Mariano Suárez-Alvarez
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1d
comment What's a somewhat fast introduction to (differential) geometry and algebraic topology for someone who knows a lot of analysis but little else?
Read faster. ${}{}$
1d
comment Is the sphere $S^2$ diffeomorphic to a quotient of the square?
You keep saying that X or Y is diffeomorphic to the square, but that only makes sense if you put a differential structure on the square. It does not have a "standard" one (its standard structure is one with corner, and with it it is most certainly not diffeomorphic to a disc), and you have not said which one you have in mind and, much less, you have bothered to give enough details so that the OP and other people with his question know about it.
1d
comment Is the sphere $S^2$ diffeomorphic to a quotient of the square?
@PaulSinclair, That is only the case if you put on the square a differential structure which already has has the corners smoothed. How to do that is not obvious.
2d
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Aug
26
comment Motivation for the Definition of Compact Space
By the time students are exposed to the pure point-set-topology definition of co pactness they should have seen many times situations where compactness is used. If not, then show them that.
Aug
26
answered Motivation for the Definition of Compact Space
Aug
25
comment Is the sphere $S^2$ diffeomorphic to a quotient of the square?
@PaulSinclair, well, a square is not, with its usual structure, a manifold with boundary as it has corners; for that to work you need to smooth the corners first.
Aug
25
comment The second fundamental form of the sphere
The curve is on the sphere!
Aug
25
answered Hamiltonian cycles in associahedron graphs
Aug
24
answered Smooth self maps of compact manifolds.
Aug
24
answered Let $G$ be a compact group. If $\{a^n\}_{n \in \mathbb{Z}}$ is dense in $G$, then $G$ is abelian.
Aug
23
comment Is there a name for complex numbers over affinely extended reals?
That notation has nothing to to with extended anything, really.
Aug
23
comment Is there a name for complex numbers over affinely extended reals?
Is it widely used? I have never seen it used at all, in fact.
Aug
23
comment Is the sphere $S^2$ diffeomorphic to a quotient of the square?
@PaulSinclair, that ther are evident ways to do it does not at all imply that the OP is aware of the fact that this has to be done somehow. Moreover, it is quite non-trivial to actually do it.
Aug
23
comment Proof a regular language by intersection construction
If you want a capital sigma letter us \Sigma, not \sum: the latter is for sums.
Aug
23
comment how to use this maple package for hodge invariant
That there is no other place to ask the question does not turn Math.SE into a good place to ask the question, I am afraid.
Aug
23
comment how to use this maple package for hodge invariant
You should así its authors or in a maple support group. This is mostly offtopic here!
Aug
22
comment What is the interest of duality in algebra, and in general in mathematics?
@Yeldarbskich, you can certainly appreciate the fact that using «the language of category theory» in this context is pretty absurd, no?
Aug
22
comment What is the interest of duality in algebra, and in general in mathematics?
One does not generally «understand a concept in an easy example». What happens is that you get used to the concept by manipulating it in many, many examples. So do that.