Yazar "Das, Kinkar Ch." seçeneğine göre listele

Listeleniyor 1 - 9 / 9
  • Küçük Resim
    Öğe
    Improved Upper and Lower Bounds for the Spectral Radius of Digraphs
    (Elsevier Science Inc, 2010) Güngör, A. Dilek; Das, Kinkar Ch.
    Let G be a digraph with n vertices and m arcs without loops and multiarcs. The spectral radius rho(G) of G is the largest eigenvalue of its adjacency matrix. In this paper, sharp upper and lower bounds on rho(G) are given. We show that some known bounds can be obtained from our bounds.
  • Küçük Resim Yok
    Öğe
    Minimality over free monoid presentations
    (HACETTEPE UNIV, FAC SCI, 2014) Cevik, A. Sinan; Das, Kinkar Ch.; Cangul, I. Naci; Maden, A. Dilek
    As a continues study of the paper [4], in here, we first state and prove the p-Cockcroft property (or, equivalently, efficiency) for a presentation, say PE, of the semi-direct product of a free abelian monoid rank two by a finite cyclic monoid. Then, in a separate section, we present sufficient conditions on a special case for PE to be minimal whilst it is inefficient.
  • Küçük Resim Yok
    Öğe
    On a graph of monogenic semigroups
    (SPRINGER INTERNATIONAL PUBLISHING AG, 2013) Das, Kinkar Ch.; Akgüneş, Nihat; Çevik, A. Sinan
    Let us consider the finite monogenic semigroup S-M with zero having elements {x, x(2), x(3), ... , x(n)}. There exists an undirected graph Gamma (S-M) associated with S-M whose vertices are the non-zero elements x, x(2), x(3), ... , x(n) and, f or 1 <= i, j <= n, any two distinct vertices xi and xj are adjacent if i + j > n. In this paper, the diameter, girth, maximum and minimum degrees, domination number, chromatic number, clique number, degree sequence, irregularity index and also perfectness of Gamma (S-M) have been established. In fact, some of the results obtained in this section are sharper and stricter than the results presented in DeMeyer et al. (Semigroup Forum 65:206-214, 2002). Moreover, the number of triangles for this special graph has been calculated. In the final part of the paper, by considering two (not necessarily different) graphs Gamma (S-M(1)) and Gamma (S-M(2)), we present the spectral properties to the Cartesian product Gamma (S-M(1)) square Gamma (S-M(2)).
  • Küçük Resim Yok
    Öğe
    On Average Eccentricity of Graphs
    (NATL ACAD SCIENCES INDIA, 2017) Das, Kinkar Ch.; Maden, A. Dilek; Cangul, I. Naci; Cevik, A. Sinan
    The eccentricity of a vertex is the maximum distance from it to any other vertex and the average eccentricity avec(G) of a graph G is the mean value of eccentricities of all vertices of G. In this paper we present some lower and upper bounds for the average eccentricity of a connected (molecular) graph in terms of its structural parameters such as number of vertices, diameter, clique number, independence number and the first Zagreb index. Also, we obtain a relation between average eccentricity and first Zagreb index. Moreover, we compare average eccentricity with graph energy, ABC index and index.
  • Küçük Resim Yok
    Öğe
    On Laplacian Energy
    (UNIV KRAGUJEVAC, FAC SCIENCE, 2013) Das, Kinkar Ch.; Gutman, Ivan; Cevik, A. Sinan; Zhou, Bo
    Let G be a connected graph of order n with Laplacian eigenvalues mu(1) >= mu(2) >= ... >= mu(n-1) > mu(n) = 0. The Laplacian energy of the graph G is defined as LE = LE(G) = (n)Sigma(i=1)vertical bar mu(i)-2m/n vertical bar. Upper bounds for LE are obtained, in terms of n and the number of edges m.
  • Küçük Resim Yok
    Öğe
    On the Laplacian-energy-like invariant
    (ELSEVIER SCIENCE INC, 2014) Das, Kinkar Ch.; Gutman, Ivan; Cevik, A. Sinan
    Let G be a connected graph of order n with Laplacian eigenvalues mu(1) >= mu(2) >= ... mu(n-1) >mu(n) = 0. The Laplacian-energy-like invariant of the graph G is defined as LEL = LEL(G) = Sigma(n-1)(i=1)root mu(i) . Lower and upper bounds for LEL are obtained, in terms of n, number of edges, maximum vertex degree, and number of spanning trees. (C) 2013 Elsevier Inc. All rights reserved.
  • Küçük Resim Yok
    Öğe
    On the normalized Laplacian eigenvalues of graphs
    (CHARLES BABBAGE RES CTR, 2015) Das, Kinkar Ch.; Gungor, A. Dilek; Bozkurt, S. Burcu
    Let G = (V, E) be a simple connected graph with n vertices and m edges. Further let lambda(i)(L), i = 1, 2, ..., n, be the non-increasing eigenvalues of the normalized Laplacian matrix of the graph G. In this paper, we obtain the following result: For a connected graph G of order n, lambda(2)(L) = lambda(3)(L) = ... = lambda(n-1)(L) if and only if G is a complete graph K-n or G is a complete bipartite graph K-p,K- q. Moreover, we present lower and upper bounds for the normalized Laplacian spectral radius of a graph and characterize graphs for which the lower or upper bounds is attained.
  • Küçük Resim Yok
    Öğe
    Sharp upper bounds on the spectral radius of the signless Laplacian matrix of a graph
    (ELSEVIER SCIENCE INC, 2013) Maden, A. Dilek (Gungor); Das, Kinkar Ch.; Cevik, A. Sinan
    Let G = (V, E) be a simple connected graph. Denote by D(G) the diagonal matrix of its vertex degrees and by A(G) its adjacency matrix. Then the signless Laplacian matrix of G is Q(G) = D(G) + A(G). In this paper, we obtain some new and improved sharp upper bounds on the spectral radius q(1)(G) of the signless Laplacian matrix of a graph G. (C) 2012 Elsevier Inc. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Some properties on the tensor product of graphs obtained by monogenic semigroups
    (ELSEVIER SCIENCE INC, 2014) Akgüneş, Nihat; Das, Kinkar Ch.; Çevik, A. Sinan
    In Das et al. (2013) [8], a new graph 1'(S-M) on monogenic semigroups S-M (with zero) having elements {0, x, x(2), x(3),..., x(n)} has been recently defined. The vertices are the non-zero elements x; x(2); x(3);..., x(n) and, for 1 <= i,j <= n, any two distinct vertices x(i) and x(j) are adjacent if x(i)x(j) = 0 in S-M. As a continuing study, in Akgunes et al. (2014) [3], it has been investigated some well known indices (first Zagreb index, second Zagreb index, Randic index, geometric-arithmetic index, atom-bond connectivity index, Wiener index, Harary index, first and second Zagreb eccentricity indices, eccentric connectivity index, the degree distance) over Gamma(S-M). In the light of above references, our main aim in this paper is to extend these studies over Gamma(S-M) to the tensor product. In detail, we will investigate the diameter, radius, girth, maximum and minimum degree, chromatic number, clique number and domination number for the tensor product of any two (not necessarily different) graphs Gamma(S-M)(1) and Gamma(S-M(2)). (C) 2014 Published by Elsevier Inc.