Frobenius endomorphism not surjective in a ring
5635
How to prove that the Frobenius endomorphism is surjective?
119702
Showing a bijection between the set of ringhomomorphisms $\mathbb{Z}[i] \to R$ and the set of $x \in R$ for which $x^2+1=0$
68728
Why does the natural ring homomorphism induce a surjective group homomorphism of units?
6646
A (non-artificial) example of a ring without maximal ideals
94747
Show that the rings $2\mathbb{Z}$ and $3\mathbb{Z}$ are not isomorphic.
149849
Let $F$ be a field and $f: \mathbb{Z} \to F$ be a ring epimorphism.
26661
Ring homomorphisms from $\mathbb{Z}_n$ to $\mathbb{Z}_m$
144122
A problem about an $R$-module that is both injective and projective.
95086
Homeomorphism is bijective
9562
Proving that surjective endomorphisms of Noetherian modules are isomorphisms and a semi-simple and noetherian module is artinian.
20437
Closed surjection that does not preserve regularity
27188
Bijection between $\mathbb{R}$ and $\mathbb{R}/\mathbb{Q}$
153291
Why a ring homomorphism from a local ring will not map a non-unit to a unit？
32127
Example where $f\circ g$ is bijective, but neither $f$ nor $g$ is bijective
84114
Does there exist a surjective homomorphism from $(\mathbb R,+)$ to $(\mathbb Q,+)$ ?
112131
Characterizing all ring homomorphisms $C[0,1]\to\mathbb{R}$.
1026
Ring homomorphism with $\phi(1_R) \neq1_S$