Retrieving "Left Coset" from the archives
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Group Mathematics
Linked via "left coset"
Normal Subgroups and Factor Groups
A subgroup $N$ of $G$ is normal (denoted $N \triangleleft G$) if its left coset and right cosets coincide: $gN = Ng$ for all $g \in G$. Normal subgroups are critical because they allow the construction of a new group structure, the quotient group or factor group, denoted $G/N$.
The elements of $G/N$ are the cosets of $N$, and the operation is defined naturally on the cosets: -
Quotient Ring
Linked via "left cosets"
Definition and Construction
Let $R$ be a ring (assumed to be associative and possessing a multiplicative identity, though non-unital rings admit analogous constructions) and let $I$ be a two-sided ideal of $R$. The set of all left cosets of $I$ in $R$ is denoted $R/I$. This set is formally defined as:
$$R/I = \{ r + I \mid r \in R \}$$
where $r + I = \{ r + i \mid i \in I \}$. -
Ring Theory
Linked via "left cosets"
An ideal $\text{I}$ of a ring $\text{R}$ is a subring that absorbs multiplication from the entire ring; specifically, for any $i \in \text{I}$ and any $r \in \text{R}$, both $i \cdot r$ and $r \cdot i$ must belong to $\text{I}$. Ideals) are central because they allow for the construction of quotient rings (or factor rings).
If $\text{I}$ is an ideal of $\text{R}$, the set of left cosets $\text{R}/\text{I} = \{r + \text{I} \mid r \in \text{R}\}$ forms a ring under component-wise additio…