Profile

Cover photo
Alex Nelson
Works at Unfold, Inc.
Attended University of California, Davis
Lives in Los Angeles, California
778 followers|22,740 views
AboutPostsPhotosVideos

Stream

Alex Nelson

Shared publicly  - 
 
It has taken a mere 29 years, but now GNU Hurd has released version 0.6...perhaps they'll get to version 1.0 in my grandchildren's lifetime...

http://lwn.net/Articles/640668/
2
Add a comment...
 
Does intelligent life need an industrial revolution?

The answer, Dartnell posits, is "Yeah, mostly."

http://aeon.co/magazine/technology/could-we-reboot-civilisation-without-fossil-fuels/
It took a lot of fossil fuels to forge our industrial world. Now they're almost gone. Could we do it again without them?
1
Alex Nelson's profile photoDebo Capulet's profile photo
3 comments
 
He was implying that any "Age" - coal, steam and, in the future, oil, e.g. - ends when something better comes along @ a reasonable price. And yes, he put in a cute way to get attention when the market was panicking at the "peak oil" theory.
Add a comment...

Alex Nelson

Shared publicly  - 
 
Climate scientists highlight cloud mysteries in a bid to compete with astronomy and cosmology.
1
Add a comment...

Alex Nelson

Shared publicly  - 
 
California was supposed to have El Nino this year...but that didn't pan out. Could it be that giant plastic garbage island in the Pacific interfered somehow?

Wikipedia tells me the name of this giant garbage patch is really  the "Great Pacific garbage patch" --- a regal name for an ignominious region.

Anyone know for sure?

http://en.wikipedia.org/wiki/Great_Pacific_garbage_patch
1
Add a comment...

Alex Nelson

Shared publicly  - 
 
Filing your own taxes is like a "Pick your own adventure" book...
3
Add a comment...
 
Someone just gave me 5,216.98 bits (or 0.00521698 Bitcoins) for some references I posted on Reddit. I'll be retiring any day now to my provincial French chateau...
3
Add a comment...
In his circles
104 people
Have him in circles
778 people
Paul Schuler's profile photo
Steven V. Calhoun's profile photo
Calton Harvey's profile photo
Peter Pflaum's profile photo
sonii minii's profile photo
ahmed magdy's profile photo
Tommy  Adams's profile photo
Denny Greenberg's profile photo
Gustav Delius's profile photo

Alex Nelson

Shared publicly  - 
 
 
"An average academic journal article is read in its entirety by about 10 people. To shape policy, professors should start penning commentaries in popular media."
Many of the world's most talented thinkers may be university professors, but sadly most of them are not shaping today's public debates or influencing policies.
1 comment on original post
3
Add a comment...

Alex Nelson

Shared publicly  - 
 
Fun exercise: prove $\cos^{n}(x/\sqrt{n})$ converges to $\exp{-x^{2}/2)$.

There are several different approaches I could think of, but they all fall into two "families".

One is to set up a differential equation, arguing $f_{n}(x) = \cos^{n}(x/\sqrt{n})$ has a stable limit $f_{n}(x)\to f(x)$ as $n\to\infty$, then argue $f'_{n}(x)$ has as its limit as $n\to\infty$ precisely $f'(x)$. There's some elementary algebra to get things right, and one needs to observe $f_{n}(0)=1$ for all $n$.

The other is to use the limit definition of e, using $\cos^{n}(x/\sqrt{n})=(1-\sin^{2}(x/\sqrt{n}))^{n/2}$ then arguing $x/\sqrt{n}$ is "small", Taylor expand, then "follow your nose".

Neither are 100% rigorous, both involve handwaviness at some point. But I cannot think of a slick proof for the claim that's completely ("arbitrarily") rigorous.
1
Add a comment...

Alex Nelson

Shared publicly  - 
 
So, I've had the rare fortune to sit in on random math courses at Caltech. I try to write up my notes in #LaTeX as a way of reviewing them, and have found Leslie Lamport's structured proofs quite good at catching errors in my reasoning.

But Lamport's LaTeX package (pf2) is woefully inadequate for my purposes. Most seriously, it's incompatible with amthm.

Since I'm not using TLA+ for automated theorem proving purposes, I can use a stripped down version of Lamport's package. Here's a first pass at it.

What's nifty about my package is if you, like me, are using this only while iteratively correcting your notes, and do not wish the rest of the world to see it, you can pass the "hide" option to comment out all the structured proofs.

https://github.com/pqnelson/notebk/wiki/Structured-Proof-Macros
1
Add a comment...

Alex Nelson

Shared publicly  - 
 
Quillen's notebooks are now freely available online as pdfs.

http://www.claymath.org/publications/quillen-notebooks
2
Add a comment...

Alex Nelson

Shared publicly  - 
Abstract: The singular limits of massless gauge theory amplitudes are described by an effective theory, called soft-collinear effective theory (SCET), which has been applied most successfully to make all-orders predictions for observables in collider physics and weak decays.
1
Add a comment...

Alex Nelson

Shared publicly  - 
 
C++ MAL-adies

I've been mucking around through the MAL tutorial, learning how to build a lisp (with the intention of learning how Clojure works under the hood)...but with C++, so I can investigate how the relevant moving parts of the Java base classes help Clojure.

Unfortunately, step 1 requires lexing/parsing --- translating strings into the actual data structures --- with regular expressions. I say it's unfortunate since the GNU C++ compiler on Ubuntu is 4.8.2...regular expressions aren't implemented until version 4.9 or higher.

I hear the LLVM is the hot new setup, and Clang is supposed to be better than the GNU compiler collection...I suppose I will install these exotic new tools and see how they pan out.

I suspect by step 3 of this process I'll get so frustrated with C++, I'll end up using D. But lets not put the cart before the horse...

Addendum in case anyone is interested, the MAL tutorial is available here: https://github.com/kanaka/mal
1
Add a comment...
People
In his circles
104 people
Have him in circles
778 people
Paul Schuler's profile photo
Steven V. Calhoun's profile photo
Calton Harvey's profile photo
Peter Pflaum's profile photo
sonii minii's profile photo
ahmed magdy's profile photo
Tommy  Adams's profile photo
Denny Greenberg's profile photo
Gustav Delius's profile photo
Education
  • University of California, Davis
    Mathematics, 2006 - 2011
Basic Information
Gender
Male
Other names
Alexander Nelson
Story
Tagline
They call me "Tractor Man"
Introduction
I'm a mathematical physicist (more on the mathematical side) with interests in category theory, monstrous moonshine, number theory, Diophantine approximations, super symmetry, Lie groups, differential geometry, and other topics. On the physical side, I'm intrigued by quantization of gauge systems, Quantum Field Theory, the mathematical underpinnings of particle physics, classical and quantum gravity.

I've been to Nottingham, England in July 2008 to attend Quantum Gravity and Quantum Geometry 2; and I've attended "Algebra and Topology in Interaction" during September 2009, in honour of Dr Fuchs' Birthday.

Starting June 2009 until June 2010, I did undergraduate research with Derek Wise with funding from VIGRE. We worked on Chain Field Theory in discrete spacetimes.

In April 2010 I was asked to peer review for the International Journal of Physical Sciences.

August 2010 I studied abroad at Trinity in Dublin, and Queen's University in Belfast.

In June 2011, I attended "Quantum Geometry and Quantum Gravity" in Zurich, Switzerland; then in July I went to the "Category Theory 2011" conference in Vancouver.

February 2012, I attended "
30th Annual Western States Mathematical Physics Meeting" at Caltech.
Work
Occupation
Mathematician/Programmer/Oracle
Employment
  • Unfold, Inc.
    Software Developer, 2012 - present
    I program in Clojure (Lisp for JVM), do numerical analysis, predict how congress will vote, analyze the Syrian Civil War, and much much more!
  • University of California, Davis
    Student, Researcher, 2006 - 2011
Places
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Currently
Los Angeles, California
Previously
Davis, California - Glendale, California - Dublin, Ireland - Belfast, Northern Ireland - Padua, Italy
Links
Contributor to