5,640 reputation
1943
bio website math.stanford.edu/~church
location Stanford
age
visits member for 5 years, 9 months
seen Jul 29 at 21:06

Jul
17
comment The evaluation fibration of a transitive, effective topological group action
Do you mean "fibration" or "fiber bundle"? en.wikipedia.org/wiki/Fibration en.wikipedia.org/wiki/Fiber_bundle
Jul
17
comment Properties of loop space functor from homotopy types to group objects in homotopy types
I'm not an expert in any of this material, but it seems to me that it might be helpful to learn about classifying spaces before jumping to $(\infty,1)$-categories.
Jul
17
comment When to postpone a proof?
Your Example 1 is dragging this discussion in the wrong direction, since everyone is going to agree with it: who would object to stating the main theorems in the introduction? The real question is about the structure of arguments within the body of the paper, and when it is appropriate to postpone a proof there. This is an important question, which too many authors neglect to think about when outlining their papers; I hope we'll get to hear a discussion on this point.
Jul
13
reviewed Approve Why is the fundamental group of a compact Riemann surface not free ?
May
27
reviewed Approve The possibility of a symmetric difference in a torsion-free group
May
24
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 off-topic 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 non-trivial 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 matrix-theory tag wiki excerpt
Feb
24
awarded  Excavator