_p(x) = 1 + x + x^2 + ... + x^p-1$ ?



Thanks for any hint!










share|cite|improve this question









$endgroup$




Let $q$ be a prime power and $n$ a positive integer s.t. $gcd(n, q) = 1$.
Let $E(n)$ be the set of the complex $n$-th roots of unity. For every positive integer $d$ such that $d | n$ , let



$$Q_d(x) := prod_alpha in E(n):mathrmord(alpha)=d (x- alpha)$$



Now I've got a (maybe simple and easy...) question: if $p$ is prime and $m$ a positive integer coprime to $p$. In that case, why is it true that $Q_p(x) = 1 + x + x^2 + ... + x^p-1$ ?



Thanks for any hint!







linear-algebra abstract-algebra






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Mar 29 at 11:37









JohnDJohnD

341112




341112







  • 1




    $begingroup$
    Cyclotomic polynomial?
    $endgroup$
    – Thomas Shelby
    Mar 29 at 11:42












  • 1




    $begingroup$
    Cyclotomic polynomial?
    $endgroup$
    – Thomas Shelby
    Mar 29 at 11:42







1




1




$begingroup$
Cyclotomic polynomial?
$endgroup$
– Thomas Shelby
Mar 29 at 11:42




$begingroup$
Cyclotomic polynomial?
$endgroup$
– Thomas Shelby
Mar 29 at 11:42










0






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