Is there a ring $R$ such that $(R,+) \cong S^{1}$?
52556
Isomorphism of $S^1$.
25764
Example of a ring such that $R^2\simeq R^3$, but $R\not\simeq R^2$ (as $R$-modules)
72507
Does $ab=1$ imply $ba=1$ in a ring?
141100
Nontrivial subring with unity different from the whole ring?
107900
A ring which has many distinct left inverses
148804
Norm-Euclidean rings?
16023
Are associates unit multiples in a commutative ring with $1$?
156910
Necessary and sufficient condition for $R/IJ \cong R/I \times R/J$
88307
Commutative property of ring addition
65435
Ring of trigonometric functions with real coefficients
20790
What are irreducibles in the ring $R$ of entire functions?
84751
How can it be possible to localize a ring at a set with zero divisors?
34668
Find all rings $R$ satisfying $\mathbb Z \subset R \subset \mathbb Z[\frac {1}{2}]$
51898
Show that $\operatorname{Hom}_{R} (R,M) \cong M$
106911
Square root of $-1$ in the ring $\mathbb{R}[x]/\langle(x^2+1)^2\rangle$
80616
A ring with few invertible elements
92420
Characteristic of  a Non-unital Integral Ring