On b-Eccentricity in Graphs

The distance \( d(u, v) \) between a pair of vertices \( u \) and \( v \) in a connected graph \( G \) is the length of a shortest path joining them. A vertex \( v \) of a connected graph \( G \) is an eccentric vertex of a vertex \( u \) if \( v \) is a vertex at greatest distance from \( u \); while \( v \) is an eccentric vertex of \( G \) if \( v \) is an eccentric vertex of some vertex of \( G \). A vertex \( v \) of \( G \) is a boundary vertex of a vertex \( u \) if \( d(u,w) \leq d(u,v) \) for each neighbour \( w \) of \( v \). A vertex \( v \) is a boundary vertex of \( G \) if \( v \) is a boundary vertex of some vertex of \( G \). It is easy to see that for a vertex \( u \), its eccentric vertices are boundary vertices for \( u \); but not conversely. In this paper, we introduce a new type of eccentricity called b-eccentricity and we study its properties.