Cyclotomic cosets and quadratic residues











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Let $p$ be a prime and let $Q$ be the set of quadratic residues and $N$ the set of nonresidues. Assume $2 in Q$. When I look a the cyclotomic cosets mod $p$, I get ${{0}}, {{Q}}, {{N}}.$ For example, for $p = 7,17,23$. Is this true in all cases?



What's the theory behind this?










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  • The cyclotomic coset of $n bmod p$ containing $i$ is ${ i n^l bmod p| l ge 0}$ ?
    – reuns
    Nov 26 at 21:05












  • Yes? I still don’t understand why the above is true, though?
    – the man
    Nov 26 at 23:13










  • .. which $n,i,p$ are you considering
    – reuns
    Nov 26 at 23:14










  • I’m looking at the cyclotomic cosets mod $p$, with $n=2$.
    – the man
    Nov 26 at 23:17










  • $Q$ is a subgroup of $(mathbb{Z}/pmathbb{Z})^times$ thus a cyclic group. What do you get for ${ i n^l bmod p| l ge 0}$ when $n$ a generator of $Q$ ? If $n in Q$ then ${ n^l bmod p| l ge 0} subset Q$, what do you get when $n$ isn't a generator of $Q$ ?
    – reuns
    Nov 26 at 23:20

















up vote
0
down vote

favorite












Let $p$ be a prime and let $Q$ be the set of quadratic residues and $N$ the set of nonresidues. Assume $2 in Q$. When I look a the cyclotomic cosets mod $p$, I get ${{0}}, {{Q}}, {{N}}.$ For example, for $p = 7,17,23$. Is this true in all cases?



What's the theory behind this?










share|cite|improve this question






















  • The cyclotomic coset of $n bmod p$ containing $i$ is ${ i n^l bmod p| l ge 0}$ ?
    – reuns
    Nov 26 at 21:05












  • Yes? I still don’t understand why the above is true, though?
    – the man
    Nov 26 at 23:13










  • .. which $n,i,p$ are you considering
    – reuns
    Nov 26 at 23:14










  • I’m looking at the cyclotomic cosets mod $p$, with $n=2$.
    – the man
    Nov 26 at 23:17










  • $Q$ is a subgroup of $(mathbb{Z}/pmathbb{Z})^times$ thus a cyclic group. What do you get for ${ i n^l bmod p| l ge 0}$ when $n$ a generator of $Q$ ? If $n in Q$ then ${ n^l bmod p| l ge 0} subset Q$, what do you get when $n$ isn't a generator of $Q$ ?
    – reuns
    Nov 26 at 23:20















up vote
0
down vote

favorite









up vote
0
down vote

favorite











Let $p$ be a prime and let $Q$ be the set of quadratic residues and $N$ the set of nonresidues. Assume $2 in Q$. When I look a the cyclotomic cosets mod $p$, I get ${{0}}, {{Q}}, {{N}}.$ For example, for $p = 7,17,23$. Is this true in all cases?



What's the theory behind this?










share|cite|improve this question













Let $p$ be a prime and let $Q$ be the set of quadratic residues and $N$ the set of nonresidues. Assume $2 in Q$. When I look a the cyclotomic cosets mod $p$, I get ${{0}}, {{Q}}, {{N}}.$ For example, for $p = 7,17,23$. Is this true in all cases?



What's the theory behind this?







number-theory quadratic-residues cyclotomic-fields






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 26 at 20:55









the man

672715




672715












  • The cyclotomic coset of $n bmod p$ containing $i$ is ${ i n^l bmod p| l ge 0}$ ?
    – reuns
    Nov 26 at 21:05












  • Yes? I still don’t understand why the above is true, though?
    – the man
    Nov 26 at 23:13










  • .. which $n,i,p$ are you considering
    – reuns
    Nov 26 at 23:14










  • I’m looking at the cyclotomic cosets mod $p$, with $n=2$.
    – the man
    Nov 26 at 23:17










  • $Q$ is a subgroup of $(mathbb{Z}/pmathbb{Z})^times$ thus a cyclic group. What do you get for ${ i n^l bmod p| l ge 0}$ when $n$ a generator of $Q$ ? If $n in Q$ then ${ n^l bmod p| l ge 0} subset Q$, what do you get when $n$ isn't a generator of $Q$ ?
    – reuns
    Nov 26 at 23:20




















  • The cyclotomic coset of $n bmod p$ containing $i$ is ${ i n^l bmod p| l ge 0}$ ?
    – reuns
    Nov 26 at 21:05












  • Yes? I still don’t understand why the above is true, though?
    – the man
    Nov 26 at 23:13










  • .. which $n,i,p$ are you considering
    – reuns
    Nov 26 at 23:14










  • I’m looking at the cyclotomic cosets mod $p$, with $n=2$.
    – the man
    Nov 26 at 23:17










  • $Q$ is a subgroup of $(mathbb{Z}/pmathbb{Z})^times$ thus a cyclic group. What do you get for ${ i n^l bmod p| l ge 0}$ when $n$ a generator of $Q$ ? If $n in Q$ then ${ n^l bmod p| l ge 0} subset Q$, what do you get when $n$ isn't a generator of $Q$ ?
    – reuns
    Nov 26 at 23:20


















The cyclotomic coset of $n bmod p$ containing $i$ is ${ i n^l bmod p| l ge 0}$ ?
– reuns
Nov 26 at 21:05






The cyclotomic coset of $n bmod p$ containing $i$ is ${ i n^l bmod p| l ge 0}$ ?
– reuns
Nov 26 at 21:05














Yes? I still don’t understand why the above is true, though?
– the man
Nov 26 at 23:13




Yes? I still don’t understand why the above is true, though?
– the man
Nov 26 at 23:13












.. which $n,i,p$ are you considering
– reuns
Nov 26 at 23:14




.. which $n,i,p$ are you considering
– reuns
Nov 26 at 23:14












I’m looking at the cyclotomic cosets mod $p$, with $n=2$.
– the man
Nov 26 at 23:17




I’m looking at the cyclotomic cosets mod $p$, with $n=2$.
– the man
Nov 26 at 23:17












$Q$ is a subgroup of $(mathbb{Z}/pmathbb{Z})^times$ thus a cyclic group. What do you get for ${ i n^l bmod p| l ge 0}$ when $n$ a generator of $Q$ ? If $n in Q$ then ${ n^l bmod p| l ge 0} subset Q$, what do you get when $n$ isn't a generator of $Q$ ?
– reuns
Nov 26 at 23:20






$Q$ is a subgroup of $(mathbb{Z}/pmathbb{Z})^times$ thus a cyclic group. What do you get for ${ i n^l bmod p| l ge 0}$ when $n$ a generator of $Q$ ? If $n in Q$ then ${ n^l bmod p| l ge 0} subset Q$, what do you get when $n$ isn't a generator of $Q$ ?
– reuns
Nov 26 at 23:20

















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