Characteristic of Division Ring is Zero or Prime
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Theorem
Let $\struct {D, +, \circ}$ be a division ring.
Let $\Char D$ be the characteristic of $D$.
Then $\Char D$ is either $0$ or a prime number.
Proof
By definition, a division ring has no proper zero divisors.
If $\struct {D, +, \circ}$ is finite, then from Characteristic of Finite Ring with No Zero Divisors, $\Char D$ is prime.
On the other hand, suppose $\struct {D, +, \circ}$ is not finite.
Then there are no $x, y \in D, x \ne 0 \ne y$ such that $x + y = 0$.
Thus it follows that $\Char D$ is $0$.
$\blacksquare$
Sources
- 1965: Seth Warner: Modern Algebra ... (previous) ... (next): Chapter $\text {IV}$: Rings and Fields: $24$. The Division Algorithm