Conjecture relating Nash adjacency to the thresholds kEk_E and kFk_F

About 11 years old · traced to

Let EE and FF be prime divisors with contact order

Cont⁡(E,F)=i,\operatorname{Cont}(E,F)=i,

where the points pi+1Ep^E_{i+1} and pi+1Fp^F_{i+1} are both free. Define

kF:=max⁡{m:⋃F′≡iFN‾F′⊊Cont⁡m(Epi)‾},k_F:=\max\left\{m:\bigcup_{F'\equiv_i F}\overline{N}_{F'}\subsetneq\overline{\operatorname{Cont}^{m}(E_{p_i})}\right\},

and

kE:=min⁡{m:Cont⁡m(Epi)‾⊊⋂E′≡≥iEN‾E′}.k_E:=\min\left\{m:\overline{\operatorname{Cont}^{m}(E_{p_i})}\subsetneq\bigcap_{E'\equiv_{\geq i}E}\overline{N}_{E'}\right\}.

Here N‾E\overline{N}_E denotes the Nash set associated with EE, and Cont⁡m(Epi)‾\overline{\operatorname{Cont}^{m}(E_{p_i})} is the corresponding closed maximal divisorial set.

Threshold conjecture. One has

N‾F⊊N‾E⟺kF≥kE.\overline{N}_F\subsetneq\overline{N}_E \quad\Longleftrightarrow\quad k_F\geq k_E.

The conjecture seeks a numerical criterion for Nash adjacency in the case where the next points in the resolutions are free. Computing kEk_E and kFk_F is also left as an open problem, and the parser supplies no evidence that the equivalence has been resolved.

References

Primary source

Javier Fernandez de Bobadilla, Maria Pe Pereira and Patrick Popescu-Pampu, “On the generalized Nash problem for smooth germs and adjacencies of curve singularities”, arXiv:1501.06898 (2017).

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