Archive for August, 2010

August 31, 2010

wavelets and multiresolution

(Source: http://blip.tv/)
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flops

August 30, 2010

At least in Javascript, that’s how it works.  Apparently floating-point operations are not exactly accurate in a computer, the way integer arithmetic or arbitrary-precision arithmetic is.

Javascript

scheherazade:~$ js
Rhino 1.7 release 2 2010 01 20
js> .1+.2
0.30000000000000004

Berkeley Calculator

scheherazade:~$ bc -l
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
.0003^2 + .0004^2 - .0005^2
0

(from the 3,4,5 right triangle used in the SAT)

August 29, 2010

The Amazon preview was really funny!

“This has become something of a ‘me-too’ trade lately,” said Mark Spitznagel, a former Taleb trading partner at Empirica.
The upside of everyone piling onto these catastrophe protection funds is that — guess what — all those people hedging against a catastrophe will reduce its likelihood of happening.

August 28, 2010

PIMCO offers Black Swan protection fund

Probability of God

August 28, 2010

Sigh.

Apparently if you go beyond the Amazon preview, Unwin just makes up some numbers, plugs them into the Bayesian machine, and — poof! — calculates the probability he wants for God’s existence, 2/3 (which he later ups to 95%).

Doing this with numbers I agree with yields a probability more like 10^−17.  That sounds really low but I guess the point is, when you make up lots of numbers, you can reach any conclusion you want.

Essentially, Unwin made up an arbitrary number of points to assign to various evidence for/against God, and then also made up what the evidence said about those criteria.

For example, the existence of human moral evil is evidence against God, and he says that current levels of moral evil militate for odds of 2:1 against God (while current levels of moral good militate for 1:10 for God).  My response, in two words:  genocide and … ?

My question coming out of this is:  are quants unscientific?  Unwin was a quant and got hired for primo positions.

Also, dumb assertion in Wilmott:  Mao, Hitler, and Stalin were all half-educated — to the point of charisma but not to the point where they realize “the madness and helplessness of it all”.  The author’s solution?  ”Managing society requires the world to embrace randomness.” (sic)  That itself sounds half-educated to me — like somebody who treats randomness and risk as an epsilon symbol.

So are the quants like some mathematically sophisticated quasi-skeptics who really believe in magic?

August 27, 2010

Which of these pictures come from a random normal distribution and which come from a mixed distribution?

plot(rnorm,-3,3);

mix <- function(x) {
rnorm(x)+rnorm(x-3)
}

plot(mix(x), -3,3);

August 26, 2010

I’m deeply skeptical about this.  Why is Ernie Chan telling me how I can make millions?  Is he just trying to increase the pool of suckers for him and his like to take money from?  If so, how does he know other firms wouldn’t profit from the suckers instead of his?

(A Lévy-Pareto process has infinite variance.) comptes_rendus_28 Cauchy distribution has infinite variance as contrasted to… Gaussian distribution which shoots down REAL fast: fast.

August 26, 2010

original Mandelbrot article on cotton prices as a Levy process

August 25, 2010

This is what I have been reduced to.  Henry County Public Library, I curse thee.

Grigory Perelman

August 24, 2010

Why did the mathematician who solved the first Millennium Prize problem— Poincaré’s conjecture that all 3-manifolds are ultimately equivalent to spheres—decline a million dollars and worldwide fame? (Well, he still got the fame or else I wouldn’t be talking about him.)

So why did Perelman turn down a fortune?

  1. He has already saved up enough money to live for the rest of his life.  (He’s ascetic.)
  2. He is taking a stand against the egotism and credit-grabbing that apparently characterizes mathematics.  (“I discovered it first!”  “No, I did!”)

Perelman wants his prize to be shared with a former colleague (Hamilton) without whom he could never have begun his famous proof (part 1, part 2). And at the same time some other mathematicians (Yau, Cao, Zhu) are claiming that his work was incomplete — a sketch, not a proof. They wrote their own version which they say is better, but Perelman deeply believes that they are just trying to steal credit for making minor clarifications to his work which was already complete in the first place.

Perelman is attracted to people who share their ideas in the hope of striving together toward a worthy goal (like proving the Poincaré conjecture). By turning down fame and fortune, he’s putting his money where his mouth is.  What’s important is what we accomplished, he’s saying. Not who gets the glory.

Now two more problems out of the seven Millennium Problems — and these are fifty- or hundred-year-old problems — may have been solved.  Deodar Deolalikar claims to have proved that P ≠ NP.  And Jorma Jormakka says he solved the Navier-Stokes equation.  (Apparently, it’s good to have your initials be the same.  Note to self.)  Update:  Some people say both DD and JJ are wrong.  Reconsidering name change.