User Matsmir

13 votes

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What do you get when you sum over the smaller half of the harmonic series?

answered Dec 31, 2019 at 17:12

8 votes

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"Square-normal" matrices are normal

answered Jan 5, 2020 at 0:36

7 votes

Topological space which is homeomorphic to its square

answered Dec 31, 2019 at 13:18

7 votes

Does this condition imply isomorphism?

answered Jan 15, 2020 at 0:28

7 votes

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Does the spectrum of a bounded from below self-adjoint operator have a lower bound?

answered May 3, 2021 at 10:22

6 votes

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Isomorphism of a Banach space on to a Hilbert space

answered Aug 5 at 0:40

5 votes

Let $X \in M_n(\mathbb{C})$. Is the set $S=\{Y \in M_n(\mathbb{C}) : X \sim Y\}$ closed?

answered Jul 30 at 23:04

5 votes

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How can I show that $\|\,|A|\,|A^*|\,\|=\|A^2\|$?

answered Jul 28 at 19:41

5 votes

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If each of the coefficient of $f(x) = a_0+a_1x+\cdots+a_nx^n$ is a zero divisor, then $f(x)$ is a zero divisor

answered Sep 2 at 10:12

5 votes

Does strong convergence of operators imply pointwise convergence of their unbounded inverses?

answered Sep 3 at 13:39

4 votes

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Covering finite sets with a set of least measure?

answered Jul 29 at 1:06

4 votes

Real Analytic Maps with Dense Image

answered Jul 30 at 22:27

4 votes

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For $S\subset V$, under what conditions does $f\colon S\to W$ extend to a linear map $\hat{f}\colon\text{span}(S)\to W$?

answered May 21, 2021 at 23:37

4 votes

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If $f_n\rightharpoonup f$ in $H^1$, is it true that $f_n\rightharpoonup f$ and $f_n'\rightharpoonup f'$ in $L^2$?

answered Jan 23, 2020 at 17:40

4 votes

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A compact normal operator is diagonalisable.

answered Jul 21, 2020 at 18:30

4 votes

$1 + 1/4 + 1/9 + 1/16 + .... + 1/n^2 < 2 - \frac{1}{n}$ for all $n \ge 2$ , $n \in N$.

answered Dec 31, 2019 at 14:58

4 votes

Find $\lim\limits_{n \to \infty} \frac{1}{n} \int\limits_0^1 \ln (1 + e^{nx}) dx$.

answered Dec 29, 2019 at 23:08

4 votes

Weak convergence in the space of tempered distributions and weighted Sobolev spaces

answered Jan 5, 2020 at 18:59

3 votes

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T is a closed map if dim(Y/T(X)) is finite

answered Jan 5, 2020 at 0:16

3 votes

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Can I create a $4\times 4$ diagonal matrix with the elements of a $2\times 2$ matrix on the diagonal through left/right matrix multiplication?

answered Jan 1, 2020 at 22:50

3 votes

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Proving a series converge

answered Jan 1, 2020 at 16:41

3 votes

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Inequality of functional on a Banach Algebra

answered Jan 4, 2020 at 20:04

3 votes

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$\frac1x\le f'(x)\le x$ implies $\lim_{x\to\infty}\ f(x)=+\infty$

answered Dec 30, 2019 at 13:39

3 votes

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Schwarz function if $|f(x)|\leq\frac{C}{(1+|x|^2)^N}$ for all $x$?

answered Dec 31, 2019 at 17:24

3 votes

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Doubt in understanding 6.3 form Rudin functional analysis

answered Jan 17, 2020 at 10:24

3 votes

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Showing an operator is compact by using Schauder's Theorem

answered Jan 12, 2020 at 22:03

3 votes

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Is a weak* limit of a sequence of tempered distributions indeed a tempered distribution?

answered Jan 9, 2023 at 22:03

3 votes

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Connected components of $\{A \in M_n(\mathbb{R}) \mid A^2 \neq 0\}$

answered Jan 21, 2023 at 15:24

3 votes

Accepted

Every matrix can be changed to a symmetric matrix through elementary column operations

answered Jan 21, 2023 at 17:12

3 votes

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If $\sigma: L \rightarrow L$ is a $K$-automorphism, where $K$ is dense in $L$ w.r.t some fitting topology, is $\sigma$ the identity?

answered Aug 1 at 14:08

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98 Answers

What do you get when you sum over the smaller half of the harmonic series?

"Square-normal" matrices are normal

Topological space which is homeomorphic to its square

Does this condition imply isomorphism?

Does the spectrum of a bounded from below self-adjoint operator have a lower bound?

Isomorphism of a Banach space on to a Hilbert space

Let $X \in M_n(\mathbb{C})$. Is the set $S=\{Y \in M_n(\mathbb{C}) : X \sim Y\}$ closed?

How can I show that $\|\,|A|\,|A^*|\,\|=\|A^2\|$?

If each of the coefficient of $f(x) = a_0+a_1x+\cdots+a_nx^n$ is a zero divisor, then $f(x)$ is a zero divisor

Does strong convergence of operators imply pointwise convergence of their unbounded inverses?

Covering finite sets with a set of least measure?

Real Analytic Maps with Dense Image

For $S\subset V$, under what conditions does $f\colon S\to W$ extend to a linear map $\hat{f}\colon\text{span}(S)\to W$?

If $f_n\rightharpoonup f$ in $H^1$, is it true that $f_n\rightharpoonup f$ and $f_n'\rightharpoonup f'$ in $L^2$?

A compact normal operator is diagonalisable.

$1 + 1/4 + 1/9 + 1/16 + .... + 1/n^2 < 2 - \frac{1}{n}$ for all $n \ge 2$ , $n \in N$.

Find $\lim\limits_{n \to \infty} \frac{1}{n} \int\limits_0^1 \ln (1 + e^{nx}) dx$.

Weak convergence in the space of tempered distributions and weighted Sobolev spaces

T is a closed map if dim(Y/T(X)) is finite

Can I create a $4\times 4$ diagonal matrix with the elements of a $2\times 2$ matrix on the diagonal through left/right matrix multiplication?

Proving a series converge

Inequality of functional on a Banach Algebra

$\frac1x\le f'(x)\le x$ implies $\lim_{x\to\infty}\ f(x)=+\infty$

Schwarz function if $|f(x)|\leq\frac{C}{(1+|x|^2)^N}$ for all $x$?

Doubt in understanding 6.3 form Rudin functional analysis

Showing an operator is compact by using Schauder's Theorem

Is a weak* limit of a sequence of tempered distributions indeed a tempered distribution?

Connected components of $\{A \in M_n(\mathbb{R}) \mid A^2 \neq 0\}$

Every matrix can be changed to a symmetric matrix through elementary column operations

If $\sigma: L \rightarrow L$ is a $K$-automorphism, where $K$ is dense in $L$ w.r.t some fitting topology, is $\sigma$ the identity?