User roger123

45 votes

8 answers

14k views

How should one think about sheafification and the difference between a sheaf and a presheaf

asked Nov 7, 2010 at 21:12

39 votes

3 answers

6k views

Why do finite homotopy groups imply finite homology groups?

asked Dec 20, 2009 at 11:41

30 votes

12 answers

14k views

Why are tensors a generalization of scalars, vectors, and matrices?

asked Mar 18, 2010 at 11:52

19 votes

3 answers

5k views

What determines a model structure?

asked Jun 26, 2010 at 19:14

17 votes

2 answers

3k views

Why does homotopy behave well with respect to fibrations and homology with respect to cofibrations?

asked Feb 24, 2011 at 21:09

16 votes

4 answers

1k views

Algebraic analogue of the Moebius bundle over the circle

asked Nov 9, 2010 at 16:46

14 votes

2 answers

2k views

Galois theory and rational points on elliptic curves

asked Dec 16, 2009 at 14:26

13 votes

2 answers

2k views

Galois group of a product of polynomials

asked Feb 8, 2010 at 20:11

13 votes

2 answers

3k views

Wikipedia's definition of 'locally free sheaf'

asked Nov 4, 2010 at 16:08

11 votes

1 answer

2k views

K-theory as a generalized cohomology theory

asked Mar 17, 2010 at 18:49

11 votes

2 answers

1k views

Geometric motivation for the Stanley-Reisner correspondence

asked Dec 8, 2010 at 22:51

11 votes

1 answer

944 views

Analogue to Serre spectral sequence for cofiber sequences and homotopy

asked Mar 4, 2011 at 21:25

10 votes

4 answers

1k views

Singular complex = cohomology ring + Steenrod operations?

asked Feb 18, 2011 at 9:11

8 votes

2 answers

483 views

Swan-like theorem and covering spaces

asked Oct 27, 2010 at 12:45

8 votes

3 answers

5k views

Why must one sheafify quotients of sheaves?

asked Mar 23, 2010 at 16:16

7 votes

2 answers

419 views

Relation between $KO$ and $K$

asked Mar 16, 2010 at 10:12

6 votes

2 answers

2k views

Understanding the product in topological K-theory

asked Jan 28, 2010 at 20:32

6 votes

2 answers

976 views

Question on a theorem of Eisenbud's and Harris' "The geometry of schemes"

asked Mar 22, 2010 at 13:09

6 votes

3 answers

1k views

Why are spectra indexed over the natural numbers?

asked Sep 8, 2010 at 22:42

6 votes

1 answer

2k views

Question on the interpretation of a presheaf category as a co-completion

asked Mar 24, 2011 at 23:26

6 votes

1 answer

800 views

What kind of colimits are preserved by a certain Yoneda embedding?

asked Dec 16, 2010 at 15:07

5 votes

3 answers

2k views

The correspondence between affine vector bundles and f.g. projective modules

asked Nov 2, 2010 at 18:10

4 votes

3 answers

3k views

Internal hom of sheaves

asked Mar 16, 2010 at 10:54

3 votes

1 answer

473 views

Closure of the homotopy relation for a simplicial set

asked Jun 26, 2010 at 18:58

2 votes

3 answers

2k views

Distributivity / commutativity of pushouts and pullbacks

asked Nov 16, 2010 at 13:13

1 vote

1 answer

326 views

Is there a map of spectra implementing the inverse of the Thom isomorphism?

asked Aug 26, 2011 at 8:28

1 vote

1 answer

963 views

Question on an exercise in Hartshorne: Equivalence of categories

asked Mar 23, 2010 at 12:28

0 votes

1 answer

386 views

The functor of continuous functions from compact CW-spaces to the reals

asked Oct 28, 2010 at 14:01

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28 Questions

How should one think about sheafification and the difference between a sheaf and a presheaf

Why do finite homotopy groups imply finite homology groups?

Why are tensors a generalization of scalars, vectors, and matrices?

What determines a model structure?

Why does homotopy behave well with respect to fibrations and homology with respect to cofibrations?

Algebraic analogue of the Moebius bundle over the circle

Galois theory and rational points on elliptic curves

Galois group of a product of polynomials

Wikipedia's definition of 'locally free sheaf'

K-theory as a generalized cohomology theory

Geometric motivation for the Stanley-Reisner correspondence

Analogue to Serre spectral sequence for cofiber sequences and homotopy

Singular complex = cohomology ring + Steenrod operations?

Swan-like theorem and covering spaces

Why must one sheafify quotients of sheaves?

Relation between $KO$ and $K$

Understanding the product in topological K-theory

Question on a theorem of Eisenbud's and Harris' "The geometry of schemes"

Why are spectra indexed over the natural numbers?

Question on the interpretation of a presheaf category as a co-completion

What kind of colimits are preserved by a certain Yoneda embedding?

The correspondence between affine vector bundles and f.g. projective modules

Internal hom of sheaves

Closure of the homotopy relation for a simplicial set

Distributivity / commutativity of pushouts and pullbacks

Is there a map of spectra implementing the inverse of the Thom isomorphism?

Question on an exercise in Hartshorne: Equivalence of categories

The functor of continuous functions from compact CW-spaces to the reals