Примеры использования Perfect graph на Английском языке и их переводы на Русский язык
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The perfect graph theorem states: The complement of a perfect graph is perfect. .
Alternatively, the imperfection of this graph follows from the perfect graph theorem and the imperfection of the complementary odd cycle.
By the perfect graph theorem, the complement of G(an"odd antihole") must therefore also not be perfect. .
Because this characterization isunaffected by graph complementation, it immediately implies the weak perfect graph theorem.
By the strong perfect graph theorem, the perfect graphs are the graphs with no odd hole and no odd antihole.
Then the comparability graph of T is trivially perfect, and every trivially perfect graph can be formed in this way.
A perfect graph is a graph in which the clique number equals the chromatic number in every induced subgraph.
Because these three types of biconnected component are all perfect graphs themselves, every line perfect graph is itself perfect. .
The perfect graph theorem is the special case of this result when one of the three subgraphs is the empty graph. .
Because these graphs are not perfect, every perfect graph must be a Berge graph, a graph with no odd holes and no odd antiholes.
The perfect graph theorem has a short proof, but the proof of the strong perfect graph theorem is long and technical, based on a deep structural decomposition of Berge graphs. .
Because Berge's forbidden graph characterization is self-complementary,the weak perfect graph theorem follows immediately from the strong perfect graph theorem.
Equivalently, in a perfect graph, the size of the maximum independent set equals the minimum number of cliques in a clique cover.
This idea was based on previous conjectured structural decompositions of similar type that would have implied the strong perfect graph conjecture but turned out to be false.
The first use of the phrase"perfect graph" appears to be in a 1963 paper of Claude Berge, after whom Berge graphs are named.
The set of all pairs of vertices in this tree-decomposition that both belong to a common node of the tree-decomposition forms a trivially perfect graph with O(n3/2) vertices that contains every n-vertex planar graph as a subgraph.
According to the strong perfect graph theorem, induced cycles and their complements play a critical role in the characterization of perfect graphs. .
If a graph family F is closed under the operation of taking induced subgraphs, then every graph in F is also locally F. For instance,every chordal graph is locally chordal; every perfect graph is locally perfect; every comparability graph is locally comparable.
Thus, the perfect graph theorem can be used to prove Dilworth's theorem from the(much easier) proof of Mirsky's theorem, or vice versa.
This result had been conjectured by Berge(1961, 1963), andit is sometimes called the weak perfect graph theorem to distinguish it from the strong perfect graph theorem characterizing perfect graphs by their forbidden induced subgraphs.
A perfect graph is a graph in which the chromatic number and the size of the maximum clique are equal, and in which this equality persists in every induced subgraph.
In 1960, Claude Berge formulated another conjecture about graph coloring, the strong perfect graph conjecture, originally motivated by an information-theoretic concept called the zero-error capacity of a graph introduced by Shannon.
A perfect graph is an undirected graph with the property that, in every one of its induced subgraphs, the size of the largest clique equals the minimum number of colors in a coloring of the subgraph.
Chudnovsky& Seymour(2005) overview a series of papers in which they prove a structure theory for claw-free graphs, analogous to the graph structure theorem for minor-closed graph families proven by Robertson and Seymour, and to the structure theory for perfect graphs that Chudnovsky, Seymour andtheir co-authors used to prove the strong perfect graph theorem.
For odd values of n, Wn is a perfect graph with chromatic number 3: the vertices of the cycle can be given two colors, and the center vertex given a third color.
Every graph that is both a trivially perfect graph and the complementary graph of a trivially perfect graph is a threshold graph. .
The strong perfect graph theorem was proven for bull-free graphs long before its proof for general graphs, and a polynomial time recognition algorithm for Bull-free perfect graphs is known.
It follows from the equivalent characterizations of trivially perfect graphs that every trivially perfect graph is also a cograph, a chordal graph, a Ptolemaic graph, an interval graph, and a perfect graph. .
As the strong perfect graph theorem states, the odd holes and odd antiholes turn out to be the minimal forbidden induced subgraphs for the perfect graphs. .
This became known as the strong perfect graph conjecture, until its proof in 2002, when it was renamed the strong perfect graph theorem.