The WLP characterization conjecture for level Artinian almost complete intersections

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Let R=K[x,y,z]R=K[x,y,z], and let

I=(xα+t,yβ+t,zγ+t,xαyβzγ)I=(x^{\alpha+t},y^{\beta+t},z^{\gamma+t},x^\alpha y^\beta z^\gamma)

be a level Artinian almost complete intersection, where t>0t>0 and 0≤α≤β≤γ0\leq\alpha\leq\beta\leq\gamma. Assume that KK is algebraically closed of characteristic zero. The WLP characterization conjecture. The quotient R/IR/I has the WLP whenever at least one of the following holds: (a) α=0\alpha=0; (b) α+β+γ\alpha+\beta+\gamma is not divisible by 33; (c) γ>2(α+β)\gamma>2(\alpha+\beta); or (d) t<13(α+β+γ)t<\frac{1}{3}(\alpha+\beta+\gamma). If 1≤α≤β≤γ≤2(α+β)1\leq\alpha\leq\beta\leq\gamma\leq2(\alpha+\beta), α+β+γ≡0(mod3)\alpha+\beta+\gamma\equiv0\pmod 3, and t≥13(α+β+γ)t\geq\frac{1}{3}(\alpha+\beta+\gamma), then R/IR/I fails to have the WLP if and only if tt is even and either (i) α\alpha is even, α=β\alpha=\beta, and γ−α≡3(mod6)\gamma-\alpha\equiv3\pmod 6, or (ii) α\alpha is odd and either α=β\alpha=\beta with γ−α≡0(mod6)\gamma-\alpha\equiv0\pmod 6, or β=γ\beta=\gamma with γ−α≡0(mod3)\gamma-\alpha\equiv0\pmod 3. In all these cases, the Hilbert function has twin peaks. The claim gives a proposed complete characterization of the weak Lefschetz property in this family, extending the preceding semistability and congruence criteria; its status is not resolved in the supplied source context.

References

Primary source

Juan C. Migliore, Rosa M. Miro-Roig and Uwe Nagel, “Monomial ideals, almost complete intersections and the Weak Lefschetz Property”, arXiv:0811.1023 (2009).

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