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1.
Wide diameter of Cartesian graph bundles
Iztok Banič, Janez Žerovnik, 2010, published scientific conference contribution

Abstract: Fault tolerance and transmission delay of networks are important concepts in network design. The notions are strongly related to connectivity and diameter of a graph, and have been studied by many authors. Wide diameter of a graph combines studying connectivity with the diameter of a graph. Diameter with width ▫$k$▫ of a graph ▫$G$▫, ▫$k$▫-diameter, is defined as the minimum integer ▫$d$▫ for which there exist at least ▫$k$▫ internally disjoint paths of length at most ▫$d$▫ between any two distinct vertices in ▫$G$▫. Denote by ▫${mathscr D}_c(G)$▫ the ▫$c$▫-diameter of ▫$G$▫ and ▫$kappa(G)$▫ the connectivity of ▫$G$▫. In the context of computer networks, wide diameters of Cartesian graph products have been recently studied by many authors. Cartesian graph bundles is a class of graphs that is a generalization of the Cartesian graph products. Let ▫$G$▫ be a Cartesian graph bundle with fiber ▫$F$▫ over base ▫$B$▫, ▫$0 < a le kappa(F)$▫, and ▫$0 < b le kappa(B)$▫. We prove that ▫${mathscr D}_{a+b}(G) le {mathscr D}_a(F) + {mathscr D}_b(B) + 1$▫. Moreover, if ▫$G$▫ is a graph bundle with fiber ▫$F ne K_2$▫ over base ▫$B ne K_2$▫, then ▫${mathscr D}_{a+b}(G) le {mathscr D}_a(F) + {mathscr D}_b(B)$▫. The bounds are tight.
Keywords: mathematics, graph theory, Cartesian graph products, Cartesian graph bundles, wide diameter
Published: 07.06.2012; Views: 1159; Downloads: 59
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2.
Fault-diameter of Cartesian product of graphs and Cartesian graph bundles
Iztok Banič, Janez Žerovnik, 2006

Abstract: Cartesian graph bundles is a class of graphs that is a generalization of the Cartesian graph products. Let ▫$G$▫ be a ▫$k_G$▫-connected graph and ▫${mathcal{D}}_c(G)$▫ denote the diameter of ▫$G$▫ after deleting any of its ▫$c < k_G$▫ vertices. We prove that if ▫$G_1, G_2, dots, G_q$▫ are ▫$k_1$▫-connected, ▫$k_2$▫-connected,...,▫$k_q$▫-connected graphs and ▫$0 leq a_1 < k_1$▫, ▫$0 leq a_2 < k_2$▫,...,▫$0 leq a_q < k_q$▫ and ▫$a = a_1 + a_2 + dots + a_q + (q-1)$▫, then the fault diameter of ▫$G$▫, a Cartesian product of ▫$G_1$▫, ▫$G_2$▫,...,▫$G_q$▫, with ▫$a$▫ faulty nodes is ▫${mathcal{D}}_{a}(G) leq {mathcal{D}}_{a_1}(G_1)+{mathcal{D}}_{a_2}(G_2) + dots + {mathcal{D}}_{a_q}(G_q) + 1$▫. We also show that ▫${mathcal{D}}_{a+b+1}(G) leq {mathcal{D}}_a(F) + {mathcal{D}}_b(B) + 1$▫ if ▫$G$▫ is a graph bundle with fibre ▫$F$▫ over base ▫$B$▫, ▫$a leq k_F$▫, and ▫$b leq k_B$▫. As an auxiliary result we prove that connectivity of graph bundle ▫$G$▫ is at least ▫$k_F+k_B$▫.
Keywords: mathematics, graph theory, Cartesian graph bundles, Cartesian graph products, fault diameter, interconnection network
Published: 10.07.2015; Views: 384; Downloads: 15
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3.
Algorithm for recognizing Cartesian graph bundles
Blaž Zmazek, Janez Žerovnik, 1999, published scientific conference contribution abstract

Abstract: Grafovski svežnji predstavljajo posplošitev krovnih in produktnih grafov. V članku vpeljemo enolično lokalno produktno relacijo ▫$Delta$▫ na kartezičnih svežnjih nad baznimi grafi, ki ne vsebujejo grafa ▫$K_4 setminus e$▫ in podamo algoritem za razpoznavanje kartezičnih svežnjev nad enostavnimi baznimi grafi brez ▫$K_4 setminus e$▫.
Keywords: matematika, teorija grafov, kartezični grafovski svežnji, enolična lokalna produktna lastnost, osnovna faktorizacija, razpoznavanje, polinomski algoritem, mathematics, graph theory, Cartesian graph bundles, unique square property, fundamental factorization, polynomial algorithm, recognition
Published: 10.07.2015; Views: 409; Downloads: 55
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4.
The edge fault-diameter of Cartesian graph bundles
Iztok Banič, Rija Erveš, Janez Žerovnik, 2009, original scientific article

Abstract: Kartezični svežnji so posplošitev krovnih grafov in kartezičnih grafovskih produktov. Naj bo ▫$G$▫ nek s povezavami ▫$k_G$▫-povezan graf in ▫${bar{mathcal{D}}_c(G)}$▫ največji premer podgrafov grafa ▫$G$▫ dobljenih z odstranitvijo $▫c < k_G$▫ povezav. Dokazano je, da je ▫${bar{mathcal{D}}_{a+b+1}(G)} le {bar{mathcal{D}}_a(F)} le {bar{mathcal{D}}_b(B)} + 1$▫, če je ▫$G$▫ grafovski sveženj z vlaknom ▫$F$▫ in bazo ▫$B$▫, ▫$a < k_F$▫, ▫$b < k_B▫$. Dokazano je tudi, da je povezanost s povezavami grafovskega svežnja ▫$G▫$ vsaj ▫$k_F + k_B$▫.
Keywords: matematika, teorija grafov, kartezični grafovski produkti, kartezični grafovski svežnji, povezavni okvarni premer, mathematics, graph theory, Cartesian graph products, Cartesian graph bundles, edge-fault diameter
Published: 10.07.2015; Views: 566; Downloads: 56
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5.
Recognizing weighted directed Cartesian graph bundles
Blaž Zmazek, Janez Žerovnik, 2000, original scientific article

Abstract: In this paper we show that methods for recognizing Cartesian graph bundles can be generalized to weighted digraphs. The main result is an algorithm which lists the sets of degenerate arcs for all representations of digraph as a weighted directed Cartesian graph bundle over simple base digraphs not containing transitive tournament on three vertices. Two main notions are used.The first one is the new relation ▫$\vec{\delta}^\ast$▫ defined among the arcs of a digraph as a weighted directed analogue of the well-known relation ▫$\delta^\ast$▫. The second one is the concept of half-convex subgraphs. A subgraph ▫$H$▫ is half-convex in ▫$G$▫ if any vertex ▫$x \in G \setminus H$▫ has at most one predecessor and at most one successor
Keywords: mathematics, graph theory, graph bundles, Cartesian graph product, weighted digraphs, half-convexity
Published: 31.03.2017; Views: 418; Downloads: 217
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