From: Robin Hanson <hanson@econ.berkeley.edu>

Date: Wed Dec 10 1997 - 15:58:20 PST

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

a=b=1.

There is no analysis of what emmigration/ growth strategy would be optimal

or selected for.

Robin Hanson

hanson@econ.berkeley.edu http://hanson.berkeley.edu/

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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