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  "body": "\n## Summary\n\nA Herman ring is a component of the [[Fatou set|C0N0XGC6GK]] of a rational map that is a topological annulus.\nOn it some iterate of the map acts as an irrational rotation.\nIt is one of the four types of periodic Fatou components, next to attracting basins, parabolic basins and [[Siegel discs|KNDYA9T8ZK]].\nUnlike a Siegel disc, it has no fixed point at its centre.\nPolynomials never have Herman rings, so they appear only for rational maps that are not polynomials.\n\n## Explanations\n\n### L1 human\n\nPicture a ring, like a washer, that the map turns around and around by an angle that is an irrational fraction of a full turn.\nPoints travel forever on closed loops that circle the hole of the ring.\nThe hole and the outside of the ring both contain points of the Julia set.\nMichael Herman showed that such rings really occur for rational maps.\n",
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