A visibility representation for graphs in three dimensions.
Abelian pattern avoidance in partial words
Pattern avoidance is an important topic in combinatorics on words which dates back to the beginning of the twentieth century when Thue constructed an infinite word over a ternary alphabet that avoids squares, i.e., a word with no two adjacent identical factors. This result finds applications in various algebraic contexts where more general patterns than squares are considered. On the other hand, Erdős raised the question as to whether there exists an infinite word that avoids abelian squares, i.e.,...
Abelian periods, partial words, and an extension of a theorem of Fine and Wilf
Recently, Constantinescu and Ilie proved a variant of the well-known periodicity theorem of Fine and Wilf in the case of two relatively prime abelian periods and conjectured a result for the case of two non-relatively prime abelian periods. In this paper, we answer some open problems they suggested. We show that their conjecture is false but we give bounds, that depend on the two abelian periods, such that the conjecture is true for all words having length at least those bounds and show that some...
Acyclic, star and oriented colourings of graph subdivisions.
Affinely self-generating sets and morphisms.
Algebraic and graph-theoretic properties of infinite -posets
A -labeled -poset is an (at most) countable set, labeled in the set , equipped with partial orders. The collection of all -labeled -posets is naturally equipped with binary product operations and -ary product operations. Moreover, the -ary product operations give rise to
Algebraic and graph-theoretic properties of infinite n-posets
A Σ-labeled n-poset is an (at most) countable set, labeled in the set Σ, equipped with n partial orders. The collection of all Σ-labeled n-posets is naturally equipped with n binary product operations and nω-ary product operations. Moreover, the ω-ary product operations give rise to nω-power operations. We show that those Σ-labeled n-posets that can be generated from the singletons by the binary and ω-ary product operations form the free algebra on Σ in a variety axiomatizable by an infinite collection...
Algorithm engineering for optimal graph bipartization.
Algorithmic aspects of bipartite graphs.
Algorithms 62-64. Graph-theoretic algorithms for sparse matrix transformations
Algorithms and experiments for the Webgraph.
Algorithms for cluster busting in anchored graph drawing.
Algorithms for Finding Unitals and Maximal Arcs in Projective Planes of Order 16
The paper has been presented at the International Conference Pioneers of Bulgarian Mathematics, Dedicated to Nikola Obreshkoff and Lubomir Tschakalo ff , Sofia, July, 2006.Two heuristic algorithms (M65 and M52) for finding respectively unitals and maximal arcs in projective planes of order 16 are described. The exact algorithms based on exhaustive search are impractical because of the combinatorial explosion (huge number of combinations to be checked). Algorithms M65 and M52 use unions of orbits...
Algorithms for incremental orthogonal graph drawing in three dimensions.
Algorithms for single link failure recovery and related problems.
Algorithms for weighted graph problems on the modified cellular graph automaton
An algorithm for deciding if a polyomino tiles the plane
For polyominoes coded by their boundary word, we describe a quadratic O(n2) algorithm in the boundary length n which improves the naive O(n4) algorithm. Techniques used emanate from algorithmics, discrete geometry and combinatorics on words.
An algorithm to compute the möbius function of the rotation lattice of binary trees
An almost naive algorithm for finding relative neighbourhood graphs in metrics
An analogue of the Thue-Morse sequence.