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bio website eqnets.com
location Inside the Beltway
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visits member for 4 years, 10 months
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My mathematically-oriented work generally explores discrete geometric and probabilistic themes in physics, computation, and communication. Jack of most trades, master of none.

I can be reached at sh#eqnets#com (make the obvious substitutions for #).


Sep
6
comment Topological description of inverting a knot
Here is a very coarse physical characterization: knots can arise via entropic forces, and are hard to untangle by the second law.
Sep
5
awarded  Popular Question
Sep
3
comment The sum of the carries when adding and multiplying two numbers in base p
math.wayne.edu/~isaksen/Expository/carrying.pdf
Sep
2
comment Recognize this strange expression from linear algebra?
If I've handled my indices correctly then $2a_j = \sum_{k \ell} c_{k \ell} (c_{\ell j} - \delta_{\ell k}) g_{kj}$.
Aug
26
awarded  Nice Answer
Aug
22
comment Is the sequence of Apéry numbers a Stieltjes moment sequence?
oeis.org/A228143
Aug
18
comment Cohomology of the toric variety $X_\Sigma=\mathbb C^2\sqcup \mathbb C^2\big/\left((x,y)_1\sim(x^{-1},y^{-1})_2\right)_{x,y\neq 0}$
You might want to take a look at Ewald's book: books.google.com/books?id=EEiwI7k7Mx8C
Aug
9
answered Examples of unexpected mathematical images
Jul
31
awarded  Popular Question
Jul
31
comment Reference request for instantons
You might also look at Chapter 8 of Ward and Wells' book on twistors.
Jul
29
answered Escape the zombie apocalypse
Jul
29
comment Reference request for instantons
It sounds like you're probably past this, but you might take a peek at section 13.2 of amazon.com/Classical-Theory-Fields-Valery-Rubakov/dp/0691059276
Jul
18
comment Rediscovery of lost mathematics
Grassmann is another good example from your link...
Jul
18
comment Rediscovery of lost mathematics
en.wikipedia.org/wiki/Stark%E2%80%93Heegner_theorem#History
Jul
18
comment Notable mathematics during World War II
@Gerry: Ha! But I'd been to APG once upon a time and had a rather different impression--the ordnance was quite loud...
Jul
2
awarded  Inquisitive
Jul
2
awarded  Curious
Jun
20
comment Maximum of two normal random variables
en.wikipedia.org/wiki/…
Jun
17
reviewed Approve suggested edit on How do I make the conceptual transition from multivariable calculus to differential forms?
Jun
12
comment Method to Generate Random Mutually Orthogonal Unitary Matrices
As an aside to Carlo's comment, two mutually orthogonal unitaries can be easily constructed: take diagonal unitaries $U^{(j)} \in U(n)$ for $j = 1,2$ with $U^{(j)}_{kk} = \exp(i\theta^{(j)}_k)$. Orthogonality then means that $\sum_{k=1}^n \exp(i[\theta^{(2)}_k-\theta^{(1)}_k]) = 0$. This can be enforced by choosing $\theta^{(2)}_k-\theta^{(1)}_k = 2\pi k/n$.