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X.T Chen

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20 votes

Why the sphere spectrum is more correct than $\mathbb{Z}$?

at.algebraic-topology stable-homotopy-category chromatic-homotopy asked Nov 4, 2022 at 5:58
mathoverflow.net

13 votes

Seek for a algebro-geometric proof: the group homomorphism $\mathrm{SL}(2,\mathbb{Z}) \rightarrow \mathrm{SL}(2,\mathbb{Z}/N\mathbb{Z})$ is surjective

ag.algebraic-geometry linear-algebra arithmetic-geometry asked May 12, 2021 at 13:20
mathoverflow.net

10 votes

Is there a strictly increasing differentiable function maps positively measurable set to zero measure set?

real-analysis measure-theory asked Feb 24, 2020 at 12:10
mathoverflow.net

8 votes

How to prove the existence and uniqueness of the solution of a second order linear ODE?

differential-equations analysis asked Dec 24, 2018 at 5:18
math.stackexchange.com

8 votes

$f$ is monotonically increasing, $0 \le f \le 1$ and $\int_0^1 (f(x) - x) dx = 0$ then $\int_0^1|f(x)-x|dx \le \frac{1}{2}$.

analysis asked Apr 15, 2019 at 13:20
math.stackexchange.com

7 votes

An example that Čech cohomology is not equal to derived cohomology with on an affine scheme with Zariski topology.

algebraic-geometry commutative-algebra sheaf-cohomology asked Oct 16, 2021 at 3:38
math.stackexchange.com

6 votes

Hartshorne's Exercise II.4.5(c). A third time.

algebraic-geometry schemes asked Nov 4, 2020 at 8:27
math.stackexchange.com

6 votes

If $f^2(t) \le 1+2\int_0^tf(s)\mathrm{d}s$ prove $f(t)\le 1+t$

analysis inequality integral-inequality asked Mar 17, 2019 at 9:31
math.stackexchange.com

5 votes

Concrete computation of pullback of the $D$-module $\mathbb{C}[t,t^{-1}]$

ag.algebraic-geometry d-modules geometric-representation-theory asked Mar 26, 2022 at 7:27
mathoverflow.net


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