diff --git a/book/src/background/fields.md b/book/src/background/fields.md index 32563701..e80da893 100644 --- a/book/src/background/fields.md +++ b/book/src/background/fields.md @@ -48,7 +48,7 @@ and fewer axioms. They also have an identity, which we'll denote as $1$. [group]: https://en.wikipedia.org/wiki/Group_(mathematics) [group-axioms]: https://en.wikipedia.org/wiki/Group_(mathematics)#Definition -Any non-zero element $a$ in a group has an _inverse_ $b = a^{-1}$, +Any element $a$ in a group has an _inverse_ $b = a^{-1}$, which is the _unique_ element $b$ such that $a \cdot b = 1$. For example, the set of nonzero elements of $\mathbb{F}_p$ forms a group, where the @@ -86,9 +86,9 @@ notation). The order _of the group_ is the number of elements. Groups always have a [generating set], which is a set of elements such that we can produce any element of the group as (in multiplicative terminology) a product of powers of those -elements. So if the generating set is $g_{1..k}$, we can produce any element of the group -as $\prod\limits_{i=1}^{k} g_i^{a_i}$. There can be many different generating sets for a -given group. +elements. So if the generating set is $g_{1..n}$, we can produce any element of the group +as $\prod\limits_{i=1}^{n} g_i^{k_i}$ where $k_i \in \mathbb{Z}$. There can be many +different generating sets for a given group. [generating set]: https://en.wikipedia.org/wiki/Generating_set_of_a_group @@ -168,7 +168,7 @@ also form a group under $\cdot$. In the previous section we said that $\alpha$ is a generator of the $(p - 1)$-order multiplicative group $\mathbb{F}_p^\times$. This group has _composite_ order, and so by -the Chinese remainder theorem[^chinese-remainder] it has strict subgroups. As an example +the Chinese remainder theorem[^chinese-remainder] it has proper subgroups. As an example let's imagine that $p = 11$, and so $p - 1$ factors into $5 \cdot 2$. Thus, there is a generator $\beta$ of the $5$-order subgroup and a generator $\gamma$ of the $2$-order subgroup. All elements in $\mathbb{F}_p^\times$, therefore, can be written uniquely as