There's a theorem in control theory that sets limits on how quickly
the gain of a feedback system can change with frequency without
driving oscillations. This is the logic behind using the
integral and/or the derivative
of the feedback signal in
mechanized control systems. One factor in the current financial
tension between short-term and long-term risk
a problem that
also appears in smaller-scale "markets."
Suppose this tension were reduced by, say, paying fund managers
investments less liquid than cash, in some quantifiable way.
Are cash commissions guaranteed to have boom and bust oscillations?
Do oscillation-free commission schemes exist?
2008-12-31 Wednesday 10:03:07
A stopped clock is exactly right twice a day.
With some error-weighted averages, a stopped clock is more
accurate on average than a clock running, say, ten minutes fast.
What averages do and don't have this property?
2008-11-19 Wednesday 23:40:45
New "open" signs at restaurants, with bright red and blue LEDs,
bring out some chromatic aberration in my glasses: viewed
peripherally, the different-colored parts don't line up.
Quantify? Why have I only just started to notice this?
2008-11-11 Tuesday 09:44:38
Passing traffic makes Doppler-shifted noises ("wheeee-oooom").
Useful trick: map between musical interval of the shift
and the speed of the traffic?
2008-11-11 Tuesday 09:38:19
Suppose I replace an incandescent light bulb with a more expensive,
more energy-efficient, longer-lived light — a CFL, an LED,
whatever — based on the expectation that it'll cost less over
its life. How old does my incandescent bulb have to be before I
actually save anything?
2008-10-28 Tuesday 21:42:08
If you pull two connected blobs of Silly Putty apart slowly, the
thread between then stretches plastically; if you pull them apart
quickly, it fractures cleanly. What sets the threshold? How sharp
2008-10-20 Monday 16:16:27
How strong is the correlation between income tax witholding /
refunding and tolerance for government spending?
2008-10-14 Tuesday 23:05:05
If Hawking's connection between black holes and thermodynamics
is right, astrophysical black holes --- for which general
relativity predicts everything bizarre happens well inside the
horizon, and for which there are observational evidence --- are at
the zero-temperature limit. What's the "warmest"
black hole for which there is observational evidence? What's
the transition "temperature" where quantum gravity starts
2008-10-06 Monday 19:45:48
by Consumer Reports
, that breakfast cereals marketed to
children aren't terribly nutritious, has gotten some
evening-news press. The main contribution of the Consumer Reports
release seems to be that they bought a bunch of cereal and read the
nutrition labels. What's new here? Has the composition of
existing products been tweaked? Have some sweeter brands been
introduced to replace healthier ones? How do these sorts of news
blobs correlate with sales, or with marketing spending?
2008-10-06 Monday 12:29:26