Connectivity of the lifts of a greedoid.
Connectivity, toughness, spanning trees of bounded degree, and the spectrum of regular graphs
The eigenvalues of graphs are related to many of its combinatorial properties. In his fundamental work, Fiedler showed the close connections between the Laplacian eigenvalues and eigenvectors of a graph and its vertex-connectivity and edge-connectivity. We present some new results describing the connections between the spectrum of a regular graph and other combinatorial parameters such as its generalized connectivity, toughness, and the existence of spanning trees with bounded degree.
Consecutive patterns: from permutations to column-convex polyominoes and back.
Consequences of a sextuple-product identity.
Conservation of the integrality of certain quotients by iterated substitutions of Lucas numbers.
Consistent cycles in 1/2-arc-transitive graphs.
Constante de Cheeger et première valeur propre non nulle du Laplacien d’un graphe de petite dimension
Constrained and generalized barycentric Davenport constants.
Constrained Colouring and σ-Hypergraphs
A constrained colouring or, more specifically, an (α, β)-colouring of a hypergraph H, is an assignment of colours to its vertices such that no edge of H contains less than α or more than β vertices with different colours. This notion, introduced by Bujtás and Tuza, generalises both classical hypergraph colourings and more general Voloshin colourings of hypergraphs. In fact, for r-uniform hypergraphs, classical colourings correspond to (2, r)-colourings while an important instance of Voloshin colourings...
Constrained Steiner trees in Halin graphs
In this paper, we study the problem of computing a minimum cost Steiner tree subject to a weight constraint in a Halin graph where each edge has a nonnegative integer cost and a nonnegative integer weight. We prove the NP-hardness of this problem and present a fully polynomial time approximation scheme for this NP-hard problem.
Constrained Steiner trees in Halin graphs
In this paper, we study the problem of computing a minimum cost Steiner tree subject to a weight constraint in a Halin graph where each edge has a nonnegative integer cost and a nonnegative integer weight. We prove the NP-hardness of this problem and present a fully polynomial time approximation scheme for this NP-hard problem.
Constrainted graph processes.
Constructing 5-configurations with chiral symmetry.
Constructing a Canonical form of a Matrix in Several Problems about Combinatorial Designs
Partially supported by the Bulgarian Science Fund contract with TU Varna, No 487.The author developed computer programs needed for the classification of designs with certain automorphisms by the local approach method. All these programs use canonicity test or/and construction of canonical form of an integer matrix. Their efficiency substantially influences the speed of the whole computation. The present paper deals with the implemented canonicity algorithm. It is based on ideas used by McKay, Meringer,...
Constructing and embedding mutually orthogonal Latin squares: reviewing both new and existing results
We review results for the embedding of orthogonal partial Latin squares in orthogonal Latin squares, comparing and contrasting these with results for embedding partial Latin squares in Latin squares. We also present a new construction that uses the existence of a set of mutually orthogonal Latin squares of order to construct a set of mutually orthogonal Latin squares of order .
Constructing and forbidding automorphisms in lifted maps
Constructing cospectral graphs.
Constructing fifteen infinite classes of nonregular bipartite integral graphs.
Constructing hypohamiltonian snarks with cyclic connectivity 5 and 6.
Constructing regular maps and graphs from planar quotients