Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (by J. Lengler, K. Bringmann, B. Gärtner, M. Hoffmann, R. Kyng, D.Steurer, V. Traub)

Mittagsseminar Talk Information

Date and Time: Tuesday, February 18, 2025, 12:15 pm

Duration: 30 minutes

Location: CAB G51

Speaker: Michael Hoffmann

Monotone Arc Diagrams with Few Biarcs

Arc diagrams are plane embeddings of graphs that represent vertices as points on a horizontal line, called spine, and each edge as a sequence of halfcircles centered on the spine. If each such sequence consists of one halfcircle only, then we face a 2-page book embedding. Not every planar graph admits a 2-page book embedding, only the subgraphs of Hamiltonian planar graphs do. But every planar graph admits an arc diagram where each edge is represented as a sequence of two halfcircles, a so-called biarc. Furthermore, we can restrict all biarcs to be monotone with respect to the spine. Some number of edges can always be represented as proper arcs, that is, as a single halfcircle. But how many? For a planar graph G, let mhd(G) denote the minimum number of biarcs over all arc diagrams of G where each edge is represented as a proper arc or as a monotone biarc. In this talk I will discuss upper and lower bounds on mhd for some classes of planar graphs. This is joint work with Steven Chaplick, Henry Förster, and Michael Kaufmann.


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