Balanced-chromatic number and Hadwiger-like conjectures
This work addresses the extension of Hadwiger’s conjecture to signed graphs. It introduces the *balanced chromatic number*—the minimum number of vertex subsets required such that no subset induces a negative cycle—as the central combinatorial tool. By establishing a quantitative relationship between the balanced chromatic number and the existence of a ( ilde{K}_t) subdivision, the authors prove an upper bound of (O(t^2)), specifically (frac{79}{2}t^2). They formulate and rigorously prove the *signed-graph analogue of Hadwiger’s conjecture*, demonstrating its equivalence to the classical conjecture. Furthermore, they generalize Kawarabayashi’s result on odd minors to the signed-graph setting and uncover a deep connection between the balanced chromatic number and the odd Hadwiger conjecture. The work unifies structural coloring, minor theory, and subdivision analysis for signed graphs, providing a novel framework for Hadwiger-type problems in signed graph theory.