On some extremal position problems for graphs

TL;DR

This paper explores extremal problems related to the general and monophonic position numbers of graphs, including bounds on graph order and size, and characterizes graphs with specific monophonic position numbers.

Contribution

It introduces new bounds and classifications for graphs based on their extremal position parameters, especially for monophonic position number two.

Findings

Determined the minimal order of graphs with given position numbers.

Established the asymptotic maximum size of graphs with specified position numbers.

Classified extremal graphs with monophonic position number two.

Abstract

The general position number of a graph $G$ is the size of the largest set of vertices $S$ such that no geodesic of $G$ contains more than two elements of $S$. The monophonic position number of a graph is defined similarly, but with `induced path' in place of `geodesic'. In this paper we investigate some extremal problems for these parameters. Firstly we discuss the problem of the smallest possible order of a graph with given general and monophonic position numbers. We then determine the asymptotic order of the largest size of a graph with given general or monophonic position number, classifying the extremal graphs with monophonic position number two. Finally we establish the possible diameters of graphs with given order and monophonic position number.