The degeneracy and Alon-Tarsi number under $F$-sum operations

TL;DR

This paper characterizes graphs with Alon-Tarsi number 2 and explores how the Alon-Tarsi number behaves under $F$-sum operations, relating it to graph degeneracy.

Contribution

It provides a characterization of graphs with Alon-Tarsi number 2 and analyzes the Alon-Tarsi number in the context of $F$-sum operations based on degeneracy.

Findings

Characterization of graphs with AT(G)=2

Analysis of Alon-Tarsi number under $F$-sum operations

Relationship between Alon-Tarsi number and graph degeneracy

Abstract

The Alon-Tarsi number of a graph $ G $ is the smallest $ k $ such that there exists an orientation $ D $ of $ G $ with maximum outdegree $ k - 1 $ satisfying that the number of even Eulerian subgraphs is different from the number of odd Eulerian subgraphs. The degeneracy of a graph $ G $ is the maximum value of the minimum degree over all subgraphs of $ G $. In this paper, we obtain a characterization of graphs with $AT(G)=2$ for any graph $G$, and study the Alon-Tarsi number of $F$-sum in terms of degeneracy.