2,417 reputation
1523
bio website math.unibas.ch/~blanc
location Basel
age 32
visits member for 1 year, 11 months
seen 14 mins ago

I am working mostly in birational geometry, especially in studying Cremona groups.


Apr
15
comment Degree and quasi projective family
What is the definition of $V_p$ ?
Apr
9
reviewed Approve suggested edit on Interpretation of the integral “with respect to a plane wave” in terms of Radon transform
Apr
9
reviewed Approve suggested edit on Inversion of Radon transform by incomplete data: specific case
Apr
9
reviewed Approve suggested edit on Choosing the order of Tikhonov regularization of an inverse problem
Apr
4
comment When is a blow-up of $\mathbb{P}^2$ a Mori Dream Space?
Good reference. And in the article they explain that this works if $(K_X)^2>0$ or for some cases where $(K_X)^2<=0$.
Apr
4
comment When is a blow-up of $\mathbb{P}^2$ a Mori Dream Space?
Another remark: if $k\ge 9$, then there are not always infinitely many $(-1)$-curves: take for example $k$ points on a line. A $(-1)$-curve distinct from the $k$ curves obtained is $C=dH-\sum a_i E_i$ and since $C^2=-1$, $CK=-1$, we have $3d-\sum a_i=-1$, and the intersection with the strict transform of the line is $0\le d-\sum a_i=-1-2d$. Hence, we have exactly $k$ $(-1)$-curves on the surface.
Apr
3
comment An affine singular surface
Nice way of seeing it. For me it is "less familiar" but certainly "more familiar" for others. Hence it is good to have both ways.
Apr
3
comment When is a blow-up of $\mathbb{P}^2$ a Mori Dream Space?
One remark: if $k\le 8$, then $-K_X$ is not always nef (think of $4$ points on a line for instance). What happens if $k\le 8$ and $-K_X$ is not ample? Is $X$ always a MDS? Is this just because $-K_X$ is big?
Apr
2
comment Compactification of the affine space with a del Pezzo surface
Do you have some similar formulas when the singularities are mild?
Apr
2
reviewed Approve suggested edit on Induced graphs of cayley graph
Apr
2
comment Compactification of the affine space with a del Pezzo surface
Thanks, nice remark. I was also thinking that smooth was too much.
Apr
2
asked Compactification of the affine space with a del Pezzo surface
Apr
2
comment NP-hard problems in linear algebra and real analysis
Proving a conjecture is maybe a hard thing, but has nothing to do with the word "hard" of "NP-hard", as Noah S explained. Hence, talking about Riemann hypothesis in this context is quite weird.
Apr
2
answered An affine singular surface
Apr
1
comment Arithmetic property of a surface of general type
If you take $P$ and $Q$ of small degree (for example of degree $1$), your surface $z^2=P(x)Q(y)$ is of course rational. That's why I asked what you assume on $P$, $Q$ to say that your variety is of general type.
Apr
1
comment Arithmetic property of a surface of general type
How much is your degree $d$? If too small, the variety is certainly not of general type. Why do you think that you dont have rational curves on the surface?
Apr
1
reviewed Approve suggested edit on What groups have a second maximal subgroup below exactly four maximal subgroups?
Mar
30
reviewed Approve suggested edit on What groups have a second maximal subgroup below exactly four maximal subgroups?
Mar
30
comment Non existence of cyclic infinite linear algebraic groups
Yes, I agree with Jason Starr, I still do not understand the details.
Mar
29
comment Hirzebruch's ICM talk
At least the title means "complex manifolds"... but you probably know it since you tagged it :-)