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olivier dot begassat dot cours at gmail dot com


Apr
14
comment What is the reason for stating Cayley's theorem this way?
Contrary to Seth, I prefer the first statement. The essence of the theorem is that the abstract notion of group encapsulates the more concrete notion of a group of permutations on a set.
Apr
14
comment Homotopy Type of Diffeomorphism Group of Lie Group
You say you can't find any counter examples to this, but what are your examples where this is true? It seems plausible that $\mathrm{Diffeo}^+(S^1)$ should have the homotopy type of $S^1$, and I think it is a theorem that $\mathrm{Diffeo}^+(S^3)$ has the homotopy type of $\mathrm{SO}(4)$. But I don't even know what the homotopy type of $\mathrm{Diffeo}^+(\Bbb R^n)$ should be for $n\geq 2$, and wether it somehow relates to $\mathrm{SO}(n)$ or not. So what is your evidence?
Apr
14
revised Why must a field with a cyclic group of units be finite?
edited body
Apr
14
revised Why must a field with a cyclic group of units be finite?
added 23 characters in body
Apr
14
revised Why must a field with a cyclic group of units be finite?
added 23 characters in body
Apr
14
answered Why must a field with a cyclic group of units be finite?
Apr
14
revised Is the category of these particularly nice spaces cartesian closed?
added 4 characters in body
Apr
14
answered Is the category of these particularly nice spaces cartesian closed?
Apr
13
comment Spelling has deteriorated by the year of 2075, how many spellings are possible?
@IgäriaMnagarka Excellent! Or as we like to say, doubleplusgood!
Apr
13
comment Spelling has deteriorated by the year of 2075, how many spellings are possible?
RLEIIF: welcome to the future.
Apr
12
revised $\textbf{Q}$ fails to prove some correct $\forall$-rudimentary sentence
edited title
Apr
12
asked Homology Whitehead theorem for non simply connected spaces
Apr
12
comment Is a bounded (Riemannian) manifold always totally bounded?
Great example! ${}$
Apr
12
comment Is an onto homomorphism from G to itself an automorphism
Did you mean to write that the circle is an example of an infinite group with a quotient by a finite subgroup isomorphic to itself?
Apr
11
revised Combinatorial definition of the homotopy groups of a quasi category?
added 24 characters in body; edited title
Apr
10
comment Combinatorial definition of the homotopy groups of a quasi category?
@ZhenLin Could you expand on what becomes clear?
Apr
10
asked Combinatorial definition of the homotopy groups of a quasi category?
Apr
6
answered Compute $\lim\limits_{n\to\infty} \int_{0}^{2\pi} \cos x \cos 2x\cdots \cos nx \space{dx}$
Apr
6
comment Is $\nabla_{X}:\Gamma(E) \to \Gamma(E)$ continuos aplication?
OK. ${}{}{}{}{}$
Apr
6
comment Is $\nabla_{X}:\Gamma(E) \to \Gamma(E)$ continuos aplication?
It doesn't go to $\Gamma(E)$...