1,720,970 research outputs found
Decompositions For The Edge Colouring Of Reduced Indifference Graphs
No full textThe chromatic index problem - finding the minimum number of colours required for colouring the edges of a graph - is still unsolved for indifference graphs, whose vertices can be linearly ordered so that the vertices contained in the same maximal clique are consecutive in this order. We present new positive evidence for the conjecture: every non neighbourhood-overfull indifference graph can be edge coloured with maximum degree colours. Two adjacent vertices are twins if they belong to the same maximal cliques. A graph is reduced if it contains no pair of twin vertices. A graph is overfull if the total number of edges is greater than the product of the maximum degree by ⌊n/2⌋, where n is the number of vertices. We give a structural characterization for neighbourhood-overfull indifference graphs proving that a reduced indifference graph cannot be neighbourhood-overfull. We show that the chromatic index for all reduced indifference graphs is the maximum degree. We present two decomposition methods for edge colouring reduced indifference graphs with maximum degree colours. © 2002 Elsevier Science B.V. All rights reserved.29701/03/15145155Cai, L., Ellis, J.A., NP-completeness of edge-colouring some restricted graphs (1991) Discrete Appl. Math., 30, pp. 15-27De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., A linear-time algorithm for proper interval graph recognition (1995) Inform. Process. Lett., 56, pp. 179-184De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., On edge-colouring indifference graphs (1997) Theoret. Comput. Sci., 181, pp. 91-106De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., Total-chromatic number and chromatic index of dually chordal graphs (1999) Inform. Process. Lett., 70, pp. 147-152De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., Local conditions for edge-coloring (2000) J. Combin. Math. Combin. Comput., 32, pp. 79-91. , Tech. Rep., DCC 17/95, UNICAMP, 1995Gutierrez, M., Oubiña, L., Minimum proper interval graphs (1995) Discrete Math., 142, pp. 77-85Hammer, P.L., Peled, U.N., Sun, X., Difference graphs (1990) Discrete Appl. Math., 28, pp. 35-44Hedman, B., Clique graphs of time graphs (1984) J. Combin. Theory Ser. B, 37, pp. 270-278Hilton, A.J.W., Two conjectures on edge-colouring (1989) Discrete Math., 74, pp. 61-64Holyer, I., The NP-completeness of edge-coloring (1981) SIAM J. Comput., 10, pp. 718-720Misra, J., Gries, D., A constructive proof of Vizing's theorem (1992) Inform. Process. Lett., 41, pp. 131-133Roberts, F.S., On the compatibility between a graph and a simple order (1971) J. Combin. Theory Ser. B, 11, pp. 28-38Vizing, V.G., On an estimate of the chromatic class of a p-graph (1964) Diskrete Anal., 3, pp. 25-30. , (in Russian
Edge Colouring Reduced Indifference Graphs
No full textThe chromatic index problem - finding the minimum number of colours required for colouring the edges of a graph - is still unsolved for indifference graphs, whose vertices can be linearly ordered so that the vertices contained in the same maximal clique are consecutive in this order. Two adjacent vertices are twins if they belong to the same maximal cliques. A graph is reduced if it contains no pair of twin vertices. A graph is overfull if the total number of edges is greater than the product of the maximum degree by [n/2], where n is the number of vertices. We give a structural characterization for neighbourhood-overfull indifference graphs proving that a reduced indifference graph cannot be neighbourhood-overfull. We show that the chromatic index for all reduced indifference graphs is the maximum degree. © Springer-Verlag Berlin Heidelberg 2000.1776 LNCS145153Cai, L., Ellis, J.A., NP-completeness of edge-colouring some restricted graphs (1991) Discrete Appl. Math., 30, pp. 15-27De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., A linear-time algorithm for proper interval graph recognition (1995) Inform. Process. Lett., 56, pp. 179-184De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., Local conditions for edge-coloring (1995) J. Combin. Mathematics and Combin. Computing, 31. , Technical report, DCC 17/95, UNICAMP To appearDe Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., On edge-colouring indifference graphs (1997) Theoret. Comput. Sci., 181, pp. 91-106De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., Total-chromatic number and chromatic index of dually chordal graphs (1999) Inform. Process. Lett., 70, pp. 147-152Gutierrez, M., Oubinã, L., Minimum proper interval graphs (1995) Discrete Math., 142, pp. 77-85Hedman, B., Clique graphs of time graphs (1984) J. Combin. Theory Ser. B, 37, pp. 270-278Hilton, A.J.W., Two conjectures on edge-colouring (1989) Discrete Math., 74, pp. 61-64Holyer, I., The NP-completeness of edge-coloring (1981) SIAM J. Comput., 10, pp. 718-720Misra, J., Gries, D., A constructive proof of vizing's theorem (1992) Inform. Process. Lett., 41, pp. 131-133Roberts, F.S., On the compatibility between a graph and a simple order (1971) J. Combin. Theory Ser. B, 11, pp. 28-38Vizing, V.G., On an estimate of the chromatic class of a p-graph (1964) Diskrete Analiz., 3, pp. 25-30. , In Russia
A Result On The Total Colouring Of Powers Of Cycles
No full textThe total chromatic number χT (G) is the least number of colours needed to colour the vertices and edges of a graph G such that no incident or adjacent elements (vertices or edges) receive the same colour. The Total Colouring Conjecture (TCC) states that for every simple graph G, χT (G) ≤ Δ(G)+2. This work verifies the TCC for powers of cycles Cnk, n even and 2 < k < ⌊n/2⌋, showing that there exists and can be polynomially constructed a (Δ(G) + 2)-total colouring for these graphs. © 2004 Elsevier B.V. All rights reserved.184752Behzad, M., Chartrand, G., Cooper Jr., J.K., The colour numbers of complete graphs (1967) J. London Mathematics Society, 42, pp. 226-228Campos, C.N., de Mello, C.P., Coloração total do Cn2 (2003) Tendências em Matemtática Aplicada e Computacional, 4 (2), pp. 177-186McDiarmid, C.J.H., Sánchez-Arroyo, A., Total colouring regular bipartite graphs is NP-hard (1994) Discrete Mathematics, 124, pp. 155-162Sánchez-Arroyo, A., Determining the total colouring number is NP-hard (1989) Discrete Mathematics, 78, pp. 315-319Vizing, V.G., On an estimate of the chromatic class of a p-graph (1964) Metody Diskret. Analiz., 3, pp. 25-30. , In RussianYap, H.P., Total colourings of graphs (1996) Lecture Notes in Mathematics, 1623. , Springer, Berli
On Edge-colouring Indifference Graphs
No full textVizing's theorem states that the chromatic index χ′(G) of a graph G is either the maximum degree Δ(G) or Δ(G) + 1. A graph G is called overfull if \E(G)| > Δ(G)[\V(G)|/2]. A sufficient condition for χ′(G) = Δ(G) + 1 is that G contains an overfull subgraph H with Δ(H) = Δ(G). Plantholt proved that this condition is necessary for graphs with a universal vertex. In this paper, we conjecture that, for indifference graphs, this is also true. As supporting evidence, we prove this conjecture for general graphs with three maximal cliques and with no universal vertex, and for indifference graphs with odd maximum degree. For the latter subclass, we prove that χ′ = Δ.181191106Cai, L., Ellis, J.A., NP-completeness of edge-colouring some restricted graphs (1991) Discrete Appl. Math., 30, pp. 15-27De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., A greedy method for edge-colouring odd maximum degree doubly chordal graphs (1995) Congressus Numerantium, 111, pp. 170-176De Figueiredo, C.M.H., Meidanis, J., De Mello, C.P., A lexbfs algorithm for proper interval graph recognition (1995) Inform. Process. Lett., 56, pp. 179-184Hilton, A.J.W., Two conjectures on edge-colouring (1989) Discrete Math., 74, pp. 61-64Hoffman, D.G., Rodger, C.A., The chromatic index of complete multipartite graphs (1992) J. Graph Theory, 16, pp. 159-163Holyer, I., The NP-completeness of edge-coloring (1981) SIAM J. Comput., 10, pp. 718-720Ortiz, C., (1994) Sobre Coloração de Arestas, , Ph.D. Thesis, COPPE-UFRJ, Rio de Janeiro, in portugueseOrtiz, C., Maculan, N., Szwarcfiter, J.L., (1996) Characterizing and Edge Colouring Split-indifference Graphs, , manuscriptPadberg, M.W., Rao, M.R., Odd minimum cut-sets and b-matching (1982) Math. Oper. Res., 7, pp. 67-80Plantholt, M., The chromatic index of graphs with a spanning star (1981) J. Graph Theory, 5, pp. 45-53Plantholt, M., The chromatic index of graphs with large maximum degree (1983) Discrete Math., 47, pp. 91-96Roberts, F.S., On the compatibility between a graph and a simple order (1971) J. Combin. Theory Ser. B, 11, pp. 28-38Vizing, V.G., On an estimate of the chromatic class of a p-graph (1964) Diket. Analiz., 3, pp. 25-30. , in Russia
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Clique Operator On Graphs With Few P4's
No full textThe clique graph of a graph G is the intersection graph K(G) of the (maximal) cliques of G. The iterated clique graphs Kn(G) are defined by K0(G)=G and Ki(G)=K(Ki-1(G)),i>0 and K is the clique operator. In this article we use the modular decomposition technique to characterize the K-behaviour of some classes of graphs with few P4's . These characterizations lead to polynomial time algorithms for deciding the K-convergence or K-divergence of any graph in the class. © 2005 Elsevier B.V. All rights reserved.1543485492Babel, L., Kloks, T., Kratochvíl, J., Kratsch, D., Müller, H., Olariu, S., Efficient algorithms for graphs with few P4's (2001) Discrete Math., 235, pp. 29-51Bandelt, H.-J., Prisner, E., Clique graphs and Helly graphs (1991) J. Combin. Theory Ser. B, 51, pp. 34-45Bornstein, C.F., Szwarcfiter, J.L., On clique convergent graphs (1995) Graphs Combin., 11, pp. 213-220Cheen, B.-L., Lih, K.-W., Diameters of iterated clique graphs of chordal graphs (1990) J. Graph Theory, 14, pp. 391-396Cournier, A., Habib, M., A new linear algorithms for modular decomposition (1994) Lecture Notes in Computer Science, 787, pp. 68-84. , Springer, BerlinEscalante, F., Über iterierte clique-graphen (1973) Abh. Math. Sem. Univ. Hamburg, 39, pp. 59-68Frias, M.E., Neumann-Lara, V., Pizaña, M., Dismantlings and iterated clique graphs (2004) Discrete Math., 282, pp. 263-265Giakoumakis, V., Vanherpe, J.-M., On extended P4P-reducible and extended P4-sparse graphs (1997) Theoret. Comput. Sci., 180, pp. 269-286Giakoumakis, V., Roussel, F., Thuillier, H., On P4-tidy graphs (1997) Discrete Math. Theoret. Comput. Sci., 1, pp. 17-41Hamelink, R., A partial characterization of clique graphs (1968) J. Combin. Theory, 5, pp. 192-197Hoang, C., (1985), Doctoral Dissertation, McGill University Montreal, QuebecJamison, B., Olariu, S., A new class of brittle graphs (1989) Stud. Appl. Math., 81, pp. 89-92Jamison, B., Olariu, S., P4-reducible graphs, a class of uniquely tree representable graphs (1989) Stud. Appl. Math., 81, pp. 79-87Jamison, B., Olariu, S., On a unique tree representation for P4-extendible graphs (1991) Discrete Appl. Math., 34, pp. 151-164Jamison, B., Olariu, S., A tree representation for P4-sparse graphs (1992) Discrete Appl. Math., 35, pp. 115-129Larrión, F., De Mello, C.P., Morgana, A., Neumann-Lara, V., Pizaña, M., The clique operator on cographs and serial graphs (2004) Discrete Math., 282, pp. 183-191Larrión, F., Neumann-Lara, V., Clique divergent graphs with unbounded sequence of diameter (1999) Discrete Math., 197-198, pp. 491-501Larrión, F., Neumann-Lara, V., Locally C6 graphs are clique divergent (2000) Discrete Math., 215, pp. 159-170Larrión, F., Neumann-Lara, V., On clique divergent graphs with linear growth (2001) Discrete Math., 245, pp. 139-153Larrión, F., Neumann-Lara, V., Pizaña, M., Whitney triangulations, local girth and iterated clique graphs (2002) Discrete Math., 258, pp. 123-135McConnell, R.M., Spinrad, J.P., Modular decomposition and transitive orientation (1999) Discrete Math., 201, pp. 189-206Neumann-Lara, V., On clique-divergent graphs (1978) Colloq. Internat. CNRS, 260, pp. 313-315. , Problèmes Combinatoires et Théorie des GraphesNeumann-Lara, V., Clique-divergence in graphs (1978) Coll. Math. Soc. Janos Bolyai, 25, pp. 563-569. , Algebraic Methods in Graph Theory, Szeged, Húngary North-Holland, AmsterdamNeumann-Lara, V., Theory of Clique Expansive Graphs, , unpublished manuscriptPizaña, M.A., The icosahedron is clique divergent (2003) Discrete Math., 262, pp. 229-239Prisner, E., Convergence of iterated clique graphs (1992) Discrete Math., 103, pp. 199-207Prisner, E., Hereditary Helly graphs (1993) J. Combin. Math. Combin. Comput., 14, pp. 216-220Prisner, E., Graph dynamics (1995) Pitman Research Notes in Mathematics, 338. , Longman, New YorkSzwarcfiter, J.L., Recognizing clique-Helly graphs (1997) Ars. Combin., 45, pp. 29-32Szwarcfiter, J.L., A survey on clique graphs (2003) Recent Advances in Algorithms and Combinatorics, CMS Books in Mathematics, pp. 109-136. , C. Linhares B. Reed Springer Berli
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
