MATH3506 Problem Sheet 5
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
MATH3506 Problem Sheet 5
1. Construct cobweb maps and analyse the linear stability for (a)
(1 + r)Nt
1 + rNtb
(b)
(1 + r)Nt
Nt+1 =
where r, b > 0. Discuss the global qualitative behaviour of the solutions for different values of r, b.
2. Verify that there exists an exact solution to the discrete logistic equation
Nt+1 = rNt (1 - Nt )
of the form Nt = sin2 (αt ), for a certain value of r and an appropriately chosen α 0. What can you say of the asymptotic behaviour of this system?
3. Let f : R → R be a smooth function. Consider the model Nt+1 = f(Nt ), with N0 > 0.
(a) What condition(s) on f ensures that Nt > 0 for all t = 0, 1, 2, . . ..
(b) What condition(s) on f ensures that Nt remains bounded for all t = 0, 1, 2, . . ..
(c) Suppose that f 2 0, f(N) → 0 as N → o and f(N) = N has three solutions N = 0, N1 , N2 where 0 < N1 < N2 . Show that if Nt falls below a certain value, which you should find, then Nt → 0 as t → o. Find also an upper bound for the population.
2023-05-08