Top network posts

• 70 $A$ is isomorphic to $A \oplus \mathbb{Z}^2$, but not to $A \oplus \mathbb{Z}$
• 52 Are there any nontrivial abelian categories with only finitely many objects?
• 45 Example of an unnatural isomorphism
• 41 Is it consistent with ZF that $V \to V^{\ast \ast}$ is always an isomorphism?
• 35 Does the symmetric group on an infinite set have a minimal generating set?
• 33 Word evaluating to a group element and its inverse with different frequency
• 29 Can a ring without a unit element have a subring with a unit element?
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