Paper 4, Section I, E

Mathematical Biology
Part II, 2015

(i) A variant of the classic logistic population model is given by the HutchinsonWright equation

dx(t)dt=αx(t)[1x(tT)]\frac{d x(t)}{d t}=\alpha x(t)[1-x(t-T)]

where α,T>0\alpha, T>0. Determine the condition on α\alpha (in terms of TT ) for the constant solution x(t)=1x(t)=1 to be stable.

(ii) Another variant of the logistic model is given by the equation

dx(t)dt=α[x(tT)x(t)2]\frac{d x(t)}{d t}=\alpha\left[x(t-T)-x(t)^{2}\right]

where α,T>0\alpha, T>0. Give a brief interpretation of what this model represents.

Determine the condition on α\alpha (in terms of TT ) for the constant solution x(t)=1x(t)=1 to be stable in this model.