bio  website  math.stanford.edu/~church 

location  Stanford  
age  
visits  member for  5 years, 7 months 
seen  2 hours ago  
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2d

comment 
Searching for $C^*$
This is clearly a question of interest to research mathematicians (indeed uniquely to research mathematicians). 
May 21 
comment 
Will this be a case of self plagiarism or will it annoy the referee?
I'm voting to close this question as offtopic because it belongs on academia.stackexchange.com (and was also asked there: academia.stackexchange.com/questions/45754/…) 
May 16 
comment 
Generalize $\pi_0(B\mathcal{C})\cong\{\text{objects}\}/\{\text{morphisms}\}$ to categories internal to topological spaces
The proof you give is not correct. Consider the category $x\rightarrow y\leftarrow z$. There is a path in $B\mathcal{C}$ from $x$ to $z$, but there is no morphism in $\mathcal{C}$ from $x$ to $z$. This contradicts your claim "which means that there is a morphism between x0 and x1"; the mistake seems to be in the earlier claim "yields a path ... but as $N_1(\mathcal{C}) is discrete, it is constant". As Zhen Lin points out, the correct deduction is that there is a zigzag of morphisms from $x_0$ to $x_1$. 
Apr 29 
comment 
Continuous maps to fat geometric realizations of simplicial spaces
Note there is a typo in the statement of Segal's Proposition 4.1: it should say that $\text{pr}\colon BX_U\to X$ is a homotopy equivalence, not $BR_U\to X$. 
Apr 28 
awarded  Revival 
Mar 25 
reviewed  Approve Can an abelian variety/Q have no nontrivial points over Q_sol? 
Mar 24 
reviewed  Approve Mal'cev “rational equivalence” and model theory 
Mar 18 
reviewed  Approve hyperbolic metrics 
Mar 15 
answered  Does there exist a fibre bundle $K(\mathbb{Z}_4,1)\rightarrow K(\mathbb{Z}_2,1)$ with fiber $K(\mathbb{Z}_2,1)$? 
Mar 6 
answered  Maryam Mirzakhani's works 
Mar 6 
reviewed  Approve latex tag wiki 
Feb 26 
comment 
$G_\mathbb{Z}$homotopy type of rational Tits building $\Delta_{G, \mathbb{Q}}$
@J.Martel: We're considering the usual cellular homology of these buildings with integer coefficients, without interference from any groups at all. 
Feb 26 
revised 
$G_\mathbb{Z}$homotopy type of rational Tits building $\Delta_{G, \mathbb{Q}}$
add reference to paper arXiv:1501.01307, now that it is posted 
Feb 26 
reviewed  Approve matrixtheory tag wiki excerpt 
Feb 24 
awarded  Excavator 
Feb 24 
revised 
Example of a Group which has $\text{SL}_{n}(\mathbb{Z})$ as the automorphism group
added Oliver Baues to author list (and added links to arXiv, MathReviews and journal) 
Feb 3 
reviewed  Leave Open Is there any Lefschetzlike principle for representations of finite groups? 
Feb 3 
reviewed  Leave Open Direct product of filters 
Feb 3 
reviewed  Leave Open Propositional logic: Minimal set of formulas, which is consistent and complete 
Feb 3 
reviewed  Leave Open integral or rational cohomology of real grassmannians 