{ "id": "1701.05597", "version": "v1", "published": "2017-01-19T20:54:51.000Z", "updated": "2017-01-19T20:54:51.000Z", "title": "Induced subgraphs of graphs with large chromatic number. VI. Banana trees", "authors": [ "Alex Scott", "Paul Seymour" ], "categories": [ "math.CO" ], "abstract": "We investigate which graphs H have the property that in every graph with bounded clique number and sufficiently large chromatic number, some induced subgraph is isomorphic to a subdivision of H. In an earlier paper, one of us proved that every tree has this property; and in another earlier paper with M. Chudnovsky, we proved that every cycle has this property. Here we give a common generalization. Say a banana is the union of a set of paths all with the same ends but otherwise disjoint. We prove that if H is obtained from a tree by replacing each edge by a banana then H has the property mentioned. We also find some other multigraphs with the same property.", "revisions": [ { "version": "v1", "updated": "2017-01-19T20:54:51.000Z" } ], "analyses": { "keywords": [ "induced subgraph", "banana trees", "earlier paper", "sufficiently large chromatic number", "bounded clique number" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable" } } }