Singular Singer–Hopf conjecture for subvarieties

Let XX be an aspherical complex projective manifold and let ZXZ\subseteq X be a closed irreducible subvariety. Let EuZEu_Z be MacPherson's local Euler obstruction function, let χ(Z,EuZ)\chi(Z,Eu_Z) be the Euler–Mather characteristic, let χIH(Z)\chi^{IH}(Z) be the intersection cohomology Euler characteristic, and let icZic_Z be the constructible function obtained from the stalkwise Euler characteristic of the intersection-cohomology complex ICZIC_Z. Let νZ\nu_Z be Behrend's constructible function and set χvir(Z):=χ(Z,νZ)\chi_{vir}(Z):=\chi(Z,\nu_Z). Singular Singer–Hopf conjecture. The following inequalities hold:

(1)dimCZχ(Z,EuZ)0,(-1)^{\dim_\mathbb{C}Z}\cdot\chi(Z,Eu_Z)\geq 0, (1)dimCZχIH(Z)=χ(Z,icZ)0,(-1)^{\dim_\mathbb{C}Z}\cdot\chi^{IH}(Z)=\chi(Z,ic_Z)\geq 0, χvir(Z)0.\chi_{vir}(Z)\geq 0.

When Z=XZ=X, these statements reduce to the complex projective Singer–Hopf conjecture, and when ZZ is smooth they reduce to the corresponding signed Euler-characteristic inequality. The paper proposes these singular variants; their general validity remains open.

Sources & referencesView supporting material

Primary source

Laurentiu Maxim, “On singular variants of the Singer-Hopf Conjecture”, arXiv:2203.10660 (2022).

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