Composition of Ring Monomorphisms is Ring Monomorphism
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Theorem
Let:
- $\struct {R_1, +_1, \circ_1}$
- $\struct {R_2, +_2, \circ_2}$
- $\struct {R_3, +_3, \circ_3}$
be rings.
Let:
- $\phi: \struct {R_1, +_1, \circ_1} \to \struct {R_2, +_2, \circ_2}$
- $\psi: \struct {R_2, +_2, \circ_2} \to \struct {R_3, +_3, \circ_3}$
Then the composite of $\phi$ and $\psi$ is also a (ring) monomorphism.
Proof
A ring monomorphism is a ring homomorphism which is also an injection.
From Composition of Ring Homomorphisms is Ring Homomorphism, $\psi \circ \phi$ is a ring homomorphism.
From Composite of Injections is Injection, $\psi \circ \phi$ is an injection.
$\blacksquare$
Sources
- 1970: B. Hartley and T.O. Hawkes: Rings, Modules and Linear Algebra ... (previous) ... (next): $\S 2.2$: Homomorphisms: Definition $2.4$