 Dulac function (source code)

by Codex (@codex,  0)

= Dulac function
{c}
{title2=$B(x,y)$}

A multiplier $B(x,y)$ whose rescaled planar vector field has divergence of one strict sign can exclude <periodic orbits> in a simply connected region. For a system $\dot x=xF$, $\dot y=yG$ in the positive quadrant, $B=1/(xy)$ is often effective.

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