منابع مشابه
Tight products and graph expansion
In this paper we study a new product of graphs called tight product. A graph H is said to be a tight product of two (undirected multi) graphs G1 and G2, if V (H) = V (G1) × V (G2) and both projection maps V (H) → V (G1) and V (H) → V (G2) are covering maps. It is not a priori clear when two given graphs have a tight product (in fact, it is NP -hard to decide). We investigate the conditions unde...
متن کاملTight products and Expansion
In this paper we study a new product of graphs called tight product. A graph H is said to be a tight product of two (undirected multi) graphs G1 and G2, if V (H) = V (G1) × V (G2) and both projection maps V (H) → V (G1) and V (H) → V (G2) are covering maps. It is not a priori clear when two given graphs have a tight product (in fact, it is NP -hard to decide). We investigate the conditions unde...
متن کاملGraph Products Revisited: Tight Approximation Hardness of Induced Matching, Poset Dimension and More
Graph product is a fundamental tool with rich applications in both graph theory and theoretical computer science. It is usually studied in the form f(G∗H) where G and H are graphs, ∗ is a graph product and f is a graph property. For example, if f is the independence number and ∗ is the disjunctive product, then the product is known to be multiplicative: f(G∗H) = f(G)f(H). In this paper, we stud...
متن کاملOn the Zagreb and Eccentricity Coindices of Graph Products
The second Zagreb coindex is a well-known graph invariant defined as the total degree product of all non-adjacent vertex pairs in a graph. The second Zagreb eccentricity coindex is defined analogously to the second Zagreb coindex by replacing the vertex degrees with the vertex eccentricities. In this paper, we present exact expressions or sharp lower bounds for the second Zagreb eccentricity co...
متن کاملTight and Simple Web Graph Compression
Analysing Web graphs has applications in determining page ranks, fighting Web spam, detecting communities and mirror sites, and more. This study is however hampered by the necessity of storing a major part of huge graphs in the external memory, which prevents efficient random access to edge (hyperlink) lists. A number of algorithm involving compression techniques have thus been presented, to re...
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ژورنال
عنوان ژورنال: Journal of Graph Theory
سال: 2011
ISSN: 0364-9024
DOI: 10.1002/jgt.20593