Abstract:Abstract. We define the geometric thickness of a graph to be the smallest number of layers such that we can draw the graph in the plane with straight-line edges and assign each edge to a layer so that no two edges on the same layer cross. The geometric thickness lies between two previously studied quantities, the (graph-theoretical) thickness and the book thickness. We investigate the geometric thickness of the family of complete graphs, {Kn}. We show that the geometric thickness of Kn lies between (n/5.646) +… Show more
“…By Theorem 1.4 there is an infinite family of bipartite expanders with simple thickness 2. Furthermore, one may subdivide each edge twice in the above construction, and then draw each edge straight to obtain an infinite family of bipartite expanders with geometric thickness 2 (see [3,10,18]). …”
Bourgain and Yehudayoff recently constructed O(1)-monotone bipartite expanders. By combining this result with a generalisation of the unraveling method of Kannan, we construct 3-monotone bipartite expanders, which is best possible. We then show that the same graphs admit 3-page book embeddings, 2-queue layouts, 4-track layouts, and have simple thickness 2. All these results are best possible.
“…By Theorem 1.4 there is an infinite family of bipartite expanders with simple thickness 2. Furthermore, one may subdivide each edge twice in the above construction, and then draw each edge straight to obtain an infinite family of bipartite expanders with geometric thickness 2 (see [3,10,18]). …”
Bourgain and Yehudayoff recently constructed O(1)-monotone bipartite expanders. By combining this result with a generalisation of the unraveling method of Kannan, we construct 3-monotone bipartite expanders, which is best possible. We then show that the same graphs admit 3-page book embeddings, 2-queue layouts, 4-track layouts, and have simple thickness 2. All these results are best possible.
“…It is unknown whether for some constant ε > 0, every geometric drawing of K n has thickness at most (1 − ε)n; see [17]. Dillencourt et al [26] studied the geometric thickness of K n , and proved that 5…”
Section: Open Problemsmentioning
confidence: 99%
“…Testing whether a graph has book thickness at most 2 is N P-complete [76]. Dillencourt et al [26] asked what is the complexity of determining the geometric thickness of a given graph? The same question can be asked for all of the other parameters discussed in this paper.…”
Consider a drawing of a graph G in the plane such that crossing edges are coloured differently. The minimum number of colours, taken over all drawings of G, is the classical graph parameter thickness. By restricting the edges to be straight, we obtain the geometric thickness. By additionally restricting the vertices to be in convex position, we obtain the book thickness. This paper studies the relationship between these parameters and treewidth.Our first main result states that for graphs of treewidth k, the maximum thickness and the maximum geometric thickness both equal ⌈k/2⌉. This says that the lower bound for thickness can be matched by an upper bound, even in the more restrictive geometric setting. Our second main result states that for graphs of treewidth k, the maximum book thickness equals k if k ≤ 2 and equals k + 1 if k ≥ 3. This refutes a conjecture of Ganley and Heath [Discrete Appl. Math. 109(3):215-221, 2001]. Analogous results are proved for outerthickness, arboricity, and star-arboricity.
“…Modified force-directed methods are used to visualize general graphs simultaneously such that the mental map is preserved up in [7]. Conceptually, the problem of simultaneously embedding graphs is the reverse of the geometric thickness problem [5].…”
Abstract. In this paper we consider the problem of simultaneous drawing of two graphs. The goal is to produce aesthetically pleasing drawings for the two graphs by means of a heuristic algorithm and with human assistance. Our implementation uses the DiamondTouch table, a multiuser, touch-sensitive input device, to take advantage of direct physical interaction of several users working collaboratively. The system can be downloaded at http://dt.cs.arizona.edu where it is also available as an applet.
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