Chordal graph conjecture for square-free powers

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Let GG be a chordal graph, let I(G)I(G) be its edge ideal, let I(G)[k]I(G)^{[k]} denote its kk-th square-free power, let ν(G)\nu(G) be its matching number, and let aim(G,k)\mathrm{aim}(G,k) be its kk-admissible matching number. Chordal graph conjecture. For all 1≤k≤ν(G)1\leq k\leq\nu(G), one has

reg(I(G)[k])=aim(G,k)+k.\mathrm{reg}(I(G)^{[k]})=\mathrm{aim}(G,k)+k.

The equality is known for block graphs and for k=2k=2 when GG is Cohen–Macaulay and chordal; computations also support it for chordal graphs with at most eight vertices. The assertion remains open in general.

References

Primary source

Trung Chau, Kanoy Kumar Das, Amit Roy and Kamalesh Saha, “Admissible matchings and the Castelnuovo-Mumford regularity of square-free powers”, arXiv:2504.11941 (2025).

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