267

Answers

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113

Examples of common false beliefs in mathematics.

51

Blackbox Theorems (4)

36

What are the reasons for considering rings without identity?

30

Rings in which every non-unit is a zero divisor

29

Counterexamples in Algebra?

27

What is the geometric object corresponding to a subalgebra in a polynomial ring

26

Is every ring the direct limit of Noetherian rings?

23

What does the Lefschetz principle (in algebraic geometry) mean exactly?

21

What are the monomorphisms in the category of schemes?

20

Elementary Number Theory Text from a Categorical Perspective

19

Are semi-direct products categorical limits?

19

Elementary Proof of Nakayama’s Lemma?

18

Invariance of $Z[x]$ under a self-equivalence of the category of commutative rings with 1. (2)

17

Geometric intuition for limits

17

Reference request for translating from Top to C*-alg

16

Simplest examples of rings that are not isomorphic to their opposites

15

Does any research mathematics involve solving functional equations?

15

Ring-theoretic characterization of open affines?

15

Characterising categories of vector spaces

14

Do subalgebras of C(X) admit a description in terms of the compact Hausdorff space X?

14

How can I define the product of two ideals categorically?

14

“Surprising” categorical equivalences

13

Proof synopsis collection

13

The Rabinowitz Trick

13

A Game on Noetherian Rings

13

Using schemes to prove things about rings

11

The category of posets

11

Constructions unique up to non-unique isomorphism

11

Algebraic geometry used “externally” (in problems without obvious algebraic structure).

10

Separable and algebraic closures?