Примеры использования Planar graph has на Английском языке и их переводы на Русский язык
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In particular, every planar graph has a planar arc diagram.
One direction of the characterisation states that every planar graph has a 2-basis.
In particular, a planar graph has genus 0{\displaystyle 0}, because it can be drawn on a sphere without self-crossing.
Heath, Leighton& Rosenberg(1992) conjectured that every planar graph has bounded queue number.
For instance, a maximal planar graph has such an embedding if and only if it contains a Hamiltonian cycle.
In the language of homomorphisms, Grötzsch's theorem states that every triangle-free planar graph has a homomorphism to K3.
However, every planar graph has an arc diagram in which each edge is drawn as a biarc with at most two semicircles.
That is, a separator formed in thisway has width O(√n), and can be used to show that every planar graph has treewidth O√n.
A slightly more general result is true: if a planar graph has at most three triangles then it is 3-colorable.
Every planar graph has an algebraic dual, which is in general not unique any dual defined by a plane embedding will do.
More strongly, by the same argument, if a maximal planar graph has a cycle of length k, it has cycles of all smaller lengths.
As any planar graph has arboricity three, the thickness of any graph is at least equal to a third of the arboricity, and at most equal to the arboricity.
If min(a, b)≤ 2, then the graph is a planar graph, and(by Fáry's theorem)every planar graph has a straight-line drawing with no crossings.
Every finite planar graph has a vertex of degree five or less; therefore, every planar graph is 5-degenerate, and the degeneracy of any planar graph is at most five.
Additionally, he proved that, with a single exception(the eight-vertex complement graph of the cube)every nearly planar graph has an embedding onto the projective plane.
As Keszegh, Pach& Pálvölgyi(2011) showed, every planar graph has a planar straight-line drawing in which the number of distinct slopes is a function of the degree of the graph. .
In 2009, Dvořák, Kráľ, and Thomas announced a proof of another generalization, conjectured in 1969 by L. Havel:there exists a constant d such that, if a planar graph has no two triangles within distance d of each other, then it can be colored with three colors.
Chalopin, Gonçalves& Ochem(2007)proved that every planar graph has a string representation in which each pair of strings has at most one crossing point, unlike the representations described above.
The width of any separation in this decomposition is, again, bounded by the sum of the sizes of the separators on a path from any node to the root of the hierarchy,so any branch-decomposition formed in this way has width O(√n) and any planar graph has branchwidth O√n.
By combining these two results,it may be shown that every triangle-free planar graph has a homomorphism to a triangle-free 3-colorable graph, the tensor product of K3 with the Clebsch graph. .
Fáry's theorem states that every planar graph has a drawing in which its edges are represented by straight line segments, and the same is true of upward planar drawing: every upward planar graph has a straight upward planar drawing.
Applying the simple cycle separator theorem of Gazit& Miller(1990) to the dual graph of a given planar graph strengthens the O(√(Δn))bound for the size of an edge separator by showing that every planar graph has an edge separator whose size is proportional to the Euclidean norm of its vector of vertex degrees.
A universal point set of order n is a set S of points in the Euclidean plane with the property that every n-vertex planar graph has a straight-line drawing in which the vertices are all placed at points of S. When n is ten or less, there exist universal point sets with exactly n points, but for all n≥ 15 additional points are required.
In 1967, Kasteleyn proved that planar graphs have an efficiently computable Pfaffian orientation.
Wagner's theorem, which characterizes the planar graphs by their forbidden minors,implies that the planar graphs have Hadwiger number at most four.
Based on the existence of such examples, Bernhart and Kainen conjectured that the book thickness of planar graphs could be made arbitrarily large, butit was subsequently shown that all planar graphs have book thickness at most four.
For instance, the linear forests have invariant 1, and can be 2-colored; the outerplanar graphs have invariant two, andcan be 3-colored; the planar graphs have invariant 3, and(by the four color theorem) can be 4-colored.
Therefore, the planar graphs have a forbidden minor characterization, which in this case is given by Wagner's theorem: the set H of minor-minimal nonplanar graphs contains exactly two graphs, the complete graph K5 and the complete bipartite graph K3,3, and the planar graphs are exactly the graphs that do not have a minor in the set{K5, K3,3.
The inversive distance has been used to define the concept of an inversive-distance circle packing:a collection of circles such that a specified subset of pairs of circles(corresponding to the edges of a planar graph) have a given inversive distance with respect to each other.
More generally, it can be shown using the Euler characteristic that all n-vertex planar graphs have at most 2n- 5 bounded faces(not counting the one unbounded face) and that if there are m edges then the number of bounded faces is m- n+ 1 the same as the circuit rank of the graph. .