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2d
awarded  Good Answer
Mar
17
awarded  Nice Answer
Mar
7
comment Hochschild cohomology of the skew group ring D(X)#G in the complex analytic case
It would probably be a good idea to tell us what $D(X)$ is.
Mar
7
comment Replacing functors by topologically or simplicially enriched functors
«Do you really care about Top?» is a great line :-)
Mar
4
awarded  Nice Answer
Mar
2
awarded  Disciplined
Feb
27
comment Defining the cup product in Ext using a Kunneth formula
I'd say that if you really know how to lift cocycles to chain maps in an example, you also know how to write down the diagonal map :-)
Feb
27
comment Defining the cup product in Ext using a Kunneth formula
Sometimes, yes (specially when you only need to compute a few products, rather than the whole thing) but the reduction ofmcup products to conputations in the derived category is not a reduction, as the Principle of Conservation of Difficulty kicks in.
Feb
15
awarded  Popular Question
Feb
12
comment space at the Planck scale
That naive attempt at combining the two ideas is way too naive!
Feb
5
awarded  Nice Answer
Jan
29
comment How many geometric structures on manifolds are there?
You should probably make explicit what makes your question different from «what are the coverings of linear Lie groups?» which is what the comments are converging to.
Jan
28
comment Categorical proof subgroups of free groups are free?
The same is true of free Lie algebras: they are those of global dimension 1.
Jan
23
comment Proofs without words
If you cannot tell the difference between a proof-tree and a proof without words in the tradition of, say, the AMM Monthly, then that is clearly a limitation of yours. I would rather you start a meta thread, or a blog, instead of further polluting this thread with what is clearly rather orthogonal chatter.
Jan
23
comment Proofs without words
@goblin, I am afraid that you have completely misunderstood the concept. The idea is pictures which have the rather amazing capability of immediately suggesting on the mind of the viewer the idea of a proof. How on earth you managed to get from the rather well-known idea involved in this question to «proofs without logic» is a mystery to me.
Jan
9
awarded  Nice Answer
Dec
30
comment Localizations or quotients of categories?
@FilippoAlbertoEdoardo, consider an antisimmetric category (so that for distinct objects $x$ and $y$ at most one of the sets $\hom(x,y)$ and $\hom(y,x)$ is nonempty,and there are no nonidentity endomorphisms) and consider the equivalence relation which identifies all elements in each nonempty $\hom$ set. This is not a lozalization, because there are no isomrphisms in the resulting category.
Dec
16
comment Defining the cup product in Ext using a Kunneth formula
The cup product is just the composition of maps in the derived category. If you want to actually compute, that's not very helpful, though.
Dec
13
awarded  Nice Answer
Dec
12
awarded  Great Answer