bio  website  math.upsud.fr/~chambert 

location  Université ParisSud (Orsay)  
age  43  
visits  member for  4 years, 6 months 
seen  31 mins ago  
stats  profile views  2,910 
20h

answered  A proof from Lang's undergraduate analysis 
Oct 17 
answered  Equidistribution of rational points on an algebraic variety 
Oct 17 
answered  Proofs of the uncountability of the reals. 
Oct 16 
revised 
About the hypothesis of Zorn's lemma
Adding a summary of comments. 
Oct 16 
awarded  Revival 
Oct 16 
answered  Categorifications of Zorn's lemma 
Oct 16 
asked  About the hypothesis of Zorn's lemma 
Oct 6 
comment 
Why do roots of polynomials tend to have absolute value close to 1?
I don't agree, for two reasons. 1) Partial sums furnish nice sequence of polynomials. 2) There is a generalization of JentzschSzegö where the limit behaviour of the zeroes can be more general (see the book of AndrievskiiBlatt, or a paper of mine, dx.doi.org/10.1142/S1793042111004691, where I discuss a generalization to Riemann surfaces of arbitrary genus). 
Oct 5 
comment 
Why do roots of polynomials tend to have absolute value close to 1?
A theorem of JentzschSzegö gives a result in a similar spirit. 
Sep 30 
comment 
Vanishing of the module of differentials of a extension of perfect fields
My impression is that the indicated maps from the tensor products do not exist. Am I wrong? 
Sep 30 
awarded  Explainer 
Sep 28 
comment 
Equivalence of definitions of the Milnor $K$groups
Math is like litterature or philosophy. One should never forget to study the classics! 
Sep 28 
comment 
Galois groups and prescribed ramification
You're right. Knowing that it splits allows to understand precisely those extensions which are regular, is contain no nontrivial extension of the finite ground field. 
Sep 26 
answered  Equivalence of definitions of the Milnor $K$groups 
Sep 26 
comment 
Galois groups and prescribed ramification
(followed) : It thus seems that the Galois group of any extension of $k(X)$ which is unramified above $X$ is generated by $2g+r$ elements. 
Sep 26 
comment 
Galois groups and prescribed ramification
I'm not really sure of the following argument, but let's try something. If $X$ is an affine curve over a field $k$, and $\overline X$ is the base change to an algebraic closure $\overline k$, there is an exact sequence of fundamental groups, which is split if $X$ has a $k$rational point: $1\to \pi_1(\overline X)\to \pi_1(X) \to \mathop{\rm Gal}(\overline k/k)\to 1$. It follows that $\pi_1(X)$ is the direct product of $\widehat{\mathbf Z}$ with a profinite free group on $2g+r1$ generators. 
Sep 25 
answered  Galois groups and prescribed ramification 
Sep 23 
comment 
Minimum of two plurisubharmonic functions
In the real case, take $D=\mathopen]1;1\mathclose[$, $u(x)=x$ and $v(x)=x$. One has $\Phi(x)=x$, $\Phi_{\partial D}=1$ hence $\Phi(x)>\sup_{\partial D}\Phi$ for every $x\in D$. 
Sep 22 
comment 
Minimum of two plurisubharmonic functions
It suffices that min {u,v} = u everywhere. More seriously (it is easier to visualize the real analogue of convex functions), if $u$ and $v$ are distinct linear functions on the real line and $x\in\mathbf R$ is such that $u(x)=v(x)$, then $\min\{u,v\}$ is concave and is not convex. 
Aug 4 
comment 
Connections between Standard, Hodge and Tate conjectures on algebraic cycles?
The Tate conjecture furnishes $\mathbf Q_\ell$linear combinations of cycles. Is it enough? 