4,425 reputation
1532
bio website math.berkeley.edu/~achinger
location Berkeley
age 28
visits member for 5 years, 2 months
seen 5 hours ago
PhD student, UC Berkeley

Apr
11
reviewed Approve Intuition for Integral Transforms
Apr
11
comment Interpreting Frobenius pullback as an invariant differential in the case of an elliptic curve
Is $S$ affine? / Shouldn't $H^1(E, \mathcal{O}_E)$ be $R^1 f_* \mathcal{O}_E$? If $E=S$, we should have ${\rm Lie}(E/S)=0$...
Mar
26
awarded  Self-Learner
Mar
21
comment Is the ring $\mathbb{Z}_p [[x]]\otimes_{\mathbb{Z}_p} \overline{\mathbb{Q}}_p$ Noetherian?
Brilliant! Thank you.
Mar
21
accepted Is the ring $\mathbb{Z}_p [[x]]\otimes_{\mathbb{Z}_p} \overline{\mathbb{Q}}_p$ Noetherian?
Mar
17
revised Is the ring $\mathbb{Z}_p [[x]]\otimes_{\mathbb{Z}_p} \overline{\mathbb{Q}}_p$ Noetherian?
added 5 characters in body; edited title
Mar
17
asked Is the ring $\mathbb{Z}_p [[x]]\otimes_{\mathbb{Z}_p} \overline{\mathbb{Q}}_p$ Noetherian?
Mar
13
comment Covering of schemes and flatness
The normalization of a cuspidal curve is a bijective finite map which is not flat.
Feb
19
comment Artin approximation of a diagram
What do you mean by approximate? Whether there exists a $\phi'$ in some etale neighborhoods inducing $\phi$ upon completion? Then the answer is no as we can take $Z$ to be a point, $(X, x)=(\mathbb{A}^1, 0)$, $(Y, y) = (\mathbb{A}^1, 1)$ and $\phi = \exp$. Or approximate up to order $N$ for any given $N$? Then I think the answer is yes, because we can apply approximation to the graph of $\phi$.
Feb
9
comment Definition and sigularity of Ramified covers
In general the cyclic cover will be ramified everywhere on $D$, so if $D\cap {\rm Sing}(X)$ is big there is no hope.
Feb
9
comment Definition and sigularity of Ramified covers
Be careful, because the cyclic covers as defined need not be normal if $D$ is non-reduced: in the simple example $X=\mathbb{A}^1$, $D=2\cdot (x)$ the recipe gives the non-normal $\tilde X = {\rm Spec}(k[x,y]/(x^2-y^3)$. But it's easy to compute the normalization, which is ${\rm Spec_X} \bigoplus_{i=0}^{n-1} \mathcal{O}_X(\lfloor \frac{i}{n}D \rfloor)$.
Feb
6
awarded  Yearling
Feb
2
awarded  Popular Question
Feb
1
comment Reference request: log Fano varieties
What if $X$ is not projective?
Jan
29
awarded  Popular Question
Jan
13
comment Intersections of $B$ and $B^-$ orbits in the flag variety $G/B$
It is also stated there that their closures are Cohen-Macaulay, so in particular they are equi-dimensional.
Jan
13
comment Intersections of $B$ and $B^-$ orbits in the flag variety $G/B$
I think they are called (open) Richardson varieties. Their dimensions are described here: arxiv.org/pdf/1008.3939v2.pdf (page 2).
Jan
12
awarded  Guru
Jan
8
comment Is there a “simplification” functor in algebraic topology?
Universal in the homotopy category, I presume?
Jan
8
awarded  Taxonomist