Re: poly: ESS for HPLD

From: Robin Hanson <>
Date: Wed Dec 10 1997 - 15:58:20 PST

Anders wrote:
>> If I find time,
>> I'll summarize the assumptions of the published models Brin mentioned.
>I would be very interested in hearing more about them.

OK. The main thing I've found so far is an '81 article by Newman & Sagan,
Icarus 46, pp293-327, "Galactic Civilizations: Population Dynamics and
Interstellar Diffusion".

They're all screwed up w.r.t. the parameters they choose: they're thinking
about human populations that grow and move very slowly. But they do have
a nice summary of population colonization differential equations, and
the effects of discretization. However, there is no "strategic" analysis.

For example, their primary model is

dp/dt = a*p*(1-p/q) + (d/dx)[b*(p/q)^N (dp/dx)]

where p is population density, q is a carrying capacity, a is a growth rate,
b a diffusion constant, and N a small integer. This has an asymtotoic
traveling wave with a near unit velocity and depth, using units where

There is no analysis of what emmigration/ growth strategy would be optimal
or selected for.

Robin Hanson
RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884
140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-8614
Received on Wed Dec 10 23:52:32 1997

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