On \(f\)-colorings of the Corona Product of Cycles with Some other Graphs

Adiwijaya 1, A.N.M. Salman1, D. Suprijanto1, E.T. Baskoro1
1Combinatorial Mathematics Research Group Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung (ITB) Jl. Ganesa 10 Bandung 40132

Abstract

Let \( G = (V(G), E(G)) \) be a simple graph and let \( f \) be a function from \( V(G) \) to a subset of positive integers. An \( f \)-\({coloring}\) of \( G \) is a generalized edge-coloring such that every vertex \( v \in V(G) \) has at most \( f(v) \) edges colored with the same color. The minimum number of colors needed to define an \( f \)-coloring of \( G \) is called the \( f \)-\({chromatic\; index}\) of \( G \), and denoted by \( \chi_f'(G) \). The \( f \)-chromatic index of \( G \) is equal to \( \Delta_f(G) \) or \( \Delta_f(G) + 1 \), where \( \Delta_f(G) = \max \left\{ \frac{d(v)}{f(v)} \mid v \in V(G) \right\} \). \( G \) is called in the \({class-1}\), denoted by \( C_f1 \), if \( \chi_f'(G) = \Delta_f(G) \); otherwise \( G \) is called in the \({class-2}\), denoted by \( C_f2 \). In this paper, we show that the corona product of a cycle with either the complement of a complete graph, or a path, or a cycle is in \( C_f1 \).

Keywords: corona product, edge coloring, f-coloring, f-chromatic index