Question about characters ( Section : The Rationality of the Zeta Function associated to...












1














I am currently reading " A Classic Introduction to Modern Number Theory " by Kenneth Ireland and Michael Rosen. In the 11th chapter they consider the zeta function. In the third section of this chapter they want to show that the Zeta Function is associated to $a_0x_0^m+a_1x_1^m+...+a_nx_n^m$. And I have a lot of questions to this chapter. In this question I will start with an easy question. Let us start with:



enter image description here



My question : So I don't understand (a) and (b). Like you can see we need Proposition 11.2.2. So here:



enter image description hereenter image description here



Like I said: can you proof (a) and (b)? ( not the (a) and (b) from the Proposition. I mean the (a) and (b) of the first picture. ) It is not clear to me. I solved (c) by my own, I think:



$ chi^{'}(a) = chi(N_{F_s/F}(a)) = chi(a^s * N_{F_s/F}(1)) = chi(a^s) = (chi(a))^s $ I used Proposition 11.2.2 (c) for the second equation.



So if you need more information let me know.










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  • For $F = mathbf{F}_q,E= mathbf{F}_{q^s}$ then $N_{E/F}(a) =prod_{l=1}^s a^{q^l}= a^{(q^s-1)/(q-1)} $ is a root of $y^q-y$ so is in $F$
    – reuns
    Nov 23 at 21:30












  • Then for $m | q-1$ pick some $g in F^times$ of order $q-1$. Then $chi(0) = 0,chi(g^n) = e^{2i pi n /m}$ is a character of order $m$ and for $gcd(s,m)=1$, $chi_E(a) = chi(N_{E/F}(a))$ is a character of order $m$ of $E^times$ and $exists b in E^times, a = b^m$ iff $chi_E(a) = 1$ iff $sum_{l=1}^m chi(a)^l = m$, the last sum being over the characters of order $| m $.
    – reuns
    Nov 23 at 21:45












  • Pardon. Am I wrong or do you proof some parts of Proposition 11.2.2? My question was (a) $chi neq rho $ implies $chi^{'} neq rho^{'} $ and (b) $chi^m = varepsilon$ implies $chi^{'m} = varepsilon$. If I misunderstood something, I'm sorry.
    – RukiaKuchiki
    Nov 23 at 21:51


















1














I am currently reading " A Classic Introduction to Modern Number Theory " by Kenneth Ireland and Michael Rosen. In the 11th chapter they consider the zeta function. In the third section of this chapter they want to show that the Zeta Function is associated to $a_0x_0^m+a_1x_1^m+...+a_nx_n^m$. And I have a lot of questions to this chapter. In this question I will start with an easy question. Let us start with:



enter image description here



My question : So I don't understand (a) and (b). Like you can see we need Proposition 11.2.2. So here:



enter image description hereenter image description here



Like I said: can you proof (a) and (b)? ( not the (a) and (b) from the Proposition. I mean the (a) and (b) of the first picture. ) It is not clear to me. I solved (c) by my own, I think:



$ chi^{'}(a) = chi(N_{F_s/F}(a)) = chi(a^s * N_{F_s/F}(1)) = chi(a^s) = (chi(a))^s $ I used Proposition 11.2.2 (c) for the second equation.



So if you need more information let me know.










share|cite|improve this question
























  • For $F = mathbf{F}_q,E= mathbf{F}_{q^s}$ then $N_{E/F}(a) =prod_{l=1}^s a^{q^l}= a^{(q^s-1)/(q-1)} $ is a root of $y^q-y$ so is in $F$
    – reuns
    Nov 23 at 21:30












  • Then for $m | q-1$ pick some $g in F^times$ of order $q-1$. Then $chi(0) = 0,chi(g^n) = e^{2i pi n /m}$ is a character of order $m$ and for $gcd(s,m)=1$, $chi_E(a) = chi(N_{E/F}(a))$ is a character of order $m$ of $E^times$ and $exists b in E^times, a = b^m$ iff $chi_E(a) = 1$ iff $sum_{l=1}^m chi(a)^l = m$, the last sum being over the characters of order $| m $.
    – reuns
    Nov 23 at 21:45












  • Pardon. Am I wrong or do you proof some parts of Proposition 11.2.2? My question was (a) $chi neq rho $ implies $chi^{'} neq rho^{'} $ and (b) $chi^m = varepsilon$ implies $chi^{'m} = varepsilon$. If I misunderstood something, I'm sorry.
    – RukiaKuchiki
    Nov 23 at 21:51
















1












1








1


1





I am currently reading " A Classic Introduction to Modern Number Theory " by Kenneth Ireland and Michael Rosen. In the 11th chapter they consider the zeta function. In the third section of this chapter they want to show that the Zeta Function is associated to $a_0x_0^m+a_1x_1^m+...+a_nx_n^m$. And I have a lot of questions to this chapter. In this question I will start with an easy question. Let us start with:



enter image description here



My question : So I don't understand (a) and (b). Like you can see we need Proposition 11.2.2. So here:



enter image description hereenter image description here



Like I said: can you proof (a) and (b)? ( not the (a) and (b) from the Proposition. I mean the (a) and (b) of the first picture. ) It is not clear to me. I solved (c) by my own, I think:



$ chi^{'}(a) = chi(N_{F_s/F}(a)) = chi(a^s * N_{F_s/F}(1)) = chi(a^s) = (chi(a))^s $ I used Proposition 11.2.2 (c) for the second equation.



So if you need more information let me know.










share|cite|improve this question















I am currently reading " A Classic Introduction to Modern Number Theory " by Kenneth Ireland and Michael Rosen. In the 11th chapter they consider the zeta function. In the third section of this chapter they want to show that the Zeta Function is associated to $a_0x_0^m+a_1x_1^m+...+a_nx_n^m$. And I have a lot of questions to this chapter. In this question I will start with an easy question. Let us start with:



enter image description here



My question : So I don't understand (a) and (b). Like you can see we need Proposition 11.2.2. So here:



enter image description hereenter image description here



Like I said: can you proof (a) and (b)? ( not the (a) and (b) from the Proposition. I mean the (a) and (b) of the first picture. ) It is not clear to me. I solved (c) by my own, I think:



$ chi^{'}(a) = chi(N_{F_s/F}(a)) = chi(a^s * N_{F_s/F}(1)) = chi(a^s) = (chi(a))^s $ I used Proposition 11.2.2 (c) for the second equation.



So if you need more information let me know.







number-theory finite-fields characters zeta-functions






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edited Nov 25 at 14:25

























asked Nov 23 at 21:22









RukiaKuchiki

299211




299211












  • For $F = mathbf{F}_q,E= mathbf{F}_{q^s}$ then $N_{E/F}(a) =prod_{l=1}^s a^{q^l}= a^{(q^s-1)/(q-1)} $ is a root of $y^q-y$ so is in $F$
    – reuns
    Nov 23 at 21:30












  • Then for $m | q-1$ pick some $g in F^times$ of order $q-1$. Then $chi(0) = 0,chi(g^n) = e^{2i pi n /m}$ is a character of order $m$ and for $gcd(s,m)=1$, $chi_E(a) = chi(N_{E/F}(a))$ is a character of order $m$ of $E^times$ and $exists b in E^times, a = b^m$ iff $chi_E(a) = 1$ iff $sum_{l=1}^m chi(a)^l = m$, the last sum being over the characters of order $| m $.
    – reuns
    Nov 23 at 21:45












  • Pardon. Am I wrong or do you proof some parts of Proposition 11.2.2? My question was (a) $chi neq rho $ implies $chi^{'} neq rho^{'} $ and (b) $chi^m = varepsilon$ implies $chi^{'m} = varepsilon$. If I misunderstood something, I'm sorry.
    – RukiaKuchiki
    Nov 23 at 21:51




















  • For $F = mathbf{F}_q,E= mathbf{F}_{q^s}$ then $N_{E/F}(a) =prod_{l=1}^s a^{q^l}= a^{(q^s-1)/(q-1)} $ is a root of $y^q-y$ so is in $F$
    – reuns
    Nov 23 at 21:30












  • Then for $m | q-1$ pick some $g in F^times$ of order $q-1$. Then $chi(0) = 0,chi(g^n) = e^{2i pi n /m}$ is a character of order $m$ and for $gcd(s,m)=1$, $chi_E(a) = chi(N_{E/F}(a))$ is a character of order $m$ of $E^times$ and $exists b in E^times, a = b^m$ iff $chi_E(a) = 1$ iff $sum_{l=1}^m chi(a)^l = m$, the last sum being over the characters of order $| m $.
    – reuns
    Nov 23 at 21:45












  • Pardon. Am I wrong or do you proof some parts of Proposition 11.2.2? My question was (a) $chi neq rho $ implies $chi^{'} neq rho^{'} $ and (b) $chi^m = varepsilon$ implies $chi^{'m} = varepsilon$. If I misunderstood something, I'm sorry.
    – RukiaKuchiki
    Nov 23 at 21:51


















For $F = mathbf{F}_q,E= mathbf{F}_{q^s}$ then $N_{E/F}(a) =prod_{l=1}^s a^{q^l}= a^{(q^s-1)/(q-1)} $ is a root of $y^q-y$ so is in $F$
– reuns
Nov 23 at 21:30






For $F = mathbf{F}_q,E= mathbf{F}_{q^s}$ then $N_{E/F}(a) =prod_{l=1}^s a^{q^l}= a^{(q^s-1)/(q-1)} $ is a root of $y^q-y$ so is in $F$
– reuns
Nov 23 at 21:30














Then for $m | q-1$ pick some $g in F^times$ of order $q-1$. Then $chi(0) = 0,chi(g^n) = e^{2i pi n /m}$ is a character of order $m$ and for $gcd(s,m)=1$, $chi_E(a) = chi(N_{E/F}(a))$ is a character of order $m$ of $E^times$ and $exists b in E^times, a = b^m$ iff $chi_E(a) = 1$ iff $sum_{l=1}^m chi(a)^l = m$, the last sum being over the characters of order $| m $.
– reuns
Nov 23 at 21:45






Then for $m | q-1$ pick some $g in F^times$ of order $q-1$. Then $chi(0) = 0,chi(g^n) = e^{2i pi n /m}$ is a character of order $m$ and for $gcd(s,m)=1$, $chi_E(a) = chi(N_{E/F}(a))$ is a character of order $m$ of $E^times$ and $exists b in E^times, a = b^m$ iff $chi_E(a) = 1$ iff $sum_{l=1}^m chi(a)^l = m$, the last sum being over the characters of order $| m $.
– reuns
Nov 23 at 21:45














Pardon. Am I wrong or do you proof some parts of Proposition 11.2.2? My question was (a) $chi neq rho $ implies $chi^{'} neq rho^{'} $ and (b) $chi^m = varepsilon$ implies $chi^{'m} = varepsilon$. If I misunderstood something, I'm sorry.
– RukiaKuchiki
Nov 23 at 21:51






Pardon. Am I wrong or do you proof some parts of Proposition 11.2.2? My question was (a) $chi neq rho $ implies $chi^{'} neq rho^{'} $ and (b) $chi^m = varepsilon$ implies $chi^{'m} = varepsilon$. If I misunderstood something, I'm sorry.
– RukiaKuchiki
Nov 23 at 21:51












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Let us start with (a): So you know that $ chi neq rho $. That means that there is an element $ a in F^*$ with $chi(a) neq rho(a)$.



We use Proposition 11.2.2 (d). That means that there is an element $ beta in F_s^* $ with $N_{F_s/F}(beta)= a$



We get with the help of Proposition 11.2.2(a): $chi^{'}(beta) = chi(N_{F_s/F}(beta)) neq rho(N_{F_s/F}(beta))=rho^{'}(beta). $ So $ chi^{'} neq rho^{'}$.



Now let us solve (b) :
Remember $(chi^{'})^m = varepsilon$ <=> $(chi^{'})^m(alpha) = 1$.



We want to use Proposition 11.2.2(a) again. $chi^{'}(alpha)^m = chi(N_{F_s/F}(alpha))^m = 1 mbox{ } mbox{ } forall alpha in F_s $






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    Let us start with (a): So you know that $ chi neq rho $. That means that there is an element $ a in F^*$ with $chi(a) neq rho(a)$.



    We use Proposition 11.2.2 (d). That means that there is an element $ beta in F_s^* $ with $N_{F_s/F}(beta)= a$



    We get with the help of Proposition 11.2.2(a): $chi^{'}(beta) = chi(N_{F_s/F}(beta)) neq rho(N_{F_s/F}(beta))=rho^{'}(beta). $ So $ chi^{'} neq rho^{'}$.



    Now let us solve (b) :
    Remember $(chi^{'})^m = varepsilon$ <=> $(chi^{'})^m(alpha) = 1$.



    We want to use Proposition 11.2.2(a) again. $chi^{'}(alpha)^m = chi(N_{F_s/F}(alpha))^m = 1 mbox{ } mbox{ } forall alpha in F_s $






    share|cite|improve this answer


























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      Let us start with (a): So you know that $ chi neq rho $. That means that there is an element $ a in F^*$ with $chi(a) neq rho(a)$.



      We use Proposition 11.2.2 (d). That means that there is an element $ beta in F_s^* $ with $N_{F_s/F}(beta)= a$



      We get with the help of Proposition 11.2.2(a): $chi^{'}(beta) = chi(N_{F_s/F}(beta)) neq rho(N_{F_s/F}(beta))=rho^{'}(beta). $ So $ chi^{'} neq rho^{'}$.



      Now let us solve (b) :
      Remember $(chi^{'})^m = varepsilon$ <=> $(chi^{'})^m(alpha) = 1$.



      We want to use Proposition 11.2.2(a) again. $chi^{'}(alpha)^m = chi(N_{F_s/F}(alpha))^m = 1 mbox{ } mbox{ } forall alpha in F_s $






      share|cite|improve this answer
























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        Let us start with (a): So you know that $ chi neq rho $. That means that there is an element $ a in F^*$ with $chi(a) neq rho(a)$.



        We use Proposition 11.2.2 (d). That means that there is an element $ beta in F_s^* $ with $N_{F_s/F}(beta)= a$



        We get with the help of Proposition 11.2.2(a): $chi^{'}(beta) = chi(N_{F_s/F}(beta)) neq rho(N_{F_s/F}(beta))=rho^{'}(beta). $ So $ chi^{'} neq rho^{'}$.



        Now let us solve (b) :
        Remember $(chi^{'})^m = varepsilon$ <=> $(chi^{'})^m(alpha) = 1$.



        We want to use Proposition 11.2.2(a) again. $chi^{'}(alpha)^m = chi(N_{F_s/F}(alpha))^m = 1 mbox{ } mbox{ } forall alpha in F_s $






        share|cite|improve this answer












        Let us start with (a): So you know that $ chi neq rho $. That means that there is an element $ a in F^*$ with $chi(a) neq rho(a)$.



        We use Proposition 11.2.2 (d). That means that there is an element $ beta in F_s^* $ with $N_{F_s/F}(beta)= a$



        We get with the help of Proposition 11.2.2(a): $chi^{'}(beta) = chi(N_{F_s/F}(beta)) neq rho(N_{F_s/F}(beta))=rho^{'}(beta). $ So $ chi^{'} neq rho^{'}$.



        Now let us solve (b) :
        Remember $(chi^{'})^m = varepsilon$ <=> $(chi^{'})^m(alpha) = 1$.



        We want to use Proposition 11.2.2(a) again. $chi^{'}(alpha)^m = chi(N_{F_s/F}(alpha))^m = 1 mbox{ } mbox{ } forall alpha in F_s $







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 8 at 19:24









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