Circle graph obstructions under pivoting

A circle graph is the intersection graph of a set of chords of a circle. The class of circle graphs is closed under pivotminors. We determine the pivot-minor-minimal non-circle-graphs; there 15 obstructions. These obstructions are found, by computer search, as a corollary to Bouchet’s characterization of circle graphs under local complementation. Our characterization generalizes Kuratowski’s Theorem.

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