English

Algebraically grid-like graphs have large tree-width

Combinatorics 2018-02-15 v1

Abstract

By the Grid Minor Theorem of Robertson and Seymour, every graph of sufficiently large tree-width contains a large grid as a minor. Tree-width may therefore be regarded as a measure of 'grid-likeness' of a graph. The grid contains a long cycle on the perimeter, which is the F2\mathbb{F}_2-sum of the rectangles inside. Moreover, the grid distorts the metric of the cycle only by a factor of two. We prove that every graph that resembles the grid in this algebraic sense has large tree-width: Let k,pk, p be integers, γ\gamma a real number and GG a graph. Suppose that GG contains a cycle of length at least 2γpk2 \gamma p k which is the F2\mathbb{F}_2-sum of cycles of length at most pp and whose metric is distorted by a factor of at most γ\gamma. Then GG has tree-width at least kk.

Keywords

Cite

@article{arxiv.1802.05158,
  title  = {Algebraically grid-like graphs have large tree-width},
  author = {Daniel Weißauer},
  journal= {arXiv preprint arXiv:1802.05158},
  year   = {2018}
}

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6 pages