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Servaes
  • Member for 12 years, 1 month
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33 votes
2 answers
3k views

Taking the automorphism group of a group is not functorial.

12 votes
1 answer
199 views

Configurations of eleven (or more) points in the Euclidean plane, such that out of any four there is a pair at unit distance.

11 votes
1 answer
3k views

The ring of integers of a number field is finitely generated.

11 votes
1 answer
1k views

When is the tensor product of rings of integers again a ring of integers?

10 votes
1 answer
291 views

On the order of $\mathbb{Z}[X]/(f,g)$ and the resultant $R(f,g)$.

10 votes
2 answers
381 views

Example of an outer automorphism that maps all elements to conjugates.

8 votes
3 answers
2k views

Kernel of $p$-adic logarithm.

8 votes
2 answers
362 views

Does there exist an elliptic curve $E$ such that $\#E(\Bbb{F}_{q^2})=(q+1)^2$ for all prime powers $q$?

8 votes
4 answers
4k views

Layman's proof that the area of a circle of radius $r$ equals $\pi r^2$.

7 votes
1 answer
808 views

Profinite completion is complete.

7 votes
1 answer
429 views

Exercise 24.13 of T. Jech's *Set Theory*

6 votes
2 answers
3k views

For a compact covering space, the fibres of the covering map are finite.

5 votes
1 answer
382 views

Example of rings of the same positive characteristic that do not embed into their tensor product?

5 votes
1 answer
65 views

Ring structure of the units of order $2$ in a monogenic order?

5 votes
1 answer
267 views

Applying the Galvin-Hajnal Theorem?

5 votes
1 answer
141 views

Embedding torsion units of an order into torsion units of the reduced order.

5 votes
1 answer
2k views

Verifying that the weighted projective space $\Bbb{P}_{\Bbb{Q}}(1,1,2,3)$ is singular.

5 votes
1 answer
254 views

Example of a reduced and connected ring that is not a domain?

5 votes
1 answer
176 views

Clarification of answer to "Connectedness of the spectrum of a tensor product"

4 votes
1 answer
147 views

Simpler solution of the Diophantine equation $x^6-y^6=z^2$.

4 votes
1 answer
1k views

Computing the Todd class of projective space.

3 votes
1 answer
561 views

A proof that every projective morphism is proper?

3 votes
1 answer
372 views

Quartic polynomial taking infinitely many square rational values?

3 votes
1 answer
897 views

Galois groups of quintics

3 votes
1 answer
122 views

Primes of the form $p=2a^2-1$ satisfying $p^2=2b^2-1$.

3 votes
1 answer
107 views

Roots of unity in $\Bbb{Z}[X]/(X^2+X+1)^2$

3 votes
2 answers
181 views

If a commutative ring is connected, then its reduced ring is connected.

3 votes
2 answers
413 views

Introduction to group rings (reference request)

3 votes
1 answer
232 views

Simple proof of existence of number field extension with the same roots of unity?

2 votes
0 answers
110 views

Lemma 3.2 of "Catalan's Conjecture" by R. Schoof.