Results 11 to 20 of about 352 (164)
Well quasi-order in combinatorics : embeddings and homomorphisms
, 2015 The notion of well quasi-order (wqo) from the theory of ordered sets often arises naturally in contexts where one deals with infinite collections of structures which can somehow be compared, and it then represents a useful discriminator between ‘tame ...
Ruskuc, Nik +3 more
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Pattern classes of permutations via bijections between linearly ordered sets
, 2008 A pattern class is a set of permutations closed under pattern involvement or, equivalently, defined by certain subsequence avoidance conditions. Any pattern class X which is atomic, i.e.
Ruškuc, Nik +2 more
core +1 more source
Geometric grid classes of permutations
, 2012 A geometric grid class consists of those permutations that can be drawn on a specified set of line segments of slope ±1 arranged in a rectangular pattern governed by a matrix.
Atkinson, M.D. +8 more
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Inflations of geometric grid classes of permutations
, 2015 All three authors were partially supported by EPSRC via the grant EP/J006440/1.Geometric grid classes and the substitution decomposition have both been shown to be fundamental in the understanding of the structure of permutation classes.
Ruskuc, Nik, Albert, M.D., Vatter, V.
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An inequality for the weights of two families of sets, their unions and intersections
, 1978 Ahlswede R, Daykin DE. An inequality for the weights of two families of sets, their unions and intersections. Zeitschrift für Wahrscheinlichkeitstheorie und verwandte Gebiete.
Ahlswede, Rudolf, Daykin, David E.
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Generating transformation semigroups using endomorphisms of preorders, graphs, and tolerances
, 2010 Let ΩΩ be the semigroup of all mappings of a countably infinite set Ω. If U and V are subsemigroups of ΩΩ, then we write U≈V if there exists a finite subset F of ΩΩ such that the subsemigroup generated by U and F equals that generated by V and F.
Morayne, Michal +11 more
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The extremals of Stanley's inequalities for partially ordered sets
, 2023 Stanley's inequalities for partially ordered sets establish important log-concavity relations for sequences of linear extensions counts. Their extremals however, i.e., the equality cases of these inequalities, were until now poorly understood with even ...
Ma, Zhao Yu, Shenfeld, Yair
core
On the dynamics of sup-norm non-expansive maps [PDF]
, 2005 We present several results for the periods of periodic points of sup-norm non-expansive maps. In particular, we show that the period of each periodic point of a sup-norm non-expansive map $f\colon M\to M$, where $M\subset \mathbb{R}^n$, is at most ...
Lemmens, Bas +3 more
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On the Hardness of Switching to a Small Number of Edges
Journal of Graph Theory, EarlyView.ABSTRACT Seidel's switching is a graph operation which makes a given vertex adjacent to precisely those vertices to which it was non‐adjacent before, while keeping the rest of the graph unchanged. Two graphs are called switching‐equivalent if one can be made isomorphic to the other one by a sequence of switches. Jelínková et al. [DMTCS 13, no. 2, 2011]
Vít Jelínek +2 more
wiley +1 more source
Linear Versus Centred Colouring via Pseudogrids
Journal of Graph Theory, EarlyView.ABSTRACT A centred colouring of a graph is a vertex colouring in which every connected subgraph contains a vertex whose colour is unique and a linear colouring is a vertex colouring in which every (not‐necessarily induced) path contains a vertex whose colour is unique. For a graph G $G$, the centred chromatic number χ cen ( G ) ${\chi }_{\text{cen}}(G)$
Prosenjit Bose +4 more
wiley +1 more source