The positive index of inertia of a signed graph \(\Gamma\), denoted by \(,(\Gamma)\), is the number of positive eigenvalues of the adjacency matrix \(A(\Gamma)\) including multiplicities. In this paper we investigate the minimal positive index of inertia of
signed unicyclic graphs of order \(n\) with fixed girth and characterize the extremal graphs with the minimal positive index. Finally, we characterize the signed unicyclic graphs with the positive indices \(1\) and \(2\).
1970-2025 CP (Manitoba, Canada) unless otherwise stated.