Conjecture on the quadratic conductor formula for quasi-homogeneous hypersurface singularities

From papers

Let O{\mathcal O} be a discrete valuation ring with residue field kk of characteristic different from two, quotient field KK and parameter tt. Let f:XSpecOf:{\mathcal X}\to\operatorname{Spec}{\mathcal O} be a flat and proper morphism with X{\mathcal X} smooth over kk and with generic fiber XKX_K smooth over KK. Suppose that the special fiber X0X_0 has only finitely many singular points p1,,psp_1,\ldots,p_s. Suppose in addition that each (X0,pi)(X_0,p_i) is, over the algebraic closure k(pi)\overline{k(p_i)}, a quasi-homogeneous hypersurface singularity of degree eie_i, with weights a(i)a_*^{(i)}, and with lcm(a(i))=1\operatorname{lcm}(a_*^{(i)})=1. Let a(i)=jaj(i)a^{(i)}=\prod_j a_j^{(i)}. Finally, suppose that eie_i, a(i)a^{(i)}, and [k(pi):k][k(p_i):k] are prime to chark\operatorname{char} k if this is positive. Define

Δt(X/O):=spt(χc(XK/K))χc(X0/k)GW(k).\Delta_t({\mathcal X}/{\mathcal O}):={\operatorname{sp}}_t(\chi_c(X_K/K))-\chi_c(X_0/k)\in {\operatorname{GW}}(k).

Conjecture on the quadratic conductor formula. Then

Δt(X/O)=i=1sTrk(pi)/k[eia(i)1+(ei)dimOXepi(ΩX/k,dt)].\Delta_t({\mathcal X}/{\mathcal O})=\sum_{i=1}^s {\operatorname{Tr}}_{k(p_i)/k}[\langle e_i\cdot a^{(i)}\rangle-\langle1\rangle+(-\langle e_i\rangle)^{{\operatorname{dim}}_{\mathcal O}{\mathcal X}}e_{p_i}(\Omega_{{\mathcal X}/k},dt)].

The formula is a quadratic refinement of the conductor formula for a degeneration with isolated quasi-homogeneous hypersurface singularities. The source notes that, in characteristic zero, it has been verified when each singularity can be resolved by a single weighted blow-up with smooth exceptional divisor; the general statement remains conjectural.

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Sources & referencesView supporting material

Primary source

Marc Levine, Simon Pepin Lehalleur and Vasudevan Srinivas, “Euler characteristics of homogeneous and weighted-homogeneous hypersurfaces”, arXiv:2101.00482 (2022).

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