Physiological aging as an infinitesimally ratcheted random walk.
The distribution of a population throughout the physiological age of the individuals is very relevant information in population studies. It has been modeled by the Langevin and the Fokker-Planck equations. A major problem with these equations is that they allow the physiological age to move back in time. This paper proposes an Infinitesimally ratcheted random walk as a way to solve that problem. Two mathematical representations are proposed. One of them uses a nonlocal scalar field. The other one is local, but involves a multicomponent field of speed states. These two formulations are compared to each other and to the Fokker-Planck equation. The relevant properties are discussed. The dynamics of the mean and variance of the population age resulting from the two proposed formulations are obtained.
Mello
Bernardo A
BA
Institute of Physics, University of Brasilia, DF, Brazil. bernardo@fis.unb.br
D017677:Age Distribution; D000375:Aging / Q000502:physiology*; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D015233:Models, Statistical