Примеры использования Is planar на Английском языке и их переводы на Русский язык
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However, not every(3,6)-sparse graph is planar.
Not every 3-tree is planar, but the planar 3-trees are exactly the Apollonian networks.
However, not every locally outerplanar graph is planar.
The Hasse diagram of a lattice is planar if and only if its order dimension is at most two.
A version of this theorem proved by Wagner(1937) states that if a graph G is both K5-free and K3,3-free,then G is planar.
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The graph of a k-gonal prism has 2k vertices, and is planar with two k-gon faces and k quadrilateral faces.
One direction of Steinitz's theorem(the easier direction to prove)states that the graph of every convex polyhedron is planar and 3-connected.
Wagner's theorem states that a graph is planar if and only if it has neither K5 nor K3,3 as a minor.
Another result also sometimes known as Wagner's theorem states that a four-connected graph is planar if and only if it has no K5 minor.
Schnyder's theorem states that a graph G is planar if and only if the order dimension of P(G) is at most three.
Corollary 1 indicates to us that k-clique-sums of small graphs describe the rough structure H-free graphs when H is planar.
For the generalization to graphs in which every finite subgraph is planar(proved directly via Gödel's compactness theorem), see Rautenberg 2010.
The study of snarks had its origin in the 1880 work of P. G. Tait, who at that time had proved that the four color theorem is equivalent to the statement that no snark is planar.
Note that steps 1. and 2. result in an empty graph if H is planar, but the bounded number of vertices added in step 3. makes the statement consistent with Corollary 1.
A graph G is subhamiltonian if G is a subgraph of another graph aug(G) on the same vertex set,such that aug(G) is planar and contains a Hamiltonian cycle.
The theory of graph minors began with Wagner's theorem that a graph is planar if and only if its minors include neither the complete graph K5 nor the complete bipartite graph K3,3.
In graph theory, the crossing number cr(G) of a graph G is the lowest number of edge crossings of a plane drawing of the graph G. For instance,a graph is planar if and only if its crossing number is zero.
By Steinitz's theorem, the Goldner-Harary graph is a polyhedral graph: it is planar and 3-connected, so there exists a convex polyhedron having the Goldner-Harary graph as its skeleton.
A graph is planar if it can be drawn with its vertices as points in the Euclidean plane, and its edges as curves that connect these points, such that no two edge curves cross each other and such that the point representing a vertex lies on the curve representing an edge only when the vertex is an endpoint of the edge.
As they showed, when the base graph is biconnected,a graph constructed in this way is planar if and only if its base graph is outerplanar and the matching forms a dihedral permutation of its outer cycle.
If a given graph is planar, so are all its minors: vertex and edge deletion obviously preserve planarity, and edge contraction can also be done in a planarity-preserving way, by leaving one of the two endpoints of the contracted edge in place and routing all of the edges that were incident to the other endpoint along the path of the contracted edge.
Wagner published both theorems in 1937, subsequent to the 1930 publication of Kuratowski's theorem,according to which a graph is planar if and only if it does not contain as a subgraph a subdivision of one of the same two forbidden graphs K5 and K3,3.
An equivalent form of Whitney 's criterion is that a graph G is planar if and only if it has a dual graph whose graphic matroid is dual to the graphic matroid of G. A graph whose graphic matroid is dual to the graphic matroid of G is known as an algebraic dual of G. This, Whitney 's planarity criterion can be expressed succinctly as: a graph is planar if and only if it has an algebraic dual.
That is, the following three conditions are equivalent to each other: F is a minor-closed family of bounded-treewidth graphs;One of the finitely many forbidden minors characterizing F is planar; F is a minor-closed graph family that does not include all planar graphs.
A prototypical example of this phenomenon is Kuratowski's theorem,which states that a graph is planar(can be drawn without crossings in the plane) if and only if it does not contain either of two forbidden graphs, the complete graph K5 and the complete bipartite graph K3,3.
Mac Lane's planarity criterion uses this idea to characterize the planar graphs in terms of the cycle bases: a finite undirected graph is planar if and only if it has a sparse cycle basis or 2-basis, a basis in which each edge of the graph participates in at most two basis cycles.
He uses a slightly different formulation of the planarity criterion,according to which a graph is planar if and only if it has a set of(not necessarily simple) cycles covering every edge exactly twice, such that the only nontrivial relation among these cycles in C(G) is that their sum be zero.
Other planarity criteria, that characterize planar graphs mathematically but are less central to planarity testing algorithms,include Whitney 's planarity criterion that a graph is planar if and only if its graphic matroid is also cographic, Mac Lane 's planarity criterion characterizing planar graphs by the bases of their cycle spaces, Schnyder 's theorem characterizing planar graphs by the order dimension of an associated partial order, and Colin de Verdière 's planarity criterion using spectral graph theory.
Wheel graphs are planar graphs, and as such have a unique planar embedding.
The regular octahedron is a special case in which all three quadrilaterals are planar squares.