Galactic civilizations: Population dynamics and interstellar diffusion
Abstract
The interstellar diffusion of galactic civilizations is reexamined by potential theory; both numerical and analytical solutions are derived for the nonlinear partial differential equations which specify a range of relevant models, drawn from blast wave physics, soil science, and, especially, population biology. An essential feature of these models is that, for all civilizations, population growth must be limited by the carrying capacity of the environment. Dispersal is fundamentally a diffusion process; a densitydependent diffusivity describes interstellar emigration. Two models are considered: the first describing zero population growth (ZPG), and the second which also includes local growth and saturation of a planetary population, and for which an asymptotic traveling wave solution is found.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 December 1978
 Bibcode:
 1978STIN...7919972N
 Keywords:

 Exobiology;
 Extraterrestrial Life;
 Population Theory;
 Analysis (Mathematics);
 Colonies;
 Diffusion;
 Galaxies;
 Mathematical Models;
 Potential Theory;
 Wave Fronts;
 Astrophysics