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I am having some difficulties understanding an argument in a proof. Here is an excerpt from Lyubich–Peters - Classification of invariant Fatou components for dissipative Henon maps, first geometric proof in the Appendix:

The following argument is a more geometric presentation of the argument given in the main body of the paper. To fix the idea, let us assume that the image of $f$ is the standard cusp $\{w^2$ = $z^3\}$. Let us include into holomorphic foliation $\mathbb{F}$ with leaves $L_\lambda = \{w^2 = \lambda z^3\}$, $\lambda \in \hat{\mathbb{C}}$. Let us puncture out $0$, and consider the space $\mathbb{O}$ of leaves in the punctured neighborhood of the origin. This space has a natural Riemann orbifold structure (supported on the sphere) whose local charts are obtained by taking local transversals to $\mathbb F$ and slicing the leaves to it. There are two orbifold points on $\mathbb O$: the leaf $w = 0$ is an orbifold point of order $3$ and the leaf $z = 0$ is an orbifold point of order $2$. So, the Euler characteristic of $\mathbb O$ is equal to $1/2+1/3 < 1$.

I should mention that I have an introductory understanding of Orbifolds, Riemannian Orbifolds, and Foliations. I am trying to understand how $\mathbb{O}$ is acquiring the structure, and what "supported on a sphere" refers to in this case. If possible, an intuitive description of this process is what I would like to have as an answer.

P.S. By cusp they mean $\{(z,w): z^{2} - w^{3}= 0 \} \subset \mathbb{C}^{2}$.

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  • $\begingroup$ What is the paper? $\endgroup$
    – LSpice
    Commented Jan 12, 2021 at 23:17
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    $\begingroup$ Classification of invariant Fatou components for dissipative Henon maps, GAFA, (first geometric proof in the Appendix), link: math.stonybrook.edu/preprints/ims12-07.pdf $\endgroup$
    – nandi
    Commented Jan 13, 2021 at 0:15
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    $\begingroup$ I have edited in that information. $\endgroup$
    – LSpice
    Commented Jan 13, 2021 at 0:34
  • $\begingroup$ I believe that they mean that the underlying space for the orbifold is the Riemann sphere. The charts near most points are just the usual charts, except near the two leaves mentioned, where you have a degree 3 resp. 2 branched cover (i.e., z^3 or z^2 near the origin). A good source for one-complex dimensional orbifolds is the corresponding chapter in Milnor's book on one-dimensional complex dynamics. $\endgroup$ Commented Jan 13, 2021 at 16:13
  • $\begingroup$ Thanks for the answer and the reference. $\endgroup$
    – nandi
    Commented Jan 13, 2021 at 19:16

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