The integrality and zero-block conjecture for quadratic lattice extensions

Let L=MNL=M\oplus N be a quadratic lattice, where MM is spanned by (e1,,end)(e_1,\ldots,e_{n-d}) and NN by (end+1,,en)(e_{n-d+1},\ldots,e_n). Let L=MNL'=M'\oplus N be a lattice containing LL in LoFL\otimes_{\mathfrak{o}}F, with MM' containing MM in MoFM\otimes_{\mathfrak{o}}F. Let qLq_{L'} and qMq_{M'} be the quadratic forms induced from qLq_L. When qMq_{M'} is integral, write Mˉ=M/πM\bar{M}'=M'/\pi M' for its reduction modulo π\pi; when qLq_{L'} is integral, likewise write Lˉ=L/πL\bar{L}'=L'/\pi L'. Integrality and zero-block conjecture. If qMq_{M'} on MM' is integral, then qLq_{L'} on LL' is integral, and hence these conditions are equivalent. In this situation, the dimensions of Lˉ\bar{L}' and Mˉ\bar{M}' modulo their radicals are equal. Equivalently, the number of zero entries in GK(L)\mathrm{GK}(L') equals the number of zero entries in GK(M)\mathrm{GK}(M'). The conjecture would characterize the integrality of qLq_{L'} through the summand MM' and relate the resulting reduced quadratic spaces to the zero entries of their Gross–Keating invariants; the paper proves it when pp is odd or when LL is anisotropic over Z2\mathbb{Z}_2, while the general case remains open.

Sources & referencesView supporting material

Primary source

Sungmun Cho and Takuya Yamauchi, “A reformulation of the Siegel series and intersection numbers”, arXiv:1805.01666 (2020).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.