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10h
asked An example of $K(G,1)$ in Hatcher
Apr
14
asked Showing that the 2-torus is parallelizable
Mar
29
comment Two definitions of attaching are equivalent.
Why not? $X\sqcup Y:=(X\times \{0\}) \cup (Y\times \{1\})$.
Mar
29
asked Two definitions of attaching are equivalent.
Mar
17
asked Why derivations obey chain rule.
Mar
10
comment Simplicial homology of sphere with bars.
Qiaochu, if we regard $S^2$ as a subset of $\mathhbb{R}^3$, then a vertical bar is a bar inside the sphere which is parallel to the $z$-axis with vertices on $S^2$.
Mar
10
asked Simplicial homology of sphere with bars.
Feb
24
asked If $\mathbb{R}^n=U\cup V$ for path-connected $U,V$ then $U\cap V$ is path-connected.
Feb
23
asked When are flag manifolds compact.
Jan
27
asked $\sqrt{I}+\sqrt{J}=R$ implies $I+J=R$
Dec
12
asked Pull-back of a one-form on a sphere.
Dec
2
revised A particular case of Zariski's lemma
added 6 characters in body
Dec
2
asked A particular case of Zariski's lemma
Nov
5
asked Square is not an algebraic set.
Nov
5
asked Inverse image of a maximal ideal under a morphism of finitely generated $\mathbb{C}$-algebras.
Oct
18
asked $\mathbb{Q}_p$ contains a square root of $4p+1$, but not of $4p$.
Oct
13
comment Divisibility of polynomials in a subfield of a field.
maybe I can say that the coefficients of $h$ are obtained from the coefficients of $f$ and $g$ by operations $\pm, \times, /$ and this means that these coefficients have to be in $K$?
Oct
13
asked Divisibility of polynomials in a subfield of a field.
Oct
3
comment Techniques to understand mathematics. What and how?
as little as I have learnt, quite a substantial part of it was through talking to people who do mathematics
Oct
1
accepted The derivative as a linear function