bio  website  math.berkeley.edu/~achinger 

location  Berkeley  
age  28  
visits  member for  5 years, 1 month 
seen  20 hours ago  
stats  profile views  3,185 
PhD student, UC Berkeley
1d

awarded  SelfLearner 
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 nonreduced: in the simple example $X=\mathbb{A}^1$, $D=2\cdot (x)$ the recipe gives the nonnormal $\tilde X = {\rm Spec}(k[x,y]/(x^2y^3)$. But it's easy to compute the normalization, which is ${\rm Spec_X} \bigoplus_{i=0}^{n1} \mathcal{O}_X(\lfloor \frac{i}{n}D \rfloor)$. 
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 CohenMacaulay, so in particular they are equidimensional. 
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 
Dec 28 
comment 
Coherent sheaves on Proj
Note that q.c. sheaves on $Proj(S)$ are the same as $\mathbb{G}_m$linearized sheaves on $Spec(S)\setminus \{m\}$ where $m = \bigoplus_{n>0} S_n$ is the irrelevant ideal. So you are asking for a criterion for an $S$module $M$ being zero away from $m$. But this is equivalent to asking when $M_x = 0$ for each $x\in m$. So the criterion (for a f.g. module) is: iff $m^k M = 0$ for some $k>0$. This in turn is clearly equivalent to $M$ having only finitely many nonzero degrees. 
Dec 24 
comment 
Blowups of $\mathbb{P}^{n3}$ and $(\mathbb{P}^1)^{n3}$
It is indeed toric  it's the identity on the torus, and the analysis of fans is used to show that it extends to the open orbits of the boundary divisors. 