Quadrics base locus conjecture for normed-division-algebra dimensions

From papers

For n{2,4,8,16}n\in\{2,4,8,16\}, let Wn,symW_{n,\operatorname{sym}} be a linear subspace of Rsymn×n\mathbb{R}_{\operatorname{sym}}^{n\times n} with

dim(Wn,sym)=12n+1,\dim(W_{n,\operatorname{sym}})=\frac{1}{2}n+1,

and suppose every nonzero element of Wn,symW_{n,\operatorname{sym}} is invertible. Let {A1,,A12n+1}\{A_1,\ldots,A_{\frac{1}{2}n+1}\} be any basis of Wn,symW_{n,\operatorname{sym}}. Quadrics base locus conjecture. The system

{xTA1x=0xTA12n+1x=0\begin{cases} \mathbf{x}^T A_1\mathbf{x}=0\\ \cdots\\ \mathbf{x}^T A_{\frac{1}{2}n+1}\mathbf{x}=0 \end{cases}

has no solution for xRn{0}\mathbf{x}\in\mathbb{R}^n\setminus\{0\}.

This conjecture extends the limitation phenomenon observed computationally for n=2n=2 to the exceptional dimensions n=4,8,16n=4,8,16, which are associated with the real normed division algebras. The supplied passage presents it as motivated by computational experiments and historical connections; no resolution is given.

Progress summary

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Sources & referencesView supporting material

Primary source

Zhitong Su and Weijun Zhang, “A Decomposition Lemma in Convex Integration via Classical Algebraic Geometry”, arXiv:2504.21300 (2026).

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