منابع مشابه
Substitution-closed pattern classes
The substitution closure of a pattern class is the class of all permutations obtained by repeated substitution. The principal pattern classes (those defined by a single restriction) whose substitution closure can be defined by a finite number of restrictions are classified by listing them as a set of explicit families.
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The cyclic closure of a permutation pattern class is defined as the set of all the cyclic rotations of its permutations. Examples of finitely based classes whose cyclic closure is also finitely based are given, as well as an example where the cyclic closure is not finitely based. Some enumerations of cyclic closures are computed.
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A non empty class C of connected spaces is said to be a closed class if it is closed under weak equivalences and pointed homotopy colimits. A closed class can be characterized as a non empty class of connected spaces which is closed under weak equivalences and is closed under certain simple operations: arbitrary wedges, homotopy push-outs and homotopy sequential colimits. The notion of a closed...
متن کاملPattern Classes of Permutations
Though still a relatively young subject within discrete mathematics, the study of pattern classes of permutations is one of the fastest growing and is useful in theoretical computer science as well as various areas of mathematics. There are two commonly used forms of notation for permutations: a1a2 . . . an denotes the permutation which sends i to ai for i = 1, 2, . . . , n, where each ai repre...
متن کاملSquare Roots of Minor Closed Graph Classes
Let G be a graph class. The square root of G contains all graphs whose square belong in G. We prove that if G is non-trivial and minor closed, then all graphs in its square root have carving-width bounded by some constant depending only on G. As a consequence, every square root of such a graph class has a linear time recognition algorithm.
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ژورنال
عنوان ژورنال: Journal of Combinatorial Theory, Series A
سال: 2011
ISSN: 0097-3165
DOI: 10.1016/j.jcta.2010.10.006