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Alex Mathers's user avatar
Alex Mathers's user avatar
Alex Mathers's user avatar
Alex Mathers
  • Member for 9 years, 2 months
  • Last seen this week
35 votes

What is an easy example of non-Noetherian domain?

27 votes
Accepted

What is the use of the chain rule?

25 votes
Accepted

What is the original source of "fiber" in mathematics?

20 votes

How does advancing through the math major work?

15 votes
Accepted

Are basis elements of a topology always open?

13 votes
Accepted

$48$ reasons why a matrix is singular

11 votes
Accepted

$V$ finite-dimensional vector space and isomorphic to $\mathbb{R}^n$?

11 votes

Why do mathematicians use $\oplus$ instead of $+$?

11 votes
Accepted

Sum of two subspaces is equal to the span of their union

11 votes
Accepted

Direct sum and Hom

11 votes
Accepted

A prime ideal $\mathbf{p}$ "lying above" a prime p

11 votes
Accepted

End(M) for cyclic R-module M is a commutative ring where R is a PID.

10 votes
Accepted

Proper clopen subset of disconnected set

10 votes
Accepted

Why global sections of Sheaf Hom is Hom?

10 votes

Is left shift operator compact?

9 votes
Accepted

What is the difference between the identity functor and the identity morphism?

9 votes
Accepted

Finite union of affine schemes

8 votes
Accepted

$G$ infinite where every non trivial proper subgroup is maximal, show $G$ is simple

8 votes
Accepted

Did I pick the error? Mathematical Logic

8 votes
Accepted

A nilpotent matrix A implies AB is nilpotent?

7 votes
Accepted

How can $\mathbb{R}/\mathbb{Z}$ be a free $\mathbb{R}$-module?

7 votes

Line bundles over $\Bbb P^1_k$

7 votes
Accepted

Is it true that $\mathscr{O}_{X,x}=\mathscr{O}_{\operatorname{Spec} A,x}$ for any $\operatorname{Spec} A$ with $x\in\operatorname{Spec} A$?

7 votes
Accepted

Prove isomorphism of rings using Yoneda lemma

7 votes
Accepted

"Easy" proof that $\Phi_n$ has degree $\phi_n$

7 votes
Accepted

Is the topologist's sine curve a manifold?

7 votes

Proof of the derivative of $\ln(x)$

7 votes
Accepted

Calculating Ext and Tor for $\mathbb Z/m\mathbb Z$ and $\mathbb Z/n\mathbb Z$

7 votes
Accepted

free vector space of the product space

7 votes
Accepted

For a ring $R$, $x^2=x$ for all $x\in R$ implies...

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