User Jonas Meyer - Mathematics Stack Exchange

148 votes

What functions or classes of functions are $L^1$ but not $L^2$?

answered Jan 21, 2011 at 4:37

147 votes

How can I evaluate $\sum_{n=0}^\infty(n+1)x^n$?

answered Apr 3, 2011 at 22:25

119 votes

Accepted

Difference between complete and closed set

answered Oct 14, 2010 at 7:13

102 votes

Accepted

Does every Abelian group admit a ring structure?

answered Dec 22, 2011 at 9:36

78 votes

Accepted

Finding the limit of $\frac {n}{\sqrt[n]{n!}}$

answered Mar 22, 2011 at 13:26

74 votes

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No continuous function switches $\mathbb{Q}$ and the irrationals

answered Aug 4, 2011 at 18:22

69 votes

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Is there a name for function with the exponential property $f(x+y)=f(x) \cdot f(y)$?

answered Feb 15, 2011 at 0:14

68 votes

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What is the difference between isometric and unitary operators on a Hilbert space?

answered Aug 16, 2014 at 17:30

67 votes

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What makes $5$ and $6$ so special that taking powers doesn't change the last digit?

answered May 27, 2013 at 20:00

67 votes

Entire one-to-one functions are linear

answered Mar 29, 2011 at 17:18

66 votes

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Derivation of the formula for the vertex of a parabola

answered Oct 15, 2010 at 2:25

63 votes

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Why doesn't induction extend to infinity? (re: Fourier series)

answered Jan 11, 2012 at 8:33

61 votes

"Negative" versus "Minus"

answered Jun 12, 2012 at 2:49

57 votes

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A function that is $L^p$ for all $p$ but is not $L^\infty$?

answered Dec 12, 2011 at 3:12

49 votes

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How do I rigorously show $f(z)$ is analytic if and only if $\overline{f(\bar{z})}$ is?

answered Jan 27, 2012 at 5:37

46 votes

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When is the image of a linear operator closed?

answered Mar 9, 2011 at 23:45

45 votes

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How to prove $\sin(1/x)$ is not uniformly continuous

answered Nov 6, 2011 at 22:19

45 votes

Accepted

The identity cannot be a commutator in a Banach algebra?

answered Jul 29, 2011 at 4:37

41 votes

Differentiating an Inner Product

answered Jan 4, 2012 at 4:31

40 votes

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Topologist's sine curve is not path-connected

answered Apr 25, 2011 at 18:41

38 votes

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Is every Lebesgue measurable function on $\mathbb{R}$ the pointwise limit of continuous functions?

answered Dec 21, 2010 at 19:02

37 votes

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In written mathematics, is $f(x)$a function or a number?

answered Oct 15, 2010 at 15:07

36 votes

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Norm of an inverse operator: $\|T^{-1}\|=\|T\|^{-1}$?

answered Oct 15, 2013 at 4:01

35 votes

Accepted

Monotone+continuous but not differentiable

answered Jan 11, 2011 at 8:16

33 votes

Accepted

Why can't Cantor sets cover $\mathbb{ R}$?

answered Oct 14, 2010 at 16:57

33 votes

Showing that $\int\limits_{-a}^a \frac{f(x)}{1+e^{x}} \mathrm dx = \int\limits_0^a f(x) \mathrm dx$, when $f$ is even

answered Aug 27, 2011 at 16:16

32 votes

Accepted

Is the void set (∅) a proper subset of every set?

answered Nov 10, 2010 at 5:45

32 votes

Accepted

Interchanging the order of differentiation and summation

answered May 21, 2012 at 20:34

31 votes

Measure of the Cantor set plus the Cantor set

answered Dec 11, 2010 at 8:50

30 votes

vector space of all smooth functions has infinite dimension

answered Mar 13, 2011 at 22:50

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1,403 Answers

What functions or classes of functions are $L^1$ but not $L^2$?

How can I evaluate $\sum_{n=0}^\infty(n+1)x^n$?

Difference between complete and closed set

Does every Abelian group admit a ring structure?

Finding the limit of $\frac {n}{\sqrt[n]{n!}}$

No continuous function switches $\mathbb{Q}$ and the irrationals

Is there a name for function with the exponential property $f(x+y)=f(x) \cdot f(y)$?

What is the difference between isometric and unitary operators on a Hilbert space?

What makes $5$ and $6$ so special that taking powers doesn't change the last digit?

Entire one-to-one functions are linear

Derivation of the formula for the vertex of a parabola

Why doesn't induction extend to infinity? (re: Fourier series)

"Negative" versus "Minus"

A function that is $L^p$ for all $p$ but is not $L^\infty$?

How do I rigorously show $f(z)$ is analytic if and only if $\overline{f(\bar{z})}$ is?

When is the image of a linear operator closed?

How to prove $\sin(1/x)$ is not uniformly continuous

The identity cannot be a commutator in a Banach algebra?

Differentiating an Inner Product

Topologist's sine curve is not path-connected

Is every Lebesgue measurable function on $\mathbb{R}$ the pointwise limit of continuous functions?

In written mathematics, is $f(x)$a function or a number?

Norm of an inverse operator: $\|T^{-1}\|=\|T\|^{-1}$?

Monotone+continuous but not differentiable

Why can't Cantor sets cover $\mathbb{ R}$?

Showing that $\int\limits_{-a}^a \frac{f(x)}{1+e^{x}} \mathrm dx = \int\limits_0^a f(x) \mathrm dx$, when $f$ is even

Is the void set (∅) a proper subset of every set?

Interchanging the order of differentiation and summation

Measure of the Cantor set plus the Cantor set

vector space of all smooth functions has infinite dimension