User Fan Zheng

23 votes

Accepted

Proof of $\mathbb{Q}$ is not cyclic

answered Mar 11, 2015 at 3:35

10 votes

Why doesn't the quadratic equation contain $2|a|$ in the denominator?

answered Jun 25, 2018 at 17:27

8 votes

Is the Riemann surface for the square root simply connected?

answered Mar 21, 2015 at 3:49

7 votes

Fundamental group of the special orthogonal group SO(n)

answered Dec 4, 2014 at 16:02

7 votes

Hatcher's example of a pair without the HEP

answered Mar 7, 2015 at 19:41

4 votes

$\mathbb{Z}[x_{1},\dots,x_{n}]/I$ is a field therefore it's finite

answered Mar 8, 2015 at 19:59

4 votes

$K[[X]]$ is not a finitely generated $K[X]$-module.

answered Apr 8, 2016 at 23:25

4 votes

Inequality constant in Papa Rudin

answered May 5, 2019 at 17:19

4 votes

Uniqueness of tempered fundamental solution (with support in half space) for the linear KdV equation

answered Feb 25, 2019 at 23:12

3 votes

Accepted

Can every algebraic set be written as a COUNTABLE union of irreducible algebraic sets?

answered Oct 11, 2016 at 18:49

3 votes

Accepted

Energy Method to show uniqueness of solution of PDE

answered Mar 21, 2015 at 2:43

3 votes

Accepted

Gradient of Harmonic Function

answered Mar 21, 2015 at 2:54

3 votes

Convergence in $L^1_{loc}$ implies convergence almost everywhere

answered Mar 23, 2015 at 23:49

3 votes

Accepted

Why does this set have finite measure?

answered Mar 8, 2015 at 2:52

2 votes

Weak convergence in $L^q$ but not in $L^p$, where $1\leq p<q<\infty$?

answered Mar 8, 2015 at 3:18

2 votes

Line integral (not using Stokes theorem)

answered Mar 13, 2015 at 16:04

2 votes

Is there a field $K$ and a quadratic polynomial $f\in K[T]$ such that $f^2+1$ is a square in $K[T]$?

answered Oct 11, 2016 at 18:58

2 votes

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Prove that $max_{J\subset \{ 1,2...n \} } \left| \sum_{j \in J} z_j\right| = max_{t\in[0,2\pi]} \sum_{j=1}^{n} Re^{+}(e^{it}z_j).$

answered Oct 10, 2016 at 19:02

1 vote

Help with an inequality in Cazenave's book "Semilinear Schrodinger equations"

answered Apr 7, 2015 at 3:40

1 vote

Accepted

A rectangle R is the union of a zero set and countably many disjoint discs

answered Mar 8, 2015 at 4:48

1 vote

Accepted

Problem with base case for transfinite induction

answered Mar 21, 2015 at 2:32

1 vote

What is this motivation for changing variables to standardize a pde?

answered Mar 10, 2015 at 1:55

1 vote

Accepted

Linear partial differential equation.

answered Mar 10, 2015 at 1:31

1 vote

Let $M=\{f(x) \in C[0,1]\mid f(0)=0\}$. Is $\overline{M}=L^2[0,1]$?

answered Mar 10, 2015 at 3:15

1 vote

Accepted

a simple "paradox"

answered Mar 11, 2015 at 3:30

1 vote

Proving that the generator of $U$ is normal if $\forall u \in U, g\in G$ $gug^{-1} \in U$

answered Mar 8, 2015 at 3:07

1 vote

Accepted

Proving the Riemann-Lebesgue Lemma in $L^1(\mathbb{R}^n)$

answered Dec 4, 2014 at 16:17

0 votes

Find an asymptotic formula for $\sum\limits_{n\leq x} d(n)\log n$

answered Mar 4, 2015 at 22:23

0 votes

Accepted

Finding the basis of the null space for $y''''=a^4y$

answered Mar 8, 2015 at 3:34

0 votes

When can you drop an inequality term when you have more than two?

answered Mar 8, 2015 at 3:45

Stack Exchange Network

38 Answers

Proof of $\mathbb{Q}$ is not cyclic

Why doesn't the quadratic equation contain $2|a|$ in the denominator?

Is the Riemann surface for the square root simply connected?

Fundamental group of the special orthogonal group SO(n)

Hatcher's example of a pair without the HEP

$\mathbb{Z}[x_{1},\dots,x_{n}]/I$ is a field therefore it's finite

$K[[X]]$ is not a finitely generated $K[X]$-module.

Inequality constant in Papa Rudin

Uniqueness of tempered fundamental solution (with support in half space) for the linear KdV equation

Can every algebraic set be written as a COUNTABLE union of irreducible algebraic sets?

Energy Method to show uniqueness of solution of PDE

Gradient of Harmonic Function

Convergence in $L^1_{loc}$ implies convergence almost everywhere

Why does this set have finite measure?

Weak convergence in $L^q$ but not in $L^p$, where $1\leq p<q<\infty$?

Line integral (not using Stokes theorem)

Is there a field $K$ and a quadratic polynomial $f\in K[T]$ such that $f^2+1$ is a square in $K[T]$?

Prove that $max_{J\subset \{ 1,2...n \} } \left| \sum_{j \in J} z_j\right| = max_{t\in[0,2\pi]} \sum_{j=1}^{n} Re^{+}(e^{it}z_j).$

Help with an inequality in Cazenave's book "Semilinear Schrodinger equations"

A rectangle R is the union of a zero set and countably many disjoint discs

Problem with base case for transfinite induction

What is this motivation for changing variables to standardize a pde?

Linear partial differential equation.

Let $M=\{f(x) \in C[0,1]\mid f(0)=0\}$. Is $\overline{M}=L^2[0,1]$?

a simple "paradox"

Proving that the generator of $U$ is normal if $\forall u \in U, g\in G$ $gug^{-1} \in U$

Proving the Riemann-Lebesgue Lemma in $L^1(\mathbb{R}^n)$

Find an asymptotic formula for $\sum\limits_{n\leq x} d(n)\log n$

Finding the basis of the null space for $y''''=a^4y$

When can you drop an inequality term when you have more than two?