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olivier dot begassat dot cours at gmail dot com


1d
revised Prove that $\{\frac{\phi (n)}{n}\}_{n \in \Bbb N}$ is dense in $[0,1]$
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1d
answered Prove that $\{\frac{\phi (n)}{n}\}_{n \in \Bbb N}$ is dense in $[0,1]$
1d
comment differential inequality implies zero function
The $\epsilon$ at the end seems a little out of place.
1d
comment differential inequality implies zero function
By twice differentiable do you mean merely twice differentiable, or do you require $f''$ to be continuous aswell?
Dec
19
awarded  Constituent
Dec
19
comment Where does the proof for commutative rings break down in the non-commutative ring when showing only two ideals implies the ring is a field?
The first point is not a consequence of Zorn's lemma! It's a straight forward proof from scratch. No axiom of choice needed.
Dec
19
answered How to find lagrangian submanifolds.
Dec
19
reviewed Approve Which convex $2n$-gons have symmetry group $D_n$ instead of $D_{2n}$?
Dec
19
reviewed Leave Open Proving function in real analysis
Dec
19
comment 2-dimesional cell complexes with fundamental group isomorphic to the following.
@Dan Oh I see.${}$
Dec
19
comment 2-dimesional cell complexes with fundamental group isomorphic to the following.
Thanks @Dan! What was your solution for such a space?
Dec
19
revised 2-dimesional cell complexes with fundamental group isomorphic to the following.
added 90 characters in body
Dec
19
answered 2-dimesional cell complexes with fundamental group isomorphic to the following.
Dec
17
awarded  algebraic-topology
Dec
15
comment Map from $n$-sphere to $n$ dimensional torus
@MikeEarnest No problem : )
Dec
15
answered Map from $n$-sphere to $n$ dimensional torus
Dec
15
comment If a linear transformation $T$ has $z^n$ as the minimal polynomial, there is a vector $v$ such that $v, Tv,\dots, T^{n-1}v$ are linearly independent
Hint: if such a $v$ exists, it can't be in in $\ker(T^{n-1})$...
Dec
15
comment Spectrum of left shift operator $L\in B(H)$
@student There is more to invertibility in infinite dimensions (i.e. in an infinite dimensional Banach space) than kernel=0. You also have to be surjective, which is a separate condition.
Dec
12
revised Showing that $F^*(L_{\mathbb{Y}}\omega)=L_{\mathbb{X}}(F^*\omega)$
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Dec
12
comment Showing that $F^*(L_{\mathbb{Y}}\omega)=L_{\mathbb{X}}(F^*\omega)$
Just plug in $k-1$ vector fields on both sides, and see for yourself.