Haensch–Kane spinor-genus decomposition conjecture for ternary lattice cosets

Let LL be a quadratic lattice and let νQL\nu\in\mathbb{Q}L. Define the proper spinor-genus theta series by

Θspn+(L+ν):=1K+μspn+(L+ν)o+(K+μ)1K+μspn+(L+ν)ΘK+μo+(K+μ),\Theta_{\operatorname{spn}^+(L+\nu)}:=\frac{1}{\sum_{K+\mu\in\operatorname{spn}^+(L+\nu)}o^+(K+\mu)^{-1}}\sum_{K+\mu\in\operatorname{spn}^+(L+\nu)}\frac{\Theta_{K+\mu}}{o^+(K+\mu)},

where the sum is over representatives of the proper classes in the proper spinor genus of L+νL+\nu, and o+(K+μ)o^+(K+\mu) is the number of proper automorphs of the lattice coset. Haensch–Kane's spinor-genus decomposition conjecture. For every quadratic lattice LL and νQL\nu\in\mathbb{Q}L,

Θspn+(L+ν)=EL+ν+Uspn+(L+ν),\Theta_{\operatorname{spn}^+(L+\nu)}=E_{L+\nu}+\mathcal{U}_{\operatorname{spn}^+(L+\nu)},

where Uspn+(L+ν)\mathcal{U}_{\operatorname{spn}^+(L+\nu)} is a linear combination of unary theta functions. This extends Schulze-Pillot's corresponding decomposition for lattices to lattice cosets and is motivated by applications to representations of sufficiently large integers. The supplied text does not establish whether the conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Ben Kane and Daejun Kim, “Theta series of ternary quadratic lattice cosets”, arXiv:2211.03987 (2024).

Additional references

3 papers in this index state this conjecture (2016–2022). The statement above is taken from the most recent of them; the others are arXiv:1710.06023, arXiv:1607.06573.

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