Untangling two systems of noncrossing curves

Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F16%3A10328975" target="_blank" >RIV/00216208:11320/16:10328975 - isvavai.cz</a>
Result on the web
<a href="http://dx.doi.org/10.1007/s11856-016-1294-9" target="_blank" >http://dx.doi.org/10.1007/s11856-016-1294-9</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1007/s11856-016-1294-9" target="_blank" >10.1007/s11856-016-1294-9</a>

Result language
angličtina
Original language name
Untangling two systems of noncrossing curves
Original language description
We consider two systems (alpha(1), ... ,alpha(m)) and (beta(1), ... , beta(n)) of simple curves drawn on a compact two-dimensional surface M with boundary. Each alpha(i) and each beta(j) is either an arc meeting the boundary of M at its two endpoints, or a closed curve. The a, are pairwise disjoint except for possibly sharing endpoints, and similarly for the beta(j). We want to "untangle" the beta(j) from the alpha(i) by a self-homeomorphism of M; more precisely, we seek a homeomorphism phi: M -> M fixing the boundary of M pointwise such that the total number of crossings of the a, with the phi(beta(j)) is as small as possible. This problem is motivated by an application in the algorithmic theory of embeddings and 3 -manifolds. We prove that if M is planar, i.e., a sphere with h >= 0 boundary components ("holes"), then O(mn) crossings can be achieved (independently of h), which is asymptotically tight, as an easy lower bound shows. In general, for an arbitrary (orientable or nonorientable) surface M with h holes and of (orientable or nonorientable) genus g >= 0, we obtain an O((m + n)(4)) upper bound, again independent of h and g. The proofs rely, among other things, on a result concerning simultaneous planar drawings of graphs by Erten and Kobourov.
Czech name
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Czech description
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Type
J<sub>x</sub> - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)
CEP classification
BA - General mathematics
OECD FORD branch
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Project
<a href="/en/project/GEGIG%2F11%2FE023" target="_blank" >GEGIG/11/E023: Graph Drawings and Representations</a><br>
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year
2016
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

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