93

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4
A Beck-Chevalley type condition
11
Non-examples of model structures, that fail for subtle/surprising reasons?
3
Why every complex of injectives is homotopically injective (provided that, the injective dimension is finite)?
5
Is this square a push-out square?
1
example re torsionless quotients of abelian groups
4
Homotopy excision and homotopy pushout
7
Commutativity of Tor
3
A statement for a subset generated a triangulated category
6
Categorical description of the second K-group
10
Morphisms between $K_0$
5
When is this braiding not a symmetry?
1
Universality of Ext functor using Yoneda extensions
15
Ring with three binary operations
3
Groups lying horizontally in 2-groups
8
Is the derived category of abelian groups a subcategory of the stable homotopy category?
4
Example: a pair of nonisomorphic parallel morphisms with isomorphic cones
3
Irreducible cohomology theories
11
An isomorphism between different Ext’s coming from group cohomology
4
A lost lemma about periodicity in a grid of long exact sequences?
4
Recovering torsion in singular homology from cplx of singular chains
3
Exact sequences
5
Are filtered colimits of weak-equivalences of spectra again weak-equivalences?
2
Chain Condition on Rings
6
Projective arrows
8
Fubini theorem for hocolim.
6
Determining homotopy classes [T^2, RP^2]
1
Small categories and completeness
4
Whitehead product with identity on homotopy groups of spheres
1
Projective dimension of cohomology over regular rings
2
Non-quasi-abelian braided crossed modules
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