<p>The v-number of a graded ideal is an invariant recently introduced in the context of coding theory, particularly in the study of Reed–Muller-type codes. In this work, we study the localized v-numbers of a binomial edge ideal <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(J_G\)</EquationSource> </InlineEquation> associated to a finite simple graph <i>G</i>. We introduce a new approach to compute these invariants, based on the analysis of transversals in families of subsets arising from dependencies in certain rank-two matroids. This reduces the computation of localized v-numbers to the determination of the radical of an explicit ideal and provides upper bounds for these invariants. Using this method, we explicitly compute the localized v-numbers of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(J_G\)</EquationSource> </InlineEquation> at the associated minimal primes corresponding to minimal cuts of <i>G</i>. Additionally, we determine the v-number of binomial edge ideals for cycle graphs and give an almost complete answer to a conjecture from Dey et al. (Int J Algebra Comput 35(01):119–143, 2024), showing that the v-number of a cycle graph <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(C_n\)</EquationSource> </InlineEquation> is either <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\textstyle \big \lceil \frac{2n}{3} \big \rceil \)</EquationSource> </InlineEquation> or <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\textstyle \big \lceil \frac{2n}{3} \big \rceil - 1\)</EquationSource> </InlineEquation>.</p>

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The V-number of binomial edge ideals: minimal cuts and cycle graphs

  • Emiliano Liwski

摘要

The v-number of a graded ideal is an invariant recently introduced in the context of coding theory, particularly in the study of Reed–Muller-type codes. In this work, we study the localized v-numbers of a binomial edge ideal \(J_G\) associated to a finite simple graph G. We introduce a new approach to compute these invariants, based on the analysis of transversals in families of subsets arising from dependencies in certain rank-two matroids. This reduces the computation of localized v-numbers to the determination of the radical of an explicit ideal and provides upper bounds for these invariants. Using this method, we explicitly compute the localized v-numbers of \(J_G\) at the associated minimal primes corresponding to minimal cuts of G. Additionally, we determine the v-number of binomial edge ideals for cycle graphs and give an almost complete answer to a conjecture from Dey et al. (Int J Algebra Comput 35(01):119–143, 2024), showing that the v-number of a cycle graph \(C_n\) is either \(\textstyle \big \lceil \frac{2n}{3} \big \rceil \) or \(\textstyle \big \lceil \frac{2n}{3} \big \rceil - 1\) .