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57Jimmy's user avatar
57Jimmy's user avatar
57Jimmy
  • Member for 7 years, 10 months
  • Last seen this week
12 votes
1 answer
3k views

Quasi-inverse of an equivalence of categories is unique up to unique isomorphism

11 votes
3 answers
589 views

How does passing to ideals solve the problem of unique factorization?

10 votes
1 answer
975 views

Confusion about genus-degree formula

9 votes
2 answers
1k views

Injectivity, surjectivity and pullback diagrams

8 votes
1 answer
2k views

The orthogonal group $O(q)$ associated with a quadratic form $A$

7 votes
1 answer
196 views

Matrix with permutations of $\{1,\dots,n\}$ is invertible

7 votes
1 answer
1k views

Different definitions of closed differential form

6 votes
3 answers
718 views

Zero element of Ext$^n$ groups

6 votes
1 answer
183 views

Geodesic quadrangles in CAT($0$) spaces

6 votes
1 answer
119 views

Tensor product and dual of $k$-vector spaces over a $k$-algebra: what is the dimension?

5 votes
0 answers
174 views

Which line bundle on $A$ is the pull-back of the Poincaré bundle via a given morphism $A \to A^*$?

5 votes
1 answer
205 views

Modules over the dual of an infinite dimensional coalgebra

5 votes
0 answers
130 views

Homology of Fermat curve

4 votes
2 answers
261 views

Tensor product that is not $0$

4 votes
1 answer
2k views

Factor theorem for multiple variables

4 votes
1 answer
208 views

Fibered surface is flat if and only if it surjects onto the base

4 votes
0 answers
53 views

Is a tensor product of subquotients a subquotient of the tensor product?

3 votes
2 answers
91 views

Power of simple object cannot be a proper subobject of itself

3 votes
1 answer
63 views

Structure sheaf of a locally ringed space can be pulled back from an open cover

3 votes
0 answers
50 views

Database for properties of categories

3 votes
1 answer
1k views

Manifold as zero locus of smooth functions

3 votes
1 answer
1k views

Representations and representable functors

3 votes
2 answers
300 views

Jump of dilogarithm

3 votes
1 answer
156 views

Correct definition of singular homology

3 votes
1 answer
183 views

A non-positively curved cube complex that admits a local isometric embedding into a Salvetti complex is special.

3 votes
2 answers
469 views

Minimal sphere around a polyhedron

3 votes
1 answer
91 views

Two questions regarding quotients and fraction fields of polynomial rings

3 votes
1 answer
813 views

Can find common principal open subsets in the intersection of two open affine subschemes

3 votes
1 answer
70 views

Special $k$-algebra is finitely generated

3 votes
0 answers
28 views

Why can't closed subschemes be defined in an easier way?