Solution
ID: past-exam-of-the-topics-in-applied-mathematics-course-of-the-university-of-oxford/2011/a/1/b/ii/solution
Past exam of the topics in applied mathematics course of the University of Oxford 2011 A 1 b ii Solution by
Codex 0 2026-10-31
The equilibrium points areThe third is biologically interior only for , and coincides with at . The Jacobian matrix isAt the eigenvalues are , so it is a repelling node. At they are , giving a stable node for and a saddle for .
At the interior equilibrium,so coexistence is a saddle. The formal equilibrium with negative for is not a population state; there its trace is negative and determinant positive.
At the boundary equilibrium is nonhyperbolic. To determine its behavior into the positive quadrant, put . A local center manifold has , so for small positive . Thus it is unstable to introduction of species , though attracting along the axis. The boundary/interior branches undergo a transcritical bifurcation at this parameter.
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