- I'll be at Dartmouth College this week giving the
Kemeny Lectures
on Wednesday, Thursday and Friday. Drop by if you get the chance; my talks
will demo WinCA (see our soup from the week of Feb. 27).
- During my absence the Kitchen is featuring a recipe by guest chef
Alex Day
(dayx0001@flipper.itlabs.umn.edu). Recall that for the past couple of
weeks we have discussed a mystery graphic from the Turbo Pascal
Programmer's Page. Contrary to the contention of several regular visitors
to the Kitchen that tp.gif represents a kind of diffusion limited
aggregation, I was convinced that competing oriented percolations
generated the image. Such a random cellular automaton rule is the
discrete-time analog of the competing contact processes studied by
my colleague Claudia Neuhauser
(neuhause@math.wisc.edu) in her thesis.
- Alex sent me this week's soup along with the source code that
generated it, in both Basic and C versions. Rather remarkably, his
algorithm can be formulated as either a ballistic aggregation rule or as
a kind of directed contact interface; these two interpretations produce
exactly the same dynamics, as confirmed by a separate program he has
written to check the identity. It's probably best to let Alex explain the
rule in his own words. His message to me,
alex_day.txt contains concise descriptions of the two variants,
all the source code, and a nice collection of references to books and
articles on related matters. In retrospect, I must admit that Alex' solution
to the puzzle seems preferable to the one proposed by me and a number of my
colleagues...
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