Existence of compact sets with a prescribed hierarchy of vanishing ideals

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Let R(K)R(K) denote the uniform algebra of rational functions with poles off a compact set KCK\subset\mathbb{C}. For xKx\in K, write MxM_x for the maximal ideal of functions in R(K)R(K) vanishing at xx, and JxJ_x for the ideal of functions vanishing on a neighborhood of xx in KK. Hierarchy conjecture. For each integer s2s\geq 2, there exists a compact set KCK\subset\mathbb{C} such that

JxMxs\overline{J_x}\supset M_x^s

for every xKx\in K, but for some yKy\in K,

Jx⊅Mys1.\overline{J_x}\not\supset M_y^{s-1}.

Consequently, for every xKx\in K one has

Jx=Mxs=Mxs+1=Mxs+2=,\overline{J_x}=\overline{M_x^s}=\overline{M_x^{s+1}}=\overline{M_x^{s+2}}=\cdots,

and at the exceptional point yy,

MyMy2Mys=Jy.M_y\supsetneq\overline{M_y^2}\supsetneq\cdots\supsetneq\overline{M_y^s}=\overline{J_y}.

The conjecture would produce rational function algebras in which the powers of a maximal ideal have a strict closure hierarchy, separating the condition involving JxMxs\overline{J_x}\supset M_x^s from the corresponding condition involving squares of maximal ideals. The source notes that the converse implication is expected to fail and that an example for the opposite implication is planned for future work.

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Sources & referencesView supporting material

Primary source

Alexander J. Izzo, “A sharper Swiss cheese”, arXiv:2211.14684 (2025).

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