User David Z - Mathematics Stack Exchange

David Z

Member for 12 years, 9 months
Last seen more than a week ago

GitHub
ellipsix.net
Sunnyvale, CA, United States

21 Questions

Score Activity Newest Views

57 votes

8 answers

15k views

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

asked Jan 11, 2012 at 8:16

11 votes

2 answers

6k views

Is any divergence-free curl-free vector field necessarily constant?

asked Jan 28, 2011 at 23:42

10 votes

1 answer

332 views

What's the right way to make a change of variables under another integral?

asked Sep 4, 2012 at 6:34

7 votes

3 answers

874 views

What's the term for a "physical vector space"?

asked May 11, 2014 at 6:03

5 votes

2 answers

3k views

How do I write the 2D Dirac delta in a manifestly rotationally invariant form?

asked Nov 29, 2011 at 23:29

5 votes

1 answer

898 views

How can I prove this identity involving the digamma function?

asked Dec 14, 2010 at 10:03

5 votes

1 answer

318 views

Asymptotic behavior of an integral involving the gamma function

asked Apr 7, 2016 at 18:48

4 votes

1 answer

2k views

What kind of quadrilateral is determined by four sides and a diagonal?

asked Nov 6, 2012 at 8:22

4 votes

2 answers

912 views

What does the Fourier transform of $1/x^2$ mean?

asked Jun 17, 2014 at 8:32

3 votes

0 answers

528 views

How can I integrate a Bessel function divided by a "shifted" value?

asked Jan 20, 2011 at 1:50

3 votes

1 answer

744 views

Proving an identity involving the derivative of the Laguerre polynomials with respect to $n$

asked Aug 7, 2012 at 4:27

2 votes

1 answer

73 views

Necessary/sufficient conditions to express numbers as differences of other numbers

asked Feb 15, 2011 at 6:23

2 votes

1 answer

101 views

Large-z limit of the other second derivative of the Laguerre polynomial

asked Nov 20, 2014 at 9:32

2 votes

1 answer

139 views

Symbolically solving coupled partial differential equations

asked Nov 8, 2015 at 16:26

1 vote

1 answer

768 views

Does an inward vector field on a boundary require a zero point or singularity in the interior?

asked May 27, 2013 at 2:01

1 vote

1 answer

390 views

Is there a known simple mental approximation to a hypergeometric distribution?

asked Dec 23, 2014 at 5:47

1 vote

0 answers

194 views

Do the classical Lie algebras all satisfy $XM + MX^T = 0$?

asked Feb 10, 2011 at 1:17

1 vote

2 answers

198 views

Is it always possible to choose 2-partitions of a set that cover the maximum number of pairs without repeating?

asked Oct 16, 2017 at 4:19

0 votes

1 answer

112 views

Is there a standard name for one period of a triangle function?

asked Apr 10, 2011 at 5:54

0 votes

1 answer

3k views

Solving an equation with a "nested" function: $f(t_1 + t_2, K) = f\bigl(t_2, f(t_1, K)\bigr)$

asked Sep 2, 2011 at 22:53

0 votes

2 answers

169 views

Why would the eigenvalues of this type of (stochastic) matrix all be close to 1?

asked Sep 13, 2015 at 15:31