Twin-pair conjecture for vertex-invariant algebraic co-rank

Let GG be a simple graph, let vV(G)v\in V(G), and let GvG-v denote the graph obtained by deleting vv. Twin-pair conjecture. If

γP(Gv)=γP(G)for all vV(G),\gamma_{\mathcal P}(G-v)=\gamma_{\mathcal P}(G)\quad\text{for all }v\in V(G),

then GG has at least one pair of twin vertices. This is proposed as a stronger variant of the twin-free lower-bound conjecture and remains open.

Sources & referencesView supporting material

Primary source

Carlos A. Alfaro, Hugo Corrales and Carlos E. Valencia, “Critical ideals of signed graphs with twin vertices”, arXiv:1504.06257 (2017).

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