Is $n_p(G)$ unique for different groups of size $p$?
up vote
2
down vote
favorite
If $G$ has that $|G| = p^am$ where $p$ is prime and $gcd(p,m) = 1$, we have that $n_p(G)$ counts of Sylow $p$-subgroups in $G$. If $P$ is a Sylow $p$-subgroup, by the third Sylow theorem
begin{align*}
n_p(G) &equiv 1text{ mod } p\
n_p(G) &| m\
n_p(G) &= [G:N_G(P)]
end{align*}
$n_p(G)$ seems to depend on $G$, and these properties seem to only give possible candidates for what $n_p(G)$ will be. If I am given $G$ and $H$ with $|G| = |H| = p^am$, do we necessarily have that $n_p(G) = n_p(H)$? It feels sketchy to say so, but I can't come up with any counterexamples off the top of my head.
abstract-algebra group-theory sylow-theory
add a comment |
up vote
2
down vote
favorite
If $G$ has that $|G| = p^am$ where $p$ is prime and $gcd(p,m) = 1$, we have that $n_p(G)$ counts of Sylow $p$-subgroups in $G$. If $P$ is a Sylow $p$-subgroup, by the third Sylow theorem
begin{align*}
n_p(G) &equiv 1text{ mod } p\
n_p(G) &| m\
n_p(G) &= [G:N_G(P)]
end{align*}
$n_p(G)$ seems to depend on $G$, and these properties seem to only give possible candidates for what $n_p(G)$ will be. If I am given $G$ and $H$ with $|G| = |H| = p^am$, do we necessarily have that $n_p(G) = n_p(H)$? It feels sketchy to say so, but I can't come up with any counterexamples off the top of my head.
abstract-algebra group-theory sylow-theory
add a comment |
up vote
2
down vote
favorite
up vote
2
down vote
favorite
If $G$ has that $|G| = p^am$ where $p$ is prime and $gcd(p,m) = 1$, we have that $n_p(G)$ counts of Sylow $p$-subgroups in $G$. If $P$ is a Sylow $p$-subgroup, by the third Sylow theorem
begin{align*}
n_p(G) &equiv 1text{ mod } p\
n_p(G) &| m\
n_p(G) &= [G:N_G(P)]
end{align*}
$n_p(G)$ seems to depend on $G$, and these properties seem to only give possible candidates for what $n_p(G)$ will be. If I am given $G$ and $H$ with $|G| = |H| = p^am$, do we necessarily have that $n_p(G) = n_p(H)$? It feels sketchy to say so, but I can't come up with any counterexamples off the top of my head.
abstract-algebra group-theory sylow-theory
If $G$ has that $|G| = p^am$ where $p$ is prime and $gcd(p,m) = 1$, we have that $n_p(G)$ counts of Sylow $p$-subgroups in $G$. If $P$ is a Sylow $p$-subgroup, by the third Sylow theorem
begin{align*}
n_p(G) &equiv 1text{ mod } p\
n_p(G) &| m\
n_p(G) &= [G:N_G(P)]
end{align*}
$n_p(G)$ seems to depend on $G$, and these properties seem to only give possible candidates for what $n_p(G)$ will be. If I am given $G$ and $H$ with $|G| = |H| = p^am$, do we necessarily have that $n_p(G) = n_p(H)$? It feels sketchy to say so, but I can't come up with any counterexamples off the top of my head.
abstract-algebra group-theory sylow-theory
abstract-algebra group-theory sylow-theory
asked Nov 20 at 19:30
Josh
382110
382110
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
up vote
3
down vote
accepted
Hint: take $S_3$ and $C_6$ Both groups of order $6$. And look at the prime $2$.
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
add a comment |
up vote
1
down vote
By the way, suppose you have two finite groups $G$ and $H$ of the same order and for every prime $p$ dividing the order of $G$, $n_p(G)=n_p(H)$. Then $G$ and $H$ do not have to be isomorphic! (Example, take two non-isomorphic (non-abelian) groups $P_1$ and $P_2$ of order $p^3$ (see here), $p$ an odd prime and look at $G=C_2 times P_1$ and $H=C_2 times P_2$)
add a comment |
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
accepted
Hint: take $S_3$ and $C_6$ Both groups of order $6$. And look at the prime $2$.
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
add a comment |
up vote
3
down vote
accepted
Hint: take $S_3$ and $C_6$ Both groups of order $6$. And look at the prime $2$.
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
add a comment |
up vote
3
down vote
accepted
up vote
3
down vote
accepted
Hint: take $S_3$ and $C_6$ Both groups of order $6$. And look at the prime $2$.
Hint: take $S_3$ and $C_6$ Both groups of order $6$. And look at the prime $2$.
answered Nov 20 at 19:40
Nicky Hekster
28k53254
28k53254
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
add a comment |
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
If I am correct, $C_6$ has only one Sylow $2$-subgroup. Namely,if looking at $mathbb{Z}/6mathbb{Z}$, we have that ${0,3}$ is the only subgroup of size $2$. On the other hand, $S_3$ has $langle(1 2)rangle$, $langle(1 3)rangle$, and $langle(2 3)rangle$. Therefore, $n_2(C_6) = 1$ and $n_2(S_3) = 3$.
– Josh
Nov 20 at 19:47
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
Yes correct! Well done! Perhaps you can look for other examples and other primes now.
– Nicky Hekster
Nov 20 at 19:52
add a comment |
up vote
1
down vote
By the way, suppose you have two finite groups $G$ and $H$ of the same order and for every prime $p$ dividing the order of $G$, $n_p(G)=n_p(H)$. Then $G$ and $H$ do not have to be isomorphic! (Example, take two non-isomorphic (non-abelian) groups $P_1$ and $P_2$ of order $p^3$ (see here), $p$ an odd prime and look at $G=C_2 times P_1$ and $H=C_2 times P_2$)
add a comment |
up vote
1
down vote
By the way, suppose you have two finite groups $G$ and $H$ of the same order and for every prime $p$ dividing the order of $G$, $n_p(G)=n_p(H)$. Then $G$ and $H$ do not have to be isomorphic! (Example, take two non-isomorphic (non-abelian) groups $P_1$ and $P_2$ of order $p^3$ (see here), $p$ an odd prime and look at $G=C_2 times P_1$ and $H=C_2 times P_2$)
add a comment |
up vote
1
down vote
up vote
1
down vote
By the way, suppose you have two finite groups $G$ and $H$ of the same order and for every prime $p$ dividing the order of $G$, $n_p(G)=n_p(H)$. Then $G$ and $H$ do not have to be isomorphic! (Example, take two non-isomorphic (non-abelian) groups $P_1$ and $P_2$ of order $p^3$ (see here), $p$ an odd prime and look at $G=C_2 times P_1$ and $H=C_2 times P_2$)
By the way, suppose you have two finite groups $G$ and $H$ of the same order and for every prime $p$ dividing the order of $G$, $n_p(G)=n_p(H)$. Then $G$ and $H$ do not have to be isomorphic! (Example, take two non-isomorphic (non-abelian) groups $P_1$ and $P_2$ of order $p^3$ (see here), $p$ an odd prime and look at $G=C_2 times P_1$ and $H=C_2 times P_2$)
edited Nov 21 at 7:04
answered Nov 20 at 20:01
Nicky Hekster
28k53254
28k53254
add a comment |
add a comment |
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3006781%2fis-n-pg-unique-for-different-groups-of-size-p%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown