Georges Elencwajg's user avatar
Georges Elencwajg's user avatar
Georges Elencwajg's user avatar
Georges Elencwajg
  • Member for 14 years, 5 months
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151 votes
13 answers
21k views

Why is the fundamental group of a compact Riemann surface not free ?

132 votes
3 answers
20k views

When is the tensor product of two fields a field?

85 votes
7 answers
48k views

How many mathematicians are there?

78 votes
7 answers
11k views

Cubical vs. simplicial singular homology

75 votes
4 answers
6k views

When is a singular point of a variety ($\mathcal{C}^\infty$-) smooth?

75 votes
3 answers
9k views

Does a power series converging everywhere on its circle of convergence define a continuous function?

71 votes
3 answers
7k views

Where do all these projection formulas come from?

65 votes
1 answer
4k views

Did Bourbaki write a text on algebraic geometry?

42 votes
4 answers
3k views

What is the Krull dimension of the ring of holomorphic functions on a complex manifold?

42 votes
6 answers
6k views

Arbitrary products of schemes don't exist, do they?

40 votes
1 answer
3k views

Is every connected scheme path connected?

37 votes
3 answers
2k views

What does it mean geometrically that an element in a domain is irreducible?

35 votes
1 answer
2k views

Mr. G.P.K.'s questions [closed]

34 votes
2 answers
2k views

An algebraic vector bundle is trivialized by open sets. How many does one need?

33 votes
0 answers
2k views

History of the Proj construction in algebraic geometry

31 votes
2 answers
2k views

Should Krull dimension be a cardinal?

28 votes
2 answers
3k views

Is every algebraic smooth hypersurface of affine space parallelizable?

28 votes
1 answer
1k views

Which intrinsic invariants of a projective variety can you deduce from its Hilbert polynomials?

25 votes
2 answers
4k views

Is a universally closed morphism of schemes quasi-compact ?

23 votes
3 answers
2k views

Which vector spaces are duals ?

22 votes
0 answers
570 views

Are the reals really a fraction field?

21 votes
2 answers
2k views

What is the dimension of the product ring $\prod \mathbb Z/2^n\mathbb Z$ ?

21 votes
3 answers
2k views

Is a complex manifold projective just because its blow-up at a point is ?

21 votes
1 answer
2k views

Are the Stiefel-Whitney classes of a vector bundle the only obstructions to its being invertible?

21 votes
5 answers
1k views

Computation of fraction field of formal series over the integers

21 votes
1 answer
934 views

Can you give an example of two projective morphisms of schemes whose composition is not projective?

19 votes
0 answers
311 views

Can one properly embed a differential manifold into numerical space of double dimension? [duplicate]

17 votes
3 answers
1k views

Did Grothendieck introduce vertical arrows that denote morphisms?

17 votes
1 answer
930 views

Is a direct sum of flabby sheaves flabby?

17 votes
3 answers
1k views

How does one compute the space of algebraic global differential forms $\Omega^i(X)$ on an affine complex scheme $X$?