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Ali Taghavi
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Isochronousation of quadratic vector fields with center

What is a classification of all quadratic vector fields

$$\begin{cases} x'=P(x,y)\\ y'=Q(x,y) \end{cases}\;\;\;\; (V)$$ with a center at origin such that $(\frac{yP(x,y)-xQ(x,y)}{x^2+y^2})V$ has an isochronous center at $(0,0)$.

In particular does $y\partial_x-(x+x^2)\partial_y$ satisfy the above property?

The motivations is mentioned in the following two posts:

A curvature description for center condition for quadratic vector field

An explicit formula for a flat metric compatible to certain polynomial vector field with center

Ali Taghavi
  • 356
  • 8
  • 31
  • 123