Pavel Čoupek's user avatar
Pavel Čoupek's user avatar
Pavel Čoupek's user avatar
Pavel Čoupek
  • Member for 10 years, 10 months
  • Last seen more than 1 year ago
24 votes
2 answers
11k views

Deck transformations of universal cover are isomorphic to the fundamental group - explicitly

20 votes
1 answer
2k views

Is there a group which has precisely all finite groups as subgroups?

13 votes
1 answer
2k views

Projective closure of an algebraic curve as a compactification of Riemann surface

12 votes
1 answer
975 views

Is there an interpretation of higher cohomology groups in terms of group extensions?

8 votes
1 answer
1k views

When does the tensor product consist of elementary tensors only?

8 votes
1 answer
507 views

Construction(s) of new integral domains from "old ones"

8 votes
1 answer
246 views

Is $\pi_1^{et}(\mathrm{Spec}\, k) \simeq \mathrm{Gal}(k^{sep}/k)$? (confusion about profinite completions)

8 votes
1 answer
818 views

Is there a "unifying framework" for harmonic analysis?

7 votes
1 answer
986 views

Homotopy category of chain complexes as a localization

7 votes
2 answers
262 views

Are varieties cocomplete?

7 votes
3 answers
1k views

(Certain) colimit and product in category of topological spaces

5 votes
1 answer
230 views

Is $\coprod \subseteq \prod$ true in any (complete cocomplete) Abelian category?

5 votes
0 answers
1k views

Surjectivity of a map on inverse limits

4 votes
1 answer
160 views

When do (universal-algebraic) varieties have (enough) injectives?

4 votes
1 answer
467 views

Abstract nonsense proof that stalks of $\mathcal{O}_X$ modules are modules over $\mathcal{O}_X$-stalks

4 votes
1 answer
252 views

Morita equivalence: Is $_{\mathrm{End}_R(P)}P$ projective if $P_R$ is?

4 votes
1 answer
394 views

Given a balanced bimodule $_SP_R$, is $R$ isomorphic to $\text{Hom}_S(P,P)$?

3 votes
1 answer
222 views

Orbits of $\mathbb{Z}_n^{*}$ acting on a set $\mathbb{Z}_n$

3 votes
3 answers
1k views

Class of algebras defined by quasi-identities is not closed under taking the quotients

3 votes
1 answer
198 views

$\mathrm{Pol}_m(\mathbb{A})$ viewed as a relation pp-definable from $\mathbb{A}$

3 votes
1 answer
374 views

How do endomorphisms of Banach space modulo compact operators look like?

3 votes
0 answers
116 views

(stability-theoretic) ¨weakly normal groups" are closed under subgroups

3 votes
0 answers
83 views

How much information about $R-\mathrm{Mod}$ can be extracted from $\underline{R-\mathrm{Mod}}$ and $K_0(R)$?

3 votes
0 answers
207 views

Infinite primes (places) of a number field geometrically

2 votes
0 answers
492 views

Rational points of conics over $\mathbb{Q}$

2 votes
0 answers
116 views

"Fourier coefficients" of a sequence of uniformly Lipschitz functions

2 votes
1 answer
164 views

Are poset-shaped limits of finite groups profinite?

2 votes
1 answer
119 views

Non-injective affine quasi-coherent module induced by injective module over the global sections??

2 votes
1 answer
257 views

Is the image of $\mathrm{Spec}(\varphi)$, where $\varphi$ is a localization, always open?

2 votes
1 answer
718 views

Is a geodesic always regular?