LRS asymptotic formula for rational points on multiple conics

Let XX be a smooth, projective, geometrically integral, weak Fano variety over Q\mathbb{Q}. Let UXU \subseteq X be an open subset and let BBrU\mathscr{B} \subseteq \operatorname{Br} U be a finite subset. Assume that BrX=Br1X\operatorname{Br} X = \operatorname{Br}_1 X, that U(Q)BU(\mathbb{Q})_{\mathscr{B}} \neq \varnothing, and that either rk(PicX)=1\operatorname{rk}(\operatorname{Pic} X) = 1 or Q[U]×=Q×\mathbb{Q}[U]^\times = \mathbb{Q}^\times. LRS conjecture. There exists a thin subset ΩX(Q)\Omega \subset X(\mathbb{Q}) such that

#{xU(Q)B:H(x)B,xΩ}cLRSB(logB)rk(PicX)Δ(B)1,\#\{ x \in U(\mathbb{Q})_{\mathscr{B}}: H(x) \leq B, x \notin \Omega \} \sim c_{\textup{LRS}} B(\log B)^{\operatorname{rk}(\operatorname{Pic} X) - \Delta(\mathscr{B}) - 1},

where

Δ(B)=DX(1)(1D(B)1),\Delta(\mathscr{B}) = \sum_{D \in X^{(1)}} \left(1 - \lvert\partial_D(\langle\mathscr{B}\rangle)\rvert^{-1}\right), cLRS=θ(X)BrSub(X,B)/BrQτB(X(AQ)BBrSub(X,B))Γ(X,B)DX(1)η(D)1D(B)1,c_{\textup{LRS}} = \frac{\theta(X) \cdot \lvert\operatorname{Br}_{\mathrm{Sub}}(X,\mathscr{B})/\operatorname{Br} \mathbb{Q}\rvert \cdot \tau_{\mathscr{B}}\left(X(\mathbb{A}_{\mathbb{Q}})_{\mathscr{B}}^{\operatorname{Br}_{\mathrm{Sub}}(X,\mathscr{B})}\right)}{\Gamma(X,\mathscr{B})} \cdot \prod_{D \in X^{(1)}} \eta(D)^{1-\lvert\partial_D(\langle\mathscr{B}\rangle)\rvert^{-1}},

and

Γ(X,B)={DX(1)Γ(D(B)1)if rk(PicX)=1,Γ(rk(PicX)Δ(B))if Q[U]×=Q×.\Gamma(X,\mathscr{B}) = \begin{cases} \displaystyle \prod_{D \in X^{(1)}}\Gamma(\lvert\partial_D(\langle\mathscr{B}\rangle)\rvert^{-1}) & \text{if } \operatorname{rk}(\operatorname{Pic} X) = 1, \\ \displaystyle \Gamma\left(\operatorname{rk}(\operatorname{Pic} X) - \Delta(\mathscr{B})\right) & \text{if } \mathbb{Q}[U]^\times = \mathbb{Q}^\times. \end{cases}

This is an expected Manin-type asymptotic for rational points satisfying the Brauer conditions on weak Fano varieties. The supplied text does not establish the assertion or provide evidence resolving its status.

Sources & referencesView supporting material

Primary source

Stephanie Chan, Peter Koymans and Nick Rome, “Serre's problem for multiple conics”, arXiv:2504.21792 (2025).

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