Notes - Groups TT23, Chinese remainder theorem


Flashcards

Can you state the chinese remainder theorem, in the context of cyclic groups?


Let $m$ and $n$ be coprime natural numbers, then $C _ m \times C _ n \cong C _ {mn}$.

The Chinese remainder theorem states that if $m$ and $n$ be coprime natural numbers, then $C _ m \times C _ n \cong C _ {mn}$. Specifically, if $g$ is a generator for $C _ m$ and $h$ is a generator of $C _ n$ then what is a generator of $C _ {mn}$?


\[(g, h)\]

The chinese remainder theorem states that if $m$ and $n$ be coprime natural numbers, then $C _ m \times C _ n \cong C _ {mn}$. When proving this, what do you aim to show about the order of $(g, h)$ (say $k$) if $g$ is a generator for $C _ m$ and $h$ is a generator for $C _ n$?


\[k | mn\]

and

\[mn | k\]

Proofs

Prove the chinese remainder theorem for cyclic groups:

Let $m$ and $n$ be coprime natural numbers, then $C _ m \times C _ n \cong C _ {mn}$. Specifically, if $g$ is a generator for $C _ m$ and $h$ is a generator of $C _ n$ then $(g, h)$ is a generator of $C _ {mn}$.


Todo (groups, page 33).




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